Mongoose

Mongoose.prototype.connect = function() {
  var conn = this.connection;
  if (rgxReplSet.test(arguments[0]) || checkReplicaSetInUri(arguments[0])) {
    return new MongooseThenable(this, conn.openSet.apply(conn, arguments));
  }

  return new MongooseThenable(this, conn.open.apply(conn, arguments));
};
Mongoose.prototype.connect.$hasSideEffects = true;

Mongoose.prototype.createConnection = function(uri, options) {
  var conn = new Connection(this);
  this.connections.push(conn);

  if (arguments.length) {
    if (rgxReplSet.test(arguments[0]) || checkReplicaSetInUri(arguments[0])) {
      conn.openSet.apply(conn, arguments);
    } else if (options && options.replset &&
        (options.replset.replicaSet || options.replset.rs_name)) {
      conn.openSet.apply(conn, arguments);
    } else {
      conn.open.apply(conn, arguments);
    }
  }

  return conn;
};
Mongoose.prototype.createConnection.$hasSideEffects = true;

Mongoose.prototype.disconnect = function(fn) {
  var error;
  this.connections.forEach(function(conn) {
    conn.close(function(err) {
      if (error) {
        return;
      }
      if (err) {
        error = err;
      }
    });
  });

  var Promise = PromiseProvider.get();
  return new MongooseThenable(this, new Promise.ES6(function(resolve, reject) {
    fn && fn(error);
    if (error) {
      reject(error);
      return;
    }
    resolve();
  }));
};
Mongoose.prototype.disconnect.$hasSideEffects = true;

Mongoose.prototype.model = function(name, schema, collection, skipInit) {
  if (typeof schema === 'string') {
    collection = schema;
    schema = false;
  }

  if (utils.isObject(schema) && !(schema.instanceOfSchema)) {
    schema = new Schema(schema);
  }

  if (typeof collection === 'boolean') {
    skipInit = collection;
    collection = null;
  }

  // handle internal options from connection.model()
  var options;
  if (skipInit && utils.isObject(skipInit)) {
    options = skipInit;
    skipInit = true;
  } else {
    options = {};
  }

  // look up schema for the collection.
  if (!this.modelSchemas[name]) {
    if (schema) {
      // cache it so we only apply plugins once
      this.modelSchemas[name] = schema;
      this._applyPlugins(schema);
    } else {
      throw new mongoose.Error.MissingSchemaError(name);
    }
  }

  var model;
  var sub;

  // connection.model() may be passing a different schema for
  // an existing model name. in this case don't read from cache.
  if (this.models[name] && options.cache !== false) {
    if (schema && schema.instanceOfSchema && schema !== this.models[name].schema) {
      throw new mongoose.Error.OverwriteModelError(name);
    }

    if (collection) {
      // subclass current model with alternate collection
      model = this.models[name];
      schema = model.prototype.schema;
      sub = model.__subclass(this.connection, schema, collection);
      // do not cache the sub model
      return sub;
    }

    return this.models[name];
  }

  // ensure a schema exists
  if (!schema) {
    schema = this.modelSchemas[name];
    if (!schema) {
      throw new mongoose.Error.MissingSchemaError(name);
    }
  }

  // Apply relevant "global" options to the schema
  if (!('pluralization' in schema.options)) schema.options.pluralization = this.options.pluralization;


  if (!collection) {
    collection = schema.get('collection') || format(name, schema.options);
  }

  var connection = options.connection || this.connection;
  model = Model.compile(name, schema, collection, connection, this);

  if (!skipInit) {
    model.init();
  }

  if (options.cache === false) {
    return model;
  }

  this.models[name] = model;
  return this.models[name];
};
Mongoose.prototype.model.$hasSideEffects = true;

Mongoose.prototype.modelNames = function() {
  var names = Object.keys(this.models);
  return names;
};
Mongoose.prototype.modelNames.$hasSideEffects = true;

function Mongoose() {
  this.connections = [];
  this.plugins = [];
  this.models = {};
  this.modelSchemas = {};
  // default global options
  this.options = {
    pluralization: true
  };
  var conn = this.createConnection(); // default connection
  conn.models = this.models;
}

Mongoose.prototype.plugin = function(fn, opts) {
  this.plugins.push([fn, opts]);
  return this;
};
Mongoose.prototype.plugin.$hasSideEffects = true;

Mongoose.prototype.set = function(key, value) {
  if (arguments.length === 1) {
    return this.options[key];
  }

  this.options[key] = value;
  return this;
};
Mongoose.prototype.set.$hasSideEffects = true;

Mongoose.prototype.STATES = STATES;

QueryStream.prototype.destroy = function(err) {
  if (this._destroyed) {
    return;
  }
  this._destroyed = true;
  this._running = false;
  this.readable = false;

  if (this._cursor) {
    this._cursor.close();
  }

  if (err) {
    this.emit('error', err);
  }

  this.emit('close');
};

QueryStream.prototype.pause = function() {
  this.paused = true;
};

function QueryStream(query, options) {
  Stream.call(this);

  this.query = query;
  this.readable = true;
  this.paused = false;
  this._cursor = null;
  this._destroyed = null;
  this._fields = null;
  this._buffer = null;
  this._inline = T_INIT;
  this._running = false;
  this._transform = options && typeof options.transform === 'function'
      ? options.transform
      : K;

  // give time to hook up events
  var _this = this;
  process.nextTick(function() {
    _this._init();
  });
}

QueryStream.prototype.resume = function() {
  this.paused = false;

  if (!this._cursor) {
    // cannot start if not initialized
    return;
  }

  // are we within the trampoline?
  if (T_INIT === this._inline) {
    return;
  }

  if (!this._running) {
    // outside QueryStream control, need manual restart
    return this._next();
  }
};

function Connection(base) {
  this.base = base;
  this.collections = {};
  this.models = {};
  this.config = {autoIndex: true};
  this.replica = false;
  this.hosts = null;
  this.host = null;
  this.port = null;
  this.user = null;
  this.pass = null;
  this.name = null;
  this.options = null;
  this.otherDbs = [];
  this._readyState = STATES.disconnected;
  this._closeCalled = false;
  this._hasOpened = false;
}

Connection.prototype.open = function(host, database, port, options, callback) {
  var parsed;

  if (typeof database === 'string') {
    switch (arguments.length) {
      case 2:
        port = 27017;
        break;
      case 3:
        switch (typeof port) {
          case 'function':
            callback = port;
            port = 27017;
            break;
          case 'object':
            options = port;
            port = 27017;
            break;
        }
        break;
      case 4:
        if (typeof options === 'function') {
          callback = options;
          options = {};
        }
    }
  } else {
    switch (typeof database) {
      case 'function':
        callback = database;
        database = undefined;
        break;
      case 'object':
        options = database;
        database = undefined;
        callback = port;
        break;
    }

    if (!rgxProtocol.test(host)) {
      host = 'mongodb://' + host;
    }

    try {
      parsed = muri(host);
    } catch (err) {
      this.error(err, callback);
      return this;
    }

    database = parsed.db;
    host = parsed.hosts[0].host || parsed.hosts[0].ipc;
    port = parsed.hosts[0].port || 27017;
  }

  this.options = this.parseOptions(options, parsed && parsed.options);

  // make sure we can open
  if (STATES.disconnected !== this.readyState) {
    var err = new Error('Trying to open unclosed connection.');
    err.state = this.readyState;
    this.error(err, callback);
    return this;
  }

  if (!host) {
    this.error(new Error('Missing hostname.'), callback);
    return this;
  }

  if (!database) {
    this.error(new Error('Missing database name.'), callback);
    return this;
  }

  // authentication
  if (this.optionsProvideAuthenticationData(options)) {
    this.user = options.user;
    this.pass = options.pass;
  } else if (parsed && parsed.auth) {
    this.user = parsed.auth.user;
    this.pass = parsed.auth.pass;

    // Check hostname for user/pass
  } else if (/@/.test(host) && /:/.test(host.split('@')[0])) {
    host = host.split('@');
    var auth = host.shift().split(':');
    host = host.pop();
    this.user = auth[0];
    this.pass = auth[1];
  } else {
    this.user = this.pass = undefined;
  }

  // global configuration options
  if (options && options.config) {
    this.config.autoIndex = options.config.autoIndex !== false;
  }

  this.name = database;
  this.host = host;
  this.port = port;

  var _this = this;
  var Promise = PromiseProvider.get();
  return new Promise.ES6(function(resolve, reject) {
    _this._open(!!callback, function(error) {
      callback && callback(error);
      if (error) {
        reject(error);
        return;
      }
      resolve();
    });
  });
};

Connection.prototype.openSet = function(uris, database, options, callback) {
  if (!rgxProtocol.test(uris)) {
    uris = 'mongodb://' + uris;
  }

  switch (arguments.length) {
    case 3:
      switch (typeof database) {
        case 'string':
          this.name = database;
          break;
        case 'object':
          callback = options;
          options = database;
          database = null;
          break;
      }

      if (typeof options === 'function') {
        callback = options;
        options = {};
      }
      break;
    case 2:
      switch (typeof database) {
        case 'string':
          this.name = database;
          break;
        case 'function':
          callback = database;
          database = null;
          break;
        case 'object':
          options = database;
          database = null;
          break;
      }
  }

  var parsed;
  try {
    parsed = muri(uris);
  } catch (err) {
    this.error(err, callback);
    return this;
  }

  if (!this.name) {
    this.name = parsed.db;
  }

  this.hosts = parsed.hosts;
  this.options = this.parseOptions(options, parsed && parsed.options);
  this.replica = true;

  if (!this.name) {
    this.error(new Error('No database name provided for replica set'), callback);
    return this;
  }

  // authentication
  if (this.optionsProvideAuthenticationData(options)) {
    this.user = options.user;
    this.pass = options.pass;
  } else if (parsed && parsed.auth) {
    this.user = parsed.auth.user;
    this.pass = parsed.auth.pass;
  } else {
    this.user = this.pass = undefined;
  }

  // global configuration options
  if (options && options.config) {
    this.config.autoIndex = options.config.autoIndex !== false;
  }

  var _this = this;
  var Promise = PromiseProvider.get();
  return new Promise.ES6(function(resolve, reject) {
    _this._open(!!callback, function(error) {
      callback && callback(error);
      if (error) {
        reject(error);
        return;
      }
      resolve();
    });
  });
};

Connection.prototype.close = function(callback) {
  var _this = this;
  var Promise = PromiseProvider.get();
  return new Promise.ES6(function(resolve, reject) {
    _this._close(function(error) {
      callback && callback(error);
      if (error) {
        reject(error);
        return;
      }
      resolve();
    });
  });
};

Connection.prototype.collection = function(name, options) {
  if (!(name in this.collections)) {
    this.collections[name] = new Collection(name, this, options);
  }
  return this.collections[name];
};

Connection.prototype.model = function(name, schema, collection) {
  // collection name discovery
  if (typeof schema === 'string') {
    collection = schema;
    schema = false;
  }

  if (utils.isObject(schema) && !schema.instanceOfSchema) {
    schema = new Schema(schema);
  }

  if (this.models[name] && !collection) {
    // model exists but we are not subclassing with custom collection
    if (schema && schema.instanceOfSchema && schema !== this.models[name].schema) {
      throw new MongooseError.OverwriteModelError(name);
    }
    return this.models[name];
  }

  var opts = {cache: false, connection: this};
  var model;

  if (schema && schema.instanceOfSchema) {
    // compile a model
    model = this.base.model(name, schema, collection, opts);

    // only the first model with this name is cached to allow
    // for one-offs with custom collection names etc.
    if (!this.models[name]) {
      this.models[name] = model;
    }

    model.init();
    return model;
  }

  if (this.models[name] && collection) {
    // subclassing current model with alternate collection
    model = this.models[name];
    schema = model.prototype.schema;
    var sub = model.__subclass(this, schema, collection);
    // do not cache the sub model
    return sub;
  }

  // lookup model in mongoose module
  model = this.base.models[name];

  if (!model) {
    throw new MongooseError.MissingSchemaError(name);
  }

  if (this === model.prototype.db
      && (!collection || collection === model.collection.name)) {
    // model already uses this connection.

    // only the first model with this name is cached to allow
    // for one-offs with custom collection names etc.
    if (!this.models[name]) {
      this.models[name] = model;
    }

    return model;
  }
  this.models[name] = model.__subclass(this, schema, collection);
  return this.models[name];
};

Connection.prototype.modelNames = function() {
  return Object.keys(this.models);
};

NativeConnection.prototype.useDb = function(name) {
  // we have to manually copy all of the attributes...
  var newConn = new this.constructor();
  newConn.name = name;
  newConn.base = this.base;
  newConn.collections = {};
  newConn.models = {};
  newConn.replica = this.replica;
  newConn.hosts = this.hosts;
  newConn.host = this.host;
  newConn.port = this.port;
  newConn.user = this.user;
  newConn.pass = this.pass;
  newConn.options = this.options;
  newConn._readyState = this._readyState;
  newConn._closeCalled = this._closeCalled;
  newConn._hasOpened = this._hasOpened;
  newConn._listening = false;

  // First, when we create another db object, we are not guaranteed to have a
  // db object to work with. So, in the case where we have a db object and it
  // is connected, we can just proceed with setting everything up. However, if
  // we do not have a db or the state is not connected, then we need to wait on
  // the 'open' event of the connection before doing the rest of the setup
  // the 'connected' event is the first time we'll have access to the db object

  var _this = this;

  if (this.db && this._readyState === STATES.connected) {
    wireup();
  } else {
    this.once('connected', wireup);
  }

  function wireup() {
    newConn.db = _this.db.db(name);
    newConn.onOpen();
    // setup the events appropriately
    listen(newConn);
  }

  newConn.name = name;

  // push onto the otherDbs stack, this is used when state changes
  this.otherDbs.push(newConn);
  newConn.otherDbs.push(this);

  return newConn;
};

ValidationError.prototype.toString = function() {
  var ret = this.name + ': ';
  var msgs = [];

  Object.keys(this.errors).forEach(function(key) {
    if (this === this.errors[key]) {
      return;
    }
    msgs.push(String(this.errors[key]));
  }, this);

  return ret + msgs.join(', ');
};

function MongooseError(msg) {
  Error.call(this);
  if (Error.captureStackTrace) {
    Error.captureStackTrace(this);
  } else {
    this.stack = new Error().stack;
  }
  this.message = msg;
  this.name = 'MongooseError';
}

VirtualType.prototype.applyGetters = function(value, scope) {
  var v = value;
  for (var l = this.getters.length - 1; l >= 0; l--) {
    v = this.getters[l].call(scope, v, this);
  }
  return v;
};

VirtualType.prototype.applySetters = function(value, scope) {
  var v = value;
  for (var l = this.setters.length - 1; l >= 0; l--) {
    v = this.setters[l].call(scope, v, this);
  }
  return v;
};

VirtualType.prototype.get = function(fn) {
  this.getters.push(fn);
  return this;
};

VirtualType.prototype.set = function(fn) {
  this.setters.push(fn);
  return this;
};

function VirtualType(options, name) {
  this.path = name;
  this.getters = [];
  this.setters = [];
  this.options = options || {};
}

Schema.prototype.add = function add(obj, prefix) {
  prefix = prefix || '';
  var keys = Object.keys(obj);

  for (var i = 0; i < keys.length; ++i) {
    var key = keys[i];

    if (obj[key] == null) {
      throw new TypeError('Invalid value for schema path `' + prefix + key + '`');
    }

    if (Array.isArray(obj[key]) && obj[key].length === 1 && obj[key][0] == null) {
      throw new TypeError('Invalid value for schema Array path `' + prefix + key + '`');
    }

    if (utils.isObject(obj[key]) &&
        (!obj[key].constructor || utils.getFunctionName(obj[key].constructor) === 'Object') &&
        (!obj[key][this.options.typeKey] || (this.options.typeKey === 'type' && obj[key].type.type))) {
      if (Object.keys(obj[key]).length) {
        // nested object { last: { name: String }}
        this.nested[prefix + key] = true;
        this.add(obj[key], prefix + key + '.');
      } else {
        this.path(prefix + key, obj[key]); // mixed type
      }
    } else {
      this.path(prefix + key, obj[key]);
    }
  }
};

Schema.prototype.eachPath = function(fn) {
  var keys = Object.keys(this.paths),
      len = keys.length;

  for (var i = 0; i < len; ++i) {
    fn(keys[i], this.paths[keys[i]]);
  }

  return this;
};

Schema.prototype.get = function(key) {
  return this.options[key];
};

Schema.prototype.index = function(fields, options) {
  options || (options = {});

  if (options.expires) {
    utils.expires(options);
  }

  this._indexes.push([fields, options]);
  return this;
};

Schema.prototype.indexes = function() {
  'use strict';

  var indexes = [];
  var seenPrefix = {};

  var collectIndexes = function(schema, prefix) {
    if (seenPrefix[prefix]) {
      return;
    }
    seenPrefix[prefix] = true;

    prefix = prefix || '';
    var key, path, index, field, isObject, options, type;
    var keys = Object.keys(schema.paths);

    for (var i = 0; i < keys.length; ++i) {
      key = keys[i];
      path = schema.paths[key];

      if ((path instanceof MongooseTypes.DocumentArray) || path.$isSingleNested) {
        collectIndexes(path.schema, key + '.');
      } else {
        index = path._index;

        if (index !== false && index !== null && index !== undefined) {
          field = {};
          isObject = utils.isObject(index);
          options = isObject ? index : {};
          type = typeof index === 'string' ? index :
              isObject ? index.type :
                  false;

          if (type && ~Schema.indexTypes.indexOf(type)) {
            field[prefix + key] = type;
          } else if (options.text) {
            field[prefix + key] = 'text';
            delete options.text;
          } else {
            field[prefix + key] = 1;
          }

          delete options.type;
          if (!('background' in options)) {
            options.background = true;
          }

          indexes.push([field, options]);
        }
      }
    }

    if (prefix) {
      fixSubIndexPaths(schema, prefix);
    } else {
      schema._indexes.forEach(function(index) {
        if (!('background' in index[1])) {
          index[1].background = true;
        }
      });
      indexes = indexes.concat(schema._indexes);
    }
  };

  collectIndexes(this);
  return indexes;

Schema.prototype.method = function(name, fn) {
  if (typeof name !== 'string') {
    for (var i in name) {
      this.methods[i] = name[i];
    }
  } else {
    this.methods[name] = fn;
  }
  return this;
};

Schema.prototype.path = function(path, obj) {
  if (obj === undefined) {
    if (this.paths[path]) {
      return this.paths[path];
    }
    if (this.subpaths[path]) {
      return this.subpaths[path];
    }
    if (this.singleNestedPaths[path]) {
      return this.singleNestedPaths[path];
    }

    // subpaths?
    return /\.\d+\.?.*$/.test(path)
        ? getPositionalPath(this, path)
        : undefined;
  }

  // some path names conflict with document methods
  if (reserved[path]) {
    throw new Error('`' + path + '` may not be used as a schema pathname');
  }

  if (warnings[path]) {
    console.log('WARN: ' + warnings[path]);
  }

  // update the tree
  var subpaths = path.split(/\./),
      last = subpaths.pop(),
      branch = this.tree;

  subpaths.forEach(function(sub, i) {
    if (!branch[sub]) {
      branch[sub] = {};
    }
    if (typeof branch[sub] !== 'object') {
      var msg = 'Cannot set nested path `' + path + '`. '
          + 'Parent path `'
          + subpaths.slice(0, i).concat([sub]).join('.')
          + '` already set to type ' + branch[sub].name
          + '.';
      throw new Error(msg);
    }
    branch = branch[sub];
  });

  branch[last] = utils.clone(obj);

  this.paths[path] = Schema.interpretAsType(path, obj, this.options);
  if (this.paths[path].$isSingleNested) {
    for (var key in this.paths[path].schema.paths) {
      this.singleNestedPaths[path + '.' + key] =
          this.paths[path].schema.paths[key];
    }
    for (key in this.paths[path].schema.singleNestedPaths) {
      this.singleNestedPaths[path + '.' + key] =
          this.paths[path].schema.singleNestedPaths[key];
    }
  }
  return this;
};

Schema.prototype.pathType = function(path) {
  if (path in this.paths) {
    return 'real';
  }
  if (path in this.virtuals) {
    return 'virtual';
  }
  if (path in this.nested) {
    return 'nested';
  }
  if (path in this.subpaths) {
    return 'real';
  }
  if (path in this.singleNestedPaths) {
    return 'real';
  }

  if (/\.\d+\.|\.\d+$/.test(path)) {
    return getPositionalPathType(this, path);
  }
  return 'adhocOrUndefined';
};

Schema.prototype.plugin = function(fn, opts) {
  fn(this, opts);
  return this;
};

Schema.prototype.post = function(method, fn) {
  if (IS_QUERY_HOOK[method]) {
    this.s.hooks.post.apply(this.s.hooks, arguments);
    return this;
  }
  // assuming that all callbacks with arity < 2 are synchronous post hooks
  if (fn.length < 2) {
    return this.queue('on', [arguments[0], function(doc) {
      return fn.call(doc, doc);
    }]);
  }

  return this.queue('post', [arguments[0], function(next) {
    // wrap original function so that the callback goes last,
    // for compatibility with old code that is using synchronous post hooks
    var _this = this;
    var args = Array.prototype.slice.call(arguments, 1);
    fn.call(this, this, function(err) {
      return next.apply(_this, [err].concat(args));
    });
  }]);
};

Schema.prototype.pre = function() {
  var name = arguments[0];
  if (IS_QUERY_HOOK[name]) {
    this.s.hooks.pre.apply(this.s.hooks, arguments);
    return this;
  }
  return this.queue('pre', arguments);
};

Schema.prototype.queue = function(name, args) {
  this.callQueue.push([name, args]);
  return this;
};

Schema.prototype.remove = function(path) {
  if (typeof path === 'string') {
    path = [path];
  }
  if (Array.isArray(path)) {
    path.forEach(function(name) {
      if (this.path(name)) {
        delete this.paths[name];

        var pieces = name.split('.');
        var last = pieces.pop();
        var branch = this.tree;
        for (var i = 0; i < pieces.length; ++i) {
          branch = branch[pieces[i]];
        }
        delete branch[last];
      }
    }, this);
  }
};

Schema.prototype.requiredPaths = function requiredPaths(invalidate) {
  if (this._requiredpaths && !invalidate) {
    return this._requiredpaths;
  }

  var paths = Object.keys(this.paths),
      i = paths.length,
      ret = [];

  while (i--) {
    var path = paths[i];
    if (this.paths[path].isRequired) {
      ret.push(path);
    }
  }
  this._requiredpaths = ret;
  return this._requiredpaths;
};

function Schema(obj, options) {
  if (!(this instanceof Schema)) {
    return new Schema(obj, options);
  }

  this.paths = {};
  this.subpaths = {};
  this.virtuals = {};
  this.singleNestedPaths = {};
  this.nested = {};
  this.inherits = {};
  this.callQueue = [];
  this._indexes = [];
  this.methods = {};
  this.statics = {};
  this.tree = {};
  this._requiredpaths = undefined;
  this.discriminatorMapping = undefined;
  this._indexedpaths = undefined;

  this.s = {
    hooks: new Kareem(),
    queryHooks: IS_QUERY_HOOK
  };

  this.options = this.defaultOptions(options);

  // build paths
  if (obj) {
    this.add(obj);
  }

  // check if _id's value is a subdocument (gh-2276)
  var _idSubDoc = obj && obj._id && utils.isObject(obj._id);

  // ensure the documents get an auto _id unless disabled
  var auto_id = !this.paths['_id'] &&
      (!this.options.noId && this.options._id) && !_idSubDoc;

  if (auto_id) {
    obj = {_id: {auto: true}};
    obj._id[this.options.typeKey] = Schema.ObjectId;
    this.add(obj);
  }

  // ensure the documents receive an id getter unless disabled
  var autoid = !this.paths['id'] &&
      (!this.options.noVirtualId && this.options.id);
  if (autoid) {
    this.virtual('id').get(idGetter);
  }

  for (var i = 0; i < this._defaultMiddleware.length; ++i) {
    var m = this._defaultMiddleware[i];
    this[m.kind](m.hook, !!m.isAsync, m.fn);
  }

  if (this.options.timestamps) {
    this.setupTimestamp(this.options.timestamps);
  }
}

Schema.prototype.set = function(key, value, _tags) {
  if (arguments.length === 1) {
    return this.options[key];
  }

  switch (key) {
    case 'read':
      this.options[key] = readPref(value, _tags);
      break;
    case 'safe':
      this.options[key] = value === false
          ? {w: 0}
          : value;
      break;
    case 'timestamps':
      this.setupTimestamp(value);
      this.options[key] = value;
      break;
    default:
      this.options[key] = value;
  }

  return this;
};

Schema.prototype.static = function(name, fn) {
  if (typeof name !== 'string') {
    for (var i in name) {
      this.statics[i] = name[i];
    }
  } else {
    this.statics[name] = fn;
  }
  return this;
};

Schema.prototype.virtual = function(name, options) {
  var virtuals = this.virtuals;
  var parts = name.split('.');
  virtuals[name] = parts.reduce(function(mem, part, i) {
    mem[part] || (mem[part] = (i === parts.length - 1)
        ? new VirtualType(options, name)
        : {});
    return mem[part];
  }, this.tree);
  return virtuals[name];
};

Schema.prototype.virtualpath = function(name) {
  return this.virtuals[name];
};

var warnings = {};
warnings.increment = '`increment` should not be used as a schema path name ' +
    'unless you have disabled versioning.';

Document.prototype.depopulate = function(path) {
  var populatedIds = this.populated(path);
  if (!populatedIds) {
    return;
  }
  delete this.$__.populated[path];
  this.set(path, populatedIds);
};

Document.prototype.equals = function(doc) {
  var tid = this.get('_id');
  var docid = doc.get ? doc.get('_id') : doc;
  if (!tid && !docid) {
    return deepEqual(this, doc);
  }
  return tid && tid.equals
      ? tid.equals(docid)
      : tid === docid;
};

Document.prototype.execPopulate = function() {
  var Promise = PromiseProvider.get();
  var _this = this;
  return new Promise.ES6(function(resolve, reject) {
    _this.populate(function(error, res) {
      if (error) {
        reject(error);
      } else {
        resolve(res);
      }
    });
  });
};

Document.prototype.get = function(path, type) {
  var adhoc;
  if (type) {
    adhoc = Schema.interpretAsType(path, type, this.schema.options);
  }

  var schema = this.$__path(path) || this.schema.virtualpath(path),
      pieces = path.split('.'),
      obj = this._doc;

  for (var i = 0, l = pieces.length; i < l; i++) {
    obj = obj === null || obj === void 0
        ? undefined
        : obj[pieces[i]];
  }

  if (adhoc) {
    obj = adhoc.cast(obj);
  }

  // Check if this path is populated - don't apply getters if it is,
  // because otherwise its a nested object. See gh-3357
  if (schema && !this.populated(path)) {
    obj = schema.applyGetters(obj, this);
  }

  return obj;
};

Document.prototype.init = function(doc, opts, fn) {
  // do not prefix this method with $__ since its
  // used by public hooks

  if (typeof opts === 'function') {
    fn = opts;
    opts = null;
  }

  this.isNew = false;

  // handle docs with populated paths
  // If doc._id is not null or undefined
  if (doc._id !== null && doc._id !== undefined &&
    opts && opts.populated && opts.populated.length) {
    var id = String(doc._id);
    for (var i = 0; i < opts.populated.length; ++i) {
      var item = opts.populated[i];
      this.populated(item.path, item._docs[id], item);
    }
  }

  init(this, doc, this._doc);
  this.$__storeShard();

  this.emit('init', this);
  if (fn) {
    fn(null);
  }
  return this;
};

Document.prototype.inspect = function(options) {
  var isPOJO = options &&
    utils.getFunctionName(options.constructor) === 'Object';
  var opts;
  if (isPOJO) {
    opts = options;
  } else if (this.schema.options.toObject) {
    opts = clone(this.schema.options.toObject);
  } else {
    opts = {};
  }
  opts.minimize = false;
  opts.retainKeyOrder = true;
  return this.toObject(opts);
};

Document.prototype.invalidate = function(path, err, val, kind) {
  if (!this.$__.validationError) {
    this.$__.validationError = new ValidationError(this);
  }

  if (this.$__.validationError.errors[path]) {
    return;
  }

  if (!err || typeof err === 'string') {
    err = new ValidatorError({
      path: path,
      message: err,
      type: kind || 'user defined',
      value: val
    });
  }

  if (this.$__.validationError === err) {
    return this.$__.validationError;
  }

  this.$__.validationError.errors[path] = err;
  return this.$__.validationError;
};

Document.prototype.isDirectModified = function(path) {
  return (path in this.$__.activePaths.states.modify);
};

Document.prototype.isInit = function(path) {
  return (path in this.$__.activePaths.states.init);
};

Document.prototype.isModified = function(path) {
  return path
      ? !!~this.modifiedPaths().indexOf(path)
      : this.$__.activePaths.some('modify');
};

Document.prototype.isSelected = function isSelected(path) {
  if (this.$__.selected) {
    if (path === '_id') {
      return this.$__.selected._id !== 0;
    }

    var paths = Object.keys(this.$__.selected),
        i = paths.length,
        inclusive = false,
        cur;

    if (i === 1 && paths[0] === '_id') {
      // only _id was selected.
      return this.$__.selected._id === 0;
    }

    while (i--) {
      cur = paths[i];
      if (cur === '_id') {
        continue;
      }
      inclusive = !!this.$__.selected[cur];
      break;
    }

    if (path in this.$__.selected) {
      return inclusive;
    }

    i = paths.length;
    var pathDot = path + '.';

    while (i--) {
      cur = paths[i];
      if (cur === '_id') {
        continue;
      }

      if (cur.indexOf(pathDot) === 0) {
        return inclusive;
      }

      if (pathDot.indexOf(cur + '.') === 0) {
        return inclusive;
      }
    }

    return !inclusive;
  }

  return true;
};

Document.prototype.markModified = function(path) {
  this.$__.activePaths.modify(path);
};

Document.prototype.modifiedPaths = function() {
  var directModifiedPaths = Object.keys(this.$__.activePaths.states.modify);

  return directModifiedPaths.reduce(function(list, path) {
    var parts = path.split('.');
    return list.concat(parts.reduce(function(chains, part, i) {
      return chains.concat(parts.slice(0, i).concat(part).join('.'));
    }, []));
  }, []);
};

Document.prototype.populate = function populate() {
  if (arguments.length === 0) {
    return this;
  }

  var pop = this.$__.populate || (this.$__.populate = {});
  var args = utils.args(arguments);
  var fn;

  if (typeof args[args.length - 1] === 'function') {
    fn = args.pop();
  }

  // allow `doc.populate(callback)`
  if (args.length) {
    // use hash to remove duplicate paths
    var res = utils.populate.apply(null, args);
    for (var i = 0; i < res.length; ++i) {
      pop[res[i].path] = res[i];
    }
  }

  if (fn) {
    var paths = utils.object.vals(pop);
    this.$__.populate = undefined;
    paths.__noPromise = true;
    this.constructor.populate(this, paths, fn);
  }

  return this;
};

Document.prototype.populated = function(path, val, options) {
  // val and options are internal

  if (val === null || val === void 0) {
    if (!this.$__.populated) {
      return undefined;
    }
    var v = this.$__.populated[path];
    if (v) {
      return v.value;
    }
    return undefined;
  }

  // internal

  if (val === true) {
    if (!this.$__.populated) {
      return undefined;
    }
    return this.$__.populated[path];
  }

  this.$__.populated || (this.$__.populated = {});
  this.$__.populated[path] = {value: val, options: options};
  return val;
};

Document.prototype.set = function(path, val, type, options) {
  if (type && utils.getFunctionName(type.constructor) === 'Object') {
    options = type;
    type = undefined;
  }

  var merge = options && options.merge,
      adhoc = type && type !== true,
      constructing = type === true,
      adhocs;

  var strict = options && 'strict' in options
      ? options.strict
      : this.$__.strictMode;

  if (adhoc) {
    adhocs = this.$__.adhocPaths || (this.$__.adhocPaths = {});
    adhocs[path] = Schema.interpretAsType(path, type, this.schema.options);
  }

  if (typeof path !== 'string') {
    // new Document({ key: val })

    if (path === null || path === void 0) {
      var _ = path;
      path = val;
      val = _;
    } else {
      var prefix = val
          ? val + '.'
          : '';

      if (path instanceof Document) {
        if (path.$__isNested) {
          path = path.toObject();
        } else {
          path = path._doc;
        }
      }

      var keys = Object.keys(path),
          i = keys.length,
          pathtype,
          key;

      while (i--) {
        key = keys[i];
        var pathName = prefix + key;
        pathtype = this.schema.pathType(pathName);

        if (path[key] !== null
            && path[key] !== void 0
              // need to know if plain object - no Buffer, ObjectId, ref, etc
            && utils.isObject(path[key])
            && (!path[key].constructor || utils.getFunctionName(path[key].constructor) === 'Object')
            && pathtype !== 'virtual'
            && pathtype !== 'real'
            && !(this.$__path(pathName) instanceof MixedSchema)
            && !(this.schema.paths[pathName] &&
            this.schema.paths[pathName].options &&
            this.schema.paths[pathName].options.ref)) {
          this.set(path[key], prefix + key, constructing);
        } else if (strict) {
          // Don't overwrite defaults with undefined keys (gh-3981)
          if (constructing && path[key] === void 0 &&
              this.get(key) !== void 0) {
            continue;
          }

          if (pathtype === 'real' || pathtype === 'virtual') {
            // Check for setting single embedded schema to document (gh-3535)
            if (this.schema.paths[pathName] &&
                this.schema.paths[pathName].$isSingleNested &&
                path[key] instanceof Document) {
              path[key] = path[key].toObject({virtuals: false});
            }
            this.set(prefix + key, path[key], constructing);
          } else if (pathtype === 'nested' && path[key] instanceof Document) {
            this.set(prefix + key,
                path[key].toObject({virtuals: false}), constructing);
          } else if (strict === 'throw') {
            if (pathtype === 'nested') {
              throw new ObjectExpectedError(key, path[key]);
            } else {
              throw new StrictModeError(key);
            }
          }
        } else if (path[key] !== void 0) {
          this.set(prefix + key, path[key], constructing);
        }
      }

      return this;
    }
  }

  // ensure _strict is honored for obj props
  // docschema = new Schema({ path: { nest: 'string' }})
  // doc.set('path', obj);
  var pathType = this.schema.pathType(path);
  if (pathType === 'nested' && val) {
    if (utils.isObject(val) &&
        (!val.constructor || utils.getFunctionName(val.constructor) === 'Object')) {
      if (!merge) {
        this.setValue(path, null);
      }
      this.set(val, path, constructing);
      return this;
    }
    this.invalidate(path, new MongooseError.CastError('Object', val, path));
    return this;
  }

  var schema;
  var parts = path.split('.');

  if (pathType === 'adhocOrUndefined' && strict) {
    // check for roots that are Mixed types
    var mixed;

    for (i = 0; i < parts.length; ++i) {
      var subpath = parts.slice(0, i + 1).join('.');
      schema = this.schema.path(subpath);
      if (schema instanceof MixedSchema) {
        // allow changes to sub paths of mixed types
        mixed = true;
        break;
      }
    }

    if (!mixed) {
      if (strict === 'throw') {
        throw new StrictModeError(path);
      }
      return this;
    }
  } else if (pathType === 'virtual') {
    schema = this.schema.virtualpath(path);
    schema.applySetters(val, this);
    return this;
  } else {
    schema = this.$__path(path);
  }

  var pathToMark;

  // When using the $set operator the path to the field must already exist.
  // Else mongodb throws: "LEFT_SUBFIELD only supports Object"

  if (parts.length <= 1) {
    pathToMark = path;
  } else {
    for (i = 0; i < parts.length; ++i) {
      subpath = parts.slice(0, i + 1).join('.');
      if (this.isDirectModified(subpath) // earlier prefixes that are already
            // marked as dirty have precedence
          || this.get(subpath) === null) {
        pathToMark = subpath;
        break;
      }
    }

    if (!pathToMark) {
      pathToMark = path;
    }
  }

  // if this doc is being constructed we should not trigger getters
  var priorVal = constructing
      ? undefined
      : this.getValue(path);

  if (!schema) {
    this.$__set(pathToMark, path, constructing, parts, schema, val, priorVal);
    return this;
  }

  var shouldSet = true;
  try {
    // If the user is trying to set a ref path to a document with
    // the correct model name, treat it as populated
    var didPopulate = false;
    if (schema.options &&
        schema.options.ref &&
        val instanceof Document &&
        schema.options.ref === val.constructor.modelName) {
      if (this.ownerDocument) {
        this.ownerDocument().populated(this.$__fullPath(path),
          val._id, {model: val.constructor});
      } else {
        this.populated(path, val._id, {model: val.constructor});
      }
      didPopulate = true;
    }

    var popOpts;
    if (schema.options &&
        Array.isArray(schema.options.type) &&
        schema.options.type.length &&
        schema.options.type[0].ref &&
        Array.isArray(val) &&
        val.length > 0 &&
        val[0] instanceof Document &&
        val[0].constructor.modelName &&
        schema.options.type[0].ref === val[0].constructor.modelName) {
      if (this.ownerDocument) {
        popOpts = { model: val[0].constructor };
        this.ownerDocument().populated(this.$__fullPath(path),
          val.map(function(v) { return v._id; }), popOpts);
      } else {
        popOpts = { model: val[0].constructor };
        this.populated(path, val.map(function(v) { return v._id; }), popOpts);
      }
      didPopulate = true;
    }
    val = schema.applySetters(val, this, false, priorVal);

    if (!didPopulate && this.$__.populated) {
      delete this.$__.populated[path];
    }

    this.$markValid(path);
  } catch (e) {
    var reason;
    if (!(e instanceof MongooseError.CastError)) {
      reason = e;
    }
    this.invalidate(path,
        new MongooseError.CastError(schema.instance, val, path, reason));
    shouldSet = false;
  }

  if (shouldSet) {
    this.$__set(pathToMark, path, constructing, parts, schema, val, priorVal);
  }

  return this;
};