define(function(require, exports, module) {
'use strict';

/**
 * Exports
 */

module.exports = Sounds;

/**
 * Initialize a new `Sounds` interface.
 *
 * @constructor
 */
function Sounds(list) {
  this.items = {};
  (list || []).forEach(this.add, this);
}

/**
 * Add a new sound.
 *
 * Checks if this sound
 * is enabled, and sets
 * up an observer.
 *
 * @param {Object} data
 *
 */
Sounds.prototype.add = function(data) {
  var self = this;
  var sound = {
    name: data.name,
    url: data.url,
    setting: data.setting,
    enabled: false
  };

  this.items[data.name] = sound;
  this.isEnabled(sound, function(value) {
    self.setEnabled(sound, value);
    self.observeSetting(sound);
  });
};

/**
 * Check if a sound is
 * enabled inside mozSettings.
 *
 * This is wrapped in a setTimeout
 * to prevent expensive mozSettings
 * API from blocking other operations.
 *
 * @param  {Object}   sound
 * @param  {Function} done
 */
Sounds.prototype.isEnabled = function(sound, done) {
  setTimeout(function() {
    var mozSettings = navigator.mozSettings;
    var key = sound.setting;

    // Requires navigator.mozSettings
    if (!mozSettings) {
      return;
    }

    mozSettings
      .createLock()
      .get(key)
      .onsuccess = onSuccess;

    function onSuccess(e) {
      var result = e.target.result[key];
      done(result);
    }
  });
};

/**
 * Observe mozSettings for changes
 * on the given settings key.
 *
 * @param  {Object} sound
 *
 */
Sounds.prototype.observeSetting = function(sound) {
  var mozSettings = navigator.mozSettings;
  var key = sound.setting;
  var self = this;
  if (mozSettings) {
    mozSettings.addObserver(key, function(e) {
      self.setEnabled(sound, e.settingValue);
    });
  }
};

/**
 * Set a sounds `enabled` key.
 *
 * @param {Object} sound
 * @param {Boolean} value
 *
 */
Sounds.prototype.setEnabled = function(sound, value) {
  sound.enabled = value;
};

/**
 * Play a sound by name.
 *
 * @param  {String} name
 * @public
 */
Sounds.prototype.play = function(name) {
  var sound = this.items[name];
  if (!sound.audio) {
    sound.audio = this.createAudio(sound.url);
  }

  this.playSound(sound);
};

/**
 * Return a function that plays
 * the given sound when called.
 *
 * @param  {String} name
 * @return {Funciton}
 * @public
 */
Sounds.prototype.player = function(name) {
  return (function() { this.play(name); }).bind(this);
};

/**
 * Play a sound.
 *
 * @param  {Object} sound
 *
 */
Sounds.prototype.playSound = function(sound) {
  if (sound.enabled) {
    // cloneNode() lets us play overlapping sounds and is needed when the
    // user takes pictures very rapidly.
    // See http://robert.ocallahan.org/2011/11/latency-of-html5-sounds.html
    sound.audio.cloneNode(true).play();
  }
};

/**
 * Create an audio element.
 *
 * @param  {String} url
 * @return {HTMLAudioElement}
 */
Sounds.prototype.createAudio = function(url) {
  var audio = new Audio(url);
  audio.mozAudioChannelType = 'notification';
  return audio;
};

});