text: import firebase from '@firebase/app';
  import { stringify, jsonEval, contains, assert, base64, stringToByteArray, Sha1, forEach, isNodeSdk, stringLength, errorPrefix, validateArgCount, validateCallback, Deferred, assertionError, safeGet, clone, map, getCount, getAnyKey, every, validateContextObject, isEmpty, getValues, findValue, findKey, deepCopy, isMobileCordova, base64Encode, CONSTANTS, isAdmin, isValidFormat, isReactNative, querystring } from '@firebase/util';
  import { Logger, LogLevel } from '@firebase/logger';
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Wraps a DOM Storage object and:
   * - automatically encode objects as JSON strings before storing them to allow us to store arbitrary types.
   * - prefixes names with "firebase:" to avoid collisions with app data.
   *
   * We automatically (see storage.js) create two such wrappers, one for sessionStorage,
   * and one for localStorage.
   *
   * @constructor
   */
  class DOMStorageWrapper {
      /**
       * @param {Storage} domStorage_ The underlying storage object (e.g. localStorage or sessionStorage)
       */
      constructor(domStorage_) {
          this.domStorage_ = domStorage_;
          // Use a prefix to avoid collisions with other stuff saved by the app.
          this.prefix_ = 'firebase:';
      }
      /**
       * @param {string} key The key to save the value under
       * @param {?Object} value The value being stored, or null to remove the key.
       */
      set(key, value) {
          if (value == null) {
              this.domStorage_.removeItem(this.prefixedName_(key));
          }
          else {
              this.domStorage_.setItem(this.prefixedName_(key), stringify(value));
          }
      }
      /**
       * @param {string} key
       * @return {*} The value that was stored under this key, or null
       */
      get(key) {
          const storedVal = this.domStorage_.getItem(this.prefixedName_(key));
          if (storedVal == null) {
              return null;
          }
          else {
              return jsonEval(storedVal);
          }
      }
      /**
       * @param {string} key
       */
      remove(key) {
          this.domStorage_.removeItem(this.prefixedName_(key));
      }
      /**
       * @param {string} name
       * @return {string}
       */
      prefixedName_(name) {
          return this.prefix_ + name;
      }
      toString() {
          return this.domStorage_.toString();
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * An in-memory storage implementation that matches the API of DOMStorageWrapper
   * (TODO: create interface for both to implement).
   *
   * @constructor
   */
  class MemoryStorage {
      constructor() {
          this.cache_ = {};
          this.isInMemoryStorage = true;
      }
      set(key, value) {
          if (value == null) {
              delete this.cache_[key];
          }
          else {
              this.cache_[key] = value;
          }
      }
      get(key) {
          if (contains(this.cache_, key)) {
              return this.cache_[key];
          }
          return null;
      }
      remove(key) {
          delete this.cache_[key];
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Helper to create a DOMStorageWrapper or else fall back to MemoryStorage.
   * TODO: Once MemoryStorage and DOMStorageWrapper have a shared interface this method annotation should change
   * to reflect this type
   *
   * @param {string} domStorageName Name of the underlying storage object
   *   (e.g. 'localStorage' or 'sessionStorage').
   * @return {?} Turning off type information until a common interface is defined.
   */
  const createStoragefor = function (domStorageName) {
      try {
          // NOTE: just accessing "localStorage" or "window['localStorage']" may throw a security exception,
          // so it must be inside the try/catch.
          if (typeof window !== 'undefined' &&
              typeof window[domStorageName] !== 'undefined') {
              // Need to test cache. Just because it's here doesn't mean it works
              const domStorage = window[domStorageName];
              domStorage.setItem('firebase:sentinel', 'cache');
              domStorage.removeItem('firebase:sentinel');
              return new DOMStorageWrapper(domStorage);
          }
      }
      catch (e) { }
      // Failed to create wrapper.  Just return in-memory storage.
      // TODO: log?
      return new MemoryStorage();
  };
  /** A storage object that lasts across sessions */
  const PersistentStorage = createStoragefor('localStorage');
  /** A storage object that only lasts one session */
  const SessionStorage = createStoragefor('sessionStorage');
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const logClient = new Logger('@firebase/database');
  /**
   * Returns a locally-unique ID (generated by just incrementing up from 0 each time its called).
   * @type {function(): number} Generated ID.
   */
  const LUIDGenerator = (function () {
      let id = 1;
      return function () {
          return id++;
      };
  })();
  /**
   * Sha1 hash of the input string
   * @param {!string} str The string to hash
   * @return {!string} The resulting hash
   */
  const sha1 = function (str) {
      const utf8Bytes = stringToByteArray(str);
      const sha1 = new Sha1();
      sha1.update(utf8Bytes);
      const sha1Bytes = sha1.digest();
      return base64.encodeByteArray(sha1Bytes);
  };
  /**
   * @param {...*} var_args
   * @return {string}
   * @private
   */
  const buildLogMessage_ = function (...var_args) {
      let message = '';
      for (let i = 0; i < var_args.length; i++) {
          if (Array.isArray(var_args[i]) ||
              (var_args[i] &&
                  typeof var_args[i] === 'object' &&
                  typeof var_args[i].length === 'number')) {
              message += buildLogMessage_.apply(null, var_args[i]);
          }
          else if (typeof var_args[i] === 'object') {
              message += stringify(var_args[i]);
          }
          else {
              message += var_args[i];
          }
          message += ' ';
      }
      return message;
  };
  /**
   * Use this for all debug messages in Firebase.
   * @type {?function(string)}
   */
  let logger = null;
  /**
   * Flag to check for log availability on first log message
   * @type {boolean}
   * @private
   */
  let firstLog_ = true;
  /**
   * The implementation of Firebase.enableLogging (defined here to break dependencies)
   * @param {boolean|?function(string)} logger_ A flag to turn on logging, or a custom logger
   * @param {boolean=} persistent Whether or not to persist logging settings across refreshes
   */
  const enableLogging = function (logger_, persistent) {
      assert(!persistent || (logger_ === true || logger_ === false), "Can't turn on custom loggers persistently.");
      if (logger_ === true) {
          logClient.logLevel = LogLevel.VERBOSE;
          logger = logClient.log.bind(logClient);
          if (persistent)
              SessionStorage.set('logging_enabled', true);
      }
      else if (typeof logger_ === 'function') {
          logger = logger_;
      }
      else {
          logger = null;
          SessionStorage.remove('logging_enabled');
      }
  };
  /**
   *
   * @param {...(string|Arguments)} var_args
   */
  const log = function (...var_args) {
      if (firstLog_ === true) {
          firstLog_ = false;
          if (logger === null && SessionStorage.get('logging_enabled') === true)
              enableLogging(true);
      }
      if (logger) {
          const message = buildLogMessage_.apply(null, var_args);
          logger(message);
      }
  };
  /**
   * @param {!string} prefix
   * @return {function(...[*])}
   */
  const logWrapper = function (prefix) {
      return function (...var_args) {
          log(prefix, ...var_args);
      };
  };
  /**
   * @param {...string} var_args
   */
  const error = function (...var_args) {
      const message = 'FIREBASE INTERNAL ERROR: ' + buildLogMessage_(...var_args);
      logClient.error(message);
  };
  /**
   * @param {...string} var_args
   */
  const fatal = function (...var_args) {
      const message = `FIREBASE FATAL ERROR: ${buildLogMessage_(...var_args)}`;
      logClient.error(message);
      throw new Error(message);
  };
  /**
   * @param {...*} var_args
   */
  const warn = function (...var_args) {
      const message = 'FIREBASE WARNING: ' + buildLogMessage_(...var_args);
      logClient.warn(message);
  };
  /**
   * Logs a warning if the containing page uses https. Called when a call to new Firebase
   * does not use https.
   */
  const warnIfPageIsSecure = function () {
      // Be very careful accessing browser globals. Who knows what may or may not exist.
      if (typeof window !== 'undefined' &&
          window.location &&
          window.location.protocol &&
          window.location.protocol.indexOf('https:') !== -1) {
          warn('Insecure Firebase access from a secure page. ' +
              'Please use https in calls to new Firebase().');
      }
  };
  /**
   * Returns true if data is NaN, or +/- Infinity.
   * @param {*} data
   * @return {boolean}
   */
  const isInvalidJSONNumber = function (data) {
      return (typeof data === 'number' &&
          (data != data || // NaN
              data == Number.POSITIVE_INFINITY ||
              data == Number.NEGATIVE_INFINITY));
  };
  /**
   * @param {function()} fn
   */
  const executeWhenDOMReady = function (fn) {
      if (isNodeSdk() || document.readyState === 'complete') {
          fn();
      }
      else {
          // Modeled after jQuery. Try DOMContentLoaded and onreadystatechange (which
          // fire before onload), but fall back to onload.
          let called = false;
          let wrappedFn = function () {
              if (!document.body) {
                  setTimeout(wrappedFn, Math.floor(10));
                  return;
              }
              if (!called) {
                  called = true;
                  fn();
              }
          };
          if (document.addEventListener) {
              document.addEventListener('DOMContentLoaded', wrappedFn, false);
              // fallback to onload.
              window.addEventListener('load', wrappedFn, false);
          }
          else if (document.attachEvent) {
              // IE.
              document.attachEvent('onreadystatechange', function () {
                  if (document.readyState === 'complete')
                      wrappedFn();
              });
              // fallback to onload.
              window.attachEvent('onload', wrappedFn);
              // jQuery has an extra hack for IE that we could employ (based on
              // http://javascript.nwbox.com/IEContentLoaded/) But it looks really old.
              // I'm hoping we don't need it.
          }
      }
  };
  /**
   * Minimum key name. Invalid for actual data, used as a marker to sort before any valid names
   * @type {!string}
   */
  const MIN_NAME = '[MIN_NAME]';
  /**
   * Maximum key name. Invalid for actual data, used as a marker to sort above any valid names
   * @type {!string}
   */
  const MAX_NAME = '[MAX_NAME]';
  /**
   * Compares valid Firebase key names, plus min and max name
   * @param {!string} a
   * @param {!string} b
   * @return {!number}
   */
  const nameCompare = function (a, b) {
      if (a === b) {
          return 0;
      }
      else if (a === MIN_NAME || b === MAX_NAME) {
          return -1;
      }
      else if (b === MIN_NAME || a === MAX_NAME) {
          return 1;
      }
      else {
          const aAsInt = tryParseInt(a), bAsInt = tryParseInt(b);
          if (aAsInt !== null) {
              if (bAsInt !== null) {
                  return aAsInt - bAsInt == 0 ? a.length - b.length : aAsInt - bAsInt;
              }
              else {
                  return -1;
              }
          }
          else if (bAsInt !== null) {
              return 1;
          }
          else {
              return a < b ? -1 : 1;
          }
      }
  };
  /**
   * @param {!string} a
   * @param {!string} b
   * @return {!number} comparison result.
   */
  const stringCompare = function (a, b) {
      if (a === b) {
          return 0;
      }
      else if (a < b) {
          return -1;
      }
      else {
          return 1;
      }
  };
  /**
   * @param {string} key
   * @param {Object} obj
   * @return {*}
   */
  const requireKey = function (key, obj) {
      if (obj && key in obj) {
          return obj[key];
      }
      else {
          throw new Error('Missing required key (' + key + ') in object: ' + stringify(obj));
      }
  };
  /**
   * @param {*} obj
   * @return {string}
   */
  const ObjectToUniqueKey = function (obj) {
      if (typeof obj !== 'object' || obj === null)
          return stringify(obj);
      const keys = [];
      for (let k in obj) {
          keys.push(k);
      }
      // Export as json, but with the keys sorted.
      keys.sort();
      let key = '{';
      for (let i = 0; i < keys.length; i++) {
          if (i !== 0)
              key += ',';
          key += stringify(keys[i]);
          key += ':';
          key += ObjectToUniqueKey(obj[keys[i]]);
      }
      key += '}';
      return key;
  };
  /**
   * Splits a string into a number of smaller segments of maximum size
   * @param {!string} str The string
   * @param {!number} segsize The maximum number of chars in the string.
   * @return {Array.<string>} The string, split into appropriately-sized chunks
   */
  const splitStringBySize = function (str, segsize) {
      const len = str.length;
      if (len <= segsize) {
          return [str];
      }
      const dataSegs = [];
      for (let c = 0; c < len; c += segsize) {
          if (c + segsize > len) {
              dataSegs.push(str.substring(c, len));
          }
          else {
              dataSegs.push(str.substring(c, c + segsize));
          }
      }
      return dataSegs;
  };
  /**
   * Apply a function to each (key, value) pair in an object or
   * apply a function to each (index, value) pair in an array
   * @param {!(Object|Array)} obj The object or array to iterate over
   * @param {function(?, ?)} fn The function to apply
   */
  const each = function (obj, fn) {
      if (Array.isArray(obj)) {
          for (let i = 0; i < obj.length; ++i) {
              fn(i, obj[i]);
          }
      }
      else {
          /**
           * in the conversion of code we removed the goog.object.forEach
           * function which did a value,key callback. We standardized on
           * a single impl that does a key, value callback. So we invert
           * to not have to touch the `each` code points
           */
          forEach(obj, (key, val) => fn(val, key));
      }
  };
  /**
   * Borrowed from http://hg.secondlife.com/llsd/src/tip/js/typedarray.js (MIT License)
   * I made one modification at the end and removed the NaN / Infinity
   * handling (since it seemed broken [caused an overflow] and we don't need it).  See MJL comments.
   * @param {!number} v A double
   * @return {string}
   */
  const doubleToIEEE754String = function (v) {
      assert(!isInvalidJSONNumber(v), 'Invalid JSON number'); // MJL
      const ebits = 11, fbits = 52;
      let bias = (1 << (ebits - 1)) - 1, s, e, f, ln, i, bits, str;
      // Compute sign, exponent, fraction
      // Skip NaN / Infinity handling --MJL.
      if (v === 0) {
          e = 0;
          f = 0;
          s = 1 / v === -Infinity ? 1 : 0;
      }
      else {
          s = v < 0;
          v = Math.abs(v);
          if (v >= Math.pow(2, 1 - bias)) {
              // Normalized
              ln = Math.min(Math.floor(Math.log(v) / Math.LN2), bias);
              e = ln + bias;
              f = Math.round(v * Math.pow(2, fbits - ln) - Math.pow(2, fbits));
          }
          else {
              // Denormalized
              e = 0;
              f = Math.round(v / Math.pow(2, 1 - bias - fbits));
          }
      }
      // Pack sign, exponent, fraction
      bits = [];
      for (i = fbits; i; i -= 1) {
          bits.push(f % 2 ? 1 : 0);
          f = Math.floor(f / 2);
      }
      for (i = ebits; i; i -= 1) {
          bits.push(e % 2 ? 1 : 0);
          e = Math.floor(e / 2);
      }
      bits.push(s ? 1 : 0);
      bits.reverse();
      str = bits.join('');
      // Return the data as a hex string. --MJL
      let hexByteString = '';
      for (i = 0; i < 64; i += 8) {
          let hexByte = parseInt(str.substr(i, 8), 2).toString(16);
          if (hexByte.length === 1)
              hexByte = '0' + hexByte;
          hexByteString = hexByteString + hexByte;
      }
      return hexByteString.toLowerCase();
  };
  /**
   * Used to detect if we're in a Chrome content script (which executes in an
   * isolated environment where long-polling doesn't work).
   * @return {boolean}
   */
  const isChromeExtensionContentScript = function () {
      return !!(typeof window === 'object' &&
          window['chrome'] &&
          window['chrome']['extension'] &&
          !/^chrome/.test(window.location.href));
  };
  /**
   * Used to detect if we're in a Windows 8 Store app.
   * @return {boolean}
   */
  const isWindowsStoreApp = function () {
      // Check for the presence of a couple WinRT globals
      return typeof Windows === 'object' && typeof Windows.UI === 'object';
  };
  /**
   * Converts a server error code to a Javascript Error
   * @param {!string} code
   * @param {!Query} query
   * @return {Error}
   */
  const errorForServerCode = function (code, query) {
      let reason = 'Unknown Error';
      if (code === 'too_big') {
          reason =
              'The data requested exceeds the maximum size ' +
                  'that can be accessed with a single request.';
      }
      else if (code == 'permission_denied') {
          reason = "Client doesn't have permission to access the desired data.";
      }
      else if (code == 'unavailable') {
          reason = 'The service is unavailable';
      }
      const error = new Error(code + ' at ' + query.path.toString() + ': ' + reason);
      error.code = code.toUpperCase();
      return error;
  };
  /**
   * Used to test for integer-looking strings
   * @type {RegExp}
   * @private
   */
  const INTEGER_REGEXP_ = new RegExp('^-?\\d{1,10}$');
  /**
   * If the string contains a 32-bit integer, return it.  Else return null.
   * @param {!string} str
   * @return {?number}
   */
  const tryParseInt = function (str) {
      if (INTEGER_REGEXP_.test(str)) {
          const intVal = Number(str);
          if (intVal >= -2147483648 && intVal <= 2147483647) {
              return intVal;
          }
      }
      return null;
  };
  /**
   * Helper to run some code but catch any exceptions and re-throw them later.
   * Useful for preventing user callbacks from breaking internal code.
   *
   * Re-throwing the exception from a setTimeout is a little evil, but it's very
   * convenient (we don't have to try to figure out when is a safe point to
   * re-throw it), and the behavior seems reasonable:
   *
   * * If you aren't pausing on exceptions, you get an error in the console with
   *   the correct stack trace.
   * * If you're pausing on all exceptions, the debugger will pause on your
   *   exception and then again when we rethrow it.
   * * If you're only pausing on uncaught exceptions, the debugger will only pause
   *   on us re-throwing it.
   *
   * @param {!function()} fn The code to guard.
   */
  const exceptionGuard = function (fn) {
      try {
          fn();
      }
      catch (e) {
          // Re-throw exception when it's safe.
          setTimeout(function () {
              // It used to be that "throw e" would result in a good console error with
              // relevant context, but as of Chrome 39, you just get the firebase.js
              // file/line number where we re-throw it, which is useless. So we log
              // e.stack explicitly.
              const stack = e.stack || '';
              warn('Exception was thrown by user callback.', stack);
              throw e;
          }, Math.floor(0));
      }
  };
  /**
   * @return {boolean} true if we think we're currently being crawled.
   */
  const beingCrawled = function () {
      const userAgent = (typeof window === 'object' &&
          window['navigator'] &&
          window['navigator']['userAgent']) ||
          '';
      // For now we whitelist the most popular crawlers.  We should refine this to be the set of crawlers we
      // believe to support JavaScript/AJAX rendering.
      // NOTE: Google Webmaster Tools doesn't really belong, but their "This is how a visitor to your website
      // would have seen the page" is flaky if we don't treat it as a crawler.
      return (userAgent.search(/googlebot|google webmaster tools|bingbot|yahoo! slurp|baiduspider|yandexbot|duckduckbot/i) >= 0);
  };
  /**
   * Same as setTimeout() except on Node.JS it will /not/ prevent the process from exiting.
   *
   * It is removed with clearTimeout() as normal.
   *
   * @param {Function} fn Function to run.
   * @param {number} time Milliseconds to wait before running.
   * @return {number|Object} The setTimeout() return value.
   */
  const setTimeoutNonBlocking = function (fn, time) {
      const timeout = setTimeout(fn, time);
      if (typeof timeout === 'object' && timeout['unref']) {
          timeout['unref']();
      }
      return timeout;
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * An immutable object representing a parsed path.  It's immutable so that you
   * can pass them around to other functions without worrying about them changing
   * it.
   */
  class Path {
      /**
       * Singleton to represent an empty path
       *
       * @const
       */
      static get Empty() {
          return new Path('');
      }
      /**
       * @param {string|Array.<string>} pathOrString Path string to parse,
       *      or another path, or the raw tokens array
       * @param {number=} pieceNum
       */
      constructor(pathOrString, pieceNum) {
          if (pieceNum === void 0) {
              this.pieces_ = pathOrString.split('/');
              // Remove empty pieces.
              let copyTo = 0;
              for (let i = 0; i < this.pieces_.length; i++) {
                  if (this.pieces_[i].length > 0) {
                      this.pieces_[copyTo] = this.pieces_[i];
                      copyTo++;
                  }
              }
              this.pieces_.length = copyTo;
              this.pieceNum_ = 0;
          }
          else {
              this.pieces_ = pathOrString;
              this.pieceNum_ = pieceNum;
          }
      }
      getFront() {
          if (this.pieceNum_ >= this.pieces_.length)
              return null;
          return this.pieces_[this.pieceNum_];
      }
      /**
       * @return {number} The number of segments in this path
       */
      getLength() {
          return this.pieces_.length - this.pieceNum_;
      }
      /**
       * @return {!Path}
       */
      popFront() {
          let pieceNum = this.pieceNum_;
          if (pieceNum < this.pieces_.length) {
              pieceNum++;
          }
          return new Path(this.pieces_, pieceNum);
      }
      /**
       * @return {?string}
       */
      getBack() {
          if (this.pieceNum_ < this.pieces_.length)
              return this.pieces_[this.pieces_.length - 1];
          return null;
      }
      toString() {
          let pathString = '';
          for (let i = this.pieceNum_; i < this.pieces_.length; i++) {
              if (this.pieces_[i] !== '')
                  pathString += '/' + this.pieces_[i];
          }
          return pathString || '/';
      }
      toUrlEncodedString() {
          let pathString = '';
          for (let i = this.pieceNum_; i < this.pieces_.length; i++) {
              if (this.pieces_[i] !== '')
                  pathString += '/' + encodeURIComponent(String(this.pieces_[i]));
          }
          return pathString || '/';
      }
      /**
       * Shallow copy of the parts of the path.
       *
       * @param {number=} begin
       * @return {!Array<string>}
       */
      slice(begin = 0) {
          return this.pieces_.slice(this.pieceNum_ + begin);
      }
      /**
       * @return {?Path}
       */
      parent() {
          if (this.pieceNum_ >= this.pieces_.length)
              return null;
          const pieces = [];
          for (let i = this.pieceNum_; i < this.pieces_.length - 1; i++)
              pieces.push(this.pieces_[i]);
          return new Path(pieces, 0);
      }
      /**
       * @param {string|!Path} childPathObj
       * @return {!Path}
       */
      child(childPathObj) {
          const pieces = [];
          for (let i = this.pieceNum_; i < this.pieces_.length; i++)
              pieces.push(this.pieces_[i]);
          if (childPathObj instanceof Path) {
              for (let i = childPathObj.pieceNum_; i < childPathObj.pieces_.length; i++) {
                  pieces.push(childPathObj.pieces_[i]);
              }
          }
          else {
              const childPieces = childPathObj.split('/');
              for (let i = 0; i < childPieces.length; i++) {
                  if (childPieces[i].length > 0)
                      pieces.push(childPieces[i]);
              }
          }
          return new Path(pieces, 0);
      }
      /**
       * @return {boolean} True if there are no segments in this path
       */
      isEmpty() {
          return this.pieceNum_ >= this.pieces_.length;
      }
      /**
       * @param {!Path} outerPath
       * @param {!Path} innerPath
       * @return {!Path} The path from outerPath to innerPath
       */
      static relativePath(outerPath, innerPath) {
          const outer = outerPath.getFront(), inner = innerPath.getFront();
          if (outer === null) {
              return innerPath;
          }
          else if (outer === inner) {
              return Path.relativePath(outerPath.popFront(), innerPath.popFront());
          }
          else {
              throw new Error('INTERNAL ERROR: innerPath (' +
                  innerPath +
                  ') is not within ' +
                  'outerPath (' +
                  outerPath +
                  ')');
          }
      }
      /**
       * @param {!Path} left
       * @param {!Path} right
       * @return {number} -1, 0, 1 if left is less, equal, or greater than the right.
       */
      static comparePaths(left, right) {
          const leftKeys = left.slice();
          const rightKeys = right.slice();
          for (let i = 0; i < leftKeys.length && i < rightKeys.length; i++) {
              const cmp = nameCompare(leftKeys[i], rightKeys[i]);
              if (cmp !== 0)
                  return cmp;
          }
          if (leftKeys.length === rightKeys.length)
              return 0;
          return leftKeys.length < rightKeys.length ? -1 : 1;
      }
      /**
       *
       * @param {Path} other
       * @return {boolean} true if paths are the same.
       */
      equals(other) {
          if (this.getLength() !== other.getLength()) {
              return false;
          }
          for (let i = this.pieceNum_, j = other.pieceNum_; i <= this.pieces_.length; i++, j++) {
              if (this.pieces_[i] !== other.pieces_[j]) {
                  return false;
              }
          }
          return true;
      }
      /**
       *
       * @param {!Path} other
       * @return {boolean} True if this path is a parent (or the same as) other
       */
      contains(other) {
          let i = this.pieceNum_;
          let j = other.pieceNum_;
          if (this.getLength() > other.getLength()) {
              return false;
          }
          while (i < this.pieces_.length) {
              if (this.pieces_[i] !== other.pieces_[j]) {
                  return false;
              }
              ++i;
              ++j;
          }
          return true;
      }
  } // end Path
  /**
   * Dynamic (mutable) path used to count path lengths.
   *
   * This class is used to efficiently check paths for valid
   * length (in UTF8 bytes) and depth (used in path validation).
   *
   * Throws Error exception if path is ever invalid.
   *
   * The definition of a path always begins with '/'.
   */
  class ValidationPath {
      /**
       * @param {!Path} path Initial Path.
       * @param {string} errorPrefix_ Prefix for any error messages.
       */
      constructor(path, errorPrefix_) {
          this.errorPrefix_ = errorPrefix_;
          /** @type {!Array<string>} */
          this.parts_ = path.slice();
          /** @type {number} Initialize to number of '/' chars needed in path. */
          this.byteLength_ = Math.max(1, this.parts_.length);
          for (let i = 0; i < this.parts_.length; i++) {
              this.byteLength_ += stringLength(this.parts_[i]);
          }
          this.checkValid_();
      }
      /** @const {number} Maximum key depth. */
      static get MAX_PATH_DEPTH() {
          return 32;
      }
      /** @const {number} Maximum number of (UTF8) bytes in a Firebase path. */
      static get MAX_PATH_LENGTH_BYTES() {
          return 768;
      }
      /** @param {string} child */
      push(child) {
          // Count the needed '/'
          if (this.parts_.length > 0) {
              this.byteLength_ += 1;
          }
          this.parts_.push(child);
          this.byteLength_ += stringLength(child);
          this.checkValid_();
      }
      pop() {
          const last = this.parts_.pop();
          this.byteLength_ -= stringLength(last);
          // Un-count the previous '/'
          if (this.parts_.length > 0) {
              this.byteLength_ -= 1;
          }
      }
      checkValid_() {
          if (this.byteLength_ > ValidationPath.MAX_PATH_LENGTH_BYTES) {
              throw new Error(this.errorPrefix_ +
                  'has a key path longer than ' +
                  ValidationPath.MAX_PATH_LENGTH_BYTES +
                  ' bytes (' +
                  this.byteLength_ +
                  ').');
          }
          if (this.parts_.length > ValidationPath.MAX_PATH_DEPTH) {
              throw new Error(this.errorPrefix_ +
                  'path specified exceeds the maximum depth that can be written (' +
                  ValidationPath.MAX_PATH_DEPTH +
                  ') or object contains a cycle ' +
                  this.toErrorString());
          }
      }
      /**
       * String for use in error messages - uses '.' notation for path.
       *
       * @return {string}
       */
      toErrorString() {
          if (this.parts_.length == 0) {
              return '';
          }
          return "in property '" + this.parts_.join('.') + "'";
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const PROTOCOL_VERSION = '5';
  const VERSION_PARAM = 'v';
  const TRANSPORT_SESSION_PARAM = 's';
  const REFERER_PARAM = 'r';
  const FORGE_REF = 'f';
  const FORGE_DOMAIN = 'firebaseio.com';
  const LAST_SESSION_PARAM = 'ls';
  const WEBSOCKET = 'websocket';
  const LONG_POLLING = 'long_polling';
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * A class that holds metadata about a Repo object
   *
   * @constructor
   */
  class RepoInfo {
      /**
       * @param {string} host Hostname portion of the url for the repo
       * @param {boolean} secure Whether or not this repo is accessed over ssl
       * @param {string} namespace The namespace represented by the repo
       * @param {boolean} webSocketOnly Whether to prefer websockets over all other transports (used by Nest).
       * @param {string=} persistenceKey Override the default session persistence storage key
       */
      constructor(host, secure, namespace, webSocketOnly, persistenceKey = '') {
          this.secure = secure;
          this.namespace = namespace;
          this.webSocketOnly = webSocketOnly;
          this.persistenceKey = persistenceKey;
          this.host = host.toLowerCase();
          this.domain = this.host.substr(this.host.indexOf('.') + 1);
          this.internalHost = PersistentStorage.get('host:' + host) || this.host;
      }
      needsQueryParam() {
          return this.host !== this.internalHost || this.isCustomHost();
      }
      isCacheableHost() {
          return this.internalHost.substr(0, 2) === 's-';
      }
      isDemoHost() {
          return this.domain === 'firebaseio-demo.com';
      }
      isCustomHost() {
          return (this.domain !== 'firebaseio.com' && this.domain !== 'firebaseio-demo.com');
      }
      updateHost(newHost) {
          if (newHost !== this.internalHost) {
              this.internalHost = newHost;
              if (this.isCacheableHost()) {
                  PersistentStorage.set('host:' + this.host, this.internalHost);
              }
          }
      }
      /**
       * Returns the websocket URL for this repo
       * @param {string} type of connection
       * @param {Object} params list
       * @return {string} The URL for this repo
       */
      connectionURL(type, params) {
          assert(typeof type === 'string', 'typeof type must == string');
          assert(typeof params === 'object', 'typeof params must == object');
          let connURL;
          if (type === WEBSOCKET) {
              connURL =
                  (this.secure ? 'wss://' : 'ws://') + this.internalHost + '/.ws?';
          }
          else if (type === LONG_POLLING) {
              connURL =
                  (this.secure ? 'https://' : 'http://') + this.internalHost + '/.lp?';
          }
          else {
              throw new Error('Unknown connection type: ' + type);
          }
          if (this.needsQueryParam()) {
              params['ns'] = this.namespace;
          }
          const pairs = [];
          forEach(params, (key, value) => {
              pairs.push(key + '=' + value);
          });
          return connURL + pairs.join('&');
      }
      /** @return {string} */
      toString() {
          let str = this.toURLString();
          if (this.persistenceKey) {
              str += '<' + this.persistenceKey + '>';
          }
          return str;
      }
      /** @return {string} */
      toURLString() {
          return (this.secure ? 'https://' : 'http://') + this.host;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @param {!string} pathString
   * @return {string}
   */
  function decodePath(pathString) {
      let pathStringDecoded = '';
      const pieces = pathString.split('/');
      for (let i = 0; i < pieces.length; i++) {
          if (pieces[i].length > 0) {
              let piece = pieces[i];
              try {
                  piece = decodeURIComponent(piece.replace(/\+/g, ' '));
              }
              catch (e) { }
              pathStringDecoded += '/' + piece;
          }
      }
      return pathStringDecoded;
  }
  /**
   * @param {!string} queryString
   * @return {!{[key:string]:string}} key value hash
   */
  function decodeQuery(queryString) {
      let results = {};
      if (queryString.charAt(0) === '?') {
          queryString = queryString.substring(1);
      }
      for (const segment of queryString.split('&')) {
          if (segment.length === 0) {
              continue;
          }
          const kv = segment.split('=');
          if (kv.length === 2) {
              results[decodeURIComponent(kv[0])] = decodeURIComponent(kv[1]);
          }
          else {
              warn(`Invalid query segment '${segment}' in query '${queryString}'`);
          }
      }
      return results;
  }
  /**
   *
   * @param {!string} dataURL
   * @return {{repoInfo: !RepoInfo, path: !Path}}
   */
  const parseRepoInfo = function (dataURL) {
      const parsedUrl = parseURL(dataURL), namespace = parsedUrl.subdomain;
      if (parsedUrl.domain === 'firebase') {
          fatal(parsedUrl.host +
              ' is no longer supported. ' +
              'Please use <YOUR FIREBASE>.firebaseio.com instead');
      }
      // Catch common error of uninitialized namespace value.
      if ((!namespace || namespace == 'undefined') &&
          parsedUrl.domain !== 'localhost') {
          fatal('Cannot parse Firebase url. Please use https://<YOUR FIREBASE>.firebaseio.com');
      }
      if (!parsedUrl.secure) {
          warnIfPageIsSecure();
      }
      const webSocketOnly = parsedUrl.scheme === 'ws' || parsedUrl.scheme === 'wss';
      return {
          repoInfo: new RepoInfo(parsedUrl.host, parsedUrl.secure, namespace, webSocketOnly),
          path: new Path(parsedUrl.pathString)
      };
  };
  /**
   *
   * @param {!string} dataURL
   * @return {{host: string, port: number, domain: string, subdomain: string, secure: boolean, scheme: string, pathString: string}}
   */
  const parseURL = function (dataURL) {
      // Default to empty strings in the event of a malformed string.
      let host = '', domain = '', subdomain = '', pathString = '';
      // Always default to SSL, unless otherwise specified.
      let secure = true, scheme = 'https', port = 443;
      // Don't do any validation here. The caller is responsible for validating the result of parsing.
      if (typeof dataURL === 'string') {
          // Parse scheme.
          let colonInd = dataURL.indexOf('//');
          if (colonInd >= 0) {
              scheme = dataURL.substring(0, colonInd - 1);
              dataURL = dataURL.substring(colonInd + 2);
          }
          // Parse host, path, and query string.
          let slashInd = dataURL.indexOf('/');
          if (slashInd === -1) {
              slashInd = dataURL.length;
          }
          let questionMarkInd = dataURL.indexOf('?');
          if (questionMarkInd === -1) {
              questionMarkInd = dataURL.length;
          }
          host = dataURL.substring(0, Math.min(slashInd, questionMarkInd));
          if (slashInd < questionMarkInd) {
              // For pathString, questionMarkInd will always come after slashInd
              pathString = decodePath(dataURL.substring(slashInd, questionMarkInd));
          }
          let queryParams = decodeQuery(dataURL.substring(Math.min(dataURL.length, questionMarkInd)));
          // If we have a port, use scheme for determining if it's secure.
          colonInd = host.indexOf(':');
          if (colonInd >= 0) {
              secure = scheme === 'https' || scheme === 'wss';
              port = parseInt(host.substring(colonInd + 1), 10);
          }
          else {
              colonInd = dataURL.length;
          }
          const parts = host.split('.');
          if (parts.length === 3) {
              // Normalize namespaces to lowercase to share storage / connection.
              domain = parts[1];
              subdomain = parts[0].toLowerCase();
          }
          else if (parts.length === 2) {
              domain = parts[0];
          }
          else if (parts[0].slice(0, colonInd).toLowerCase() === 'localhost') {
              domain = 'localhost';
          }
          // Support `ns` query param if subdomain not already set
          if (subdomain === '' && 'ns' in queryParams) {
              subdomain = queryParams['ns'];
          }
      }
      return {
          host,
          port,
          domain,
          subdomain,
          secure,
          scheme,
          pathString
      };
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * True for invalid Firebase keys
   * @type {RegExp}
   * @private
   */
  const INVALID_KEY_REGEX_ = /[\[\].#$\/\u0000-\u001F\u007F]/;
  /**
   * True for invalid Firebase paths.
   * Allows '/' in paths.
   * @type {RegExp}
   * @private
   */
  const INVALID_PATH_REGEX_ = /[\[\].#$\u0000-\u001F\u007F]/;
  /**
   * Maximum number of characters to allow in leaf value
   * @type {number}
   * @private
   */
  const MAX_LEAF_SIZE_ = 10 * 1024 * 1024;
  /**
   * @param {*} key
   * @return {boolean}
   */
  const isValidKey = function (key) {
      return (typeof key === 'string' && key.length !== 0 && !INVALID_KEY_REGEX_.test(key));
  };
  /**
   * @param {string} pathString
   * @return {boolean}
   */
  const isValidPathString = function (pathString) {
      return (typeof pathString === 'string' &&
          pathString.length !== 0 &&
          !INVALID_PATH_REGEX_.test(pathString));
  };
  /**
   * @param {string} pathString
   * @return {boolean}
   */
  const isValidRootPathString = function (pathString) {
      if (pathString) {
          // Allow '/.info/' at the beginning.
          pathString = pathString.replace(/^\/*\.info(\/|$)/, '/');
      }
      return isValidPathString(pathString);
  };
  /**
   * @param {*} priority
   * @return {boolean}
   */
  const isValidPriority = function (priority) {
      return (priority === null ||
          typeof priority === 'string' ||
          (typeof priority === 'number' && !isInvalidJSONNumber(priority)) ||
          (priority && typeof priority === 'object' && contains(priority, '.sv')));
  };
  /**
   * Pre-validate a datum passed as an argument to Firebase function.
   *
   * @param {string} fnName
   * @param {number} argumentNumber
   * @param {*} data
   * @param {!Path} path
   * @param {boolean} optional
   */
  const validateFirebaseDataArg = function (fnName, argumentNumber, data, path, optional) {
      if (optional && data === undefined)
          return;
      validateFirebaseData(errorPrefix(fnName, argumentNumber, optional), data, path);
  };
  /**
   * Validate a data object client-side before sending to server.
   *
   * @param {string} errorPrefix
   * @param {*} data
   * @param {!Path|!ValidationPath} path_
   */
  const validateFirebaseData = function (errorPrefix, data, path_) {
      const path = path_ instanceof Path ? new ValidationPath(path_, errorPrefix) : path_;
      if (data === undefined) {
          throw new Error(errorPrefix + 'contains undefined ' + path.toErrorString());
      }
      if (typeof data === 'function') {
          throw new Error(errorPrefix +
              'contains a function ' +
              path.toErrorString() +
              ' with contents = ' +
              data.toString());
      }
      if (isInvalidJSONNumber(data)) {
          throw new Error(errorPrefix + 'contains ' + data.toString() + ' ' + path.toErrorString());
      }
      // Check max leaf size, but try to avoid the utf8 conversion if we can.
      if (typeof data === 'string' &&
          data.length > MAX_LEAF_SIZE_ / 3 &&
          stringLength(data) > MAX_LEAF_SIZE_) {
          throw new Error(errorPrefix +
              'contains a string greater than ' +
              MAX_LEAF_SIZE_ +
              ' utf8 bytes ' +
              path.toErrorString() +
              " ('" +
              data.substring(0, 50) +
              "...')");
      }
      // TODO = Perf = Consider combining the recursive validation of keys into NodeFromJSON
      // to save extra walking of large objects.
      if (data && typeof data === 'object') {
          let hasDotValue = false, hasActualChild = false;
          forEach(data, function (key, value) {
              if (key === '.value') {
                  hasDotValue = true;
              }
              else if (key !== '.priority' && key !== '.sv') {
                  hasActualChild = true;
                  if (!isValidKey(key)) {
                      throw new Error(errorPrefix +
                          ' contains an invalid key (' +
                          key +
                          ') ' +
                          path.toErrorString() +
                          '.  Keys must be non-empty strings ' +
                          'and can\'t contain ".", "#", "$", "/", "[", or "]"');
                  }
              }
              path.push(key);
              validateFirebaseData(errorPrefix, value, path);
              path.pop();
          });
          if (hasDotValue && hasActualChild) {
              throw new Error(errorPrefix +
                  ' contains ".value" child ' +
                  path.toErrorString() +
                  ' in addition to actual children.');
          }
      }
  };
  /**
   * Pre-validate paths passed in the firebase function.
   *
   * @param {string} errorPrefix
   * @param {Array<!Path>} mergePaths
   */
  const validateFirebaseMergePaths = function (errorPrefix, mergePaths) {
      let i, curPath;
      for (i = 0; i < mergePaths.length; i++) {
          curPath = mergePaths[i];
          const keys = curPath.slice();
          for (let j = 0; j < keys.length; j++) {
              if (keys[j] === '.priority' && j === keys.length - 1) ;
              else if (!isValidKey(keys[j])) {
                  throw new Error(errorPrefix +
                      'contains an invalid key (' +
                      keys[j] +
                      ') in path ' +
                      curPath.toString() +
                      '. Keys must be non-empty strings ' +
                      'and can\'t contain ".", "#", "$", "/", "[", or "]"');
              }
          }
      }
      // Check that update keys are not descendants of each other.
      // We rely on the property that sorting guarantees that ancestors come
      // right before descendants.
      mergePaths.sort(Path.comparePaths);
      let prevPath = null;
      for (i = 0; i < mergePaths.length; i++) {
          curPath = mergePaths[i];
          if (prevPath !== null && prevPath.contains(curPath)) {
              throw new Error(errorPrefix +
                  'contains a path ' +
                  prevPath.toString() +
                  ' that is ancestor of another path ' +
                  curPath.toString());
          }
          prevPath = curPath;
      }
  };
  /**
   * pre-validate an object passed as an argument to firebase function (
   * must be an object - e.g. for firebase.update()).
   *
   * @param {string} fnName
   * @param {number} argumentNumber
   * @param {*} data
   * @param {!Path} path
   * @param {boolean} optional
   */
  const validateFirebaseMergeDataArg = function (fnName, argumentNumber, data, path, optional) {
      if (optional && data === undefined)
          return;
      const errorPrefix$1 = errorPrefix(fnName, argumentNumber, optional);
      if (!(data && typeof data === 'object') || Array.isArray(data)) {
          throw new Error(errorPrefix$1 + ' must be an object containing the children to replace.');
      }
      const mergePaths = [];
      forEach(data, function (key, value) {
          const curPath = new Path(key);
          validateFirebaseData(errorPrefix$1, value, path.child(curPath));
          if (curPath.getBack() === '.priority') {
              if (!isValidPriority(value)) {
                  throw new Error(errorPrefix$1 +
                      "contains an invalid value for '" +
                      curPath.toString() +
                      "', which must be a valid " +
                      'Firebase priority (a string, finite number, server value, or null).');
              }
          }
          mergePaths.push(curPath);
      });
      validateFirebaseMergePaths(errorPrefix$1, mergePaths);
  };
  const validatePriority = function (fnName, argumentNumber, priority, optional) {
      if (optional && priority === undefined)
          return;
      if (isInvalidJSONNumber(priority))
          throw new Error(errorPrefix(fnName, argumentNumber, optional) +
              'is ' +
              priority.toString() +
              ', but must be a valid Firebase priority (a string, finite number, ' +
              'server value, or null).');
      // Special case to allow importing data with a .sv.
      if (!isValidPriority(priority))
          throw new Error(errorPrefix(fnName, argumentNumber, optional) +
              'must be a valid Firebase priority ' +
              '(a string, finite number, server value, or null).');
  };
  const validateEventType = function (fnName, argumentNumber, eventType, optional) {
      if (optional && eventType === undefined)
          return;
      switch (eventType) {
          case 'value':
          case 'child_added':
          case 'child_removed':
          case 'child_changed':
          case 'child_moved':
              break;
          default:
              throw new Error(errorPrefix(fnName, argumentNumber, optional) +
                  'must be a valid event type = "value", "child_added", "child_removed", ' +
                  '"child_changed", or "child_moved".');
      }
  };
  const validateKey = function (fnName, argumentNumber, key, optional) {
      if (optional && key === undefined)
          return;
      if (!isValidKey(key))
          throw new Error(errorPrefix(fnName, argumentNumber, optional) +
              'was an invalid key = "' +
              key +
              '".  Firebase keys must be non-empty strings and ' +
              'can\'t contain ".", "#", "$", "/", "[", or "]").');
  };
  const validatePathString = function (fnName, argumentNumber, pathString, optional) {
      if (optional && pathString === undefined)
          return;
      if (!isValidPathString(pathString))
          throw new Error(errorPrefix(fnName, argumentNumber, optional) +
              'was an invalid path = "' +
              pathString +
              '". Paths must be non-empty strings and ' +
              'can\'t contain ".", "#", "$", "[", or "]"');
  };
  const validateRootPathString = function (fnName, argumentNumber, pathString, optional) {
      if (pathString) {
          // Allow '/.info/' at the beginning.
          pathString = pathString.replace(/^\/*\.info(\/|$)/, '/');
      }
      validatePathString(fnName, argumentNumber, pathString, optional);
  };
  const validateWritablePath = function (fnName, path) {
      if (path.getFront() === '.info') {
          throw new Error(fnName + " failed = Can't modify data under /.info/");
      }
  };
  const validateUrl = function (fnName, argumentNumber, parsedUrl) {
      // TODO = Validate server better.
      const pathString = parsedUrl.path.toString();
      if (!(typeof parsedUrl.repoInfo.host === 'string') ||
          parsedUrl.repoInfo.host.length === 0 ||
          (!isValidKey(parsedUrl.repoInfo.namespace) &&
              parsedUrl.repoInfo.host.split(':')[0] !== 'localhost') ||
          (pathString.length !== 0 && !isValidRootPathString(pathString))) {
          throw new Error(errorPrefix(fnName, argumentNumber, false) +
              'must be a valid firebase URL and ' +
              'the path can\'t contain ".", "#", "$", "[", or "]".');
      }
  };
  const validateBoolean = function (fnName, argumentNumber, bool, optional) {
      if (optional && bool === undefined)
          return;
      if (typeof bool !== 'boolean')
          throw new Error(errorPrefix(fnName, argumentNumber, optional) + 'must be a boolean.');
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @constructor
   */
  class OnDisconnect {
      /**
       * @param {!Repo} repo_
       * @param {!Path} path_
       */
      constructor(repo_, path_) {
          this.repo_ = repo_;
          this.path_ = path_;
      }
      /**
       * @param {function(?Error)=} onComplete
       * @return {!firebase.Promise}
       */
      cancel(onComplete) {
          validateArgCount('OnDisconnect.cancel', 0, 1, arguments.length);
          validateCallback('OnDisconnect.cancel', 1, onComplete, true);
          const deferred = new Deferred();
          this.repo_.onDisconnectCancel(this.path_, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
      /**
       * @param {function(?Error)=} onComplete
       * @return {!firebase.Promise}
       */
      remove(onComplete) {
          validateArgCount('OnDisconnect.remove', 0, 1, arguments.length);
          validateWritablePath('OnDisconnect.remove', this.path_);
          validateCallback('OnDisconnect.remove', 1, onComplete, true);
          const deferred = new Deferred();
          this.repo_.onDisconnectSet(this.path_, null, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
      /**
       * @param {*} value
       * @param {function(?Error)=} onComplete
       * @return {!firebase.Promise}
       */
      set(value, onComplete) {
          validateArgCount('OnDisconnect.set', 1, 2, arguments.length);
          validateWritablePath('OnDisconnect.set', this.path_);
          validateFirebaseDataArg('OnDisconnect.set', 1, value, this.path_, false);
          validateCallback('OnDisconnect.set', 2, onComplete, true);
          const deferred = new Deferred();
          this.repo_.onDisconnectSet(this.path_, value, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
      /**
       * @param {*} value
       * @param {number|string|null} priority
       * @param {function(?Error)=} onComplete
       * @return {!firebase.Promise}
       */
      setWithPriority(value, priority, onComplete) {
          validateArgCount('OnDisconnect.setWithPriority', 2, 3, arguments.length);
          validateWritablePath('OnDisconnect.setWithPriority', this.path_);
          validateFirebaseDataArg('OnDisconnect.setWithPriority', 1, value, this.path_, false);
          validatePriority('OnDisconnect.setWithPriority', 2, priority, false);
          validateCallback('OnDisconnect.setWithPriority', 3, onComplete, true);
          const deferred = new Deferred();
          this.repo_.onDisconnectSetWithPriority(this.path_, value, priority, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
      /**
       * @param {!Object} objectToMerge
       * @param {function(?Error)=} onComplete
       * @return {!firebase.Promise}
       */
      update(objectToMerge, onComplete) {
          validateArgCount('OnDisconnect.update', 1, 2, arguments.length);
          validateWritablePath('OnDisconnect.update', this.path_);
          if (Array.isArray(objectToMerge)) {
              const newObjectToMerge = {};
              for (let i = 0; i < objectToMerge.length; ++i) {
                  newObjectToMerge['' + i] = objectToMerge[i];
              }
              objectToMerge = newObjectToMerge;
              warn('Passing an Array to firebase.database.onDisconnect().update() is deprecated. Use set() if you want to overwrite the ' +
                  'existing data, or an Object with integer keys if you really do want to only update some of the children.');
          }
          validateFirebaseMergeDataArg('OnDisconnect.update', 1, objectToMerge, this.path_, false);
          validateCallback('OnDisconnect.update', 2, onComplete, true);
          const deferred = new Deferred();
          this.repo_.onDisconnectUpdate(this.path_, objectToMerge, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  class TransactionResult {
      /**
       * A type for the resolve value of Firebase.transaction.
       * @constructor
       * @dict
       * @param {boolean} committed
       * @param {DataSnapshot} snapshot
       */
      constructor(committed, snapshot) {
          this.committed = committed;
          this.snapshot = snapshot;
      }
      // Do not create public documentation. This is intended to make JSON serialization work but is otherwise unnecessary
      // for end-users
      toJSON() {
          validateArgCount('TransactionResult.toJSON', 0, 1, arguments.length);
          return { committed: this.committed, snapshot: this.snapshot.toJSON() };
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Fancy ID generator that creates 20-character string identifiers with the
   * following properties:
   *
   * 1. They're based on timestamp so that they sort *after* any existing ids.
   * 2. They contain 72-bits of random data after the timestamp so that IDs won't
   *    collide with other clients' IDs.
   * 3. They sort *lexicographically* (so the timestamp is converted to characters
   *    that will sort properly).
   * 4. They're monotonically increasing. Even if you generate more than one in
   *    the same timestamp, the latter ones will sort after the former ones. We do
   *    this by using the previous random bits but "incrementing" them by 1 (only
   *    in the case of a timestamp collision).
   */
  const nextPushId = (function () {
      // Modeled after base64 web-safe chars, but ordered by ASCII.
      const PUSH_CHARS = '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';
      // Timestamp of last push, used to prevent local collisions if you push twice
      // in one ms.
      let lastPushTime = 0;
      // We generate 72-bits of randomness which get turned into 12 characters and
      // appended to the timestamp to prevent collisions with other clients. We
      // store the last characters we generated because in the event of a collision,
      // we'll use those same characters except "incremented" by one.
      const lastRandChars = [];
      return function (now) {
          const duplicateTime = now === lastPushTime;
          lastPushTime = now;
          let i;
          const timeStampChars = new Array(8);
          for (i = 7; i >= 0; i--) {
              timeStampChars[i] = PUSH_CHARS.charAt(now % 64);
              // NOTE: Can't use << here because javascript will convert to int and lose
              // the upper bits.
              now = Math.floor(now / 64);
          }
          assert(now === 0, 'Cannot push at time == 0');
          let id = timeStampChars.join('');
          if (!duplicateTime) {
              for (i = 0; i < 12; i++) {
                  lastRandChars[i] = Math.floor(Math.random() * 64);
              }
          }
          else {
              // If the timestamp hasn't changed since last push, use the same random
              // number, except incremented by 1.
              for (i = 11; i >= 0 && lastRandChars[i] === 63; i--) {
                  lastRandChars[i] = 0;
              }
              lastRandChars[i]++;
          }
          for (i = 0; i < 12; i++) {
              id += PUSH_CHARS.charAt(lastRandChars[i]);
          }
          assert(id.length === 20, 'nextPushId: Length should be 20.');
          return id;
      };
  })();
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   *
   * @param {!string} name
   * @param {!Node} node
   * @constructor
   * @struct
   */
  class NamedNode {
      constructor(name, node) {
          this.name = name;
          this.node = node;
      }
      /**
       *
       * @param {!string} name
       * @param {!Node} node
       * @return {NamedNode}
       */
      static Wrap(name, node) {
          return new NamedNode(name, node);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   *
   * @constructor
   */
  class Index {
      /**
       * @return {function(!NamedNode, !NamedNode):number} A standalone comparison function for
       * this index
       */
      getCompare() {
          return this.compare.bind(this);
      }
      /**
       * Given a before and after value for a node, determine if the indexed value has changed. Even if they are different,
       * it's possible that the changes are isolated to parts of the snapshot that are not indexed.
       *
       * @param {!Node} oldNode
       * @param {!Node} newNode
       * @return {boolean} True if the portion of the snapshot being indexed changed between oldNode and newNode
       */
      indexedValueChanged(oldNode, newNode) {
          const oldWrapped = new NamedNode(MIN_NAME, oldNode);
          const newWrapped = new NamedNode(MIN_NAME, newNode);
          return this.compare(oldWrapped, newWrapped) !== 0;
      }
      /**
       * @return {!NamedNode} a node wrapper that will sort equal to or less than
       * any other node wrapper, using this index
       */
      minPost() {
          return NamedNode.MIN;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  let __EMPTY_NODE;
  class KeyIndex extends Index {
      static get __EMPTY_NODE() {
          return __EMPTY_NODE;
      }
      static set __EMPTY_NODE(val) {
          __EMPTY_NODE = val;
      }
      /**
       * @inheritDoc
       */
      compare(a, b) {
          return nameCompare(a.name, b.name);
      }
      /**
       * @inheritDoc
       */
      isDefinedOn(node) {
          // We could probably return true here (since every node has a key), but it's never called
          // so just leaving unimplemented for now.
          throw assertionError('KeyIndex.isDefinedOn not expected to be called.');
      }
      /**
       * @inheritDoc
       */
      indexedValueChanged(oldNode, newNode) {
          return false; // The key for a node never changes.
      }
      /**
       * @inheritDoc
       */
      minPost() {
          return NamedNode.MIN;
      }
      /**
       * @inheritDoc
       */
      maxPost() {
          // TODO: This should really be created once and cached in a static property, but
          // NamedNode isn't defined yet, so I can't use it in a static.  Bleh.
          return new NamedNode(MAX_NAME, __EMPTY_NODE);
      }
      /**
       * @param {*} indexValue
       * @param {string} name
       * @return {!NamedNode}
       */
      makePost(indexValue, name) {
          assert(typeof indexValue === 'string', 'KeyIndex indexValue must always be a string.');
          // We just use empty node, but it'll never be compared, since our comparator only looks at name.
          return new NamedNode(indexValue, __EMPTY_NODE);
      }
      /**
       * @return {!string} String representation for inclusion in a query spec
       */
      toString() {
          return '.key';
      }
  }
  const KEY_INDEX = new KeyIndex();
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  let MAX_NODE;
  function setMaxNode(val) {
      MAX_NODE = val;
  }
  /**
   * @param {(!string|!number)} priority
   * @return {!string}
   */
  const priorityHashText = function (priority) {
      if (typeof priority === 'number')
          return 'number:' + doubleToIEEE754String(priority);
      else
          return 'string:' + priority;
  };
  /**
   * Validates that a priority snapshot Node is valid.
   *
   * @param {!Node} priorityNode
   */
  const validatePriorityNode = function (priorityNode) {
      if (priorityNode.isLeafNode()) {
          const val = priorityNode.val();
          assert(typeof val === 'string' ||
              typeof val === 'number' ||
              (typeof val === 'object' &&
                  contains(val, '.sv')), 'Priority must be a string or number.');
      }
      else {
          assert(priorityNode === MAX_NODE || priorityNode.isEmpty(), 'priority of unexpected type.');
      }
      // Don't call getPriority() on MAX_NODE to avoid hitting assertion.
      assert(priorityNode === MAX_NODE || priorityNode.getPriority().isEmpty(), "Priority nodes can't have a priority of their own.");
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  let __childrenNodeConstructor;
  /**
   * LeafNode is a class for storing leaf nodes in a DataSnapshot.  It
   * implements Node and stores the value of the node (a string,
   * number, or boolean) accessible via getValue().
   */
  class LeafNode {
      /**
       * @implements {Node}
       * @param {!(string|number|boolean|Object)} value_ The value to store in this leaf node.
       *                                         The object type is possible in the event of a deferred value
       * @param {!Node=} priorityNode_ The priority of this node.
       */
      constructor(value_, priorityNode_ = LeafNode.__childrenNodeConstructor.EMPTY_NODE) {
          this.value_ = value_;
          this.priorityNode_ = priorityNode_;
          this.lazyHash_ = null;
          assert(this.value_ !== undefined && this.value_ !== null, "LeafNode shouldn't be created with null/undefined value.");
          validatePriorityNode(this.priorityNode_);
      }
      static set __childrenNodeConstructor(val) {
          __childrenNodeConstructor = val;
      }
      static get __childrenNodeConstructor() {
          return __childrenNodeConstructor;
      }
      /** @inheritDoc */
      isLeafNode() {
          return true;
      }
      /** @inheritDoc */
      getPriority() {
          return this.priorityNode_;
      }
      /** @inheritDoc */
      updatePriority(newPriorityNode) {
          return new LeafNode(this.value_, newPriorityNode);
      }
      /** @inheritDoc */
      getImmediateChild(childName) {
          // Hack to treat priority as a regular child
          if (childName === '.priority') {
              return this.priorityNode_;
          }
          else {
              return LeafNode.__childrenNodeConstructor.EMPTY_NODE;
          }
      }
      /** @inheritDoc */
      getChild(path) {
          if (path.isEmpty()) {
              return this;
          }
          else if (path.getFront() === '.priority') {
              return this.priorityNode_;
          }
          else {
              return LeafNode.__childrenNodeConstructor.EMPTY_NODE;
          }
      }
      /**
       * @inheritDoc
       */
      hasChild() {
          return false;
      }
      /** @inheritDoc */
      getPredecessorChildName(childName, childNode) {
          return null;
      }
      /** @inheritDoc */
      updateImmediateChild(childName, newChildNode) {
          if (childName === '.priority') {
              return this.updatePriority(newChildNode);
          }
          else if (newChildNode.isEmpty() && childName !== '.priority') {
              return this;
          }
          else {
              return LeafNode.__childrenNodeConstructor.EMPTY_NODE.updateImmediateChild(childName, newChildNode).updatePriority(this.priorityNode_);
          }
      }
      /** @inheritDoc */
      updateChild(path, newChildNode) {
          const front = path.getFront();
          if (front === null) {
              return newChildNode;
          }
          else if (newChildNode.isEmpty() && front !== '.priority') {
              return this;
          }
          else {
              assert(front !== '.priority' || path.getLength() === 1, '.priority must be the last token in a path');
              return this.updateImmediateChild(front, LeafNode.__childrenNodeConstructor.EMPTY_NODE.updateChild(path.popFront(), newChildNode));
          }
      }
      /** @inheritDoc */
      isEmpty() {
          return false;
      }
      /** @inheritDoc */
      numChildren() {
          return 0;
      }
      /** @inheritDoc */
      forEachChild(index, action) {
          return false;
      }
      /**
       * @inheritDoc
       */
      val(exportFormat) {
          if (exportFormat && !this.getPriority().isEmpty())
              return {
                  '.value': this.getValue(),
                  '.priority': this.getPriority().val()
              };
          else
              return this.getValue();
      }
      /** @inheritDoc */
      hash() {
          if (this.lazyHash_ === null) {
              let toHash = '';
              if (!this.priorityNode_.isEmpty())
                  toHash +=
                      'priority:' +
                          priorityHashText(this.priorityNode_.val()) +
                          ':';
              const type = typeof this.value_;
              toHash += type + ':';
              if (type === 'number') {
                  toHash += doubleToIEEE754String(this.value_);
              }
              else {
                  toHash += this.value_;
              }
              this.lazyHash_ = sha1(toHash);
          }
          return this.lazyHash_;
      }
      /**
       * Returns the value of the leaf node.
       * @return {Object|string|number|boolean} The value of the node.
       */
      getValue() {
          return this.value_;
      }
      /**
       * @inheritDoc
       */
      compareTo(other) {
          if (other === LeafNode.__childrenNodeConstructor.EMPTY_NODE) {
              return 1;
          }
          else if (other instanceof LeafNode.__childrenNodeConstructor) {
              return -1;
          }
          else {
              assert(other.isLeafNode(), 'Unknown node type');
              return this.compareToLeafNode_(other);
          }
      }
      /**
       * Comparison specifically for two leaf nodes
       * @param {!LeafNode} otherLeaf
       * @return {!number}
       * @private
       */
      compareToLeafNode_(otherLeaf) {
          const otherLeafType = typeof otherLeaf.value_;
          const thisLeafType = typeof this.value_;
          const otherIndex = LeafNode.VALUE_TYPE_ORDER.indexOf(otherLeafType);
          const thisIndex = LeafNode.VALUE_TYPE_ORDER.indexOf(thisLeafType);
          assert(otherIndex >= 0, 'Unknown leaf type: ' + otherLeafType);
          assert(thisIndex >= 0, 'Unknown leaf type: ' + thisLeafType);
          if (otherIndex === thisIndex) {
              // Same type, compare values
              if (thisLeafType === 'object') {
                  // Deferred value nodes are all equal, but we should also never get to this point...
                  return 0;
              }
              else {
                  // Note that this works because true > false, all others are number or string comparisons
                  if (this.value_ < otherLeaf.value_) {
                      return -1;
                  }
                  else if (this.value_ === otherLeaf.value_) {
                      return 0;
                  }
                  else {
                      return 1;
                  }
              }
          }
          else {
              return thisIndex - otherIndex;
          }
      }
      /**
       * @inheritDoc
       */
      withIndex() {
          return this;
      }
      /**
       * @inheritDoc
       */
      isIndexed() {
          return true;
      }
      /**
       * @inheritDoc
       */
      equals(other) {
          /**
           * @inheritDoc
           */
          if (other === this) {
              return true;
          }
          else if (other.isLeafNode()) {
              const otherLeaf = other;
              return (this.value_ === otherLeaf.value_ &&
                  this.priorityNode_.equals(otherLeaf.priorityNode_));
          }
          else {
              return false;
          }
      }
  }
  /**
   * The sort order for comparing leaf nodes of different types. If two leaf nodes have
   * the same type, the comparison falls back to their value
   * @type {Array.<!string>}
   * @const
   */
  LeafNode.VALUE_TYPE_ORDER = ['object', 'boolean', 'number', 'string'];
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  let nodeFromJSON;
  let MAX_NODE$1;
  function setNodeFromJSON(val) {
      nodeFromJSON = val;
  }
  function setMaxNode$1(val) {
      MAX_NODE$1 = val;
  }
  /**
   * @constructor
   * @extends {Index}
   * @private
   */
  class PriorityIndex extends Index {
      /**
       * @inheritDoc
       */
      compare(a, b) {
          const aPriority = a.node.getPriority();
          const bPriority = b.node.getPriority();
          const indexCmp = aPriority.compareTo(bPriority);
          if (indexCmp === 0) {
              return nameCompare(a.name, b.name);
          }
          else {
              return indexCmp;
          }
      }
      /**
       * @inheritDoc
       */
      isDefinedOn(node) {
          return !node.getPriority().isEmpty();
      }
      /**
       * @inheritDoc
       */
      indexedValueChanged(oldNode, newNode) {
          return !oldNode.getPriority().equals(newNode.getPriority());
      }
      /**
       * @inheritDoc
       */
      minPost() {
          return NamedNode.MIN;
      }
      /**
       * @inheritDoc
       */
      maxPost() {
          return new NamedNode(MAX_NAME, new LeafNode('[PRIORITY-POST]', MAX_NODE$1));
      }
      /**
       * @param {*} indexValue
       * @param {string} name
       * @return {!NamedNode}
       */
      makePost(indexValue, name) {
          const priorityNode = nodeFromJSON(indexValue);
          return new NamedNode(name, new LeafNode('[PRIORITY-POST]', priorityNode));
      }
      /**
       * @return {!string} String representation for inclusion in a query spec
       */
      toString() {
          return '.priority';
      }
  }
  const PRIORITY_INDEX = new PriorityIndex();
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * An iterator over an LLRBNode.
   */
  class SortedMapIterator {
      /**
       * @template K, V, T
       * @param {LLRBNode|LLRBEmptyNode} node Node to iterate.
       * @param {?K} startKey
       * @param {function(K, K): number} comparator
       * @param {boolean} isReverse_ Whether or not to iterate in reverse
       * @param {(function(K, V):T)=} resultGenerator_
       */
      constructor(node, startKey, comparator, isReverse_, resultGenerator_ = null) {
          this.isReverse_ = isReverse_;
          this.resultGenerator_ = resultGenerator_;
          /** @private
           * @type {Array.<!LLRBNode>}
           */
          this.nodeStack_ = [];
          let cmp = 1;
          while (!node.isEmpty()) {
              node = node;
              cmp = startKey ? comparator(node.key, startKey) : 1;
              // flip the comparison if we're going in reverse
              if (isReverse_)
                  cmp *= -1;
              if (cmp < 0) {
                  // This node is less than our start key. ignore it
                  if (this.isReverse_) {
                      node = node.left;
                  }
                  else {
                      node = node.right;
                  }
              }
              else if (cmp === 0) {
                  // This node is exactly equal to our start key. Push it on the stack, but stop iterating;
                  this.nodeStack_.push(node);
                  break;
              }
              else {
                  // This node is greater than our start key, add it to the stack and move to the next one
                  this.nodeStack_.push(node);
                  if (this.isReverse_) {
                      node = node.right;
                  }
                  else {
                      node = node.left;
                  }
              }
          }
      }
      getNext() {
          if (this.nodeStack_.length === 0)
              return null;
          let node = this.nodeStack_.pop();
          let result;
          if (this.resultGenerator_)
              result = this.resultGenerator_(node.key, node.value);
          else
              result = { key: node.key, value: node.value };
          if (this.isReverse_) {
              node = node.left;
              while (!node.isEmpty()) {
                  this.nodeStack_.push(node);
                  node = node.right;
              }
          }
          else {
              node = node.right;
              while (!node.isEmpty()) {
                  this.nodeStack_.push(node);
                  node = node.left;
              }
          }
          return result;
      }
      hasNext() {
          return this.nodeStack_.length > 0;
      }
      peek() {
          if (this.nodeStack_.length === 0)
              return null;
          const node = this.nodeStack_[this.nodeStack_.length - 1];
          if (this.resultGenerator_) {
              return this.resultGenerator_(node.key, node.value);
          }
          else {
              return { key: node.key, value: node.value };
          }
      }
  }
  /**
   * Represents a node in a Left-leaning Red-Black tree.
   */
  class LLRBNode {
      /**
       * @template K, V
       * @param {!K} key Key associated with this node.
       * @param {!V} value Value associated with this node.
       * @param {?boolean} color Whether this node is red.
       * @param {?(LLRBNode|LLRBEmptyNode)=} left Left child.
       * @param {?(LLRBNode|LLRBEmptyNode)=} right Right child.
       */
      constructor(key, value, color, left, right) {
          this.key = key;
          this.value = value;
          this.color = color != null ? color : LLRBNode.RED;
          this.left =
              left != null ? left : SortedMap.EMPTY_NODE;
          this.right =
              right != null ? right : SortedMap.EMPTY_NODE;
      }
      /**
       * Returns a copy of the current node, optionally replacing pieces of it.
       *
       * @param {?K} key New key for the node, or null.
       * @param {?V} value New value for the node, or null.
       * @param {?boolean} color New color for the node, or null.
       * @param {?LLRBNode|LLRBEmptyNode} left New left child for the node, or null.
       * @param {?LLRBNode|LLRBEmptyNode} right New right child for the node, or null.
       * @return {!LLRBNode} The node copy.
       */
      copy(key, value, color, left, right) {
          return new LLRBNode(key != null ? key : this.key, value != null ? value : this.value, color != null ? color : this.color, left != null ? left : this.left, right != null ? right : this.right);
      }
      /**
       * @return {number} The total number of nodes in the tree.
       */
      count() {
          return this.left.count() + 1 + this.right.count();
      }
      /**
       * @return {boolean} True if the tree is empty.
       */
      isEmpty() {
          return false;
      }
      /**
       * Traverses the tree in key order and calls the specified action function
       * for each node.
       *
       * @param {function(!K, !V):*} action Callback function to be called for each
       *   node.  If it returns true, traversal is aborted.
       * @return {*} The first truthy value returned by action, or the last falsey
       *   value returned by action
       */
      inorderTraversal(action) {
          return (this.left.inorderTraversal(action) ||
              action(this.key, this.value) ||
              this.right.inorderTraversal(action));
      }
      /**
       * Traverses the tree in reverse key order and calls the specified action function
       * for each node.
       *
       * @param {function(!Object, !Object)} action Callback function to be called for each
       * node.  If it returns true, traversal is aborted.
       * @return {*} True if traversal was aborted.
       */
      reverseTraversal(action) {
          return (this.right.reverseTraversal(action) ||
              action(this.key, this.value) ||
              this.left.reverseTraversal(action));
      }
      /**
       * @return {!Object} The minimum node in the tree.
       * @private
       */
      min_() {
          if (this.left.isEmpty()) {
              return this;
          }
          else {
              return this.left.min_();
          }
      }
      /**
       * @return {!K} The maximum key in the tree.
       */
      minKey() {
          return this.min_().key;
      }
      /**
       * @return {!K} The maximum key in the tree.
       */
      maxKey() {
          if (this.right.isEmpty()) {
              return this.key;
          }
          else {
              return this.right.maxKey();
          }
      }
      /**
       *
       * @param {!Object} key Key to insert.
       * @param {!Object} value Value to insert.
       * @param {Comparator} comparator Comparator.
       * @return {!LLRBNode} New tree, with the key/value added.
       */
      insert(key, value, comparator) {
          let cmp, n;
          n = this;
          cmp = comparator(key, n.key);
          if (cmp < 0) {
              n = n.copy(null, null, null, n.left.insert(key, value, comparator), null);
          }
          else if (cmp === 0) {
              n = n.copy(null, value, null, null, null);
          }
          else {
              n = n.copy(null, null, null, null, n.right.insert(key, value, comparator));
          }
          return n.fixUp_();
      }
      /**
       * @private
       * @return {!LLRBNode|LLRBEmptyNode} New tree, with the minimum key removed.
       */
      removeMin_() {
          if (this.left.isEmpty()) {
              return SortedMap.EMPTY_NODE;
          }
          let n = this;
          if (!n.left.isRed_() && !n.left.left.isRed_())
              n = n.moveRedLeft_();
          n = n.copy(null, null, null, n.left.removeMin_(), null);
          return n.fixUp_();
      }
      /**
       * @param {!Object} key The key of the item to remove.
       * @param {Comparator} comparator Comparator.
       * @return {!LLRBNode|LLRBEmptyNode} New tree, with the specified item removed.
       */
      remove(key, comparator) {
          let n, smallest;
          n = this;
          if (comparator(key, n.key) < 0) {
              if (!n.left.isEmpty() && !n.left.isRed_() && !n.left.left.isRed_()) {
                  n = n.moveRedLeft_();
              }
              n = n.copy(null, null, null, n.left.remove(key, comparator), null);
          }
          else {
              if (n.left.isRed_())
                  n = n.rotateRight_();
              if (!n.right.isEmpty() && !n.right.isRed_() && !n.right.left.isRed_()) {
                  n = n.moveRedRight_();
              }
              if (comparator(key, n.key) === 0) {
                  if (n.right.isEmpty()) {
                      return SortedMap.EMPTY_NODE;
                  }
                  else {
                      smallest = n.right.min_();
                      n = n.copy(smallest.key, smallest.value, null, null, n.right.removeMin_());
                  }
              }
              n = n.copy(null, null, null, null, n.right.remove(key, comparator));
          }
          return n.fixUp_();
      }
      /**
       * @private
       * @return {boolean} Whether this is a RED node.
       */
      isRed_() {
          return this.color;
      }
      /**
       * @private
       * @return {!LLRBNode} New tree after performing any needed rotations.
       */
      fixUp_() {
          let n = this;
          if (n.right.isRed_() && !n.left.isRed_())
              n = n.rotateLeft_();
          if (n.left.isRed_() && n.left.left.isRed_())
              n = n.rotateRight_();
          if (n.left.isRed_() && n.right.isRed_())
              n = n.colorFlip_();
          return n;
      }
      /**
       * @private
       * @return {!LLRBNode} New tree, after moveRedLeft.
       */
      moveRedLeft_() {
          let n = this.colorFlip_();
          if (n.right.left.isRed_()) {
              n = n.copy(null, null, null, null, n.right.rotateRight_());
              n = n.rotateLeft_();
              n = n.colorFlip_();
          }
          return n;
      }
      /**
       * @private
       * @return {!LLRBNode} New tree, after moveRedRight.
       */
      moveRedRight_() {
          let n = this.colorFlip_();
          if (n.left.left.isRed_()) {
              n = n.rotateRight_();
              n = n.colorFlip_();
          }
          return n;
      }
      /**
       * @private
       * @return {!LLRBNode} New tree, after rotateLeft.
       */
      rotateLeft_() {
          const nl = this.copy(null, null, LLRBNode.RED, null, this.right.left);
          return this.right.copy(null, null, this.color, nl, null);
      }
      /**
       * @private
       * @return {!LLRBNode} New tree, after rotateRight.
       */
      rotateRight_() {
          const nr = this.copy(null, null, LLRBNode.RED, this.left.right, null);
          return this.left.copy(null, null, this.color, null, nr);
      }
      /**
       * @private
       * @return {!LLRBNode} New tree, after colorFlip.
       */
      colorFlip_() {
          const left = this.left.copy(null, null, !this.left.color, null, null);
          const right = this.right.copy(null, null, !this.right.color, null, null);
          return this.copy(null, null, !this.color, left, right);
      }
      /**
       * For testing.
       *
       * @private
       * @return {boolean} True if all is well.
       */
      checkMaxDepth_() {
          const blackDepth = this.check_();
          return Math.pow(2.0, blackDepth) <= this.count() + 1;
      }
      /**
       * @private
       * @return {number} Not sure what this returns exactly. :-).
       */
      check_() {
          let blackDepth;
          if (this.isRed_() && this.left.isRed_()) {
              throw new Error('Red node has red child(' + this.key + ',' + this.value + ')');
          }
          if (this.right.isRed_()) {
              throw new Error('Right child of (' + this.key + ',' + this.value + ') is red');
          }
          blackDepth = this.left.check_();
          if (blackDepth !== this.right.check_()) {
              throw new Error('Black depths differ');
          }
          else {
              return blackDepth + (this.isRed_() ? 0 : 1);
          }
      }
  }
  LLRBNode.RED = true;
  LLRBNode.BLACK = false;
  /**
   * Represents an empty node (a leaf node in the Red-Black Tree).
   */
  class LLRBEmptyNode {
      /**
       * Returns a copy of the current node.
       *
       * @return {!LLRBEmptyNode} The node copy.
       */
      copy(key, value, color, left, right) {
          return this;
      }
      /**
       * Returns a copy of the tree, with the specified key/value added.
       *
       * @param {!K} key Key to be added.
       * @param {!V} value Value to be added.
       * @param {Comparator} comparator Comparator.
       * @return {!LLRBNode} New tree, with item added.
       */
      insert(key, value, comparator) {
          return new LLRBNode(key, value, null);
      }
      /**
       * Returns a copy of the tree, with the specified key removed.
       *
       * @param {!K} key The key to remove.
       * @param {Comparator} comparator Comparator.
       * @return {!LLRBEmptyNode} New tree, with item removed.
       */
      remove(key, comparator) {
          return this;
      }
      /**
       * @return {number} The total number of nodes in the tree.
       */
      count() {
          return 0;
      }
      /**
       * @return {boolean} True if the tree is empty.
       */
      isEmpty() {
          return true;
      }
      /**
       * Traverses the tree in key order and calls the specified action function
       * for each node.
       *
       * @param {function(!K, !V):*} action Callback function to be called for each
       * node.  If it returns true, traversal is aborted.
       * @return {boolean} True if traversal was aborted.
       */
      inorderTraversal(action) {
          return false;
      }
      /**
       * Traverses the tree in reverse key order and calls the specified action function
       * for each node.
       *
       * @param {function(!K, !V)} action Callback function to be called for each
       * node.  If it returns true, traversal is aborted.
       * @return {boolean} True if traversal was aborted.
       */
      reverseTraversal(action) {
          return false;
      }
      /**
       * @return {null}
       */
      minKey() {
          return null;
      }
      /**
       * @return {null}
       */
      maxKey() {
          return null;
      }
      /**
       * @private
       * @return {number} Not sure what this returns exactly. :-).
       */
      check_() {
          return 0;
      }
      /**
       * @private
       * @return {boolean} Whether this node is red.
       */
      isRed_() {
          return false;
      }
  }
  /**
   * An immutable sorted map implementation, based on a Left-leaning Red-Black
   * tree.
   */
  class SortedMap {
      /**
       * @template K, V
       * @param {function(K, K):number} comparator_ Key comparator.
       * @param {LLRBNode=} root_ (Optional) Root node for the map.
       */
      constructor(comparator_, root_ = SortedMap.EMPTY_NODE) {
          this.comparator_ = comparator_;
          this.root_ = root_;
      }
      /**
       * Returns a copy of the map, with the specified key/value added or replaced.
       * (TODO: We should perhaps rename this method to 'put')
       *
       * @param {!K} key Key to be added.
       * @param {!V} value Value to be added.
       * @return {!SortedMap.<K, V>} New map, with item added.
       */
      insert(key, value) {
          return new SortedMap(this.comparator_, this.root_
              .insert(key, value, this.comparator_)
              .copy(null, null, LLRBNode.BLACK, null, null));
      }
      /**
       * Returns a copy of the map, with the specified key removed.
       *
       * @param {!K} key The key to remove.
       * @return {!SortedMap.<K, V>} New map, with item removed.
       */
      remove(key) {
          return new SortedMap(this.comparator_, this.root_
              .remove(key, this.comparator_)
              .copy(null, null, LLRBNode.BLACK, null, null));
      }
      /**
       * Returns the value of the node with the given key, or null.
       *
       * @param {!K} key The key to look up.
       * @return {?V} The value of the node with the given key, or null if the
       * key doesn't exist.
       */
      get(key) {
          let cmp;
          let node = this.root_;
          while (!node.isEmpty()) {
              cmp = this.comparator_(key, node.key);
              if (cmp === 0) {
                  return node.value;
              }
              else if (cmp < 0) {
                  node = node.left;
              }
              else if (cmp > 0) {
                  node = node.right;
              }
          }
          return null;
      }
      /**
       * Returns the key of the item *before* the specified key, or null if key is the first item.
       * @param {K} key The key to find the predecessor of
       * @return {?K} The predecessor key.
       */
      getPredecessorKey(key) {
          let cmp, node = this.root_, rightParent = null;
          while (!node.isEmpty()) {
              cmp = this.comparator_(key, node.key);
              if (cmp === 0) {
                  if (!node.left.isEmpty()) {
                      node = node.left;
                      while (!node.right.isEmpty())
                          node = node.right;
                      return node.key;
                  }
                  else if (rightParent) {
                      return rightParent.key;
                  }
                  else {
                      return null; // first item.
                  }
              }
              else if (cmp < 0) {
                  node = node.left;
              }
              else if (cmp > 0) {
                  rightParent = node;
                  node = node.right;
              }
          }
          throw new Error('Attempted to find predecessor key for a nonexistent key.  What gives?');
      }
      /**
       * @return {boolean} True if the map is empty.
       */
      isEmpty() {
          return this.root_.isEmpty();
      }
      /**
       * @return {number} The total number of nodes in the map.
       */
      count() {
          return this.root_.count();
      }
      /**
       * @return {?K} The minimum key in the map.
       */
      minKey() {
          return this.root_.minKey();
      }
      /**
       * @return {?K} The maximum key in the map.
       */
      maxKey() {
          return this.root_.maxKey();
      }
      /**
       * Traverses the map in key order and calls the specified action function
       * for each key/value pair.
       *
       * @param {function(!K, !V):*} action Callback function to be called
       * for each key/value pair.  If action returns true, traversal is aborted.
       * @return {*} The first truthy value returned by action, or the last falsey
       *   value returned by action
       */
      inorderTraversal(action) {
          return this.root_.inorderTraversal(action);
      }
      /**
       * Traverses the map in reverse key order and calls the specified action function
       * for each key/value pair.
       *
       * @param {function(!Object, !Object)} action Callback function to be called
       * for each key/value pair.  If action returns true, traversal is aborted.
       * @return {*} True if the traversal was aborted.
       */
      reverseTraversal(action) {
          return this.root_.reverseTraversal(action);
      }
      /**
       * Returns an iterator over the SortedMap.
       * @template T
       * @param {(function(K, V):T)=} resultGenerator
       * @return {SortedMapIterator.<K, V, T>} The iterator.
       */
      getIterator(resultGenerator) {
          return new SortedMapIterator(this.root_, null, this.comparator_, false, resultGenerator);
      }
      getIteratorFrom(key, resultGenerator) {
          return new SortedMapIterator(this.root_, key, this.comparator_, false, resultGenerator);
      }
      getReverseIteratorFrom(key, resultGenerator) {
          return new SortedMapIterator(this.root_, key, this.comparator_, true, resultGenerator);
      }
      getReverseIterator(resultGenerator) {
          return new SortedMapIterator(this.root_, null, this.comparator_, true, resultGenerator);
      }
  }
  /**
   * Always use the same empty node, to reduce memory.
   * @const
   */
  SortedMap.EMPTY_NODE = new LLRBEmptyNode();
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const LOG_2 = Math.log(2);
  /**
   * @constructor
   */
  class Base12Num {
      /**
       * @param {number} length
       */
      constructor(length) {
          const logBase2 = (num) => parseInt((Math.log(num) / LOG_2), 10);
          const bitMask = (bits) => parseInt(Array(bits + 1).join('1'), 2);
          this.count = logBase2(length + 1);
          this.current_ = this.count - 1;
          const mask = bitMask(this.count);
          this.bits_ = (length + 1) & mask;
      }
      /**
       * @return {boolean}
       */
      nextBitIsOne() {
          //noinspection JSBitwiseOperatorUsage
          const result = !(this.bits_ & (0x1 << this.current_));
          this.current_--;
          return result;
      }
  }
  /**
   * Takes a list of child nodes and constructs a SortedSet using the given comparison
   * function
   *
   * Uses the algorithm described in the paper linked here:
   * http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.46.1458
   *
   * @template K, V
   * @param {Array.<!NamedNode>} childList Unsorted list of children
   * @param {function(!NamedNode, !NamedNode):number} cmp The comparison method to be used
   * @param {(function(NamedNode):K)=} keyFn An optional function to extract K from a node wrapper, if K's
   *                                                        type is not NamedNode
   * @param {(function(K, K):number)=} mapSortFn An optional override for comparator used by the generated sorted map
   * @return {SortedMap.<K, V>}
   */
  const buildChildSet = function (childList, cmp, keyFn, mapSortFn) {
      childList.sort(cmp);
      const buildBalancedTree = function (low, high) {
          const length = high - low;
          let namedNode;
          let key;
          if (length == 0) {
              return null;
          }
          else if (length == 1) {
              namedNode = childList[low];
              key = keyFn ? keyFn(namedNode) : namedNode;
              return new LLRBNode(key, namedNode.node, LLRBNode.BLACK, null, null);
          }
          else {
              const middle = parseInt((length / 2), 10) + low;
              const left = buildBalancedTree(low, middle);
              const right = buildBalancedTree(middle + 1, high);
              namedNode = childList[middle];
              key = keyFn ? keyFn(namedNode) : namedNode;
              return new LLRBNode(key, namedNode.node, LLRBNode.BLACK, left, right);
          }
      };
      const buildFrom12Array = function (base12) {
          let node = null;
          let root = null;
          let index = childList.length;
          const buildPennant = function (chunkSize, color) {
              const low = index - chunkSize;
              const high = index;
              index -= chunkSize;
              const childTree = buildBalancedTree(low + 1, high);
              const namedNode = childList[low];
              const key = keyFn ? keyFn(namedNode) : namedNode;
              attachPennant(new LLRBNode(key, namedNode.node, color, null, childTree));
          };
          const attachPennant = function (pennant) {
              if (node) {
                  node.left = pennant;
                  node = pennant;
              }
              else {
                  root = pennant;
                  node = pennant;
              }
          };
          for (let i = 0; i < base12.count; ++i) {
              const isOne = base12.nextBitIsOne();
              // The number of nodes taken in each slice is 2^(arr.length - (i + 1))
              const chunkSize = Math.pow(2, base12.count - (i + 1));
              if (isOne) {
                  buildPennant(chunkSize, LLRBNode.BLACK);
              }
              else {
                  // current == 2
                  buildPennant(chunkSize, LLRBNode.BLACK);
                  buildPennant(chunkSize, LLRBNode.RED);
              }
          }
          return root;
      };
      const base12 = new Base12Num(childList.length);
      const root = buildFrom12Array(base12);
      return new SortedMap(mapSortFn || cmp, root);
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  let _defaultIndexMap;
  const fallbackObject = {};
  /**
   *
   * @param {Object.<string, FallbackType|SortedMap.<NamedNode, Node>>} indexes
   * @param {Object.<string, Index>} indexSet
   * @constructor
   */
  class IndexMap {
      constructor(indexes_, indexSet_) {
          this.indexes_ = indexes_;
          this.indexSet_ = indexSet_;
      }
      /**
       * The default IndexMap for nodes without a priority
       * @type {!IndexMap}
       * @const
       */
      static get Default() {
          assert(fallbackObject && PRIORITY_INDEX, 'ChildrenNode.ts has not been loaded');
          _defaultIndexMap =
              _defaultIndexMap ||
                  new IndexMap({ '.priority': fallbackObject }, { '.priority': PRIORITY_INDEX });
          return _defaultIndexMap;
      }
      /**
       *
       * @param {!string} indexKey
       * @return {?SortedMap.<NamedNode, Node>}
       */
      get(indexKey) {
          const sortedMap = safeGet(this.indexes_, indexKey);
          if (!sortedMap)
              throw new Error('No index defined for ' + indexKey);
          if (sortedMap === fallbackObject) {
              // The index exists, but it falls back to just name comparison. Return null so that the calling code uses the
              // regular child map
              return null;
          }
          else {
              return sortedMap;
          }
      }
      /**
       * @param {!Index} indexDefinition
       * @return {boolean}
       */
      hasIndex(indexDefinition) {
          return contains(this.indexSet_, indexDefinition.toString());
      }
      /**
       * @param {!Index} indexDefinition
       * @param {!SortedMap.<string, !Node>} existingChildren
       * @return {!IndexMap}
       */
      addIndex(indexDefinition, existingChildren) {
          assert(indexDefinition !== KEY_INDEX, "KeyIndex always exists and isn't meant to be added to the IndexMap.");
          const childList = [];
          let sawIndexedValue = false;
          const iter = existingChildren.getIterator(NamedNode.Wrap);
          let next = iter.getNext();
          while (next) {
              sawIndexedValue =
                  sawIndexedValue || indexDefinition.isDefinedOn(next.node);
              childList.push(next);
              next = iter.getNext();
          }
          let newIndex;
          if (sawIndexedValue) {
              newIndex = buildChildSet(childList, indexDefinition.getCompare());
          }
          else {
              newIndex = fallbackObject;
          }
          const indexName = indexDefinition.toString();
          const newIndexSet = clone(this.indexSet_);
          newIndexSet[indexName] = indexDefinition;
          const newIndexes = clone(this.indexes_);
          newIndexes[indexName] = newIndex;
          return new IndexMap(newIndexes, newIndexSet);
      }
      /**
       * Ensure that this node is properly tracked in any indexes that we're maintaining
       * @param {!NamedNode} namedNode
       * @param {!SortedMap.<string, !Node>} existingChildren
       * @return {!IndexMap}
       */
      addToIndexes(namedNode, existingChildren) {
          const newIndexes = map(this.indexes_, (indexedChildren, indexName) => {
              const index = safeGet(this.indexSet_, indexName);
              assert(index, 'Missing index implementation for ' + indexName);
              if (indexedChildren === fallbackObject) {
                  // Check to see if we need to index everything
                  if (index.isDefinedOn(namedNode.node)) {
                      // We need to build this index
                      const childList = [];
                      const iter = existingChildren.getIterator(NamedNode.Wrap);
                      let next = iter.getNext();
                      while (next) {
                          if (next.name != namedNode.name) {
                              childList.push(next);
                          }
                          next = iter.getNext();
                      }
                      childList.push(namedNode);
                      return buildChildSet(childList, index.getCompare());
                  }
                  else {
                      // No change, this remains a fallback
                      return fallbackObject;
                  }
              }
              else {
                  const existingSnap = existingChildren.get(namedNode.name);
                  let newChildren = indexedChildren;
                  if (existingSnap) {
                      newChildren = newChildren.remove(new NamedNode(namedNode.name, existingSnap));
                  }
                  return newChildren.insert(namedNode, namedNode.node);
              }
          });
          return new IndexMap(newIndexes, this.indexSet_);
      }
      /**
       * Create a new IndexMap instance with the given value removed
       * @param {!NamedNode} namedNode
       * @param {!SortedMap.<string, !Node>} existingChildren
       * @return {!IndexMap}
       */
      removeFromIndexes(namedNode, existingChildren) {
          const newIndexes = map(this.indexes_, function (indexedChildren) {
              if (indexedChildren === fallbackObject) {
                  // This is the fallback. Just return it, nothing to do in this case
                  return indexedChildren;
              }
              else {
                  const existingSnap = existingChildren.get(namedNode.name);
                  if (existingSnap) {
                      return indexedChildren.remove(new NamedNode(namedNode.name, existingSnap));
                  }
                  else {
                      // No record of this child
                      return indexedChildren;
                  }
              }
          });
          return new IndexMap(newIndexes, this.indexSet_);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  function NAME_ONLY_COMPARATOR(left, right) {
      return nameCompare(left.name, right.name);
  }
  function NAME_COMPARATOR(left, right) {
      return nameCompare(left, right);
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  // TODO: For memory savings, don't store priorityNode_ if it's empty.
  let EMPTY_NODE;
  /**
   * ChildrenNode is a class for storing internal nodes in a DataSnapshot
   * (i.e. nodes with children).  It implements Node and stores the
   * list of children in the children property, sorted by child name.
   *
   * @constructor
   * @implements {Node}
   */
  class ChildrenNode {
      /**
       *
       * @param {!SortedMap.<string, !Node>} children_ List of children
       * of this node..
       * @param {?Node} priorityNode_ The priority of this node (as a snapshot node).
       * @param {!IndexMap} indexMap_
       */
      constructor(children_, priorityNode_, indexMap_) {
          this.children_ = children_;
          this.priorityNode_ = priorityNode_;
          this.indexMap_ = indexMap_;
          this.lazyHash_ = null;
          /**
           * Note: The only reason we allow null priority is for EMPTY_NODE, since we can't use
           * EMPTY_NODE as the priority of EMPTY_NODE.  We might want to consider making EMPTY_NODE its own
           * class instead of an empty ChildrenNode.
           */
          if (this.priorityNode_) {
              validatePriorityNode(this.priorityNode_);
          }
          if (this.children_.isEmpty()) {
              assert(!this.priorityNode_ || this.priorityNode_.isEmpty(), 'An empty node cannot have a priority');
          }
      }
      static get EMPTY_NODE() {
          return (EMPTY_NODE ||
              (EMPTY_NODE = new ChildrenNode(new SortedMap(NAME_COMPARATOR), null, IndexMap.Default)));
      }
      /** @inheritDoc */
      isLeafNode() {
          return false;
      }
      /** @inheritDoc */
      getPriority() {
          return this.priorityNode_ || EMPTY_NODE;
      }
      /** @inheritDoc */
      updatePriority(newPriorityNode) {
          if (this.children_.isEmpty()) {
              // Don't allow priorities on empty nodes
              return this;
          }
          else {
              return new ChildrenNode(this.children_, newPriorityNode, this.indexMap_);
          }
      }
      /** @inheritDoc */
      getImmediateChild(childName) {
          // Hack to treat priority as a regular child
          if (childName === '.priority') {
              return this.getPriority();
          }
          else {
              const child = this.children_.get(childName);
              return child === null ? EMPTY_NODE : child;
          }
      }
      /** @inheritDoc */
      getChild(path) {
          const front = path.getFront();
          if (front === null)
              return this;
          return this.getImmediateChild(front).getChild(path.popFront());
      }
      /** @inheritDoc */
      hasChild(childName) {
          return this.children_.get(childName) !== null;
      }
      /** @inheritDoc */
      updateImmediateChild(childName, newChildNode) {
          assert(newChildNode, 'We should always be passing snapshot nodes');
          if (childName === '.priority') {
              return this.updatePriority(newChildNode);
          }
          else {
              const namedNode = new NamedNode(childName, newChildNode);
              let newChildren, newIndexMap, newPriority;
              if (newChildNode.isEmpty()) {
                  newChildren = this.children_.remove(childName);
                  newIndexMap = this.indexMap_.removeFromIndexes(namedNode, this.children_);
              }
              else {
                  newChildren = this.children_.insert(childName, newChildNode);
                  newIndexMap = this.indexMap_.addToIndexes(namedNode, this.children_);
              }
              newPriority = newChildren.isEmpty() ? EMPTY_NODE : this.priorityNode_;
              return new ChildrenNode(newChildren, newPriority, newIndexMap);
          }
      }
      /** @inheritDoc */
      updateChild(path, newChildNode) {
          const front = path.getFront();
          if (front === null) {
              return newChildNode;
          }
          else {
              assert(path.getFront() !== '.priority' || path.getLength() === 1, '.priority must be the last token in a path');
              const newImmediateChild = this.getImmediateChild(front).updateChild(path.popFront(), newChildNode);
              return this.updateImmediateChild(front, newImmediateChild);
          }
      }
      /** @inheritDoc */
      isEmpty() {
          return this.children_.isEmpty();
      }
      /** @inheritDoc */
      numChildren() {
          return this.children_.count();
      }
      /** @inheritDoc */
      val(exportFormat) {
          if (this.isEmpty())
              return null;
          const obj = {};
          let numKeys = 0, maxKey = 0, allIntegerKeys = true;
          this.forEachChild(PRIORITY_INDEX, function (key, childNode) {
              obj[key] = childNode.val(exportFormat);
              numKeys++;
              if (allIntegerKeys && ChildrenNode.INTEGER_REGEXP_.test(key)) {
                  maxKey = Math.max(maxKey, Number(key));
              }
              else {
                  allIntegerKeys = false;
              }
          });
          if (!exportFormat && allIntegerKeys && maxKey < 2 * numKeys) {
              // convert to array.
              const array = [];
              for (let key in obj)
                  array[key] = obj[key];
              return array;
          }
          else {
              if (exportFormat && !this.getPriority().isEmpty()) {
                  obj['.priority'] = this.getPriority().val();
              }
              return obj;
          }
      }
      /** @inheritDoc */
      hash() {
          if (this.lazyHash_ === null) {
              let toHash = '';
              if (!this.getPriority().isEmpty())
                  toHash +=
                      'priority:' +
                          priorityHashText(this.getPriority().val()) +
                          ':';
              this.forEachChild(PRIORITY_INDEX, function (key, childNode) {
                  const childHash = childNode.hash();
                  if (childHash !== '')
                      toHash += ':' + key + ':' + childHash;
              });
              this.lazyHash_ = toHash === '' ? '' : sha1(toHash);
          }
          return this.lazyHash_;
      }
      /** @inheritDoc */
      getPredecessorChildName(childName, childNode, index) {
          const idx = this.resolveIndex_(index);
          if (idx) {
              const predecessor = idx.getPredecessorKey(new NamedNode(childName, childNode));
              return predecessor ? predecessor.name : null;
          }
          else {
              return this.children_.getPredecessorKey(childName);
          }
      }
      /**
       * @param {!Index} indexDefinition
       * @return {?string}
       */
      getFirstChildName(indexDefinition) {
          const idx = this.resolveIndex_(indexDefinition);
          if (idx) {
              const minKey = idx.minKey();
              return minKey && minKey.name;
          }
          else {
              return this.children_.minKey();
          }
      }
      /**
       * @param {!Index} indexDefinition
       * @return {?NamedNode}
       */
      getFirstChild(indexDefinition) {
          const minKey = this.getFirstChildName(indexDefinition);
          if (minKey) {
              return new NamedNode(minKey, this.children_.get(minKey));
          }
          else {
              return null;
          }
      }
      /**
       * Given an index, return the key name of the largest value we have, according to that index
       * @param {!Index} indexDefinition
       * @return {?string}
       */
      getLastChildName(indexDefinition) {
          const idx = this.resolveIndex_(indexDefinition);
          if (idx) {
              const maxKey = idx.maxKey();
              return maxKey && maxKey.name;
          }
          else {
              return this.children_.maxKey();
          }
      }
      /**
       * @param {!Index} indexDefinition
       * @return {?NamedNode}
       */
      getLastChild(indexDefinition) {
          const maxKey = this.getLastChildName(indexDefinition);
          if (maxKey) {
              return new NamedNode(maxKey, this.children_.get(maxKey));
          }
          else {
              return null;
          }
      }
      /**
       * @inheritDoc
       */
      forEachChild(index, action) {
          const idx = this.resolveIndex_(index);
          if (idx) {
              return idx.inorderTraversal(function (wrappedNode) {
                  return action(wrappedNode.name, wrappedNode.node);
              });
          }
          else {
              return this.children_.inorderTraversal(action);
          }
      }
      /**
       * @param {!Index} indexDefinition
       * @return {SortedMapIterator}
       */
      getIterator(indexDefinition) {
          return this.getIteratorFrom(indexDefinition.minPost(), indexDefinition);
      }
      /**
       *
       * @param {!NamedNode} startPost
       * @param {!Index} indexDefinition
       * @return {!SortedMapIterator}
       */
      getIteratorFrom(startPost, indexDefinition) {
          const idx = this.resolveIndex_(indexDefinition);
          if (idx) {
              return idx.getIteratorFrom(startPost, key => key);
          }
          else {
              const iterator = this.children_.getIteratorFrom(startPost.name, NamedNode.Wrap);
              let next = iterator.peek();
              while (next != null && indexDefinition.compare(next, startPost) < 0) {
                  iterator.getNext();
                  next = iterator.peek();
              }
              return iterator;
          }
      }
      /**
       * @param {!Index} indexDefinition
       * @return {!SortedMapIterator}
       */
      getReverseIterator(indexDefinition) {
          return this.getReverseIteratorFrom(indexDefinition.maxPost(), indexDefinition);
      }
      /**
       * @param {!NamedNode} endPost
       * @param {!Index} indexDefinition
       * @return {!SortedMapIterator}
       */
      getReverseIteratorFrom(endPost, indexDefinition) {
          const idx = this.resolveIndex_(indexDefinition);
          if (idx) {
              return idx.getReverseIteratorFrom(endPost, function (key) {
                  return key;
              });
          }
          else {
              const iterator = this.children_.getReverseIteratorFrom(endPost.name, NamedNode.Wrap);
              let next = iterator.peek();
              while (next != null && indexDefinition.compare(next, endPost) > 0) {
                  iterator.getNext();
                  next = iterator.peek();
              }
              return iterator;
          }
      }
      /**
       * @inheritDoc
       */
      compareTo(other) {
          if (this.isEmpty()) {
              if (other.isEmpty()) {
                  return 0;
              }
              else {
                  return -1;
              }
          }
          else if (other.isLeafNode() || other.isEmpty()) {
              return 1;
          }
          else if (other === MAX_NODE$2) {
              return -1;
          }
          else {
              // Must be another node with children.
              return 0;
          }
      }
      /**
       * @inheritDoc
       */
      withIndex(indexDefinition) {
          if (indexDefinition === KEY_INDEX ||
              this.indexMap_.hasIndex(indexDefinition)) {
              return this;
          }
          else {
              const newIndexMap = this.indexMap_.addIndex(indexDefinition, this.children_);
              return new ChildrenNode(this.children_, this.priorityNode_, newIndexMap);
          }
      }
      /**
       * @inheritDoc
       */
      isIndexed(index) {
          return index === KEY_INDEX || this.indexMap_.hasIndex(index);
      }
      /**
       * @inheritDoc
       */
      equals(other) {
          if (other === this) {
              return true;
          }
          else if (other.isLeafNode()) {
              return false;
          }
          else {
              const otherChildrenNode = other;
              if (!this.getPriority().equals(otherChildrenNode.getPriority())) {
                  return false;
              }
              else if (this.children_.count() === otherChildrenNode.children_.count()) {
                  const thisIter = this.getIterator(PRIORITY_INDEX);
                  const otherIter = otherChildrenNode.getIterator(PRIORITY_INDEX);
                  let thisCurrent = thisIter.getNext();
                  let otherCurrent = otherIter.getNext();
                  while (thisCurrent && otherCurrent) {
                      if (thisCurrent.name !== otherCurrent.name ||
                          !thisCurrent.node.equals(otherCurrent.node)) {
                          return false;
                      }
                      thisCurrent = thisIter.getNext();
                      otherCurrent = otherIter.getNext();
                  }
                  return thisCurrent === null && otherCurrent === null;
              }
              else {
                  return false;
              }
          }
      }
      /**
       * Returns a SortedMap ordered by index, or null if the default (by-key) ordering can be used
       * instead.
       *
       * @private
       * @param {!Index} indexDefinition
       * @return {?SortedMap.<NamedNode, Node>}
       */
      resolveIndex_(indexDefinition) {
          if (indexDefinition === KEY_INDEX) {
              return null;
          }
          else {
              return this.indexMap_.get(indexDefinition.toString());
          }
      }
  }
  /**
   * @private
   * @type {RegExp}
   */
  ChildrenNode.INTEGER_REGEXP_ = /^(0|[1-9]\d*)$/;
  /**
   * @constructor
   * @extends {ChildrenNode}
   * @private
   */
  class MaxNode extends ChildrenNode {
      constructor() {
          super(new SortedMap(NAME_COMPARATOR), ChildrenNode.EMPTY_NODE, IndexMap.Default);
      }
      compareTo(other) {
          if (other === this) {
              return 0;
          }
          else {
              return 1;
          }
      }
      equals(other) {
          // Not that we every compare it, but MAX_NODE is only ever equal to itself
          return other === this;
      }
      getPriority() {
          return this;
      }
      getImmediateChild(childName) {
          return ChildrenNode.EMPTY_NODE;
      }
      isEmpty() {
          return false;
      }
  }
  /**
   * Marker that will sort higher than any other snapshot.
   * @type {!MAX_NODE}
   * @const
   */
  const MAX_NODE$2 = new MaxNode();
  Object.defineProperties(NamedNode, {
      MIN: {
          value: new NamedNode(MIN_NAME, ChildrenNode.EMPTY_NODE)
      },
      MAX: {
          value: new NamedNode(MAX_NAME, MAX_NODE$2)
      }
  });
  /**
   * Reference Extensions
   */
  KeyIndex.__EMPTY_NODE = ChildrenNode.EMPTY_NODE;
  LeafNode.__childrenNodeConstructor = ChildrenNode;
  setMaxNode(MAX_NODE$2);
  setMaxNode$1(MAX_NODE$2);
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const USE_HINZE = true;
  /**
   * Constructs a snapshot node representing the passed JSON and returns it.
   * @param {*} json JSON to create a node for.
   * @param {?string|?number=} priority Optional priority to use.  This will be ignored if the
   * passed JSON contains a .priority property.
   * @return {!Node}
   */
  function nodeFromJSON$1(json, priority = null) {
      if (json === null) {
          return ChildrenNode.EMPTY_NODE;
      }
      if (typeof json === 'object' && '.priority' in json) {
          priority = json['.priority'];
      }
      assert(priority === null ||
          typeof priority === 'string' ||
          typeof priority === 'number' ||
          (typeof priority === 'object' && '.sv' in priority), 'Invalid priority type found: ' + typeof priority);
      if (typeof json === 'object' && '.value' in json && json['.value'] !== null) {
          json = json['.value'];
      }
      // Valid leaf nodes include non-objects or server-value wrapper objects
      if (typeof json !== 'object' || '.sv' in json) {
          const jsonLeaf = json;
          return new LeafNode(jsonLeaf, nodeFromJSON$1(priority));
      }
      if (!(json instanceof Array) && USE_HINZE) {
          const children = [];
          let childrenHavePriority = false;
          const hinzeJsonObj = json;
          forEach(hinzeJsonObj, (key, child) => {
              if (typeof key !== 'string' || key.substring(0, 1) !== '.') {
                  // Ignore metadata nodes
                  const childNode = nodeFromJSON$1(hinzeJsonObj[key]);
                  if (!childNode.isEmpty()) {
                      childrenHavePriority =
                          childrenHavePriority || !childNode.getPriority().isEmpty();
                      children.push(new NamedNode(key, childNode));
                  }
              }
          });
          if (children.length == 0) {
              return ChildrenNode.EMPTY_NODE;
          }
          const childSet = buildChildSet(children, NAME_ONLY_COMPARATOR, namedNode => namedNode.name, NAME_COMPARATOR);
          if (childrenHavePriority) {
              const sortedChildSet = buildChildSet(children, PRIORITY_INDEX.getCompare());
              return new ChildrenNode(childSet, nodeFromJSON$1(priority), new IndexMap({ '.priority': sortedChildSet }, { '.priority': PRIORITY_INDEX }));
          }
          else {
              return new ChildrenNode(childSet, nodeFromJSON$1(priority), IndexMap.Default);
          }
      }
      else {
          let node = ChildrenNode.EMPTY_NODE;
          const jsonObj = json;
          forEach(jsonObj, (key, childData) => {
              if (contains(jsonObj, key)) {
                  if (key.substring(0, 1) !== '.') {
                      // ignore metadata nodes.
                      const childNode = nodeFromJSON$1(childData);
                      if (childNode.isLeafNode() || !childNode.isEmpty())
                          node = node.updateImmediateChild(key, childNode);
                  }
              }
          });
          return node.updatePriority(nodeFromJSON$1(priority));
      }
  }
  setNodeFromJSON(nodeFromJSON$1);
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @constructor
   * @extends {Index}
   * @private
   */
  class ValueIndex extends Index {
      /**
       * @inheritDoc
       */
      compare(a, b) {
          const indexCmp = a.node.compareTo(b.node);
          if (indexCmp === 0) {
              return nameCompare(a.name, b.name);
          }
          else {
              return indexCmp;
          }
      }
      /**
       * @inheritDoc
       */
      isDefinedOn(node) {
          return true;
      }
      /**
       * @inheritDoc
       */
      indexedValueChanged(oldNode, newNode) {
          return !oldNode.equals(newNode);
      }
      /**
       * @inheritDoc
       */
      minPost() {
          return NamedNode.MIN;
      }
      /**
       * @inheritDoc
       */
      maxPost() {
          return NamedNode.MAX;
      }
      /**
       * @param {*} indexValue
       * @param {string} name
       * @return {!NamedNode}
       */
      makePost(indexValue, name) {
          const valueNode = nodeFromJSON$1(indexValue);
          return new NamedNode(name, valueNode);
      }
      /**
       * @return {!string} String representation for inclusion in a query spec
       */
      toString() {
          return '.value';
      }
  }
  const VALUE_INDEX = new ValueIndex();
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @param {!Path} indexPath
   * @constructor
   * @extends {Index}
   */
  class PathIndex extends Index {
      constructor(indexPath_) {
          super();
          this.indexPath_ = indexPath_;
          assert(!indexPath_.isEmpty() && indexPath_.getFront() !== '.priority', "Can't create PathIndex with empty path or .priority key");
      }
      /**
       * @param {!Node} snap
       * @return {!Node}
       * @protected
       */
      extractChild(snap) {
          return snap.getChild(this.indexPath_);
      }
      /**
       * @inheritDoc
       */
      isDefinedOn(node) {
          return !node.getChild(this.indexPath_).isEmpty();
      }
      /**
       * @inheritDoc
       */
      compare(a, b) {
          const aChild = this.extractChild(a.node);
          const bChild = this.extractChild(b.node);
          const indexCmp = aChild.compareTo(bChild);
          if (indexCmp === 0) {
              return nameCompare(a.name, b.name);
          }
          else {
              return indexCmp;
          }
      }
      /**
       * @inheritDoc
       */
      makePost(indexValue, name) {
          const valueNode = nodeFromJSON$1(indexValue);
          const node = ChildrenNode.EMPTY_NODE.updateChild(this.indexPath_, valueNode);
          return new NamedNode(name, node);
      }
      /**
       * @inheritDoc
       */
      maxPost() {
          const node = ChildrenNode.EMPTY_NODE.updateChild(this.indexPath_, MAX_NODE$2);
          return new NamedNode(MAX_NAME, node);
      }
      /**
       * @inheritDoc
       */
      toString() {
          return this.indexPath_.slice().join('/');
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Class representing a firebase data snapshot.  It wraps a SnapshotNode and
   * surfaces the public methods (val, forEach, etc.) we want to expose.
   */
  class DataSnapshot {
      /**
       * @param {!Node} node_ A SnapshotNode to wrap.
       * @param {!Reference} ref_ The ref of the location this snapshot came from.
       * @param {!Index} index_ The iteration order for this snapshot
       */
      constructor(node_, ref_, index_) {
          this.node_ = node_;
          this.ref_ = ref_;
          this.index_ = index_;
      }
      /**
       * Retrieves the snapshot contents as JSON.  Returns null if the snapshot is
       * empty.
       *
       * @return {*} JSON representation of the DataSnapshot contents, or null if empty.
       */
      val() {
          validateArgCount('DataSnapshot.val', 0, 0, arguments.length);
          return this.node_.val();
      }
      /**
       * Returns the snapshot contents as JSON, including priorities of node.  Suitable for exporting
       * the entire node contents.
       * @return {*} JSON representation of the DataSnapshot contents, or null if empty.
       */
      exportVal() {
          validateArgCount('DataSnapshot.exportVal', 0, 0, arguments.length);
          return this.node_.val(true);
      }
      // Do not create public documentation. This is intended to make JSON serialization work but is otherwise unnecessary
      // for end-users
      toJSON() {
          // Optional spacer argument is unnecessary because we're depending on recursion rather than stringifying the content
          validateArgCount('DataSnapshot.toJSON', 0, 1, arguments.length);
          return this.exportVal();
      }
      /**
       * Returns whether the snapshot contains a non-null value.
       *
       * @return {boolean} Whether the snapshot contains a non-null value, or is empty.
       */
      exists() {
          validateArgCount('DataSnapshot.exists', 0, 0, arguments.length);
          return !this.node_.isEmpty();
      }
      /**
       * Returns a DataSnapshot of the specified child node's contents.
       *
       * @param {!string} childPathString Path to a child.
       * @return {!DataSnapshot} DataSnapshot for child node.
       */
      child(childPathString) {
          validateArgCount('DataSnapshot.child', 0, 1, arguments.length);
          // Ensure the childPath is a string (can be a number)
          childPathString = String(childPathString);
          validatePathString('DataSnapshot.child', 1, childPathString, false);
          const childPath = new Path(childPathString);
          const childRef = this.ref_.child(childPath);
          return new DataSnapshot(this.node_.getChild(childPath), childRef, PRIORITY_INDEX);
      }
      /**
       * Returns whether the snapshot contains a child at the specified path.
       *
       * @param {!string} childPathString Path to a child.
       * @return {boolean} Whether the child exists.
       */
      hasChild(childPathString) {
          validateArgCount('DataSnapshot.hasChild', 1, 1, arguments.length);
          validatePathString('DataSnapshot.hasChild', 1, childPathString, false);
          const childPath = new Path(childPathString);
          return !this.node_.getChild(childPath).isEmpty();
      }
      /**
       * Returns the priority of the object, or null if no priority was set.
       *
       * @return {string|number|null} The priority.
       */
      getPriority() {
          validateArgCount('DataSnapshot.getPriority', 0, 0, arguments.length);
          // typecast here because we never return deferred values or internal priorities (MAX_PRIORITY)
          return this.node_.getPriority().val();
      }
      /**
       * Iterates through child nodes and calls the specified action for each one.
       *
       * @param {function(!DataSnapshot)} action Callback function to be called
       * for each child.
       * @return {boolean} True if forEach was canceled by action returning true for
       * one of the child nodes.
       */
      forEach(action) {
          validateArgCount('DataSnapshot.forEach', 1, 1, arguments.length);
          validateCallback('DataSnapshot.forEach', 1, action, false);
          if (this.node_.isLeafNode())
              return false;
          const childrenNode = this.node_;
          // Sanitize the return value to a boolean. ChildrenNode.forEachChild has a weird return type...
          return !!childrenNode.forEachChild(this.index_, (key, node) => {
              return action(new DataSnapshot(node, this.ref_.child(key), PRIORITY_INDEX));
          });
      }
      /**
       * Returns whether this DataSnapshot has children.
       * @return {boolean} True if the DataSnapshot contains 1 or more child nodes.
       */
      hasChildren() {
          validateArgCount('DataSnapshot.hasChildren', 0, 0, arguments.length);
          if (this.node_.isLeafNode())
              return false;
          else
              return !this.node_.isEmpty();
      }
      get key() {
          return this.ref_.getKey();
      }
      /**
       * Returns the number of children for this DataSnapshot.
       * @return {number} The number of children that this DataSnapshot contains.
       */
      numChildren() {
          validateArgCount('DataSnapshot.numChildren', 0, 0, arguments.length);
          return this.node_.numChildren();
      }
      /**
       * @return {Reference} The Firebase reference for the location this snapshot's data came from.
       */
      getRef() {
          validateArgCount('DataSnapshot.ref', 0, 0, arguments.length);
          return this.ref_;
      }
      get ref() {
          return this.getRef();
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Encapsulates the data needed to raise an event
   * @implements {Event}
   */
  class DataEvent {
      /**
       * @param {!string} eventType One of: value, child_added, child_changed, child_moved, child_removed
       * @param {!EventRegistration} eventRegistration The function to call to with the event data. User provided
       * @param {!DataSnapshot} snapshot The data backing the event
       * @param {?string=} prevName Optional, the name of the previous child for child_* events.
       */
      constructor(eventType, eventRegistration, snapshot, prevName) {
          this.eventType = eventType;
          this.eventRegistration = eventRegistration;
          this.snapshot = snapshot;
          this.prevName = prevName;
      }
      /**
       * @inheritDoc
       */
      getPath() {
          const ref = this.snapshot.getRef();
          if (this.eventType === 'value') {
              return ref.path;
          }
          else {
              return ref.getParent().path;
          }
      }
      /**
       * @inheritDoc
       */
      getEventType() {
          return this.eventType;
      }
      /**
       * @inheritDoc
       */
      getEventRunner() {
          return this.eventRegistration.getEventRunner(this);
      }
      /**
       * @inheritDoc
       */
      toString() {
          return (this.getPath().toString() +
              ':' +
              this.eventType +
              ':' +
              stringify(this.snapshot.exportVal()));
      }
  }
  class CancelEvent {
      /**
       * @param {EventRegistration} eventRegistration
       * @param {Error} error
       * @param {!Path} path
       */
      constructor(eventRegistration, error, path) {
          this.eventRegistration = eventRegistration;
          this.error = error;
          this.path = path;
      }
      /**
       * @inheritDoc
       */
      getPath() {
          return this.path;
      }
      /**
       * @inheritDoc
       */
      getEventType() {
          return 'cancel';
      }
      /**
       * @inheritDoc
       */
      getEventRunner() {
          return this.eventRegistration.getEventRunner(this);
      }
      /**
       * @inheritDoc
       */
      toString() {
          return this.path.toString() + ':cancel';
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Represents registration for 'value' events.
   */
  class ValueEventRegistration {
      /**
       * @param {?function(!DataSnapshot)} callback_
       * @param {?function(Error)} cancelCallback_
       * @param {?Object} context_
       */
      constructor(callback_, cancelCallback_, context_) {
          this.callback_ = callback_;
          this.cancelCallback_ = cancelCallback_;
          this.context_ = context_;
      }
      /**
       * @inheritDoc
       */
      respondsTo(eventType) {
          return eventType === 'value';
      }
      /**
       * @inheritDoc
       */
      createEvent(change, query) {
          const index = query.getQueryParams().getIndex();
          return new DataEvent('value', this, new DataSnapshot(change.snapshotNode, query.getRef(), index));
      }
      /**
       * @inheritDoc
       */
      getEventRunner(eventData) {
          const ctx = this.context_;
          if (eventData.getEventType() === 'cancel') {
              assert(this.cancelCallback_, 'Raising a cancel event on a listener with no cancel callback');
              const cancelCB = this.cancelCallback_;
              return function () {
                  // We know that error exists, we checked above that this is a cancel event
                  cancelCB.call(ctx, eventData.error);
              };
          }
          else {
              const cb = this.callback_;
              return function () {
                  cb.call(ctx, eventData.snapshot);
              };
          }
      }
      /**
       * @inheritDoc
       */
      createCancelEvent(error, path) {
          if (this.cancelCallback_) {
              return new CancelEvent(this, error, path);
          }
          else {
              return null;
          }
      }
      /**
       * @inheritDoc
       */
      matches(other) {
          if (!(other instanceof ValueEventRegistration)) {
              return false;
          }
          else if (!other.callback_ || !this.callback_) {
              // If no callback specified, we consider it to match any callback.
              return true;
          }
          else {
              return (other.callback_ === this.callback_ && other.context_ === this.context_);
          }
      }
      /**
       * @inheritDoc
       */
      hasAnyCallback() {
          return this.callback_ !== null;
      }
  }
  /**
   * Represents the registration of 1 or more child_xxx events.
   *
   * Currently, it is always exactly 1 child_xxx event, but the idea is we might let you
   * register a group of callbacks together in the future.
   *
   * @constructor
   * @implements {EventRegistration}
   */
  class ChildEventRegistration {
      /**
       * @param {?Object.<string, function(!DataSnapshot, ?string=)>} callbacks_
       * @param {?function(Error)} cancelCallback_
       * @param {Object=} context_
       */
      constructor(callbacks_, cancelCallback_, context_) {
          this.callbacks_ = callbacks_;
          this.cancelCallback_ = cancelCallback_;
          this.context_ = context_;
      }
      /**
       * @inheritDoc
       */
      respondsTo(eventType) {
          let eventToCheck = eventType === 'children_added' ? 'child_added' : eventType;
          eventToCheck =
              eventToCheck === 'children_removed' ? 'child_removed' : eventToCheck;
          return contains(this.callbacks_, eventToCheck);
      }
      /**
       * @inheritDoc
       */
      createCancelEvent(error, path) {
          if (this.cancelCallback_) {
              return new CancelEvent(this, error, path);
          }
          else {
              return null;
          }
      }
      /**
       * @inheritDoc
       */
      createEvent(change, query) {
          assert(change.childName != null, 'Child events should have a childName.');
          const ref = query.getRef().child(/** @type {!string} */ (change.childName));
          const index = query.getQueryParams().getIndex();
          return new DataEvent(change.type, this, new DataSnapshot(change.snapshotNode, ref, index), change.prevName);
      }
      /**
       * @inheritDoc
       */
      getEventRunner(eventData) {
          const ctx = this.context_;
          if (eventData.getEventType() === 'cancel') {
              assert(this.cancelCallback_, 'Raising a cancel event on a listener with no cancel callback');
              const cancelCB = this.cancelCallback_;
              return function () {
                  // We know that error exists, we checked above that this is a cancel event
                  cancelCB.call(ctx, eventData.error);
              };
          }
          else {
              const cb = this.callbacks_[eventData.eventType];
              return function () {
                  cb.call(ctx, eventData.snapshot, eventData.prevName);
              };
          }
      }
      /**
       * @inheritDoc
       */
      matches(other) {
          if (other instanceof ChildEventRegistration) {
              if (!this.callbacks_ || !other.callbacks_) {
                  return true;
              }
              else if (this.context_ === other.context_) {
                  const otherCount = getCount(other.callbacks_);
                  const thisCount = getCount(this.callbacks_);
                  if (otherCount === thisCount) {
                      // If count is 1, do an exact match on eventType, if either is defined but null, it's a match.
                      //  If event types don't match, not a match
                      // If count is not 1, exact match across all
                      if (otherCount === 1) {
                          const otherKey /** @type {!string} */ = getAnyKey(other.callbacks_);
                          const thisKey /** @type {!string} */ = getAnyKey(this.callbacks_);
                          return (thisKey === otherKey &&
                              (!other.callbacks_[otherKey] ||
                                  !this.callbacks_[thisKey] ||
                                  other.callbacks_[otherKey] === this.callbacks_[thisKey]));
                      }
                      else {
                          // Exact match on each key.
                          return every(this.callbacks_, (eventType, cb) => other.callbacks_[eventType] === cb);
                      }
                  }
              }
          }
          return false;
      }
      /**
       * @inheritDoc
       */
      hasAnyCallback() {
          return this.callbacks_ !== null;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  let __referenceConstructor;
  /**
   * A Query represents a filter to be applied to a firebase location.  This object purely represents the
   * query expression (and exposes our public API to build the query).  The actual query logic is in ViewBase.js.
   *
   * Since every Firebase reference is a query, Firebase inherits from this object.
   */
  class Query {
      constructor(repo, path, queryParams_, orderByCalled_) {
          this.repo = repo;
          this.path = path;
          this.queryParams_ = queryParams_;
          this.orderByCalled_ = orderByCalled_;
      }
      static set __referenceConstructor(val) {
          __referenceConstructor = val;
      }
      static get __referenceConstructor() {
          assert(__referenceConstructor, 'Reference.ts has not been loaded');
          return __referenceConstructor;
      }
      /**
       * Validates start/end values for queries.
       * @param {!QueryParams} params
       * @private
       */
      static validateQueryEndpoints_(params) {
          let startNode = null;
          let endNode = null;
          if (params.hasStart()) {
              startNode = params.getIndexStartValue();
          }
          if (params.hasEnd()) {
              endNode = params.getIndexEndValue();
          }
          if (params.getIndex() === KEY_INDEX) {
              const tooManyArgsError = 'Query: When ordering by key, you may only pass one argument to ' +
                  'startAt(), endAt(), or equalTo().';
              const wrongArgTypeError = 'Query: When ordering by key, the argument passed to startAt(), endAt(),' +
                  'or equalTo() must be a string.';
              if (params.hasStart()) {
                  const startName = params.getIndexStartName();
                  if (startName != MIN_NAME) {
                      throw new Error(tooManyArgsError);
                  }
                  else if (typeof startNode !== 'string') {
                      throw new Error(wrongArgTypeError);
                  }
              }
              if (params.hasEnd()) {
                  const endName = params.getIndexEndName();
                  if (endName != MAX_NAME) {
                      throw new Error(tooManyArgsError);
                  }
                  else if (typeof endNode !== 'string') {
                      throw new Error(wrongArgTypeError);
                  }
              }
          }
          else if (params.getIndex() === PRIORITY_INDEX) {
              if ((startNode != null && !isValidPriority(startNode)) ||
                  (endNode != null && !isValidPriority(endNode))) {
                  throw new Error('Query: When ordering by priority, the first argument passed to startAt(), ' +
                      'endAt(), or equalTo() must be a valid priority value (null, a number, or a string).');
              }
          }
          else {
              assert(params.getIndex() instanceof PathIndex ||
                  params.getIndex() === VALUE_INDEX, 'unknown index type.');
              if ((startNode != null && typeof startNode === 'object') ||
                  (endNode != null && typeof endNode === 'object')) {
                  throw new Error('Query: First argument passed to startAt(), endAt(), or equalTo() cannot be ' +
                      'an object.');
              }
          }
      }
      /**
       * Validates that limit* has been called with the correct combination of parameters
       * @param {!QueryParams} params
       * @private
       */
      static validateLimit_(params) {
          if (params.hasStart() &&
              params.hasEnd() &&
              params.hasLimit() &&
              !params.hasAnchoredLimit()) {
              throw new Error("Query: Can't combine startAt(), endAt(), and limit(). Use limitToFirst() or limitToLast() instead.");
          }
      }
      /**
       * Validates that no other order by call has been made
       * @param {!string} fnName
       * @private
       */
      validateNoPreviousOrderByCall_(fnName) {
          if (this.orderByCalled_ === true) {
              throw new Error(fnName + ": You can't combine multiple orderBy calls.");
          }
      }
      /**
       * @return {!QueryParams}
       */
      getQueryParams() {
          return this.queryParams_;
      }
      /**
       * @return {!Reference}
       */
      getRef() {
          validateArgCount('Query.ref', 0, 0, arguments.length);
          // This is a slight hack. We cannot goog.require('fb.api.Firebase'), since Firebase requires fb.api.Query.
          // However, we will always export 'Firebase' to the global namespace, so it's guaranteed to exist by the time this
          // method gets called.
          return new Query.__referenceConstructor(this.repo, this.path);
      }
      /**
       * @param {!string} eventType
       * @param {!function(DataSnapshot, string=)} callback
       * @param {(function(Error)|Object)=} cancelCallbackOrContext
       * @param {Object=} context
       * @return {!function(DataSnapshot, string=)}
       */
      on(eventType, callback, cancelCallbackOrContext, context) {
          validateArgCount('Query.on', 2, 4, arguments.length);
          validateEventType('Query.on', 1, eventType, false);
          validateCallback('Query.on', 2, callback, false);
          const ret = Query.getCancelAndContextArgs_('Query.on', cancelCallbackOrContext, context);
          if (eventType === 'value') {
              this.onValueEvent(callback, ret.cancel, ret.context);
          }
          else {
              const callbacks = {};
              callbacks[eventType] = callback;
              this.onChildEvent(callbacks, ret.cancel, ret.context);
          }
          return callback;
      }
      /**
       * @param {!function(!DataSnapshot)} callback
       * @param {?function(Error)} cancelCallback
       * @param {?Object} context
       * @protected
       */
      onValueEvent(callback, cancelCallback, context) {
          const container = new ValueEventRegistration(callback, cancelCallback || null, context || null);
          this.repo.addEventCallbackForQuery(this, container);
      }
      /**
       * @param {!Object.<string, !function(!DataSnapshot, ?string)>} callbacks
       * @param {?function(Error)} cancelCallback
       * @param {?Object} context
       * @protected
       */
      onChildEvent(callbacks, cancelCallback, context) {
          const container = new ChildEventRegistration(callbacks, cancelCallback, context);
          this.repo.addEventCallbackForQuery(this, container);
      }
      /**
       * @param {string=} eventType
       * @param {(function(!DataSnapshot, ?string=))=} callback
       * @param {Object=} context
       */
      off(eventType, callback, context) {
          validateArgCount('Query.off', 0, 3, arguments.length);
          validateEventType('Query.off', 1, eventType, true);
          validateCallback('Query.off', 2, callback, true);
          validateContextObject('Query.off', 3, context, true);
          let container = null;
          let callbacks = null;
          if (eventType === 'value') {
              const valueCallback = callback || null;
              container = new ValueEventRegistration(valueCallback, null, context || null);
          }
          else if (eventType) {
              if (callback) {
                  callbacks = {};
                  callbacks[eventType] = callback;
              }
              container = new ChildEventRegistration(callbacks, null, context || null);
          }
          this.repo.removeEventCallbackForQuery(this, container);
      }
      /**
       * Attaches a listener, waits for the first event, and then removes the listener
       * @param {!string} eventType
       * @param {!function(!DataSnapshot, string=)} userCallback
       * @param failureCallbackOrContext
       * @param context
       * @return {!firebase.Promise}
       */
      once(eventType, userCallback, failureCallbackOrContext, context) {
          validateArgCount('Query.once', 1, 4, arguments.length);
          validateEventType('Query.once', 1, eventType, false);
          validateCallback('Query.once', 2, userCallback, true);
          const ret = Query.getCancelAndContextArgs_('Query.once', failureCallbackOrContext, context);
          // TODO: Implement this more efficiently (in particular, use 'get' wire protocol for 'value' event)
          // TODO: consider actually wiring the callbacks into the promise. We cannot do this without a breaking change
          // because the API currently expects callbacks will be called synchronously if the data is cached, but this is
          // against the Promise specification.
          let firstCall = true;
          const deferred = new Deferred();
          // A dummy error handler in case a user wasn't expecting promises
          deferred.promise.catch(() => { });
          const onceCallback = (snapshot) => {
              // NOTE: Even though we unsubscribe, we may get called multiple times if a single action (e.g. set() with JSON)
              // triggers multiple events (e.g. child_added or child_changed).
              if (firstCall) {
                  firstCall = false;
                  this.off(eventType, onceCallback);
                  if (userCallback) {
                      userCallback.bind(ret.context)(snapshot);
                  }
                  deferred.resolve(snapshot);
              }
          };
          this.on(eventType, onceCallback, 
          /*cancel=*/ err => {
              this.off(eventType, onceCallback);
              if (ret.cancel)
                  ret.cancel.bind(ret.context)(err);
              deferred.reject(err);
          });
          return deferred.promise;
      }
      /**
       * Set a limit and anchor it to the start of the window.
       * @param {!number} limit
       * @return {!Query}
       */
      limitToFirst(limit) {
          validateArgCount('Query.limitToFirst', 1, 1, arguments.length);
          if (typeof limit !== 'number' ||
              Math.floor(limit) !== limit ||
              limit <= 0) {
              throw new Error('Query.limitToFirst: First argument must be a positive integer.');
          }
          if (this.queryParams_.hasLimit()) {
              throw new Error('Query.limitToFirst: Limit was already set (by another call to limit, ' +
                  'limitToFirst, or limitToLast).');
          }
          return new Query(this.repo, this.path, this.queryParams_.limitToFirst(limit), this.orderByCalled_);
      }
      /**
       * Set a limit and anchor it to the end of the window.
       * @param {!number} limit
       * @return {!Query}
       */
      limitToLast(limit) {
          validateArgCount('Query.limitToLast', 1, 1, arguments.length);
          if (typeof limit !== 'number' ||
              Math.floor(limit) !== limit ||
              limit <= 0) {
              throw new Error('Query.limitToLast: First argument must be a positive integer.');
          }
          if (this.queryParams_.hasLimit()) {
              throw new Error('Query.limitToLast: Limit was already set (by another call to limit, ' +
                  'limitToFirst, or limitToLast).');
          }
          return new Query(this.repo, this.path, this.queryParams_.limitToLast(limit), this.orderByCalled_);
      }
      /**
       * Given a child path, return a new query ordered by the specified grandchild path.
       * @param {!string} path
       * @return {!Query}
       */
      orderByChild(path) {
          validateArgCount('Query.orderByChild', 1, 1, arguments.length);
          if (path === '$key') {
              throw new Error('Query.orderByChild: "$key" is invalid.  Use Query.orderByKey() instead.');
          }
          else if (path === '$priority') {
              throw new Error('Query.orderByChild: "$priority" is invalid.  Use Query.orderByPriority() instead.');
          }
          else if (path === '$value') {
              throw new Error('Query.orderByChild: "$value" is invalid.  Use Query.orderByValue() instead.');
          }
          validatePathString('Query.orderByChild', 1, path, false);
          this.validateNoPreviousOrderByCall_('Query.orderByChild');
          const parsedPath = new Path(path);
          if (parsedPath.isEmpty()) {
              throw new Error('Query.orderByChild: cannot pass in empty path.  Use Query.orderByValue() instead.');
          }
          const index = new PathIndex(parsedPath);
          const newParams = this.queryParams_.orderBy(index);
          Query.validateQueryEndpoints_(newParams);
          return new Query(this.repo, this.path, newParams, /*orderByCalled=*/ true);
      }
      /**
       * Return a new query ordered by the KeyIndex
       * @return {!Query}
       */
      orderByKey() {
          validateArgCount('Query.orderByKey', 0, 0, arguments.length);
          this.validateNoPreviousOrderByCall_('Query.orderByKey');
          const newParams = this.queryParams_.orderBy(KEY_INDEX);
          Query.validateQueryEndpoints_(newParams);
          return new Query(this.repo, this.path, newParams, /*orderByCalled=*/ true);
      }
      /**
       * Return a new query ordered by the PriorityIndex
       * @return {!Query}
       */
      orderByPriority() {
          validateArgCount('Query.orderByPriority', 0, 0, arguments.length);
          this.validateNoPreviousOrderByCall_('Query.orderByPriority');
          const newParams = this.queryParams_.orderBy(PRIORITY_INDEX);
          Query.validateQueryEndpoints_(newParams);
          return new Query(this.repo, this.path, newParams, /*orderByCalled=*/ true);
      }
      /**
       * Return a new query ordered by the ValueIndex
       * @return {!Query}
       */
      orderByValue() {
          validateArgCount('Query.orderByValue', 0, 0, arguments.length);
          this.validateNoPreviousOrderByCall_('Query.orderByValue');
          const newParams = this.queryParams_.orderBy(VALUE_INDEX);
          Query.validateQueryEndpoints_(newParams);
          return new Query(this.repo, this.path, newParams, /*orderByCalled=*/ true);
      }
      /**
       * @param {number|string|boolean|null} value
       * @param {?string=} name
       * @return {!Query}
       */
      startAt(value = null, name) {
          validateArgCount('Query.startAt', 0, 2, arguments.length);
          validateFirebaseDataArg('Query.startAt', 1, value, this.path, true);
          validateKey('Query.startAt', 2, name, true);
          const newParams = this.queryParams_.startAt(value, name);
          Query.validateLimit_(newParams);
          Query.validateQueryEndpoints_(newParams);
          if (this.queryParams_.hasStart()) {
              throw new Error('Query.startAt: Starting point was already set (by another call to startAt ' +
                  'or equalTo).');
          }
          // Calling with no params tells us to start at the beginning.
          if (value === undefined) {
              value = null;
              name = null;
          }
          return new Query(this.repo, this.path, newParams, this.orderByCalled_);
      }
      /**
       * @param {number|string|boolean|null} value
       * @param {?string=} name
       * @return {!Query}
       */
      endAt(value = null, name) {
          validateArgCount('Query.endAt', 0, 2, arguments.length);
          validateFirebaseDataArg('Query.endAt', 1, value, this.path, true);
          validateKey('Query.endAt', 2, name, true);
          const newParams = this.queryParams_.endAt(value, name);
          Query.validateLimit_(newParams);
          Query.validateQueryEndpoints_(newParams);
          if (this.queryParams_.hasEnd()) {
              throw new Error('Query.endAt: Ending point was already set (by another call to endAt or ' +
                  'equalTo).');
          }
          return new Query(this.repo, this.path, newParams, this.orderByCalled_);
      }
      /**
       * Load the selection of children with exactly the specified value, and, optionally,
       * the specified name.
       * @param {number|string|boolean|null} value
       * @param {string=} name
       * @return {!Query}
       */
      equalTo(value, name) {
          validateArgCount('Query.equalTo', 1, 2, arguments.length);
          validateFirebaseDataArg('Query.equalTo', 1, value, this.path, false);
          validateKey('Query.equalTo', 2, name, true);
          if (this.queryParams_.hasStart()) {
              throw new Error('Query.equalTo: Starting point was already set (by another call to startAt or ' +
                  'equalTo).');
          }
          if (this.queryParams_.hasEnd()) {
              throw new Error('Query.equalTo: Ending point was already set (by another call to endAt or ' +
                  'equalTo).');
          }
          return this.startAt(value, name).endAt(value, name);
      }
      /**
       * @return {!string} URL for this location.
       */
      toString() {
          validateArgCount('Query.toString', 0, 0, arguments.length);
          return this.repo.toString() + this.path.toUrlEncodedString();
      }
      // Do not create public documentation. This is intended to make JSON serialization work but is otherwise unnecessary
      // for end-users.
      toJSON() {
          // An optional spacer argument is unnecessary for a string.
          validateArgCount('Query.toJSON', 0, 1, arguments.length);
          return this.toString();
      }
      /**
       * An object representation of the query parameters used by this Query.
       * @return {!Object}
       */
      queryObject() {
          return this.queryParams_.getQueryObject();
      }
      /**
       * @return {!string}
       */
      queryIdentifier() {
          const obj = this.queryObject();
          const id = ObjectToUniqueKey(obj);
          return id === '{}' ? 'default' : id;
      }
      /**
       * Return true if this query and the provided query are equivalent; otherwise, return false.
       * @param {Query} other
       * @return {boolean}
       */
      isEqual(other) {
          validateArgCount('Query.isEqual', 1, 1, arguments.length);
          if (!(other instanceof Query)) {
              const error = 'Query.isEqual failed: First argument must be an instance of firebase.database.Query.';
              throw new Error(error);
          }
          const sameRepo = this.repo === other.repo;
          const samePath = this.path.equals(other.path);
          const sameQueryIdentifier = this.queryIdentifier() === other.queryIdentifier();
          return sameRepo && samePath && sameQueryIdentifier;
      }
      /**
       * Helper used by .on and .once to extract the context and or cancel arguments.
       * @param {!string} fnName The function name (on or once)
       * @param {(function(Error)|Object)=} cancelOrContext
       * @param {Object=} context
       * @return {{cancel: ?function(Error), context: ?Object}}
       * @private
       */
      static getCancelAndContextArgs_(fnName, cancelOrContext, context) {
          const ret = { cancel: null, context: null };
          if (cancelOrContext && context) {
              ret.cancel = cancelOrContext;
              validateCallback(fnName, 3, ret.cancel, true);
              ret.context = context;
              validateContextObject(fnName, 4, ret.context, true);
          }
          else if (cancelOrContext) {
              // we have either a cancel callback or a context.
              if (typeof cancelOrContext === 'object' && cancelOrContext !== null) {
                  // it's a context!
                  ret.context = cancelOrContext;
              }
              else if (typeof cancelOrContext === 'function') {
                  ret.cancel = cancelOrContext;
              }
              else {
                  throw new Error(errorPrefix(fnName, 3, true) +
                      ' must either be a cancel callback or a context object.');
              }
          }
          return ret;
      }
      get ref() {
          return this.getRef();
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Implements a set with a count of elements.
   *
   * @template K, V
   */
  class CountedSet {
      constructor() {
          this.set = {};
      }
      /**
       * @param {!K} item
       * @param {V} val
       */
      add(item, val) {
          this.set[item] = val !== null ? val : true;
      }
      /**
       * @param {!K} key
       * @return {boolean}
       */
      contains(key) {
          return contains(this.set, key);
      }
      /**
       * @param {!K} item
       * @return {V}
       */
      get(item) {
          return this.contains(item) ? this.set[item] : undefined;
      }
      /**
       * @param {!K} item
       */
      remove(item) {
          delete this.set[item];
      }
      /**
       * Deletes everything in the set
       */
      clear() {
          this.set = {};
      }
      /**
       * True if there's nothing in the set
       * @return {boolean}
       */
      isEmpty() {
          return isEmpty(this.set);
      }
      /**
       * @return {number} The number of items in the set
       */
      count() {
          return getCount(this.set);
      }
      /**
       * Run a function on each k,v pair in the set
       * @param {function(K, V)} fn
       */
      each(fn) {
          forEach(this.set, (k, v) => fn(k, v));
      }
      /**
       * Mostly for debugging
       * @return {Array.<K>} The keys present in this CountedSet
       */
      keys() {
          const keys = [];
          forEach(this.set, (k) => {
              keys.push(k);
          });
          return keys;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Helper class to store a sparse set of snapshots.
   *
   * @constructor
   */
  class SparseSnapshotTree {
      constructor() {
          /**
           * @private
           * @type {Node}
           */
          this.value_ = null;
          /**
           * @private
           * @type {CountedSet}
           */
          this.children_ = null;
      }
      /**
       * Gets the node stored at the given path if one exists.
       *
       * @param {!Path} path Path to look up snapshot for.
       * @return {?Node} The retrieved node, or null.
       */
      find(path) {
          if (this.value_ != null) {
              return this.value_.getChild(path);
          }
          else if (!path.isEmpty() && this.children_ != null) {
              const childKey = path.getFront();
              path = path.popFront();
              if (this.children_.contains(childKey)) {
                  const childTree = this.children_.get(childKey);
                  return childTree.find(path);
              }
              else {
                  return null;
              }
          }
          else {
              return null;
          }
      }
      /**
       * Stores the given node at the specified path. If there is already a node
       * at a shallower path, it merges the new data into that snapshot node.
       *
       * @param {!Path} path Path to look up snapshot for.
       * @param {!Node} data The new data, or null.
       */
      remember(path, data) {
          if (path.isEmpty()) {
              this.value_ = data;
              this.children_ = null;
          }
          else if (this.value_ !== null) {
              this.value_ = this.value_.updateChild(path, data);
          }
          else {
              if (this.children_ == null) {
                  this.children_ = new CountedSet();
              }
              const childKey = path.getFront();
              if (!this.children_.contains(childKey)) {
                  this.children_.add(childKey, new SparseSnapshotTree());
              }
              const child = this.children_.get(childKey);
              path = path.popFront();
              child.remember(path, data);
          }
      }
      /**
       * Purge the data at path from the cache.
       *
       * @param {!Path} path Path to look up snapshot for.
       * @return {boolean} True if this node should now be removed.
       */
      forget(path) {
          if (path.isEmpty()) {
              this.value_ = null;
              this.children_ = null;
              return true;
          }
          else {
              if (this.value_ !== null) {
                  if (this.value_.isLeafNode()) {
                      // We're trying to forget a node that doesn't exist
                      return false;
                  }
                  else {
                      const value = this.value_;
                      this.value_ = null;
                      const self = this;
                      value.forEachChild(PRIORITY_INDEX, function (key, tree) {
                          self.remember(new Path(key), tree);
                      });
                      return this.forget(path);
                  }
              }
              else if (this.children_ !== null) {
                  const childKey = path.getFront();
                  path = path.popFront();
                  if (this.children_.contains(childKey)) {
                      const safeToRemove = this.children_.get(childKey).forget(path);
                      if (safeToRemove) {
                          this.children_.remove(childKey);
                      }
                  }
                  if (this.children_.isEmpty()) {
                      this.children_ = null;
                      return true;
                  }
                  else {
                      return false;
                  }
              }
              else {
                  return true;
              }
          }
      }
      /**
       * Recursively iterates through all of the stored tree and calls the
       * callback on each one.
       *
       * @param {!Path} prefixPath Path to look up node for.
       * @param {!Function} func The function to invoke for each tree.
       */
      forEachTree(prefixPath, func) {
          if (this.value_ !== null) {
              func(prefixPath, this.value_);
          }
          else {
              this.forEachChild((key, tree) => {
                  const path = new Path(prefixPath.toString() + '/' + key);
                  tree.forEachTree(path, func);
              });
          }
      }
      /**
       * Iterates through each immediate child and triggers the callback.
       *
       * @param {!Function} func The function to invoke for each child.
       */
      forEachChild(func) {
          if (this.children_ !== null) {
              this.children_.each((key, tree) => {
                  func(key, tree);
              });
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Generate placeholders for deferred values.
   * @param {?Object} values
   * @return {!Object}
   */
  const generateWithValues = function (values) {
      values = values || {};
      values['timestamp'] = values['timestamp'] || new Date().getTime();
      return values;
  };
  /**
   * Value to use when firing local events. When writing server values, fire
   * local events with an approximate value, otherwise return value as-is.
   * @param {(Object|string|number|boolean)} value
   * @param {!Object} serverValues
   * @return {!(string|number|boolean)}
   */
  const resolveDeferredValue = function (value, serverValues) {
      if (!value || typeof value !== 'object') {
          return value;
      }
      else {
          assert('.sv' in value, 'Unexpected leaf node or priority contents');
          return serverValues[value['.sv']];
      }
  };
  /**
   * Recursively replace all deferred values and priorities in the tree with the
   * specified generated replacement values.
   * @param {!SparseSnapshotTree} tree
   * @param {!Object} serverValues
   * @return {!SparseSnapshotTree}
   */
  const resolveDeferredValueTree = function (tree, serverValues) {
      const resolvedTree = new SparseSnapshotTree();
      tree.forEachTree(new Path(''), function (path, node) {
          resolvedTree.remember(path, resolveDeferredValueSnapshot(node, serverValues));
      });
      return resolvedTree;
  };
  /**
   * Recursively replace all deferred values and priorities in the node with the
   * specified generated replacement values.  If there are no server values in the node,
   * it'll be returned as-is.
   * @param {!Node} node
   * @param {!Object} serverValues
   * @return {!Node}
   */
  const resolveDeferredValueSnapshot = function (node, serverValues) {
      const rawPri = node.getPriority().val();
      const priority = resolveDeferredValue(rawPri, serverValues);
      let newNode;
      if (node.isLeafNode()) {
          const leafNode = node;
          const value = resolveDeferredValue(leafNode.getValue(), serverValues);
          if (value !== leafNode.getValue() ||
              priority !== leafNode.getPriority().val()) {
              return new LeafNode(value, nodeFromJSON$1(priority));
          }
          else {
              return node;
          }
      }
      else {
          const childrenNode = node;
          newNode = childrenNode;
          if (priority !== childrenNode.getPriority().val()) {
              newNode = newNode.updatePriority(new LeafNode(priority));
          }
          childrenNode.forEachChild(PRIORITY_INDEX, function (childName, childNode) {
              const newChildNode = resolveDeferredValueSnapshot(childNode, serverValues);
              if (newChildNode !== childNode) {
                  newNode = newNode.updateImmediateChild(childName, newChildNode);
              }
          });
          return newNode;
      }
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   *
   * @enum
   */
  var OperationType;
  (function (OperationType) {
      OperationType[OperationType["OVERWRITE"] = 0] = "OVERWRITE";
      OperationType[OperationType["MERGE"] = 1] = "MERGE";
      OperationType[OperationType["ACK_USER_WRITE"] = 2] = "ACK_USER_WRITE";
      OperationType[OperationType["LISTEN_COMPLETE"] = 3] = "LISTEN_COMPLETE";
  })(OperationType || (OperationType = {}));
  /**
   * @param {boolean} fromUser
   * @param {boolean} fromServer
   * @param {?string} queryId
   * @param {boolean} tagged
   * @constructor
   */
  class OperationSource {
      constructor(fromUser, fromServer, queryId, tagged) {
          this.fromUser = fromUser;
          this.fromServer = fromServer;
          this.queryId = queryId;
          this.tagged = tagged;
          assert(!tagged || fromServer, 'Tagged queries must be from server.');
      }
  }
  /**
   * @const
   * @type {!OperationSource}
   */
  OperationSource.User = new OperationSource(
  /*fromUser=*/ true, false, null, 
  /*tagged=*/ false);
  /**
   * @const
   * @type {!OperationSource}
   */
  OperationSource.Server = new OperationSource(false, 
  /*fromServer=*/ true, null, 
  /*tagged=*/ false);
  /**
   * @param {string} queryId
   * @return {!OperationSource}
   */
  OperationSource.forServerTaggedQuery = function (queryId) {
      return new OperationSource(false, 
      /*fromServer=*/ true, queryId, 
      /*tagged=*/ true);
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  class AckUserWrite {
      /**
       *
       * @param {!Path} path
       * @param {!ImmutableTree<!boolean>} affectedTree A tree containing true for each affected path. Affected paths can't overlap.
       * @param {!boolean} revert
       */
      constructor(
      /**@inheritDoc */ path, 
      /**@inheritDoc */ affectedTree, 
      /**@inheritDoc */ revert) {
          this.path = path;
          this.affectedTree = affectedTree;
          this.revert = revert;
          /** @inheritDoc */
          this.type = OperationType.ACK_USER_WRITE;
          /** @inheritDoc */
          this.source = OperationSource.User;
      }
      /**
       * @inheritDoc
       */
      operationForChild(childName) {
          if (!this.path.isEmpty()) {
              assert(this.path.getFront() === childName, 'operationForChild called for unrelated child.');
              return new AckUserWrite(this.path.popFront(), this.affectedTree, this.revert);
          }
          else if (this.affectedTree.value != null) {
              assert(this.affectedTree.children.isEmpty(), 'affectedTree should not have overlapping affected paths.');
              // All child locations are affected as well; just return same operation.
              return this;
          }
          else {
              const childTree = this.affectedTree.subtree(new Path(childName));
              return new AckUserWrite(Path.Empty, childTree, this.revert);
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  let emptyChildrenSingleton;
  /**
   * Singleton empty children collection.
   *
   * @const
   * @type {!SortedMap.<string, !ImmutableTree.<?>>}
   */
  const EmptyChildren = () => {
      if (!emptyChildrenSingleton) {
          emptyChildrenSingleton = new SortedMap(stringCompare);
      }
      return emptyChildrenSingleton;
  };
  /**
   * A tree with immutable elements.
   */
  class ImmutableTree {
      /**
       * @template T
       * @param {?T} value
       * @param {SortedMap.<string, !ImmutableTree.<T>>=} children
       */
      constructor(value, children = EmptyChildren()) {
          this.value = value;
          this.children = children;
      }
      /**
       * @template T
       * @param {!Object.<string, !T>} obj
       * @return {!ImmutableTree.<!T>}
       */
      static fromObject(obj) {
          let tree = ImmutableTree.Empty;
          forEach(obj, (childPath, childSnap) => {
              tree = tree.set(new Path(childPath), childSnap);
          });
          return tree;
      }
      /**
       * True if the value is empty and there are no children
       * @return {boolean}
       */
      isEmpty() {
          return this.value === null && this.children.isEmpty();
      }
      /**
       * Given a path and predicate, return the first node and the path to that node
       * where the predicate returns true.
       *
       * TODO Do a perf test -- If we're creating a bunch of {path: value:} objects
       * on the way back out, it may be better to pass down a pathSoFar obj.
       *
       * @param {!Path} relativePath The remainder of the path
       * @param {function(T):boolean} predicate The predicate to satisfy to return a
       *   node
       * @return {?{path:!Path, value:!T}}
       */
      findRootMostMatchingPathAndValue(relativePath, predicate) {
          if (this.value != null && predicate(this.value)) {
              return { path: Path.Empty, value: this.value };
          }
          else {
              if (relativePath.isEmpty()) {
                  return null;
              }
              else {
                  const front = relativePath.getFront();
                  const child = this.children.get(front);
                  if (child !== null) {
                      const childExistingPathAndValue = child.findRootMostMatchingPathAndValue(relativePath.popFront(), predicate);
                      if (childExistingPathAndValue != null) {
                          const fullPath = new Path(front).child(childExistingPathAndValue.path);
                          return { path: fullPath, value: childExistingPathAndValue.value };
                      }
                      else {
                          return null;
                      }
                  }
                  else {
                      return null;
                  }
              }
          }
      }
      /**
       * Find, if it exists, the shortest subpath of the given path that points a defined
       * value in the tree
       * @param {!Path} relativePath
       * @return {?{path: !Path, value: !T}}
       */
      findRootMostValueAndPath(relativePath) {
          return this.findRootMostMatchingPathAndValue(relativePath, () => true);
      }
      /**
       * @param {!Path} relativePath
       * @return {!ImmutableTree.<T>} The subtree at the given path
       */
      subtree(relativePath) {
          if (relativePath.isEmpty()) {
              return this;
          }
          else {
              const front = relativePath.getFront();
              const childTree = this.children.get(front);
              if (childTree !== null) {
                  return childTree.subtree(relativePath.popFront());
              }
              else {
                  return ImmutableTree.Empty;
              }
          }
      }
      /**
       * Sets a value at the specified path.
       *
       * @param {!Path} relativePath Path to set value at.
       * @param {?T} toSet Value to set.
       * @return {!ImmutableTree.<T>} Resulting tree.
       */
      set(relativePath, toSet) {
          if (relativePath.isEmpty()) {
              return new ImmutableTree(toSet, this.children);
          }
          else {
              const front = relativePath.getFront();
              const child = this.children.get(front) || ImmutableTree.Empty;
              const newChild = child.set(relativePath.popFront(), toSet);
              const newChildren = this.children.insert(front, newChild);
              return new ImmutableTree(this.value, newChildren);
          }
      }
      /**
       * Removes the value at the specified path.
       *
       * @param {!Path} relativePath Path to value to remove.
       * @return {!ImmutableTree.<T>} Resulting tree.
       */
      remove(relativePath) {
          if (relativePath.isEmpty()) {
              if (this.children.isEmpty()) {
                  return ImmutableTree.Empty;
              }
              else {
                  return new ImmutableTree(null, this.children);
              }
          }
          else {
              const front = relativePath.getFront();
              const child = this.children.get(front);
              if (child) {
                  const newChild = child.remove(relativePath.popFront());
                  let newChildren;
                  if (newChild.isEmpty()) {
                      newChildren = this.children.remove(front);
                  }
                  else {
                      newChildren = this.children.insert(front, newChild);
                  }
                  if (this.value === null && newChildren.isEmpty()) {
                      return ImmutableTree.Empty;
                  }
                  else {
                      return new ImmutableTree(this.value, newChildren);
                  }
              }
              else {
                  return this;
              }
          }
      }
      /**
       * Gets a value from the tree.
       *
       * @param {!Path} relativePath Path to get value for.
       * @return {?T} Value at path, or null.
       */
      get(relativePath) {
          if (relativePath.isEmpty()) {
              return this.value;
          }
          else {
              const front = relativePath.getFront();
              const child = this.children.get(front);
              if (child) {
                  return child.get(relativePath.popFront());
              }
              else {
                  return null;
              }
          }
      }
      /**
       * Replace the subtree at the specified path with the given new tree.
       *
       * @param {!Path} relativePath Path to replace subtree for.
       * @param {!ImmutableTree} newTree New tree.
       * @return {!ImmutableTree} Resulting tree.
       */
      setTree(relativePath, newTree) {
          if (relativePath.isEmpty()) {
              return newTree;
          }
          else {
              const front = relativePath.getFront();
              const child = this.children.get(front) || ImmutableTree.Empty;
              const newChild = child.setTree(relativePath.popFront(), newTree);
              let newChildren;
              if (newChild.isEmpty()) {
                  newChildren = this.children.remove(front);
              }
              else {
                  newChildren = this.children.insert(front, newChild);
              }
              return new ImmutableTree(this.value, newChildren);
          }
      }
      /**
       * Performs a depth first fold on this tree. Transforms a tree into a single
       * value, given a function that operates on the path to a node, an optional
       * current value, and a map of child names to folded subtrees
       * @template V
       * @param {function(Path, ?T, Object.<string, V>):V} fn
       * @return {V}
       */
      fold(fn) {
          return this.fold_(Path.Empty, fn);
      }
      /**
       * Recursive helper for public-facing fold() method
       * @template V
       * @param {!Path} pathSoFar
       * @param {function(Path, ?T, Object.<string, V>):V} fn
       * @return {V}
       * @private
       */
      fold_(pathSoFar, fn) {
          const accum = {};
          this.children.inorderTraversal(function (childKey, childTree) {
              accum[childKey] = childTree.fold_(pathSoFar.child(childKey), fn);
          });
          return fn(pathSoFar, this.value, accum);
      }
      /**
       * Find the first matching value on the given path. Return the result of applying f to it.
       * @template V
       * @param {!Path} path
       * @param {!function(!Path, !T):?V} f
       * @return {?V}
       */
      findOnPath(path, f) {
          return this.findOnPath_(path, Path.Empty, f);
      }
      findOnPath_(pathToFollow, pathSoFar, f) {
          const result = this.value ? f(pathSoFar, this.value) : false;
          if (result) {
              return result;
          }
          else {
              if (pathToFollow.isEmpty()) {
                  return null;
              }
              else {
                  const front = pathToFollow.getFront();
                  const nextChild = this.children.get(front);
                  if (nextChild) {
                      return nextChild.findOnPath_(pathToFollow.popFront(), pathSoFar.child(front), f);
                  }
                  else {
                      return null;
                  }
              }
          }
      }
      /**
       *
       * @param {!Path} path
       * @param {!function(!Path, !T)} f
       * @returns {!ImmutableTree.<T>}
       */
      foreachOnPath(path, f) {
          return this.foreachOnPath_(path, Path.Empty, f);
      }
      foreachOnPath_(pathToFollow, currentRelativePath, f) {
          if (pathToFollow.isEmpty()) {
              return this;
          }
          else {
              if (this.value) {
                  f(currentRelativePath, this.value);
              }
              const front = pathToFollow.getFront();
              const nextChild = this.children.get(front);
              if (nextChild) {
                  return nextChild.foreachOnPath_(pathToFollow.popFront(), currentRelativePath.child(front), f);
              }
              else {
                  return ImmutableTree.Empty;
              }
          }
      }
      /**
       * Calls the given function for each node in the tree that has a value.
       *
       * @param {function(!Path, !T)} f A function to be called with
       *   the path from the root of the tree to a node, and the value at that node.
       *   Called in depth-first order.
       */
      foreach(f) {
          this.foreach_(Path.Empty, f);
      }
      foreach_(currentRelativePath, f) {
          this.children.inorderTraversal(function (childName, childTree) {
              childTree.foreach_(currentRelativePath.child(childName), f);
          });
          if (this.value) {
              f(currentRelativePath, this.value);
          }
      }
      /**
       *
       * @param {function(string, !T)} f
       */
      foreachChild(f) {
          this.children.inorderTraversal((childName, childTree) => {
              if (childTree.value) {
                  f(childName, childTree.value);
              }
          });
      }
  }
  ImmutableTree.Empty = new ImmutableTree(null);
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @param {!OperationSource} source
   * @param {!Path} path
   * @constructor
   * @implements {Operation}
   */
  class ListenComplete {
      constructor(source, path) {
          this.source = source;
          this.path = path;
          /** @inheritDoc */
          this.type = OperationType.LISTEN_COMPLETE;
      }
      operationForChild(childName) {
          if (this.path.isEmpty()) {
              return new ListenComplete(this.source, Path.Empty);
          }
          else {
              return new ListenComplete(this.source, this.path.popFront());
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @param {!OperationSource} source
   * @param {!Path} path
   * @param {!Node} snap
   * @constructor
   * @implements {Operation}
   */
  class Overwrite {
      constructor(source, path, snap) {
          this.source = source;
          this.path = path;
          this.snap = snap;
          /** @inheritDoc */
          this.type = OperationType.OVERWRITE;
      }
      operationForChild(childName) {
          if (this.path.isEmpty()) {
              return new Overwrite(this.source, Path.Empty, this.snap.getImmediateChild(childName));
          }
          else {
              return new Overwrite(this.source, this.path.popFront(), this.snap);
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @param {!OperationSource} source
   * @param {!Path} path
   * @param {!ImmutableTree.<!Node>} children
   * @constructor
   * @implements {Operation}
   */
  class Merge {
      constructor(
      /**@inheritDoc */ source, 
      /**@inheritDoc */ path, 
      /**@inheritDoc */ children) {
          this.source = source;
          this.path = path;
          this.children = children;
          /** @inheritDoc */
          this.type = OperationType.MERGE;
      }
      /**
       * @inheritDoc
       */
      operationForChild(childName) {
          if (this.path.isEmpty()) {
              const childTree = this.children.subtree(new Path(childName));
              if (childTree.isEmpty()) {
                  // This child is unaffected
                  return null;
              }
              else if (childTree.value) {
                  // We have a snapshot for the child in question.  This becomes an overwrite of the child.
                  return new Overwrite(this.source, Path.Empty, childTree.value);
              }
              else {
                  // This is a merge at a deeper level
                  return new Merge(this.source, Path.Empty, childTree);
              }
          }
          else {
              assert(this.path.getFront() === childName, "Can't get a merge for a child not on the path of the operation");
              return new Merge(this.source, this.path.popFront(), this.children);
          }
      }
      /**
       * @inheritDoc
       */
      toString() {
          return ('Operation(' +
              this.path +
              ': ' +
              this.source.toString() +
              ' merge: ' +
              this.children.toString() +
              ')');
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * A cache node only stores complete children. Additionally it holds a flag whether the node can be considered fully
   * initialized in the sense that we know at one point in time this represented a valid state of the world, e.g.
   * initialized with data from the server, or a complete overwrite by the client. The filtered flag also tracks
   * whether a node potentially had children removed due to a filter.
   */
  class CacheNode {
      /**
       * @param {!Node} node_
       * @param {boolean} fullyInitialized_
       * @param {boolean} filtered_
       */
      constructor(node_, fullyInitialized_, filtered_) {
          this.node_ = node_;
          this.fullyInitialized_ = fullyInitialized_;
          this.filtered_ = filtered_;
      }
      /**
       * Returns whether this node was fully initialized with either server data or a complete overwrite by the client
       * @return {boolean}
       */
      isFullyInitialized() {
          return this.fullyInitialized_;
      }
      /**
       * Returns whether this node is potentially missing children due to a filter applied to the node
       * @return {boolean}
       */
      isFiltered() {
          return this.filtered_;
      }
      /**
       * @param {!Path} path
       * @return {boolean}
       */
      isCompleteForPath(path) {
          if (path.isEmpty()) {
              return this.isFullyInitialized() && !this.filtered_;
          }
          const childKey = path.getFront();
          return this.isCompleteForChild(childKey);
      }
      /**
       * @param {!string} key
       * @return {boolean}
       */
      isCompleteForChild(key) {
          return ((this.isFullyInitialized() && !this.filtered_) || this.node_.hasChild(key));
      }
      /**
       * @return {!Node}
       */
      getNode() {
          return this.node_;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Stores the data we have cached for a view.
   *
   * serverSnap is the cached server data, eventSnap is the cached event data (server data plus any local writes).
   *
   * @constructor
   */
  class ViewCache {
      /**
       *
       * @param {!CacheNode} eventCache_
       * @param {!CacheNode} serverCache_
       */
      constructor(eventCache_, serverCache_) {
          this.eventCache_ = eventCache_;
          this.serverCache_ = serverCache_;
      }
      /**
       * @param {!Node} eventSnap
       * @param {boolean} complete
       * @param {boolean} filtered
       * @return {!ViewCache}
       */
      updateEventSnap(eventSnap, complete, filtered) {
          return new ViewCache(new CacheNode(eventSnap, complete, filtered), this.serverCache_);
      }
      /**
       * @param {!Node} serverSnap
       * @param {boolean} complete
       * @param {boolean} filtered
       * @return {!ViewCache}
       */
      updateServerSnap(serverSnap, complete, filtered) {
          return new ViewCache(this.eventCache_, new CacheNode(serverSnap, complete, filtered));
      }
      /**
       * @return {!CacheNode}
       */
      getEventCache() {
          return this.eventCache_;
      }
      /**
       * @return {?Node}
       */
      getCompleteEventSnap() {
          return this.eventCache_.isFullyInitialized()
              ? this.eventCache_.getNode()
              : null;
      }
      /**
       * @return {!CacheNode}
       */
      getServerCache() {
          return this.serverCache_;
      }
      /**
       * @return {?Node}
       */
      getCompleteServerSnap() {
          return this.serverCache_.isFullyInitialized()
              ? this.serverCache_.getNode()
              : null;
      }
  }
  /**
   * @const
   * @type {ViewCache}
   */
  ViewCache.Empty = new ViewCache(new CacheNode(ChildrenNode.EMPTY_NODE, 
  /*fullyInitialized=*/ false, 
  /*filtered=*/ false), new CacheNode(ChildrenNode.EMPTY_NODE, 
  /*fullyInitialized=*/ false, 
  /*filtered=*/ false));
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @constructor
   * @struct
   * @param {!string} type The event type
   * @param {!Node} snapshotNode The data
   * @param {string=} childName The name for this child, if it's a child event
   * @param {Node=} oldSnap Used for intermediate processing of child changed events
   * @param {string=} prevName The name for the previous child, if applicable
   */
  class Change {
      constructor(type, snapshotNode, childName, oldSnap, prevName) {
          this.type = type;
          this.snapshotNode = snapshotNode;
          this.childName = childName;
          this.oldSnap = oldSnap;
          this.prevName = prevName;
      }
      /**
       * @param {!Node} snapshot
       * @return {!Change}
       */
      static valueChange(snapshot) {
          return new Change(Change.VALUE, snapshot);
      }
      /**
       * @param {string} childKey
       * @param {!Node} snapshot
       * @return {!Change}
       */
      static childAddedChange(childKey, snapshot) {
          return new Change(Change.CHILD_ADDED, snapshot, childKey);
      }
      /**
       * @param {string} childKey
       * @param {!Node} snapshot
       * @return {!Change}
       */
      static childRemovedChange(childKey, snapshot) {
          return new Change(Change.CHILD_REMOVED, snapshot, childKey);
      }
      /**
       * @param {string} childKey
       * @param {!Node} newSnapshot
       * @param {!Node} oldSnapshot
       * @return {!Change}
       */
      static childChangedChange(childKey, newSnapshot, oldSnapshot) {
          return new Change(Change.CHILD_CHANGED, newSnapshot, childKey, oldSnapshot);
      }
      /**
       * @param {string} childKey
       * @param {!Node} snapshot
       * @return {!Change}
       */
      static childMovedChange(childKey, snapshot) {
          return new Change(Change.CHILD_MOVED, snapshot, childKey);
      }
  }
  //event types
  /** Event type for a child added */
  Change.CHILD_ADDED = 'child_added';
  /** Event type for a child removed */
  Change.CHILD_REMOVED = 'child_removed';
  /** Event type for a child changed */
  Change.CHILD_CHANGED = 'child_changed';
  /** Event type for a child moved */
  Change.CHILD_MOVED = 'child_moved';
  /** Event type for a value change */
  Change.VALUE = 'value';
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Doesn't really filter nodes but applies an index to the node and keeps track of any changes
   *
   * @constructor
   * @implements {NodeFilter}
   * @param {!Index} index
   */
  class IndexedFilter {
      constructor(index_) {
          this.index_ = index_;
      }
      updateChild(snap, key, newChild, affectedPath, source, optChangeAccumulator) {
          assert(snap.isIndexed(this.index_), 'A node must be indexed if only a child is updated');
          const oldChild = snap.getImmediateChild(key);
          // Check if anything actually changed.
          if (oldChild.getChild(affectedPath).equals(newChild.getChild(affectedPath))) {
              // There's an edge case where a child can enter or leave the view because affectedPath was set to null.
              // In this case, affectedPath will appear null in both the old and new snapshots.  So we need
              // to avoid treating these cases as "nothing changed."
              if (oldChild.isEmpty() == newChild.isEmpty()) {
                  // Nothing changed.
                  // This assert should be valid, but it's expensive (can dominate perf testing) so don't actually do it.
                  //assert(oldChild.equals(newChild), 'Old and new snapshots should be equal.');
                  return snap;
              }
          }
          if (optChangeAccumulator != null) {
              if (newChild.isEmpty()) {
                  if (snap.hasChild(key)) {
                      optChangeAccumulator.trackChildChange(Change.childRemovedChange(key, oldChild));
                  }
                  else {
                      assert(snap.isLeafNode(), 'A child remove without an old child only makes sense on a leaf node');
                  }
              }
              else if (oldChild.isEmpty()) {
                  optChangeAccumulator.trackChildChange(Change.childAddedChange(key, newChild));
              }
              else {
                  optChangeAccumulator.trackChildChange(Change.childChangedChange(key, newChild, oldChild));
              }
          }
          if (snap.isLeafNode() && newChild.isEmpty()) {
              return snap;
          }
          else {
              // Make sure the node is indexed
              return snap.updateImmediateChild(key, newChild).withIndex(this.index_);
          }
      }
      /**
       * @inheritDoc
       */
      updateFullNode(oldSnap, newSnap, optChangeAccumulator) {
          if (optChangeAccumulator != null) {
              if (!oldSnap.isLeafNode()) {
                  oldSnap.forEachChild(PRIORITY_INDEX, function (key, childNode) {
                      if (!newSnap.hasChild(key)) {
                          optChangeAccumulator.trackChildChange(Change.childRemovedChange(key, childNode));
                      }
                  });
              }
              if (!newSnap.isLeafNode()) {
                  newSnap.forEachChild(PRIORITY_INDEX, function (key, childNode) {
                      if (oldSnap.hasChild(key)) {
                          const oldChild = oldSnap.getImmediateChild(key);
                          if (!oldChild.equals(childNode)) {
                              optChangeAccumulator.trackChildChange(Change.childChangedChange(key, childNode, oldChild));
                          }
                      }
                      else {
                          optChangeAccumulator.trackChildChange(Change.childAddedChange(key, childNode));
                      }
                  });
              }
          }
          return newSnap.withIndex(this.index_);
      }
      /**
       * @inheritDoc
       */
      updatePriority(oldSnap, newPriority) {
          if (oldSnap.isEmpty()) {
              return ChildrenNode.EMPTY_NODE;
          }
          else {
              return oldSnap.updatePriority(newPriority);
          }
      }
      /**
       * @inheritDoc
       */
      filtersNodes() {
          return false;
      }
      /**
       * @inheritDoc
       */
      getIndexedFilter() {
          return this;
      }
      /**
       * @inheritDoc
       */
      getIndex() {
          return this.index_;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @constructor
   */
  class ChildChangeAccumulator {
      constructor() {
          this.changeMap_ = {};
      }
      /**
       * @param {!Change} change
       */
      trackChildChange(change) {
          const type = change.type;
          const childKey /** @type {!string} */ = change.childName;
          assert(type == Change.CHILD_ADDED ||
              type == Change.CHILD_CHANGED ||
              type == Change.CHILD_REMOVED, 'Only child changes supported for tracking');
          assert(childKey !== '.priority', 'Only non-priority child changes can be tracked.');
          const oldChange = safeGet(this.changeMap_, childKey);
          if (oldChange) {
              const oldType = oldChange.type;
              if (type == Change.CHILD_ADDED && oldType == Change.CHILD_REMOVED) {
                  this.changeMap_[childKey] = Change.childChangedChange(childKey, change.snapshotNode, oldChange.snapshotNode);
              }
              else if (type == Change.CHILD_REMOVED &&
                  oldType == Change.CHILD_ADDED) {
                  delete this.changeMap_[childKey];
              }
              else if (type == Change.CHILD_REMOVED &&
                  oldType == Change.CHILD_CHANGED) {
                  this.changeMap_[childKey] = Change.childRemovedChange(childKey, oldChange.oldSnap);
              }
              else if (type == Change.CHILD_CHANGED &&
                  oldType == Change.CHILD_ADDED) {
                  this.changeMap_[childKey] = Change.childAddedChange(childKey, change.snapshotNode);
              }
              else if (type == Change.CHILD_CHANGED &&
                  oldType == Change.CHILD_CHANGED) {
                  this.changeMap_[childKey] = Change.childChangedChange(childKey, change.snapshotNode, oldChange.oldSnap);
              }
              else {
                  throw assertionError('Illegal combination of changes: ' +
                      change +
                      ' occurred after ' +
                      oldChange);
              }
          }
          else {
              this.changeMap_[childKey] = change;
          }
      }
      /**
       * @return {!Array.<!Change>}
       */
      getChanges() {
          return getValues(this.changeMap_);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * An implementation of CompleteChildSource that never returns any additional children
   *
   * @private
   * @constructor
   * @implements CompleteChildSource
   */
  class NoCompleteChildSource_ {
      /**
       * @inheritDoc
       */
      getCompleteChild(childKey) {
          return null;
      }
      /**
       * @inheritDoc
       */
      getChildAfterChild(index, child, reverse) {
          return null;
      }
  }
  /**
   * Singleton instance.
   * @const
   * @type {!CompleteChildSource}
   */
  const NO_COMPLETE_CHILD_SOURCE = new NoCompleteChildSource_();
  /**
   * An implementation of CompleteChildSource that uses a WriteTree in addition to any other server data or
   * old event caches available to calculate complete children.
   *
   *
   * @implements CompleteChildSource
   */
  class WriteTreeCompleteChildSource {
      /**
       * @param {!WriteTreeRef} writes_
       * @param {!ViewCache} viewCache_
       * @param {?Node} optCompleteServerCache_
       */
      constructor(writes_, viewCache_, optCompleteServerCache_ = null) {
          this.writes_ = writes_;
          this.viewCache_ = viewCache_;
          this.optCompleteServerCache_ = optCompleteServerCache_;
      }
      /**
       * @inheritDoc
       */
      getCompleteChild(childKey) {
          const node = this.viewCache_.getEventCache();
          if (node.isCompleteForChild(childKey)) {
              return node.getNode().getImmediateChild(childKey);
          }
          else {
              const serverNode = this.optCompleteServerCache_ != null
                  ? new CacheNode(this.optCompleteServerCache_, true, false)
                  : this.viewCache_.getServerCache();
              return this.writes_.calcCompleteChild(childKey, serverNode);
          }
      }
      /**
       * @inheritDoc
       */
      getChildAfterChild(index, child, reverse) {
          const completeServerData = this.optCompleteServerCache_ != null
              ? this.optCompleteServerCache_
              : this.viewCache_.getCompleteServerSnap();
          const nodes = this.writes_.calcIndexedSlice(completeServerData, child, 1, reverse, index);
          if (nodes.length === 0) {
              return null;
          }
          else {
              return nodes[0];
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @constructor
   * @struct
   */
  class ProcessorResult {
      /**
       * @param {!ViewCache} viewCache
       * @param {!Array.<!Change>} changes
       */
      constructor(viewCache, changes) {
          this.viewCache = viewCache;
          this.changes = changes;
      }
  }
  /**
   * @constructor
   */
  class ViewProcessor {
      /**
       * @param {!NodeFilter} filter_
       */
      constructor(filter_) {
          this.filter_ = filter_;
      }
      /**
       * @param {!ViewCache} viewCache
       */
      assertIndexed(viewCache) {
          assert(viewCache
              .getEventCache()
              .getNode()
              .isIndexed(this.filter_.getIndex()), 'Event snap not indexed');
          assert(viewCache
              .getServerCache()
              .getNode()
              .isIndexed(this.filter_.getIndex()), 'Server snap not indexed');
      }
      /**
       * @param {!ViewCache} oldViewCache
       * @param {!Operation} operation
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} completeCache
       * @return {!ProcessorResult}
       */
      applyOperation(oldViewCache, operation, writesCache, completeCache) {
          const accumulator = new ChildChangeAccumulator();
          let newViewCache, filterServerNode;
          if (operation.type === OperationType.OVERWRITE) {
              const overwrite = operation;
              if (overwrite.source.fromUser) {
                  newViewCache = this.applyUserOverwrite_(oldViewCache, overwrite.path, overwrite.snap, writesCache, completeCache, accumulator);
              }
              else {
                  assert(overwrite.source.fromServer, 'Unknown source.');
                  // We filter the node if it's a tagged update or the node has been previously filtered  and the
                  // update is not at the root in which case it is ok (and necessary) to mark the node unfiltered
                  // again
                  filterServerNode =
                      overwrite.source.tagged ||
                          (oldViewCache.getServerCache().isFiltered() &&
                              !overwrite.path.isEmpty());
                  newViewCache = this.applyServerOverwrite_(oldViewCache, overwrite.path, overwrite.snap, writesCache, completeCache, filterServerNode, accumulator);
              }
          }
          else if (operation.type === OperationType.MERGE) {
              const merge = operation;
              if (merge.source.fromUser) {
                  newViewCache = this.applyUserMerge_(oldViewCache, merge.path, merge.children, writesCache, completeCache, accumulator);
              }
              else {
                  assert(merge.source.fromServer, 'Unknown source.');
                  // We filter the node if it's a tagged update or the node has been previously filtered
                  filterServerNode =
                      merge.source.tagged || oldViewCache.getServerCache().isFiltered();
                  newViewCache = this.applyServerMerge_(oldViewCache, merge.path, merge.children, writesCache, completeCache, filterServerNode, accumulator);
              }
          }
          else if (operation.type === OperationType.ACK_USER_WRITE) {
              const ackUserWrite = operation;
              if (!ackUserWrite.revert) {
                  newViewCache = this.ackUserWrite_(oldViewCache, ackUserWrite.path, ackUserWrite.affectedTree, writesCache, completeCache, accumulator);
              }
              else {
                  newViewCache = this.revertUserWrite_(oldViewCache, ackUserWrite.path, writesCache, completeCache, accumulator);
              }
          }
          else if (operation.type === OperationType.LISTEN_COMPLETE) {
              newViewCache = this.listenComplete_(oldViewCache, operation.path, writesCache, accumulator);
          }
          else {
              throw assertionError('Unknown operation type: ' + operation.type);
          }
          const changes = accumulator.getChanges();
          ViewProcessor.maybeAddValueEvent_(oldViewCache, newViewCache, changes);
          return new ProcessorResult(newViewCache, changes);
      }
      /**
       * @param {!ViewCache} oldViewCache
       * @param {!ViewCache} newViewCache
       * @param {!Array.<!Change>} accumulator
       * @private
       */
      static maybeAddValueEvent_(oldViewCache, newViewCache, accumulator) {
          const eventSnap = newViewCache.getEventCache();
          if (eventSnap.isFullyInitialized()) {
              const isLeafOrEmpty = eventSnap.getNode().isLeafNode() || eventSnap.getNode().isEmpty();
              const oldCompleteSnap = oldViewCache.getCompleteEventSnap();
              if (accumulator.length > 0 ||
                  !oldViewCache.getEventCache().isFullyInitialized() ||
                  (isLeafOrEmpty &&
                      !eventSnap
                          .getNode()
                          .equals(/** @type {!Node} */ (oldCompleteSnap))) ||
                  !eventSnap
                      .getNode()
                      .getPriority()
                      .equals(oldCompleteSnap.getPriority())) {
                  accumulator.push(Change.valueChange(
                  /** @type {!Node} */ newViewCache.getCompleteEventSnap()));
              }
          }
      }
      /**
       * @param {!ViewCache} viewCache
       * @param {!Path} changePath
       * @param {!WriteTreeRef} writesCache
       * @param {!CompleteChildSource} source
       * @param {!ChildChangeAccumulator} accumulator
       * @return {!ViewCache}
       * @private
       */
      generateEventCacheAfterServerEvent_(viewCache, changePath, writesCache, source, accumulator) {
          const oldEventSnap = viewCache.getEventCache();
          if (writesCache.shadowingWrite(changePath) != null) {
              // we have a shadowing write, ignore changes
              return viewCache;
          }
          else {
              let newEventCache, serverNode;
              if (changePath.isEmpty()) {
                  // TODO: figure out how this plays with "sliding ack windows"
                  assert(viewCache.getServerCache().isFullyInitialized(), 'If change path is empty, we must have complete server data');
                  if (viewCache.getServerCache().isFiltered()) {
                      // We need to special case this, because we need to only apply writes to complete children, or
                      // we might end up raising events for incomplete children. If the server data is filtered deep
                      // writes cannot be guaranteed to be complete
                      const serverCache = viewCache.getCompleteServerSnap();
                      const completeChildren = serverCache instanceof ChildrenNode
                          ? serverCache
                          : ChildrenNode.EMPTY_NODE;
                      const completeEventChildren = writesCache.calcCompleteEventChildren(completeChildren);
                      newEventCache = this.filter_.updateFullNode(viewCache.getEventCache().getNode(), completeEventChildren, accumulator);
                  }
                  else {
                      const completeNode = writesCache.calcCompleteEventCache(viewCache.getCompleteServerSnap());
                      newEventCache = this.filter_.updateFullNode(viewCache.getEventCache().getNode(), completeNode, accumulator);
                  }
              }
              else {
                  const childKey = changePath.getFront();
                  if (childKey == '.priority') {
                      assert(changePath.getLength() == 1, "Can't have a priority with additional path components");
                      const oldEventNode = oldEventSnap.getNode();
                      serverNode = viewCache.getServerCache().getNode();
                      // we might have overwrites for this priority
                      const updatedPriority = writesCache.calcEventCacheAfterServerOverwrite(changePath, oldEventNode, serverNode);
                      if (updatedPriority != null) {
                          newEventCache = this.filter_.updatePriority(oldEventNode, updatedPriority);
                      }
                      else {
                          // priority didn't change, keep old node
                          newEventCache = oldEventSnap.getNode();
                      }
                  }
                  else {
                      const childChangePath = changePath.popFront();
                      // update child
                      let newEventChild;
                      if (oldEventSnap.isCompleteForChild(childKey)) {
                          serverNode = viewCache.getServerCache().getNode();
                          const eventChildUpdate = writesCache.calcEventCacheAfterServerOverwrite(changePath, oldEventSnap.getNode(), serverNode);
                          if (eventChildUpdate != null) {
                              newEventChild = oldEventSnap
                                  .getNode()
                                  .getImmediateChild(childKey)
                                  .updateChild(childChangePath, eventChildUpdate);
                          }
                          else {
                              // Nothing changed, just keep the old child
                              newEventChild = oldEventSnap
                                  .getNode()
                                  .getImmediateChild(childKey);
                          }
                      }
                      else {
                          newEventChild = writesCache.calcCompleteChild(childKey, viewCache.getServerCache());
                      }
                      if (newEventChild != null) {
                          newEventCache = this.filter_.updateChild(oldEventSnap.getNode(), childKey, newEventChild, childChangePath, source, accumulator);
                      }
                      else {
                          // no complete child available or no change
                          newEventCache = oldEventSnap.getNode();
                      }
                  }
              }
              return viewCache.updateEventSnap(newEventCache, oldEventSnap.isFullyInitialized() || changePath.isEmpty(), this.filter_.filtersNodes());
          }
      }
      /**
       * @param {!ViewCache} oldViewCache
       * @param {!Path} changePath
       * @param {!Node} changedSnap
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} completeCache
       * @param {boolean} filterServerNode
       * @param {!ChildChangeAccumulator} accumulator
       * @return {!ViewCache}
       * @private
       */
      applyServerOverwrite_(oldViewCache, changePath, changedSnap, writesCache, completeCache, filterServerNode, accumulator) {
          const oldServerSnap = oldViewCache.getServerCache();
          let newServerCache;
          const serverFilter = filterServerNode
              ? this.filter_
              : this.filter_.getIndexedFilter();
          if (changePath.isEmpty()) {
              newServerCache = serverFilter.updateFullNode(oldServerSnap.getNode(), changedSnap, null);
          }
          else if (serverFilter.filtersNodes() && !oldServerSnap.isFiltered()) {
              // we want to filter the server node, but we didn't filter the server node yet, so simulate a full update
              const newServerNode = oldServerSnap
                  .getNode()
                  .updateChild(changePath, changedSnap);
              newServerCache = serverFilter.updateFullNode(oldServerSnap.getNode(), newServerNode, null);
          }
          else {
              const childKey = changePath.getFront();
              if (!oldServerSnap.isCompleteForPath(changePath) &&
                  changePath.getLength() > 1) {
                  // We don't update incomplete nodes with updates intended for other listeners
                  return oldViewCache;
              }
              const childChangePath = changePath.popFront();
              const childNode = oldServerSnap.getNode().getImmediateChild(childKey);
              const newChildNode = childNode.updateChild(childChangePath, changedSnap);
              if (childKey == '.priority') {
                  newServerCache = serverFilter.updatePriority(oldServerSnap.getNode(), newChildNode);
              }
              else {
                  newServerCache = serverFilter.updateChild(oldServerSnap.getNode(), childKey, newChildNode, childChangePath, NO_COMPLETE_CHILD_SOURCE, null);
              }
          }
          const newViewCache = oldViewCache.updateServerSnap(newServerCache, oldServerSnap.isFullyInitialized() || changePath.isEmpty(), serverFilter.filtersNodes());
          const source = new WriteTreeCompleteChildSource(writesCache, newViewCache, completeCache);
          return this.generateEventCacheAfterServerEvent_(newViewCache, changePath, writesCache, source, accumulator);
      }
      /**
       * @param {!ViewCache} oldViewCache
       * @param {!Path} changePath
       * @param {!Node} changedSnap
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} completeCache
       * @param {!ChildChangeAccumulator} accumulator
       * @return {!ViewCache}
       * @private
       */
      applyUserOverwrite_(oldViewCache, changePath, changedSnap, writesCache, completeCache, accumulator) {
          const oldEventSnap = oldViewCache.getEventCache();
          let newViewCache, newEventCache;
          const source = new WriteTreeCompleteChildSource(writesCache, oldViewCache, completeCache);
          if (changePath.isEmpty()) {
              newEventCache = this.filter_.updateFullNode(oldViewCache.getEventCache().getNode(), changedSnap, accumulator);
              newViewCache = oldViewCache.updateEventSnap(newEventCache, true, this.filter_.filtersNodes());
          }
          else {
              const childKey = changePath.getFront();
              if (childKey === '.priority') {
                  newEventCache = this.filter_.updatePriority(oldViewCache.getEventCache().getNode(), changedSnap);
                  newViewCache = oldViewCache.updateEventSnap(newEventCache, oldEventSnap.isFullyInitialized(), oldEventSnap.isFiltered());
              }
              else {
                  const childChangePath = changePath.popFront();
                  const oldChild = oldEventSnap.getNode().getImmediateChild(childKey);
                  let newChild;
                  if (childChangePath.isEmpty()) {
                      // Child overwrite, we can replace the child
                      newChild = changedSnap;
                  }
                  else {
                      const childNode = source.getCompleteChild(childKey);
                      if (childNode != null) {
                          if (childChangePath.getBack() === '.priority' &&
                              childNode.getChild(childChangePath.parent()).isEmpty()) {
                              // This is a priority update on an empty node. If this node exists on the server, the
                              // server will send down the priority in the update, so ignore for now
                              newChild = childNode;
                          }
                          else {
                              newChild = childNode.updateChild(childChangePath, changedSnap);
                          }
                      }
                      else {
                          // There is no complete child node available
                          newChild = ChildrenNode.EMPTY_NODE;
                      }
                  }
                  if (!oldChild.equals(newChild)) {
                      const newEventSnap = this.filter_.updateChild(oldEventSnap.getNode(), childKey, newChild, childChangePath, source, accumulator);
                      newViewCache = oldViewCache.updateEventSnap(newEventSnap, oldEventSnap.isFullyInitialized(), this.filter_.filtersNodes());
                  }
                  else {
                      newViewCache = oldViewCache;
                  }
              }
          }
          return newViewCache;
      }
      /**
       * @param {!ViewCache} viewCache
       * @param {string} childKey
       * @return {boolean}
       * @private
       */
      static cacheHasChild_(viewCache, childKey) {
          return viewCache.getEventCache().isCompleteForChild(childKey);
      }
      /**
       * @param {!ViewCache} viewCache
       * @param {!Path} path
       * @param {ImmutableTree.<!Node>} changedChildren
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} serverCache
       * @param {!ChildChangeAccumulator} accumulator
       * @return {!ViewCache}
       * @private
       */
      applyUserMerge_(viewCache, path, changedChildren, writesCache, serverCache, accumulator) {
          // HACK: In the case of a limit query, there may be some changes that bump things out of the
          // window leaving room for new items.  It's important we process these changes first, so we
          // iterate the changes twice, first processing any that affect items currently in view.
          // TODO: I consider an item "in view" if cacheHasChild is true, which checks both the server
          // and event snap.  I'm not sure if this will result in edge cases when a child is in one but
          // not the other.
          let curViewCache = viewCache;
          changedChildren.foreach((relativePath, childNode) => {
              const writePath = path.child(relativePath);
              if (ViewProcessor.cacheHasChild_(viewCache, writePath.getFront())) {
                  curViewCache = this.applyUserOverwrite_(curViewCache, writePath, childNode, writesCache, serverCache, accumulator);
              }
          });
          changedChildren.foreach((relativePath, childNode) => {
              const writePath = path.child(relativePath);
              if (!ViewProcessor.cacheHasChild_(viewCache, writePath.getFront())) {
                  curViewCache = this.applyUserOverwrite_(curViewCache, writePath, childNode, writesCache, serverCache, accumulator);
              }
          });
          return curViewCache;
      }
      /**
       * @param {!Node} node
       * @param {ImmutableTree.<!Node>} merge
       * @return {!Node}
       * @private
       */
      applyMerge_(node, merge) {
          merge.foreach(function (relativePath, childNode) {
              node = node.updateChild(relativePath, childNode);
          });
          return node;
      }
      /**
       * @param {!ViewCache} viewCache
       * @param {!Path} path
       * @param {!ImmutableTree.<!Node>} changedChildren
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} serverCache
       * @param {boolean} filterServerNode
       * @param {!ChildChangeAccumulator} accumulator
       * @return {!ViewCache}
       * @private
       */
      applyServerMerge_(viewCache, path, changedChildren, writesCache, serverCache, filterServerNode, accumulator) {
          // If we don't have a cache yet, this merge was intended for a previously listen in the same location. Ignore it and
          // wait for the complete data update coming soon.
          if (viewCache
              .getServerCache()
              .getNode()
              .isEmpty() &&
              !viewCache.getServerCache().isFullyInitialized()) {
              return viewCache;
          }
          // HACK: In the case of a limit query, there may be some changes that bump things out of the
          // window leaving room for new items.  It's important we process these changes first, so we
          // iterate the changes twice, first processing any that affect items currently in view.
          // TODO: I consider an item "in view" if cacheHasChild is true, which checks both the server
          // and event snap.  I'm not sure if this will result in edge cases when a child is in one but
          // not the other.
          let curViewCache = viewCache;
          let viewMergeTree;
          if (path.isEmpty()) {
              viewMergeTree = changedChildren;
          }
          else {
              viewMergeTree = ImmutableTree.Empty.setTree(path, changedChildren);
          }
          const serverNode = viewCache.getServerCache().getNode();
          viewMergeTree.children.inorderTraversal((childKey, childTree) => {
              if (serverNode.hasChild(childKey)) {
                  const serverChild = viewCache
                      .getServerCache()
                      .getNode()
                      .getImmediateChild(childKey);
                  const newChild = this.applyMerge_(serverChild, childTree);
                  curViewCache = this.applyServerOverwrite_(curViewCache, new Path(childKey), newChild, writesCache, serverCache, filterServerNode, accumulator);
              }
          });
          viewMergeTree.children.inorderTraversal((childKey, childMergeTree) => {
              const isUnknownDeepMerge = !viewCache.getServerCache().isCompleteForChild(childKey) &&
                  childMergeTree.value == null;
              if (!serverNode.hasChild(childKey) && !isUnknownDeepMerge) {
                  const serverChild = viewCache
                      .getServerCache()
                      .getNode()
                      .getImmediateChild(childKey);
                  const newChild = this.applyMerge_(serverChild, childMergeTree);
                  curViewCache = this.applyServerOverwrite_(curViewCache, new Path(childKey), newChild, writesCache, serverCache, filterServerNode, accumulator);
              }
          });
          return curViewCache;
      }
      /**
       * @param {!ViewCache} viewCache
       * @param {!Path} ackPath
       * @param {!ImmutableTree<!boolean>} affectedTree
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} completeCache
       * @param {!ChildChangeAccumulator} accumulator
       * @return {!ViewCache}
       * @private
       */
      ackUserWrite_(viewCache, ackPath, affectedTree, writesCache, completeCache, accumulator) {
          if (writesCache.shadowingWrite(ackPath) != null) {
              return viewCache;
          }
          // Only filter server node if it is currently filtered
          const filterServerNode = viewCache.getServerCache().isFiltered();
          // Essentially we'll just get our existing server cache for the affected paths and re-apply it as a server update
          // now that it won't be shadowed.
          const serverCache = viewCache.getServerCache();
          if (affectedTree.value != null) {
              // This is an overwrite.
              if ((ackPath.isEmpty() && serverCache.isFullyInitialized()) ||
                  serverCache.isCompleteForPath(ackPath)) {
                  return this.applyServerOverwrite_(viewCache, ackPath, serverCache.getNode().getChild(ackPath), writesCache, completeCache, filterServerNode, accumulator);
              }
              else if (ackPath.isEmpty()) {
                  // This is a goofy edge case where we are acking data at this location but don't have full data.  We
                  // should just re-apply whatever we have in our cache as a merge.
                  let changedChildren = ImmutableTree.Empty;
                  serverCache.getNode().forEachChild(KEY_INDEX, function (name, node) {
                      changedChildren = changedChildren.set(new Path(name), node);
                  });
                  return this.applyServerMerge_(viewCache, ackPath, changedChildren, writesCache, completeCache, filterServerNode, accumulator);
              }
              else {
                  return viewCache;
              }
          }
          else {
              // This is a merge.
              let changedChildren = ImmutableTree.Empty;
              affectedTree.foreach(function (mergePath, value) {
                  const serverCachePath = ackPath.child(mergePath);
                  if (serverCache.isCompleteForPath(serverCachePath)) {
                      changedChildren = changedChildren.set(mergePath, serverCache.getNode().getChild(serverCachePath));
                  }
              });
              return this.applyServerMerge_(viewCache, ackPath, changedChildren, writesCache, completeCache, filterServerNode, accumulator);
          }
      }
      /**
       * @param {!ViewCache} viewCache
       * @param {!Path} path
       * @param {!WriteTreeRef} writesCache
       * @param {!ChildChangeAccumulator} accumulator
       * @return {!ViewCache}
       * @private
       */
      listenComplete_(viewCache, path, writesCache, accumulator) {
          const oldServerNode = viewCache.getServerCache();
          const newViewCache = viewCache.updateServerSnap(oldServerNode.getNode(), oldServerNode.isFullyInitialized() || path.isEmpty(), oldServerNode.isFiltered());
          return this.generateEventCacheAfterServerEvent_(newViewCache, path, writesCache, NO_COMPLETE_CHILD_SOURCE, accumulator);
      }
      /**
       * @param {!ViewCache} viewCache
       * @param {!Path} path
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} completeServerCache
       * @param {!ChildChangeAccumulator} accumulator
       * @return {!ViewCache}
       * @private
       */
      revertUserWrite_(viewCache, path, writesCache, completeServerCache, accumulator) {
          let complete;
          if (writesCache.shadowingWrite(path) != null) {
              return viewCache;
          }
          else {
              const source = new WriteTreeCompleteChildSource(writesCache, viewCache, completeServerCache);
              const oldEventCache = viewCache.getEventCache().getNode();
              let newEventCache;
              if (path.isEmpty() || path.getFront() === '.priority') {
                  let newNode;
                  if (viewCache.getServerCache().isFullyInitialized()) {
                      newNode = writesCache.calcCompleteEventCache(viewCache.getCompleteServerSnap());
                  }
                  else {
                      const serverChildren = viewCache.getServerCache().getNode();
                      assert(serverChildren instanceof ChildrenNode, 'serverChildren would be complete if leaf node');
                      newNode = writesCache.calcCompleteEventChildren(serverChildren);
                  }
                  newNode = newNode;
                  newEventCache = this.filter_.updateFullNode(oldEventCache, newNode, accumulator);
              }
              else {
                  const childKey = path.getFront();
                  let newChild = writesCache.calcCompleteChild(childKey, viewCache.getServerCache());
                  if (newChild == null &&
                      viewCache.getServerCache().isCompleteForChild(childKey)) {
                      newChild = oldEventCache.getImmediateChild(childKey);
                  }
                  if (newChild != null) {
                      newEventCache = this.filter_.updateChild(oldEventCache, childKey, newChild, path.popFront(), source, accumulator);
                  }
                  else if (viewCache
                      .getEventCache()
                      .getNode()
                      .hasChild(childKey)) {
                      // No complete child available, delete the existing one, if any
                      newEventCache = this.filter_.updateChild(oldEventCache, childKey, ChildrenNode.EMPTY_NODE, path.popFront(), source, accumulator);
                  }
                  else {
                      newEventCache = oldEventCache;
                  }
                  if (newEventCache.isEmpty() &&
                      viewCache.getServerCache().isFullyInitialized()) {
                      // We might have reverted all child writes. Maybe the old event was a leaf node
                      complete = writesCache.calcCompleteEventCache(viewCache.getCompleteServerSnap());
                      if (complete.isLeafNode()) {
                          newEventCache = this.filter_.updateFullNode(newEventCache, complete, accumulator);
                      }
                  }
              }
              complete =
                  viewCache.getServerCache().isFullyInitialized() ||
                      writesCache.shadowingWrite(Path.Empty) != null;
              return viewCache.updateEventSnap(newEventCache, complete, this.filter_.filtersNodes());
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * An EventGenerator is used to convert "raw" changes (Change) as computed by the
   * CacheDiffer into actual events (Event) that can be raised.  See generateEventsForChanges()
   * for details.
   *
   * @constructor
   */
  class EventGenerator {
      /**
       *
       * @param {!Query} query_
       */
      constructor(query_) {
          this.query_ = query_;
          /**
           * @private
           * @type {!Index}
           */
          this.index_ = this.query_.getQueryParams().getIndex();
      }
      /**
       * Given a set of raw changes (no moved events and prevName not specified yet), and a set of
       * EventRegistrations that should be notified of these changes, generate the actual events to be raised.
       *
       * Notes:
       *  - child_moved events will be synthesized at this time for any child_changed events that affect
       *    our index.
       *  - prevName will be calculated based on the index ordering.
       *
       * @param {!Array.<!Change>} changes
       * @param {!Node} eventCache
       * @param {!Array.<!EventRegistration>} eventRegistrations
       * @return {!Array.<!Event>}
       */
      generateEventsForChanges(changes, eventCache, eventRegistrations) {
          const events = [];
          const moves = [];
          changes.forEach(change => {
              if (change.type === Change.CHILD_CHANGED &&
                  this.index_.indexedValueChanged(change.oldSnap, change.snapshotNode)) {
                  moves.push(Change.childMovedChange(change.childName, change.snapshotNode));
              }
          });
          this.generateEventsForType_(events, Change.CHILD_REMOVED, changes, eventRegistrations, eventCache);
          this.generateEventsForType_(events, Change.CHILD_ADDED, changes, eventRegistrations, eventCache);
          this.generateEventsForType_(events, Change.CHILD_MOVED, moves, eventRegistrations, eventCache);
          this.generateEventsForType_(events, Change.CHILD_CHANGED, changes, eventRegistrations, eventCache);
          this.generateEventsForType_(events, Change.VALUE, changes, eventRegistrations, eventCache);
          return events;
      }
      /**
       * Given changes of a single change type, generate the corresponding events.
       *
       * @param {!Array.<!Event>} events
       * @param {!string} eventType
       * @param {!Array.<!Change>} changes
       * @param {!Array.<!EventRegistration>} registrations
       * @param {!Node} eventCache
       * @private
       */
      generateEventsForType_(events, eventType, changes, registrations, eventCache) {
          const filteredChanges = changes.filter(change => change.type === eventType);
          filteredChanges.sort(this.compareChanges_.bind(this));
          filteredChanges.forEach(change => {
              const materializedChange = this.materializeSingleChange_(change, eventCache);
              registrations.forEach(registration => {
                  if (registration.respondsTo(change.type)) {
                      events.push(registration.createEvent(materializedChange, this.query_));
                  }
              });
          });
      }
      /**
       * @param {!Change} change
       * @param {!Node} eventCache
       * @return {!Change}
       * @private
       */
      materializeSingleChange_(change, eventCache) {
          if (change.type === 'value' || change.type === 'child_removed') {
              return change;
          }
          else {
              change.prevName = eventCache.getPredecessorChildName(
              /** @type {!string} */
              change.childName, change.snapshotNode, this.index_);
              return change;
          }
      }
      /**
       * @param {!Change} a
       * @param {!Change} b
       * @return {number}
       * @private
       */
      compareChanges_(a, b) {
          if (a.childName == null || b.childName == null) {
              throw assertionError('Should only compare child_ events.');
          }
          const aWrapped = new NamedNode(a.childName, a.snapshotNode);
          const bWrapped = new NamedNode(b.childName, b.snapshotNode);
          return this.index_.compare(aWrapped, bWrapped);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * A view represents a specific location and query that has 1 or more event registrations.
   *
   * It does several things:
   *  - Maintains the list of event registrations for this location/query.
   *  - Maintains a cache of the data visible for this location/query.
   *  - Applies new operations (via applyOperation), updates the cache, and based on the event
   *    registrations returns the set of events to be raised.
   * @constructor
   */
  class View {
      /**
       *
       * @param {!Query} query_
       * @param {!ViewCache} initialViewCache
       */
      constructor(query_, initialViewCache) {
          this.query_ = query_;
          this.eventRegistrations_ = [];
          const params = this.query_.getQueryParams();
          const indexFilter = new IndexedFilter(params.getIndex());
          const filter = params.getNodeFilter();
          /**
           * @type {ViewProcessor}
           * @private
           */
          this.processor_ = new ViewProcessor(filter);
          const initialServerCache = initialViewCache.getServerCache();
          const initialEventCache = initialViewCache.getEventCache();
          // Don't filter server node with other filter than index, wait for tagged listen
          const serverSnap = indexFilter.updateFullNode(ChildrenNode.EMPTY_NODE, initialServerCache.getNode(), null);
          const eventSnap = filter.updateFullNode(ChildrenNode.EMPTY_NODE, initialEventCache.getNode(), null);
          const newServerCache = new CacheNode(serverSnap, initialServerCache.isFullyInitialized(), indexFilter.filtersNodes());
          const newEventCache = new CacheNode(eventSnap, initialEventCache.isFullyInitialized(), filter.filtersNodes());
          /**
           * @type {!ViewCache}
           * @private
           */
          this.viewCache_ = new ViewCache(newEventCache, newServerCache);
          /**
           * @type {!EventGenerator}
           * @private
           */
          this.eventGenerator_ = new EventGenerator(this.query_);
      }
      /**
       * @return {!Query}
       */
      getQuery() {
          return this.query_;
      }
      /**
       * @return {?Node}
       */
      getServerCache() {
          return this.viewCache_.getServerCache().getNode();
      }
      /**
       * @param {!Path} path
       * @return {?Node}
       */
      getCompleteServerCache(path) {
          const cache = this.viewCache_.getCompleteServerSnap();
          if (cache) {
              // If this isn't a "loadsAllData" view, then cache isn't actually a complete cache and
              // we need to see if it contains the child we're interested in.
              if (this.query_.getQueryParams().loadsAllData() ||
                  (!path.isEmpty() && !cache.getImmediateChild(path.getFront()).isEmpty())) {
                  return cache.getChild(path);
              }
          }
          return null;
      }
      /**
       * @return {boolean}
       */
      isEmpty() {
          return this.eventRegistrations_.length === 0;
      }
      /**
       * @param {!EventRegistration} eventRegistration
       */
      addEventRegistration(eventRegistration) {
          this.eventRegistrations_.push(eventRegistration);
      }
      /**
       * @param {?EventRegistration} eventRegistration If null, remove all callbacks.
       * @param {Error=} cancelError If a cancelError is provided, appropriate cancel events will be returned.
       * @return {!Array.<!Event>} Cancel events, if cancelError was provided.
       */
      removeEventRegistration(eventRegistration, cancelError) {
          const cancelEvents = [];
          if (cancelError) {
              assert(eventRegistration == null, 'A cancel should cancel all event registrations.');
              const path = this.query_.path;
              this.eventRegistrations_.forEach(function (registration) {
                  cancelError /** @type {!Error} */ = cancelError;
                  const maybeEvent = registration.createCancelEvent(cancelError, path);
                  if (maybeEvent) {
                      cancelEvents.push(maybeEvent);
                  }
              });
          }
          if (eventRegistration) {
              let remaining = [];
              for (let i = 0; i < this.eventRegistrations_.length; ++i) {
                  const existing = this.eventRegistrations_[i];
                  if (!existing.matches(eventRegistration)) {
                      remaining.push(existing);
                  }
                  else if (eventRegistration.hasAnyCallback()) {
                      // We're removing just this one
                      remaining = remaining.concat(this.eventRegistrations_.slice(i + 1));
                      break;
                  }
              }
              this.eventRegistrations_ = remaining;
          }
          else {
              this.eventRegistrations_ = [];
          }
          return cancelEvents;
      }
      /**
       * Applies the given Operation, updates our cache, and returns the appropriate events.
       *
       * @param {!Operation} operation
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} completeServerCache
       * @return {!Array.<!Event>}
       */
      applyOperation(operation, writesCache, completeServerCache) {
          if (operation.type === OperationType.MERGE &&
              operation.source.queryId !== null) {
              assert(this.viewCache_.getCompleteServerSnap(), 'We should always have a full cache before handling merges');
              assert(this.viewCache_.getCompleteEventSnap(), 'Missing event cache, even though we have a server cache');
          }
          const oldViewCache = this.viewCache_;
          const result = this.processor_.applyOperation(oldViewCache, operation, writesCache, completeServerCache);
          this.processor_.assertIndexed(result.viewCache);
          assert(result.viewCache.getServerCache().isFullyInitialized() ||
              !oldViewCache.getServerCache().isFullyInitialized(), 'Once a server snap is complete, it should never go back');
          this.viewCache_ = result.viewCache;
          return this.generateEventsForChanges_(result.changes, result.viewCache.getEventCache().getNode(), null);
      }
      /**
       * @param {!EventRegistration} registration
       * @return {!Array.<!Event>}
       */
      getInitialEvents(registration) {
          const eventSnap = this.viewCache_.getEventCache();
          const initialChanges = [];
          if (!eventSnap.getNode().isLeafNode()) {
              const eventNode = eventSnap.getNode();
              eventNode.forEachChild(PRIORITY_INDEX, function (key, childNode) {
                  initialChanges.push(Change.childAddedChange(key, childNode));
              });
          }
          if (eventSnap.isFullyInitialized()) {
              initialChanges.push(Change.valueChange(eventSnap.getNode()));
          }
          return this.generateEventsForChanges_(initialChanges, eventSnap.getNode(), registration);
      }
      /**
       * @private
       * @param {!Array.<!Change>} changes
       * @param {!Node} eventCache
       * @param {EventRegistration=} eventRegistration
       * @return {!Array.<!Event>}
       */
      generateEventsForChanges_(changes, eventCache, eventRegistration) {
          const registrations = eventRegistration
              ? [eventRegistration]
              : this.eventRegistrations_;
          return this.eventGenerator_.generateEventsForChanges(changes, eventCache, registrations);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  let __referenceConstructor$1;
  /**
   * SyncPoint represents a single location in a SyncTree with 1 or more event registrations, meaning we need to
   * maintain 1 or more Views at this location to cache server data and raise appropriate events for server changes
   * and user writes (set, transaction, update).
   *
   * It's responsible for:
   *  - Maintaining the set of 1 or more views necessary at this location (a SyncPoint with 0 views should be removed).
   *  - Proxying user / server operations to the views as appropriate (i.e. applyServerOverwrite,
   *    applyUserOverwrite, etc.)
   */
  class SyncPoint {
      constructor() {
          /**
           * The Views being tracked at this location in the tree, stored as a map where the key is a
           * queryId and the value is the View for that query.
           *
           * NOTE: This list will be quite small (usually 1, but perhaps 2 or 3; any more is an odd use case).
           *
           * @type {!Object.<!string, !View>}
           * @private
           */
          this.views_ = {};
      }
      static set __referenceConstructor(val) {
          assert(!__referenceConstructor$1, '__referenceConstructor has already been defined');
          __referenceConstructor$1 = val;
      }
      static get __referenceConstructor() {
          assert(__referenceConstructor$1, 'Reference.ts has not been loaded');
          return __referenceConstructor$1;
      }
      /**
       * @return {boolean}
       */
      isEmpty() {
          return isEmpty(this.views_);
      }
      /**
       *
       * @param {!Operation} operation
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} optCompleteServerCache
       * @return {!Array.<!Event>}
       */
      applyOperation(operation, writesCache, optCompleteServerCache) {
          const queryId = operation.source.queryId;
          if (queryId !== null) {
              const view = safeGet(this.views_, queryId);
              assert(view != null, 'SyncTree gave us an op for an invalid query.');
              return view.applyOperation(operation, writesCache, optCompleteServerCache);
          }
          else {
              let events = [];
              forEach(this.views_, function (key, view) {
                  events = events.concat(view.applyOperation(operation, writesCache, optCompleteServerCache));
              });
              return events;
          }
      }
      /**
       * Add an event callback for the specified query.
       *
       * @param {!Query} query
       * @param {!EventRegistration} eventRegistration
       * @param {!WriteTreeRef} writesCache
       * @param {?Node} serverCache Complete server cache, if we have it.
       * @param {boolean} serverCacheComplete
       * @return {!Array.<!Event>} Events to raise.
       */
      addEventRegistration(query, eventRegistration, writesCache, serverCache, serverCacheComplete) {
          const queryId = query.queryIdentifier();
          let view = safeGet(this.views_, queryId);
          if (!view) {
              // TODO: make writesCache take flag for complete server node
              let eventCache = writesCache.calcCompleteEventCache(serverCacheComplete ? serverCache : null);
              let eventCacheComplete = false;
              if (eventCache) {
                  eventCacheComplete = true;
              }
              else if (serverCache instanceof ChildrenNode) {
                  eventCache = writesCache.calcCompleteEventChildren(serverCache);
                  eventCacheComplete = false;
              }
              else {
                  eventCache = ChildrenNode.EMPTY_NODE;
                  eventCacheComplete = false;
              }
              const viewCache = new ViewCache(new CacheNode(
              /** @type {!Node} */ (eventCache), eventCacheComplete, false), new CacheNode(
              /** @type {!Node} */ (serverCache), serverCacheComplete, false));
              view = new View(query, viewCache);
              this.views_[queryId] = view;
          }
          // This is guaranteed to exist now, we just created anything that was missing
          view.addEventRegistration(eventRegistration);
          return view.getInitialEvents(eventRegistration);
      }
      /**
       * Remove event callback(s).  Return cancelEvents if a cancelError is specified.
       *
       * If query is the default query, we'll check all views for the specified eventRegistration.
       * If eventRegistration is null, we'll remove all callbacks for the specified view(s).
       *
       * @param {!Query} query
       * @param {?EventRegistration} eventRegistration If null, remove all callbacks.
       * @param {Error=} cancelError If a cancelError is provided, appropriate cancel events will be returned.
       * @return {{removed:!Array.<!Query>, events:!Array.<!Event>}} removed queries and any cancel events
       */
      removeEventRegistration(query, eventRegistration, cancelError) {
          const queryId = query.queryIdentifier();
          const removed = [];
          let cancelEvents = [];
          const hadCompleteView = this.hasCompleteView();
          if (queryId === 'default') {
              // When you do ref.off(...), we search all views for the registration to remove.
              const self = this;
              forEach(this.views_, function (viewQueryId, view) {
                  cancelEvents = cancelEvents.concat(view.removeEventRegistration(eventRegistration, cancelError));
                  if (view.isEmpty()) {
                      delete self.views_[viewQueryId];
                      // We'll deal with complete views later.
                      if (!view
                          .getQuery()
                          .getQueryParams()
                          .loadsAllData()) {
                          removed.push(view.getQuery());
                      }
                  }
              });
          }
          else {
              // remove the callback from the specific view.
              const view = safeGet(this.views_, queryId);
              if (view) {
                  cancelEvents = cancelEvents.concat(view.removeEventRegistration(eventRegistration, cancelError));
                  if (view.isEmpty()) {
                      delete this.views_[queryId];
                      // We'll deal with complete views later.
                      if (!view
                          .getQuery()
                          .getQueryParams()
                          .loadsAllData()) {
                          removed.push(view.getQuery());
                      }
                  }
              }
          }
          if (hadCompleteView && !this.hasCompleteView()) {
              // We removed our last complete view.
              removed.push(new SyncPoint.__referenceConstructor(query.repo, query.path));
          }
          return { removed: removed, events: cancelEvents };
      }
      /**
       * @return {!Array.<!View>}
       */
      getQueryViews() {
          const values = Object.keys(this.views_).map(key => this.views_[key]);
          return values.filter(function (view) {
              return !view
                  .getQuery()
                  .getQueryParams()
                  .loadsAllData();
          });
      }
      /**
       *
       * @param {!Path} path The path to the desired complete snapshot
       * @return {?Node} A complete cache, if it exists
       */
      getCompleteServerCache(path) {
          let serverCache = null;
          forEach(this.views_, (key, view) => {
              serverCache = serverCache || view.getCompleteServerCache(path);
          });
          return serverCache;
      }
      /**
       * @param {!Query} query
       * @return {?View}
       */
      viewForQuery(query) {
          const params = query.getQueryParams();
          if (params.loadsAllData()) {
              return this.getCompleteView();
          }
          else {
              const queryId = query.queryIdentifier();
              return safeGet(this.views_, queryId);
          }
      }
      /**
       * @param {!Query} query
       * @return {boolean}
       */
      viewExistsForQuery(query) {
          return this.viewForQuery(query) != null;
      }
      /**
       * @return {boolean}
       */
      hasCompleteView() {
          return this.getCompleteView() != null;
      }
      /**
       * @return {?View}
       */
      getCompleteView() {
          const completeView = findValue(this.views_, (view) => view
              .getQuery()
              .getQueryParams()
              .loadsAllData());
          return completeView || null;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * This class holds a collection of writes that can be applied to nodes in unison. It abstracts away the logic with
   * dealing with priority writes and multiple nested writes. At any given path there is only allowed to be one write
   * modifying that path. Any write to an existing path or shadowing an existing path will modify that existing write
   * to reflect the write added.
   *
   * @constructor
   * @param {!ImmutableTree.<!Node>} writeTree
   */
  class CompoundWrite {
      constructor(writeTree_) {
          this.writeTree_ = writeTree_;
      }
      /**
       * @param {!Path} path
       * @param {!Node} node
       * @return {!CompoundWrite}
       */
      addWrite(path, node) {
          if (path.isEmpty()) {
              return new CompoundWrite(new ImmutableTree(node));
          }
          else {
              const rootmost = this.writeTree_.findRootMostValueAndPath(path);
              if (rootmost != null) {
                  const rootMostPath = rootmost.path;
                  let value = rootmost.value;
                  const relativePath = Path.relativePath(rootMostPath, path);
                  value = value.updateChild(relativePath, node);
                  return new CompoundWrite(this.writeTree_.set(rootMostPath, value));
              }
              else {
                  const subtree = new ImmutableTree(node);
                  const newWriteTree = this.writeTree_.setTree(path, subtree);
                  return new CompoundWrite(newWriteTree);
              }
          }
      }
      /**
       * @param {!Path} path
       * @param {!Object.<string, !Node>} updates
       * @return {!CompoundWrite}
       */
      addWrites(path, updates) {
          let newWrite = this;
          forEach(updates, function (childKey, node) {
              newWrite = newWrite.addWrite(path.child(childKey), node);
          });
          return newWrite;
      }
      /**
       * Will remove a write at the given path and deeper paths. This will <em>not</em> modify a write at a higher
       * location, which must be removed by calling this method with that path.
       *
       * @param {!Path} path The path at which a write and all deeper writes should be removed
       * @return {!CompoundWrite} The new CompoundWrite with the removed path
       */
      removeWrite(path) {
          if (path.isEmpty()) {
              return CompoundWrite.Empty;
          }
          else {
              const newWriteTree = this.writeTree_.setTree(path, ImmutableTree.Empty);
              return new CompoundWrite(newWriteTree);
          }
      }
      /**
       * Returns whether this CompoundWrite will fully overwrite a node at a given location and can therefore be
       * considered "complete".
       *
       * @param {!Path} path The path to check for
       * @return {boolean} Whether there is a complete write at that path
       */
      hasCompleteWrite(path) {
          return this.getCompleteNode(path) != null;
      }
      /**
       * Returns a node for a path if and only if the node is a "complete" overwrite at that path. This will not aggregate
       * writes from deeper paths, but will return child nodes from a more shallow path.
       *
       * @param {!Path} path The path to get a complete write
       * @return {?Node} The node if complete at that path, or null otherwise.
       */
      getCompleteNode(path) {
          const rootmost = this.writeTree_.findRootMostValueAndPath(path);
          if (rootmost != null) {
              return this.writeTree_
                  .get(rootmost.path)
                  .getChild(Path.relativePath(rootmost.path, path));
          }
          else {
              return null;
          }
      }
      /**
       * Returns all children that are guaranteed to be a complete overwrite.
       *
       * @return {!Array.<NamedNode>} A list of all complete children.
       */
      getCompleteChildren() {
          const children = [];
          let node = this.writeTree_.value;
          if (node != null) {
              // If it's a leaf node, it has no children; so nothing to do.
              if (!node.isLeafNode()) {
                  node.forEachChild(PRIORITY_INDEX, function (childName, childNode) {
                      children.push(new NamedNode(childName, childNode));
                  });
              }
          }
          else {
              this.writeTree_.children.inorderTraversal(function (childName, childTree) {
                  if (childTree.value != null) {
                      children.push(new NamedNode(childName, childTree.value));
                  }
              });
          }
          return children;
      }
      /**
       * @param {!Path} path
       * @return {!CompoundWrite}
       */
      childCompoundWrite(path) {
          if (path.isEmpty()) {
              return this;
          }
          else {
              const shadowingNode = this.getCompleteNode(path);
              if (shadowingNode != null) {
                  return new CompoundWrite(new ImmutableTree(shadowingNode));
              }
              else {
                  return new CompoundWrite(this.writeTree_.subtree(path));
              }
          }
      }
      /**
       * Returns true if this CompoundWrite is empty and therefore does not modify any nodes.
       * @return {boolean} Whether this CompoundWrite is empty
       */
      isEmpty() {
          return this.writeTree_.isEmpty();
      }
      /**
       * Applies this CompoundWrite to a node. The node is returned with all writes from this CompoundWrite applied to the
       * node
       * @param {!Node} node The node to apply this CompoundWrite to
       * @return {!Node} The node with all writes applied
       */
      apply(node) {
          return CompoundWrite.applySubtreeWrite_(Path.Empty, this.writeTree_, node);
      }
  }
  /**
   * @type {!CompoundWrite}
   */
  CompoundWrite.Empty = new CompoundWrite(new ImmutableTree(null));
  /**
   * @param {!Path} relativePath
   * @param {!ImmutableTree.<!Node>} writeTree
   * @param {!Node} node
   * @return {!Node}
   * @private
   */
  CompoundWrite.applySubtreeWrite_ = function (relativePath, writeTree, node) {
      if (writeTree.value != null) {
          // Since there a write is always a leaf, we're done here
          return node.updateChild(relativePath, writeTree.value);
      }
      else {
          let priorityWrite = null;
          writeTree.children.inorderTraversal(function (childKey, childTree) {
              if (childKey === '.priority') {
                  // Apply priorities at the end so we don't update priorities for either empty nodes or forget
                  // to apply priorities to empty nodes that are later filled
                  assert(childTree.value !== null, 'Priority writes must always be leaf nodes');
                  priorityWrite = childTree.value;
              }
              else {
                  node = CompoundWrite.applySubtreeWrite_(relativePath.child(childKey), childTree, node);
              }
          });
          // If there was a priority write, we only apply it if the node is not empty
          if (!node.getChild(relativePath).isEmpty() && priorityWrite !== null) {
              node = node.updateChild(relativePath.child('.priority'), priorityWrite);
          }
          return node;
      }
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * WriteTree tracks all pending user-initiated writes and has methods to calculate the result of merging them
   * with underlying server data (to create "event cache" data).  Pending writes are added with addOverwrite()
   * and addMerge(), and removed with removeWrite().
   *
   * @constructor
   */
  class WriteTree {
      constructor() {
          /**
           * A tree tracking the result of applying all visible writes.  This does not include transactions with
           * applyLocally=false or writes that are completely shadowed by other writes.
           *
           * @type {!CompoundWrite}
           * @private
           */
          this.visibleWrites_ = CompoundWrite.Empty;
          /**
           * A list of all pending writes, regardless of visibility and shadowed-ness.  Used to calculate arbitrary
           * sets of the changed data, such as hidden writes (from transactions) or changes with certain writes excluded (also
           * used by transactions).
           *
           * @type {!Array.<!WriteRecord>}
           * @private
           */
          this.allWrites_ = [];
          this.lastWriteId_ = -1;
      }
      /**
       * Create a new WriteTreeRef for the given path. For use with a new sync point at the given path.
       *
       * @param {!Path} path
       * @return {!WriteTreeRef}
       */
      childWrites(path) {
          return new WriteTreeRef(path, this);
      }
      /**
       * Record a new overwrite from user code.
       *
       * @param {!Path} path
       * @param {!Node} snap
       * @param {!number} writeId
       * @param {boolean=} visible This is set to false by some transactions. It should be excluded from event caches
       */
      addOverwrite(path, snap, writeId, visible) {
          assert(writeId > this.lastWriteId_, 'Stacking an older write on top of newer ones');
          if (visible === undefined) {
              visible = true;
          }
          this.allWrites_.push({
              path: path,
              snap: snap,
              writeId: writeId,
              visible: visible
          });
          if (visible) {
              this.visibleWrites_ = this.visibleWrites_.addWrite(path, snap);
          }
          this.lastWriteId_ = writeId;
      }
      /**
       * Record a new merge from user code.
       *
       * @param {!Path} path
       * @param {!Object.<string, !Node>} changedChildren
       * @param {!number} writeId
       */
      addMerge(path, changedChildren, writeId) {
          assert(writeId > this.lastWriteId_, 'Stacking an older merge on top of newer ones');
          this.allWrites_.push({
              path: path,
              children: changedChildren,
              writeId: writeId,
              visible: true
          });
          this.visibleWrites_ = this.visibleWrites_.addWrites(path, changedChildren);
          this.lastWriteId_ = writeId;
      }
      /**
       * @param {!number} writeId
       * @return {?WriteRecord}
       */
      getWrite(writeId) {
          for (let i = 0; i < this.allWrites_.length; i++) {
              const record = this.allWrites_[i];
              if (record.writeId === writeId) {
                  return record;
              }
          }
          return null;
      }
      /**
       * Remove a write (either an overwrite or merge) that has been successfully acknowledge by the server. Recalculates
       * the tree if necessary.  We return true if it may have been visible, meaning views need to reevaluate.
       *
       * @param {!number} writeId
       * @return {boolean} true if the write may have been visible (meaning we'll need to reevaluate / raise
       * events as a result).
       */
      removeWrite(writeId) {
          // Note: disabling this check. It could be a transaction that preempted another transaction, and thus was applied
          // out of order.
          //const validClear = revert || this.allWrites_.length === 0 || writeId <= this.allWrites_[0].writeId;
          //assert(validClear, "Either we don't have this write, or it's the first one in the queue");
          const idx = this.allWrites_.findIndex(function (s) {
              return s.writeId === writeId;
          });
          assert(idx >= 0, 'removeWrite called with nonexistent writeId.');
          const writeToRemove = this.allWrites_[idx];
          this.allWrites_.splice(idx, 1);
          let removedWriteWasVisible = writeToRemove.visible;
          let removedWriteOverlapsWithOtherWrites = false;
          let i = this.allWrites_.length - 1;
          while (removedWriteWasVisible && i >= 0) {
              const currentWrite = this.allWrites_[i];
              if (currentWrite.visible) {
                  if (i >= idx &&
                      this.recordContainsPath_(currentWrite, writeToRemove.path)) {
                      // The removed write was completely shadowed by a subsequent write.
                      removedWriteWasVisible = false;
                  }
                  else if (writeToRemove.path.contains(currentWrite.path)) {
                      // Either we're covering some writes or they're covering part of us (depending on which came first).
                      removedWriteOverlapsWithOtherWrites = true;
                  }
              }
              i--;
          }
          if (!removedWriteWasVisible) {
              return false;
          }
          else if (removedWriteOverlapsWithOtherWrites) {
              // There's some shadowing going on. Just rebuild the visible writes from scratch.
              this.resetTree_();
              return true;
          }
          else {
              // There's no shadowing.  We can safely just remove the write(s) from visibleWrites.
              if (writeToRemove.snap) {
                  this.visibleWrites_ = this.visibleWrites_.removeWrite(writeToRemove.path);
              }
              else {
                  const children = writeToRemove.children;
                  forEach(children, (childName) => {
                      this.visibleWrites_ = this.visibleWrites_.removeWrite(writeToRemove.path.child(childName));
                  });
              }
              return true;
          }
      }
      /**
       * Return a complete snapshot for the given path if there's visible write data at that path, else null.
       * No server data is considered.
       *
       * @param {!Path} path
       * @return {?Node}
       */
      getCompleteWriteData(path) {
          return this.visibleWrites_.getCompleteNode(path);
      }
      /**
       * Given optional, underlying server data, and an optional set of constraints (exclude some sets, include hidden
       * writes), attempt to calculate a complete snapshot for the given path
       *
       * @param {!Path} treePath
       * @param {?Node} completeServerCache
       * @param {Array.<number>=} writeIdsToExclude An optional set to be excluded
       * @param {boolean=} includeHiddenWrites Defaults to false, whether or not to layer on writes with visible set to false
       * @return {?Node}
       */
      calcCompleteEventCache(treePath, completeServerCache, writeIdsToExclude, includeHiddenWrites) {
          if (!writeIdsToExclude && !includeHiddenWrites) {
              const shadowingNode = this.visibleWrites_.getCompleteNode(treePath);
              if (shadowingNode != null) {
                  return shadowingNode;
              }
              else {
                  const subMerge = this.visibleWrites_.childCompoundWrite(treePath);
                  if (subMerge.isEmpty()) {
                      return completeServerCache;
                  }
                  else if (completeServerCache == null &&
                      !subMerge.hasCompleteWrite(Path.Empty)) {
                      // We wouldn't have a complete snapshot, since there's no underlying data and no complete shadow
                      return null;
                  }
                  else {
                      const layeredCache = completeServerCache || ChildrenNode.EMPTY_NODE;
                      return subMerge.apply(layeredCache);
                  }
              }
          }
          else {
              const merge = this.visibleWrites_.childCompoundWrite(treePath);
              if (!includeHiddenWrites && merge.isEmpty()) {
                  return completeServerCache;
              }
              else {
                  // If the server cache is null, and we don't have a complete cache, we need to return null
                  if (!includeHiddenWrites &&
                      completeServerCache == null &&
                      !merge.hasCompleteWrite(Path.Empty)) {
                      return null;
                  }
                  else {
                      const filter = function (write) {
                          return ((write.visible || includeHiddenWrites) &&
                              (!writeIdsToExclude ||
                                  !~writeIdsToExclude.indexOf(write.writeId)) &&
                              (write.path.contains(treePath) || treePath.contains(write.path)));
                      };
                      const mergeAtPath = WriteTree.layerTree_(this.allWrites_, filter, treePath);
                      const layeredCache = completeServerCache || ChildrenNode.EMPTY_NODE;
                      return mergeAtPath.apply(layeredCache);
                  }
              }
          }
      }
      /**
       * With optional, underlying server data, attempt to return a children node of children that we have complete data for.
       * Used when creating new views, to pre-fill their complete event children snapshot.
       *
       * @param {!Path} treePath
       * @param {?ChildrenNode} completeServerChildren
       * @return {!ChildrenNode}
       */
      calcCompleteEventChildren(treePath, completeServerChildren) {
          let completeChildren = ChildrenNode.EMPTY_NODE;
          const topLevelSet = this.visibleWrites_.getCompleteNode(treePath);
          if (topLevelSet) {
              if (!topLevelSet.isLeafNode()) {
                  // we're shadowing everything. Return the children.
                  topLevelSet.forEachChild(PRIORITY_INDEX, function (childName, childSnap) {
                      completeChildren = completeChildren.updateImmediateChild(childName, childSnap);
                  });
              }
              return completeChildren;
          }
          else if (completeServerChildren) {
              // Layer any children we have on top of this
              // We know we don't have a top-level set, so just enumerate existing children
              const merge = this.visibleWrites_.childCompoundWrite(treePath);
              completeServerChildren.forEachChild(PRIORITY_INDEX, function (childName, childNode) {
                  const node = merge
                      .childCompoundWrite(new Path(childName))
                      .apply(childNode);
                  completeChildren = completeChildren.updateImmediateChild(childName, node);
              });
              // Add any complete children we have from the set
              merge.getCompleteChildren().forEach(function (namedNode) {
                  completeChildren = completeChildren.updateImmediateChild(namedNode.name, namedNode.node);
              });
              return completeChildren;
          }
          else {
              // We don't have anything to layer on top of. Layer on any children we have
              // Note that we can return an empty snap if we have a defined delete
              const merge = this.visibleWrites_.childCompoundWrite(treePath);
              merge.getCompleteChildren().forEach(function (namedNode) {
                  completeChildren = completeChildren.updateImmediateChild(namedNode.name, namedNode.node);
              });
              return completeChildren;
          }
      }
      /**
       * Given that the underlying server data has updated, determine what, if anything, needs to be
       * applied to the event cache.
       *
       * Possibilities:
       *
       * 1. No writes are shadowing. Events should be raised, the snap to be applied comes from the server data
       *
       * 2. Some write is completely shadowing. No events to be raised
       *
       * 3. Is partially shadowed. Events
       *
       * Either existingEventSnap or existingServerSnap must exist
       *
       * @param {!Path} treePath
       * @param {!Path} childPath
       * @param {?Node} existingEventSnap
       * @param {?Node} existingServerSnap
       * @return {?Node}
       */
      calcEventCacheAfterServerOverwrite(treePath, childPath, existingEventSnap, existingServerSnap) {
          assert(existingEventSnap || existingServerSnap, 'Either existingEventSnap or existingServerSnap must exist');
          const path = treePath.child(childPath);
          if (this.visibleWrites_.hasCompleteWrite(path)) {
              // At this point we can probably guarantee that we're in case 2, meaning no events
              // May need to check visibility while doing the findRootMostValueAndPath call
              return null;
          }
          else {
              // No complete shadowing. We're either partially shadowing or not shadowing at all.
              const childMerge = this.visibleWrites_.childCompoundWrite(path);
              if (childMerge.isEmpty()) {
                  // We're not shadowing at all. Case 1
                  return existingServerSnap.getChild(childPath);
              }
              else {
                  // This could be more efficient if the serverNode + updates doesn't change the eventSnap
                  // However this is tricky to find out, since user updates don't necessary change the server
                  // snap, e.g. priority updates on empty nodes, or deep deletes. Another special case is if the server
                  // adds nodes, but doesn't change any existing writes. It is therefore not enough to
                  // only check if the updates change the serverNode.
                  // Maybe check if the merge tree contains these special cases and only do a full overwrite in that case?
                  return childMerge.apply(existingServerSnap.getChild(childPath));
              }
          }
      }
      /**
       * Returns a complete child for a given server snap after applying all user writes or null if there is no
       * complete child for this ChildKey.
       *
       * @param {!Path} treePath
       * @param {!string} childKey
       * @param {!CacheNode} existingServerSnap
       * @return {?Node}
       */
      calcCompleteChild(treePath, childKey, existingServerSnap) {
          const path = treePath.child(childKey);
          const shadowingNode = this.visibleWrites_.getCompleteNode(path);
          if (shadowingNode != null) {
              return shadowingNode;
          }
          else {
              if (existingServerSnap.isCompleteForChild(childKey)) {
                  const childMerge = this.visibleWrites_.childCompoundWrite(path);
                  return childMerge.apply(existingServerSnap.getNode().getImmediateChild(childKey));
              }
              else {
                  return null;
              }
          }
      }
      /**
       * Returns a node if there is a complete overwrite for this path. More specifically, if there is a write at
       * a higher path, this will return the child of that write relative to the write and this path.
       * Returns null if there is no write at this path.
       *
       * @param {!Path} path
       * @return {?Node}
       */
      shadowingWrite(path) {
          return this.visibleWrites_.getCompleteNode(path);
      }
      /**
       * This method is used when processing child remove events on a query. If we can, we pull in children that were outside
       * the window, but may now be in the window.
       *
       * @param {!Path} treePath
       * @param {?Node} completeServerData
       * @param {!NamedNode} startPost
       * @param {!number} count
       * @param {boolean} reverse
       * @param {!Index} index
       * @return {!Array.<!NamedNode>}
       */
      calcIndexedSlice(treePath, completeServerData, startPost, count, reverse, index) {
          let toIterate;
          const merge = this.visibleWrites_.childCompoundWrite(treePath);
          const shadowingNode = merge.getCompleteNode(Path.Empty);
          if (shadowingNode != null) {
              toIterate = shadowingNode;
          }
          else if (completeServerData != null) {
              toIterate = merge.apply(completeServerData);
          }
          else {
              // no children to iterate on
              return [];
          }
          toIterate = toIterate.withIndex(index);
          if (!toIterate.isEmpty() && !toIterate.isLeafNode()) {
              const nodes = [];
              const cmp = index.getCompare();
              const iter = reverse
                  ? toIterate.getReverseIteratorFrom(startPost, index)
                  : toIterate.getIteratorFrom(startPost, index);
              let next = iter.getNext();
              while (next && nodes.length < count) {
                  if (cmp(next, startPost) !== 0) {
                      nodes.push(next);
                  }
                  next = iter.getNext();
              }
              return nodes;
          }
          else {
              return [];
          }
      }
      /**
       * @param {!WriteRecord} writeRecord
       * @param {!Path} path
       * @return {boolean}
       * @private
       */
      recordContainsPath_(writeRecord, path) {
          if (writeRecord.snap) {
              return writeRecord.path.contains(path);
          }
          else {
              // findKey can return undefined, so use !! to coerce to boolean
              return !!findKey(writeRecord.children, function (childSnap, childName) {
                  return writeRecord.path.child(childName).contains(path);
              });
          }
      }
      /**
       * Re-layer the writes and merges into a tree so we can efficiently calculate event snapshots
       * @private
       */
      resetTree_() {
          this.visibleWrites_ = WriteTree.layerTree_(this.allWrites_, WriteTree.DefaultFilter_, Path.Empty);
          if (this.allWrites_.length > 0) {
              this.lastWriteId_ = this.allWrites_[this.allWrites_.length - 1].writeId;
          }
          else {
              this.lastWriteId_ = -1;
          }
      }
      /**
       * The default filter used when constructing the tree. Keep everything that's visible.
       *
       * @param {!WriteRecord} write
       * @return {boolean}
       * @private
       */
      static DefaultFilter_(write) {
          return write.visible;
      }
      /**
       * Static method. Given an array of WriteRecords, a filter for which ones to include, and a path, construct the tree of
       * event data at that path.
       *
       * @param {!Array.<!WriteRecord>} writes
       * @param {!function(!WriteRecord):boolean} filter
       * @param {!Path} treeRoot
       * @return {!CompoundWrite}
       * @private
       */
      static layerTree_(writes, filter, treeRoot) {
          let compoundWrite = CompoundWrite.Empty;
          for (let i = 0; i < writes.length; ++i) {
              const write = writes[i];
              // Theory, a later set will either:
              // a) abort a relevant transaction, so no need to worry about excluding it from calculating that transaction
              // b) not be relevant to a transaction (separate branch), so again will not affect the data for that transaction
              if (filter(write)) {
                  const writePath = write.path;
                  let relativePath;
                  if (write.snap) {
                      if (treeRoot.contains(writePath)) {
                          relativePath = Path.relativePath(treeRoot, writePath);
                          compoundWrite = compoundWrite.addWrite(relativePath, write.snap);
                      }
                      else if (writePath.contains(treeRoot)) {
                          relativePath = Path.relativePath(writePath, treeRoot);
                          compoundWrite = compoundWrite.addWrite(Path.Empty, write.snap.getChild(relativePath));
                      }
                  }
                  else if (write.children) {
                      if (treeRoot.contains(writePath)) {
                          relativePath = Path.relativePath(treeRoot, writePath);
                          compoundWrite = compoundWrite.addWrites(relativePath, write.children);
                      }
                      else if (writePath.contains(treeRoot)) {
                          relativePath = Path.relativePath(writePath, treeRoot);
                          if (relativePath.isEmpty()) {
                              compoundWrite = compoundWrite.addWrites(Path.Empty, write.children);
                          }
                          else {
                              const child = safeGet(write.children, relativePath.getFront());
                              if (child) {
                                  // There exists a child in this node that matches the root path
                                  const deepNode = child.getChild(relativePath.popFront());
                                  compoundWrite = compoundWrite.addWrite(Path.Empty, deepNode);
                              }
                          }
                      }
                  }
                  else {
                      throw assertionError('WriteRecord should have .snap or .children');
                  }
              }
          }
          return compoundWrite;
      }
  }
  /**
   * A WriteTreeRef wraps a WriteTree and a path, for convenient access to a particular subtree.  All of the methods
   * just proxy to the underlying WriteTree.
   *
   * @constructor
   */
  class WriteTreeRef {
      /**
       * @param {!Path} path
       * @param {!WriteTree} writeTree
       */
      constructor(path, writeTree) {
          this.treePath_ = path;
          this.writeTree_ = writeTree;
      }
      /**
       * If possible, returns a complete event cache, using the underlying server data if possible. In addition, can be used
       * to get a cache that includes hidden writes, and excludes arbitrary writes. Note that customizing the returned node
       * can lead to a more expensive calculation.
       *
       * @param {?Node} completeServerCache
       * @param {Array.<number>=} writeIdsToExclude Optional writes to exclude.
       * @param {boolean=} includeHiddenWrites Defaults to false, whether or not to layer on writes with visible set to false
       * @return {?Node}
       */
      calcCompleteEventCache(completeServerCache, writeIdsToExclude, includeHiddenWrites) {
          return this.writeTree_.calcCompleteEventCache(this.treePath_, completeServerCache, writeIdsToExclude, includeHiddenWrites);
      }
      /**
       * If possible, returns a children node containing all of the complete children we have data for. The returned data is a
       * mix of the given server data and write data.
       *
       * @param {?ChildrenNode} completeServerChildren
       * @return {!ChildrenNode}
       */
      calcCompleteEventChildren(completeServerChildren) {
          return this.writeTree_.calcCompleteEventChildren(this.treePath_, completeServerChildren);
      }
      /**
       * Given that either the underlying server data has updated or the outstanding writes have updated, determine what,
       * if anything, needs to be applied to the event cache.
       *
       * Possibilities:
       *
       * 1. No writes are shadowing. Events should be raised, the snap to be applied comes from the server data
       *
       * 2. Some write is completely shadowing. No events to be raised
       *
       * 3. Is partially shadowed. Events should be raised
       *
       * Either existingEventSnap or existingServerSnap must exist, this is validated via an assert
       *
       * @param {!Path} path
       * @param {?Node} existingEventSnap
       * @param {?Node} existingServerSnap
       * @return {?Node}
       */
      calcEventCacheAfterServerOverwrite(path, existingEventSnap, existingServerSnap) {
          return this.writeTree_.calcEventCacheAfterServerOverwrite(this.treePath_, path, existingEventSnap, existingServerSnap);
      }
      /**
       * Returns a node if there is a complete overwrite for this path. More specifically, if there is a write at
       * a higher path, this will return the child of that write relative to the write and this path.
       * Returns null if there is no write at this path.
       *
       * @param {!Path} path
       * @return {?Node}
       */
      shadowingWrite(path) {
          return this.writeTree_.shadowingWrite(this.treePath_.child(path));
      }
      /**
       * This method is used when processing child remove events on a query. If we can, we pull in children that were outside
       * the window, but may now be in the window
       *
       * @param {?Node} completeServerData
       * @param {!NamedNode} startPost
       * @param {!number} count
       * @param {boolean} reverse
       * @param {!Index} index
       * @return {!Array.<!NamedNode>}
       */
      calcIndexedSlice(completeServerData, startPost, count, reverse, index) {
          return this.writeTree_.calcIndexedSlice(this.treePath_, completeServerData, startPost, count, reverse, index);
      }
      /**
       * Returns a complete child for a given server snap after applying all user writes or null if there is no
       * complete child for this ChildKey.
       *
       * @param {!string} childKey
       * @param {!CacheNode} existingServerCache
       * @return {?Node}
       */
      calcCompleteChild(childKey, existingServerCache) {
          return this.writeTree_.calcCompleteChild(this.treePath_, childKey, existingServerCache);
      }
      /**
       * Return a WriteTreeRef for a child.
       *
       * @param {string} childName
       * @return {!WriteTreeRef}
       */
      child(childName) {
          return new WriteTreeRef(this.treePath_.child(childName), this.writeTree_);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * SyncTree is the central class for managing event callback registration, data caching, views
   * (query processing), and event generation.  There are typically two SyncTree instances for
   * each Repo, one for the normal Firebase data, and one for the .info data.
   *
   * It has a number of responsibilities, including:
   *  - Tracking all user event callbacks (registered via addEventRegistration() and removeEventRegistration()).
   *  - Applying and caching data changes for user set(), transaction(), and update() calls
   *    (applyUserOverwrite(), applyUserMerge()).
   *  - Applying and caching data changes for server data changes (applyServerOverwrite(),
   *    applyServerMerge()).
   *  - Generating user-facing events for server and user changes (all of the apply* methods
   *    return the set of events that need to be raised as a result).
   *  - Maintaining the appropriate set of server listens to ensure we are always subscribed
   *    to the correct set of paths and queries to satisfy the current set of user event
   *    callbacks (listens are started/stopped using the provided listenProvider).
   *
   * NOTE: Although SyncTree tracks event callbacks and calculates events to raise, the actual
   * events are returned to the caller rather than raised synchronously.
   *
   * @constructor
   */
  class SyncTree {
      /**
       * @param {!ListenProvider} listenProvider_ Used by SyncTree to start / stop listening
       *   to server data.
       */
      constructor(listenProvider_) {
          this.listenProvider_ = listenProvider_;
          /**
           * Tree of SyncPoints.  There's a SyncPoint at any location that has 1 or more views.
           * @type {!ImmutableTree.<!SyncPoint>}
           * @private
           */
          this.syncPointTree_ = ImmutableTree.Empty;
          /**
           * A tree of all pending user writes (user-initiated set()'s, transaction()'s, update()'s, etc.).
           * @type {!WriteTree}
           * @private
           */
          this.pendingWriteTree_ = new WriteTree();
          this.tagToQueryMap_ = {};
          this.queryToTagMap_ = {};
      }
      /**
       * Apply the data changes for a user-generated set() or transaction() call.
       *
       * @param {!Path} path
       * @param {!Node} newData
       * @param {number} writeId
       * @param {boolean=} visible
       * @return {!Array.<!Event>} Events to raise.
       */
      applyUserOverwrite(path, newData, writeId, visible) {
          // Record pending write.
          this.pendingWriteTree_.addOverwrite(path, newData, writeId, visible);
          if (!visible) {
              return [];
          }
          else {
              return this.applyOperationToSyncPoints_(new Overwrite(OperationSource.User, path, newData));
          }
      }
      /**
       * Apply the data from a user-generated update() call
       *
       * @param {!Path} path
       * @param {!Object.<string, !Node>} changedChildren
       * @param {!number} writeId
       * @return {!Array.<!Event>} Events to raise.
       */
      applyUserMerge(path, changedChildren, writeId) {
          // Record pending merge.
          this.pendingWriteTree_.addMerge(path, changedChildren, writeId);
          const changeTree = ImmutableTree.fromObject(changedChildren);
          return this.applyOperationToSyncPoints_(new Merge(OperationSource.User, path, changeTree));
      }
      /**
       * Acknowledge a pending user write that was previously registered with applyUserOverwrite() or applyUserMerge().
       *
       * @param {!number} writeId
       * @param {boolean=} revert True if the given write failed and needs to be reverted
       * @return {!Array.<!Event>} Events to raise.
       */
      ackUserWrite(writeId, revert = false) {
          const write = this.pendingWriteTree_.getWrite(writeId);
          const needToReevaluate = this.pendingWriteTree_.removeWrite(writeId);
          if (!needToReevaluate) {
              return [];
          }
          else {
              let affectedTree = ImmutableTree.Empty;
              if (write.snap != null) {
                  // overwrite
                  affectedTree = affectedTree.set(Path.Empty, true);
              }
              else {
                  forEach(write.children, function (pathString, node) {
                      affectedTree = affectedTree.set(new Path(pathString), node);
                  });
              }
              return this.applyOperationToSyncPoints_(new AckUserWrite(write.path, affectedTree, revert));
          }
      }
      /**
       * Apply new server data for the specified path..
       *
       * @param {!Path} path
       * @param {!Node} newData
       * @return {!Array.<!Event>} Events to raise.
       */
      applyServerOverwrite(path, newData) {
          return this.applyOperationToSyncPoints_(new Overwrite(OperationSource.Server, path, newData));
      }
      /**
       * Apply new server data to be merged in at the specified path.
       *
       * @param {!Path} path
       * @param {!Object.<string, !Node>} changedChildren
       * @return {!Array.<!Event>} Events to raise.
       */
      applyServerMerge(path, changedChildren) {
          const changeTree = ImmutableTree.fromObject(changedChildren);
          return this.applyOperationToSyncPoints_(new Merge(OperationSource.Server, path, changeTree));
      }
      /**
       * Apply a listen complete for a query
       *
       * @param {!Path} path
       * @return {!Array.<!Event>} Events to raise.
       */
      applyListenComplete(path) {
          return this.applyOperationToSyncPoints_(new ListenComplete(OperationSource.Server, path));
      }
      /**
       * Apply new server data for the specified tagged query.
       *
       * @param {!Path} path
       * @param {!Node} snap
       * @param {!number} tag
       * @return {!Array.<!Event>} Events to raise.
       */
      applyTaggedQueryOverwrite(path, snap, tag) {
          const queryKey = this.queryKeyForTag_(tag);
          if (queryKey != null) {
              const r = SyncTree.parseQueryKey_(queryKey);
              const queryPath = r.path, queryId = r.queryId;
              const relativePath = Path.relativePath(queryPath, path);
              const op = new Overwrite(OperationSource.forServerTaggedQuery(queryId), relativePath, snap);
              return this.applyTaggedOperation_(queryPath, op);
          }
          else {
              // Query must have been removed already
              return [];
          }
      }
      /**
       * Apply server data to be merged in for the specified tagged query.
       *
       * @param {!Path} path
       * @param {!Object.<string, !Node>} changedChildren
       * @param {!number} tag
       * @return {!Array.<!Event>} Events to raise.
       */
      applyTaggedQueryMerge(path, changedChildren, tag) {
          const queryKey = this.queryKeyForTag_(tag);
          if (queryKey) {
              const r = SyncTree.parseQueryKey_(queryKey);
              const queryPath = r.path, queryId = r.queryId;
              const relativePath = Path.relativePath(queryPath, path);
              const changeTree = ImmutableTree.fromObject(changedChildren);
              const op = new Merge(OperationSource.forServerTaggedQuery(queryId), relativePath, changeTree);
              return this.applyTaggedOperation_(queryPath, op);
          }
          else {
              // We've already removed the query. No big deal, ignore the update
              return [];
          }
      }
      /**
       * Apply a listen complete for a tagged query
       *
       * @param {!Path} path
       * @param {!number} tag
       * @return {!Array.<!Event>} Events to raise.
       */
      applyTaggedListenComplete(path, tag) {
          const queryKey = this.queryKeyForTag_(tag);
          if (queryKey) {
              const r = SyncTree.parseQueryKey_(queryKey);
              const queryPath = r.path, queryId = r.queryId;
              const relativePath = Path.relativePath(queryPath, path);
              const op = new ListenComplete(OperationSource.forServerTaggedQuery(queryId), relativePath);
              return this.applyTaggedOperation_(queryPath, op);
          }
          else {
              // We've already removed the query. No big deal, ignore the update
              return [];
          }
      }
      /**
       * Add an event callback for the specified query.
       *
       * @param {!Query} query
       * @param {!EventRegistration} eventRegistration
       * @return {!Array.<!Event>} Events to raise.
       */
      addEventRegistration(query, eventRegistration) {
          const path = query.path;
          let serverCache = null;
          let foundAncestorDefaultView = false;
          // Any covering writes will necessarily be at the root, so really all we need to find is the server cache.
          // Consider optimizing this once there's a better understanding of what actual behavior will be.
          this.syncPointTree_.foreachOnPath(path, function (pathToSyncPoint, sp) {
              const relativePath = Path.relativePath(pathToSyncPoint, path);
              serverCache = serverCache || sp.getCompleteServerCache(relativePath);
              foundAncestorDefaultView =
                  foundAncestorDefaultView || sp.hasCompleteView();
          });
          let syncPoint = this.syncPointTree_.get(path);
          if (!syncPoint) {
              syncPoint = new SyncPoint();
              this.syncPointTree_ = this.syncPointTree_.set(path, syncPoint);
          }
          else {
              foundAncestorDefaultView =
                  foundAncestorDefaultView || syncPoint.hasCompleteView();
              serverCache = serverCache || syncPoint.getCompleteServerCache(Path.Empty);
          }
          let serverCacheComplete;
          if (serverCache != null) {
              serverCacheComplete = true;
          }
          else {
              serverCacheComplete = false;
              serverCache = ChildrenNode.EMPTY_NODE;
              const subtree = this.syncPointTree_.subtree(path);
              subtree.foreachChild(function (childName, childSyncPoint) {
                  const completeCache = childSyncPoint.getCompleteServerCache(Path.Empty);
                  if (completeCache) {
                      serverCache = serverCache.updateImmediateChild(childName, completeCache);
                  }
              });
          }
          const viewAlreadyExists = syncPoint.viewExistsForQuery(query);
          if (!viewAlreadyExists && !query.getQueryParams().loadsAllData()) {
              // We need to track a tag for this query
              const queryKey = SyncTree.makeQueryKey_(query);
              assert(!(queryKey in this.queryToTagMap_), 'View does not exist, but we have a tag');
              const tag = SyncTree.getNextQueryTag_();
              this.queryToTagMap_[queryKey] = tag;
              // Coerce to string to avoid sparse arrays.
              this.tagToQueryMap_['_' + tag] = queryKey;
          }
          const writesCache = this.pendingWriteTree_.childWrites(path);
          let events = syncPoint.addEventRegistration(query, eventRegistration, writesCache, serverCache, serverCacheComplete);
          if (!viewAlreadyExists && !foundAncestorDefaultView) {
              const view /** @type !View */ = syncPoint.viewForQuery(query);
              events = events.concat(this.setupListener_(query, view));
          }
          return events;
      }
      /**
       * Remove event callback(s).
       *
       * If query is the default query, we'll check all queries for the specified eventRegistration.
       * If eventRegistration is null, we'll remove all callbacks for the specified query/queries.
       *
       * @param {!Query} query
       * @param {?EventRegistration} eventRegistration If null, all callbacks are removed.
       * @param {Error=} cancelError If a cancelError is provided, appropriate cancel events will be returned.
       * @return {!Array.<!Event>} Cancel events, if cancelError was provided.
       */
      removeEventRegistration(query, eventRegistration, cancelError) {
          // Find the syncPoint first. Then deal with whether or not it has matching listeners
          const path = query.path;
          const maybeSyncPoint = this.syncPointTree_.get(path);
          let cancelEvents = [];
          // A removal on a default query affects all queries at that location. A removal on an indexed query, even one without
          // other query constraints, does *not* affect all queries at that location. So this check must be for 'default', and
          // not loadsAllData().
          if (maybeSyncPoint &&
              (query.queryIdentifier() === 'default' ||
                  maybeSyncPoint.viewExistsForQuery(query))) {
              /**
               * @type {{removed: !Array.<!Query>, events: !Array.<!Event>}}
               */
              const removedAndEvents = maybeSyncPoint.removeEventRegistration(query, eventRegistration, cancelError);
              if (maybeSyncPoint.isEmpty()) {
                  this.syncPointTree_ = this.syncPointTree_.remove(path);
              }
              const removed = removedAndEvents.removed;
              cancelEvents = removedAndEvents.events;
              // We may have just removed one of many listeners and can short-circuit this whole process
              // We may also not have removed a default listener, in which case all of the descendant listeners should already be
              // properly set up.
              //
              // Since indexed queries can shadow if they don't have other query constraints, check for loadsAllData(), instead of
              // queryId === 'default'
              const removingDefault = -1 !==
                  removed.findIndex(function (query) {
                      return query.getQueryParams().loadsAllData();
                  });
              const covered = this.syncPointTree_.findOnPath(path, function (relativePath, parentSyncPoint) {
                  return parentSyncPoint.hasCompleteView();
              });
              if (removingDefault && !covered) {
                  const subtree = this.syncPointTree_.subtree(path);
                  // There are potentially child listeners. Determine what if any listens we need to send before executing the
                  // removal
                  if (!subtree.isEmpty()) {
                      // We need to fold over our subtree and collect the listeners to send
                      const newViews = this.collectDistinctViewsForSubTree_(subtree);
                      // Ok, we've collected all the listens we need. Set them up.
                      for (let i = 0; i < newViews.length; ++i) {
                          const view = newViews[i], newQuery = view.getQuery();
                          const listener = this.createListenerForView_(view);
                          this.listenProvider_.startListening(SyncTree.queryForListening_(newQuery), this.tagForQuery_(newQuery), listener.hashFn, listener.onComplete);
                      }
                  }
              }
              // If we removed anything and we're not covered by a higher up listen, we need to stop listening on this query
              // The above block has us covered in terms of making sure we're set up on listens lower in the tree.
              // Also, note that if we have a cancelError, it's already been removed at the provider level.
              if (!covered && removed.length > 0 && !cancelError) {
                  // If we removed a default, then we weren't listening on any of the other queries here. Just cancel the one
                  // default. Otherwise, we need to iterate through and cancel each individual query
                  if (removingDefault) {
                      // We don't tag default listeners
                      const defaultTag = null;
                      this.listenProvider_.stopListening(SyncTree.queryForListening_(query), defaultTag);
                  }
                  else {
                      removed.forEach((queryToRemove) => {
                          const tagToRemove = this.queryToTagMap_[SyncTree.makeQueryKey_(queryToRemove)];
                          this.listenProvider_.stopListening(SyncTree.queryForListening_(queryToRemove), tagToRemove);
                      });
                  }
              }
              // Now, clear all of the tags we're tracking for the removed listens
              this.removeTags_(removed);
          }
          return cancelEvents;
      }
      /**
       * Returns a complete cache, if we have one, of the data at a particular path. The location must have a listener above
       * it, but as this is only used by transaction code, that should always be the case anyways.
       *
       * Note: this method will *include* hidden writes from transaction with applyLocally set to false.
       * @param {!Path} path The path to the data we want
       * @param {Array.<number>=} writeIdsToExclude A specific set to be excluded
       * @return {?Node}
       */
      calcCompleteEventCache(path, writeIdsToExclude) {
          const includeHiddenSets = true;
          const writeTree = this.pendingWriteTree_;
          const serverCache = this.syncPointTree_.findOnPath(path, function (pathSoFar, syncPoint) {
              const relativePath = Path.relativePath(pathSoFar, path);
              const serverCache = syncPoint.getCompleteServerCache(relativePath);
              if (serverCache) {
                  return serverCache;
              }
          });
          return writeTree.calcCompleteEventCache(path, serverCache, writeIdsToExclude, includeHiddenSets);
      }
      /**
       * This collapses multiple unfiltered views into a single view, since we only need a single
       * listener for them.
       *
       * @param {!ImmutableTree.<!SyncPoint>} subtree
       * @return {!Array.<!View>}
       * @private
       */
      collectDistinctViewsForSubTree_(subtree) {
          return subtree.fold((relativePath, maybeChildSyncPoint, childMap) => {
              if (maybeChildSyncPoint && maybeChildSyncPoint.hasCompleteView()) {
                  const completeView = maybeChildSyncPoint.getCompleteView();
                  return [completeView];
              }
              else {
                  // No complete view here, flatten any deeper listens into an array
                  let views = [];
                  if (maybeChildSyncPoint) {
                      views = maybeChildSyncPoint.getQueryViews();
                  }
                  forEach(childMap, function (key, childViews) {
                      views = views.concat(childViews);
                  });
                  return views;
              }
          });
      }
      /**
       * @param {!Array.<!Query>} queries
       * @private
       */
      removeTags_(queries) {
          for (let j = 0; j < queries.length; ++j) {
              const removedQuery = queries[j];
              if (!removedQuery.getQueryParams().loadsAllData()) {
                  // We should have a tag for this
                  const removedQueryKey = SyncTree.makeQueryKey_(removedQuery);
                  const removedQueryTag = this.queryToTagMap_[removedQueryKey];
                  delete this.queryToTagMap_[removedQueryKey];
                  delete this.tagToQueryMap_['_' + removedQueryTag];
              }
          }
      }
      /**
       * Normalizes a query to a query we send the server for listening
       * @param {!Query} query
       * @return {!Query} The normalized query
       * @private
       */
      static queryForListening_(query) {
          if (query.getQueryParams().loadsAllData() &&
              !query.getQueryParams().isDefault()) {
              // We treat queries that load all data as default queries
              // Cast is necessary because ref() technically returns Firebase which is actually fb.api.Firebase which inherits
              // from Query
              return /** @type {!Query} */ query.getRef();
          }
          else {
              return query;
          }
      }
      /**
       * For a given new listen, manage the de-duplication of outstanding subscriptions.
       *
       * @param {!Query} query
       * @param {!View} view
       * @return {!Array.<!Event>} This method can return events to support synchronous data sources
       * @private
       */
      setupListener_(query, view) {
          const path = query.path;
          const tag = this.tagForQuery_(query);
          const listener = this.createListenerForView_(view);
          const events = this.listenProvider_.startListening(SyncTree.queryForListening_(query), tag, listener.hashFn, listener.onComplete);
          const subtree = this.syncPointTree_.subtree(path);
          // The root of this subtree has our query. We're here because we definitely need to send a listen for that, but we
          // may need to shadow other listens as well.
          if (tag) {
              assert(!subtree.value.hasCompleteView(), "If we're adding a query, it shouldn't be shadowed");
          }
          else {
              // Shadow everything at or below this location, this is a default listener.
              const queriesToStop = subtree.fold(function (relativePath, maybeChildSyncPoint, childMap) {
                  if (!relativePath.isEmpty() &&
                      maybeChildSyncPoint &&
                      maybeChildSyncPoint.hasCompleteView()) {
                      return [maybeChildSyncPoint.getCompleteView().getQuery()];
                  }
                  else {
                      // No default listener here, flatten any deeper queries into an array
                      let queries = [];
                      if (maybeChildSyncPoint) {
                          queries = queries.concat(maybeChildSyncPoint.getQueryViews().map(view => view.getQuery()));
                      }
                      forEach(childMap, function (key, childQueries) {
                          queries = queries.concat(childQueries);
                      });
                      return queries;
                  }
              });
              for (let i = 0; i < queriesToStop.length; ++i) {
                  const queryToStop = queriesToStop[i];
                  this.listenProvider_.stopListening(SyncTree.queryForListening_(queryToStop), this.tagForQuery_(queryToStop));
              }
          }
          return events;
      }
      /**
       *
       * @param {!View} view
       * @return {{hashFn: function(), onComplete: function(!string, *)}}
       * @private
       */
      createListenerForView_(view) {
          const query = view.getQuery();
          const tag = this.tagForQuery_(query);
          return {
              hashFn: () => {
                  const cache = view.getServerCache() || ChildrenNode.EMPTY_NODE;
                  return cache.hash();
              },
              onComplete: (status) => {
                  if (status === 'ok') {
                      if (tag) {
                          return this.applyTaggedListenComplete(query.path, tag);
                      }
                      else {
                          return this.applyListenComplete(query.path);
                      }
                  }
                  else {
                      // If a listen failed, kill all of the listeners here, not just the one that triggered the error.
                      // Note that this may need to be scoped to just this listener if we change permissions on filtered children
                      const error = errorForServerCode(status, query);
                      return this.removeEventRegistration(query, 
                      /*eventRegistration*/ null, error);
                  }
              }
          };
      }
      /**
       * Given a query, computes a "queryKey" suitable for use in our queryToTagMap_.
       * @private
       * @param {!Query} query
       * @return {string}
       */
      static makeQueryKey_(query) {
          return query.path.toString() + '$' + query.queryIdentifier();
      }
      /**
       * Given a queryKey (created by makeQueryKey), parse it back into a path and queryId.
       * @private
       * @param {!string} queryKey
       * @return {{queryId: !string, path: !Path}}
       */
      static parseQueryKey_(queryKey) {
          const splitIndex = queryKey.indexOf('$');
          assert(splitIndex !== -1 && splitIndex < queryKey.length - 1, 'Bad queryKey.');
          return {
              queryId: queryKey.substr(splitIndex + 1),
              path: new Path(queryKey.substr(0, splitIndex))
          };
      }
      /**
       * Return the query associated with the given tag, if we have one
       * @param {!number} tag
       * @return {?string}
       * @private
       */
      queryKeyForTag_(tag) {
          return this.tagToQueryMap_['_' + tag];
      }
      /**
       * Return the tag associated with the given query.
       * @param {!Query} query
       * @return {?number}
       * @private
       */
      tagForQuery_(query) {
          const queryKey = SyncTree.makeQueryKey_(query);
          return safeGet(this.queryToTagMap_, queryKey);
      }
      /**
       * Static accessor for query tags.
       * @return {number}
       * @private
       */
      static getNextQueryTag_() {
          return SyncTree.nextQueryTag_++;
      }
      /**
       * A helper method to apply tagged operations
       *
       * @param {!Path} queryPath
       * @param {!Operation} operation
       * @return {!Array.<!Event>}
       * @private
       */
      applyTaggedOperation_(queryPath, operation) {
          const syncPoint = this.syncPointTree_.get(queryPath);
          assert(syncPoint, "Missing sync point for query tag that we're tracking");
          const writesCache = this.pendingWriteTree_.childWrites(queryPath);
          return syncPoint.applyOperation(operation, writesCache, 
          /*serverCache=*/ null);
      }
      /**
       * A helper method that visits all descendant and ancestor SyncPoints, applying the operation.
       *
       * NOTES:
       * - Descendant SyncPoints will be visited first (since we raise events depth-first).
    
       * - We call applyOperation() on each SyncPoint passing three things:
       *   1. A version of the Operation that has been made relative to the SyncPoint location.
       *   2. A WriteTreeRef of any writes we have cached at the SyncPoint location.
       *   3. A snapshot Node with cached server data, if we have it.
    
       * - We concatenate all of the events returned by each SyncPoint and return the result.
       *
       * @param {!Operation} operation
       * @return {!Array.<!Event>}
       * @private
       */
      applyOperationToSyncPoints_(operation) {
          return this.applyOperationHelper_(operation, this.syncPointTree_, 
          /*serverCache=*/ null, this.pendingWriteTree_.childWrites(Path.Empty));
      }
      /**
       * Recursive helper for applyOperationToSyncPoints_
       *
       * @private
       * @param {!Operation} operation
       * @param {ImmutableTree.<!SyncPoint>} syncPointTree
       * @param {?Node} serverCache
       * @param {!WriteTreeRef} writesCache
       * @return {!Array.<!Event>}
       */
      applyOperationHelper_(operation, syncPointTree, serverCache, writesCache) {
          if (operation.path.isEmpty()) {
              return this.applyOperationDescendantsHelper_(operation, syncPointTree, serverCache, writesCache);
          }
          else {
              const syncPoint = syncPointTree.get(Path.Empty);
              // If we don't have cached server data, see if we can get it from this SyncPoint.
              if (serverCache == null && syncPoint != null) {
                  serverCache = syncPoint.getCompleteServerCache(Path.Empty);
              }
              let events = [];
              const childName = operation.path.getFront();
              const childOperation = operation.operationForChild(childName);
              const childTree = syncPointTree.children.get(childName);
              if (childTree && childOperation) {
                  const childServerCache = serverCache
                      ? serverCache.getImmediateChild(childName)
                      : null;
                  const childWritesCache = writesCache.child(childName);
                  events = events.concat(this.applyOperationHelper_(childOperation, childTree, childServerCache, childWritesCache));
              }
              if (syncPoint) {
                  events = events.concat(syncPoint.applyOperation(operation, writesCache, serverCache));
              }
              return events;
          }
      }
      /**
       * Recursive helper for applyOperationToSyncPoints_
       *
       * @private
       * @param {!Operation} operation
       * @param {ImmutableTree.<!SyncPoint>} syncPointTree
       * @param {?Node} serverCache
       * @param {!WriteTreeRef} writesCache
       * @return {!Array.<!Event>}
       */
      applyOperationDescendantsHelper_(operation, syncPointTree, serverCache, writesCache) {
          const syncPoint = syncPointTree.get(Path.Empty);
          // If we don't have cached server data, see if we can get it from this SyncPoint.
          if (serverCache == null && syncPoint != null) {
              serverCache = syncPoint.getCompleteServerCache(Path.Empty);
          }
          let events = [];
          syncPointTree.children.inorderTraversal((childName, childTree) => {
              const childServerCache = serverCache
                  ? serverCache.getImmediateChild(childName)
                  : null;
              const childWritesCache = writesCache.child(childName);
              const childOperation = operation.operationForChild(childName);
              if (childOperation) {
                  events = events.concat(this.applyOperationDescendantsHelper_(childOperation, childTree, childServerCache, childWritesCache));
              }
          });
          if (syncPoint) {
              events = events.concat(syncPoint.applyOperation(operation, writesCache, serverCache));
          }
          return events;
      }
  }
  /**
   * Static tracker for next query tag.
   * @type {number}
   * @private
   */
  SyncTree.nextQueryTag_ = 1;
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Mutable object which basically just stores a reference to the "latest" immutable snapshot.
   *
   * @constructor
   */
  class SnapshotHolder {
      constructor() {
          this.rootNode_ = ChildrenNode.EMPTY_NODE;
      }
      getNode(path) {
          return this.rootNode_.getChild(path);
      }
      updateSnapshot(path, newSnapshotNode) {
          this.rootNode_ = this.rootNode_.updateChild(path, newSnapshotNode);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Abstraction around FirebaseApp's token fetching capabilities.
   */
  class AuthTokenProvider {
      /**
       * @param {!FirebaseApp} app_
       */
      constructor(app_) {
          this.app_ = app_;
      }
      /**
       * @param {boolean} forceRefresh
       * @return {!Promise<FirebaseAuthTokenData>}
       */
      getToken(forceRefresh) {
          return this.app_['INTERNAL']['getToken'](forceRefresh).then(null, 
          // .catch
          function (error) {
              // TODO: Need to figure out all the cases this is raised and whether
              // this makes sense.
              if (error && error.code === 'auth/token-not-initialized') {
                  log('Got auth/token-not-initialized error.  Treating as null token.');
                  return null;
              }
              else {
                  return Promise.reject(error);
              }
          });
      }
      addTokenChangeListener(listener) {
          // TODO: We might want to wrap the listener and call it with no args to
          // avoid a leaky abstraction, but that makes removing the listener harder.
          this.app_['INTERNAL']['addAuthTokenListener'](listener);
      }
      removeTokenChangeListener(listener) {
          this.app_['INTERNAL']['removeAuthTokenListener'](listener);
      }
      notifyForInvalidToken() {
          let errorMessage = 'Provided authentication credentials for the app named "' +
              this.app_.name +
              '" are invalid. This usually indicates your app was not ' +
              'initialized correctly. ';
          if ('credential' in this.app_.options) {
              errorMessage +=
                  'Make sure the "credential" property provided to initializeApp() ' +
                      'is authorized to access the specified "databaseURL" and is from the correct ' +
                      'project.';
          }
          else if ('serviceAccount' in this.app_.options) {
              errorMessage +=
                  'Make sure the "serviceAccount" property provided to initializeApp() ' +
                      'is authorized to access the specified "databaseURL" and is from the correct ' +
                      'project.';
          }
          else {
              errorMessage +=
                  'Make sure the "apiKey" and "databaseURL" properties provided to ' +
                      'initializeApp() match the values provided for your app at ' +
                      'https://console.firebase.google.com/.';
          }
          warn(errorMessage);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Tracks a collection of stats.
   *
   * @constructor
   */
  class StatsCollection {
      constructor() {
          this.counters_ = {};
      }
      incrementCounter(name, amount = 1) {
          if (!contains(this.counters_, name))
              this.counters_[name] = 0;
          this.counters_[name] += amount;
      }
      get() {
          return deepCopy(this.counters_);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  class StatsManager {
      static getCollection(repoInfo) {
          const hashString = repoInfo.toString();
          if (!this.collections_[hashString]) {
              this.collections_[hashString] = new StatsCollection();
          }
          return this.collections_[hashString];
      }
      static getOrCreateReporter(repoInfo, creatorFunction) {
          const hashString = repoInfo.toString();
          if (!this.reporters_[hashString]) {
              this.reporters_[hashString] = creatorFunction();
          }
          return this.reporters_[hashString];
      }
  }
  StatsManager.collections_ = {};
  StatsManager.reporters_ = {};
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Returns the delta from the previous call to get stats.
   *
   * @param collection_ The collection to "listen" to.
   * @constructor
   */
  class StatsListener {
      constructor(collection_) {
          this.collection_ = collection_;
          this.last_ = null;
      }
      get() {
          const newStats = this.collection_.get();
          const delta = clone(newStats);
          if (this.last_) {
              forEach(this.last_, (stat, value) => {
                  delta[stat] = delta[stat] - value;
              });
          }
          this.last_ = newStats;
          return delta;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  // Assuming some apps may have a short amount of time on page, and a bulk of firebase operations probably
  // happen on page load, we try to report our first set of stats pretty quickly, but we wait at least 10
  // seconds to try to ensure the Firebase connection is established / settled.
  const FIRST_STATS_MIN_TIME = 10 * 1000;
  const FIRST_STATS_MAX_TIME = 30 * 1000;
  // We'll continue to report stats on average every 5 minutes.
  const REPORT_STATS_INTERVAL = 5 * 60 * 1000;
  /**
   * @constructor
   */
  class StatsReporter {
      /**
       * @param collection
       * @param server_
       */
      constructor(collection, server_) {
          this.server_ = server_;
          this.statsToReport_ = {};
          this.statsListener_ = new StatsListener(collection);
          const timeout = FIRST_STATS_MIN_TIME +
              (FIRST_STATS_MAX_TIME - FIRST_STATS_MIN_TIME) * Math.random();
          setTimeoutNonBlocking(this.reportStats_.bind(this), Math.floor(timeout));
      }
      includeStat(stat) {
          this.statsToReport_[stat] = true;
      }
      reportStats_() {
          const stats = this.statsListener_.get();
          const reportedStats = {};
          let haveStatsToReport = false;
          forEach(stats, (stat, value) => {
              if (value > 0 && contains(this.statsToReport_, stat)) {
                  reportedStats[stat] = value;
                  haveStatsToReport = true;
              }
          });
          if (haveStatsToReport) {
              this.server_.reportStats(reportedStats);
          }
          // queue our next run.
          setTimeoutNonBlocking(this.reportStats_.bind(this), Math.floor(Math.random() * 2 * REPORT_STATS_INTERVAL));
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * The event queue serves a few purposes:
   * 1. It ensures we maintain event order in the face of event callbacks doing operations that result in more
   *    events being queued.
   * 2. raiseQueuedEvents() handles being called reentrantly nicely.  That is, if in the course of raising events,
   *    raiseQueuedEvents() is called again, the "inner" call will pick up raising events where the "outer" call
   *    left off, ensuring that the events are still raised synchronously and in order.
   * 3. You can use raiseEventsAtPath and raiseEventsForChangedPath to ensure only relevant previously-queued
   *    events are raised synchronously.
   *
   * NOTE: This can all go away if/when we move to async events.
   *
   * @constructor
   */
  class EventQueue {
      constructor() {
          /**
           * @private
           * @type {!Array.<EventList>}
           */
          this.eventLists_ = [];
          /**
           * Tracks recursion depth of raiseQueuedEvents_, for debugging purposes.
           * @private
           * @type {!number}
           */
          this.recursionDepth_ = 0;
      }
      /**
       * @param {!Array.<Event>} eventDataList The new events to queue.
       */
      queueEvents(eventDataList) {
          // We group events by path, storing them in a single EventList, to make it easier to skip over them quickly.
          let currList = null;
          for (let i = 0; i < eventDataList.length; i++) {
              const eventData = eventDataList[i];
              const eventPath = eventData.getPath();
              if (currList !== null && !eventPath.equals(currList.getPath())) {
                  this.eventLists_.push(currList);
                  currList = null;
              }
              if (currList === null) {
                  currList = new EventList(eventPath);
              }
              currList.add(eventData);
          }
          if (currList) {
              this.eventLists_.push(currList);
          }
      }
      /**
       * Queues the specified events and synchronously raises all events (including previously queued ones)
       * for the specified path.
       *
       * It is assumed that the new events are all for the specified path.
       *
       * @param {!Path} path The path to raise events for.
       * @param {!Array.<Event>} eventDataList The new events to raise.
       */
      raiseEventsAtPath(path, eventDataList) {
          this.queueEvents(eventDataList);
          this.raiseQueuedEventsMatchingPredicate_((eventPath) => eventPath.equals(path));
      }
      /**
       * Queues the specified events and synchronously raises all events (including previously queued ones) for
       * locations related to the specified change path (i.e. all ancestors and descendants).
       *
       * It is assumed that the new events are all related (ancestor or descendant) to the specified path.
       *
       * @param {!Path} changedPath The path to raise events for.
       * @param {!Array.<!Event>} eventDataList The events to raise
       */
      raiseEventsForChangedPath(changedPath, eventDataList) {
          this.queueEvents(eventDataList);
          this.raiseQueuedEventsMatchingPredicate_((eventPath) => {
              return eventPath.contains(changedPath) || changedPath.contains(eventPath);
          });
      }
      /**
       * @param {!function(!Path):boolean} predicate
       * @private
       */
      raiseQueuedEventsMatchingPredicate_(predicate) {
          this.recursionDepth_++;
          let sentAll = true;
          for (let i = 0; i < this.eventLists_.length; i++) {
              const eventList = this.eventLists_[i];
              if (eventList) {
                  const eventPath = eventList.getPath();
                  if (predicate(eventPath)) {
                      this.eventLists_[i].raise();
                      this.eventLists_[i] = null;
                  }
                  else {
                      sentAll = false;
                  }
              }
          }
          if (sentAll) {
              this.eventLists_ = [];
          }
          this.recursionDepth_--;
      }
  }
  /**
   * @param {!Path} path
   * @constructor
   */
  class EventList {
      constructor(path_) {
          this.path_ = path_;
          /**
           * @type {!Array.<Event>}
           * @private
           */
          this.events_ = [];
      }
      /**
       * @param {!Event} eventData
       */
      add(eventData) {
          this.events_.push(eventData);
      }
      /**
       * Iterates through the list and raises each event
       */
      raise() {
          for (let i = 0; i < this.events_.length; i++) {
              const eventData = this.events_[i];
              if (eventData !== null) {
                  this.events_[i] = null;
                  const eventFn = eventData.getEventRunner();
                  if (logger) {
                      log('event: ' + eventData.toString());
                  }
                  exceptionGuard(eventFn);
              }
          }
      }
      /**
       * @return {!Path}
       */
      getPath() {
          return this.path_;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Base class to be used if you want to emit events. Call the constructor with
   * the set of allowed event names.
   */
  class EventEmitter {
      /**
       * @param {!Array.<string>} allowedEvents_
       */
      constructor(allowedEvents_) {
          this.allowedEvents_ = allowedEvents_;
          this.listeners_ = {};
          assert(Array.isArray(allowedEvents_) && allowedEvents_.length > 0, 'Requires a non-empty array');
      }
      /**
       * To be called by derived classes to trigger events.
       * @param {!string} eventType
       * @param {...*} var_args
       */
      trigger(eventType, ...var_args) {
          if (Array.isArray(this.listeners_[eventType])) {
              // Clone the list, since callbacks could add/remove listeners.
              const listeners = [...this.listeners_[eventType]];
              for (let i = 0; i < listeners.length; i++) {
                  listeners[i].callback.apply(listeners[i].context, var_args);
              }
          }
      }
      on(eventType, callback, context) {
          this.validateEventType_(eventType);
          this.listeners_[eventType] = this.listeners_[eventType] || [];
          this.listeners_[eventType].push({ callback, context });
          const eventData = this.getInitialEvent(eventType);
          if (eventData) {
              callback.apply(context, eventData);
          }
      }
      off(eventType, callback, context) {
          this.validateEventType_(eventType);
          const listeners = this.listeners_[eventType] || [];
          for (let i = 0; i < listeners.length; i++) {
              if (listeners[i].callback === callback &&
                  (!context || context === listeners[i].context)) {
                  listeners.splice(i, 1);
                  return;
              }
          }
      }
      validateEventType_(eventType) {
          assert(this.allowedEvents_.find(function (et) {
              return et === eventType;
          }), 'Unknown event: ' + eventType);
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * @extends {EventEmitter}
   */
  class VisibilityMonitor extends EventEmitter {
      static getInstance() {
          return new VisibilityMonitor();
      }
      constructor() {
          super(['visible']);
          let hidden;
          let visibilityChange;
          if (typeof document !== 'undefined' &&
              typeof document.addEventListener !== 'undefined') {
              if (typeof document['hidden'] !== 'undefined') {
                  // Opera 12.10 and Firefox 18 and later support
                  visibilityChange = 'visibilitychange';
                  hidden = 'hidden';
              }
              else if (typeof document['mozHidden'] !== 'undefined') {
                  visibilityChange = 'mozvisibilitychange';
                  hidden = 'mozHidden';
              }
              else if (typeof document['msHidden'] !== 'undefined') {
                  visibilityChange = 'msvisibilitychange';
                  hidden = 'msHidden';
              }
              else if (typeof document['webkitHidden'] !== 'undefined') {
                  visibilityChange = 'webkitvisibilitychange';
                  hidden = 'webkitHidden';
              }
          }
          // Initially, we always assume we are visible. This ensures that in browsers
          // without page visibility support or in cases where we are never visible
          // (e.g. chrome extension), we act as if we are visible, i.e. don't delay
          // reconnects
          this.visible_ = true;
          if (visibilityChange) {
              document.addEventListener(visibilityChange, () => {
                  const visible = !document[hidden];
                  if (visible !== this.visible_) {
                      this.visible_ = visible;
                      this.trigger('visible', visible);
                  }
              }, false);
          }
      }
      /**
       * @param {!string} eventType
       * @return {Array.<boolean>}
       */
      getInitialEvent(eventType) {
          assert(eventType === 'visible', 'Unknown event type: ' + eventType);
          return [this.visible_];
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Monitors online state (as reported by window.online/offline events).
   *
   * The expectation is that this could have many false positives (thinks we are online
   * when we're not), but no false negatives.  So we can safely use it to determine when
   * we definitely cannot reach the internet.
   *
   * @extends {EventEmitter}
   */
  class OnlineMonitor extends EventEmitter {
      constructor() {
          super(['online']);
          this.online_ = true;
          // We've had repeated complaints that Cordova apps can get stuck "offline", e.g.
          // https://forum.ionicframework.com/t/firebase-connection-is-lost-and-never-come-back/43810
          // It would seem that the 'online' event does not always fire consistently. So we disable it
          // for Cordova.
          if (typeof window !== 'undefined' &&
              typeof window.addEventListener !== 'undefined' &&
              !isMobileCordova()) {
              window.addEventListener('online', () => {
                  if (!this.online_) {
                      this.online_ = true;
                      this.trigger('online', true);
                  }
              }, false);
              window.addEventListener('offline', () => {
                  if (this.online_) {
                      this.online_ = false;
                      this.trigger('online', false);
                  }
              }, false);
          }
      }
      static getInstance() {
          return new OnlineMonitor();
      }
      /**
       * @param {!string} eventType
       * @return {Array.<boolean>}
       */
      getInitialEvent(eventType) {
          assert(eventType === 'online', 'Unknown event type: ' + eventType);
          return [this.online_];
      }
      /**
       * @return {boolean}
       */
      currentlyOnline() {
          return this.online_;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * This class ensures the packets from the server arrive in order
   * This class takes data from the server and ensures it gets passed into the callbacks in order.
   * @constructor
   */
  class PacketReceiver {
      /**
       * @param onMessage_
       */
      constructor(onMessage_) {
          this.onMessage_ = onMessage_;
          this.pendingResponses = [];
          this.currentResponseNum = 0;
          this.closeAfterResponse = -1;
          this.onClose = null;
      }
      closeAfter(responseNum, callback) {
          this.closeAfterResponse = responseNum;
          this.onClose = callback;
          if (this.closeAfterResponse < this.currentResponseNum) {
              this.onClose();
              this.onClose = null;
          }
      }
      /**
       * Each message from the server comes with a response number, and an array of data. The responseNumber
       * allows us to ensure that we process them in the right order, since we can't be guaranteed that all
       * browsers will respond in the same order as the requests we sent
       * @param {number} requestNum
       * @param {Array} data
       */
      handleResponse(requestNum, data) {
          this.pendingResponses[requestNum] = data;
          while (this.pendingResponses[this.currentResponseNum]) {
              const toProcess = this.pendingResponses[this.currentResponseNum];
              delete this.pendingResponses[this.currentResponseNum];
              for (let i = 0; i < toProcess.length; ++i) {
                  if (toProcess[i]) {
                      exceptionGuard(() => {
                          this.onMessage_(toProcess[i]);
                      });
                  }
              }
              if (this.currentResponseNum === this.closeAfterResponse) {
                  if (this.onClose) {
                      this.onClose();
                      this.onClose = null;
                  }
                  break;
              }
              this.currentResponseNum++;
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  // URL query parameters associated with longpolling
  const FIREBASE_LONGPOLL_START_PARAM = 'start';
  const FIREBASE_LONGPOLL_CLOSE_COMMAND = 'close';
  const FIREBASE_LONGPOLL_COMMAND_CB_NAME = 'pLPCommand';
  const FIREBASE_LONGPOLL_DATA_CB_NAME = 'pRTLPCB';
  const FIREBASE_LONGPOLL_ID_PARAM = 'id';
  const FIREBASE_LONGPOLL_PW_PARAM = 'pw';
  const FIREBASE_LONGPOLL_SERIAL_PARAM = 'ser';
  const FIREBASE_LONGPOLL_CALLBACK_ID_PARAM = 'cb';
  const FIREBASE_LONGPOLL_SEGMENT_NUM_PARAM = 'seg';
  const FIREBASE_LONGPOLL_SEGMENTS_IN_PACKET = 'ts';
  const FIREBASE_LONGPOLL_DATA_PARAM = 'd';
  const FIREBASE_LONGPOLL_DISCONN_FRAME_PARAM = 'disconn';
  const FIREBASE_LONGPOLL_DISCONN_FRAME_REQUEST_PARAM = 'dframe';
  //Data size constants.
  //TODO: Perf: the maximum length actually differs from browser to browser.
  // We should check what browser we're on and set accordingly.
  const MAX_URL_DATA_SIZE = 1870;
  const SEG_HEADER_SIZE = 30; //ie: &seg=8299234&ts=982389123&d=
  const MAX_PAYLOAD_SIZE = MAX_URL_DATA_SIZE - SEG_HEADER_SIZE;
  /**
   * Keepalive period
   * send a fresh request at minimum every 25 seconds. Opera has a maximum request
   * length of 30 seconds that we can't exceed.
   * @const
   * @type {number}
   */
  const KEEPALIVE_REQUEST_INTERVAL = 25000;
  /**
   * How long to wait before aborting a long-polling connection attempt.
   * @const
   * @type {number}
   */
  const LP_CONNECT_TIMEOUT = 30000;
  /**
   * This class manages a single long-polling connection.
   *
   * @constructor
   * @implements {Transport}
   */
  class BrowserPollConnection {
      /**
       * @param {string} connId An identifier for this connection, used for logging
       * @param {RepoInfo} repoInfo The info for the endpoint to send data to.
       * @param {string=} transportSessionId Optional transportSessionid if we are reconnecting for an existing
       *                                         transport session
       * @param {string=}  lastSessionId Optional lastSessionId if the PersistentConnection has already created a
       *                                     connection previously
       */
      constructor(connId, repoInfo, transportSessionId, lastSessionId) {
          this.connId = connId;
          this.repoInfo = repoInfo;
          this.transportSessionId = transportSessionId;
          this.lastSessionId = lastSessionId;
          this.bytesSent = 0;
          this.bytesReceived = 0;
          this.everConnected_ = false;
          this.log_ = logWrapper(connId);
          this.stats_ = StatsManager.getCollection(repoInfo);
          this.urlFn = (params) => repoInfo.connectionURL(LONG_POLLING, params);
      }
      /**
       *
       * @param {function(Object)} onMessage Callback when messages arrive
       * @param {function()} onDisconnect Callback with connection lost.
       */
      open(onMessage, onDisconnect) {
          this.curSegmentNum = 0;
          this.onDisconnect_ = onDisconnect;
          this.myPacketOrderer = new PacketReceiver(onMessage);
          this.isClosed_ = false;
          this.connectTimeoutTimer_ = setTimeout(() => {
              this.log_('Timed out trying to connect.');
              // Make sure we clear the host cache
              this.onClosed_();
              this.connectTimeoutTimer_ = null;
          }, Math.floor(LP_CONNECT_TIMEOUT));
          // Ensure we delay the creation of the iframe until the DOM is loaded.
          executeWhenDOMReady(() => {
              if (this.isClosed_)
                  return;
              //Set up a callback that gets triggered once a connection is set up.
              this.scriptTagHolder = new FirebaseIFrameScriptHolder((...args) => {
                  const [command, arg1, arg2, arg3, arg4] = args;
                  this.incrementIncomingBytes_(args);
                  if (!this.scriptTagHolder)
                      return; // we closed the connection.
                  if (this.connectTimeoutTimer_) {
                      clearTimeout(this.connectTimeoutTimer_);
                      this.connectTimeoutTimer_ = null;
                  }
                  this.everConnected_ = true;
                  if (command == FIREBASE_LONGPOLL_START_PARAM) {
                      this.id = arg1;
                      this.password = arg2;
                  }
                  else if (command === FIREBASE_LONGPOLL_CLOSE_COMMAND) {
                      // Don't clear the host cache. We got a response from the server, so we know it's reachable
                      if (arg1) {
                          // We aren't expecting any more data (other than what the server's already in the process of sending us
                          // through our already open polls), so don't send any more.
                          this.scriptTagHolder.sendNewPolls = false;
                          // arg1 in this case is the last response number sent by the server. We should try to receive
                          // all of the responses up to this one before closing
                          this.myPacketOrderer.closeAfter(arg1, () => {
                              this.onClosed_();
                          });
                      }
                      else {
                          this.onClosed_();
                      }
                  }
                  else {
                      throw new Error('Unrecognized command received: ' + command);
                  }
              }, (...args) => {
                  const [pN, data] = args;
                  this.incrementIncomingBytes_(args);
                  this.myPacketOrderer.handleResponse(pN, data);
              }, () => {
                  this.onClosed_();
              }, this.urlFn);
              //Send the initial request to connect. The serial number is simply to keep the browser from pulling previous results
              //from cache.
              const urlParams = {};
              urlParams[FIREBASE_LONGPOLL_START_PARAM] = 't';
              urlParams[FIREBASE_LONGPOLL_SERIAL_PARAM] = Math.floor(Math.random() * 100000000);
              if (this.scriptTagHolder.uniqueCallbackIdentifier)
                  urlParams[FIREBASE_LONGPOLL_CALLBACK_ID_PARAM] = this.scriptTagHolder.uniqueCallbackIdentifier;
              urlParams[VERSION_PARAM] = PROTOCOL_VERSION;
              if (this.transportSessionId) {
                  urlParams[TRANSPORT_SESSION_PARAM] = this.transportSessionId;
              }
              if (this.lastSessionId) {
                  urlParams[LAST_SESSION_PARAM] = this.lastSessionId;
              }
              if (!isNodeSdk() &&
                  typeof location !== 'undefined' &&
                  location.href &&
                  location.href.indexOf(FORGE_DOMAIN) !== -1) {
                  urlParams[REFERER_PARAM] = FORGE_REF;
              }
              const connectURL = this.urlFn(urlParams);
              this.log_('Connecting via long-poll to ' + connectURL);
              this.scriptTagHolder.addTag(connectURL, () => {
                  /* do nothing */
              });
          });
      }
      /**
       * Call this when a handshake has completed successfully and we want to consider the connection established
       */
      start() {
          this.scriptTagHolder.startLongPoll(this.id, this.password);
          this.addDisconnectPingFrame(this.id, this.password);
      }
      /**
       * Forces long polling to be considered as a potential transport
       */
      static forceAllow() {
          BrowserPollConnection.forceAllow_ = true;
      }
      /**
       * Forces longpolling to not be considered as a potential transport
       */
      static forceDisallow() {
          BrowserPollConnection.forceDisallow_ = true;
      }
      // Static method, use string literal so it can be accessed in a generic way
      static isAvailable() {
          // NOTE: In React-Native there's normally no 'document', but if you debug a React-Native app in
          // the Chrome debugger, 'document' is defined, but document.createElement is null (2015/06/08).
          return (BrowserPollConnection.forceAllow_ ||
              (!BrowserPollConnection.forceDisallow_ &&
                  typeof document !== 'undefined' &&
                  document.createElement != null &&
                  !isChromeExtensionContentScript() &&
                  !isWindowsStoreApp() &&
                  !isNodeSdk()));
      }
      /**
       * No-op for polling
       */
      markConnectionHealthy() { }
      /**
       * Stops polling and cleans up the iframe
       * @private
       */
      shutdown_() {
          this.isClosed_ = true;
          if (this.scriptTagHolder) {
              this.scriptTagHolder.close();
              this.scriptTagHolder = null;
          }
          //remove the disconnect frame, which will trigger an XHR call to the server to tell it we're leaving.
          if (this.myDisconnFrame) {
              document.body.removeChild(this.myDisconnFrame);
              this.myDisconnFrame = null;
          }
          if (this.connectTimeoutTimer_) {
              clearTimeout(this.connectTimeoutTimer_);
              this.connectTimeoutTimer_ = null;
          }
      }
      /**
       * Triggered when this transport is closed
       * @private
       */
      onClosed_() {
          if (!this.isClosed_) {
              this.log_('Longpoll is closing itself');
              this.shutdown_();
              if (this.onDisconnect_) {
                  this.onDisconnect_(this.everConnected_);
                  this.onDisconnect_ = null;
              }
          }
      }
      /**
       * External-facing close handler. RealTime has requested we shut down. Kill our connection and tell the server
       * that we've left.
       */
      close() {
          if (!this.isClosed_) {
              this.log_('Longpoll is being closed.');
              this.shutdown_();
          }
      }
      /**
       * Send the JSON object down to the server. It will need to be stringified, base64 encoded, and then
       * broken into chunks (since URLs have a small maximum length).
       * @param {!Object} data The JSON data to transmit.
       */
      send(data) {
          const dataStr = stringify(data);
          this.bytesSent += dataStr.length;
          this.stats_.incrementCounter('bytes_sent', dataStr.length);
          //first, lets get the base64-encoded data
          const base64data = base64Encode(dataStr);
          //We can only fit a certain amount in each URL, so we need to split this request
          //up into multiple pieces if it doesn't fit in one request.
          const dataSegs = splitStringBySize(base64data, MAX_PAYLOAD_SIZE);
          //Enqueue each segment for transmission. We assign each chunk a sequential ID and a total number
          //of segments so that we can reassemble the packet on the server.
          for (let i = 0; i < dataSegs.length; i++) {
              this.scriptTagHolder.enqueueSegment(this.curSegmentNum, dataSegs.length, dataSegs[i]);
              this.curSegmentNum++;
          }
      }
      /**
       * This is how we notify the server that we're leaving.
       * We aren't able to send requests with DHTML on a window close event, but we can
       * trigger XHR requests in some browsers (everything but Opera basically).
       * @param {!string} id
       * @param {!string} pw
       */
      addDisconnectPingFrame(id, pw) {
          if (isNodeSdk())
              return;
          this.myDisconnFrame = document.createElement('iframe');
          const urlParams = {};
          urlParams[FIREBASE_LONGPOLL_DISCONN_FRAME_REQUEST_PARAM] = 't';
          urlParams[FIREBASE_LONGPOLL_ID_PARAM] = id;
          urlParams[FIREBASE_LONGPOLL_PW_PARAM] = pw;
          this.myDisconnFrame.src = this.urlFn(urlParams);
          this.myDisconnFrame.style.display = 'none';
          document.body.appendChild(this.myDisconnFrame);
      }
      /**
       * Used to track the bytes received by this client
       * @param {*} args
       * @private
       */
      incrementIncomingBytes_(args) {
          // TODO: This is an annoying perf hit just to track the number of incoming bytes.  Maybe it should be opt-in.
          const bytesReceived = stringify(args).length;
          this.bytesReceived += bytesReceived;
          this.stats_.incrementCounter('bytes_received', bytesReceived);
      }
  }
  /*********************************************************************************************
   * A wrapper around an iframe that is used as a long-polling script holder.
   * @constructor
   *********************************************************************************************/
  class FirebaseIFrameScriptHolder {
      /**
       * @param commandCB - The callback to be called when control commands are recevied from the server.
       * @param onMessageCB - The callback to be triggered when responses arrive from the server.
       * @param onDisconnect - The callback to be triggered when this tag holder is closed
       * @param urlFn - A function that provides the URL of the endpoint to send data to.
       */
      constructor(commandCB, onMessageCB, onDisconnect, urlFn) {
          this.onDisconnect = onDisconnect;
          this.urlFn = urlFn;
          //We maintain a count of all of the outstanding requests, because if we have too many active at once it can cause
          //problems in some browsers.
          /**
           * @type {CountedSet.<number, number>}
           */
          this.outstandingRequests = new CountedSet();
          //A queue of the pending segments waiting for transmission to the server.
          this.pendingSegs = [];
          //A serial number. We use this for two things:
          // 1) A way to ensure the browser doesn't cache responses to polls
          // 2) A way to make the server aware when long-polls arrive in a different order than we started them. The
          //    server needs to release both polls in this case or it will cause problems in Opera since Opera can only execute
          //    JSONP code in the order it was added to the iframe.
          this.currentSerial = Math.floor(Math.random() * 100000000);
          // This gets set to false when we're "closing down" the connection (e.g. we're switching transports but there's still
          // incoming data from the server that we're waiting for).
          this.sendNewPolls = true;
          if (!isNodeSdk()) {
              //Each script holder registers a couple of uniquely named callbacks with the window. These are called from the
              //iframes where we put the long-polling script tags. We have two callbacks:
              //   1) Command Callback - Triggered for control issues, like starting a connection.
              //   2) Message Callback - Triggered when new data arrives.
              this.uniqueCallbackIdentifier = LUIDGenerator();
              window[FIREBASE_LONGPOLL_COMMAND_CB_NAME + this.uniqueCallbackIdentifier] = commandCB;
              window[FIREBASE_LONGPOLL_DATA_CB_NAME + this.uniqueCallbackIdentifier] = onMessageCB;
              //Create an iframe for us to add script tags to.
              this.myIFrame = FirebaseIFrameScriptHolder.createIFrame_();
              // Set the iframe's contents.
              let script = '';
              // if we set a javascript url, it's IE and we need to set the document domain. The javascript url is sufficient
              // for ie9, but ie8 needs to do it again in the document itself.
              if (this.myIFrame.src &&
                  this.myIFrame.src.substr(0, 'javascript:'.length) === 'javascript:') {
                  const currentDomain = document.domain;
                  script = '<script>document.domain="' + currentDomain + '";</script>';
              }
              const iframeContents = '<html><body>' + script + '</body></html>';
              try {
                  this.myIFrame.doc.open();
                  this.myIFrame.doc.write(iframeContents);
                  this.myIFrame.doc.close();
              }
              catch (e) {
                  log('frame writing exception');
                  if (e.stack) {
                      log(e.stack);
                  }
                  log(e);
              }
          }
          else {
              this.commandCB = commandCB;
              this.onMessageCB = onMessageCB;
          }
      }
      /**
       * Each browser has its own funny way to handle iframes. Here we mush them all together into one object that I can
       * actually use.
       * @private
       * @return {Element}
       */
      static createIFrame_() {
          const iframe = document.createElement('iframe');
          iframe.style.display = 'none';
          // This is necessary in order to initialize the document inside the iframe
          if (document.body) {
              document.body.appendChild(iframe);
              try {
                  // If document.domain has been modified in IE, this will throw an error, and we need to set the
                  // domain of the iframe's document manually. We can do this via a javascript: url as the src attribute
                  // Also note that we must do this *after* the iframe has been appended to the page. Otherwise it doesn't work.
                  const a = iframe.contentWindow.document;
                  if (!a) {
                      // Apologies for the log-spam, I need to do something to keep closure from optimizing out the assignment above.
                      log('No IE domain setting required');
                  }
              }
              catch (e) {
                  const domain = document.domain;
                  iframe.src =
                      "javascript:void((function(){document.open();document.domain='" +
                          domain +
                          "';document.close();})())";
              }
          }
          else {
              // LongPollConnection attempts to delay initialization until the document is ready, so hopefully this
              // never gets hit.
              throw 'Document body has not initialized. Wait to initialize Firebase until after the document is ready.';
          }
          // Get the document of the iframe in a browser-specific way.
          if (iframe.contentDocument) {
              iframe.doc = iframe.contentDocument; // Firefox, Opera, Safari
          }
          else if (iframe.contentWindow) {
              iframe.doc = iframe.contentWindow.document; // Internet Explorer
          }
          else if (iframe.document) {
              iframe.doc = iframe.document; //others?
          }
          return iframe;
      }
      /**
       * Cancel all outstanding queries and remove the frame.
       */
      close() {
          //Mark this iframe as dead, so no new requests are sent.
          this.alive = false;
          if (this.myIFrame) {
              //We have to actually remove all of the html inside this iframe before removing it from the
              //window, or IE will continue loading and executing the script tags we've already added, which
              //can lead to some errors being thrown. Setting innerHTML seems to be the easiest way to do this.
              this.myIFrame.doc.body.innerHTML = '';
              setTimeout(() => {
                  if (this.myIFrame !== null) {
                      document.body.removeChild(this.myIFrame);
                      this.myIFrame = null;
                  }
              }, Math.floor(0));
          }
          if (isNodeSdk() && this.myID) {
              const urlParams = {};
              urlParams[FIREBASE_LONGPOLL_DISCONN_FRAME_PARAM] = 't';
              urlParams[FIREBASE_LONGPOLL_ID_PARAM] = this.myID;
              urlParams[FIREBASE_LONGPOLL_PW_PARAM] = this.myPW;
              const theURL = this.urlFn(urlParams);
              FirebaseIFrameScriptHolder.nodeRestRequest(theURL);
          }
          // Protect from being called recursively.
          const onDisconnect = this.onDisconnect;
          if (onDisconnect) {
              this.onDisconnect = null;
              onDisconnect();
          }
      }
      /**
       * Actually start the long-polling session by adding the first script tag(s) to the iframe.
       * @param {!string} id - The ID of this connection
       * @param {!string} pw - The password for this connection
       */
      startLongPoll(id, pw) {
          this.myID = id;
          this.myPW = pw;
          this.alive = true;
          //send the initial request. If there are requests queued, make sure that we transmit as many as we are currently able to.
          while (this.newRequest_()) { }
      }
      /**
       * This is called any time someone might want a script tag to be added. It adds a script tag when there aren't
       * too many outstanding requests and we are still alive.
       *
       * If there are outstanding packet segments to send, it sends one. If there aren't, it sends a long-poll anyways if
       * needed.
       */
      newRequest_() {
          // We keep one outstanding request open all the time to receive data, but if we need to send data
          // (pendingSegs.length > 0) then we create a new request to send the data.  The server will automatically
          // close the old request.
          if (this.alive &&
              this.sendNewPolls &&
              this.outstandingRequests.count() < (this.pendingSegs.length > 0 ? 2 : 1)) {
              //construct our url
              this.currentSerial++;
              const urlParams = {};
              urlParams[FIREBASE_LONGPOLL_ID_PARAM] = this.myID;
              urlParams[FIREBASE_LONGPOLL_PW_PARAM] = this.myPW;
              urlParams[FIREBASE_LONGPOLL_SERIAL_PARAM] = this.currentSerial;
              let theURL = this.urlFn(urlParams);
              //Now add as much data as we can.
              let curDataString = '';
              let i = 0;
              while (this.pendingSegs.length > 0) {
                  //first, lets see if the next segment will fit.
                  const nextSeg = this.pendingSegs[0];
                  if (nextSeg.d.length + SEG_HEADER_SIZE + curDataString.length <=
                      MAX_URL_DATA_SIZE) {
                      //great, the segment will fit. Lets append it.
                      const theSeg = this.pendingSegs.shift();
                      curDataString =
                          curDataString +
                              '&' +
                              FIREBASE_LONGPOLL_SEGMENT_NUM_PARAM +
                              i +
                              '=' +
                              theSeg.seg +
                              '&' +
                              FIREBASE_LONGPOLL_SEGMENTS_IN_PACKET +
                              i +
                              '=' +
                              theSeg.ts +
                              '&' +
                              FIREBASE_LONGPOLL_DATA_PARAM +
                              i +
                              '=' +
                              theSeg.d;
                      i++;
                  }
                  else {
                      break;
                  }
              }
              theURL = theURL + curDataString;
              this.addLongPollTag_(theURL, this.currentSerial);
              return true;
          }
          else {
              return false;
          }
      }
      /**
       * Queue a packet for transmission to the server.
       * @param segnum - A sequential id for this packet segment used for reassembly
       * @param totalsegs - The total number of segments in this packet
       * @param data - The data for this segment.
       */
      enqueueSegment(segnum, totalsegs, data) {
          //add this to the queue of segments to send.
          this.pendingSegs.push({ seg: segnum, ts: totalsegs, d: data });
          //send the data immediately if there isn't already data being transmitted, unless
          //startLongPoll hasn't been called yet.
          if (this.alive) {
              this.newRequest_();
          }
      }
      /**
       * Add a script tag for a regular long-poll request.
       * @param {!string} url - The URL of the script tag.
       * @param {!number} serial - The serial number of the request.
       * @private
       */
      addLongPollTag_(url, serial) {
          //remember that we sent this request.
          this.outstandingRequests.add(serial, 1);
          const doNewRequest = () => {
              this.outstandingRequests.remove(serial);
              this.newRequest_();
          };
          // If this request doesn't return on its own accord (by the server sending us some data), we'll
          // create a new one after the KEEPALIVE interval to make sure we always keep a fresh request open.
          const keepaliveTimeout = setTimeout(doNewRequest, Math.floor(KEEPALIVE_REQUEST_INTERVAL));
          const readyStateCB = () => {
              // Request completed.  Cancel the keepalive.
              clearTimeout(keepaliveTimeout);
              // Trigger a new request so we can continue receiving data.
              doNewRequest();
          };
          this.addTag(url, readyStateCB);
      }
      /**
       * Add an arbitrary script tag to the iframe.
       * @param {!string} url - The URL for the script tag source.
       * @param {!function()} loadCB - A callback to be triggered once the script has loaded.
       */
      addTag(url, loadCB) {
          if (isNodeSdk()) {
              this.doNodeLongPoll(url, loadCB);
          }
          else {
              setTimeout(() => {
                  try {
                      // if we're already closed, don't add this poll
                      if (!this.sendNewPolls)
                          return;
                      const newScript = this.myIFrame.doc.createElement('script');
                      newScript.type = 'text/javascript';
                      newScript.async = true;
                      newScript.src = url;
                      newScript.onload = newScript.onreadystatechange = function () {
                          const rstate = newScript.readyState;
                          if (!rstate || rstate === 'loaded' || rstate === 'complete') {
                              newScript.onload = newScript.onreadystatechange = null;
                              if (newScript.parentNode) {
                                  newScript.parentNode.removeChild(newScript);
                              }
                              loadCB();
                          }
                      };
                      newScript.onerror = () => {
                          log('Long-poll script failed to load: ' + url);
                          this.sendNewPolls = false;
                          this.close();
                      };
                      this.myIFrame.doc.body.appendChild(newScript);
                  }
                  catch (e) {
                      // TODO: we should make this error visible somehow
                  }
              }, Math.floor(1));
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const WEBSOCKET_MAX_FRAME_SIZE = 16384;
  const WEBSOCKET_KEEPALIVE_INTERVAL = 45000;
  let WebSocketImpl = null;
  if (typeof MozWebSocket !== 'undefined') {
      WebSocketImpl = MozWebSocket;
  }
  else if (typeof WebSocket !== 'undefined') {
      WebSocketImpl = WebSocket;
  }
  /**
   * Create a new websocket connection with the given callbacks.
   * @constructor
   * @implements {Transport}
   */
  class WebSocketConnection {
      /**
       * @param {string} connId identifier for this transport
       * @param {RepoInfo} repoInfo The info for the websocket endpoint.
       * @param {string=} transportSessionId Optional transportSessionId if this is connecting to an existing transport
       *                                         session
       * @param {string=} lastSessionId Optional lastSessionId if there was a previous connection
       */
      constructor(connId, repoInfo, transportSessionId, lastSessionId) {
          this.connId = connId;
          this.keepaliveTimer = null;
          this.frames = null;
          this.totalFrames = 0;
          this.bytesSent = 0;
          this.bytesReceived = 0;
          this.log_ = logWrapper(this.connId);
          this.stats_ = StatsManager.getCollection(repoInfo);
          this.connURL = WebSocketConnection.connectionURL_(repoInfo, transportSessionId, lastSessionId);
      }
      /**
       * @param {RepoInfo} repoInfo The info for the websocket endpoint.
       * @param {string=} transportSessionId Optional transportSessionId if this is connecting to an existing transport
       *                                         session
       * @param {string=} lastSessionId Optional lastSessionId if there was a previous connection
       * @return {string} connection url
       * @private
       */
      static connectionURL_(repoInfo, transportSessionId, lastSessionId) {
          const urlParams = {};
          urlParams[VERSION_PARAM] = PROTOCOL_VERSION;
          if (!isNodeSdk() &&
              typeof location !== 'undefined' &&
              location.href &&
              location.href.indexOf(FORGE_DOMAIN) !== -1) {
              urlParams[REFERER_PARAM] = FORGE_REF;
          }
          if (transportSessionId) {
              urlParams[TRANSPORT_SESSION_PARAM] = transportSessionId;
          }
          if (lastSessionId) {
              urlParams[LAST_SESSION_PARAM] = lastSessionId;
          }
          return repoInfo.connectionURL(WEBSOCKET, urlParams);
      }
      /**
       *
       * @param onMessage Callback when messages arrive
       * @param onDisconnect Callback with connection lost.
       */
      open(onMessage, onDisconnect) {
          this.onDisconnect = onDisconnect;
          this.onMessage = onMessage;
          this.log_('Websocket connecting to ' + this.connURL);
          this.everConnected_ = false;
          // Assume failure until proven otherwise.
          PersistentStorage.set('previous_websocket_failure', true);
          try {
              if (isNodeSdk()) {
                  const device = CONSTANTS.NODE_ADMIN ? 'AdminNode' : 'Node';
                  // UA Format: Firebase/<wire_protocol>/<sdk_version>/<platform>/<device>
                  const options = {
                      headers: {
                          'User-Agent': `Firebase/${PROTOCOL_VERSION}/${firebase.SDK_VERSION}/${process.platform}/${device}`
                      }
                  };
                  // Plumb appropriate http_proxy environment variable into faye-websocket if it exists.
                  const env = process['env'];
                  const proxy = this.connURL.indexOf('wss://') == 0
                      ? env['HTTPS_PROXY'] || env['https_proxy']
                      : env['HTTP_PROXY'] || env['http_proxy'];
                  if (proxy) {
                      options['proxy'] = { origin: proxy };
                  }
                  this.mySock = new WebSocketImpl(this.connURL, [], options);
              }
              else {
                  this.mySock = new WebSocketImpl(this.connURL);
              }
          }
          catch (e) {
              this.log_('Error instantiating WebSocket.');
              const error = e.message || e.data;
              if (error) {
                  this.log_(error);
              }
              this.onClosed_();
              return;
          }
          this.mySock.onopen = () => {
              this.log_('Websocket connected.');
              this.everConnected_ = true;
          };
          this.mySock.onclose = () => {
              this.log_('Websocket connection was disconnected.');
              this.mySock = null;
              this.onClosed_();
          };
          this.mySock.onmessage = (m) => {
              this.handleIncomingFrame(m);
          };
          this.mySock.onerror = (e) => {
              this.log_('WebSocket error.  Closing connection.');
              const error = e.message || e.data;
              if (error) {
                  this.log_(error);
              }
              this.onClosed_();
          };
      }
      /**
       * No-op for websockets, we don't need to do anything once the connection is confirmed as open
       */
      start() { }
      static forceDisallow() {
          WebSocketConnection.forceDisallow_ = true;
      }
      static isAvailable() {
          let isOldAndroid = false;
          if (typeof navigator !== 'undefined' && navigator.userAgent) {
              const oldAndroidRegex = /Android ([0-9]{0,}\.[0-9]{0,})/;
              const oldAndroidMatch = navigator.userAgent.match(oldAndroidRegex);
              if (oldAndroidMatch && oldAndroidMatch.length > 1) {
                  if (parseFloat(oldAndroidMatch[1]) < 4.4) {
                      isOldAndroid = true;
                  }
              }
          }
          return (!isOldAndroid &&
              WebSocketImpl !== null &&
              !WebSocketConnection.forceDisallow_);
      }
      /**
       * Returns true if we previously failed to connect with this transport.
       * @return {boolean}
       */
      static previouslyFailed() {
          // If our persistent storage is actually only in-memory storage,
          // we default to assuming that it previously failed to be safe.
          return (PersistentStorage.isInMemoryStorage ||
              PersistentStorage.get('previous_websocket_failure') === true);
      }
      markConnectionHealthy() {
          PersistentStorage.remove('previous_websocket_failure');
      }
      appendFrame_(data) {
          this.frames.push(data);
          if (this.frames.length == this.totalFrames) {
              const fullMess = this.frames.join('');
              this.frames = null;
              const jsonMess = jsonEval(fullMess);
              //handle the message
              this.onMessage(jsonMess);
          }
      }
      /**
       * @param {number} frameCount The number of frames we are expecting from the server
       * @private
       */
      handleNewFrameCount_(frameCount) {
          this.totalFrames = frameCount;
          this.frames = [];
      }
      /**
       * Attempts to parse a frame count out of some text. If it can't, assumes a value of 1
       * @param {!String} data
       * @return {?String} Any remaining data to be process, or null if there is none
       * @private
       */
      extractFrameCount_(data) {
          assert(this.frames === null, 'We already have a frame buffer');
          // TODO: The server is only supposed to send up to 9999 frames (i.e. length <= 4), but that isn't being enforced
          // currently.  So allowing larger frame counts (length <= 6).  See https://app.asana.com/0/search/8688598998380/8237608042508
          if (data.length <= 6) {
              const frameCount = Number(data);
              if (!isNaN(frameCount)) {
                  this.handleNewFrameCount_(frameCount);
                  return null;
              }
          }
          this.handleNewFrameCount_(1);
          return data;
      }
      /**
       * Process a websocket frame that has arrived from the server.
       * @param mess The frame data
       */
      handleIncomingFrame(mess) {
          if (this.mySock === null)
              return; // Chrome apparently delivers incoming packets even after we .close() the connection sometimes.
          const data = mess['data'];
          this.bytesReceived += data.length;
          this.stats_.incrementCounter('bytes_received', data.length);
          this.resetKeepAlive();
          if (this.frames !== null) {
              // we're buffering
              this.appendFrame_(data);
          }
          else {
              // try to parse out a frame count, otherwise, assume 1 and process it
              const remainingData = this.extractFrameCount_(data);
              if (remainingData !== null) {
                  this.appendFrame_(remainingData);
              }
          }
      }
      /**
       * Send a message to the server
       * @param {Object} data The JSON object to transmit
       */
      send(data) {
          this.resetKeepAlive();
          const dataStr = stringify(data);
          this.bytesSent += dataStr.length;
          this.stats_.incrementCounter('bytes_sent', dataStr.length);
          //We can only fit a certain amount in each websocket frame, so we need to split this request
          //up into multiple pieces if it doesn't fit in one request.
          const dataSegs = splitStringBySize(dataStr, WEBSOCKET_MAX_FRAME_SIZE);
          //Send the length header
          if (dataSegs.length > 1) {
              this.sendString_(String(dataSegs.length));
          }
          //Send the actual data in segments.
          for (let i = 0; i < dataSegs.length; i++) {
              this.sendString_(dataSegs[i]);
          }
      }
      shutdown_() {
          this.isClosed_ = true;
          if (this.keepaliveTimer) {
              clearInterval(this.keepaliveTimer);
              this.keepaliveTimer = null;
          }
          if (this.mySock) {
              this.mySock.close();
              this.mySock = null;
          }
      }
      onClosed_() {
          if (!this.isClosed_) {
              this.log_('WebSocket is closing itself');
              this.shutdown_();
              // since this is an internal close, trigger the close listener
              if (this.onDisconnect) {
                  this.onDisconnect(this.everConnected_);
                  this.onDisconnect = null;
              }
          }
      }
      /**
       * External-facing close handler.
       * Close the websocket and kill the connection.
       */
      close() {
          if (!this.isClosed_) {
              this.log_('WebSocket is being closed');
              this.shutdown_();
          }
      }
      /**
       * Kill the current keepalive timer and start a new one, to ensure that it always fires N seconds after
       * the last activity.
       */
      resetKeepAlive() {
          clearInterval(this.keepaliveTimer);
          this.keepaliveTimer = setInterval(() => {
              //If there has been no websocket activity for a while, send a no-op
              if (this.mySock) {
                  this.sendString_('0');
              }
              this.resetKeepAlive();
          }, Math.floor(WEBSOCKET_KEEPALIVE_INTERVAL));
      }
      /**
       * Send a string over the websocket.
       *
       * @param {string} str String to send.
       * @private
       */
      sendString_(str) {
          // Firefox seems to sometimes throw exceptions (NS_ERROR_UNEXPECTED) from websocket .send()
          // calls for some unknown reason.  We treat these as an error and disconnect.
          // See https://app.asana.com/0/58926111402292/68021340250410
          try {
              this.mySock.send(str);
          }
          catch (e) {
              this.log_('Exception thrown from WebSocket.send():', e.message || e.data, 'Closing connection.');
              setTimeout(this.onClosed_.bind(this), 0);
          }
      }
  }
  /**
   * Number of response before we consider the connection "healthy."
   * @type {number}
   */
  WebSocketConnection.responsesRequiredToBeHealthy = 2;
  /**
   * Time to wait for the connection te become healthy before giving up.
   * @type {number}
   */
  WebSocketConnection.healthyTimeout = 30000;
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Currently simplistic, this class manages what transport a Connection should use at various stages of its
   * lifecycle.
   *
   * It starts with longpolling in a browser, and httppolling on node. It then upgrades to websockets if
   * they are available.
   * @constructor
   */
  class TransportManager {
      /**
       * @const
       * @type {!Array.<function(new:Transport, string, RepoInfo, string=)>}
       */
      static get ALL_TRANSPORTS() {
          return [BrowserPollConnection, WebSocketConnection];
      }
      /**
       * @param {!RepoInfo} repoInfo Metadata around the namespace we're connecting to
       */
      constructor(repoInfo) {
          this.initTransports_(repoInfo);
      }
      /**
       * @param {!RepoInfo} repoInfo
       * @private
       */
      initTransports_(repoInfo) {
          const isWebSocketsAvailable = WebSocketConnection && WebSocketConnection['isAvailable']();
          let isSkipPollConnection = isWebSocketsAvailable && !WebSocketConnection.previouslyFailed();
          if (repoInfo.webSocketOnly) {
              if (!isWebSocketsAvailable)
                  warn("wss:// URL used, but browser isn't known to support websockets.  Trying anyway.");
              isSkipPollConnection = true;
          }
          if (isSkipPollConnection) {
              this.transports_ = [WebSocketConnection];
          }
          else {
              const transports = (this.transports_ = []);
              each(TransportManager.ALL_TRANSPORTS, (i, transport) => {
                  if (transport && transport['isAvailable']()) {
                      transports.push(transport);
                  }
              });
          }
      }
      /**
       * @return {function(new:Transport, !string, !RepoInfo, string=, string=)} The constructor for the
       * initial transport to use
       */
      initialTransport() {
          if (this.transports_.length > 0) {
              return this.transports_[0];
          }
          else {
              throw new Error('No transports available');
          }
      }
      /**
       * @return {?function(new:Transport, function(),function(), string=)} The constructor for the next
       * transport, or null
       */
      upgradeTransport() {
          if (this.transports_.length > 1) {
              return this.transports_[1];
          }
          else {
              return null;
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  // Abort upgrade attempt if it takes longer than 60s.
  const UPGRADE_TIMEOUT = 60000;
  // For some transports (WebSockets), we need to "validate" the transport by exchanging a few requests and responses.
  // If we haven't sent enough requests within 5s, we'll start sending noop ping requests.
  const DELAY_BEFORE_SENDING_EXTRA_REQUESTS = 5000;
  // If the initial data sent triggers a lot of bandwidth (i.e. it's a large put or a listen for a large amount of data)
  // then we may not be able to exchange our ping/pong requests within the healthy timeout.  So if we reach the timeout
  // but we've sent/received enough bytes, we don't cancel the connection.
  const BYTES_SENT_HEALTHY_OVERRIDE = 10 * 1024;
  const BYTES_RECEIVED_HEALTHY_OVERRIDE = 100 * 1024;
  const MESSAGE_TYPE = 't';
  const MESSAGE_DATA = 'd';
  const CONTROL_SHUTDOWN = 's';
  const CONTROL_RESET = 'r';
  const CONTROL_ERROR = 'e';
  const CONTROL_PONG = 'o';
  const SWITCH_ACK = 'a';
  const END_TRANSMISSION = 'n';
  const PING = 'p';
  const SERVER_HELLO = 'h';
  /**
   * Creates a new real-time connection to the server using whichever method works
   * best in the current browser.
   *
   * @constructor
   */
  class Connection {
      /**
       * @param {!string} id - an id for this connection
       * @param {!RepoInfo} repoInfo_ - the info for the endpoint to connect to
       * @param {function(Object)} onMessage_ - the callback to be triggered when a server-push message arrives
       * @param {function(number, string)} onReady_ - the callback to be triggered when this connection is ready to send messages.
       * @param {function()} onDisconnect_ - the callback to be triggered when a connection was lost
       * @param {function(string)} onKill_ - the callback to be triggered when this connection has permanently shut down.
       * @param {string=} lastSessionId - last session id in persistent connection. is used to clean up old session in real-time server
       */
      constructor(id, repoInfo_, onMessage_, onReady_, onDisconnect_, onKill_, lastSessionId) {
          this.id = id;
          this.repoInfo_ = repoInfo_;
          this.onMessage_ = onMessage_;
          this.onReady_ = onReady_;
          this.onDisconnect_ = onDisconnect_;
          this.onKill_ = onKill_;
          this.lastSessionId = lastSessionId;
          this.connectionCount = 0;
          this.pendingDataMessages = [];
          this.state_ = 0 /* CONNECTING */;
          this.log_ = logWrapper('c:' + this.id + ':');
          this.transportManager_ = new TransportManager(repoInfo_);
          this.log_('Connection created');
          this.start_();
      }
      /**
       * Starts a connection attempt
       * @private
       */
      start_() {
          const conn = this.transportManager_.initialTransport();
          this.conn_ = new conn(this.nextTransportId_(), this.repoInfo_, undefined, this.lastSessionId);
          // For certain transports (WebSockets), we need to send and receive several messages back and forth before we
          // can consider the transport healthy.
          this.primaryResponsesRequired_ = conn['responsesRequiredToBeHealthy'] || 0;
          const onMessageReceived = this.connReceiver_(this.conn_);
          const onConnectionLost = this.disconnReceiver_(this.conn_);
          this.tx_ = this.conn_;
          this.rx_ = this.conn_;
          this.secondaryConn_ = null;
          this.isHealthy_ = false;
          /*
           * Firefox doesn't like when code from one iframe tries to create another iframe by way of the parent frame.
           * This can occur in the case of a redirect, i.e. we guessed wrong on what server to connect to and received a reset.
           * Somehow, setTimeout seems to make this ok. That doesn't make sense from a security perspective, since you should
           * still have the context of your originating frame.
           */
          setTimeout(() => {
              // this.conn_ gets set to null in some of the tests. Check to make sure it still exists before using it
              this.conn_ && this.conn_.open(onMessageReceived, onConnectionLost);
          }, Math.floor(0));
          const healthyTimeout_ms = conn['healthyTimeout'] || 0;
          if (healthyTimeout_ms > 0) {
              this.healthyTimeout_ = setTimeoutNonBlocking(() => {
                  this.healthyTimeout_ = null;
                  if (!this.isHealthy_) {
                      if (this.conn_ &&
                          this.conn_.bytesReceived > BYTES_RECEIVED_HEALTHY_OVERRIDE) {
                          this.log_('Connection exceeded healthy timeout but has received ' +
                              this.conn_.bytesReceived +
                              ' bytes.  Marking connection healthy.');
                          this.isHealthy_ = true;
                          this.conn_.markConnectionHealthy();
                      }
                      else if (this.conn_ &&
                          this.conn_.bytesSent > BYTES_SENT_HEALTHY_OVERRIDE) {
                          this.log_('Connection exceeded healthy timeout but has sent ' +
                              this.conn_.bytesSent +
                              ' bytes.  Leaving connection alive.');
                          // NOTE: We don't want to mark it healthy, since we have no guarantee that the bytes have made it to
                          // the server.
                      }
                      else {
                          this.log_('Closing unhealthy connection after timeout.');
                          this.close();
                      }
                  }
              }, Math.floor(healthyTimeout_ms));
          }
      }
      /**
       * @return {!string}
       * @private
       */
      nextTransportId_() {
          return 'c:' + this.id + ':' + this.connectionCount++;
      }
      disconnReceiver_(conn) {
          return everConnected => {
              if (conn === this.conn_) {
                  this.onConnectionLost_(everConnected);
              }
              else if (conn === this.secondaryConn_) {
                  this.log_('Secondary connection lost.');
                  this.onSecondaryConnectionLost_();
              }
              else {
                  this.log_('closing an old connection');
              }
          };
      }
      connReceiver_(conn) {
          return (message) => {
              if (this.state_ != 2 /* DISCONNECTED */) {
                  if (conn === this.rx_) {
                      this.onPrimaryMessageReceived_(message);
                  }
                  else if (conn === this.secondaryConn_) {
                      this.onSecondaryMessageReceived_(message);
                  }
                  else {
                      this.log_('message on old connection');
                  }
              }
          };
      }
      /**
       *
       * @param {Object} dataMsg An arbitrary data message to be sent to the server
       */
      sendRequest(dataMsg) {
          // wrap in a data message envelope and send it on
          const msg = { t: 'd', d: dataMsg };
          this.sendData_(msg);
      }
      tryCleanupConnection() {
          if (this.tx_ === this.secondaryConn_ && this.rx_ === this.secondaryConn_) {
              this.log_('cleaning up and promoting a connection: ' + this.secondaryConn_.connId);
              this.conn_ = this.secondaryConn_;
              this.secondaryConn_ = null;
              // the server will shutdown the old connection
          }
      }
      onSecondaryControl_(controlData) {
          if (MESSAGE_TYPE in controlData) {
              const cmd = controlData[MESSAGE_TYPE];
              if (cmd === SWITCH_ACK) {
                  this.upgradeIfSecondaryHealthy_();
              }
              else if (cmd === CONTROL_RESET) {
                  // Most likely the session wasn't valid. Abandon the switch attempt
                  this.log_('Got a reset on secondary, closing it');
                  this.secondaryConn_.close();
                  // If we were already using this connection for something, than we need to fully close
                  if (this.tx_ === this.secondaryConn_ ||
                      this.rx_ === this.secondaryConn_) {
                      this.close();
                  }
              }
              else if (cmd === CONTROL_PONG) {
                  this.log_('got pong on secondary.');
                  this.secondaryResponsesRequired_--;
                  this.upgradeIfSecondaryHealthy_();
              }
          }
      }
      onSecondaryMessageReceived_(parsedData) {
          const layer = requireKey('t', parsedData);
          const data = requireKey('d', parsedData);
          if (layer == 'c') {
              this.onSecondaryControl_(data);
          }
          else if (layer == 'd') {
              // got a data message, but we're still second connection. Need to buffer it up
              this.pendingDataMessages.push(data);
          }
          else {
              throw new Error('Unknown protocol layer: ' + layer);
          }
      }
      upgradeIfSecondaryHealthy_() {
          if (this.secondaryResponsesRequired_ <= 0) {
              this.log_('Secondary connection is healthy.');
              this.isHealthy_ = true;
              this.secondaryConn_.markConnectionHealthy();
              this.proceedWithUpgrade_();
          }
          else {
              // Send a ping to make sure the connection is healthy.
              this.log_('sending ping on secondary.');
              this.secondaryConn_.send({ t: 'c', d: { t: PING, d: {} } });
          }
      }
      proceedWithUpgrade_() {
          // tell this connection to consider itself open
          this.secondaryConn_.start();
          // send ack
          this.log_('sending client ack on secondary');
          this.secondaryConn_.send({ t: 'c', d: { t: SWITCH_ACK, d: {} } });
          // send end packet on primary transport, switch to sending on this one
          // can receive on this one, buffer responses until end received on primary transport
          this.log_('Ending transmission on primary');
          this.conn_.send({ t: 'c', d: { t: END_TRANSMISSION, d: {} } });
          this.tx_ = this.secondaryConn_;
          this.tryCleanupConnection();
      }
      onPrimaryMessageReceived_(parsedData) {
          // Must refer to parsedData properties in quotes, so closure doesn't touch them.
          const layer = requireKey('t', parsedData);
          const data = requireKey('d', parsedData);
          if (layer == 'c') {
              this.onControl_(data);
          }
          else if (layer == 'd') {
              this.onDataMessage_(data);
          }
      }
      onDataMessage_(message) {
          this.onPrimaryResponse_();
          // We don't do anything with data messages, just kick them up a level
          this.onMessage_(message);
      }
      onPrimaryResponse_() {
          if (!this.isHealthy_) {
              this.primaryResponsesRequired_--;
              if (this.primaryResponsesRequired_ <= 0) {
                  this.log_('Primary connection is healthy.');
                  this.isHealthy_ = true;
                  this.conn_.markConnectionHealthy();
              }
          }
      }
      onControl_(controlData) {
          const cmd = requireKey(MESSAGE_TYPE, controlData);
          if (MESSAGE_DATA in controlData) {
              const payload = controlData[MESSAGE_DATA];
              if (cmd === SERVER_HELLO) {
                  this.onHandshake_(payload);
              }
              else if (cmd === END_TRANSMISSION) {
                  this.log_('recvd end transmission on primary');
                  this.rx_ = this.secondaryConn_;
                  for (let i = 0; i < this.pendingDataMessages.length; ++i) {
                      this.onDataMessage_(this.pendingDataMessages[i]);
                  }
                  this.pendingDataMessages = [];
                  this.tryCleanupConnection();
              }
              else if (cmd === CONTROL_SHUTDOWN) {
                  // This was previously the 'onKill' callback passed to the lower-level connection
                  // payload in this case is the reason for the shutdown. Generally a human-readable error
                  this.onConnectionShutdown_(payload);
              }
              else if (cmd === CONTROL_RESET) {
                  // payload in this case is the host we should contact
                  this.onReset_(payload);
              }
              else if (cmd === CONTROL_ERROR) {
                  error('Server Error: ' + payload);
              }
              else if (cmd === CONTROL_PONG) {
                  this.log_('got pong on primary.');
                  this.onPrimaryResponse_();
                  this.sendPingOnPrimaryIfNecessary_();
              }
              else {
                  error('Unknown control packet command: ' + cmd);
              }
          }
      }
      /**
       *
       * @param {Object} handshake The handshake data returned from the server
       * @private
       */
      onHandshake_(handshake) {
          const timestamp = handshake.ts;
          const version = handshake.v;
          const host = handshake.h;
          this.sessionId = handshake.s;
          this.repoInfo_.updateHost(host);
          // if we've already closed the connection, then don't bother trying to progress further
          if (this.state_ == 0 /* CONNECTING */) {
              this.conn_.start();
              this.onConnectionEstablished_(this.conn_, timestamp);
              if (PROTOCOL_VERSION !== version) {
                  warn('Protocol version mismatch detected');
              }
              // TODO: do we want to upgrade? when? maybe a delay?
              this.tryStartUpgrade_();
          }
      }
      tryStartUpgrade_() {
          const conn = this.transportManager_.upgradeTransport();
          if (conn) {
              this.startUpgrade_(conn);
          }
      }
      startUpgrade_(conn) {
          this.secondaryConn_ = new conn(this.nextTransportId_(), this.repoInfo_, this.sessionId);
          // For certain transports (WebSockets), we need to send and receive several messages back and forth before we
          // can consider the transport healthy.
          this.secondaryResponsesRequired_ =
              conn['responsesRequiredToBeHealthy'] || 0;
          const onMessage = this.connReceiver_(this.secondaryConn_);
          const onDisconnect = this.disconnReceiver_(this.secondaryConn_);
          this.secondaryConn_.open(onMessage, onDisconnect);
          // If we haven't successfully upgraded after UPGRADE_TIMEOUT, give up and kill the secondary.
          setTimeoutNonBlocking(() => {
              if (this.secondaryConn_) {
                  this.log_('Timed out trying to upgrade.');
                  this.secondaryConn_.close();
              }
          }, Math.floor(UPGRADE_TIMEOUT));
      }
      onReset_(host) {
          this.log_('Reset packet received.  New host: ' + host);
          this.repoInfo_.updateHost(host);
          // TODO: if we're already "connected", we need to trigger a disconnect at the next layer up.
          // We don't currently support resets after the connection has already been established
          if (this.state_ === 1 /* CONNECTED */) {
              this.close();
          }
          else {
              // Close whatever connections we have open and start again.
              this.closeConnections_();
              this.start_();
          }
      }
      onConnectionEstablished_(conn, timestamp) {
          this.log_('Realtime connection established.');
          this.conn_ = conn;
          this.state_ = 1 /* CONNECTED */;
          if (this.onReady_) {
              this.onReady_(timestamp, this.sessionId);
              this.onReady_ = null;
          }
          // If after 5 seconds we haven't sent enough requests to the server to get the connection healthy,
          // send some pings.
          if (this.primaryResponsesRequired_ === 0) {
              this.log_('Primary connection is healthy.');
              this.isHealthy_ = true;
          }
          else {
              setTimeoutNonBlocking(() => {
                  this.sendPingOnPrimaryIfNecessary_();
              }, Math.floor(DELAY_BEFORE_SENDING_EXTRA_REQUESTS));
          }
      }
      sendPingOnPrimaryIfNecessary_() {
          // If the connection isn't considered healthy yet, we'll send a noop ping packet request.
          if (!this.isHealthy_ && this.state_ === 1 /* CONNECTED */) {
              this.log_('sending ping on primary.');
              this.sendData_({ t: 'c', d: { t: PING, d: {} } });
          }
      }
      onSecondaryConnectionLost_() {
          const conn = this.secondaryConn_;
          this.secondaryConn_ = null;
          if (this.tx_ === conn || this.rx_ === conn) {
              // we are relying on this connection already in some capacity. Therefore, a failure is real
              this.close();
          }
      }
      /**
       *
       * @param {boolean} everConnected Whether or not the connection ever reached a server. Used to determine if
       * we should flush the host cache
       * @private
       */
      onConnectionLost_(everConnected) {
          this.conn_ = null;
          // NOTE: IF you're seeing a Firefox error for this line, I think it might be because it's getting
          // called on window close and RealtimeState.CONNECTING is no longer defined.  Just a guess.
          if (!everConnected && this.state_ === 0 /* CONNECTING */) {
              this.log_('Realtime connection failed.');
              // Since we failed to connect at all, clear any cached entry for this namespace in case the machine went away
              if (this.repoInfo_.isCacheableHost()) {
                  PersistentStorage.remove('host:' + this.repoInfo_.host);
                  // reset the internal host to what we would show the user, i.e. <ns>.firebaseio.com
                  this.repoInfo_.internalHost = this.repoInfo_.host;
              }
          }
          else if (this.state_ === 1 /* CONNECTED */) {
              this.log_('Realtime connection lost.');
          }
          this.close();
      }
      /**
       *
       * @param {string} reason
       * @private
       */
      onConnectionShutdown_(reason) {
          this.log_('Connection shutdown command received. Shutting down...');
          if (this.onKill_) {
              this.onKill_(reason);
              this.onKill_ = null;
          }
          // We intentionally don't want to fire onDisconnect (kill is a different case),
          // so clear the callback.
          this.onDisconnect_ = null;
          this.close();
      }
      sendData_(data) {
          if (this.state_ !== 1 /* CONNECTED */) {
              throw 'Connection is not connected';
          }
          else {
              this.tx_.send(data);
          }
      }
      /**
       * Cleans up this connection, calling the appropriate callbacks
       */
      close() {
          if (this.state_ !== 2 /* DISCONNECTED */) {
              this.log_('Closing realtime connection.');
              this.state_ = 2 /* DISCONNECTED */;
              this.closeConnections_();
              if (this.onDisconnect_) {
                  this.onDisconnect_();
                  this.onDisconnect_ = null;
              }
          }
      }
      /**
       *
       * @private
       */
      closeConnections_() {
          this.log_('Shutting down all connections');
          if (this.conn_) {
              this.conn_.close();
              this.conn_ = null;
          }
          if (this.secondaryConn_) {
              this.secondaryConn_.close();
              this.secondaryConn_ = null;
          }
          if (this.healthyTimeout_) {
              clearTimeout(this.healthyTimeout_);
              this.healthyTimeout_ = null;
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Interface defining the set of actions that can be performed against the Firebase server
   * (basically corresponds to our wire protocol).
   *
   * @interface
   */
  class ServerActions {
      /**
       * @param {string} pathString
       * @param {*} data
       * @param {function(string, string)=} onComplete
       * @param {string=} hash
       */
      put(pathString, data, onComplete, hash) { }
      /**
       * @param {string} pathString
       * @param {*} data
       * @param {function(string, ?string)} onComplete
       * @param {string=} hash
       */
      merge(pathString, data, onComplete, hash) { }
      /**
       * Refreshes the auth token for the current connection.
       * @param {string} token The authentication token
       */
      refreshAuthToken(token) { }
      /**
       * @param {string} pathString
       * @param {*} data
       * @param {function(string, string)=} onComplete
       */
      onDisconnectPut(pathString, data, onComplete) { }
      /**
       * @param {string} pathString
       * @param {*} data
       * @param {function(string, string)=} onComplete
       */
      onDisconnectMerge(pathString, data, onComplete) { }
      /**
       * @param {string} pathString
       * @param {function(string, string)=} onComplete
       */
      onDisconnectCancel(pathString, onComplete) { }
      /**
       * @param {Object.<string, *>} stats
       */
      reportStats(stats) { }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const RECONNECT_MIN_DELAY = 1000;
  const RECONNECT_MAX_DELAY_DEFAULT = 60 * 5 * 1000; // 5 minutes in milliseconds (Case: 1858)
  const RECONNECT_MAX_DELAY_FOR_ADMINS = 30 * 1000; // 30 seconds for admin clients (likely to be a backend server)
  const RECONNECT_DELAY_MULTIPLIER = 1.3;
  const RECONNECT_DELAY_RESET_TIMEOUT = 30000; // Reset delay back to MIN_DELAY after being connected for 30sec.
  const SERVER_KILL_INTERRUPT_REASON = 'server_kill';
  // If auth fails repeatedly, we'll assume something is wrong and log a warning / back off.
  const INVALID_AUTH_TOKEN_THRESHOLD = 3;
  /**
   * Firebase connection.  Abstracts wire protocol and handles reconnecting.
   *
   * NOTE: All JSON objects sent to the realtime connection must have property names enclosed
   * in quotes to make sure the closure compiler does not minify them.
   */
  class PersistentConnection extends ServerActions {
      /**
       * @implements {ServerActions}
       * @param {!RepoInfo} repoInfo_ Data about the namespace we are connecting to
       * @param {function(string, *, boolean, ?number)} onDataUpdate_ A callback for new data from the server
       * @param onConnectStatus_
       * @param onServerInfoUpdate_
       * @param authTokenProvider_
       * @param authOverride_
       */
      constructor(repoInfo_, onDataUpdate_, onConnectStatus_, onServerInfoUpdate_, authTokenProvider_, authOverride_) {
          super();
          this.repoInfo_ = repoInfo_;
          this.onDataUpdate_ = onDataUpdate_;
          this.onConnectStatus_ = onConnectStatus_;
          this.onServerInfoUpdate_ = onServerInfoUpdate_;
          this.authTokenProvider_ = authTokenProvider_;
          this.authOverride_ = authOverride_;
          // Used for diagnostic logging.
          this.id = PersistentConnection.nextPersistentConnectionId_++;
          this.log_ = logWrapper('p:' + this.id + ':');
          /** @private {Object} */
          this.interruptReasons_ = {};
          this.listens_ = {};
          this.outstandingPuts_ = [];
          this.outstandingPutCount_ = 0;
          this.onDisconnectRequestQueue_ = [];
          this.connected_ = false;
          this.reconnectDelay_ = RECONNECT_MIN_DELAY;
          this.maxReconnectDelay_ = RECONNECT_MAX_DELAY_DEFAULT;
          this.securityDebugCallback_ = null;
          this.lastSessionId = null;
          /** @private {number|null} */
          this.establishConnectionTimer_ = null;
          /** @private {boolean} */
          this.visible_ = false;
          // Before we get connected, we keep a queue of pending messages to send.
          this.requestCBHash_ = {};
          this.requestNumber_ = 0;
          /** @private {?{
           *   sendRequest(Object),
           *   close()
           * }} */
          this.realtime_ = null;
          /** @private {string|null} */
          this.authToken_ = null;
          this.forceTokenRefresh_ = false;
          this.invalidAuthTokenCount_ = 0;
          this.firstConnection_ = true;
          this.lastConnectionAttemptTime_ = null;
          this.lastConnectionEstablishedTime_ = null;
          if (authOverride_ && !isNodeSdk()) {
              throw new Error('Auth override specified in options, but not supported on non Node.js platforms');
          }
          this.scheduleConnect_(0);
          VisibilityMonitor.getInstance().on('visible', this.onVisible_, this);
          if (repoInfo_.host.indexOf('fblocal') === -1) {
              OnlineMonitor.getInstance().on('online', this.onOnline_, this);
          }
      }
      /**
       * @param {!string} action
       * @param {*} body
       * @param {function(*)=} onResponse
       * @protected
       */
      sendRequest(action, body, onResponse) {
          const curReqNum = ++this.requestNumber_;
          const msg = { r: curReqNum, a: action, b: body };
          this.log_(stringify(msg));
          assert(this.connected_, "sendRequest call when we're not connected not allowed.");
          this.realtime_.sendRequest(msg);
          if (onResponse) {
              this.requestCBHash_[curReqNum] = onResponse;
          }
      }
      /**
       * @inheritDoc
       */
      listen(query, currentHashFn, tag, onComplete) {
          const queryId = query.queryIdentifier();
          const pathString = query.path.toString();
          this.log_('Listen called for ' + pathString + ' ' + queryId);
          this.listens_[pathString] = this.listens_[pathString] || {};
          assert(query.getQueryParams().isDefault() ||
              !query.getQueryParams().loadsAllData(), 'listen() called for non-default but complete query');
          assert(!this.listens_[pathString][queryId], 'listen() called twice for same path/queryId.');
          const listenSpec = {
              onComplete: onComplete,
              hashFn: currentHashFn,
              query: query,
              tag: tag
          };
          this.listens_[pathString][queryId] = listenSpec;
          if (this.connected_) {
              this.sendListen_(listenSpec);
          }
      }
      /**
       * @param {!{onComplete(),
       *           hashFn():!string,
       *           query: !Query,
       *           tag: ?number}} listenSpec
       * @private
       */
      sendListen_(listenSpec) {
          const query = listenSpec.query;
          const pathString = query.path.toString();
          const queryId = query.queryIdentifier();
          this.log_('Listen on ' + pathString + ' for ' + queryId);
          const req = { /*path*/ p: pathString };
          const action = 'q';
          // Only bother to send query if it's non-default.
          if (listenSpec.tag) {
              req['q'] = query.queryObject();
              req['t'] = listenSpec.tag;
          }
          req[ /*hash*/'h'] = listenSpec.hashFn();
          this.sendRequest(action, req, (message) => {
              const payload = message[ /*data*/'d'];
              const status = message[ /*status*/'s'];
              // print warnings in any case...
              PersistentConnection.warnOnListenWarnings_(payload, query);
              const currentListenSpec = this.listens_[pathString] && this.listens_[pathString][queryId];
              // only trigger actions if the listen hasn't been removed and readded
              if (currentListenSpec === listenSpec) {
                  this.log_('listen response', message);
                  if (status !== 'ok') {
                      this.removeListen_(pathString, queryId);
                  }
                  if (listenSpec.onComplete) {
                      listenSpec.onComplete(status, payload);
                  }
              }
          });
      }
      /**
       * @param {*} payload
       * @param {!Query} query
       * @private
       */
      static warnOnListenWarnings_(payload, query) {
          if (payload && typeof payload === 'object' && contains(payload, 'w')) {
              const warnings = safeGet(payload, 'w');
              if (Array.isArray(warnings) && ~warnings.indexOf('no_index')) {
                  const indexSpec = '".indexOn": "' +
                      query
                          .getQueryParams()
                          .getIndex()
                          .toString() +
                      '"';
                  const indexPath = query.path.toString();
                  warn(`Using an unspecified index. Your data will be downloaded and ` +
                      `filtered on the client. Consider adding ${indexSpec} at ` +
                      `${indexPath} to your security rules for better performance.`);
              }
          }
      }
      /**
       * @inheritDoc
       */
      refreshAuthToken(token) {
          this.authToken_ = token;
          this.log_('Auth token refreshed');
          if (this.authToken_) {
              this.tryAuth();
          }
          else {
              //If we're connected we want to let the server know to unauthenticate us. If we're not connected, simply delete
              //the credential so we dont become authenticated next time we connect.
              if (this.connected_) {
                  this.sendRequest('unauth', {}, () => { });
              }
          }
          this.reduceReconnectDelayIfAdminCredential_(token);
      }
      /**
       * @param {!string} credential
       * @private
       */
      reduceReconnectDelayIfAdminCredential_(credential) {
          // NOTE: This isn't intended to be bulletproof (a malicious developer can always just modify the client).
          // Additionally, we don't bother resetting the max delay back to the default if auth fails / expires.
          const isFirebaseSecret = credential && credential.length === 40;
          if (isFirebaseSecret || isAdmin(credential)) {
              this.log_('Admin auth credential detected.  Reducing max reconnect time.');
              this.maxReconnectDelay_ = RECONNECT_MAX_DELAY_FOR_ADMINS;
          }
      }
      /**
       * Attempts to authenticate with the given credentials. If the authentication attempt fails, it's triggered like
       * a auth revoked (the connection is closed).
       */
      tryAuth() {
          if (this.connected_ && this.authToken_) {
              const token = this.authToken_;
              const authMethod = isValidFormat(token) ? 'auth' : 'gauth';
              const requestData = { cred: token };
              if (this.authOverride_ === null) {
                  requestData['noauth'] = true;
              }
              else if (typeof this.authOverride_ === 'object') {
                  requestData['authvar'] = this.authOverride_;
              }
              this.sendRequest(authMethod, requestData, (res) => {
                  const status = res[ /*status*/'s'];
                  const data = res[ /*data*/'d'] || 'error';
                  if (this.authToken_ === token) {
                      if (status === 'ok') {
                          this.invalidAuthTokenCount_ = 0;
                      }
                      else {
                          // Triggers reconnect and force refresh for auth token
                          this.onAuthRevoked_(status, data);
                      }
                  }
              });
          }
      }
      /**
       * @inheritDoc
       */
      unlisten(query, tag) {
          const pathString = query.path.toString();
          const queryId = query.queryIdentifier();
          this.log_('Unlisten called for ' + pathString + ' ' + queryId);
          assert(query.getQueryParams().isDefault() ||
              !query.getQueryParams().loadsAllData(), 'unlisten() called for non-default but complete query');
          const listen = this.removeListen_(pathString, queryId);
          if (listen && this.connected_) {
              this.sendUnlisten_(pathString, queryId, query.queryObject(), tag);
          }
      }
      sendUnlisten_(pathString, queryId, queryObj, tag) {
          this.log_('Unlisten on ' + pathString + ' for ' + queryId);
          const req = { /*path*/ p: pathString };
          const action = 'n';
          // Only bother sending queryId if it's non-default.
          if (tag) {
              req['q'] = queryObj;
              req['t'] = tag;
          }
          this.sendRequest(action, req);
      }
      /**
       * @inheritDoc
       */
      onDisconnectPut(pathString, data, onComplete) {
          if (this.connected_) {
              this.sendOnDisconnect_('o', pathString, data, onComplete);
          }
          else {
              this.onDisconnectRequestQueue_.push({
                  pathString,
                  action: 'o',
                  data,
                  onComplete
              });
          }
      }
      /**
       * @inheritDoc
       */
      onDisconnectMerge(pathString, data, onComplete) {
          if (this.connected_) {
              this.sendOnDisconnect_('om', pathString, data, onComplete);
          }
          else {
              this.onDisconnectRequestQueue_.push({
                  pathString,
                  action: 'om',
                  data,
                  onComplete
              });
          }
      }
      /**
       * @inheritDoc
       */
      onDisconnectCancel(pathString, onComplete) {
          if (this.connected_) {
              this.sendOnDisconnect_('oc', pathString, null, onComplete);
          }
          else {
              this.onDisconnectRequestQueue_.push({
                  pathString,
                  action: 'oc',
                  data: null,
                  onComplete
              });
          }
      }
      sendOnDisconnect_(action, pathString, data, onComplete) {
          const request = { /*path*/ p: pathString, /*data*/ d: data };
          this.log_('onDisconnect ' + action, request);
          this.sendRequest(action, request, (response) => {
              if (onComplete) {
                  setTimeout(function () {
                      onComplete(response[ /*status*/'s'], response[ /* data */'d']);
                  }, Math.floor(0));
              }
          });
      }
      /**
       * @inheritDoc
       */
      put(pathString, data, onComplete, hash) {
          this.putInternal('p', pathString, data, onComplete, hash);
      }
      /**
       * @inheritDoc
       */
      merge(pathString, data, onComplete, hash) {
          this.putInternal('m', pathString, data, onComplete, hash);
      }
      putInternal(action, pathString, data, onComplete, hash) {
          const request = {
              /*path*/ p: pathString,
              /*data*/ d: data
          };
          if (hash !== undefined)
              request[ /*hash*/'h'] = hash;
          // TODO: Only keep track of the most recent put for a given path?
          this.outstandingPuts_.push({
              action,
              request,
              onComplete
          });
          this.outstandingPutCount_++;
          const index = this.outstandingPuts_.length - 1;
          if (this.connected_) {
              this.sendPut_(index);
          }
          else {
              this.log_('Buffering put: ' + pathString);
          }
      }
      sendPut_(index) {
          const action = this.outstandingPuts_[index].action;
          const request = this.outstandingPuts_[index].request;
          const onComplete = this.outstandingPuts_[index].onComplete;
          this.outstandingPuts_[index].queued = this.connected_;
          this.sendRequest(action, request, (message) => {
              this.log_(action + ' response', message);
              delete this.outstandingPuts_[index];
              this.outstandingPutCount_--;
              // Clean up array occasionally.
              if (this.outstandingPutCount_ === 0) {
                  this.outstandingPuts_ = [];
              }
              if (onComplete)
                  onComplete(message[ /*status*/'s'], message[ /* data */'d']);
          });
      }
      /**
       * @inheritDoc
       */
      reportStats(stats) {
          // If we're not connected, we just drop the stats.
          if (this.connected_) {
              const request = { /*counters*/ c: stats };
              this.log_('reportStats', request);
              this.sendRequest(/*stats*/ 's', request, result => {
                  const status = result[ /*status*/'s'];
                  if (status !== 'ok') {
                      const errorReason = result[ /* data */'d'];
                      this.log_('reportStats', 'Error sending stats: ' + errorReason);
                  }
              });
          }
      }
      /**
       * @param {*} message
       * @private
       */
      onDataMessage_(message) {
          if ('r' in message) {
              // this is a response
              this.log_('from server: ' + stringify(message));
              const reqNum = message['r'];
              const onResponse = this.requestCBHash_[reqNum];
              if (onResponse) {
                  delete this.requestCBHash_[reqNum];
                  onResponse(message[ /*body*/'b']);
              }
          }
          else if ('error' in message) {
              throw 'A server-side error has occurred: ' + message['error'];
          }
          else if ('a' in message) {
              // a and b are action and body, respectively
              this.onDataPush_(message['a'], message['b']);
          }
      }
      onDataPush_(action, body) {
          this.log_('handleServerMessage', action, body);
          if (action === 'd')
              this.onDataUpdate_(body[ /*path*/'p'], body[ /*data*/'d'], 
              /*isMerge*/ false, body['t']);
          else if (action === 'm')
              this.onDataUpdate_(body[ /*path*/'p'], body[ /*data*/'d'], 
              /*isMerge=*/ true, body['t']);
          else if (action === 'c')
              this.onListenRevoked_(body[ /*path*/'p'], body[ /*query*/'q']);
          else if (action === 'ac')
              this.onAuthRevoked_(body[ /*status code*/'s'], body[ /* explanation */'d']);
          else if (action === 'sd')
              this.onSecurityDebugPacket_(body);
          else
              error('Unrecognized action received from server: ' +
                  stringify(action) +
                  '\nAre you using the latest client?');
      }
      onReady_(timestamp, sessionId) {
          this.log_('connection ready');
          this.connected_ = true;
          this.lastConnectionEstablishedTime_ = new Date().getTime();
          this.handleTimestamp_(timestamp);
          this.lastSessionId = sessionId;
          if (this.firstConnection_) {
              this.sendConnectStats_();
          }
          this.restoreState_();
          this.firstConnection_ = false;
          this.onConnectStatus_(true);
      }
      scheduleConnect_(timeout) {
          assert(!this.realtime_, "Scheduling a connect when we're already connected/ing?");
          if (this.establishConnectionTimer_) {
              clearTimeout(this.establishConnectionTimer_);
          }
          // NOTE: Even when timeout is 0, it's important to do a setTimeout to work around an infuriating "Security Error" in
          // Firefox when trying to write to our long-polling iframe in some scenarios (e.g. Forge or our unit tests).
          this.establishConnectionTimer_ = setTimeout(() => {
              this.establishConnectionTimer_ = null;
              this.establishConnection_();
          }, Math.floor(timeout));
      }
      /**
       * @param {boolean} visible
       * @private
       */
      onVisible_(visible) {
          // NOTE: Tabbing away and back to a window will defeat our reconnect backoff, but I think that's fine.
          if (visible &&
              !this.visible_ &&
              this.reconnectDelay_ === this.maxReconnectDelay_) {
              this.log_('Window became visible.  Reducing delay.');
              this.reconnectDelay_ = RECONNECT_MIN_DELAY;
              if (!this.realtime_) {
                  this.scheduleConnect_(0);
              }
          }
          this.visible_ = visible;
      }
      onOnline_(online) {
          if (online) {
              this.log_('Browser went online.');
              this.reconnectDelay_ = RECONNECT_MIN_DELAY;
              if (!this.realtime_) {
                  this.scheduleConnect_(0);
              }
          }
          else {
              this.log_('Browser went offline.  Killing connection.');
              if (this.realtime_) {
                  this.realtime_.close();
              }
          }
      }
      onRealtimeDisconnect_() {
          this.log_('data client disconnected');
          this.connected_ = false;
          this.realtime_ = null;
          // Since we don't know if our sent transactions succeeded or not, we need to cancel them.
          this.cancelSentTransactions_();
          // Clear out the pending requests.
          this.requestCBHash_ = {};
          if (this.shouldReconnect_()) {
              if (!this.visible_) {
                  this.log_("Window isn't visible.  Delaying reconnect.");
                  this.reconnectDelay_ = this.maxReconnectDelay_;
                  this.lastConnectionAttemptTime_ = new Date().getTime();
              }
              else if (this.lastConnectionEstablishedTime_) {
                  // If we've been connected long enough, reset reconnect delay to minimum.
                  const timeSinceLastConnectSucceeded = new Date().getTime() - this.lastConnectionEstablishedTime_;
                  if (timeSinceLastConnectSucceeded > RECONNECT_DELAY_RESET_TIMEOUT)
                      this.reconnectDelay_ = RECONNECT_MIN_DELAY;
                  this.lastConnectionEstablishedTime_ = null;
              }
              const timeSinceLastConnectAttempt = new Date().getTime() - this.lastConnectionAttemptTime_;
              let reconnectDelay = Math.max(0, this.reconnectDelay_ - timeSinceLastConnectAttempt);
              reconnectDelay = Math.random() * reconnectDelay;
              this.log_('Trying to reconnect in ' + reconnectDelay + 'ms');
              this.scheduleConnect_(reconnectDelay);
              // Adjust reconnect delay for next time.
              this.reconnectDelay_ = Math.min(this.maxReconnectDelay_, this.reconnectDelay_ * RECONNECT_DELAY_MULTIPLIER);
          }
          this.onConnectStatus_(false);
      }
      establishConnection_() {
          if (this.shouldReconnect_()) {
              this.log_('Making a connection attempt');
              this.lastConnectionAttemptTime_ = new Date().getTime();
              this.lastConnectionEstablishedTime_ = null;
              const onDataMessage = this.onDataMessage_.bind(this);
              const onReady = this.onReady_.bind(this);
              const onDisconnect = this.onRealtimeDisconnect_.bind(this);
              const connId = this.id + ':' + PersistentConnection.nextConnectionId_++;
              const self = this;
              const lastSessionId = this.lastSessionId;
              let canceled = false;
              let connection = null;
              const closeFn = function () {
                  if (connection) {
                      connection.close();
                  }
                  else {
                      canceled = true;
                      onDisconnect();
                  }
              };
              const sendRequestFn = function (msg) {
                  assert(connection, "sendRequest call when we're not connected not allowed.");
                  connection.sendRequest(msg);
              };
              this.realtime_ = {
                  close: closeFn,
                  sendRequest: sendRequestFn
              };
              const forceRefresh = this.forceTokenRefresh_;
              this.forceTokenRefresh_ = false;
              // First fetch auth token, and establish connection after fetching the token was successful
              this.authTokenProvider_
                  .getToken(forceRefresh)
                  .then(function (result) {
                  if (!canceled) {
                      log('getToken() completed. Creating connection.');
                      self.authToken_ = result && result.accessToken;
                      connection = new Connection(connId, self.repoInfo_, onDataMessage, onReady, onDisconnect, 
                      /* onKill= */ function (reason) {
                          warn(reason + ' (' + self.repoInfo_.toString() + ')');
                          self.interrupt(SERVER_KILL_INTERRUPT_REASON);
                      }, lastSessionId);
                  }
                  else {
                      log('getToken() completed but was canceled');
                  }
              })
                  .then(null, function (error) {
                  self.log_('Failed to get token: ' + error);
                  if (!canceled) {
                      if (CONSTANTS.NODE_ADMIN) {
                          // This may be a critical error for the Admin Node.js SDK, so log a warning.
                          // But getToken() may also just have temporarily failed, so we still want to
                          // continue retrying.
                          warn(error);
                      }
                      closeFn();
                  }
              });
          }
      }
      /**
       * @param {string} reason
       */
      interrupt(reason) {
          log('Interrupting connection for reason: ' + reason);
          this.interruptReasons_[reason] = true;
          if (this.realtime_) {
              this.realtime_.close();
          }
          else {
              if (this.establishConnectionTimer_) {
                  clearTimeout(this.establishConnectionTimer_);
                  this.establishConnectionTimer_ = null;
              }
              if (this.connected_) {
                  this.onRealtimeDisconnect_();
              }
          }
      }
      /**
       * @param {string} reason
       */
      resume(reason) {
          log('Resuming connection for reason: ' + reason);
          delete this.interruptReasons_[reason];
          if (isEmpty(this.interruptReasons_)) {
              this.reconnectDelay_ = RECONNECT_MIN_DELAY;
              if (!this.realtime_) {
                  this.scheduleConnect_(0);
              }
          }
      }
      handleTimestamp_(timestamp) {
          const delta = timestamp - new Date().getTime();
          this.onServerInfoUpdate_({ serverTimeOffset: delta });
      }
      cancelSentTransactions_() {
          for (let i = 0; i < this.outstandingPuts_.length; i++) {
              const put = this.outstandingPuts_[i];
              if (put && /*hash*/ 'h' in put.request && put.queued) {
                  if (put.onComplete)
                      put.onComplete('disconnect');
                  delete this.outstandingPuts_[i];
                  this.outstandingPutCount_--;
              }
          }
          // Clean up array occasionally.
          if (this.outstandingPutCount_ === 0)
              this.outstandingPuts_ = [];
      }
      /**
       * @param {!string} pathString
       * @param {Array.<*>=} query
       * @private
       */
      onListenRevoked_(pathString, query) {
          // Remove the listen and manufacture a "permission_denied" error for the failed listen.
          let queryId;
          if (!query) {
              queryId = 'default';
          }
          else {
              queryId = query.map(q => ObjectToUniqueKey(q)).join('$');
          }
          const listen = this.removeListen_(pathString, queryId);
          if (listen && listen.onComplete)
              listen.onComplete('permission_denied');
      }
      /**
       * @param {!string} pathString
       * @param {!string} queryId
       * @return {{queries:Array.<Query>, onComplete:function(string)}}
       * @private
       */
      removeListen_(pathString, queryId) {
          const normalizedPathString = new Path(pathString).toString(); // normalize path.
          let listen;
          if (this.listens_[normalizedPathString] !== undefined) {
              listen = this.listens_[normalizedPathString][queryId];
              delete this.listens_[normalizedPathString][queryId];
              if (getCount(this.listens_[normalizedPathString]) === 0) {
                  delete this.listens_[normalizedPathString];
              }
          }
          else {
              // all listens for this path has already been removed
              listen = undefined;
          }
          return listen;
      }
      onAuthRevoked_(statusCode, explanation) {
          log('Auth token revoked: ' + statusCode + '/' + explanation);
          this.authToken_ = null;
          this.forceTokenRefresh_ = true;
          this.realtime_.close();
          if (statusCode === 'invalid_token' || statusCode === 'permission_denied') {
              // We'll wait a couple times before logging the warning / increasing the
              // retry period since oauth tokens will report as "invalid" if they're
              // just expired. Plus there may be transient issues that resolve themselves.
              this.invalidAuthTokenCount_++;
              if (this.invalidAuthTokenCount_ >= INVALID_AUTH_TOKEN_THRESHOLD) {
                  // Set a long reconnect delay because recovery is unlikely
                  this.reconnectDelay_ = RECONNECT_MAX_DELAY_FOR_ADMINS;
                  // Notify the auth token provider that the token is invalid, which will log
                  // a warning
                  this.authTokenProvider_.notifyForInvalidToken();
              }
          }
      }
      onSecurityDebugPacket_(body) {
          if (this.securityDebugCallback_) {
              this.securityDebugCallback_(body);
          }
          else {
              if ('msg' in body) {
                  console.log('FIREBASE: ' + body['msg'].replace('\n', '\nFIREBASE: '));
              }
          }
      }
      restoreState_() {
          //Re-authenticate ourselves if we have a credential stored.
          this.tryAuth();
          // Puts depend on having received the corresponding data update from the server before they complete, so we must
          // make sure to send listens before puts.
          forEach(this.listens_, (pathString, queries) => {
              forEach(queries, (key, listenSpec) => {
                  this.sendListen_(listenSpec);
              });
          });
          for (let i = 0; i < this.outstandingPuts_.length; i++) {
              if (this.outstandingPuts_[i])
                  this.sendPut_(i);
          }
          while (this.onDisconnectRequestQueue_.length) {
              const request = this.onDisconnectRequestQueue_.shift();
              this.sendOnDisconnect_(request.action, request.pathString, request.data, request.onComplete);
          }
      }
      /**
       * Sends client stats for first connection
       * @private
       */
      sendConnectStats_() {
          const stats = {};
          let clientName = 'js';
          if (CONSTANTS.NODE_ADMIN) {
              clientName = 'admin_node';
          }
          else if (CONSTANTS.NODE_CLIENT) {
              clientName = 'node';
          }
          stats['sdk.' + clientName + '.' + firebase.SDK_VERSION.replace(/\./g, '-')] = 1;
          if (isMobileCordova()) {
              stats['framework.cordova'] = 1;
          }
          else if (isReactNative()) {
              stats['framework.reactnative'] = 1;
          }
          this.reportStats(stats);
      }
      /**
       * @return {boolean}
       * @private
       */
      shouldReconnect_() {
          const online = OnlineMonitor.getInstance().currentlyOnline();
          return isEmpty(this.interruptReasons_) && online;
      }
  }
  /**
   * @private
   */
  PersistentConnection.nextPersistentConnectionId_ = 0;
  /**
   * Counter for number of connections created. Mainly used for tagging in the logs
   * @type {number}
   * @private
   */
  PersistentConnection.nextConnectionId_ = 0;
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * An implementation of ServerActions that communicates with the server via REST requests.
   * This is mostly useful for compatibility with crawlers, where we don't want to spin up a full
   * persistent connection (using WebSockets or long-polling)
   */
  class ReadonlyRestClient extends ServerActions {
      /**
       * @param {!RepoInfo} repoInfo_ Data about the namespace we are connecting to
       * @param {function(string, *, boolean, ?number)} onDataUpdate_ A callback for new data from the server
       * @param {AuthTokenProvider} authTokenProvider_
       * @implements {ServerActions}
       */
      constructor(repoInfo_, onDataUpdate_, authTokenProvider_) {
          super();
          this.repoInfo_ = repoInfo_;
          this.onDataUpdate_ = onDataUpdate_;
          this.authTokenProvider_ = authTokenProvider_;
          /** @private {function(...[*])} */
          this.log_ = logWrapper('p:rest:');
          /**
           * We don't actually need to track listens, except to prevent us calling an onComplete for a listen
           * that's been removed. :-/
           *
           * @private {!Object.<string, !Object>}
           */
          this.listens_ = {};
      }
      reportStats(stats) {
          throw new Error('Method not implemented.');
      }
      /**
       * @param {!Query} query
       * @param {?number=} tag
       * @return {string}
       * @private
       */
      static getListenId_(query, tag) {
          if (tag !== undefined) {
              return 'tag$' + tag;
          }
          else {
              assert(query.getQueryParams().isDefault(), "should have a tag if it's not a default query.");
              return query.path.toString();
          }
      }
      /** @inheritDoc */
      listen(query, currentHashFn, tag, onComplete) {
          const pathString = query.path.toString();
          this.log_('Listen called for ' + pathString + ' ' + query.queryIdentifier());
          // Mark this listener so we can tell if it's removed.
          const listenId = ReadonlyRestClient.getListenId_(query, tag);
          const thisListen = {};
          this.listens_[listenId] = thisListen;
          const queryStringParameters = query
              .getQueryParams()
              .toRestQueryStringParameters();
          this.restRequest_(pathString + '.json', queryStringParameters, (error, result) => {
              let data = result;
              if (error === 404) {
                  data = null;
                  error = null;
              }
              if (error === null) {
                  this.onDataUpdate_(pathString, data, /*isMerge=*/ false, tag);
              }
              if (safeGet(this.listens_, listenId) === thisListen) {
                  let status;
                  if (!error) {
                      status = 'ok';
                  }
                  else if (error == 401) {
                      status = 'permission_denied';
                  }
                  else {
                      status = 'rest_error:' + error;
                  }
                  onComplete(status, null);
              }
          });
      }
      /** @inheritDoc */
      unlisten(query, tag) {
          const listenId = ReadonlyRestClient.getListenId_(query, tag);
          delete this.listens_[listenId];
      }
      /** @inheritDoc */
      refreshAuthToken(token) {
          // no-op since we just always call getToken.
      }
      /**
       * Performs a REST request to the given path, with the provided query string parameters,
       * and any auth credentials we have.
       *
       * @param {!string} pathString
       * @param {!Object.<string, *>} queryStringParameters
       * @param {?function(?number, *=)} callback
       * @private
       */
      restRequest_(pathString, queryStringParameters = {}, callback) {
          queryStringParameters['format'] = 'export';
          this.authTokenProvider_
              .getToken(/*forceRefresh=*/ false)
              .then(authTokenData => {
              const authToken = authTokenData && authTokenData.accessToken;
              if (authToken) {
                  queryStringParameters['auth'] = authToken;
              }
              const url = (this.repoInfo_.secure ? 'https://' : 'http://') +
                  this.repoInfo_.host +
                  pathString +
                  '?' +
                  'ns=' +
                  this.repoInfo_.namespace +
                  querystring(queryStringParameters);
              this.log_('Sending REST request for ' + url);
              const xhr = new XMLHttpRequest();
              xhr.onreadystatechange = () => {
                  if (callback && xhr.readyState === 4) {
                      this.log_('REST Response for ' + url + ' received. status:', xhr.status, 'response:', xhr.responseText);
                      let res = null;
                      if (xhr.status >= 200 && xhr.status < 300) {
                          try {
                              res = jsonEval(xhr.responseText);
                          }
                          catch (e) {
                              warn('Failed to parse JSON response for ' +
                                  url +
                                  ': ' +
                                  xhr.responseText);
                          }
                          callback(null, res);
                      }
                      else {
                          // 401 and 404 are expected.
                          if (xhr.status !== 401 && xhr.status !== 404) {
                              warn('Got unsuccessful REST response for ' +
                                  url +
                                  ' Status: ' +
                                  xhr.status);
                          }
                          callback(xhr.status);
                      }
                      callback = null;
                  }
              };
              xhr.open('GET', url, /*asynchronous=*/ true);
              xhr.send();
          });
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const INTERRUPT_REASON = 'repo_interrupt';
  /**
   * A connection to a single data repository.
   */
  class Repo {
      /**
       * @param {!RepoInfo} repoInfo_
       * @param {boolean} forceRestClient
       * @param {!FirebaseApp} app
       */
      constructor(repoInfo_, forceRestClient, app) {
          this.repoInfo_ = repoInfo_;
          this.app = app;
          this.dataUpdateCount = 0;
          this.statsListener_ = null;
          this.eventQueue_ = new EventQueue();
          this.nextWriteId_ = 1;
          this.interceptServerDataCallback_ = null;
          // A list of data pieces and paths to be set when this client disconnects.
          this.onDisconnect_ = new SparseSnapshotTree();
          /**
           * TODO: This should be @private but it's used by test_access.js and internal.js
           * @type {?PersistentConnection}
           */
          this.persistentConnection_ = null;
          /** @type {!AuthTokenProvider} */
          const authTokenProvider = new AuthTokenProvider(app);
          this.stats_ = StatsManager.getCollection(repoInfo_);
          if (forceRestClient || beingCrawled()) {
              this.server_ = new ReadonlyRestClient(this.repoInfo_, this.onDataUpdate_.bind(this), authTokenProvider);
              // Minor hack: Fire onConnect immediately, since there's no actual connection.
              setTimeout(this.onConnectStatus_.bind(this, true), 0);
          }
          else {
              const authOverride = app.options['databaseAuthVariableOverride'];
              // Validate authOverride
              if (typeof authOverride !== 'undefined' && authOverride !== null) {
                  if (typeof authOverride !== 'object') {
                      throw new Error('Only objects are supported for option databaseAuthVariableOverride');
                  }
                  try {
                      stringify(authOverride);
                  }
                  catch (e) {
                      throw new Error('Invalid authOverride provided: ' + e);
                  }
              }
              this.persistentConnection_ = new PersistentConnection(this.repoInfo_, this.onDataUpdate_.bind(this), this.onConnectStatus_.bind(this), this.onServerInfoUpdate_.bind(this), authTokenProvider, authOverride);
              this.server_ = this.persistentConnection_;
          }
          authTokenProvider.addTokenChangeListener(token => {
              this.server_.refreshAuthToken(token);
          });
          // In the case of multiple Repos for the same repoInfo (i.e. there are multiple Firebase.Contexts being used),
          // we only want to create one StatsReporter.  As such, we'll report stats over the first Repo created.
          this.statsReporter_ = StatsManager.getOrCreateReporter(repoInfo_, () => new StatsReporter(this.stats_, this.server_));
          this.transactions_init_();
          // Used for .info.
          this.infoData_ = new SnapshotHolder();
          this.infoSyncTree_ = new SyncTree({
              startListening: (query, tag, currentHashFn, onComplete) => {
                  let infoEvents = [];
                  const node = this.infoData_.getNode(query.path);
                  // This is possibly a hack, but we have different semantics for .info endpoints. We don't raise null events
                  // on initial data...
                  if (!node.isEmpty()) {
                      infoEvents = this.infoSyncTree_.applyServerOverwrite(query.path, node);
                      setTimeout(() => {
                          onComplete('ok');
                      }, 0);
                  }
                  return infoEvents;
              },
              stopListening: () => { }
          });
          this.updateInfo_('connected', false);
          this.serverSyncTree_ = new SyncTree({
              startListening: (query, tag, currentHashFn, onComplete) => {
                  this.server_.listen(query, currentHashFn, tag, (status, data) => {
                      const events = onComplete(status, data);
                      this.eventQueue_.raiseEventsForChangedPath(query.path, events);
                  });
                  // No synchronous events for network-backed sync trees
                  return [];
              },
              stopListening: (query, tag) => {
                  this.server_.unlisten(query, tag);
              }
          });
      }
      /**
       * @return {string}  The URL corresponding to the root of this Firebase.
       */
      toString() {
          return ((this.repoInfo_.secure ? 'https://' : 'http://') + this.repoInfo_.host);
      }
      /**
       * @return {!string} The namespace represented by the repo.
       */
      name() {
          return this.repoInfo_.namespace;
      }
      /**
       * @return {!number} The time in milliseconds, taking the server offset into account if we have one.
       */
      serverTime() {
          const offsetNode = this.infoData_.getNode(new Path('.info/serverTimeOffset'));
          const offset = offsetNode.val() || 0;
          return new Date().getTime() + offset;
      }
      /**
       * Generate ServerValues using some variables from the repo object.
       * @return {!Object}
       */
      generateServerValues() {
          return generateWithValues({
              timestamp: this.serverTime()
          });
      }
      /**
       * Called by realtime when we get new messages from the server.
       *
       * @private
       * @param {string} pathString
       * @param {*} data
       * @param {boolean} isMerge
       * @param {?number} tag
       */
      onDataUpdate_(pathString, data, isMerge, tag) {
          // For testing.
          this.dataUpdateCount++;
          const path = new Path(pathString);
          data = this.interceptServerDataCallback_
              ? this.interceptServerDataCallback_(pathString, data)
              : data;
          let events = [];
          if (tag) {
              if (isMerge) {
                  const taggedChildren = map(data, (raw) => nodeFromJSON$1(raw));
                  events = this.serverSyncTree_.applyTaggedQueryMerge(path, taggedChildren, tag);
              }
              else {
                  const taggedSnap = nodeFromJSON$1(data);
                  events = this.serverSyncTree_.applyTaggedQueryOverwrite(path, taggedSnap, tag);
              }
          }
          else if (isMerge) {
              const changedChildren = map(data, (raw) => nodeFromJSON$1(raw));
              events = this.serverSyncTree_.applyServerMerge(path, changedChildren);
          }
          else {
              const snap = nodeFromJSON$1(data);
              events = this.serverSyncTree_.applyServerOverwrite(path, snap);
          }
          let affectedPath = path;
          if (events.length > 0) {
              // Since we have a listener outstanding for each transaction, receiving any events
              // is a proxy for some change having occurred.
              affectedPath = this.rerunTransactions_(path);
          }
          this.eventQueue_.raiseEventsForChangedPath(affectedPath, events);
      }
      /**
       * TODO: This should be @private but it's used by test_access.js and internal.js
       * @param {?function(!string, *):*} callback
       * @private
       */
      interceptServerData_(callback) {
          this.interceptServerDataCallback_ = callback;
      }
      /**
       * @param {!boolean} connectStatus
       * @private
       */
      onConnectStatus_(connectStatus) {
          this.updateInfo_('connected', connectStatus);
          if (connectStatus === false) {
              this.runOnDisconnectEvents_();
          }
      }
      /**
       * @param {!Object} updates
       * @private
       */
      onServerInfoUpdate_(updates) {
          each(updates, (value, key) => {
              this.updateInfo_(key, value);
          });
      }
      /**
       *
       * @param {!string} pathString
       * @param {*} value
       * @private
       */
      updateInfo_(pathString, value) {
          const path = new Path('/.info/' + pathString);
          const newNode = nodeFromJSON$1(value);
          this.infoData_.updateSnapshot(path, newNode);
          const events = this.infoSyncTree_.applyServerOverwrite(path, newNode);
          this.eventQueue_.raiseEventsForChangedPath(path, events);
      }
      /**
       * @return {!number}
       * @private
       */
      getNextWriteId_() {
          return this.nextWriteId_++;
      }
      /**
       * @param {!Path} path
       * @param {*} newVal
       * @param {number|string|null} newPriority
       * @param {?function(?Error, *=)} onComplete
       */
      setWithPriority(path, newVal, newPriority, onComplete) {
          this.log_('set', {
              path: path.toString(),
              value: newVal,
              priority: newPriority
          });
          // TODO: Optimize this behavior to either (a) store flag to skip resolving where possible and / or
          // (b) store unresolved paths on JSON parse
          const serverValues = this.generateServerValues();
          const newNodeUnresolved = nodeFromJSON$1(newVal, newPriority);
          const newNode = resolveDeferredValueSnapshot(newNodeUnresolved, serverValues);
          const writeId = this.getNextWriteId_();
          const events = this.serverSyncTree_.applyUserOverwrite(path, newNode, writeId, true);
          this.eventQueue_.queueEvents(events);
          this.server_.put(path.toString(), newNodeUnresolved.val(/*export=*/ true), (status, errorReason) => {
              const success = status === 'ok';
              if (!success) {
                  warn('set at ' + path + ' failed: ' + status);
              }
              const clearEvents = this.serverSyncTree_.ackUserWrite(writeId, !success);
              this.eventQueue_.raiseEventsForChangedPath(path, clearEvents);
              this.callOnCompleteCallback(onComplete, status, errorReason);
          });
          const affectedPath = this.abortTransactions_(path);
          this.rerunTransactions_(affectedPath);
          // We queued the events above, so just flush the queue here
          this.eventQueue_.raiseEventsForChangedPath(affectedPath, []);
      }
      /**
       * @param {!Path} path
       * @param {!Object} childrenToMerge
       * @param {?function(?Error, *=)} onComplete
       */
      update(path, childrenToMerge, onComplete) {
          this.log_('update', { path: path.toString(), value: childrenToMerge });
          // Start with our existing data and merge each child into it.
          let empty = true;
          const serverValues = this.generateServerValues();
          const changedChildren = {};
          forEach(childrenToMerge, (changedKey, changedValue) => {
              empty = false;
              const newNodeUnresolved = nodeFromJSON$1(changedValue);
              changedChildren[changedKey] = resolveDeferredValueSnapshot(newNodeUnresolved, serverValues);
          });
          if (!empty) {
              const writeId = this.getNextWriteId_();
              const events = this.serverSyncTree_.applyUserMerge(path, changedChildren, writeId);
              this.eventQueue_.queueEvents(events);
              this.server_.merge(path.toString(), childrenToMerge, (status, errorReason) => {
                  const success = status === 'ok';
                  if (!success) {
                      warn('update at ' + path + ' failed: ' + status);
                  }
                  const clearEvents = this.serverSyncTree_.ackUserWrite(writeId, !success);
                  const affectedPath = clearEvents.length > 0 ? this.rerunTransactions_(path) : path;
                  this.eventQueue_.raiseEventsForChangedPath(affectedPath, clearEvents);
                  this.callOnCompleteCallback(onComplete, status, errorReason);
              });
              forEach(childrenToMerge, (changedPath) => {
                  const affectedPath = this.abortTransactions_(path.child(changedPath));
                  this.rerunTransactions_(affectedPath);
              });
              // We queued the events above, so just flush the queue here
              this.eventQueue_.raiseEventsForChangedPath(path, []);
          }
          else {
              log("update() called with empty data.  Don't do anything.");
              this.callOnCompleteCallback(onComplete, 'ok');
          }
      }
      /**
       * Applies all of the changes stored up in the onDisconnect_ tree.
       * @private
       */
      runOnDisconnectEvents_() {
          this.log_('onDisconnectEvents');
          const serverValues = this.generateServerValues();
          const resolvedOnDisconnectTree = resolveDeferredValueTree(this.onDisconnect_, serverValues);
          let events = [];
          resolvedOnDisconnectTree.forEachTree(Path.Empty, (path, snap) => {
              events = events.concat(this.serverSyncTree_.applyServerOverwrite(path, snap));
              const affectedPath = this.abortTransactions_(path);
              this.rerunTransactions_(affectedPath);
          });
          this.onDisconnect_ = new SparseSnapshotTree();
          this.eventQueue_.raiseEventsForChangedPath(Path.Empty, events);
      }
      /**
       * @param {!Path} path
       * @param {?function(?Error, *=)} onComplete
       */
      onDisconnectCancel(path, onComplete) {
          this.server_.onDisconnectCancel(path.toString(), (status, errorReason) => {
              if (status === 'ok') {
                  this.onDisconnect_.forget(path);
              }
              this.callOnCompleteCallback(onComplete, status, errorReason);
          });
      }
      /**
       * @param {!Path} path
       * @param {*} value
       * @param {?function(?Error, *=)} onComplete
       */
      onDisconnectSet(path, value, onComplete) {
          const newNode = nodeFromJSON$1(value);
          this.server_.onDisconnectPut(path.toString(), newNode.val(/*export=*/ true), (status, errorReason) => {
              if (status === 'ok') {
                  this.onDisconnect_.remember(path, newNode);
              }
              this.callOnCompleteCallback(onComplete, status, errorReason);
          });
      }
      /**
       * @param {!Path} path
       * @param {*} value
       * @param {*} priority
       * @param {?function(?Error, *=)} onComplete
       */
      onDisconnectSetWithPriority(path, value, priority, onComplete) {
          const newNode = nodeFromJSON$1(value, priority);
          this.server_.onDisconnectPut(path.toString(), newNode.val(/*export=*/ true), (status, errorReason) => {
              if (status === 'ok') {
                  this.onDisconnect_.remember(path, newNode);
              }
              this.callOnCompleteCallback(onComplete, status, errorReason);
          });
      }
      /**
       * @param {!Path} path
       * @param {*} childrenToMerge
       * @param {?function(?Error, *=)} onComplete
       */
      onDisconnectUpdate(path, childrenToMerge, onComplete) {
          if (isEmpty(childrenToMerge)) {
              log("onDisconnect().update() called with empty data.  Don't do anything.");
              this.callOnCompleteCallback(onComplete, 'ok');
              return;
          }
          this.server_.onDisconnectMerge(path.toString(), childrenToMerge, (status, errorReason) => {
              if (status === 'ok') {
                  forEach(childrenToMerge, (childName, childNode) => {
                      const newChildNode = nodeFromJSON$1(childNode);
                      this.onDisconnect_.remember(path.child(childName), newChildNode);
                  });
              }
              this.callOnCompleteCallback(onComplete, status, errorReason);
          });
      }
      /**
       * @param {!Query} query
       * @param {!EventRegistration} eventRegistration
       */
      addEventCallbackForQuery(query, eventRegistration) {
          let events;
          if (query.path.getFront() === '.info') {
              events = this.infoSyncTree_.addEventRegistration(query, eventRegistration);
          }
          else {
              events = this.serverSyncTree_.addEventRegistration(query, eventRegistration);
          }
          this.eventQueue_.raiseEventsAtPath(query.path, events);
      }
      /**
       * @param {!Query} query
       * @param {?EventRegistration} eventRegistration
       */
      removeEventCallbackForQuery(query, eventRegistration) {
          // These are guaranteed not to raise events, since we're not passing in a cancelError. However, we can future-proof
          // a little bit by handling the return values anyways.
          let events;
          if (query.path.getFront() === '.info') {
              events = this.infoSyncTree_.removeEventRegistration(query, eventRegistration);
          }
          else {
              events = this.serverSyncTree_.removeEventRegistration(query, eventRegistration);
          }
          this.eventQueue_.raiseEventsAtPath(query.path, events);
      }
      interrupt() {
          if (this.persistentConnection_) {
              this.persistentConnection_.interrupt(INTERRUPT_REASON);
          }
      }
      resume() {
          if (this.persistentConnection_) {
              this.persistentConnection_.resume(INTERRUPT_REASON);
          }
      }
      stats(showDelta = false) {
          if (typeof console === 'undefined')
              return;
          let stats;
          if (showDelta) {
              if (!this.statsListener_)
                  this.statsListener_ = new StatsListener(this.stats_);
              stats = this.statsListener_.get();
          }
          else {
              stats = this.stats_.get();
          }
          const longestName = Object.keys(stats).reduce((previousValue, currentValue) => Math.max(currentValue.length, previousValue), 0);
          forEach(stats, (stat, value) => {
              // pad stat names to be the same length (plus 2 extra spaces).
              for (let i = stat.length; i < longestName + 2; i++)
                  stat += ' ';
              console.log(stat + value);
          });
      }
      statsIncrementCounter(metric) {
          this.stats_.incrementCounter(metric);
          this.statsReporter_.includeStat(metric);
      }
      /**
       * @param {...*} var_args
       * @private
       */
      log_(...var_args) {
          let prefix = '';
          if (this.persistentConnection_) {
              prefix = this.persistentConnection_.id + ':';
          }
          log(prefix, ...var_args);
      }
      /**
       * @param {?function(?Error, *=)} callback
       * @param {!string} status
       * @param {?string=} errorReason
       */
      callOnCompleteCallback(callback, status, errorReason) {
          if (callback) {
              exceptionGuard(function () {
                  if (status == 'ok') {
                      callback(null);
                  }
                  else {
                      const code = (status || 'error').toUpperCase();
                      let message = code;
                      if (errorReason)
                          message += ': ' + errorReason;
                      const error = new Error(message);
                      error.code = code;
                      callback(error);
                  }
              });
          }
      }
      get database() {
          return this.__database || (this.__database = new Database(this));
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Filters nodes by range and uses an IndexFilter to track any changes after filtering the node
   *
   * @constructor
   * @implements {NodeFilter}
   */
  class RangedFilter {
      /**
       * @param {!QueryParams} params
       */
      constructor(params) {
          this.indexedFilter_ = new IndexedFilter(params.getIndex());
          this.index_ = params.getIndex();
          this.startPost_ = RangedFilter.getStartPost_(params);
          this.endPost_ = RangedFilter.getEndPost_(params);
      }
      /**
       * @return {!NamedNode}
       */
      getStartPost() {
          return this.startPost_;
      }
      /**
       * @return {!NamedNode}
       */
      getEndPost() {
          return this.endPost_;
      }
      /**
       * @param {!NamedNode} node
       * @return {boolean}
       */
      matches(node) {
          return (this.index_.compare(this.getStartPost(), node) <= 0 &&
              this.index_.compare(node, this.getEndPost()) <= 0);
      }
      /**
       * @inheritDoc
       */
      updateChild(snap, key, newChild, affectedPath, source, optChangeAccumulator) {
          if (!this.matches(new NamedNode(key, newChild))) {
              newChild = ChildrenNode.EMPTY_NODE;
          }
          return this.indexedFilter_.updateChild(snap, key, newChild, affectedPath, source, optChangeAccumulator);
      }
      /**
       * @inheritDoc
       */
      updateFullNode(oldSnap, newSnap, optChangeAccumulator) {
          if (newSnap.isLeafNode()) {
              // Make sure we have a children node with the correct index, not a leaf node;
              newSnap = ChildrenNode.EMPTY_NODE;
          }
          let filtered = newSnap.withIndex(this.index_);
          // Don't support priorities on queries
          filtered = filtered.updatePriority(ChildrenNode.EMPTY_NODE);
          const self = this;
          newSnap.forEachChild(PRIORITY_INDEX, function (key, childNode) {
              if (!self.matches(new NamedNode(key, childNode))) {
                  filtered = filtered.updateImmediateChild(key, ChildrenNode.EMPTY_NODE);
              }
          });
          return this.indexedFilter_.updateFullNode(oldSnap, filtered, optChangeAccumulator);
      }
      /**
       * @inheritDoc
       */
      updatePriority(oldSnap, newPriority) {
          // Don't support priorities on queries
          return oldSnap;
      }
      /**
       * @inheritDoc
       */
      filtersNodes() {
          return true;
      }
      /**
       * @inheritDoc
       */
      getIndexedFilter() {
          return this.indexedFilter_;
      }
      /**
       * @inheritDoc
       */
      getIndex() {
          return this.index_;
      }
      /**
       * @param {!QueryParams} params
       * @return {!NamedNode}
       * @private
       */
      static getStartPost_(params) {
          if (params.hasStart()) {
              const startName = params.getIndexStartName();
              return params.getIndex().makePost(params.getIndexStartValue(), startName);
          }
          else {
              return params.getIndex().minPost();
          }
      }
      /**
       * @param {!QueryParams} params
       * @return {!NamedNode}
       * @private
       */
      static getEndPost_(params) {
          if (params.hasEnd()) {
              const endName = params.getIndexEndName();
              return params.getIndex().makePost(params.getIndexEndValue(), endName);
          }
          else {
              return params.getIndex().maxPost();
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Applies a limit and a range to a node and uses RangedFilter to do the heavy lifting where possible
   *
   * @constructor
   * @implements {NodeFilter}
   */
  class LimitedFilter {
      /**
       * @param {!QueryParams} params
       */
      constructor(params) {
          this.rangedFilter_ = new RangedFilter(params);
          this.index_ = params.getIndex();
          this.limit_ = params.getLimit();
          this.reverse_ = !params.isViewFromLeft();
      }
      /**
       * @inheritDoc
       */
      updateChild(snap, key, newChild, affectedPath, source, optChangeAccumulator) {
          if (!this.rangedFilter_.matches(new NamedNode(key, newChild))) {
              newChild = ChildrenNode.EMPTY_NODE;
          }
          if (snap.getImmediateChild(key).equals(newChild)) {
              // No change
              return snap;
          }
          else if (snap.numChildren() < this.limit_) {
              return this.rangedFilter_
                  .getIndexedFilter()
                  .updateChild(snap, key, newChild, affectedPath, source, optChangeAccumulator);
          }
          else {
              return this.fullLimitUpdateChild_(snap, key, newChild, source, optChangeAccumulator);
          }
      }
      /**
       * @inheritDoc
       */
      updateFullNode(oldSnap, newSnap, optChangeAccumulator) {
          let filtered;
          if (newSnap.isLeafNode() || newSnap.isEmpty()) {
              // Make sure we have a children node with the correct index, not a leaf node;
              filtered = ChildrenNode.EMPTY_NODE.withIndex(this.index_);
          }
          else {
              if (this.limit_ * 2 < newSnap.numChildren() &&
                  newSnap.isIndexed(this.index_)) {
                  // Easier to build up a snapshot, since what we're given has more than twice the elements we want
                  filtered = ChildrenNode.EMPTY_NODE.withIndex(this.index_);
                  // anchor to the startPost, endPost, or last element as appropriate
                  let iterator;
                  if (this.reverse_) {
                      iterator = newSnap.getReverseIteratorFrom(this.rangedFilter_.getEndPost(), this.index_);
                  }
                  else {
                      iterator = newSnap.getIteratorFrom(this.rangedFilter_.getStartPost(), this.index_);
                  }
                  let count = 0;
                  while (iterator.hasNext() && count < this.limit_) {
                      const next = iterator.getNext();
                      let inRange;
                      if (this.reverse_) {
                          inRange =
                              this.index_.compare(this.rangedFilter_.getStartPost(), next) <= 0;
                      }
                      else {
                          inRange =
                              this.index_.compare(next, this.rangedFilter_.getEndPost()) <= 0;
                      }
                      if (inRange) {
                          filtered = filtered.updateImmediateChild(next.name, next.node);
                          count++;
                      }
                      else {
                          // if we have reached the end post, we cannot keep adding elemments
                          break;
                      }
                  }
              }
              else {
                  // The snap contains less than twice the limit. Faster to delete from the snap than build up a new one
                  filtered = newSnap.withIndex(this.index_);
                  // Don't support priorities on queries
                  filtered = filtered.updatePriority(ChildrenNode.EMPTY_NODE);
                  let startPost;
                  let endPost;
                  let cmp;
                  let iterator;
                  if (this.reverse_) {
                      iterator = filtered.getReverseIterator(this.index_);
                      startPost = this.rangedFilter_.getEndPost();
                      endPost = this.rangedFilter_.getStartPost();
                      const indexCompare = this.index_.getCompare();
                      cmp = (a, b) => indexCompare(b, a);
                  }
                  else {
                      iterator = filtered.getIterator(this.index_);
                      startPost = this.rangedFilter_.getStartPost();
                      endPost = this.rangedFilter_.getEndPost();
                      cmp = this.index_.getCompare();
                  }
                  let count = 0;
                  let foundStartPost = false;
                  while (iterator.hasNext()) {
                      let next = iterator.getNext();
                      if (!foundStartPost && cmp(startPost, next) <= 0) {
                          // start adding
                          foundStartPost = true;
                      }
                      let inRange = foundStartPost && count < this.limit_ && cmp(next, endPost) <= 0;
                      if (inRange) {
                          count++;
                      }
                      else {
                          filtered = filtered.updateImmediateChild(next.name, ChildrenNode.EMPTY_NODE);
                      }
                  }
              }
          }
          return this.rangedFilter_
              .getIndexedFilter()
              .updateFullNode(oldSnap, filtered, optChangeAccumulator);
      }
      /**
       * @inheritDoc
       */
      updatePriority(oldSnap, newPriority) {
          // Don't support priorities on queries
          return oldSnap;
      }
      /**
       * @inheritDoc
       */
      filtersNodes() {
          return true;
      }
      /**
       * @inheritDoc
       */
      getIndexedFilter() {
          return this.rangedFilter_.getIndexedFilter();
      }
      /**
       * @inheritDoc
       */
      getIndex() {
          return this.index_;
      }
      /**
       * @param {!Node} snap
       * @param {string} childKey
       * @param {!Node} childSnap
       * @param {!CompleteChildSource} source
       * @param {?ChildChangeAccumulator} changeAccumulator
       * @return {!Node}
       * @private
       */
      fullLimitUpdateChild_(snap, childKey, childSnap, source, changeAccumulator) {
          // TODO: rename all cache stuff etc to general snap terminology
          let cmp;
          if (this.reverse_) {
              const indexCmp = this.index_.getCompare();
              cmp = (a, b) => indexCmp(b, a);
          }
          else {
              cmp = this.index_.getCompare();
          }
          const oldEventCache = snap;
          assert(oldEventCache.numChildren() == this.limit_, '');
          const newChildNamedNode = new NamedNode(childKey, childSnap);
          const windowBoundary = this.reverse_
              ? oldEventCache.getFirstChild(this.index_)
              : oldEventCache.getLastChild(this.index_);
          const inRange = this.rangedFilter_.matches(newChildNamedNode);
          if (oldEventCache.hasChild(childKey)) {
              const oldChildSnap = oldEventCache.getImmediateChild(childKey);
              let nextChild = source.getChildAfterChild(this.index_, windowBoundary, this.reverse_);
              while (nextChild != null &&
                  (nextChild.name == childKey || oldEventCache.hasChild(nextChild.name))) {
                  // There is a weird edge case where a node is updated as part of a merge in the write tree, but hasn't
                  // been applied to the limited filter yet. Ignore this next child which will be updated later in
                  // the limited filter...
                  nextChild = source.getChildAfterChild(this.index_, nextChild, this.reverse_);
              }
              const compareNext = nextChild == null ? 1 : cmp(nextChild, newChildNamedNode);
              const remainsInWindow = inRange && !childSnap.isEmpty() && compareNext >= 0;
              if (remainsInWindow) {
                  if (changeAccumulator != null) {
                      changeAccumulator.trackChildChange(Change.childChangedChange(childKey, childSnap, oldChildSnap));
                  }
                  return oldEventCache.updateImmediateChild(childKey, childSnap);
              }
              else {
                  if (changeAccumulator != null) {
                      changeAccumulator.trackChildChange(Change.childRemovedChange(childKey, oldChildSnap));
                  }
                  const newEventCache = oldEventCache.updateImmediateChild(childKey, ChildrenNode.EMPTY_NODE);
                  const nextChildInRange = nextChild != null && this.rangedFilter_.matches(nextChild);
                  if (nextChildInRange) {
                      if (changeAccumulator != null) {
                          changeAccumulator.trackChildChange(Change.childAddedChange(nextChild.name, nextChild.node));
                      }
                      return newEventCache.updateImmediateChild(nextChild.name, nextChild.node);
                  }
                  else {
                      return newEventCache;
                  }
              }
          }
          else if (childSnap.isEmpty()) {
              // we're deleting a node, but it was not in the window, so ignore it
              return snap;
          }
          else if (inRange) {
              if (cmp(windowBoundary, newChildNamedNode) >= 0) {
                  if (changeAccumulator != null) {
                      changeAccumulator.trackChildChange(Change.childRemovedChange(windowBoundary.name, windowBoundary.node));
                      changeAccumulator.trackChildChange(Change.childAddedChange(childKey, childSnap));
                  }
                  return oldEventCache
                      .updateImmediateChild(childKey, childSnap)
                      .updateImmediateChild(windowBoundary.name, ChildrenNode.EMPTY_NODE);
              }
              else {
                  return snap;
              }
          }
          else {
              return snap;
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * This class is an immutable-from-the-public-api struct containing a set of query parameters defining a
   * range to be returned for a particular location. It is assumed that validation of parameters is done at the
   * user-facing API level, so it is not done here.
   * @constructor
   */
  class QueryParams {
      constructor() {
          this.limitSet_ = false;
          this.startSet_ = false;
          this.startNameSet_ = false;
          this.endSet_ = false;
          this.endNameSet_ = false;
          this.limit_ = 0;
          this.viewFrom_ = '';
          this.indexStartValue_ = null;
          this.indexStartName_ = '';
          this.indexEndValue_ = null;
          this.indexEndName_ = '';
          this.index_ = PRIORITY_INDEX;
      }
      /**
       * @return {boolean}
       */
      hasStart() {
          return this.startSet_;
      }
      /**
       * @return {boolean} True if it would return from left.
       */
      isViewFromLeft() {
          if (this.viewFrom_ === '') {
              // limit(), rather than limitToFirst or limitToLast was called.
              // This means that only one of startSet_ and endSet_ is true. Use them
              // to calculate which side of the view to anchor to. If neither is set,
              // anchor to the end.
              return this.startSet_;
          }
          else {
              return (this.viewFrom_ === QueryParams.WIRE_PROTOCOL_CONSTANTS_.VIEW_FROM_LEFT);
          }
      }
      /**
       * Only valid to call if hasStart() returns true
       * @return {*}
       */
      getIndexStartValue() {
          assert(this.startSet_, 'Only valid if start has been set');
          return this.indexStartValue_;
      }
      /**
       * Only valid to call if hasStart() returns true.
       * Returns the starting key name for the range defined by these query parameters
       * @return {!string}
       */
      getIndexStartName() {
          assert(this.startSet_, 'Only valid if start has been set');
          if (this.startNameSet_) {
              return this.indexStartName_;
          }
          else {
              return MIN_NAME;
          }
      }
      /**
       * @return {boolean}
       */
      hasEnd() {
          return this.endSet_;
      }
      /**
       * Only valid to call if hasEnd() returns true.
       * @return {*}
       */
      getIndexEndValue() {
          assert(this.endSet_, 'Only valid if end has been set');
          return this.indexEndValue_;
      }
      /**
       * Only valid to call if hasEnd() returns true.
       * Returns the end key name for the range defined by these query parameters
       * @return {!string}
       */
      getIndexEndName() {
          assert(this.endSet_, 'Only valid if end has been set');
          if (this.endNameSet_) {
              return this.indexEndName_;
          }
          else {
              return MAX_NAME;
          }
      }
      /**
       * @return {boolean}
       */
      hasLimit() {
          return this.limitSet_;
      }
      /**
       * @return {boolean} True if a limit has been set and it has been explicitly anchored
       */
      hasAnchoredLimit() {
          return this.limitSet_ && this.viewFrom_ !== '';
      }
      /**
       * Only valid to call if hasLimit() returns true
       * @return {!number}
       */
      getLimit() {
          assert(this.limitSet_, 'Only valid if limit has been set');
          return this.limit_;
      }
      /**
       * @return {!Index}
       */
      getIndex() {
          return this.index_;
      }
      /**
       * @return {!QueryParams}
       * @private
       */
      copy_() {
          const copy = new QueryParams();
          copy.limitSet_ = this.limitSet_;
          copy.limit_ = this.limit_;
          copy.startSet_ = this.startSet_;
          copy.indexStartValue_ = this.indexStartValue_;
          copy.startNameSet_ = this.startNameSet_;
          copy.indexStartName_ = this.indexStartName_;
          copy.endSet_ = this.endSet_;
          copy.indexEndValue_ = this.indexEndValue_;
          copy.endNameSet_ = this.endNameSet_;
          copy.indexEndName_ = this.indexEndName_;
          copy.index_ = this.index_;
          copy.viewFrom_ = this.viewFrom_;
          return copy;
      }
      /**
       * @param {!number} newLimit
       * @return {!QueryParams}
       */
      limit(newLimit) {
          const newParams = this.copy_();
          newParams.limitSet_ = true;
          newParams.limit_ = newLimit;
          newParams.viewFrom_ = '';
          return newParams;
      }
      /**
       * @param {!number} newLimit
       * @return {!QueryParams}
       */
      limitToFirst(newLimit) {
          const newParams = this.copy_();
          newParams.limitSet_ = true;
          newParams.limit_ = newLimit;
          newParams.viewFrom_ = QueryParams.WIRE_PROTOCOL_CONSTANTS_.VIEW_FROM_LEFT;
          return newParams;
      }
      /**
       * @param {!number} newLimit
       * @return {!QueryParams}
       */
      limitToLast(newLimit) {
          const newParams = this.copy_();
          newParams.limitSet_ = true;
          newParams.limit_ = newLimit;
          newParams.viewFrom_ = QueryParams.WIRE_PROTOCOL_CONSTANTS_.VIEW_FROM_RIGHT;
          return newParams;
      }
      /**
       * @param {*} indexValue
       * @param {?string=} key
       * @return {!QueryParams}
       */
      startAt(indexValue, key) {
          const newParams = this.copy_();
          newParams.startSet_ = true;
          if (indexValue === undefined) {
              indexValue = null;
          }
          newParams.indexStartValue_ = indexValue;
          if (key != null) {
              newParams.startNameSet_ = true;
              newParams.indexStartName_ = key;
          }
          else {
              newParams.startNameSet_ = false;
              newParams.indexStartName_ = '';
          }
          return newParams;
      }
      /**
       * @param {*} indexValue
       * @param {?string=} key
       * @return {!QueryParams}
       */
      endAt(indexValue, key) {
          const newParams = this.copy_();
          newParams.endSet_ = true;
          if (indexValue === undefined) {
              indexValue = null;
          }
          newParams.indexEndValue_ = indexValue;
          if (key !== undefined) {
              newParams.endNameSet_ = true;
              newParams.indexEndName_ = key;
          }
          else {
              newParams.endNameSet_ = false;
              newParams.indexEndName_ = '';
          }
          return newParams;
      }
      /**
       * @param {!Index} index
       * @return {!QueryParams}
       */
      orderBy(index) {
          const newParams = this.copy_();
          newParams.index_ = index;
          return newParams;
      }
      /**
       * @return {!Object}
       */
      getQueryObject() {
          const WIRE_PROTOCOL_CONSTANTS = QueryParams.WIRE_PROTOCOL_CONSTANTS_;
          const obj = {};
          if (this.startSet_) {
              obj[WIRE_PROTOCOL_CONSTANTS.INDEX_START_VALUE] = this.indexStartValue_;
              if (this.startNameSet_) {
                  obj[WIRE_PROTOCOL_CONSTANTS.INDEX_START_NAME] = this.indexStartName_;
              }
          }
          if (this.endSet_) {
              obj[WIRE_PROTOCOL_CONSTANTS.INDEX_END_VALUE] = this.indexEndValue_;
              if (this.endNameSet_) {
                  obj[WIRE_PROTOCOL_CONSTANTS.INDEX_END_NAME] = this.indexEndName_;
              }
          }
          if (this.limitSet_) {
              obj[WIRE_PROTOCOL_CONSTANTS.LIMIT] = this.limit_;
              let viewFrom = this.viewFrom_;
              if (viewFrom === '') {
                  if (this.isViewFromLeft()) {
                      viewFrom = WIRE_PROTOCOL_CONSTANTS.VIEW_FROM_LEFT;
                  }
                  else {
                      viewFrom = WIRE_PROTOCOL_CONSTANTS.VIEW_FROM_RIGHT;
                  }
              }
              obj[WIRE_PROTOCOL_CONSTANTS.VIEW_FROM] = viewFrom;
          }
          // For now, priority index is the default, so we only specify if it's some other index
          if (this.index_ !== PRIORITY_INDEX) {
              obj[WIRE_PROTOCOL_CONSTANTS.INDEX] = this.index_.toString();
          }
          return obj;
      }
      /**
       * @return {boolean}
       */
      loadsAllData() {
          return !(this.startSet_ || this.endSet_ || this.limitSet_);
      }
      /**
       * @return {boolean}
       */
      isDefault() {
          return this.loadsAllData() && this.index_ == PRIORITY_INDEX;
      }
      /**
       * @return {!NodeFilter}
       */
      getNodeFilter() {
          if (this.loadsAllData()) {
              return new IndexedFilter(this.getIndex());
          }
          else if (this.hasLimit()) {
              return new LimitedFilter(this);
          }
          else {
              return new RangedFilter(this);
          }
      }
      /**
       * Returns a set of REST query string parameters representing this query.
       *
       * @return {!Object.<string,*>} query string parameters
       */
      toRestQueryStringParameters() {
          const REST_CONSTANTS = QueryParams.REST_QUERY_CONSTANTS_;
          const qs = {};
          if (this.isDefault()) {
              return qs;
          }
          let orderBy;
          if (this.index_ === PRIORITY_INDEX) {
              orderBy = REST_CONSTANTS.PRIORITY_INDEX;
          }
          else if (this.index_ === VALUE_INDEX) {
              orderBy = REST_CONSTANTS.VALUE_INDEX;
          }
          else if (this.index_ === KEY_INDEX) {
              orderBy = REST_CONSTANTS.KEY_INDEX;
          }
          else {
              assert(this.index_ instanceof PathIndex, 'Unrecognized index type!');
              orderBy = this.index_.toString();
          }
          qs[REST_CONSTANTS.ORDER_BY] = stringify(orderBy);
          if (this.startSet_) {
              qs[REST_CONSTANTS.START_AT] = stringify(this.indexStartValue_);
              if (this.startNameSet_) {
                  qs[REST_CONSTANTS.START_AT] += ',' + stringify(this.indexStartName_);
              }
          }
          if (this.endSet_) {
              qs[REST_CONSTANTS.END_AT] = stringify(this.indexEndValue_);
              if (this.endNameSet_) {
                  qs[REST_CONSTANTS.END_AT] += ',' + stringify(this.indexEndName_);
              }
          }
          if (this.limitSet_) {
              if (this.isViewFromLeft()) {
                  qs[REST_CONSTANTS.LIMIT_TO_FIRST] = this.limit_;
              }
              else {
                  qs[REST_CONSTANTS.LIMIT_TO_LAST] = this.limit_;
              }
          }
          return qs;
      }
  }
  /**
   * Wire Protocol Constants
   * @const
   * @enum {string}
   * @private
   */
  QueryParams.WIRE_PROTOCOL_CONSTANTS_ = {
      INDEX_START_VALUE: 'sp',
      INDEX_START_NAME: 'sn',
      INDEX_END_VALUE: 'ep',
      INDEX_END_NAME: 'en',
      LIMIT: 'l',
      VIEW_FROM: 'vf',
      VIEW_FROM_LEFT: 'l',
      VIEW_FROM_RIGHT: 'r',
      INDEX: 'i'
  };
  /**
   * REST Query Constants
   * @const
   * @enum {string}
   * @private
   */
  QueryParams.REST_QUERY_CONSTANTS_ = {
      ORDER_BY: 'orderBy',
      PRIORITY_INDEX: '$priority',
      VALUE_INDEX: '$value',
      KEY_INDEX: '$key',
      START_AT: 'startAt',
      END_AT: 'endAt',
      LIMIT_TO_FIRST: 'limitToFirst',
      LIMIT_TO_LAST: 'limitToLast'
  };
  /**
   * Default, empty query parameters
   * @type {!QueryParams}
   * @const
   */
  QueryParams.DEFAULT = new QueryParams();
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  class Reference extends Query {
      /**
       * Call options:
       *   new Reference(Repo, Path) or
       *   new Reference(url: string, string|RepoManager)
       *
       * Externally - this is the firebase.database.Reference type.
       *
       * @param {!Repo} repo
       * @param {(!Path)} path
       * @extends {Query}
       */
      constructor(repo, path) {
          if (!(repo instanceof Repo)) {
              throw new Error('new Reference() no longer supported - use app.database().');
          }
          // call Query's constructor, passing in the repo and path.
          super(repo, path, QueryParams.DEFAULT, false);
      }
      /** @return {?string} */
      getKey() {
          validateArgCount('Reference.key', 0, 0, arguments.length);
          if (this.path.isEmpty())
              return null;
          else
              return this.path.getBack();
      }
      /**
       * @param {!(string|Path)} pathString
       * @return {!Reference}
       */
      child(pathString) {
          validateArgCount('Reference.child', 1, 1, arguments.length);
          if (typeof pathString === 'number') {
              pathString = String(pathString);
          }
          else if (!(pathString instanceof Path)) {
              if (this.path.getFront() === null)
                  validateRootPathString('Reference.child', 1, pathString, false);
              else
                  validatePathString('Reference.child', 1, pathString, false);
          }
          return new Reference(this.repo, this.path.child(pathString));
      }
      /** @return {?Reference} */
      getParent() {
          validateArgCount('Reference.parent', 0, 0, arguments.length);
          const parentPath = this.path.parent();
          return parentPath === null ? null : new Reference(this.repo, parentPath);
      }
      /** @return {!Reference} */
      getRoot() {
          validateArgCount('Reference.root', 0, 0, arguments.length);
          let ref = this;
          while (ref.getParent() !== null) {
              ref = ref.getParent();
          }
          return ref;
      }
      /** @return {!Database} */
      databaseProp() {
          return this.repo.database;
      }
      /**
       * @param {*} newVal
       * @param {function(?Error)=} onComplete
       * @return {!Promise}
       */
      set(newVal, onComplete) {
          validateArgCount('Reference.set', 1, 2, arguments.length);
          validateWritablePath('Reference.set', this.path);
          validateFirebaseDataArg('Reference.set', 1, newVal, this.path, false);
          validateCallback('Reference.set', 2, onComplete, true);
          const deferred = new Deferred();
          this.repo.setWithPriority(this.path, newVal, 
          /*priority=*/ null, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
      /**
       * @param {!Object} objectToMerge
       * @param {function(?Error)=} onComplete
       * @return {!Promise}
       */
      update(objectToMerge, onComplete) {
          validateArgCount('Reference.update', 1, 2, arguments.length);
          validateWritablePath('Reference.update', this.path);
          if (Array.isArray(objectToMerge)) {
              const newObjectToMerge = {};
              for (let i = 0; i < objectToMerge.length; ++i) {
                  newObjectToMerge['' + i] = objectToMerge[i];
              }
              objectToMerge = newObjectToMerge;
              warn('Passing an Array to Firebase.update() is deprecated. ' +
                  'Use set() if you want to overwrite the existing data, or ' +
                  'an Object with integer keys if you really do want to ' +
                  'only update some of the children.');
          }
          validateFirebaseMergeDataArg('Reference.update', 1, objectToMerge, this.path, false);
          validateCallback('Reference.update', 2, onComplete, true);
          const deferred = new Deferred();
          this.repo.update(this.path, objectToMerge, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
      /**
       * @param {*} newVal
       * @param {string|number|null} newPriority
       * @param {function(?Error)=} onComplete
       * @return {!Promise}
       */
      setWithPriority(newVal, newPriority, onComplete) {
          validateArgCount('Reference.setWithPriority', 2, 3, arguments.length);
          validateWritablePath('Reference.setWithPriority', this.path);
          validateFirebaseDataArg('Reference.setWithPriority', 1, newVal, this.path, false);
          validatePriority('Reference.setWithPriority', 2, newPriority, false);
          validateCallback('Reference.setWithPriority', 3, onComplete, true);
          if (this.getKey() === '.length' || this.getKey() === '.keys')
              throw 'Reference.setWithPriority failed: ' +
                  this.getKey() +
                  ' is a read-only object.';
          const deferred = new Deferred();
          this.repo.setWithPriority(this.path, newVal, newPriority, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
      /**
       * @param {function(?Error)=} onComplete
       * @return {!Promise}
       */
      remove(onComplete) {
          validateArgCount('Reference.remove', 0, 1, arguments.length);
          validateWritablePath('Reference.remove', this.path);
          validateCallback('Reference.remove', 1, onComplete, true);
          return this.set(null, onComplete);
      }
      /**
       * @param {function(*):*} transactionUpdate
       * @param {(function(?Error, boolean, ?DataSnapshot))=} onComplete
       * @param {boolean=} applyLocally
       * @return {!Promise}
       */
      transaction(transactionUpdate, onComplete, applyLocally) {
          validateArgCount('Reference.transaction', 1, 3, arguments.length);
          validateWritablePath('Reference.transaction', this.path);
          validateCallback('Reference.transaction', 1, transactionUpdate, false);
          validateCallback('Reference.transaction', 2, onComplete, true);
          // NOTE: applyLocally is an internal-only option for now.  We need to decide if we want to keep it and how
          // to expose it.
          validateBoolean('Reference.transaction', 3, applyLocally, true);
          if (this.getKey() === '.length' || this.getKey() === '.keys')
              throw 'Reference.transaction failed: ' +
                  this.getKey() +
                  ' is a read-only object.';
          if (applyLocally === undefined)
              applyLocally = true;
          const deferred = new Deferred();
          if (typeof onComplete === 'function') {
              deferred.promise.catch(() => { });
          }
          const promiseComplete = function (error, committed, snapshot) {
              if (error) {
                  deferred.reject(error);
              }
              else {
                  deferred.resolve(new TransactionResult(committed, snapshot));
              }
              if (typeof onComplete === 'function') {
                  onComplete(error, committed, snapshot);
              }
          };
          this.repo.startTransaction(this.path, transactionUpdate, promiseComplete, applyLocally);
          return deferred.promise;
      }
      /**
       * @param {string|number|null} priority
       * @param {function(?Error)=} onComplete
       * @return {!Promise}
       */
      setPriority(priority, onComplete) {
          validateArgCount('Reference.setPriority', 1, 2, arguments.length);
          validateWritablePath('Reference.setPriority', this.path);
          validatePriority('Reference.setPriority', 1, priority, false);
          validateCallback('Reference.setPriority', 2, onComplete, true);
          const deferred = new Deferred();
          this.repo.setWithPriority(this.path.child('.priority'), priority, null, deferred.wrapCallback(onComplete));
          return deferred.promise;
      }
      /**
       * @param {*=} value
       * @param {function(?Error)=} onComplete
       * @return {!Reference}
       */
      push(value, onComplete) {
          validateArgCount('Reference.push', 0, 2, arguments.length);
          validateWritablePath('Reference.push', this.path);
          validateFirebaseDataArg('Reference.push', 1, value, this.path, true);
          validateCallback('Reference.push', 2, onComplete, true);
          const now = this.repo.serverTime();
          const name = nextPushId(now);
          // push() returns a ThennableReference whose promise is fulfilled with a regular Reference.
          // We use child() to create handles to two different references. The first is turned into a
          // ThennableReference below by adding then() and catch() methods and is used as the
          // return value of push(). The second remains a regular Reference and is used as the fulfilled
          // value of the first ThennableReference.
          const thennablePushRef = this.child(name);
          const pushRef = this.child(name);
          let promise;
          if (value != null) {
              promise = thennablePushRef.set(value, onComplete).then(() => pushRef);
          }
          else {
              promise = Promise.resolve(pushRef);
          }
          thennablePushRef.then = promise.then.bind(promise);
          thennablePushRef.catch = promise.then.bind(promise, undefined);
          if (typeof onComplete === 'function') {
              promise.catch(() => { });
          }
          return thennablePushRef;
      }
      /**
       * @return {!OnDisconnect}
       */
      onDisconnect() {
          validateWritablePath('Reference.onDisconnect', this.path);
          return new OnDisconnect(this.repo, this.path);
      }
      get database() {
          return this.databaseProp();
      }
      get key() {
          return this.getKey();
      }
      get parent() {
          return this.getParent();
      }
      get root() {
          return this.getRoot();
      }
  }
  /**
   * Define reference constructor in various modules
   *
   * We are doing this here to avoid several circular
   * dependency issues
   */
  Query.__referenceConstructor = Reference;
  SyncPoint.__referenceConstructor = Reference;
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Node in a Tree.
   */
  class TreeNode {
      constructor() {
          // TODO: Consider making accessors that create children and value lazily or
          // separate Internal / Leaf 'types'.
          this.children = {};
          this.childCount = 0;
          this.value = null;
      }
  }
  /**
   * A light-weight tree, traversable by path.  Nodes can have both values and children.
   * Nodes are not enumerated (by forEachChild) unless they have a value or non-empty
   * children.
   */
  class Tree {
      /**
       * @template T
       * @param {string=} name_ Optional name of the node.
       * @param {Tree=} parent_ Optional parent node.
       * @param {TreeNode=} node_ Optional node to wrap.
       */
      constructor(name_ = '', parent_ = null, node_ = new TreeNode()) {
          this.name_ = name_;
          this.parent_ = parent_;
          this.node_ = node_;
      }
      /**
       * Returns a sub-Tree for the given path.
       *
       * @param {!(string|Path)} pathObj Path to look up.
       * @return {!Tree.<T>} Tree for path.
       */
      subTree(pathObj) {
          // TODO: Require pathObj to be Path?
          let path = pathObj instanceof Path ? pathObj : new Path(pathObj);
          let child = this, next;
          while ((next = path.getFront()) !== null) {
              const childNode = safeGet(child.node_.children, next) || new TreeNode();
              child = new Tree(next, child, childNode);
              path = path.popFront();
          }
          return child;
      }
      /**
       * Returns the data associated with this tree node.
       *
       * @return {?T} The data or null if no data exists.
       */
      getValue() {
          return this.node_.value;
      }
      /**
       * Sets data to this tree node.
       *
       * @param {!T} value Value to set.
       */
      setValue(value) {
          assert(typeof value !== 'undefined', 'Cannot set value to undefined');
          this.node_.value = value;
          this.updateParents_();
      }
      /**
       * Clears the contents of the tree node (its value and all children).
       */
      clear() {
          this.node_.value = null;
          this.node_.children = {};
          this.node_.childCount = 0;
          this.updateParents_();
      }
      /**
       * @return {boolean} Whether the tree has any children.
       */
      hasChildren() {
          return this.node_.childCount > 0;
      }
      /**
       * @return {boolean} Whether the tree is empty (no value or children).
       */
      isEmpty() {
          return this.getValue() === null && !this.hasChildren();
      }
      /**
       * Calls action for each child of this tree node.
       *
       * @param {function(!Tree.<T>)} action Action to be called for each child.
       */
      forEachChild(action) {
          forEach(this.node_.children, (child, childTree) => {
              action(new Tree(child, this, childTree));
          });
      }
      /**
       * Does a depth-first traversal of this node's descendants, calling action for each one.
       *
       * @param {function(!Tree.<T>)} action Action to be called for each child.
       * @param {boolean=} includeSelf Whether to call action on this node as well. Defaults to
       *   false.
       * @param {boolean=} childrenFirst Whether to call action on children before calling it on
       *   parent.
       */
      forEachDescendant(action, includeSelf, childrenFirst) {
          if (includeSelf && !childrenFirst)
              action(this);
          this.forEachChild(function (child) {
              child.forEachDescendant(action, /*includeSelf=*/ true, childrenFirst);
          });
          if (includeSelf && childrenFirst)
              action(this);
      }
      /**
       * Calls action on each ancestor node.
       *
       * @param {function(!Tree.<T>)} action Action to be called on each parent; return
       *   true to abort.
       * @param {boolean=} includeSelf Whether to call action on this node as well.
       * @return {boolean} true if the action callback returned true.
       */
      forEachAncestor(action, includeSelf) {
          let node = includeSelf ? this : this.parent();
          while (node !== null) {
              if (action(node)) {
                  return true;
              }
              node = node.parent();
          }
          return false;
      }
      /**
       * Does a depth-first traversal of this node's descendants.  When a descendant with a value
       * is found, action is called on it and traversal does not continue inside the node.
       * Action is *not* called on this node.
       *
       * @param {function(!Tree.<T>)} action Action to be called for each child.
       */
      forEachImmediateDescendantWithValue(action) {
          this.forEachChild(function (child) {
              if (child.getValue() !== null)
                  action(child);
              else
                  child.forEachImmediateDescendantWithValue(action);
          });
      }
      /**
       * @return {!Path} The path of this tree node, as a Path.
       */
      path() {
          return new Path(this.parent_ === null
              ? this.name_
              : this.parent_.path() + '/' + this.name_);
      }
      /**
       * @return {string} The name of the tree node.
       */
      name() {
          return this.name_;
      }
      /**
       * @return {?Tree} The parent tree node, or null if this is the root of the tree.
       */
      parent() {
          return this.parent_;
      }
      /**
       * Adds or removes this child from its parent based on whether it's empty or not.
       *
       * @private
       */
      updateParents_() {
          if (this.parent_ !== null)
              this.parent_.updateChild_(this.name_, this);
      }
      /**
       * Adds or removes the passed child to this tree node, depending on whether it's empty.
       *
       * @param {string} childName The name of the child to update.
       * @param {!Tree.<T>} child The child to update.
       * @private
       */
      updateChild_(childName, child) {
          const childEmpty = child.isEmpty();
          const childExists = contains(this.node_.children, childName);
          if (childEmpty && childExists) {
              delete this.node_.children[childName];
              this.node_.childCount--;
              this.updateParents_();
          }
          else if (!childEmpty && !childExists) {
              this.node_.children[childName] = child.node_;
              this.node_.childCount++;
              this.updateParents_();
          }
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  // TODO: This is pretty messy.  Ideally, a lot of this would move into FirebaseData, or a transaction-specific
  // component used by FirebaseData, but it has ties to user callbacks (transaction update and onComplete) as well
  // as the realtime connection (to send transactions to the server).  So that all needs to be decoupled first.
  // For now it's part of Repo, but in its own file.
  /**
   * @enum {number}
   */
  var TransactionStatus;
  (function (TransactionStatus) {
      // We've run the transaction and updated transactionResultData_ with the result, but it isn't currently sent to the
      // server. A transaction will go from RUN -> SENT -> RUN if it comes back from the server as rejected due to
      // mismatched hash.
      TransactionStatus[TransactionStatus["RUN"] = 0] = "RUN";
      // We've run the transaction and sent it to the server and it's currently outstanding (hasn't come back as accepted
      // or rejected yet).
      TransactionStatus[TransactionStatus["SENT"] = 1] = "SENT";
      // Temporary state used to mark completed transactions (whether successful or aborted).  The transaction will be
      // removed when we get a chance to prune completed ones.
      TransactionStatus[TransactionStatus["COMPLETED"] = 2] = "COMPLETED";
      // Used when an already-sent transaction needs to be aborted (e.g. due to a conflicting set() call that was made).
      // If it comes back as unsuccessful, we'll abort it.
      TransactionStatus[TransactionStatus["SENT_NEEDS_ABORT"] = 3] = "SENT_NEEDS_ABORT";
      // Temporary state used to mark transactions that need to be aborted.
      TransactionStatus[TransactionStatus["NEEDS_ABORT"] = 4] = "NEEDS_ABORT";
  })(TransactionStatus || (TransactionStatus = {}));
  /**
   * If a transaction does not succeed after 25 retries, we abort it.  Among other things this ensure that if there's
   * ever a bug causing a mismatch between client / server hashes for some data, we won't retry indefinitely.
   * @type {number}
   * @const
   * @private
   */
  Repo.MAX_TRANSACTION_RETRIES_ = 25;
  /**
   * Setup the transaction data structures
   * @private
   */
  Repo.prototype.transactions_init_ = function () {
      /**
       * Stores queues of outstanding transactions for Firebase locations.
       *
       * @type {!Tree.<Array.<!Transaction>>}
       * @private
       */
      this.transactionQueueTree_ = new Tree();
  };
  /**
   * Creates a new transaction, adds it to the transactions we're tracking, and sends it to the server if possible.
   *
   * @param {!Path} path Path at which to do transaction.
   * @param {function(*):*} transactionUpdate Update callback.
   * @param {?function(?Error, boolean, ?DataSnapshot)} onComplete Completion callback.
   * @param {boolean} applyLocally Whether or not to make intermediate results visible
   */
  Repo.prototype.startTransaction = function (path, transactionUpdate, onComplete, applyLocally) {
      this.log_('transaction on ' + path);
      // Add a watch to make sure we get server updates.
      const valueCallback = function () { };
      const watchRef = new Reference(this, path);
      watchRef.on('value', valueCallback);
      const unwatcher = function () {
          watchRef.off('value', valueCallback);
      };
      // Initialize transaction.
      const transaction = {
          path,
          update: transactionUpdate,
          onComplete,
          // One of TransactionStatus enums.
          status: null,
          // Used when combining transactions at different locations to figure out which one goes first.
          order: LUIDGenerator(),
          // Whether to raise local events for this transaction.
          applyLocally: applyLocally,
          // Count of how many times we've retried the transaction.
          retryCount: 0,
          // Function to call to clean up our .on() listener.
          unwatcher,
          // Stores why a transaction was aborted.
          abortReason: null,
          currentWriteId: null,
          currentInputSnapshot: null,
          currentOutputSnapshotRaw: null,
          currentOutputSnapshotResolved: null
      };
      // Run transaction initially.
      const currentState = this.getLatestState_(path);
      transaction.currentInputSnapshot = currentState;
      const newVal = transaction.update(currentState.val());
      if (newVal === undefined) {
          // Abort transaction.
          transaction.unwatcher();
          transaction.currentOutputSnapshotRaw = null;
          transaction.currentOutputSnapshotResolved = null;
          if (transaction.onComplete) {
              // We just set the input snapshot, so this cast should be safe
              const snapshot = new DataSnapshot(transaction.currentInputSnapshot, new Reference(this, transaction.path), PRIORITY_INDEX);
              transaction.onComplete(null, false, snapshot);
          }
      }
      else {
          validateFirebaseData('transaction failed: Data returned ', newVal, transaction.path);
          // Mark as run and add to our queue.
          transaction.status = TransactionStatus.RUN;
          const queueNode = this.transactionQueueTree_.subTree(path);
          const nodeQueue = queueNode.getValue() || [];
          nodeQueue.push(transaction);
          queueNode.setValue(nodeQueue);
          // Update visibleData and raise events
          // Note: We intentionally raise events after updating all of our transaction state, since the user could
          // start new transactions from the event callbacks.
          let priorityForNode;
          if (typeof newVal === 'object' &&
              newVal !== null &&
              contains(newVal, '.priority')) {
              priorityForNode = safeGet(newVal, '.priority');
              assert(isValidPriority(priorityForNode), 'Invalid priority returned by transaction. ' +
                  'Priority must be a valid string, finite number, server value, or null.');
          }
          else {
              const currentNode = this.serverSyncTree_.calcCompleteEventCache(path) ||
                  ChildrenNode.EMPTY_NODE;
              priorityForNode = currentNode.getPriority().val();
          }
          priorityForNode /** @type {null|number|string} */ = priorityForNode;
          const serverValues = this.generateServerValues();
          const newNodeUnresolved = nodeFromJSON$1(newVal, priorityForNode);
          const newNode = resolveDeferredValueSnapshot(newNodeUnresolved, serverValues);
          transaction.currentOutputSnapshotRaw = newNodeUnresolved;
          transaction.currentOutputSnapshotResolved = newNode;
          transaction.currentWriteId = this.getNextWriteId_();
          const events = this.serverSyncTree_.applyUserOverwrite(path, newNode, transaction.currentWriteId, transaction.applyLocally);
          this.eventQueue_.raiseEventsForChangedPath(path, events);
          this.sendReadyTransactions_();
      }
  };
  /**
   * @param {!Path} path
   * @param {Array.<number>=} excludeSets A specific set to exclude
   * @return {Node}
   * @private
   */
  Repo.prototype.getLatestState_ = function (path, excludeSets) {
      return (this.serverSyncTree_.calcCompleteEventCache(path, excludeSets) ||
          ChildrenNode.EMPTY_NODE);
  };
  /**
   * Sends any already-run transactions that aren't waiting for outstanding transactions to
   * complete.
   *
   * Externally it's called with no arguments, but it calls itself recursively with a particular
   * transactionQueueTree node to recurse through the tree.
   *
   * @param {Tree.<Array.<Transaction>>=} node  transactionQueueTree node to start at.
   * @private
   */
  Repo.prototype.sendReadyTransactions_ = function (node = this.transactionQueueTree_) {
      // Before recursing, make sure any completed transactions are removed.
      if (!node) {
          this.pruneCompletedTransactionsBelowNode_(node);
      }
      if (node.getValue() !== null) {
          const queue = this.buildTransactionQueue_(node);
          assert(queue.length > 0, 'Sending zero length transaction queue');
          const allRun = queue.every((transaction) => transaction.status === TransactionStatus.RUN);
          // If they're all run (and not sent), we can send them.  Else, we must wait.
          if (allRun) {
              this.sendTransactionQueue_(node.path(), queue);
          }
      }
      else if (node.hasChildren()) {
          node.forEachChild(childNode => {
              this.sendReadyTransactions_(childNode);
          });
      }
  };
  /**
   * Given a list of run transactions, send them to the server and then handle the result (success or failure).
   *
   * @param {!Path} path The location of the queue.
   * @param {!Array.<Transaction>} queue Queue of transactions under the specified location.
   * @private
   */
  Repo.prototype.sendTransactionQueue_ = function (path, queue) {
      // Mark transactions as sent and increment retry count!
      const setsToIgnore = queue.map(function (txn) {
          return txn.currentWriteId;
      });
      const latestState = this.getLatestState_(path, setsToIgnore);
      let snapToSend = latestState;
      const latestHash = latestState.hash();
      for (let i = 0; i < queue.length; i++) {
          const txn = queue[i];
          assert(txn.status === TransactionStatus.RUN, 'tryToSendTransactionQueue_: items in queue should all be run.');
          txn.status = TransactionStatus.SENT;
          txn.retryCount++;
          const relativePath = Path.relativePath(path, txn.path);
          // If we've gotten to this point, the output snapshot must be defined.
          snapToSend = snapToSend.updateChild(relativePath /**@type {!Node} */, txn.currentOutputSnapshotRaw);
      }
      const dataToSend = snapToSend.val(true);
      const pathToSend = path;
      // Send the put.
      this.server_.put(pathToSend.toString(), dataToSend, (status) => {
          this.log_('transaction put response', {
              path: pathToSend.toString(),
              status
          });
          let events = [];
          if (status === 'ok') {
              // Queue up the callbacks and fire them after cleaning up all of our transaction state, since
              // the callback could trigger more transactions or sets.
              const callbacks = [];
              for (let i = 0; i < queue.length; i++) {
                  queue[i].status = TransactionStatus.COMPLETED;
                  events = events.concat(this.serverSyncTree_.ackUserWrite(queue[i].currentWriteId));
                  if (queue[i].onComplete) {
                      // We never unset the output snapshot, and given that this transaction is complete, it should be set
                      const node = queue[i].currentOutputSnapshotResolved;
                      const ref = new Reference(this, queue[i].path);
                      const snapshot = new DataSnapshot(node, ref, PRIORITY_INDEX);
                      callbacks.push(queue[i].onComplete.bind(null, null, true, snapshot));
                  }
                  queue[i].unwatcher();
              }
              // Now remove the completed transactions.
              this.pruneCompletedTransactionsBelowNode_(this.transactionQueueTree_.subTree(path));
              // There may be pending transactions that we can now send.
              this.sendReadyTransactions_();
              this.eventQueue_.raiseEventsForChangedPath(path, events);
              // Finally, trigger onComplete callbacks.
              for (let i = 0; i < callbacks.length; i++) {
                  exceptionGuard(callbacks[i]);
              }
          }
          else {
              // transactions are no longer sent.  Update their status appropriately.
              if (status === 'datastale') {
                  for (let i = 0; i < queue.length; i++) {
                      if (queue[i].status === TransactionStatus.SENT_NEEDS_ABORT)
                          queue[i].status = TransactionStatus.NEEDS_ABORT;
                      else
                          queue[i].status = TransactionStatus.RUN;
                  }
              }
              else {
                  warn('transaction at ' + pathToSend.toString() + ' failed: ' + status);
                  for (let i = 0; i < queue.length; i++) {
                      queue[i].status = TransactionStatus.NEEDS_ABORT;
                      queue[i].abortReason = status;
                  }
              }
              this.rerunTransactions_(path);
          }
      }, latestHash);
  };
  /**
   * Finds all transactions dependent on the data at changedPath and reruns them.
   *
   * Should be called any time cached data changes.
   *
   * Return the highest path that was affected by rerunning transactions.  This is the path at which events need to
   * be raised for.
   *
   * @param {!Path} changedPath The path in mergedData that changed.
   * @return {!Path} The rootmost path that was affected by rerunning transactions.
   * @private
   */
  Repo.prototype.rerunTransactions_ = function (changedPath) {
      const rootMostTransactionNode = this.getAncestorTransactionNode_(changedPath);
      const path = rootMostTransactionNode.path();
      const queue = this.buildTransactionQueue_(rootMostTransactionNode);
      this.rerunTransactionQueue_(queue, path);
      return path;
  };
  /**
   * Does all the work of rerunning transactions (as well as cleans up aborted transactions and whatnot).
   *
   * @param {Array.<Transaction>} queue The queue of transactions to run.
   * @param {!Path} path The path the queue is for.
   * @private
   */
  Repo.prototype.rerunTransactionQueue_ = function (queue, path) {
      if (queue.length === 0) {
          return; // Nothing to do!
      }
      // Queue up the callbacks and fire them after cleaning up all of our transaction state, since
      // the callback could trigger more transactions or sets.
      const callbacks = [];
      let events = [];
      // Ignore all of the sets we're going to re-run.
      const txnsToRerun = queue.filter(function (q) {
          return q.status === TransactionStatus.RUN;
      });
      const setsToIgnore = txnsToRerun.map(function (q) {
          return q.currentWriteId;
      });
      for (let i = 0; i < queue.length; i++) {
          const transaction = queue[i];
          const relativePath = Path.relativePath(path, transaction.path);
          let abortTransaction = false, abortReason;
          assert(relativePath !== null, 'rerunTransactionsUnderNode_: relativePath should not be null.');
          if (transaction.status === TransactionStatus.NEEDS_ABORT) {
              abortTransaction = true;
              abortReason = transaction.abortReason;
              events = events.concat(this.serverSyncTree_.ackUserWrite(transaction.currentWriteId, true));
          }
          else if (transaction.status === TransactionStatus.RUN) {
              if (transaction.retryCount >= Repo.MAX_TRANSACTION_RETRIES_) {
                  abortTransaction = true;
                  abortReason = 'maxretry';
                  events = events.concat(this.serverSyncTree_.ackUserWrite(transaction.currentWriteId, true));
              }
              else {
                  // This code reruns a transaction
                  const currentNode = this.getLatestState_(transaction.path, setsToIgnore);
                  transaction.currentInputSnapshot = currentNode;
                  const newData = queue[i].update(currentNode.val());
                  if (newData !== undefined) {
                      validateFirebaseData('transaction failed: Data returned ', newData, transaction.path);
                      let newDataNode = nodeFromJSON$1(newData);
                      const hasExplicitPriority = typeof newData === 'object' &&
                          newData != null &&
                          contains(newData, '.priority');
                      if (!hasExplicitPriority) {
                          // Keep the old priority if there wasn't a priority explicitly specified.
                          newDataNode = newDataNode.updatePriority(currentNode.getPriority());
                      }
                      const oldWriteId = transaction.currentWriteId;
                      const serverValues = this.generateServerValues();
                      const newNodeResolved = resolveDeferredValueSnapshot(newDataNode, serverValues);
                      transaction.currentOutputSnapshotRaw = newDataNode;
                      transaction.currentOutputSnapshotResolved = newNodeResolved;
                      transaction.currentWriteId = this.getNextWriteId_();
                      // Mutates setsToIgnore in place
                      setsToIgnore.splice(setsToIgnore.indexOf(oldWriteId), 1);
                      events = events.concat(this.serverSyncTree_.applyUserOverwrite(transaction.path, newNodeResolved, transaction.currentWriteId, transaction.applyLocally));
                      events = events.concat(this.serverSyncTree_.ackUserWrite(oldWriteId, true));
                  }
                  else {
                      abortTransaction = true;
                      abortReason = 'nodata';
                      events = events.concat(this.serverSyncTree_.ackUserWrite(transaction.currentWriteId, true));
                  }
              }
          }
          this.eventQueue_.raiseEventsForChangedPath(path, events);
          events = [];
          if (abortTransaction) {
              // Abort.
              queue[i].status = TransactionStatus.COMPLETED;
              // Removing a listener can trigger pruning which can muck with mergedData/visibleData (as it prunes data).
              // So defer the unwatcher until we're done.
              (function (unwatcher) {
                  setTimeout(unwatcher, Math.floor(0));
              })(queue[i].unwatcher);
              if (queue[i].onComplete) {
                  if (abortReason === 'nodata') {
                      const ref = new Reference(this, queue[i].path);
                      // We set this field immediately, so it's safe to cast to an actual snapshot
                      const lastInput /** @type {!Node} */ = queue[i].currentInputSnapshot;
                      const snapshot = new DataSnapshot(lastInput, ref, PRIORITY_INDEX);
                      callbacks.push(queue[i].onComplete.bind(null, null, false, snapshot));
                  }
                  else {
                      callbacks.push(queue[i].onComplete.bind(null, new Error(abortReason), false, null));
                  }
              }
          }
      }
      // Clean up completed transactions.
      this.pruneCompletedTransactionsBelowNode_(this.transactionQueueTree_);
      // Now fire callbacks, now that we're in a good, known state.
      for (let i = 0; i < callbacks.length; i++) {
          exceptionGuard(callbacks[i]);
      }
      // Try to send the transaction result to the server.
      this.sendReadyTransactions_();
  };
  /**
   * Returns the rootmost ancestor node of the specified path that has a pending transaction on it, or just returns
   * the node for the given path if there are no pending transactions on any ancestor.
   *
   * @param {!Path} path The location to start at.
   * @return {!Tree.<Array.<!Transaction>>} The rootmost node with a transaction.
   * @private
   */
  Repo.prototype.getAncestorTransactionNode_ = function (path) {
      let front;
      // Start at the root and walk deeper into the tree towards path until we find a node with pending transactions.
      let transactionNode = this.transactionQueueTree_;
      while ((front = path.getFront()) !== null &&
          transactionNode.getValue() === null) {
          transactionNode = transactionNode.subTree(front);
          path = path.popFront();
      }
      return transactionNode;
  };
  /**
   * Builds the queue of all transactions at or below the specified transactionNode.
   *
   * @param {!Tree.<Array.<Transaction>>} transactionNode
   * @return {Array.<Transaction>} The generated queue.
   * @private
   */
  Repo.prototype.buildTransactionQueue_ = function (transactionNode) {
      // Walk any child transaction queues and aggregate them into a single queue.
      const transactionQueue = [];
      this.aggregateTransactionQueuesForNode_(transactionNode, transactionQueue);
      // Sort them by the order the transactions were created.
      transactionQueue.sort(function (a, b) {
          return a.order - b.order;
      });
      return transactionQueue;
  };
  /**
   * @param {!Tree.<Array.<Transaction>>} node
   * @param {Array.<Transaction>} queue
   * @private
   */
  Repo.prototype.aggregateTransactionQueuesForNode_ = function (node, queue) {
      const nodeQueue = node.getValue();
      if (nodeQueue !== null) {
          for (let i = 0; i < nodeQueue.length; i++) {
              queue.push(nodeQueue[i]);
          }
      }
      node.forEachChild(child => {
          this.aggregateTransactionQueuesForNode_(child, queue);
      });
  };
  /**
   * Remove COMPLETED transactions at or below this node in the transactionQueueTree_.
   *
   * @param {!Tree.<Array.<!Transaction>>} node
   * @private
   */
  Repo.prototype.pruneCompletedTransactionsBelowNode_ = function (node) {
      const queue = node.getValue();
      if (queue) {
          let to = 0;
          for (let from = 0; from < queue.length; from++) {
              if (queue[from].status !== TransactionStatus.COMPLETED) {
                  queue[to] = queue[from];
                  to++;
              }
          }
          queue.length = to;
          node.setValue(queue.length > 0 ? queue : null);
      }
      node.forEachChild(childNode => {
          this.pruneCompletedTransactionsBelowNode_(childNode);
      });
  };
  /**
   * Aborts all transactions on ancestors or descendants of the specified path.  Called when doing a set() or update()
   * since we consider them incompatible with transactions.
   *
   * @param {!Path} path Path for which we want to abort related transactions.
   * @return {!Path}
   * @private
   */
  Repo.prototype.abortTransactions_ = function (path) {
      const affectedPath = this.getAncestorTransactionNode_(path).path();
      const transactionNode = this.transactionQueueTree_.subTree(path);
      transactionNode.forEachAncestor((node) => {
          this.abortTransactionsOnNode_(node);
      });
      this.abortTransactionsOnNode_(transactionNode);
      transactionNode.forEachDescendant((node) => {
          this.abortTransactionsOnNode_(node);
      });
      return affectedPath;
  };
  /**
   * Abort transactions stored in this transaction queue node.
   *
   * @param {!Tree.<Array.<Transaction>>} node Node to abort transactions for.
   * @private
   */
  Repo.prototype.abortTransactionsOnNode_ = function (node) {
      const queue = node.getValue();
      if (queue !== null) {
          // Queue up the callbacks and fire them after cleaning up all of our transaction state, since
          // the callback could trigger more transactions or sets.
          const callbacks = [];
          // Go through queue.  Any already-sent transactions must be marked for abort, while the unsent ones
          // can be immediately aborted and removed.
          let events = [];
          let lastSent = -1;
          for (let i = 0; i < queue.length; i++) {
              if (queue[i].status === TransactionStatus.SENT_NEEDS_ABORT) ;
              else if (queue[i].status === TransactionStatus.SENT) {
                  assert(lastSent === i - 1, 'All SENT items should be at beginning of queue.');
                  lastSent = i;
                  // Mark transaction for abort when it comes back.
                  queue[i].status = TransactionStatus.SENT_NEEDS_ABORT;
                  queue[i].abortReason = 'set';
              }
              else {
                  assert(queue[i].status === TransactionStatus.RUN, 'Unexpected transaction status in abort');
                  // We can abort it immediately.
                  queue[i].unwatcher();
                  events = events.concat(this.serverSyncTree_.ackUserWrite(queue[i].currentWriteId, true));
                  if (queue[i].onComplete) {
                      const snapshot = null;
                      callbacks.push(queue[i].onComplete.bind(null, new Error('set'), false, snapshot));
                  }
              }
          }
          if (lastSent === -1) {
              // We're not waiting for any sent transactions.  We can clear the queue.
              node.setValue(null);
          }
          else {
              // Remove the transactions we aborted.
              queue.length = lastSent + 1;
          }
          // Now fire the callbacks.
          this.eventQueue_.raiseEventsForChangedPath(node.path(), events);
          for (let i = 0; i < callbacks.length; i++) {
              exceptionGuard(callbacks[i]);
          }
      }
  };
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /** @const {string} */
  const DATABASE_URL_OPTION = 'databaseURL';
  let _staticInstance;
  /**
   * Creates and caches Repo instances.
   */
  class RepoManager {
      constructor() {
          /**
           * @private {!Object.<string, Object<string, !fb.core.Repo>>}
           */
          this.repos_ = {};
          /**
           * If true, new Repos will be created to use ReadonlyRestClient (for testing purposes).
           * @private {boolean}
           */
          this.useRestClient_ = false;
      }
      static getInstance() {
          if (!_staticInstance) {
              _staticInstance = new RepoManager();
          }
          return _staticInstance;
      }
      // TODO(koss): Remove these functions unless used in tests?
      interrupt() {
          for (const appName in this.repos_) {
              for (const dbUrl in this.repos_[appName]) {
                  this.repos_[appName][dbUrl].interrupt();
              }
          }
      }
      resume() {
          for (const appName in this.repos_) {
              for (const dbUrl in this.repos_[appName]) {
                  this.repos_[appName][dbUrl].resume();
              }
          }
      }
      /**
       * This function should only ever be called to CREATE a new database instance.
       *
       * @param {!FirebaseApp} app
       * @return {!Database}
       */
      databaseFromApp(app, url) {
          const dbUrl = url || app.options[DATABASE_URL_OPTION];
          if (dbUrl === undefined) {
              fatal("Can't determine Firebase Database URL.  Be sure to include " +
                  DATABASE_URL_OPTION +
                  ' option when calling firebase.initializeApp().');
          }
          const parsedUrl = parseRepoInfo(dbUrl);
          const repoInfo = parsedUrl.repoInfo;
          validateUrl('Invalid Firebase Database URL', 1, parsedUrl);
          if (!parsedUrl.path.isEmpty()) {
              fatal('Database URL must point to the root of a Firebase Database ' +
                  '(not including a child path).');
          }
          const repo = this.createRepo(repoInfo, app);
          return repo.database;
      }
      /**
       * Remove the repo and make sure it is disconnected.
       *
       * @param {!Repo} repo
       */
      deleteRepo(repo) {
          const appRepos = safeGet(this.repos_, repo.app.name);
          // This should never happen...
          if (!appRepos || safeGet(appRepos, repo.repoInfo_.toURLString()) !== repo) {
              fatal(`Database ${repo.app.name}(${repo.repoInfo_}) has already been deleted.`);
          }
          repo.interrupt();
          delete appRepos[repo.repoInfo_.toURLString()];
      }
      /**
       * Ensures a repo doesn't already exist and then creates one using the
       * provided app.
       *
       * @param {!RepoInfo} repoInfo The metadata about the Repo
       * @param {!FirebaseApp} app
       * @return {!Repo} The Repo object for the specified server / repoName.
       */
      createRepo(repoInfo, app) {
          let appRepos = safeGet(this.repos_, app.name);
          if (!appRepos) {
              appRepos = {};
              this.repos_[app.name] = appRepos;
          }
          let repo = safeGet(appRepos, repoInfo.toURLString());
          if (repo) {
              fatal('Database initialized multiple times. Please make sure the format of the database URL matches with each database() call.');
          }
          repo = new Repo(repoInfo, this.useRestClient_, app);
          appRepos[repoInfo.toURLString()] = repo;
          return repo;
      }
      /**
       * Forces us to use ReadonlyRestClient instead of PersistentConnection for new Repos.
       * @param {boolean} forceRestClient
       */
      forceRestClient(forceRestClient) {
          this.useRestClient_ = forceRestClient;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * Class representing a firebase database.
   * @implements {FirebaseService}
   */
  class Database {
      /**
       * The constructor should not be called by users of our public API.
       * @param {!Repo} repo_
       */
      constructor(repo_) {
          this.repo_ = repo_;
          if (!(repo_ instanceof Repo)) {
              fatal("Don't call new Database() directly - please use firebase.database().");
          }
          /** @type {Reference} */
          this.root_ = new Reference(repo_, Path.Empty);
          this.INTERNAL = new DatabaseInternals(this);
      }
      get app() {
          return this.repo_.app;
      }
      ref(path) {
          this.checkDeleted_('ref');
          validateArgCount('database.ref', 0, 1, arguments.length);
          if (path instanceof Reference) {
              return this.refFromURL(path.toString());
          }
          return path !== undefined ? this.root_.child(path) : this.root_;
      }
      /**
       * Returns a reference to the root or the path specified in url.
       * We throw a exception if the url is not in the same domain as the
       * current repo.
       * @param {string} url
       * @return {!Reference} Firebase reference.
       */
      refFromURL(url) {
          /** @const {string} */
          const apiName = 'database.refFromURL';
          this.checkDeleted_(apiName);
          validateArgCount(apiName, 1, 1, arguments.length);
          const parsedURL = parseRepoInfo(url);
          validateUrl(apiName, 1, parsedURL);
          const repoInfo = parsedURL.repoInfo;
          if (repoInfo.host !== this.repo_.repoInfo_.host) {
              fatal(apiName +
                  ': Host name does not match the current database: ' +
                  '(found ' +
                  repoInfo.host +
                  ' but expected ' +
                  this.repo_.repoInfo_.host +
                  ')');
          }
          return this.ref(parsedURL.path.toString());
      }
      /**
       * @param {string} apiName
       */
      checkDeleted_(apiName) {
          if (this.repo_ === null) {
              fatal('Cannot call ' + apiName + ' on a deleted database.');
          }
      }
      // Make individual repo go offline.
      goOffline() {
          validateArgCount('database.goOffline', 0, 0, arguments.length);
          this.checkDeleted_('goOffline');
          this.repo_.interrupt();
      }
      goOnline() {
          validateArgCount('database.goOnline', 0, 0, arguments.length);
          this.checkDeleted_('goOnline');
          this.repo_.resume();
      }
  }
  Database.ServerValue = {
      TIMESTAMP: {
          '.sv': 'timestamp'
      }
  };
  class DatabaseInternals {
      /** @param {!Database} database */
      constructor(database) {
          this.database = database;
      }
      /** @return {Promise<void>} */
      async delete() {
          this.database.checkDeleted_('delete');
          RepoManager.getInstance().deleteRepo(this.database.repo_);
          this.database.repo_ = null;
          this.database.root_ = null;
          this.database.INTERNAL = null;
          this.database = null;
      }
  }
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /**
   * INTERNAL methods for internal-use only (tests, etc.).
   *
   * Customers shouldn't use these or else should be aware that they could break at any time.
   *
   * @const
   */
  const forceLongPolling = function () {
      WebSocketConnection.forceDisallow();
      BrowserPollConnection.forceAllow();
  };
  const forceWebSockets = function () {
      BrowserPollConnection.forceDisallow();
  };
  /* Used by App Manager */
  const isWebSocketsAvailable = function () {
      return WebSocketConnection['isAvailable']();
  };
  const setSecurityDebugCallback = function (ref, callback) {
      ref.repo.persistentConnection_.securityDebugCallback_ = callback;
  };
  const stats = function (ref, showDelta) {
      ref.repo.stats(showDelta);
  };
  const statsIncrementCounter = function (ref, metric) {
      ref.repo.statsIncrementCounter(metric);
  };
  const dataUpdateCount = function (ref) {
      return ref.repo.dataUpdateCount;
  };
  const interceptServerData = function (ref, callback) {
      return ref.repo.interceptServerData_(callback);
  };
  
  var INTERNAL = /*#__PURE__*/Object.freeze({
    forceLongPolling: forceLongPolling,
    forceWebSockets: forceWebSockets,
    isWebSocketsAvailable: isWebSocketsAvailable,
    setSecurityDebugCallback: setSecurityDebugCallback,
    stats: stats,
    statsIncrementCounter: statsIncrementCounter,
    dataUpdateCount: dataUpdateCount,
    interceptServerData: interceptServerData
  });
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const DataConnection = PersistentConnection;
  /**
   * @param {!string} pathString
   * @param {function(*)} onComplete
   */
  PersistentConnection.prototype.simpleListen = function (pathString, onComplete) {
      this.sendRequest('q', { p: pathString }, onComplete);
  };
  /**
   * @param {*} data
   * @param {function(*)} onEcho
   */
  PersistentConnection.prototype.echo = function (data, onEcho) {
      this.sendRequest('echo', { d: data }, onEcho);
  };
  // RealTimeConnection properties that we use in tests.
  const RealTimeConnection = Connection;
  /**
   * @param {function(): string} newHash
   * @return {function()}
   */
  const hijackHash = function (newHash) {
      const oldPut = PersistentConnection.prototype.put;
      PersistentConnection.prototype.put = function (pathString, data, opt_onComplete, opt_hash) {
          if (opt_hash !== undefined) {
              opt_hash = newHash();
          }
          oldPut.call(this, pathString, data, opt_onComplete, opt_hash);
      };
      return function () {
          PersistentConnection.prototype.put = oldPut;
      };
  };
  /**
   * @type {function(new:RepoInfo, !string, boolean, !string, boolean): undefined}
   */
  const ConnectionTarget = RepoInfo;
  /**
   * @param {!Query} query
   * @return {!string}
   */
  const queryIdentifier = function (query) {
      return query.queryIdentifier();
  };
  /**
   * @param {!Query} firebaseRef
   * @return {!Object}
   */
  const listens = function (firebaseRef) {
      return firebaseRef.repo.persistentConnection_.listens_;
  };
  /**
   * Forces the RepoManager to create Repos that use ReadonlyRestClient instead of PersistentConnection.
   *
   * @param {boolean} forceRestClient
   */
  const forceRestClient = function (forceRestClient) {
      RepoManager.getInstance().forceRestClient(forceRestClient);
  };
  
  var TEST_ACCESS = /*#__PURE__*/Object.freeze({
    DataConnection: DataConnection,
    RealTimeConnection: RealTimeConnection,
    hijackHash: hijackHash,
    ConnectionTarget: ConnectionTarget,
    queryIdentifier: queryIdentifier,
    listens: listens,
    forceRestClient: forceRestClient
  });
  
  /**
   * @license
   * Copyright 2017 Google Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const ServerValue = Database.ServerValue;
  function registerDatabase(instance) {
      // Register the Database Service with the 'firebase' namespace.
      const namespace = instance.INTERNAL.registerService('database', (app, unused, url) => RepoManager.getInstance().databaseFromApp(app, url), 
      // firebase.database namespace properties
      {
          Reference,
          Query,
          Database,
          DataSnapshot,
          enableLogging,
          INTERNAL,
          ServerValue,
          TEST_ACCESS
      }, null, true);
      if (isNodeSdk()) {
          module.exports = namespace;
      }
  }
  registerDatabase(firebase);
  
  export { DataSnapshot, Database, OnDisconnect, Query, Reference, ServerValue, enableLogging, registerDatabase };
  //# sourceMappingURL=index.esm2017.js.map
  