Audio Channel Controller

audio_channel_controller.js

/* global BaseUI */
'use strict';

(function(exports) {
  var AudioChannelController = function(app) {
    this.app = app;
    this.appId = app.instanceID;
    this._audioChannels = new Map();
    app.browser.element.allowedAudioChannels.forEach((channel) => {
      channel.addEventListener('activestatechanged', this);
      this._audioChannels.set(channel.name, channel);
    });
    return this;
  };

  AudioChannelController.prototype = Object.create(BaseUI.prototype); 

  AudioChannelController.prototype.EVENT_PREFIX = 'audiochannel';

  AudioChannelController.prototype.handleEvent = function(evt) {
    var channel = evt.target;
    switch (evt.type) {
      case 'activestatechanged':
        // We should get the `isActive` stage from evt.target.isActive,
        // and get channel from evt.target.channel.
        channel.isActive().onsuccess = (evt) => {
          this.publish('statechanged', {
            audioChannelController: this,
            channelName: channel.name,
            isActive: evt.target.result
          });
        };
        break;
    }
  };  

  /**
   * Play the audio channel.
   *
   * @param {BrowserElementAudioChannel} channel A audio channel.
   * @param {Number} volume 0 to 1.
   */
  AudioChannelController.prototype.play =
    function(channelName, volume, callback) {
    var playRequest = this._audioChannels.get(channelName).setMuted(false);
    playRequest.onsuccess = () => {
      callback && callback();
      this.debug(channelName + ' is playing');
    };
    playRequest.onerror = () => {
      this.debug('Error of playing ' + channelName);
    };
    if (volume != null) {
      this.setVolume(channelName, volume);
    }
  };

  /**
   * Pause the audio channel.
   *
   * @param {BrowserElementAudioChannel} channel A audio channel.
   */
  AudioChannelController.prototype.pause = function(channelName, callback) {
    var pauseRequest = this._audioChannels.get(channelName).setMuted(true);
    pauseRequest.onsuccess = () => {
      callback && callback();
      this.debug('Pause ' + channelName);
    };
    pauseRequest.onerror = () => {
      this.debug('Error of pausing the channel');
    };
  };

  /**
   * Change volume of audio channels.
   *
   * @param {BrowserElementAudioChannel} channel.
   * Audio channels you want to turn down or up its volume.
   * @param {Number} volume 0 to 1.
   */
  AudioChannelController.prototype.setVolume =
    function(channelName, volume, callback) {
    var volumeRequest = this._audioChannels.get(channelName).setVolume(volume);
    volumeRequest.onsuccess = () => {
      callback && callback();
      this.debug(channelName + ' set volume: ' + volume);
    };
    volumeRequest.onerror = () => {
      this.debug('Error of setting volume');
    };
  };

  exports.AudioChannelController = AudioChannelController;
}(window));