'use strict';

var checkCollectionName = require('./utils').checkCollectionName,
  ObjectID = require('mongodb-core').BSON.ObjectID,
  Long = require('mongodb-core').BSON.Long,
  Code = require('mongodb-core').BSON.Code,
  f = require('util').format,
  AggregationCursor = require('./aggregation_cursor'),
  MongoError = require('mongodb-core').MongoError,
  shallowClone = require('./utils').shallowClone,
  isObject = require('./utils').isObject,
  toError = require('./utils').toError,
  normalizeHintField = require('./utils').normalizeHintField,
  handleCallback = require('./utils').handleCallback,
  decorateCommand = require('./utils').decorateCommand,
  formattedOrderClause = require('./utils').formattedOrderClause,
  ReadPreference = require('mongodb-core').ReadPreference,
  CommandCursor = require('./command_cursor'),
  Define = require('./metadata'),
  Cursor = require('./cursor'),
  unordered = require('./bulk/unordered'),
  ordered = require('./bulk/ordered'),
  ChangeStream = require('./change_stream'),
  executeOperation = require('./utils').executeOperation;

/**
 * @fileOverview The **Collection** class is an internal class that embodies a MongoDB collection
 * allowing for insert/update/remove/find and other command operation on that MongoDB collection.
 *
 * **COLLECTION Cannot directly be instantiated**
 * @example
 * const MongoClient = require('mongodb').MongoClient;
 * const test = require('assert');
 * // Connection url
 * const url = 'mongodb://localhost:27017';
 * // Database Name
 * const dbName = 'test';
 * // Connect using MongoClient
 * MongoClient.connect(url, function(err, client) {
 *   // Create a collection we want to drop later
 *   const col = client.db(dbName).collection('createIndexExample1');
 *   // Show that duplicate records got dropped
 *   col.find({}).toArray(function(err, items) {
 *     test.equal(null, err);
 *     test.equal(4, items.length);
 *     client.close();
 *   });
 * });
 */

var mergeKeys = ['readPreference', 'ignoreUndefined'];

/**
 * Create a new Collection instance (INTERNAL TYPE, do not instantiate directly)
 * @class
 * @property {string} collectionName Get the collection name.
 * @property {string} namespace Get the full collection namespace.
 * @property {object} writeConcern The current write concern values.
 * @property {object} readConcern The current read concern values.
 * @property {object} hint Get current index hint for collection.
 * @return {Collection} a Collection instance.
 */
var Collection = function(db, topology, dbName, name, pkFactory, options) {
  checkCollectionName(name);

  // Unpack variables
  var internalHint = null;
  var slaveOk = options == null || options.slaveOk == null ? db.slaveOk : options.slaveOk;
  var serializeFunctions =
    options == null || options.serializeFunctions == null
      ? db.s.options.serializeFunctions
      : options.serializeFunctions;
  var raw = options == null || options.raw == null ? db.s.options.raw : options.raw;
  var promoteLongs =
    options == null || options.promoteLongs == null
      ? db.s.options.promoteLongs
      : options.promoteLongs;
  var promoteValues =
    options == null || options.promoteValues == null
      ? db.s.options.promoteValues
      : options.promoteValues;
  var promoteBuffers =
    options == null || options.promoteBuffers == null
      ? db.s.options.promoteBuffers
      : options.promoteBuffers;
  var readPreference = null;
  var collectionHint = null;
  var namespace = f('%s.%s', dbName, name);

  // Get the promiseLibrary
  var promiseLibrary = options.promiseLibrary || Promise;

  // Assign the right collection level readPreference
  if (options && options.readPreference) {
    readPreference = options.readPreference;
  } else if (db.options.readPreference) {
    readPreference = db.options.readPreference;
  }

  // Set custom primary key factory if provided
  pkFactory = pkFactory == null ? ObjectID : pkFactory;

  // Internal state
  this.s = {
    // Set custom primary key factory if provided
    pkFactory: pkFactory,
    // Db
    db: db,
    // Topology
    topology: topology,
    // dbName
    dbName: dbName,
    // Options
    options: options,
    // Namespace
    namespace: namespace,
    // Read preference
    readPreference: readPreference,
    // SlaveOK
    slaveOk: slaveOk,
    // Serialize functions
    serializeFunctions: serializeFunctions,
    // Raw
    raw: raw,
    // promoteLongs
    promoteLongs: promoteLongs,
    // promoteValues
    promoteValues: promoteValues,
    // promoteBuffers
    promoteBuffers: promoteBuffers,
    // internalHint
    internalHint: internalHint,
    // collectionHint
    collectionHint: collectionHint,
    // Name
    name: name,
    // Promise library
    promiseLibrary: promiseLibrary,
    // Read Concern
    readConcern: options.readConcern
  };
};

var define = (Collection.define = new Define('Collection', Collection, false));

Object.defineProperty(Collection.prototype, 'dbName', {
  enumerable: true,
  get: function() {
    return this.s.dbName;
  }
});

Object.defineProperty(Collection.prototype, 'collectionName', {
  enumerable: true,
  get: function() {
    return this.s.name;
  }
});

Object.defineProperty(Collection.prototype, 'namespace', {
  enumerable: true,
  get: function() {
    return this.s.namespace;
  }
});

Object.defineProperty(Collection.prototype, 'readConcern', {
  enumerable: true,
  get: function() {
    return this.s.readConcern || { level: 'local' };
  }
});

Object.defineProperty(Collection.prototype, 'writeConcern', {
  enumerable: true,
  get: function() {
    var ops = {};
    if (this.s.options.w != null) ops.w = this.s.options.w;
    if (this.s.options.j != null) ops.j = this.s.options.j;
    if (this.s.options.fsync != null) ops.fsync = this.s.options.fsync;
    if (this.s.options.wtimeout != null) ops.wtimeout = this.s.options.wtimeout;
    return ops;
  }
});

/**
 * @ignore
 */
Object.defineProperty(Collection.prototype, 'hint', {
  enumerable: true,
  get: function() {
    return this.s.collectionHint;
  },
  set: function(v) {
    this.s.collectionHint = normalizeHintField(v);
  }
});

/**
 * Creates a cursor for a query that can be used to iterate over results from MongoDB
 * @method
 * @param {object} [query={}] The cursor query object.
 * @param {object} [options=null] Optional settings.
 * @param {number} [options.limit=0] Sets the limit of documents returned in the query.
 * @param {(array|object)} [options.sort=null] Set to sort the documents coming back from the query. Array of indexes, [['a', 1]] etc.
 * @param {object} [options.projection=null] The fields to return in the query. Object of fields to include or exclude (not both), {'a':1}
 * @param {object} [options.fields=null] **Deprecated** Use `options.projection` instead
 * @param {number} [options.skip=0] Set to skip N documents ahead in your query (useful for pagination).
 * @param {Object} [options.hint=null] Tell the query to use specific indexes in the query. Object of indexes to use, {'_id':1}
 * @param {boolean} [options.explain=false] Explain the query instead of returning the data.
 * @param {boolean} [options.snapshot=false] Snapshot query.
 * @param {boolean} [options.timeout=false] Specify if the cursor can timeout.
 * @param {boolean} [options.tailable=false] Specify if the cursor is tailable.
 * @param {number} [options.batchSize=0] Set the batchSize for the getMoreCommand when iterating over the query results.
 * @param {boolean} [options.returnKey=false] Only return the index key.
 * @param {number} [options.maxScan=null] Limit the number of items to scan.
 * @param {number} [options.min=null] Set index bounds.
 * @param {number} [options.max=null] Set index bounds.
 * @param {boolean} [options.showDiskLoc=false] Show disk location of results.
 * @param {string} [options.comment=null] You can put a $comment field on a query to make looking in the profiler logs simpler.
 * @param {boolean} [options.raw=false] Return document results as raw BSON buffers.
 * @param {boolean} [options.promoteLongs=true] Promotes Long values to number if they fit inside the 53 bits resolution.
 * @param {boolean} [options.promoteValues=true] Promotes BSON values to native types where possible, set to false to only receive wrapper types.
 * @param {boolean} [options.promoteBuffers=false] Promotes Binary BSON values to native Node Buffers.
 * @param {(ReadPreference|string)} [options.readPreference=null] The preferred read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
 * @param {boolean} [options.partial=false] Specify if the cursor should return partial results when querying against a sharded system
 * @param {number} [options.maxTimeMS=null] Number of miliseconds to wait before aborting the query.
 * @param {object} [options.collation=null] Specify collation (MongoDB 3.4 or higher) settings for update operation (see 3.4 documentation for available fields).
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @throws {MongoError}
 * @return {Cursor}
 */
Collection.prototype.find = function(query, options, callback) {
  let selector = query;
  // figuring out arguments
  if (typeof callback !== 'function') {
    if (typeof options === 'function') {
      callback = options;
      options = undefined;
    } else if (options == null) {
      callback = typeof selector === 'function' ? selector : undefined;
      selector = typeof selector === 'object' ? selector : undefined;
    }
  }

  // Ensure selector is not null
  selector = selector == null ? {} : selector;
  // Validate correctness off the selector
  var object = selector;
  if (Buffer.isBuffer(object)) {
    var object_size = object[0] | (object[1] << 8) | (object[2] << 16) | (object[3] << 24);
    if (object_size !== object.length) {
      var error = new Error(
        'query selector raw message size does not match message header size [' +
          object.length +
          '] != [' +
          object_size +
          ']'
      );
      error.name = 'MongoError';
      throw error;
    }
  }

  // Check special case where we are using an objectId
  if (selector != null && selector._bsontype === 'ObjectID') {
    selector = { _id: selector };
  }

  if (!options) options = {};

  let projection = options.projection || options.fields;

  if (projection && !Buffer.isBuffer(projection) && Array.isArray(projection)) {
    projection = projection.length
      ? projection.reduce((result, field) => {
          result[field] = 1;
          return result;
        }, {})
      : { _id: 1 };
  }

  var newOptions = {};

  // Make a shallow copy of the collection options
  for (var key in this.s.options) {
    if (mergeKeys.indexOf(key) !== -1) {
      newOptions[key] = this.s.options[key];
    }
  }

  // Make a shallow copy of options
  for (var optKey in options) {
    newOptions[optKey] = options[optKey];
  }

  // Unpack options
  newOptions.skip = options.skip ? options.skip : 0;
  newOptions.limit = options.limit ? options.limit : 0;
  newOptions.raw = typeof options.raw === 'boolean' ? options.raw : this.s.raw;
  newOptions.hint = options.hint != null ? normalizeHintField(options.hint) : this.s.collectionHint;
  newOptions.timeout = typeof options.timeout === 'undefined' ? undefined : options.timeout;
  // // If we have overridden slaveOk otherwise use the default db setting
  newOptions.slaveOk = options.slaveOk != null ? options.slaveOk : this.s.db.slaveOk;

  // Add read preference if needed
  newOptions = getReadPreference(this, newOptions, this.s.db);

  // Set slave ok to true if read preference different from primary
  if (
    newOptions.readPreference != null &&
    (newOptions.readPreference !== 'primary' || newOptions.readPreference.mode !== 'primary')
  ) {
    newOptions.slaveOk = true;
  }

  // Ensure the query is an object
  if (selector != null && typeof selector !== 'object') {
    throw MongoError.create({ message: 'query selector must be an object', driver: true });
  }

  // Build the find command
  var findCommand = {
    find: this.s.namespace,
    limit: newOptions.limit,
    skip: newOptions.skip,
    query: selector
  };

  // Ensure we use the right await data option
  if (typeof newOptions.awaitdata === 'boolean') {
    newOptions.awaitData = newOptions.awaitdata;
  }

  // Translate to new command option noCursorTimeout
  if (typeof newOptions.timeout === 'boolean') newOptions.noCursorTimeout = newOptions.timeout;

  // Merge in options to command
  for (var name in newOptions) {
    if (newOptions[name] != null && name !== 'session') {
      findCommand[name] = newOptions[name];
    }
  }

  if (projection) findCommand.fields = projection;

  // Add db object to the new options
  newOptions.db = this.s.db;

  // Add the promise library
  newOptions.promiseLibrary = this.s.promiseLibrary;

  // Set raw if available at collection level
  if (newOptions.raw == null && typeof this.s.raw === 'boolean') newOptions.raw = this.s.raw;
  // Set promoteLongs if available at collection level
  if (newOptions.promoteLongs == null && typeof this.s.promoteLongs === 'boolean')
    newOptions.promoteLongs = this.s.promoteLongs;
  if (newOptions.promoteValues == null && typeof this.s.promoteValues === 'boolean')
    newOptions.promoteValues = this.s.promoteValues;
  if (newOptions.promoteBuffers == null && typeof this.s.promoteBuffers === 'boolean')
    newOptions.promoteBuffers = this.s.promoteBuffers;

  // Sort options
  if (findCommand.sort) {
    findCommand.sort = formattedOrderClause(findCommand.sort);
  }

  // Set the readConcern
  decorateWithReadConcern(findCommand, this, options);

  // Decorate find command with collation options
  decorateWithCollation(findCommand, this, options);

  // Create the cursor
  if (typeof callback === 'function')
    return handleCallback(
      callback,
      null,
      this.s.topology.cursor(this.s.namespace, findCommand, newOptions)
    );
  return this.s.topology.cursor(this.s.namespace, findCommand, newOptions);
};

define.classMethod('find', { callback: false, promise: false, returns: [Cursor] });

/**
 * Inserts a single document into MongoDB. If documents passed in do not contain the **_id** field,
 * one will be added to each of the documents missing it by the driver, mutating the document. This behavior
 * can be overridden by setting the **forceServerObjectId** flag.
 *
 * @method
 * @param {object} doc Document to insert.
 * @param {object} [options=null] Optional settings.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {boolean} [options.serializeFunctions=false] Serialize functions on any object.
 * @param {boolean} [options.forceServerObjectId=false] Force server to assign _id values instead of driver.
 * @param {boolean} [options.bypassDocumentValidation=false] Allow driver to bypass schema validation in MongoDB 3.2 or higher.
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~insertOneWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 */
Collection.prototype.insertOne = function(doc, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = options || {};

  // Add ignoreUndfined
  if (this.s.options.ignoreUndefined) {
    options = shallowClone(options);
    options.ignoreUndefined = this.s.options.ignoreUndefined;
  }

  return executeOperation(this.s.topology, insertOne, [this, doc, options, callback]);
};

var insertOne = function(self, doc, options, callback) {
  if (Array.isArray(doc)) {
    return callback(
      MongoError.create({ message: 'doc parameter must be an object', driver: true })
    );
  }

  insertDocuments(self, [doc], options, function(err, r) {
    if (callback == null) return;
    if (err && callback) return callback(err);
    // Workaround for pre 2.6 servers
    if (r == null) return callback(null, { result: { ok: 1 } });
    // Add values to top level to ensure crud spec compatibility
    r.insertedCount = r.result.n;
    r.insertedId = doc._id;
    if (callback) callback(null, r);
  });
};

var mapInserManyResults = function(docs, r) {
  var finalResult = {
    result: { ok: 1, n: r.insertedCount },
    ops: docs,
    insertedCount: r.insertedCount,
    insertedIds: r.insertedIds
  };

  if (r.getLastOp()) {
    finalResult.result.opTime = r.getLastOp();
  }

  return finalResult;
};

define.classMethod('insertOne', { callback: true, promise: true });

/**
 * Inserts an array of documents into MongoDB. If documents passed in do not contain the **_id** field,
 * one will be added to each of the documents missing it by the driver, mutating the document. This behavior
 * can be overridden by setting the **forceServerObjectId** flag.
 *
 * @method
 * @param {object[]} docs Documents to insert.
 * @param {object} [options=null] Optional settings.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {boolean} [options.serializeFunctions=false] Serialize functions on any object.
 * @param {boolean} [options.forceServerObjectId=false] Force server to assign _id values instead of driver.
 * @param {boolean} [options.bypassDocumentValidation=false] Allow driver to bypass schema validation in MongoDB 3.2 or higher.
 * @param {boolean} [options.ordered=true] If true, when an insert fails, don't execute the remaining writes. If false, continue with remaining inserts when one fails.
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~insertWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 */
Collection.prototype.insertMany = function(docs, options, callback) {
  var self = this;
  if (typeof options === 'function') (callback = options), (options = {});
  options = options ? shallowClone(options) : { ordered: true };
  if (!Array.isArray(docs) && typeof callback === 'function') {
    return callback(
      MongoError.create({ message: 'docs parameter must be an array of documents', driver: true })
    );
  } else if (!Array.isArray(docs)) {
    return new this.s.promiseLibrary(function(resolve, reject) {
      reject(
        MongoError.create({ message: 'docs parameter must be an array of documents', driver: true })
      );
    });
  }

  // If keep going set unordered
  options['serializeFunctions'] = options['serializeFunctions'] || self.s.serializeFunctions;

  // Set up the force server object id
  var forceServerObjectId =
    typeof options.forceServerObjectId === 'boolean'
      ? options.forceServerObjectId
      : self.s.db.options.forceServerObjectId;

  // Do we want to force the server to assign the _id key
  if (forceServerObjectId !== true) {
    // Add _id if not specified
    for (var i = 0; i < docs.length; i++) {
      if (docs[i]._id == null) docs[i]._id = self.s.pkFactory.createPk();
    }
  }

  // Generate the bulk write operations
  var operations = [
    {
      insertMany: docs
    }
  ];

  return executeOperation(this.s.topology, bulkWrite, [this, operations, options, callback], {
    resultMutator: result => mapInserManyResults(docs, result)
  });
};

define.classMethod('insertMany', { callback: true, promise: true });

/**
 * @typedef {Object} Collection~BulkWriteOpResult
 * @property {number} insertedCount Number of documents inserted.
 * @property {number} matchedCount Number of documents matched for update.
 * @property {number} modifiedCount Number of documents modified.
 * @property {number} deletedCount Number of documents deleted.
 * @property {number} upsertedCount Number of documents upserted.
 * @property {object} insertedIds Inserted document generated Id's, hash key is the index of the originating operation
 * @property {object} upsertedIds Upserted document generated Id's, hash key is the index of the originating operation
 * @property {object} result The command result object.
 */

/**
 * The callback format for inserts
 * @callback Collection~bulkWriteOpCallback
 * @param {BulkWriteError} error An error instance representing the error during the execution.
 * @param {Collection~BulkWriteOpResult} result The result object if the command was executed successfully.
 */

/**
 * Perform a bulkWrite operation without a fluent API
 *
 * Legal operation types are
 *
 *  { insertOne: { document: { a: 1 } } }
 *
 *  { updateOne: { filter: {a:2}, update: {$set: {a:2}}, upsert:true } }
 *
 *  { updateMany: { filter: {a:2}, update: {$set: {a:2}}, upsert:true } }
 *
 *  { deleteOne: { filter: {c:1} } }
 *
 *  { deleteMany: { filter: {c:1} } }
 *
 *  { replaceOne: { filter: {c:3}, replacement: {c:4}, upsert:true}}
 *
 * If documents passed in do not contain the **_id** field,
 * one will be added to each of the documents missing it by the driver, mutating the document. This behavior
 * can be overridden by setting the **forceServerObjectId** flag.
 *
 * @method
 * @param {object[]} operations Bulk operations to perform.
 * @param {object} [options=null] Optional settings.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {boolean} [options.serializeFunctions=false] Serialize functions on any object.
 * @param {boolean} [options.ordered=true] Execute write operation in ordered or unordered fashion.
 * @param {boolean} [options.bypassDocumentValidation=false] Allow driver to bypass schema validation in MongoDB 3.2 or higher.
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~bulkWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 */
Collection.prototype.bulkWrite = function(operations, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = options || { ordered: true };

  if (!Array.isArray(operations)) {
    throw MongoError.create({ message: 'operations must be an array of documents', driver: true });
  }

  return executeOperation(this.s.topology, bulkWrite, [this, operations, options, callback]);
};

var bulkWrite = function(self, operations, options, callback) {
  // Add ignoreUndfined
  if (self.s.options.ignoreUndefined) {
    options = shallowClone(options);
    options.ignoreUndefined = self.s.options.ignoreUndefined;
  }

  // Create the bulk operation
  var bulk =
    options.ordered === true || options.ordered == null
      ? self.initializeOrderedBulkOp(options)
      : self.initializeUnorderedBulkOp(options);

  // Do we have a collation
  var collation = false;

  // for each op go through and add to the bulk
  try {
    for (var i = 0; i < operations.length; i++) {
      // Get the operation type
      var key = Object.keys(operations[i])[0];
      // Check if we have a collation
      if (operations[i][key].collation) {
        collation = true;
      }

      // Pass to the raw bulk
      bulk.raw(operations[i]);
    }
  } catch (err) {
    return callback(err, null);
  }

  // Final options for write concern
  var finalOptions = writeConcern(shallowClone(options), self.s.db, self, options);
  var writeCon = finalOptions.writeConcern ? finalOptions.writeConcern : {};
  var capabilities = self.s.topology.capabilities();

  // Did the user pass in a collation, check if our write server supports it
  if (collation && capabilities && !capabilities.commandsTakeCollation) {
    return callback(new MongoError(f('server/primary/mongos does not support collation')));
  }

  // Execute the bulk
  bulk.execute(writeCon, finalOptions, function(err, r) {
    // We have connection level error
    if (!r && err) {
      return callback(err, null);
    }

    r.insertedCount = r.nInserted;
    r.matchedCount = r.nMatched;
    r.modifiedCount = r.nModified || 0;
    r.deletedCount = r.nRemoved;
    r.upsertedCount = r.getUpsertedIds().length;
    r.upsertedIds = {};
    r.insertedIds = {};

    // Update the n
    r.n = r.insertedCount;

    // Inserted documents
    var inserted = r.getInsertedIds();
    // Map inserted ids
    for (var i = 0; i < inserted.length; i++) {
      r.insertedIds[inserted[i].index] = inserted[i]._id;
    }

    // Upserted documents
    var upserted = r.getUpsertedIds();
    // Map upserted ids
    for (i = 0; i < upserted.length; i++) {
      r.upsertedIds[upserted[i].index] = upserted[i]._id;
    }

    // Return the results
    callback(null, r);
  });
};

var insertDocuments = function(self, docs, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = options || {};
  // Ensure we are operating on an array op docs
  docs = Array.isArray(docs) ? docs : [docs];

  // Get the write concern options
  var finalOptions = writeConcern(shallowClone(options), self.s.db, self, options);

  // If keep going set unordered
  if (finalOptions.keepGoing === true) finalOptions.ordered = false;
  finalOptions['serializeFunctions'] = options['serializeFunctions'] || self.s.serializeFunctions;

  // Set up the force server object id
  var forceServerObjectId =
    typeof options.forceServerObjectId === 'boolean'
      ? options.forceServerObjectId
      : self.s.db.options.forceServerObjectId;

  // Add _id if not specified
  if (forceServerObjectId !== true) {
    for (var i = 0; i < docs.length; i++) {
      if (docs[i]._id === void 0) docs[i]._id = self.s.pkFactory.createPk();
    }
  }

  // File inserts
  self.s.topology.insert(self.s.namespace, docs, finalOptions, function(err, result) {
    if (callback == null) return;
    if (err) return handleCallback(callback, err);
    if (result == null) return handleCallback(callback, null, null);
    if (result.result.code) return handleCallback(callback, toError(result.result));
    if (result.result.writeErrors)
      return handleCallback(callback, toError(result.result.writeErrors[0]));
    // Add docs to the list
    result.ops = docs;
    // Return the results
    handleCallback(callback, null, result);
  });
};

define.classMethod('bulkWrite', { callback: true, promise: true });

/**
 * @typedef {Object} Collection~WriteOpResult
 * @property {object[]} ops All the documents inserted using insertOne/insertMany/replaceOne. Documents contain the _id field if forceServerObjectId == false for insertOne/insertMany
 * @property {object} connection The connection object used for the operation.
 * @property {object} result The command result object.
 */

/**
 * The callback format for inserts
 * @callback Collection~writeOpCallback
 * @param {MongoError} error An error instance representing the error during the execution.
 * @param {Collection~WriteOpResult} result The result object if the command was executed successfully.
 */

/**
 * @typedef {Object} Collection~insertWriteOpResult
 * @property {Number} insertedCount The total amount of documents inserted.
 * @property {object[]} ops All the documents inserted using insertOne/insertMany/replaceOne. Documents contain the _id field if forceServerObjectId == false for insertOne/insertMany
 * @property {Object.<Number, ObjectId>} insertedIds Map of the index of the inserted document to the id of the inserted document.
 * @property {object} connection The connection object used for the operation.
 * @property {object} result The raw command result object returned from MongoDB (content might vary by server version).
 * @property {Number} result.ok Is 1 if the command executed correctly.
 * @property {Number} result.n The total count of documents inserted.
 */

/**
 * @typedef {Object} Collection~insertOneWriteOpResult
 * @property {Number} insertedCount The total amount of documents inserted.
 * @property {object[]} ops All the documents inserted using insertOne/insertMany/replaceOne. Documents contain the _id field if forceServerObjectId == false for insertOne/insertMany
 * @property {ObjectId} insertedId The driver generated ObjectId for the insert operation.
 * @property {object} connection The connection object used for the operation.
 * @property {object} result The raw command result object returned from MongoDB (content might vary by server version).
 * @property {Number} result.ok Is 1 if the command executed correctly.
 * @property {Number} result.n The total count of documents inserted.
 */

/**
 * The callback format for inserts
 * @callback Collection~insertWriteOpCallback
 * @param {MongoError} error An error instance representing the error during the execution.
 * @param {Collection~insertWriteOpResult} result The result object if the command was executed successfully.
 */

/**
 * The callback format for inserts
 * @callback Collection~insertOneWriteOpCallback
 * @param {MongoError} error An error instance representing the error during the execution.
 * @param {Collection~insertOneWriteOpResult} result The result object if the command was executed successfully.
 */

/**
 * Inserts a single document or a an array of documents into MongoDB. If documents passed in do not contain the **_id** field,
 * one will be added to each of the documents missing it by the driver, mutating the document. This behavior
 * can be overridden by setting the **forceServerObjectId** flag.
 *
 * @method
 * @param {(object|object[])} docs Documents to insert.
 * @param {object} [options=null] Optional settings.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {boolean} [options.serializeFunctions=false] Serialize functions on any object.
 * @param {boolean} [options.forceServerObjectId=false] Force server to assign _id values instead of driver.
 * @param {boolean} [options.bypassDocumentValidation=false] Allow driver to bypass schema validation in MongoDB 3.2 or higher.
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~insertWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 * @deprecated Use insertOne, insertMany or bulkWrite
 */
Collection.prototype.insert = function(docs, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = options || { ordered: false };
  docs = !Array.isArray(docs) ? [docs] : docs;

  if (options.keepGoing === true) {
    options.ordered = false;
  }

  return this.insertMany(docs, options, callback);
};

define.classMethod('insert', { callback: true, promise: true });

/**
 * @typedef {Object} Collection~updateWriteOpResult
 * @property {Object} result The raw result returned from MongoDB, field will vary depending on server version.
 * @property {Number} result.ok Is 1 if the command executed correctly.
 * @property {Number} result.n The total count of documents scanned.
 * @property {Number} result.nModified The total count of documents modified.
 * @property {Object} connection The connection object used for the operation.
 * @property {Number} matchedCount The number of documents that matched the filter.
 * @property {Number} modifiedCount The number of documents that were modified.
 * @property {Number} upsertedCount The number of documents upserted.
 * @property {Object} upsertedId The upserted id.
 * @property {ObjectId} upsertedId._id The upserted _id returned from the server.
 */

/**
 * The callback format for inserts
 * @callback Collection~updateWriteOpCallback
 * @param {MongoError} error An error instance representing the error during the execution.
 * @param {Collection~updateWriteOpResult} result The result object if the command was executed successfully.
 */

/**
 * Update a single document on MongoDB
 * @method
 * @param {object} filter The Filter used to select the document to update
 * @param {object} update The update operations to be applied to the document
 * @param {object} [options=null] Optional settings.
 * @param {boolean} [options.upsert=false] Update operation is an upsert.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {boolean} [options.bypassDocumentValidation=false] Allow driver to bypass schema validation in MongoDB 3.2 or higher.
 * @param {Array} [options.arrayFilters=null] optional list of array filters referenced in filtered positional operators
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~updateWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 */
Collection.prototype.updateOne = function(filter, update, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = options || {};

  var err = checkForAtomicOperators(update);
  if (err) {
    if (typeof callback === 'function') return callback(err);
    return this.s.promiseLibrary.reject(err);
  }

  options = shallowClone(options);

  // Add ignoreUndfined
  if (this.s.options.ignoreUndefined) {
    options = shallowClone(options);
    options.ignoreUndefined = this.s.options.ignoreUndefined;
  }

  return executeOperation(this.s.topology, updateOne, [this, filter, update, options, callback]);
};

var checkForAtomicOperators = function(update) {
  var keys = Object.keys(update);

  // same errors as the server would give for update doc lacking atomic operators
  if (keys.length === 0) {
    return toError('The update operation document must contain at least one atomic operator.');
  }

  if (keys[0][0] !== '$') {
    return toError('the update operation document must contain atomic operators.');
  }
};

var updateOne = function(self, filter, update, options, callback) {
  // Set single document update
  options.multi = false;
  // Execute update
  updateDocuments(self, filter, update, options, function(err, r) {
    if (callback == null) return;
    if (err && callback) return callback(err);
    if (r == null) return callback(null, { result: { ok: 1 } });
    r.modifiedCount = r.result.nModified != null ? r.result.nModified : r.result.n;
    r.upsertedId =
      Array.isArray(r.result.upserted) && r.result.upserted.length > 0
        ? r.result.upserted[0]
        : null;
    r.upsertedCount =
      Array.isArray(r.result.upserted) && r.result.upserted.length ? r.result.upserted.length : 0;
    r.matchedCount =
      Array.isArray(r.result.upserted) && r.result.upserted.length > 0 ? 0 : r.result.n;
    if (callback) callback(null, r);
  });
};

define.classMethod('updateOne', { callback: true, promise: true });

/**
 * Replace a document on MongoDB
 * @method
 * @param {object} filter The Filter used to select the document to update
 * @param {object} doc The Document that replaces the matching document
 * @param {object} [options=null] Optional settings.
 * @param {boolean} [options.upsert=false] Update operation is an upsert.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {boolean} [options.bypassDocumentValidation=false] Allow driver to bypass schema validation in MongoDB 3.2 or higher.
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~updateWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 */
Collection.prototype.replaceOne = function(filter, doc, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = shallowClone(options);

  // Add ignoreUndfined
  if (this.s.options.ignoreUndefined) {
    options = shallowClone(options);
    options.ignoreUndefined = this.s.options.ignoreUndefined;
  }

  return executeOperation(this.s.topology, replaceOne, [this, filter, doc, options, callback]);
};

var replaceOne = function(self, filter, doc, options, callback) {
  // Set single document update
  options.multi = false;

  // Execute update
  updateDocuments(self, filter, doc, options, function(err, r) {
    if (callback == null) return;
    if (err && callback) return callback(err);
    if (r == null) return callback(null, { result: { ok: 1 } });

    r.modifiedCount = r.result.nModified != null ? r.result.nModified : r.result.n;
    r.upsertedId =
      Array.isArray(r.result.upserted) && r.result.upserted.length > 0
        ? r.result.upserted[0]
        : null;
    r.upsertedCount =
      Array.isArray(r.result.upserted) && r.result.upserted.length ? r.result.upserted.length : 0;
    r.matchedCount =
      Array.isArray(r.result.upserted) && r.result.upserted.length > 0 ? 0 : r.result.n;
    r.ops = [doc];
    if (callback) callback(null, r);
  });
};

define.classMethod('replaceOne', { callback: true, promise: true });

/**
 * Update multiple documents on MongoDB
 * @method
 * @param {object} filter The Filter used to select the documents to update
 * @param {object} update The update operations to be applied to the document
 * @param {object} [options=null] Optional settings.
 * @param {boolean} [options.upsert=false] Update operation is an upsert.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {Array} [options.arrayFilters=null] optional list of array filters referenced in filtered positional operators
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~updateWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 */
Collection.prototype.updateMany = function(filter, update, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = options || {};

  var err = checkForAtomicOperators(update);
  if (err) {
    if (typeof callback === 'function') return callback(err);
    return this.s.promiseLibrary.reject(err);
  }

  options = shallowClone(options);

  // Add ignoreUndfined
  if (this.s.options.ignoreUndefined) {
    options = shallowClone(options);
    options.ignoreUndefined = this.s.options.ignoreUndefined;
  }

  return executeOperation(this.s.topology, updateMany, [this, filter, update, options, callback]);
};

var updateMany = function(self, filter, update, options, callback) {
  // Set single document update
  options.multi = true;
  // Execute update
  updateDocuments(self, filter, update, options, function(err, r) {
    if (callback == null) return;
    if (err && callback) return callback(err);
    if (r == null) return callback(null, { result: { ok: 1 } });
    r.modifiedCount = r.result.nModified != null ? r.result.nModified : r.result.n;
    r.upsertedId =
      Array.isArray(r.result.upserted) && r.result.upserted.length > 0
        ? r.result.upserted[0]
        : null;
    r.upsertedCount =
      Array.isArray(r.result.upserted) && r.result.upserted.length ? r.result.upserted.length : 0;
    r.matchedCount =
      Array.isArray(r.result.upserted) && r.result.upserted.length > 0 ? 0 : r.result.n;
    if (callback) callback(null, r);
  });
};

define.classMethod('updateMany', { callback: true, promise: true });

var updateDocuments = function(self, selector, document, options, callback) {
  if ('function' === typeof options) (callback = options), (options = null);
  if (options == null) options = {};
  if (!('function' === typeof callback)) callback = null;

  // If we are not providing a selector or document throw
  if (selector == null || typeof selector !== 'object')
    return callback(toError('selector must be a valid JavaScript object'));
  if (document == null || typeof document !== 'object')
    return callback(toError('document must be a valid JavaScript object'));

  // Get the write concern options
  var finalOptions = writeConcern(shallowClone(options), self.s.db, self, options);

  // Do we return the actual result document
  // Either use override on the function, or go back to default on either the collection
  // level or db
  finalOptions['serializeFunctions'] = options['serializeFunctions'] || self.s.serializeFunctions;

  // Execute the operation
  var op = { q: selector, u: document };
  op.upsert = options.upsert !== void 0 ? !!options.upsert : false;
  op.multi = options.multi !== void 0 ? !!options.multi : false;

  if (finalOptions.arrayFilters) {
    op.arrayFilters = finalOptions.arrayFilters;
    delete finalOptions.arrayFilters;
  }

  // Have we specified collation
  decorateWithCollation(finalOptions, self, options);

  // Update options
  self.s.topology.update(self.s.namespace, [op], finalOptions, function(err, result) {
    if (callback == null) return;
    if (err) return handleCallback(callback, err, null);
    if (result == null) return handleCallback(callback, null, null);
    if (result.result.code) return handleCallback(callback, toError(result.result));
    if (result.result.writeErrors)
      return handleCallback(callback, toError(result.result.writeErrors[0]));
    // Return the results
    handleCallback(callback, null, result);
  });
};

/**
 * Updates documents.
 * @method
 * @param {object} selector The selector for the update operation.
 * @param {object} document The update document.
 * @param {object} [options=null] Optional settings.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {boolean} [options.upsert=false] Update operation is an upsert.
 * @param {boolean} [options.multi=false] Update one/all documents with operation.
 * @param {boolean} [options.bypassDocumentValidation=false] Allow driver to bypass schema validation in MongoDB 3.2 or higher.
 * @param {object} [options.collation=null] Specify collation (MongoDB 3.4 or higher) settings for update operation (see 3.4 documentation for available fields).
 * @param {Array} [options.arrayFilters=null] optional list of array filters referenced in filtered positional operators
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~writeOpCallback} [callback] The command result callback
 * @throws {MongoError}
 * @return {Promise} returns Promise if no callback passed
 * @deprecated use updateOne, updateMany or bulkWrite
 */
Collection.prototype.update = function(selector, document, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = options || {};

  // Add ignoreUndfined
  if (this.s.options.ignoreUndefined) {
    options = shallowClone(options);
    options.ignoreUndefined = this.s.options.ignoreUndefined;
  }

  return executeOperation(this.s.topology, updateDocuments, [
    this,
    selector,
    document,
    options,
    callback
  ]);
};

define.classMethod('update', { callback: true, promise: true });

/**
 * @typedef {Object} Collection~deleteWriteOpResult
 * @property {Object} result The raw result returned from MongoDB, field will vary depending on server version.
 * @property {Number} result.ok Is 1 if the command executed correctly.
 * @property {Number} result.n The total count of documents deleted.
 * @property {Object} connection The connection object used for the operation.
 * @property {Number} deletedCount The number of documents deleted.
 */

/**
 * The callback format for inserts
 * @callback Collection~deleteWriteOpCallback
 * @param {MongoError} error An error instance representing the error during the execution.
 * @param {Collection~deleteWriteOpResult} result The result object if the command was executed successfully.
 */

/**
 * Delete a document on MongoDB
 * @method
 * @param {object} filter The Filter used to select the document to remove
 * @param {object} [options=null] Optional settings.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~deleteWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 */
Collection.prototype.deleteOne = function(filter, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = shallowClone(options);

  // Add ignoreUndfined
  if (this.s.options.ignoreUndefined) {
    options = shallowClone(options);
    options.ignoreUndefined = this.s.options.ignoreUndefined;
  }

  return executeOperation(this.s.topology, deleteOne, [this, filter, options, callback]);
};

var deleteOne = function(self, filter, options, callback) {
  options.single = true;
  removeDocuments(self, filter, options, function(err, r) {
    if (callback == null) return;
    if (err && callback) return callback(err);
    if (r == null) return callback(null, { result: { ok: 1 } });
    r.deletedCount = r.result.n;
    if (callback) callback(null, r);
  });
};

define.classMethod('deleteOne', { callback: true, promise: true });

Collection.prototype.removeOne = Collection.prototype.deleteOne;

define.classMethod('removeOne', { callback: true, promise: true });

/**
 * Delete multiple documents on MongoDB
 * @method
 * @param {object} filter The Filter used to select the documents to remove
 * @param {object} [options=null] Optional settings.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~deleteWriteOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 */
Collection.prototype.deleteMany = function(filter, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});
  options = shallowClone(options);

  // Add ignoreUndfined
  if (this.s.options.ignoreUndefined) {
    options = shallowClone(options);
    options.ignoreUndefined = this.s.options.ignoreUndefined;
  }

  return executeOperation(this.s.topology, deleteMany, [this, filter, options, callback]);
};

var deleteMany = function(self, filter, options, callback) {
  options.single = false;

  removeDocuments(self, filter, options, function(err, r) {
    if (callback == null) return;
    if (err && callback) return callback(err);
    if (r == null) return callback(null, { result: { ok: 1 } });
    r.deletedCount = r.result.n;
    if (callback) callback(null, r);
  });
};

var removeDocuments = function(self, selector, options, callback) {
  if (typeof options === 'function') {
    (callback = options), (options = {});
  } else if (typeof selector === 'function') {
    callback = selector;
    options = {};
    selector = {};
  }

  // Create an empty options object if the provided one is null
  options = options || {};

  // Get the write concern options
  var finalOptions = writeConcern(shallowClone(options), self.s.db, self, options);

  // If selector is null set empty
  if (selector == null) selector = {};

  // Build the op
  var op = { q: selector, limit: 0 };
  if (options.single) op.limit = 1;

  // Have we specified collation
  decorateWithCollation(finalOptions, self, options);

  // Execute the remove
  self.s.topology.remove(self.s.namespace, [op], finalOptions, function(err, result) {
    if (callback == null) return;
    if (err) return handleCallback(callback, err, null);
    if (result == null) return handleCallback(callback, null, null);
    if (result.result.code) return handleCallback(callback, toError(result.result));
    if (result.result.writeErrors)
      return handleCallback(callback, toError(result.result.writeErrors[0]));
    // Return the results
    handleCallback(callback, null, result);
  });
};

define.classMethod('deleteMany', { callback: true, promise: true });

Collection.prototype.removeMany = Collection.prototype.deleteMany;

define.classMethod('removeMany', { callback: true, promise: true });

/**
 * Remove documents.
 * @method
 * @param {object} selector The selector for the update operation.
 * @param {object} [options=null] Optional settings.
 * @param {(number|string)} [options.w=null] The write concern.
 * @param {number} [options.wtimeout=null] The write concern timeout.
 * @param {boolean} [options.j=false] Specify a journal write concern.
 * @param {boolean} [options.single=false] Removes the first document found.
 * @param {ClientSession} [options.session] optional session to use for this operation
 * @param {Collection~writeOpCallback} [callback] The command result callback
 * @return {Promise} returns Promise if no callback passed
 * @deprecated use deleteOne, deleteMany or bulkWrite
 */
Collection.prototype.remove = function(selector, options, callback) {
  if (typeof options === 'function') (callback = options), (options = {});…