+(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 PhotocellEvent = {

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

  /**
   * The Photocell class.
   *
   * Photocell is small, inexpensive, low-power sensor that allow you to detect light.
   * 
   * @namespace webduino.module
   * @class Photocell
   * @constructor
   * @param {webduino.Board} board Board that the photocell is attached to.
   * @param {Integer} analogPinNumber The pin that the photocell is connected to.
   * @extends webduino.Module
   */
  function Photocell(board, analogPinNumber) {
    Module.call(this);
    this._board = board;
    this._pinNumber = Number(analogPinNumber);
    this._messageHandler = onMessage.bind(this);
  }

  function onMessage(event) {
    var pin = event.pin;
    if (this._pinNumber !== pin.analogNumber) {
      return false;
    }

    this.emit(PhotocellEvent.MESSAGE, pin.value);
  }

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

    /**
     * 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) {
    this._board.enableAnalogPin(this._pinNumber);

    if (typeof callback !== 'function') {
      callback = function () {};
    }

    this._callback = function (val) {
      callback(val);
    };

    this._state = 'on';
    this._board.on(BoardEvent.ANALOG_DATA, this._messageHandler);
    this.addListener(PhotocellEvent.MESSAGE, this._callback);
  };

  /**
   * Stop detection.
   *
   * @method off
   */
  proto.off = function () {
    this._state = 'off';
    this._board.disableAnalogPin(this._pinNumber);
    this._board.removeListener(BoardEvent.ANALOG_DATA, this._messageHandler);
    this.removeListener(PhotocellEvent.MESSAGE, this._callback);
    this._callback = null;
  };

  scope.module.Photocell = Photocell;
}));