/*!
 * ws: a node.js websocket client
 * Copyright(c) 2011 Einar Otto Stangvik <einaros@gmail.com>
 * MIT Licensed
 */

var events = require('events')
  , util = require('util')
  , EventEmitter = events.EventEmitter;

/**
 * State constants
 */

var EMPTY = 0
  , BODY = 1;

/**
 * Hixie Receiver implementation
 */

function Receiver () {
  this.state = EMPTY;
  this.buffers = [];
  this.messageEnd = -1;
  this.spanLength = 0;
  this.dead = false;
}

module.exports = Receiver;

/**
 * Inherits from EventEmitter.
 */

util.inherits(Receiver, events.EventEmitter);

/**
 * Add new data to the parser.
 *
 * @api public
 */

Receiver.prototype.add = function(data) {
  var self = this;
  function doAdd() {
    if (self.state === EMPTY) {
      if (data.length == 2 && data[0] == 0xFF && data[1] == 0x00) {
        self.reset();
        self.emit('close');
        return;
      }
      if (data[0] !== 0x00) {
        self.error('payload must start with 0x00 byte', true);
        return;
      }
      data = data.slice(1);
      self.state = BODY;
    }
    self.buffers.push(data);
    if ((self.messageEnd = bufferIndex(data, 0xFF)) != -1) {
      self.spanLength += self.messageEnd;
      return self.parse();
    }
    else self.spanLength += data.length;
  }
  while(data) data = doAdd();
}

/**
 * Releases all resources used by the receiver.
 *
 * @api public
 */

Receiver.prototype.cleanup = function() {
  this.dead = true;
  this.state = EMPTY;
  this.buffers = [];
}

/**
 * Process buffered data.
 *
 * @api public
 */

Receiver.prototype.parse = function() {
  var output = new Buffer(this.spanLength);
  var outputIndex = 0;
  for (var bi = 0, bl = this.buffers.length; bi < bl - 1; ++bi) {
    var buffer = this.buffers[bi];
    buffer.copy(output, outputIndex);
    outputIndex += buffer.length;
  }
  var lastBuffer = this.buffers[this.buffers.length - 1];
  if (this.messageEnd > 0) lastBuffer.copy(output, outputIndex, 0, this.messageEnd);
  var tail = null;
  if (this.messageEnd < lastBuffer.length - 1) {
    tail = lastBuffer.slice(this.messageEnd + 1);
  }
  this.reset();
  this.emit('text', output.toString('utf8'));
  return tail;
}

/**
 * Handles an error
 *
 * @api private
 */

Receiver.prototype.error = function (reason, terminate) {
  this.reset();
  this.emit('error', reason, terminate);
  return this;
}

/**
 * Reset parser state
 *
 * @api private
 */

Receiver.prototype.reset = function (reason) {
  if (this.dead) return;
  this.state = EMPTY;
  this.buffers = [];
  this.messageEnd = -1;
  this.spanLength = 0;
}

/**
 * Internal api
 */

function bufferIndex(buffer, byte) {
  for (var i = 0, l = buffer.length; i < l; ++i) {
    if (buffer[i] === byte) return i;
  }
  return -1;
}