+(function (global, factory) {
  if (typeof exports === 'undefined') {
    factory(global.webduino || {});
  } else {
    module.exports = factory;
  }
}(this, function (scope) {
  'use strict';

  var Module = scope.Module,
    BoardEvent = scope.BoardEvent,
    proto;

  var HX711_MESSAGE = [0x04, 0x15];

  var HX711Event = {

    /**
     * Fires when the value of weight has changed.
     * 
     * @event HX711.MESSAGE
     */
    MESSAGE: 'message'
  };

  /**
   * The HX711 Class.
   *
   * HX711 is a precision 24-bit analogto-digital converter (ADC) designed for weigh scales.
   *
   * @namespace webduino.module
   * @class HX711
   * @constructor
   * @param {webduino.Board} board The board that the IRLed is attached to.
   * @param {Integer} sckPin The pin that Serial Clock Input is attached to.
   * @param {Integer} dtPin The pin that Data Output is attached to.
   * @extends webduino.Module
   */
  function HX711(board, sckPin, dtPin) {
    Module.call(this);
    this._board = board;
    this._dt = !isNaN(dtPin) ? board.getDigitalPin(dtPin) : dtPin;
    this._sck = !isNaN(sckPin) ? board.getDigitalPin(sckPin) : sckPin;

    this._init = false;
    this._weight = 0;
    this._callback = function() {};
    this._messageHandler = onMessage.bind(this);
    this._board.send([0xf0, 0x04, 0x15, 0x00,
      this._sck._number, this._dt._number, 0xf7
    ]);
  }

  function onMessage(event) {
    var msg = event.message;
    if (msg[0] == HX711_MESSAGE[0] && msg[1] == HX711_MESSAGE[1]) {
      this.emit(HX711Event.MESSAGE, msg.slice(2));
    }
  }

  HX711.prototype = proto = Object.create(Module.prototype, {
    constructor: {
      value: HX711
    },

    /**
     * The state indicating whether the module is measuring.
     * 
     * @attribute state
     * @type {String} `on` or `off`
     */
    state: {
      get: function() {
        return this._state;
      },
      set: function(val) {
        this._state = val;
      }
    }
  });

  /**
   * Start detection.
   *
   * @method measure
   * @param {Function} [callback] Callback after starting detection.
   */
  
  /**
   * Start detection.
   *
   * @method on
   * @param {Function} [callback] Callback after starting detection.
   * @deprecated `on()` is deprecated, use `measure()` instead.
   */
  proto.measure = proto.on = function(callback) {
    var _this = this;
    this._board.send([0xf0, 0x04, 0x15, 0x01, 0xf7]);
    if (typeof callback !== 'function') {
      callback = function() {};
    }
    this._callback = function(rawData) {
      var weight = '';
      for (var i = 0; i < rawData.length; i++) {
        weight += (rawData[i] - 0x30);
      }
      _this._weight = parseFloat(weight);
      callback(_this._weight);
    };
    this._state = 'on';
    this._board.on(BoardEvent.SYSEX_MESSAGE, this._messageHandler);
    this.addListener(HX711Event.MESSAGE, this._callback);
  };

  /**
   * Stop detection.
   *
   * @method off
   */
  proto.off = function() {
    this._state = 'off';
    this._board.send([0xf0, 0x04, 0x15, 0x02, 0xf7]);
    this._board.removeListener(BoardEvent.SYSEX_MESSAGE, this._messageHandler);
    this.removeListener(HX711Event.MESSAGE, this._callback);
    this._callback = null;
  };

  scope.module.HX711 = HX711;
}));