text: "use strict";
  
  var inherits = require('util').inherits
    , f = require('util').format
    , toError = require('./utils').toError
    , getSingleProperty = require('./utils').getSingleProperty
    , formattedOrderClause = require('./utils').formattedOrderClause
    , handleCallback = require('./utils').handleCallback
    , Logger = require('mongodb-core').Logger
    , EventEmitter = require('events').EventEmitter
    , ReadPreference = require('./read_preference')
    , MongoError = require('mongodb-core').MongoError
    , Readable = require('stream').Readable || require('readable-stream').Readable
    , Define = require('./metadata')
    , CoreCursor = require('./cursor')
    , Query = require('mongodb-core').Query
    , CoreReadPreference = require('mongodb-core').ReadPreference;
  
  /**
   * @fileOverview The **AggregationCursor** class is an internal class that embodies an aggregation cursor on MongoDB
   * allowing for iteration over the results returned from the underlying query. It supports
   * one by one document iteration, conversion to an array or can be iterated as a Node 0.10.X
   * or higher stream
   *
   * **AGGREGATIONCURSOR Cannot directly be instantiated**
   * @example
   * var MongoClient = require('mongodb').MongoClient,
   *   test = require('assert');
   * // Connection url
   * var url = 'mongodb://localhost:27017/test';
   * // Connect using MongoClient
   * MongoClient.connect(url, function(err, db) {
   *   // Create a collection we want to drop later
   *   var col = db.collection('createIndexExample1');
   *   // Insert a bunch of documents
   *   col.insert([{a:1, b:1}
   *     , {a:2, b:2}, {a:3, b:3}
   *     , {a:4, b:4}], {w:1}, function(err, result) {
   *     test.equal(null, err);
   *     // Show that duplicate records got dropped
   *     col.aggregation({}, {cursor: {}}).toArray(function(err, items) {
   *       test.equal(null, err);
   *       test.equal(4, items.length);
   *       db.close();
   *     });
   *   });
   * });
   */
  
  /**
   * Namespace provided by the browser.
   * @external Readable
   */
  
  /**
   * Creates a new Aggregation Cursor instance (INTERNAL TYPE, do not instantiate directly)
   * @class AggregationCursor
   * @extends external:Readable
   * @fires AggregationCursor#data
   * @fires AggregationCursor#end
   * @fires AggregationCursor#close
   * @fires AggregationCursor#readable
   * @return {AggregationCursor} an AggregationCursor instance.
   */
  var AggregationCursor = function(bson, ns, cmd, options, topology, topologyOptions) {
    CoreCursor.apply(this, Array.prototype.slice.call(arguments, 0));
    var self = this;
    var state = AggregationCursor.INIT;
    var streamOptions = {};
  
    // MaxTimeMS
    var maxTimeMS = null;
  
    // Get the promiseLibrary
    var promiseLibrary = options.promiseLibrary;
  
    // No promise library selected fall back
    if(!promiseLibrary) {
      promiseLibrary = typeof global.Promise == 'function' ?
        global.Promise : require('es6-promise').Promise;
    }
  
    // Set up
    Readable.call(this, {objectMode: true});
  
    // Internal state
    this.s = {
      // MaxTimeMS
        maxTimeMS: maxTimeMS
      // State
      , state: state
      // Stream options
      , streamOptions: streamOptions
      // BSON
      , bson: bson
      // Namespae
      , ns: ns
      // Command
      , cmd: cmd
      // Options
      , options: options
      // Topology
      , topology: topology
      // Topology Options
      , topologyOptions: topologyOptions
      // Promise library
      , promiseLibrary: promiseLibrary
    }
  }
  
  /**
   * AggregationCursor stream data event, fired for each document in the cursor.
   *
   * @event AggregationCursor#data
   * @type {object}
   */
  
  /**
   * AggregationCursor stream end event
   *
   * @event AggregationCursor#end
   * @type {null}
   */
  
  /**
   * AggregationCursor stream close event
   *
   * @event AggregationCursor#close
   * @type {null}
   */
  
  /**
   * AggregationCursor stream readable event
   *
   * @event AggregationCursor#readable
   * @type {null}
   */
  
  // Inherit from Readable
  inherits(AggregationCursor, Readable);
  
  // Set the methods to inherit from prototype
  var methodsToInherit = ['_next', 'next', 'each', 'forEach', 'toArray'
    , 'rewind', 'bufferedCount', 'readBufferedDocuments', 'close', 'isClosed', 'kill'
    , '_find', '_getmore', '_killcursor', 'isDead', 'explain', 'isNotified'];
  
  // Extend the Cursor
  for(var name in CoreCursor.prototype) {
    AggregationCursor.prototype[name] = CoreCursor.prototype[name];
  }
  
  var define = AggregationCursor.define = new Define('AggregationCursor', AggregationCursor, true);
  
  /**
   * Set the batch size for the cursor.
   * @method
   * @param {number} value The batchSize for the cursor.
   * @throws {MongoError}
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.batchSize = function(value) {
    if(this.s.state == AggregationCursor.CLOSED || this.isDead()) throw MongoError.create({message: "Cursor is closed", driver:true });
    if(typeof value != 'number') throw MongoError.create({message: "batchSize requires an integer", drvier:true });
    if(this.s.cmd.cursor) this.s.cmd.cursor.batchSize = value;
    this.setCursorBatchSize(value);
    return this;
  }
  
  define.classMethod('batchSize', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a geoNear stage to the aggregation pipeline
   * @method
   * @param {object} document The geoNear stage document.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.geoNear = function(document) {
    this.s.cmd.pipeline.push({$geoNear: document});
    return this;
  }
  
  define.classMethod('geoNear', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a group stage to the aggregation pipeline
   * @method
   * @param {object} document The group stage document.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.group = function(document) {
    this.s.cmd.pipeline.push({$group: document});
    return this;
  }
  
  define.classMethod('group', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a limit stage to the aggregation pipeline
   * @method
   * @param {number} value The state limit value.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.limit = function(value) {
    this.s.cmd.pipeline.push({$limit: value});
    return this;
  }
  
  define.classMethod('limit', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a match stage to the aggregation pipeline
   * @method
   * @param {object} document The match stage document.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.match = function(document) {
    this.s.cmd.pipeline.push({$match: document});
    return this;
  }
  
  define.classMethod('match', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a maxTimeMS stage to the aggregation pipeline
   * @method
   * @param {number} value The state maxTimeMS value.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.maxTimeMS = function(value) {
    if(this.s.topology.lastIsMaster().minWireVersion > 2) {
      this.s.cmd.maxTimeMS = value;
    }
    return this;
  }
  
  define.classMethod('maxTimeMS', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a out stage to the aggregation pipeline
   * @method
   * @param {number} destination The destination name.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.out = function(destination) {
    this.s.cmd.pipeline.push({$out: destination});
    return this;
  }
  
  define.classMethod('out', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a project stage to the aggregation pipeline
   * @method
   * @param {object} document The project stage document.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.project = function(document) {
    this.s.cmd.pipeline.push({$project: document});
    return this;
  }
  
  define.classMethod('project', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a lookup stage to the aggregation pipeline
   * @method
   * @param {object} document The lookup stage document.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.lookup = function(document) {
    this.s.cmd.pipeline.push({$lookup: document});
    return this;
  }
  
  define.classMethod('lookup', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a redact stage to the aggregation pipeline
   * @method
   * @param {object} document The redact stage document.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.redact = function(document) {
    this.s.cmd.pipeline.push({$redact: document});
    return this;
  }
  
  define.classMethod('redact', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a skip stage to the aggregation pipeline
   * @method
   * @param {number} value The state skip value.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.skip = function(value) {
    this.s.cmd.pipeline.push({$skip: value});
    return this;
  }
  
  define.classMethod('skip', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a sort stage to the aggregation pipeline
   * @method
   * @param {object} document The sort stage document.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.sort = function(document) {
    this.s.cmd.pipeline.push({$sort: document});
    return this;
  }
  
  define.classMethod('sort', {callback: false, promise:false, returns: [AggregationCursor]});
  
  /**
   * Add a unwind stage to the aggregation pipeline
   * @method
   * @param {number} field The unwind field name.
   * @return {AggregationCursor}
   */
  AggregationCursor.prototype.unwind = function(field) {
    this.s.cmd.pipeline.push({$unwind: field});
    return this;
  }
  
  define.classMethod('unwind', {callback: false, promise:false, returns: [AggregationCursor]});
  
  AggregationCursor.prototype.get = AggregationCursor.prototype.toArray;
  
  // Inherited methods
  define.classMethod('toArray', {callback: true, promise:true});
  define.classMethod('each', {callback: true, promise:false});
  define.classMethod('forEach', {callback: true, promise:false});
  define.classMethod('next', {callback: true, promise:true});
  define.classMethod('close', {callback: true, promise:true});
  define.classMethod('isClosed', {callback: false, promise:false, returns: [Boolean]});
  define.classMethod('rewind', {callback: false, promise:false});
  define.classMethod('bufferedCount', {callback: false, promise:false, returns: [Number]});
  define.classMethod('readBufferedDocuments', {callback: false, promise:false, returns: [Array]});
  
  /**
   * Get the next available document from the cursor, returns null if no more documents are available.
   * @function AggregationCursor.prototype.next
   * @param {AggregationCursor~resultCallback} [callback] The result callback.
   * @throws {MongoError}
   * @return {Promise} returns Promise if no callback passed
   */
  
  /**
   * The callback format for results
   * @callback AggregationCursor~toArrayResultCallback
   * @param {MongoError} error An error instance representing the error during the execution.
   * @param {object[]} documents All the documents the satisfy the cursor.
   */
  
  /**
   * Returns an array of documents. The caller is responsible for making sure that there
   * is enough memory to store the results. Note that the array only contain partial
   * results when this cursor had been previouly accessed. In that case,
   * cursor.rewind() can be used to reset the cursor.
   * @method AggregationCursor.prototype.toArray
   * @param {AggregationCursor~toArrayResultCallback} [callback] The result callback.
   * @throws {MongoError}
   * @return {Promise} returns Promise if no callback passed
   */
  
  /**
   * The callback format for results
   * @callback AggregationCursor~resultCallback
   * @param {MongoError} error An error instance representing the error during the execution.
   * @param {(object|null)} result The result object if the command was executed successfully.
   */
  
  /**
   * Iterates over all the documents for this cursor. As with **{cursor.toArray}**,
   * not all of the elements will be iterated if this cursor had been previouly accessed.
   * In that case, **{cursor.rewind}** can be used to reset the cursor. However, unlike
   * **{cursor.toArray}**, the cursor will only hold a maximum of batch size elements
   * at any given time if batch size is specified. Otherwise, the caller is responsible
   * for making sure that the entire result can fit the memory.
   * @method AggregationCursor.prototype.each
   * @param {AggregationCursor~resultCallback} callback The result callback.
   * @throws {MongoError}
   * @return {null}
   */
  
  /**
   * Close the cursor, sending a AggregationCursor command and emitting close.
   * @method AggregationCursor.prototype.close
   * @param {AggregationCursor~resultCallback} [callback] The result callback.
   * @return {Promise} returns Promise if no callback passed
   */
  
  /**
   * Is the cursor closed
   * @method AggregationCursor.prototype.isClosed
   * @return {boolean}
   */
  
  /**
   * Execute the explain for the cursor
   * @method AggregationCursor.prototype.explain
   * @param {AggregationCursor~resultCallback} [callback] The result callback.
   * @return {Promise} returns Promise if no callback passed
   */
  
  /**
   * Clone the cursor
   * @function AggregationCursor.prototype.clone
   * @return {AggregationCursor}
   */
  
  /**
   * Resets the cursor
   * @function AggregationCursor.prototype.rewind
   * @return {AggregationCursor}
   */
  
  /**
   * The callback format for the forEach iterator method
   * @callback AggregationCursor~iteratorCallback
   * @param {Object} doc An emitted document for the iterator
   */
  
  /**
   * The callback error format for the forEach iterator method
   * @callback AggregationCursor~endCallback
   * @param {MongoError} error An error instance representing the error during the execution.
   */
  
  /*
   * Iterates over all the documents for this cursor using the iterator, callback pattern.
   * @method AggregationCursor.prototype.forEach
   * @param {AggregationCursor~iteratorCallback} iterator The iteration callback.
   * @param {AggregationCursor~endCallback} callback The end callback.
   * @throws {MongoError}
   * @return {null}
   */
  
  AggregationCursor.INIT = 0;
  AggregationCursor.OPEN = 1;
  AggregationCursor.CLOSED = 2;
  
  module.exports = AggregationCursor;
  