text: /**
   * @fileoverview Main ESLint object.
   * @author Nicholas C. Zakas
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Requirements
  //------------------------------------------------------------------------------
  
  var lodash = require("lodash"),
      Traverser = require("./util/traverser"),
      escope = require("escope"),
      Environments = require("./config/environments"),
      blankScriptAST = require("../conf/blank-script.json"),
      rules = require("./rules"),
      RuleContext = require("./rule-context"),
      timing = require("./timing"),
      SourceCode = require("./util/source-code"),
      NodeEventGenerator = require("./util/node-event-generator"),
      CommentEventGenerator = require("./util/comment-event-generator"),
      EventEmitter = require("events").EventEmitter,
      ConfigOps = require("./config/config-ops"),
      validator = require("./config/config-validator"),
      replacements = require("../conf/replacements.json"),
      assert = require("assert"),
      CodePathAnalyzer = require("./code-path-analysis/code-path-analyzer");
  
  var DEFAULT_PARSER = require("../conf/eslint.json").parser;
  
  //------------------------------------------------------------------------------
  // Helpers
  //------------------------------------------------------------------------------
  
  /**
   * Parses a list of "name:boolean_value" or/and "name" options divided by comma or
   * whitespace.
   * @param {string} string The string to parse.
   * @param {Comment} comment The comment node which has the string.
   * @returns {Object} Result map object of names and boolean values
   */
  function parseBooleanConfig(string, comment) {
      var items = {};
  
      // Collapse whitespace around : to make parsing easier
      string = string.replace(/\s*:\s*/g, ":");
  
      // Collapse whitespace around ,
      string = string.replace(/\s*,\s*/g, ",");
  
      string.split(/\s|,+/).forEach(function(name) {
          if (!name) {
              return;
          }
          var pos = name.indexOf(":"),
              value;
  
          if (pos !== -1) {
              value = name.substring(pos + 1, name.length);
              name = name.substring(0, pos);
          }
  
          items[name] = {
              value: (value === "true"),
              comment: comment
          };
  
      });
      return items;
  }
  
  /**
   * Parses a JSON-like config.
   * @param {string} string The string to parse.
   * @param {Object} location Start line and column of comments for potential error message.
   * @param {Object[]} messages The messages queue for potential error message.
   * @returns {Object} Result map object
   */
  function parseJsonConfig(string, location, messages) {
      var items = {};
  
      string = string.replace(/([a-zA-Z0-9\-\/]+):/g, "\"$1\":").replace(/(\]|[0-9])\s+(?=")/, "$1,");
      try {
          items = JSON.parse("{" + string + "}");
      } catch (ex) {
  
          messages.push({
              ruleId: null,
              fatal: true,
              severity: 2,
              source: null,
              message: "Failed to parse JSON from '" + string + "': " + ex.message,
              line: location.start.line,
              column: location.start.column + 1
          });
  
      }
  
      return items;
  }
  
  /**
   * Parses a config of values separated by comma.
   * @param {string} string The string to parse.
   * @returns {Object} Result map of values and true values
   */
  function parseListConfig(string) {
      var items = {};
  
      // Collapse whitespace around ,
      string = string.replace(/\s*,\s*/g, ",");
  
      string.split(/,+/).forEach(function(name) {
          name = name.trim();
          if (!name) {
              return;
          }
          items[name] = true;
      });
      return items;
  }
  
  /**
   * Ensures that variables representing built-in properties of the Global Object,
   * and any globals declared by special block comments, are present in the global
   * scope.
   * @param {ASTNode} program The top node of the AST.
   * @param {Scope} globalScope The global scope.
   * @param {Object} config The existing configuration data.
   * @returns {void}
   */
  function addDeclaredGlobals(program, globalScope, config) {
      var declaredGlobals = {},
          exportedGlobals = {},
          explicitGlobals = {},
          builtin = Environments.get("builtin");
  
      lodash.assign(declaredGlobals, builtin);
  
      Object.keys(config.env).forEach(function(name) {
          if (config.env[name]) {
              var env = Environments.get(name),
                  environmentGlobals = env && env.globals;
  
              if (environmentGlobals) {
                  lodash.assign(declaredGlobals, environmentGlobals);
              }
          }
      });
  
      lodash.assign(exportedGlobals, config.exported);
      lodash.assign(declaredGlobals, config.globals);
      lodash.assign(explicitGlobals, config.astGlobals);
  
      Object.keys(declaredGlobals).forEach(function(name) {
          var variable = globalScope.set.get(name);
  
          if (!variable) {
              variable = new escope.Variable(name, globalScope);
              variable.eslintExplicitGlobal = false;
              globalScope.variables.push(variable);
              globalScope.set.set(name, variable);
          }
          variable.writeable = declaredGlobals[name];
      });
  
      Object.keys(explicitGlobals).forEach(function(name) {
          var variable = globalScope.set.get(name);
  
          if (!variable) {
              variable = new escope.Variable(name, globalScope);
              variable.eslintExplicitGlobal = true;
              variable.eslintExplicitGlobalComment = explicitGlobals[name].comment;
              globalScope.variables.push(variable);
              globalScope.set.set(name, variable);
          }
          variable.writeable = explicitGlobals[name].value;
      });
  
      // mark all exported variables as such
      Object.keys(exportedGlobals).forEach(function(name) {
          var variable = globalScope.set.get(name);
  
          if (variable) {
              variable.eslintUsed = true;
          }
      });
  
      /*
       * "through" contains all references which definitions cannot be found.
       * Since we augment the global scope using configuration, we need to update
       * references and remove the ones that were added by configuration.
       */
      globalScope.through = globalScope.through.filter(function(reference) {
          var name = reference.identifier.name;
          var variable = globalScope.set.get(name);
  
          if (variable) {
  
              /*
               * Links the variable and the reference.
               * And this reference is removed from `Scope#through`.
               */
              reference.resolved = variable;
              variable.references.push(reference);
  
              return false;
          }
  
          return true;
      });
  }
  
  /**
   * Add data to reporting configuration to disable reporting for list of rules
   * starting from start location
   * @param  {Object[]} reportingConfig Current reporting configuration
   * @param  {Object} start Position to start
   * @param  {string[]} rulesToDisable List of rules
   * @returns {void}
   */
  function disableReporting(reportingConfig, start, rulesToDisable) {
  
      if (rulesToDisable.length) {
          rulesToDisable.forEach(function(rule) {
              reportingConfig.push({
                  start: start,
                  end: null,
                  rule: rule
              });
          });
      } else {
          reportingConfig.push({
              start: start,
              end: null,
              rule: null
          });
      }
  }
  
  /**
   * Add data to reporting configuration to enable reporting for list of rules
   * starting from start location
   * @param  {Object[]} reportingConfig Current reporting configuration
   * @param  {Object} start Position to start
   * @param  {string[]} rulesToEnable List of rules
   * @returns {void}
   */
  function enableReporting(reportingConfig, start, rulesToEnable) {
      var i;
  
      if (rulesToEnable.length) {
          rulesToEnable.forEach(function(rule) {
              for (i = reportingConfig.length - 1; i >= 0; i--) {
                  if (!reportingConfig[i].end && reportingConfig[i].rule === rule) {
                      reportingConfig[i].end = start;
                      break;
                  }
              }
          });
      } else {
  
          // find all previous disabled locations if they was started as list of rules
          var prevStart;
  
          for (i = reportingConfig.length - 1; i >= 0; i--) {
              if (prevStart && prevStart !== reportingConfig[i].start) {
                  break;
              }
  
              if (!reportingConfig[i].end) {
                  reportingConfig[i].end = start;
                  prevStart = reportingConfig[i].start;
              }
          }
      }
  }
  
  /**
   * Parses comments in file to extract file-specific config of rules, globals
   * and environments and merges them with global config; also code blocks
   * where reporting is disabled or enabled and merges them with reporting config.
   * @param {string} filename The file being checked.
   * @param {ASTNode} ast The top node of the AST.
   * @param {Object} config The existing configuration data.
   * @param {Object[]} reportingConfig The existing reporting configuration data.
   * @param {Object[]} messages The messages queue.
   * @returns {object} Modified config object
   */
  function modifyConfigsFromComments(filename, ast, config, reportingConfig, messages) {
  
      var commentConfig = {
          exported: {},
          astGlobals: {},
          rules: {},
          env: {}
      };
      var commentRules = {};
  
      ast.comments.forEach(function(comment) {
  
          var value = comment.value.trim();
          var match = /^(eslint(-\w+){0,3}|exported|globals?)(\s|$)/.exec(value);
  
          if (match) {
              value = value.substring(match.index + match[1].length);
  
              if (comment.type === "Block") {
                  switch (match[1]) {
                      case "exported":
                          lodash.assign(commentConfig.exported, parseBooleanConfig(value, comment));
                          break;
  
                      case "globals":
                      case "global":
                          lodash.assign(commentConfig.astGlobals, parseBooleanConfig(value, comment));
                          break;
  
                      case "eslint-env":
                          lodash.assign(commentConfig.env, parseListConfig(value));
                          break;
  
                      case "eslint-disable":
                          disableReporting(reportingConfig, comment.loc.start, Object.keys(parseListConfig(value)));
                          break;
  
                      case "eslint-enable":
                          enableReporting(reportingConfig, comment.loc.start, Object.keys(parseListConfig(value)));
                          break;
  
                      case "eslint":
                          var items = parseJsonConfig(value, comment.loc, messages);
  
                          Object.keys(items).forEach(function(name) {
                              var ruleValue = items[name];
  
                              validator.validateRuleOptions(name, ruleValue, filename + " line " + comment.loc.start.line);
                              commentRules[name] = ruleValue;
                          });
                          break;
  
                      // no default
                  }
              } else {        // comment.type === "Line"
                  if (match[1] === "eslint-disable-line") {
                      disableReporting(reportingConfig, { line: comment.loc.start.line, column: 0 }, Object.keys(parseListConfig(value)));
                      enableReporting(reportingConfig, comment.loc.end, Object.keys(parseListConfig(value)));
                  } else if (match[1] === "eslint-disable-next-line") {
                      disableReporting(reportingConfig, comment.loc.start, Object.keys(parseListConfig(value)));
                      enableReporting(reportingConfig, { line: comment.loc.start.line + 2 }, Object.keys(parseListConfig(value)));
                  }
              }
          }
      });
  
      // apply environment configs
      Object.keys(commentConfig.env).forEach(function(name) {
          var env = Environments.get(name);
  
          if (env) {
              commentConfig = ConfigOps.merge(commentConfig, env);
          }
      });
      lodash.assign(commentConfig.rules, commentRules);
  
      return ConfigOps.merge(config, commentConfig);
  }
  
  /**
   * Check if message of rule with ruleId should be ignored in location
   * @param  {Object[]} reportingConfig  Collection of ignore records
   * @param  {string} ruleId   Id of rule
   * @param  {Object} location Location of message
   * @returns {boolean}          True if message should be ignored, false otherwise
   */
  function isDisabledByReportingConfig(reportingConfig, ruleId, location) {
  
      for (var i = 0, c = reportingConfig.length; i < c; i++) {
  
          var ignore = reportingConfig[i];
  
          if ((!ignore.rule || ignore.rule === ruleId) &&
              (location.line > ignore.start.line || (location.line === ignore.start.line && location.column >= ignore.start.column)) &&
              (!ignore.end || (location.line < ignore.end.line || (location.line === ignore.end.line && location.column <= ignore.end.column)))) {
              return true;
          }
      }
  
      return false;
  }
  
  /**
   * Process initial config to make it safe to extend by file comment config
   * @param  {Object} config Initial config
   * @returns {Object}        Processed config
   */
  function prepareConfig(config) {
  
      config.globals = config.globals || config.global || {};
      delete config.global;
  
      var copiedRules = {},
          parserOptions = {},
          preparedConfig;
  
      if (typeof config.rules === "object") {
          Object.keys(config.rules).forEach(function(k) {
              var rule = config.rules[k];
  
              if (rule === null) {
                  throw new Error("Invalid config for rule '" + k + "'\.");
              }
              if (Array.isArray(rule)) {
                  copiedRules[k] = rule.slice();
              } else {
                  copiedRules[k] = rule;
              }
          });
      }
  
      // merge in environment parserOptions
      if (typeof config.env === "object") {
          Object.keys(config.env).forEach(function(envName) {
              var env = Environments.get(envName);
  
              if (config.env[envName] && env && env.parserOptions) {
                  parserOptions = ConfigOps.merge(parserOptions, env.parserOptions);
              }
          });
      }
  
      preparedConfig = {
          rules: copiedRules,
          parser: config.parser || DEFAULT_PARSER,
          globals: ConfigOps.merge({}, config.globals),
          env: ConfigOps.merge({}, config.env || {}),
          settings: ConfigOps.merge({}, config.settings || {}),
          parserOptions: ConfigOps.merge(parserOptions, config.parserOptions || {})
      };
  
      if (preparedConfig.parserOptions.sourceType === "module") {
          if (!preparedConfig.parserOptions.ecmaFeatures) {
              preparedConfig.parserOptions.ecmaFeatures = {};
          }
  
          // can't have global return inside of modules
          preparedConfig.parserOptions.ecmaFeatures.globalReturn = false;
  
          // also need at least ES6 for modules
          if (!preparedConfig.parserOptions.ecmaVersion || preparedConfig.parserOptions.ecmaVersion < 6) {
              preparedConfig.parserOptions.ecmaVersion = 6;
          }
      }
  
      return preparedConfig;
  }
  
  /**
   * Provide a stub rule with a given message
   * @param  {string} message The message to be displayed for the rule
   * @returns {Function}      Stub rule function
   */
  function createStubRule(message) {
  
      /**
       * Creates a fake rule object
       * @param {object} context context object for each rule
       * @returns {object} collection of node to listen on
       */
      function createRuleModule(context) {
          return {
              Program: function(node) {
                  context.report(node, message);
              }
          };
      }
  
      if (message) {
          return createRuleModule;
      } else {
          throw new Error("No message passed to stub rule");
      }
  }
  
  /**
   * Provide a rule replacement message
   * @param  {string} ruleId Name of the rule
   * @returns {string}       Message detailing rule replacement
   */
  function getRuleReplacementMessage(ruleId) {
      if (ruleId in replacements.rules) {
          var newRules = replacements.rules[ruleId];
  
          return "Rule \'" + ruleId + "\' was removed and replaced by: " + newRules.join(", ");
      }
  
      return null;
  }
  
  var eslintEnvPattern = /\/\*\s*eslint-env\s(.+?)\*\//g;
  
  /**
   * Checks whether or not there is a comment which has "eslint-env *" in a given text.
   * @param {string} text - A source code text to check.
   * @returns {object|null} A result of parseListConfig() with "eslint-env *" comment.
   */
  function findEslintEnv(text) {
      var match, retv;
  
      eslintEnvPattern.lastIndex = 0;
  
      while ((match = eslintEnvPattern.exec(text))) {
          retv = lodash.assign(retv || {}, parseListConfig(match[1]));
      }
  
      return retv;
  }
  
  /**
   * Strips Unicode BOM from a given text.
   *
   * @param {string} text - A text to strip.
   * @returns {string} The stripped text.
   */
  function stripUnicodeBOM(text) {
  
      /*
       * Check Unicode BOM.
       * In JavaScript, string data is stored as UTF-16, so BOM is 0xFEFF.
       * http://www.ecma-international.org/ecma-262/6.0/#sec-unicode-format-control-characters
       */
      if (text.charCodeAt(0) === 0xFEFF) {
          return text.slice(1);
      }
      return text;
  }
  
  //------------------------------------------------------------------------------
  // Public Interface
  //------------------------------------------------------------------------------
  
  /**
   * Object that is responsible for verifying JavaScript text
   * @name eslint
   */
  module.exports = (function() {
  
      var api = Object.create(new EventEmitter()),
          messages = [],
          currentConfig = null,
          currentScopes = null,
          scopeMap = null,
          scopeManager = null,
          currentFilename = null,
          traverser = null,
          reportingConfig = [],
          sourceCode = null;
  
      /**
       * Parses text into an AST. Moved out here because the try-catch prevents
       * optimization of functions, so it's best to keep the try-catch as isolated
       * as possible
       * @param {string} text The text to parse.
       * @param {Object} config The ESLint configuration object.
       * @returns {ASTNode} The AST if successful or null if not.
       * @private
       */
      function parse(text, config) {
  
          var parser,
              parserOptions = {
                  loc: true,
                  range: true,
                  raw: true,
                  tokens: true,
                  comment: true,
                  attachComment: true
              };
  
          try {
              parser = require(config.parser);
          } catch (ex) {
              messages.push({
                  ruleId: null,
                  fatal: true,
                  severity: 2,
                  source: null,
                  message: ex.message,
                  line: 0,
                  column: 0
              });
  
              return null;
          }
  
          // merge in any additional parser options
          if (config.parserOptions) {
              parserOptions = lodash.assign({}, config.parserOptions, parserOptions);
          }
  
          /*
           * Check for parsing errors first. If there's a parsing error, nothing
           * else can happen. However, a parsing error does not throw an error
           * from this method - it's just considered a fatal error message, a
           * problem that ESLint identified just like any other.
           */
          try {
              return parser.parse(text, parserOptions);
          } catch (ex) {
  
              // If the message includes a leading line number, strip it:
              var message = ex.message.replace(/^line \d+:/i, "").trim();
              var source = (ex.lineNumber) ? SourceCode.splitLines(text)[ex.lineNumber - 1] : null;
  
              messages.push({
                  ruleId: null,
                  fatal: true,
                  severity: 2,
                  source: source,
                  message: "Parsing error: " + message,
  
                  line: ex.lineNumber,
                  column: ex.column
              });
  
              return null;
          }
      }
  
      /**
       * Get the severity level of a rule (0 - none, 1 - warning, 2 - error)
       * Returns 0 if the rule config is not valid (an Array or a number)
       * @param {Array|number} ruleConfig rule configuration
       * @returns {number} 0, 1, or 2, indicating rule severity
       */
      function getRuleSeverity(ruleConfig) {
          if (typeof ruleConfig === "number") {
              return ruleConfig;
          } else if (Array.isArray(ruleConfig)) {
              return ruleConfig[0];
          } else {
              return 0;
          }
      }
  
      /**
       * Get the options for a rule (not including severity), if any
       * @param {Array|number} ruleConfig rule configuration
       * @returns {Array} of rule options, empty Array if none
       */
      function getRuleOptions(ruleConfig) {
          if (Array.isArray(ruleConfig)) {
              return ruleConfig.slice(1);
          } else {
              return [];
          }
      }
  
      // set unlimited listeners (see https://github.com/eslint/eslint/issues/524)
      api.setMaxListeners(0);
  
      /**
       * Resets the internal state of the object.
       * @returns {void}
       */
      api.reset = function() {
          this.removeAllListeners();
          messages = [];
          currentConfig = null;
          currentScopes = null;
          scopeMap = null;
          scopeManager = null;
          traverser = null;
          reportingConfig = [];
          sourceCode = null;
      };
  
      /**
       * Configuration object for the `verify` API. A JS representation of the eslintrc files.
       * @typedef {Object} ESLintConfig
       * @property {Object} rules The rule configuration to verify against.
       * @property {string} [parser] Parser to use when generatig the AST.
       * @property {Object} [parserOptions] Options for the parsed used.
       * @property {Object} [settings] Global settings passed to each rule.
       * @property {Object} [env] The environment to verify in.
       * @property {Object} [globals] Available globalsto the code.
       */
  
      /**
       * Verifies the text against the rules specified by the second argument.
       * @param {string|SourceCode} textOrSourceCode The text to parse or a SourceCode object.
       * @param {ESLintConfig} config An ESLintConfig instance to configure everything.
       * @param {(string|Object)} [filenameOrOptions] The optional filename of the file being checked.
       *      If this is not set, the filename will default to '<input>' in the rule context. If
       *      an object, then it has "filename", "saveState", and "allowInlineConfig" properties.
       * @param {boolean} [saveState] Indicates if the state from the last run should be saved.
       *      Mostly useful for testing purposes.
       * @param {boolean} [filenameOrOptions.allowInlineConfig] Allow/disallow inline comments' ability to change config once it is set. Defaults to true if not supplied.
       *      Useful if you want to validate JS without comments overriding rules.
       * @returns {Object[]} The results as an array of messages or null if no messages.
       */
      api.verify = function(textOrSourceCode, config, filenameOrOptions, saveState) {
  
          var ast,
              shebang,
              ecmaFeatures,
              ecmaVersion,
              allowInlineConfig,
              text = (typeof textOrSourceCode === "string") ? textOrSourceCode : null;
  
          // evaluate arguments
          if (typeof filenameOrOptions === "object") {
              currentFilename = filenameOrOptions.filename;
              allowInlineConfig = filenameOrOptions.allowInlineConfig;
              saveState = filenameOrOptions.saveState;
          } else {
              currentFilename = filenameOrOptions;
          }
  
          if (!saveState) {
              this.reset();
          }
  
          // search and apply "eslint-env *".
          var envInFile = findEslintEnv(text || textOrSourceCode.text);
  
          if (envInFile) {
              if (!config || !config.env) {
                  config = lodash.assign({}, config || {}, {env: envInFile});
              } else {
                  config = lodash.assign({}, config);
                  config.env = lodash.assign({}, config.env, envInFile);
              }
          }
  
          // process initial config to make it safe to extend
          config = prepareConfig(config || {});
  
          // only do this for text
          if (text !== null) {
  
              // there's no input, just exit here
              if (text.trim().length === 0) {
                  sourceCode = new SourceCode(text, blankScriptAST);
                  return messages;
              }
  
              ast = parse(
                  stripUnicodeBOM(text).replace(/^#!([^\r\n]+)/, function(match, captured) {
                      shebang = captured;
                      return "//" + captured;
                  }),
                  config
              );
  
              if (ast) {
                  sourceCode = new SourceCode(text, ast);
              }
  
          } else {
              sourceCode = textOrSourceCode;
              ast = sourceCode.ast;
          }
  
          // if espree failed to parse the file, there's no sense in setting up rules
          if (ast) {
  
              // parse global comments and modify config
              if (allowInlineConfig !== false) {
                  config = modifyConfigsFromComments(currentFilename, ast, config, reportingConfig, messages);
              }
  
              // ensure that severities are normalized in the config
              ConfigOps.normalize(config);
  
              // enable appropriate rules
              Object.keys(config.rules).filter(function(key) {
                  return getRuleSeverity(config.rules[key]) > 0;
              }).forEach(function(key) {
                  var ruleCreator,
                      severity,
                      options,
                      rule;
  
                  ruleCreator = rules.get(key);
  
                  if (!ruleCreator) {
                      var replacementMsg = getRuleReplacementMessage(key);
  
                      if (replacementMsg) {
                          ruleCreator = createStubRule(replacementMsg);
                      } else {
                          ruleCreator = createStubRule("Definition for rule '" + key + "' was not found");
                      }
                      rules.define(key, ruleCreator);
                  }
  
                  severity = getRuleSeverity(config.rules[key]);
                  options = getRuleOptions(config.rules[key]);
  
                  try {
                      var ruleContext = new RuleContext(
                          key, api, severity, options,
                          config.settings, config.parserOptions, config.parser, ruleCreator.meta);
  
                      rule = ruleCreator.create ? ruleCreator.create(ruleContext) :
                          ruleCreator(ruleContext);
  
                      // add all the node types as listeners
                      Object.keys(rule).forEach(function(nodeType) {
                          api.on(nodeType, timing.enabled
                              ? timing.time(key, rule[nodeType])
                              : rule[nodeType]
                          );
                      });
                  } catch (ex) {
                      ex.message = "Error while loading rule '" + key + "': " + ex.message;
                      throw ex;
                  }
              });
  
              // save config so rules can access as necessary
              currentConfig = config;
              traverser = new Traverser();
  
              ecmaFeatures = currentConfig.parserOptions.ecmaFeatures || {};
              ecmaVersion = currentConfig.parserOptions.ecmaVersion || 5;
  
              // gather scope data that may be needed by the rules
              scopeManager = escope.analyze(ast, {
                  ignoreEval: true,
                  nodejsScope: ecmaFeatures.globalReturn,
                  impliedStrict: ecmaFeatures.impliedStrict,
                  ecmaVersion: ecmaVersion,
                  sourceType: currentConfig.parserOptions.sourceType || "script",
                  fallback: Traverser.getKeys
              });
  
              currentScopes = scopeManager.scopes;
  
              /*
               * Index the scopes by the start range of their block for efficient
               * lookup in getScope.
               */
              scopeMap = [];
  
              currentScopes.forEach(function(scope, index) {
                  var range = scope.block.range[0];
  
                  /*
                   * Sometimes two scopes are returned for a given node. This is
                   * handled later in a known way, so just don't overwrite here.
                   */
                  if (!scopeMap[range]) {
                      scopeMap[range] = index;
                  }
              });
  
              // augment global scope with declared global variables
              addDeclaredGlobals(ast, currentScopes[0], currentConfig);
  
              // remove shebang comments
              if (shebang && ast.comments.length && ast.comments[0].value === shebang) {
                  ast.comments.splice(0, 1);
  
                  if (ast.body.length && ast.body[0].leadingComments && ast.body[0].leadingComments[0].value === shebang) {
                      ast.body[0].leadingComments.splice(0, 1);
                  }
              }
  
              var eventGenerator = new NodeEventGenerator(api);
  
              eventGenerator = new CodePathAnalyzer(eventGenerator);
              eventGenerator = new CommentEventGenerator(eventGenerator, sourceCode);
  
              /*
               * Each node has a type property. Whenever a particular type of
               * node is found, an event is fired. This allows any listeners to
               * automatically be informed that this type of node has been found
               * and react accordingly.
               */
              traverser.traverse(ast, {
                  enter: function(node, parent) {
                      node.parent = parent;
                      eventGenerator.enterNode(node);
                  },
                  leave: function(node) {
                      eventGenerator.leaveNode(node);
                  }
              });
          }
  
          // sort by line and column
          messages.sort(function(a, b) {
              var lineDiff = a.line - b.line;
  
              if (lineDiff === 0) {
                  return a.column - b.column;
              } else {
                  return lineDiff;
              }
          });
  
          return messages;
      };
  
      /**
       * Reports a message from one of the rules.
       * @param {string} ruleId The ID of the rule causing the message.
       * @param {number} severity The severity level of the rule as configured.
       * @param {ASTNode} node The AST node that the message relates to.
       * @param {Object=} location An object containing the error line and column
       *      numbers. If location is not provided the node's start location will
       *      be used.
       * @param {string} message The actual message.
       * @param {Object} opts Optional template data which produces a formatted message
       *     with symbols being replaced by this object's values.
       * @param {Object} fix A fix command description.
       * @param {Object} meta Metadata of the rule
       * @returns {void}
       */
      api.report = function(ruleId, severity, node, location, message, opts, fix, meta) {
          if (node) {
              assert.strictEqual(typeof node, "object", "Node must be an object");
          }
  
          if (typeof location === "string") {
              assert.ok(node, "Node must be provided when reporting error if location is not provided");
  
              meta = fix;
              fix = opts;
              opts = message;
              message = location;
              location = node.loc.start;
          }
  
          // else, assume location was provided, so node may be omitted
  
          if (isDisabledByReportingConfig(reportingConfig, ruleId, location)) {
              return;
          }
  
          if (opts) {
              message = message.replace(/\{\{\s*(.+?)\s*\}\}/g, function(fullMatch, term) {
                  if (term in opts) {
                      return opts[term];
                  }
  
                  // Preserve old behavior: If parameter name not provided, don't replace it.
                  return fullMatch;
              });
          }
  
          var problem = {
              ruleId: ruleId,
              severity: severity,
              message: message,
              line: location.line,
              column: location.column + 1,   // switch to 1-base instead of 0-base
              nodeType: node && node.type,
              source: sourceCode.lines[location.line - 1] || ""
          };
  
          // ensure there's range and text properties as well as metadata switch, otherwise it's not a valid fix
          if (fix && Array.isArray(fix.range) && (typeof fix.text === "string") && (!meta || meta.fixable)) {
              problem.fix = fix;
          }
  
          messages.push(problem);
      };
  
      /**
       * Gets the SourceCode object representing the parsed source.
       * @returns {SourceCode} The SourceCode object.
       */
      api.getSourceCode = function() {
          return sourceCode;
      };
  
      // methods that exist on SourceCode object
      var externalMethods = {
          getSource: "getText",
          getSourceLines: "getLines",
          getAllComments: "getAllComments",
          getNodeByRangeIndex: "getNodeByRangeIndex",
          getComments: "getComments",
          getJSDocComment: "getJSDocComment",
          getFirstToken: "getFirstToken",
          getFirstTokens: "getFirstTokens",
          getLastToken: "getLastToken",
          getLastTokens: "getLastTokens",
          getTokenAfter: "getTokenAfter",
          getTokenBefore: "getTokenBefore",
          getTokenByRangeStart: "getTokenByRangeStart",
          getTokens: "getTokens",
          getTokensAfter: "getTokensAfter",
          getTokensBefore: "getTokensBefore",
          getTokensBetween: "getTokensBetween"
      };
  
      // copy over methods
      Object.keys(externalMethods).forEach(function(methodName) {
          var exMethodName = externalMethods[methodName];
  
          // All functions expected to have less arguments than 5.
          api[methodName] = function(a, b, c, d, e) {
              if (sourceCode) {
                  return sourceCode[exMethodName](a, b, c, d, e);
              }
              return null;
          };
      });
  
      /**
       * Gets nodes that are ancestors of current node.
       * @returns {ASTNode[]} Array of objects representing ancestors.
       */
      api.getAncestors = function() {
          return traverser.parents();
      };
  
      /**
       * Gets the scope for the current node.
       * @returns {Object} An object representing the current node's scope.
       */
      api.getScope = function() {
          var parents = traverser.parents(),
              scope = currentScopes[0];
  
          // Don't do this for Program nodes - they have no parents
          if (parents.length) {
  
              // if current node introduces a scope, add it to the list
              var current = traverser.current();
  
              if (currentConfig.parserOptions.ecmaVersion >= 6) {
                  if (["BlockStatement", "SwitchStatement", "CatchClause", "FunctionDeclaration", "FunctionExpression", "ArrowFunctionExpression"].indexOf(current.type) >= 0) {
                      parents.push(current);
                  }
              } else {
                  if (["FunctionDeclaration", "FunctionExpression", "ArrowFunctionExpression"].indexOf(current.type) >= 0) {
                      parents.push(current);
                  }
              }
  
              // Ascend the current node's parents
              for (var i = parents.length - 1; i >= 0; --i) {
  
                  // Get the innermost scope
                  scope = scopeManager.acquire(parents[i], true);
                  if (scope) {
                      if (scope.type === "function-expression-name") {
                          return scope.childScopes[0];
                      } else {
                          return scope;
                      }
                  }
  
              }
  
          }
  
          return currentScopes[0];
      };
  
      /**
       * Record that a particular variable has been used in code
       * @param {string} name The name of the variable to mark as used
       * @returns {boolean} True if the variable was found and marked as used,
       *      false if not.
       */
      api.markVariableAsUsed = function(name) {
          var scope = this.getScope(),
              hasGlobalReturn = currentConfig.parserOptions.ecmaFeatures && currentConfig.parserOptions.ecmaFeatures.globalReturn,
              specialScope = hasGlobalReturn || currentConfig.parserOptions.sourceType === "module",
              variables,
              i,
              len;
  
          // Special Node.js scope means we need to start one level deeper
          if (scope.type === "global" && specialScope) {
              scope = scope.childScopes[0];
          }
  
          do {
              variables = scope.variables;
              for (i = 0, len = variables.length; i < len; i++) {
                  if (variables[i].name === name) {
                      variables[i].eslintUsed = true;
                      return true;
                  }
              }
          } while ((scope = scope.upper));
  
          return false;
      };
  
      /**
       * Gets the filename for the currently parsed source.
       * @returns {string} The filename associated with the source being parsed.
       *     Defaults to "<input>" if no filename info is present.
       */
      api.getFilename = function() {
          if (typeof currentFilename === "string") {
              return currentFilename;
          } else {
              return "<input>";
          }
      };
  
      /**
       * Defines a new linting rule.
       * @param {string} ruleId A unique rule identifier
       * @param {Function} ruleModule Function from context to object mapping AST node types to event handlers
       * @returns {void}
       */
      var defineRule = api.defineRule = function(ruleId, ruleModule) {
          rules.define(ruleId, ruleModule);
      };
  
      /**
       * Defines many new linting rules.
       * @param {object} rulesToDefine map from unique rule identifier to rule
       * @returns {void}
       */
      api.defineRules = function(rulesToDefine) {
          Object.getOwnPropertyNames(rulesToDefine).forEach(function(ruleId) {
              defineRule(ruleId, rulesToDefine[ruleId]);
          });
      };
  
      /**
       * Gets the default eslint configuration.
       * @returns {Object} Object mapping rule IDs to their default configurations
       */
      api.defaults = function() {
          return require("../conf/eslint.json");
      };
  
      /**
       * Gets variables that are declared by a specified node.
       *
       * The variables are its `defs[].node` or `defs[].parent` is same as the specified node.
       * Specifically, below:
       *
       * - `VariableDeclaration` - variables of its all declarators.
       * - `VariableDeclarator` - variables.
       * - `FunctionDeclaration`/`FunctionExpression` - its function name and parameters.
       * - `ArrowFunctionExpression` - its parameters.
       * - `ClassDeclaration`/`ClassExpression` - its class name.
       * - `CatchClause` - variables of its exception.
       * - `ImportDeclaration` - variables of  its all specifiers.
       * - `ImportSpecifier`/`ImportDefaultSpecifier`/`ImportNamespaceSpecifier` - a variable.
       * - others - always an empty array.
       *
       * @param {ASTNode} node A node to get.
       * @returns {escope.Variable[]} Variables that are declared by the node.
       */
      api.getDeclaredVariables = function(node) {
          return (scopeManager && scopeManager.getDeclaredVariables(node)) || [];
      };
  
      return api;
  
  }());
  