/**
   * Module dependencies.
   */
  
  var Emitter = require('events').EventEmitter;
  var parser = require('socket.io-parser');
  var url = require('url');
  var debug = require('debug')('socket.io:socket');
  var hasBin = require('has-binary');
  
  /**
   * Module exports.
   */
  
  module.exports = exports = Socket;
  
  /**
   * Blacklisted events.
   *
   * @api public
   */
  
  exports.events = [
    'error',
    'connect',
    'disconnect',
    'newListener',
    'removeListener'
  ];
  
  /**
   * Flags.
   *
   * @api private
   */
  
  var flags = [
    'json',
    'volatile',
    'broadcast'
  ];
  
  /**
   * `EventEmitter#emit` reference.
   */
  
  var emit = Emitter.prototype.emit;
  
  /**
   * Interface to a `Client` for a given `Namespace`.
   *
   * @param {Namespace} nsp
   * @param {Client} client
   * @api public
   */
  
  function Socket(nsp, client){
    this.nsp = nsp;
    this.server = nsp.server;
    this.adapter = this.nsp.adapter;
    this.id = nsp.name + '#' + client.id;
    this.client = client;
    this.conn = client.conn;
    this.rooms = {};
    this.acks = {};
    this.connected = true;
    this.disconnected = false;
    this.handshake = this.buildHandshake();
  }
  
  /**
   * Inherits from `EventEmitter`.
   */
  
  Socket.prototype.__proto__ = Emitter.prototype;
  
  /**
   * Apply flags from `Socket`.
   */
  
  flags.forEach(function(flag){
    Socket.prototype.__defineGetter__(flag, function(){
      this.flags = this.flags || {};
      this.flags[flag] = true;
      return this;
    });
  });
  
  /**
   * `request` engine.io shortcut.
   *
   * @api public
   */
  
  Socket.prototype.__defineGetter__('request', function(){
    return this.conn.request;
  });
  
  /**
   * Builds the `handshake` BC object
   *
   * @api private
   */
  
  Socket.prototype.buildHandshake = function(){
    return {
      headers: this.request.headers,
      time: (new Date) + '',
      address: this.conn.remoteAddress,
      xdomain: !!this.request.headers.origin,
      secure: !!this.request.connection.encrypted,
      issued: +(new Date),
      url: this.request.url,
      query: url.parse(this.request.url, true).query || {}
    };
  };
  
  /**
   * Emits to this client.
   *
   * @return {Socket} self
   * @api public
   */
  
  Socket.prototype.emit = function(ev){
    if (~exports.events.indexOf(ev)) {
      emit.apply(this, arguments);
    } else {
      var args = Array.prototype.slice.call(arguments);
      var packet = {};
      packet.type = hasBin(args) ? parser.BINARY_EVENT : parser.EVENT;
      packet.data = args;
      var flags = this.flags || {};
  
      // access last argument to see if it's an ACK callback
      if ('function' == typeof args[args.length - 1]) {
        if (this._rooms || flags.broadcast) {
          throw new Error('Callbacks are not supported when broadcasting');
        }
  
        debug('emitting packet with ack id %d', this.nsp.ids);
        this.acks[this.nsp.ids] = args.pop();
        packet.id = this.nsp.ids++;
      }
  
      if (this._rooms || flags.broadcast) {
        this.adapter.broadcast(packet, {
          except: [this.id],
          rooms: this._rooms,
          flags: flags
        });
      } else {
        // dispatch packet
        this.packet(packet, {
          volatile: flags.volatile,
          compress: flags.compress
        });
      }
  
      // reset flags
      delete this._rooms;
      delete this.flags;
    }
    return this;
  };
  
  /**
   * Targets a room when broadcasting.
   *
   * @param {String} name
   * @return {Socket} self
   * @api public
   */
  
  Socket.prototype.to =
  Socket.prototype.in = function(name){
    this._rooms = this._rooms || [];
    if (!~this._rooms.indexOf(name)) this._rooms.push(name);
    return this;
  };
  
  /**
   * Sends a `message` event.
   *
   * @return {Socket} self
   * @api public
   */
  
  Socket.prototype.send =
  Socket.prototype.write = function(){
    var args = Array.prototype.slice.call(arguments);
    args.unshift('message');
    this.emit.apply(this, args);
    return this;
  };
  
  /**
   * Writes a packet.
   *
   * @param {Object} packet object
   * @param {Object} opts options
   * @api private
   */
  
  Socket.prototype.packet = function(packet, opts){
    packet.nsp = this.nsp.name;
    opts = opts || {};
    opts.compress = false !== opts.compress;
    this.client.packet(packet, opts);
  };
  
  /**
   * Joins a room.
   *
   * @param {String} room
   * @param {Function} fn optional, callback
   * @return {Socket} self
   * @api private
   */
  
  Socket.prototype.join = function(room, fn){
    debug('joining room %s', room);
    var self = this;
    if (this.rooms.hasOwnProperty(room)) {
      fn && fn(null);
      return this;
    }
    this.adapter.add(this.id, room, function(err){
      if (err) return fn && fn(err);
      debug('joined room %s', room);
      self.rooms[room] = room;
      fn && fn(null);
    });
    return this;
  };
  
  /**
   * Leaves a room.
   *
   * @param {String} room
   * @param {Function} fn optional, callback
   * @return {Socket} self
   * @api private
   */
  
  Socket.prototype.leave = function(room, fn){
    debug('leave room %s', room);
    var self = this;
    this.adapter.del(this.id, room, function(err){
      if (err) return fn && fn(err);
      debug('left room %s', room);
      delete self.rooms[room];
      fn && fn(null);
    });
    return this;
  };
  
  /**
   * Leave all rooms.
   *
   * @api private
   */
  
  Socket.prototype.leaveAll = function(){
    this.adapter.delAll(this.id);
    this.rooms = {};
  };
  
  /**
   * Called by `Namespace` upon succesful
   * middleware execution (ie: authorization).
   *
   * @api private
   */
  
  Socket.prototype.onconnect = function(){
    debug('socket connected - writing packet');
    this.nsp.connected[this.id] = this;
    this.join(this.id);
    this.packet({ type: parser.CONNECT });
  };
  
  /**
   * Called with each packet. Called by `Client`.
   *
   * @param {Object} packet
   * @api private
   */
  
  Socket.prototype.onpacket = function(packet){
    debug('got packet %j', packet);
    switch (packet.type) {
      case parser.EVENT:
        this.onevent(packet);
        break;
  
      case parser.BINARY_EVENT:
        this.onevent(packet);
        break;
  
      case parser.ACK:
        this.onack(packet);
        break;
  
      case parser.BINARY_ACK:
        this.onack(packet);
        break;
  
      case parser.DISCONNECT:
        this.ondisconnect();
        break;
  
      case parser.ERROR:
        this.emit('error', packet.data);
    }
  };
  
  /**
   * Called upon event packet.
   *
   * @param {Object} packet object
   * @api private
   */
  
  Socket.prototype.onevent = function(packet){
    var args = packet.data || [];
    debug('emitting event %j', args);
  
    if (null != packet.id) {
      debug('attaching ack callback to event');
      args.push(this.ack(packet.id));
    }
  
    emit.apply(this, args);
  };
  
  /**
   * Produces an ack callback to emit with an event.
   *
   * @param {Number} id packet id
   * @api private
   */
  
  Socket.prototype.ack = function(id){
    var self = this;
    var sent = false;
    return function(){
      // prevent double callbacks
      if (sent) return;
      var args = Array.prototype.slice.call(arguments);
      debug('sending ack %j', args);
  
      var type = hasBin(args) ? parser.BINARY_ACK : parser.ACK;
      self.packet({
        id: id,
        type: type,
        data: args
      });
  
      sent = true;
    };
  };
  
  /**
   * Called upon ack packet.
   *
   * @api private
   */
  
  Socket.prototype.onack = function(packet){
    var ack = this.acks[packet.id];
    if ('function' == typeof ack) {
      debug('calling ack %s with %j', packet.id, packet.data);
      ack.apply(this, packet.data);
      delete this.acks[packet.id];
    } else {
      debug('bad ack %s', packet.id);
    }
  };
  
  /**
   * Called upon client disconnect packet.
   *
   * @api private
   */
  
  Socket.prototype.ondisconnect = function(){
    debug('got disconnect packet');
    this.onclose('client namespace disconnect');
  };
  
  /**
   * Handles a client error.
   *
   * @api private
   */
  
  Socket.prototype.onerror = function(err){
    if (this.listeners('error').length) {
      this.emit('error', err);
    } else {
      console.error('Missing error handler on `socket`.');
      console.error(err.stack);
    }
  };
  
  /**
   * Called upon closing. Called by `Client`.
   *
   * @param {String} reason
   * @throw {Error} optional error object
   * @api private
   */
  
  Socket.prototype.onclose = function(reason){
    if (!this.connected) return this;
    debug('closing socket - reason %s', reason);
    this.leaveAll();
    this.nsp.remove(this);
    this.client.remove(this);
    this.connected = false;
    this.disconnected = true;
    delete this.nsp.connected[this.id];
    this.emit('disconnect', reason);
  };
  
  /**
   * Produces an `error` packet.
   *
   * @param {Object} err error object
   * @api private
   */
  
  Socket.prototype.error = function(err){
    this.packet({ type: parser.ERROR, data: err });
  };
  
  /**
   * Disconnects this client.
   *
   * @param {Boolean} close if `true`, closes the underlying connection
   * @return {Socket} self
   * @api public
   */
  
  Socket.prototype.disconnect = function(close){
    if (!this.connected) return this;
    if (close) {
      this.client.disconnect();
    } else {
      this.packet({ type: parser.DISCONNECT });
      this.onclose('server namespace disconnect');
    }
    return this;
  };
  
  /**
   * Sets the compress flag.
   *
   * @param {Boolean} compress if `true`, compresses the sending data
   * @return {Socket} self
   * @api public
   */
  
  Socket.prototype.compress = function(compress){
    this.flags = this.flags || {};
    this.flags.compress = compress;
    return this;
  };