text: // Copyright Joyent, Inc. and other Node contributors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a
  // copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to permit
  // persons to whom the Software is furnished to do so, subject to the
  // following conditions:
  //
  // The above copyright notice and this permission notice shall be included
  // in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  'use strict';
  
  // WARNING: THIS MODULE IS PENDING DEPRECATION.
  //
  // No new pull requests targeting this module will be accepted
  // unless they address existing, critical bugs.
  
  const util = require('util');
  const EventEmitter = require('events');
  const {
    ERR_DOMAIN_CALLBACK_NOT_AVAILABLE,
    ERR_DOMAIN_CANNOT_SET_UNCAUGHT_EXCEPTION_CAPTURE,
    ERR_UNHANDLED_ERROR
  } = require('internal/errors').codes;
  const { createHook } = require('async_hooks');
  
  // TODO(addaleax): Use a non-internal solution for this.
  const kWeak = Symbol('kWeak');
  const { WeakReference } = internalBinding('util');
  
  // Overwrite process.domain with a getter/setter that will allow for more
  // effective optimizations
  var _domain = [null];
  Object.defineProperty(process, 'domain', {
    enumerable: true,
    get: function() {
      return _domain[0];
    },
    set: function(arg) {
      return _domain[0] = arg;
    }
  });
  
  const pairing = new Map();
  const asyncHook = createHook({
    init(asyncId, type, triggerAsyncId, resource) {
      if (process.domain !== null && process.domain !== undefined) {
        // If this operation is created while in a domain, let's mark it
        pairing.set(asyncId, process.domain[kWeak]);
        resource.domain = process.domain;
      }
    },
    before(asyncId) {
      const current = pairing.get(asyncId);
      if (current !== undefined) { // enter domain for this cb
        // We will get the domain through current.get(), because the resource
        // object's .domain property makes sure it is not garbage collected.
        current.get().enter();
      }
    },
    after(asyncId) {
      const current = pairing.get(asyncId);
      if (current !== undefined) { // exit domain for this cb
        current.get().exit();
      }
    },
    destroy(asyncId) {
      pairing.delete(asyncId); // cleaning up
    }
  });
  
  // When domains are in use, they claim full ownership of the
  // uncaught exception capture callback.
  if (process.hasUncaughtExceptionCaptureCallback()) {
    throw new ERR_DOMAIN_CALLBACK_NOT_AVAILABLE();
  }
  
  // Get the stack trace at the point where `domain` was required.
  // eslint-disable-next-line no-restricted-syntax
  const domainRequireStack = new Error('require(`domain`) at this point').stack;
  
  const { setUncaughtExceptionCaptureCallback } = process;
  process.setUncaughtExceptionCaptureCallback = function(fn) {
    const err = new ERR_DOMAIN_CANNOT_SET_UNCAUGHT_EXCEPTION_CAPTURE();
    err.stack = err.stack + '\n' + '-'.repeat(40) + '\n' + domainRequireStack;
    throw err;
  };
  
  
  let sendMakeCallbackDeprecation = false;
  function emitMakeCallbackDeprecation() {
    if (!sendMakeCallbackDeprecation) {
      process.emitWarning(
        'Using a domain property in MakeCallback is deprecated. Use the ' +
        'async_context variant of MakeCallback or the AsyncResource class ' +
        'instead.', 'DeprecationWarning', 'DEP0097');
      sendMakeCallbackDeprecation = true;
    }
  }
  
  function topLevelDomainCallback(cb, ...args) {
    const domain = this.domain;
    if (exports.active && domain)
      emitMakeCallbackDeprecation();
  
    if (domain)
      domain.enter();
    const ret = Reflect.apply(cb, this, args);
    if (domain)
      domain.exit();
  
    return ret;
  }
  
  // It's possible to enter one domain while already inside
  // another one. The stack is each entered domain.
  const stack = [];
  exports._stack = stack;
  internalBinding('domain').enable(topLevelDomainCallback);
  
  function updateExceptionCapture() {
    if (stack.every((domain) => domain.listenerCount('error') === 0)) {
      setUncaughtExceptionCaptureCallback(null);
    } else {
      setUncaughtExceptionCaptureCallback(null);
      setUncaughtExceptionCaptureCallback((er) => {
        return process.domain._errorHandler(er);
      });
    }
  }
  
  
  process.on('newListener', (name, listener) => {
    if (name === 'uncaughtException' &&
        listener !== domainUncaughtExceptionClear) {
      // Make sure the first listener for `uncaughtException` always clears
      // the domain stack.
      process.removeListener(name, domainUncaughtExceptionClear);
      process.prependListener(name, domainUncaughtExceptionClear);
    }
  });
  
  process.on('removeListener', (name, listener) => {
    if (name === 'uncaughtException' &&
        listener !== domainUncaughtExceptionClear) {
      // If the domain listener would be the only remaining one, remove it.
      const listeners = process.listeners('uncaughtException');
      if (listeners.length === 1 && listeners[0] === domainUncaughtExceptionClear)
        process.removeListener(name, domainUncaughtExceptionClear);
    }
  });
  
  function domainUncaughtExceptionClear() {
    stack.length = 0;
    exports.active = process.domain = null;
    updateExceptionCapture();
  }
  
  
  class Domain extends EventEmitter {
    constructor() {
      super();
  
      this.members = [];
      this[kWeak] = new WeakReference(this);
      asyncHook.enable();
  
      this.on('removeListener', updateExceptionCapture);
      this.on('newListener', updateExceptionCapture);
    }
  }
  
  exports.Domain = Domain;
  
  exports.create = exports.createDomain = function createDomain() {
    return new Domain();
  };
  
  // The active domain is always the one that we're currently in.
  exports.active = null;
  Domain.prototype.members = undefined;
  
  // Called by process._fatalException in case an error was thrown.
  Domain.prototype._errorHandler = function(er) {
    var caught = false;
  
    if (!util.isPrimitive(er)) {
      er.domain = this;
      er.domainThrown = true;
    }
  
    // The top-level domain-handler is handled separately.
    //
    // The reason is that if V8 was passed a command line option
    // asking it to abort on an uncaught exception (currently
    // "--abort-on-uncaught-exception"), we want an uncaught exception
    // in the top-level domain error handler to make the
    // process abort. Using try/catch here would always make V8 think
    // that these exceptions are caught, and thus would prevent it from
    // aborting in these cases.
    if (stack.length === 1) {
      // If there's no error handler, do not emit an 'error' event
      // as this would throw an error, make the process exit, and thus
      // prevent the process 'uncaughtException' event from being emitted
      // if a listener is set.
      if (EventEmitter.listenerCount(this, 'error') > 0) {
        // Clear the uncaughtExceptionCaptureCallback so that we know that, even
        // if technically the top-level domain is still active, it would
        // be ok to abort on an uncaught exception at this point
        setUncaughtExceptionCaptureCallback(null);
        try {
          caught = this.emit('error', er);
        } finally {
          updateExceptionCapture();
        }
      }
    } else {
      // Wrap this in a try/catch so we don't get infinite throwing
      try {
        // One of three things will happen here.
        //
        // 1. There is a handler, caught = true
        // 2. There is no handler, caught = false
        // 3. It throws, caught = false
        //
        // If caught is false after this, then there's no need to exit()
        // the domain, because we're going to crash the process anyway.
        caught = this.emit('error', er);
      } catch (er2) {
        // The domain error handler threw!  oh no!
        // See if another domain can catch THIS error,
        // or else crash on the original one.
        // If the user already exited it, then don't double-exit.
        if (this === exports.active) {
          stack.pop();
        }
        updateExceptionCapture();
        if (stack.length) {
          exports.active = process.domain = stack[stack.length - 1];
          caught = process.domain._errorHandler(er2);
        } else {
          // Pass on to the next exception handler.
          throw er2;
        }
      }
    }
  
    // Exit all domains on the stack.  Uncaught exceptions end the
    // current tick and no domains should be left on the stack
    // between ticks.
    domainUncaughtExceptionClear();
  
    return caught;
  };
  
  
  Domain.prototype.enter = function() {
    // Note that this might be a no-op, but we still need
    // to push it onto the stack so that we can pop it later.
    exports.active = process.domain = this;
    stack.push(this);
    updateExceptionCapture();
  };
  
  
  Domain.prototype.exit = function() {
    // Don't do anything if this domain is not on the stack.
    var index = stack.lastIndexOf(this);
    if (index === -1) return;
  
    // exit all domains until this one.
    stack.splice(index);
  
    exports.active = stack[stack.length - 1];
    process.domain = exports.active;
    updateExceptionCapture();
  };
  
  
  // note: this works for timers as well.
  Domain.prototype.add = function(ee) {
    // If the domain is already added, then nothing left to do.
    if (ee.domain === this)
      return;
  
    // has a domain already - remove it first.
    if (ee.domain)
      ee.domain.remove(ee);
  
    // check for circular Domain->Domain links.
    // This causes bad insanity!
    //
    // For example:
    // var d = domain.create();
    // var e = domain.create();
    // d.add(e);
    // e.add(d);
    // e.emit('error', er); // RangeError, stack overflow!
    if (this.domain && (ee instanceof Domain)) {
      for (var d = this.domain; d; d = d.domain) {
        if (ee === d) return;
      }
    }
  
    ee.domain = this;
    this.members.push(ee);
  };
  
  
  Domain.prototype.remove = function(ee) {
    ee.domain = null;
    var index = this.members.indexOf(ee);
    if (index !== -1)
      this.members.splice(index, 1);
  };
  
  
  Domain.prototype.run = function(fn) {
    var ret;
  
    this.enter();
    if (arguments.length >= 2) {
      var len = arguments.length;
      var args = new Array(len - 1);
  
      for (var i = 1; i < len; i++)
        args[i - 1] = arguments[i];
  
      ret = fn.apply(this, args);
    } else {
      ret = fn.call(this);
    }
    this.exit();
  
    return ret;
  };
  
  
  function intercepted(_this, self, cb, fnargs) {
    if (fnargs[0] && fnargs[0] instanceof Error) {
      var er = fnargs[0];
      er.domainBound = cb;
      er.domainThrown = false;
      er.domain = self;
      self.emit('error', er);
      return;
    }
  
    var args = [];
    var i, ret;
  
    self.enter();
    if (fnargs.length > 1) {
      for (i = 1; i < fnargs.length; i++)
        args.push(fnargs[i]);
      ret = cb.apply(_this, args);
    } else {
      ret = cb.call(_this);
    }
    self.exit();
  
    return ret;
  }
  
  
  Domain.prototype.intercept = function(cb) {
    var self = this;
  
    function runIntercepted() {
      return intercepted(this, self, cb, arguments);
    }
  
    return runIntercepted;
  };
  
  
  function bound(_this, self, cb, fnargs) {
    var ret;
  
    self.enter();
    if (fnargs.length > 0)
      ret = cb.apply(_this, fnargs);
    else
      ret = cb.call(_this);
    self.exit();
  
    return ret;
  }
  
  
  Domain.prototype.bind = function(cb) {
    var self = this;
  
    function runBound() {
      return bound(this, self, cb, arguments);
    }
  
    runBound.domain = this;
  
    return runBound;
  };
  
  // Override EventEmitter methods to make it domain-aware.
  EventEmitter.usingDomains = true;
  
  const eventInit = EventEmitter.init;
  EventEmitter.init = function() {
    this.domain = null;
    if (exports.active && !(this instanceof exports.Domain)) {
      this.domain = exports.active;
    }
  
    return eventInit.call(this);
  };
  
  const eventEmit = EventEmitter.prototype.emit;
  EventEmitter.prototype.emit = function(...args) {
    const domain = this.domain;
  
    const type = args[0];
    const shouldEmitError = type === 'error' &&
                            this.listenerCount(type) > 0;
  
    // Just call original `emit` if current EE instance has `error`
    // handler, there's no active domain or this is process
    if (shouldEmitError || domain === null || domain === undefined ||
        this === process) {
      return Reflect.apply(eventEmit, this, args);
    }
  
    if (type === 'error') {
      const er = args.length > 1 && args[1] ?
        args[1] : new ERR_UNHANDLED_ERROR();
  
      if (typeof er === 'object') {
        er.domainEmitter = this;
        er.domain = domain;
        er.domainThrown = false;
      }
  
      domain.emit('error', er);
      return false;
    }
  
    domain.enter();
    const ret = Reflect.apply(eventEmit, this, args);
    domain.exit();
  
    return ret;
  };
  