/**
 * Play and fade between multiple audio files.
 *
 * @class
 */
pageflow.Audio.MultiPlayer = function(pool, options) {
  if (options.crossFade && options.playFromBeginning) {
    throw 'pageflow.Audio.MultiPlayer: The options crossFade and playFromBeginning can not be used together at the moment.';
  }

  var current = new pageflow.AudioPlayer.Null();
  var currentId = null;
  var that = this;

  /**
   * Continue playback.
   */
  this.resume = function() {
    return current.play();
  };

  /**
   * Continue playback with fade in.
   */
  this.resumeAndFadeIn = function() {
    return current.playAndFadeIn(options.fadeDuration);
  };

  this.seek = function(position) {
    return current.seek(position);
  };

  this.pause = function() {
    return current.pause();
  };

  this.paused = function() {
    return current.paused();
  };

  this.fadeOutAndPause = function() {
    return current.fadeOutAndPause(options.fadeDuration);
  };

  this.position = function() {
    return current.position;
  };

  this.duration = function() {
    return current.duration;
  };

  this.fadeTo = function(id) {
    return changeCurrent(id, function(player) {
      return player.playAndFadeIn(options.fadeDuration);
    });
  };

  this.play = function(id) {
    return changeCurrent(id, function(player) {
      return player.play();
    });
  };

  this.changeVolumeFactor = function(factor) {
    return current.changeVolumeFactor(factor, options.fadeDuration);
  };

  this.formatTime = function(time) {
    return current.formatTime(time);
  };

  function changeCurrent(id, callback) {
    if (!options.playFromBeginning && id === currentId && !current.paused()) {
      return;
    }

    var player = pool.get(id);
    currentId = id;

    var fadeOutPromise = current.fadeOutAndPause(options.fadeDuration);

    fadeOutPromise.then(function() {
      stopEventPropagation(current);
    });

    handleCrossFade(fadeOutPromise).then(function() {
      current = player;
      startEventPropagation(current, id);

      handlePlayFromBeginning(player).then(function() {
        callback(player);
      });
    });
  }

  function handleCrossFade(fadePomise) {
    if (options.crossFade) {
      return new $.Deferred().resolve().promise();
    }
    else {
      return fadePomise;
    }
  }

  function handlePlayFromBeginning(player) {
    if (options.playFromBeginning || options.rewindOnChange) {
      return player.rewind();
    }
    else {
      return new $.Deferred().resolve().promise();
    }
  }

  function startEventPropagation(player, id) {
    that.listenTo(player, 'play', function() {
      that.trigger('play', {audioFileId: id});
    });

    that.listenTo(player, 'pause', function() {
      that.trigger('pause', {audioFileId: id});
    });

    that.listenTo(player, 'timeupdate', function() {
      that.trigger('timeupdate', {audioFileId: id});
    });

    that.listenTo(player, 'ended', function() {
      that.trigger('ended', {audioFileId: id});
    });

    that.listenTo(player, 'playfailed', function() {
      that.trigger('playfailed', {audioFileId: id});
    });
  }

  function stopEventPropagation(player) {
    that.stopListening(player);
  }
};

_.extend(pageflow.Audio.MultiPlayer.prototype, Backbone.Events);