chrome/browser/resources/file_manager/foreground/js/media/audio_player.js

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

'use strict';

/**
 * TODO(mtomasz): Rewrite the entire audio player.
 *
 * @param {HTMLElement} container Container element.
 * @constructor
 */
function AudioPlayer(container) {
  this.container_ = container;
  this.metadataCache_ = MetadataCache.createFull();
  this.currentTrack_ = -1;
  this.playlistGeneration_ = 0;
  this.selectedEntry_ = null;
  this.volumeManager_ = new VolumeManagerWrapper(
      VolumeManagerWrapper.DriveEnabledStatus.DRIVE_ENABLED);

  this.container_.classList.add('collapsed');

  function createChild(opt_className, opt_tag) {
    var child = container.ownerDocument.createElement(opt_tag || 'div');
    if (opt_className)
      child.className = opt_className;
    container.appendChild(child);
    return child;
  }

  // We create two separate containers (for expanded and compact view) and keep
  // two sets of TrackInfo instances. We could fiddle with a single set instead
  // but it would make keeping the list scroll position very tricky.
  this.trackList_ = createChild('track-list');
  this.trackStack_ = createChild('track-stack');

  createChild('title-button collapse').addEventListener(
      'click', this.onExpandCollapse_.bind(this));

  this.audioControls_ = new FullWindowAudioControls(
      createChild(), this.advance_.bind(this), this.onError_.bind(this));

  this.audioControls_.attachMedia(createChild('', 'audio'));

  chrome.fileBrowserPrivate.getStrings(function(strings) {
    container.ownerDocument.title = strings['AUDIO_PLAYER_TITLE'];
    this.errorString_ = strings['AUDIO_ERROR'];
    this.offlineString_ = strings['AUDIO_OFFLINE'];
    AudioPlayer.TrackInfo.DEFAULT_ARTIST =
        strings['AUDIO_PLAYER_DEFAULT_ARTIST'];
  }.bind(this));

  this.volumeManager_.addEventListener('externally-unmounted',
      this.onExternallyUnmounted_.bind(this));

  window.addEventListener('resize', this.onResize_.bind(this));

  // Show the window after DOM is processed.
  var currentWindow = chrome.app.window.current();
  setTimeout(currentWindow.show.bind(currentWindow), 0);
}

/**
 * Initial load method (static).
 */
AudioPlayer.load = function() {
  document.ondragstart = function(e) { e.preventDefault() };

  // TODO(mtomasz): Consider providing an exact size icon, instead of relying
  // on downsampling by ash.
  chrome.app.window.current().setIcon(
      'foreground/images/media/2x/audio_player.png');

  AudioPlayer.instance =
      new AudioPlayer(document.querySelector('.audio-player'));
  reload();
};

util.addPageLoadHandler(AudioPlayer.load);

/**
 * Unload the player.
 */
function unload() {
  if (AudioPlayer.instance)
    AudioPlayer.instance.onUnload();
}

/**
 * Reload the player.
 */
function reload() {
  if (window.appState) {
    util.saveAppState();
    AudioPlayer.instance.load(window.appState);
    return;
  }
}

/**
 * Load a new playlist.
 * @param {Playlist} playlist Playlist object passed via mediaPlayerPrivate.
 */
AudioPlayer.prototype.load = function(playlist) {
  this.playlistGeneration_++;
  this.audioControls_.pause();
  this.currentTrack_ = -1;

  // Save the app state, in case of restart.
  window.appState = playlist;
  util.saveAppState();

  util.URLsToEntries(playlist.items, function(entries) {
    this.entries_ = entries;
    this.invalidTracks_ = {};
    this.cancelAutoAdvance_();

    if (this.entries_.length <= 1)
      this.container_.classList.add('single-track');
    else
      this.container_.classList.remove('single-track');

    this.syncHeight_();

    this.trackList_.textContent = '';
    this.trackStack_.textContent = '';

    this.trackListItems_ = [];
    this.trackStackItems_ = [];

    if (this.entries_.length == 0)
      return;

    for (var i = 0; i != this.entries_.length; i++) {
      var entry = this.entries_[i];
      var onClick = this.select_.bind(this, i, false /* no restore */);
      this.trackListItems_.push(
          new AudioPlayer.TrackInfo(this.trackList_, entry, onClick));
      this.trackStackItems_.push(
          new AudioPlayer.TrackInfo(this.trackStack_, entry, onClick));
    }

    this.select_(playlist.position, !!playlist.time);

    // This class will be removed if at least one track has art.
    this.container_.classList.add('noart');

    // Load the selected track metadata first, then load the rest.
    this.loadMetadata_(playlist.position);
    for (i = 0; i != this.entries_.length; i++) {
      if (i != playlist.position)
        this.loadMetadata_(i);
    }
  }.bind(this));
};

/**
 * Load metadata for a track.
 * @param {number} track Track number.
 * @private
 */
AudioPlayer.prototype.loadMetadata_ = function(track) {
  this.fetchMetadata_(
      this.entries_[track], this.displayMetadata_.bind(this, track));
};

/**
 * Display track's metadata.
 * @param {number} track Track number.
 * @param {Object} metadata Metadata object.
 * @param {string=} opt_error Error message.
 * @private
 */
AudioPlayer.prototype.displayMetadata_ = function(track, metadata, opt_error) {
  this.trackListItems_[track].
      setMetadata(metadata, this.container_, opt_error);
  this.trackStackItems_[track].
      setMetadata(metadata, this.container_, opt_error);
};

/**
 * Closes audio player when a volume containing the selected item is unmounted.
 * @param {Event} event The unmount event.
 * @private
 */
AudioPlayer.prototype.onExternallyUnmounted_ = function(event) {
  if (!this.selectedEntry_)
    return;

  if (this.volumeManager_.getVolumeInfo(this.selectedEntry_) ===
      event.volumeInfo) {
    window.close();
  }
};

/**
 * Called on window is being unloaded.
 */
AudioPlayer.prototype.onUnload = function() {
  this.audioControls_.cleanup();
  this.volumeManager_.dispose();
};

/**
 * Select a new track to play.
 * @param {number} newTrack New track number.
 * @param {boolean=} opt_restoreState True if restoring the play state from URL.
 * @private
 */
AudioPlayer.prototype.select_ = function(newTrack, opt_restoreState) {
  if (this.currentTrack_ == newTrack) return;

  this.changeSelectionInList_(this.currentTrack_, newTrack);
  this.changeSelectionInStack_(this.currentTrack_, newTrack);

  this.currentTrack_ = newTrack;

  if (window.appState) {
    window.appState.position = this.currentTrack_;
    window.appState.time = 0;
    util.saveAppState();
  } else {
    util.platform.setPreference(AudioPlayer.TRACK_KEY, this.currentTrack_);
  }

  this.scrollToCurrent_(false);

  var currentTrack = this.currentTrack_;
  var entry = this.entries_[currentTrack];
  this.fetchMetadata_(entry, function(metadata) {
    if (this.currentTrack_ != currentTrack)
      return;
    this.audioControls_.load(entry, opt_restoreState);

    // Resolve real filesystem path of the current audio file.
    this.selectedEntry_ = entry;
  }.bind(this));
};

/**
 * @param {Entry} entry Track file entry.
 * @param {function(object)} callback Callback.
 * @private
 */
AudioPlayer.prototype.fetchMetadata_ = function(entry, callback) {
  this.metadataCache_.get(entry, 'thumbnail|media|streaming',
      function(generation, metadata) {
        // Do nothing if another load happened since the metadata request.
        if (this.playlistGeneration_ == generation)
          callback(metadata);
      }.bind(this, this.playlistGeneration_));
};

/**
 * @param {number} oldTrack Old track number.
 * @param {number} newTrack New track number.
 * @private
 */
AudioPlayer.prototype.changeSelectionInList_ = function(oldTrack, newTrack) {
  this.trackListItems_[newTrack].getBox().classList.add('selected');

  if (oldTrack >= 0) {
    this.trackListItems_[oldTrack].getBox().classList.remove('selected');
  }
};

/**
 * @param {number} oldTrack Old track number.
 * @param {number} newTrack New track number.
 * @private
 */
AudioPlayer.prototype.changeSelectionInStack_ = function(oldTrack, newTrack) {
  var newBox = this.trackStackItems_[newTrack].getBox();
  newBox.classList.add('selected');  // Put on top immediately.
  newBox.classList.add('visible');  // Start fading in.

  if (oldTrack >= 0) {
    var oldBox = this.trackStackItems_[oldTrack].getBox();
    oldBox.classList.remove('selected'); // Put under immediately.
    setTimeout(function() {
      if (!oldBox.classList.contains('selected')) {
        // This will start fading out which is not really necessary because
        // oldBox is already completely obscured by newBox.
        oldBox.classList.remove('visible');
      }
    }, 300);
  }
};

/**
 * Scrolls the current track into the viewport.
 *
 * @param {boolean} keepAtBottom If true, make the selected track the last
 *   of the visible (if possible). If false, perform minimal scrolling.
 * @private
 */
AudioPlayer.prototype.scrollToCurrent_ = function(keepAtBottom) {
  var box = this.trackListItems_[this.currentTrack_].getBox();
  this.trackList_.scrollTop = Math.max(
      keepAtBottom ? 0 : Math.min(box.offsetTop, this.trackList_.scrollTop),
      box.offsetTop + box.offsetHeight - this.trackList_.clientHeight);
};

/**
 * @return {boolean} True if the player is be displayed in compact mode.
 * @private
 */
AudioPlayer.prototype.isCompact_ = function() {
  return this.container_.classList.contains('collapsed') ||
         this.container_.classList.contains('single-track');
};

/**
 * Go to the previous or the next track.
 * @param {boolean} forward True if next, false if previous.
 * @param {boolean=} opt_onlyIfValid True if invalid tracks should be selected.
 * @private
 */
AudioPlayer.prototype.advance_ = function(forward, opt_onlyIfValid) {
  this.cancelAutoAdvance_();

  var newTrack = this.currentTrack_ + (forward ? 1 : -1);
  if (newTrack < 0) newTrack = this.entries_.length - 1;
  if (newTrack == this.entries_.length) newTrack = 0;
  if (opt_onlyIfValid && this.invalidTracks_[newTrack])
    return;
  this.select_(newTrack);
};

/**
 * Media error handler.
 * @private
 */
AudioPlayer.prototype.onError_ = function() {
  var track = this.currentTrack_;

  this.invalidTracks_[track] = true;

  this.fetchMetadata_(
      this.entries_[track],
      function(metadata) {
        var error = (!navigator.onLine && metadata.streaming) ?
            this.offlineString_ : this.errorString_;
        this.displayMetadata_(track, metadata, error);
        this.scheduleAutoAdvance_();
      }.bind(this));
};

/**
 * Schedule automatic advance to the next track after a timeout.
 * @private
 */
AudioPlayer.prototype.scheduleAutoAdvance_ = function() {
  this.cancelAutoAdvance_();
  this.autoAdvanceTimer_ = setTimeout(
      function() {
        this.autoAdvanceTimer_ = null;
        // We are advancing only if the next track is not known to be invalid.
        // This prevents an endless auto-advancing in the case when all tracks
        // are invalid (we will only visit each track once).
        this.advance_(true /* forward */, true /* only if valid */);
      }.bind(this),
      3000);
};

/**
 * Cancel the scheduled auto advance.
 * @private
 */
AudioPlayer.prototype.cancelAutoAdvance_ = function() {
  if (this.autoAdvanceTimer_) {
    clearTimeout(this.autoAdvanceTimer_);
    this.autoAdvanceTimer_ = null;
  }
};

/**
 * Expand/collapse button click handler. Toggles the mode and updates the
 * height of the window.
 *
 * @private
 */
AudioPlayer.prototype.onExpandCollapse_ = function() {
  if (!this.isCompact_()) {
    this.setExpanded_(false);
    this.lastExpandedHeight_ = window.innerHeight;
  } else {
    this.setExpanded_(true);
  }
  this.syncHeight_();
};

/**
 * Toggles the current expand mode.
 *
 * @param {boolean} on True if on, false otherwise.
 * @private
 */
AudioPlayer.prototype.setExpanded_ = function(on) {
  if (on) {
    this.container_.classList.remove('collapsed');
    this.scrollToCurrent_(true);
  } else {
    this.container_.classList.add('collapsed');
  }
};

/**
 * Toggles the expanded mode when resizing.
 *
 * @param {Event} event Resize event.
 * @private
 */
AudioPlayer.prototype.onResize_ = function(event) {
  if (this.isCompact_() &&
      window.innerHeight >= AudioPlayer.EXPANDED_MODE_MIN_HEIGHT) {
    this.setExpanded_(true);
  } else if (!this.isCompact_() &&
             window.innerHeight < AudioPlayer.EXPANDED_MODE_MIN_HEIGHT) {
    this.setExpanded_(false);
  }
};

/* Keep the below constants in sync with the CSS. */

/**
 * Window header size in pixels.
 * @type {number}
 * @const
 */
AudioPlayer.HEADER_HEIGHT = 28;

/**
 * Track height in pixels.
 * @type {number}
 * @const
 */
AudioPlayer.TRACK_HEIGHT = 58;

/**
 * Controls bar height in pixels.
 * @type {number}
 * @const
 */
AudioPlayer.CONTROLS_HEIGHT = 35;

/**
 * Default number of items in the expanded mode.
 * @type {number}
 * @const
 */
AudioPlayer.DEFAULT_EXPANDED_ITEMS = 5;

/**
 * Minimum size of the window in the expanded mode in pixels.
 * @type {number}
 * @const
 */
AudioPlayer.EXPANDED_MODE_MIN_HEIGHT = AudioPlayer.CONTROLS_HEIGHT +
                                       AudioPlayer.TRACK_HEIGHT * 2;

/**
 * Set the correct player window height.
 * @private
 */
AudioPlayer.prototype.syncHeight_ = function() {
  var targetHeight;

  if (!this.isCompact_()) {
    // Expanded.
    if (this.lastExpandedHeight_) {
      targetHeight = this.lastExpandedHeight_;
    } else {
      var expandedListHeight =
        Math.min(this.entries_.length, AudioPlayer.DEFAULT_EXPANDED_ITEMS) *
                                    AudioPlayer.TRACK_HEIGHT;
      targetHeight = AudioPlayer.CONTROLS_HEIGHT + expandedListHeight;
    }
  } else {
    // Not expaned.
    targetHeight = AudioPlayer.CONTROLS_HEIGHT + AudioPlayer.TRACK_HEIGHT;
  }

  window.resizeTo(window.innerWidth, targetHeight + AudioPlayer.HEADER_HEIGHT);
};

/**
 * Create a TrackInfo object encapsulating the information about one track.
 *
 * @param {HTMLElement} container Container element.
 * @param {Entry} entry Track entry.
 * @param {function} onClick Click handler.
 * @constructor
 */
AudioPlayer.TrackInfo = function(container, entry, onClick) {
  this.entry_ = entry;

  var doc = container.ownerDocument;

  this.box_ = doc.createElement('div');
  this.box_.className = 'track';
  this.box_.addEventListener('click', onClick);
  container.appendChild(this.box_);

  this.art_ = doc.createElement('div');
  this.art_.className = 'art blank';
  this.box_.appendChild(this.art_);

  this.img_ = doc.createElement('img');
  this.art_.appendChild(this.img_);

  this.data_ = doc.createElement('div');
  this.data_.className = 'data';
  this.box_.appendChild(this.data_);

  this.title_ = doc.createElement('div');
  this.title_.className = 'data-title';
  this.data_.appendChild(this.title_);

  this.artist_ = doc.createElement('div');
  this.artist_.className = 'data-artist';
  this.data_.appendChild(this.artist_);
};

/**
 * @return {HTMLDivElement} The wrapper element for the track.
 */
AudioPlayer.TrackInfo.prototype.getBox = function() { return this.box_ };

/**
 * @return {string} Default track title (file name extracted from the entry).
 */
AudioPlayer.TrackInfo.prototype.getDefaultTitle = function() {
  // TODO(mtomasz): Reuse ImageUtil.getDisplayNameFromName().
  var name = this.entry_.name;
  var dotIndex = name.lastIndexOf('.');
  var title = dotIndex >= 0 ? name.substr(0, dotIndex) : name;
  return title;
};

/**
 * TODO(kaznacheev): Localize.
 */
AudioPlayer.TrackInfo.DEFAULT_ARTIST = 'Unknown Artist';

/**
 * @return {string} 'Unknown artist' string.
 */
AudioPlayer.TrackInfo.prototype.getDefaultArtist = function() {
  return AudioPlayer.TrackInfo.DEFAULT_ARTIST;
};

/**
 * @param {Object} metadata The metadata object.
 * @param {HTMLElement} container The container for the tracks.
 * @param {string} error Error string.
 */
AudioPlayer.TrackInfo.prototype.setMetadata = function(
    metadata, container, error) {
  if (error) {
    this.art_.classList.add('blank');
    this.art_.classList.add('error');
    container.classList.remove('noart');
  } else if (metadata.thumbnail && metadata.thumbnail.url) {
    this.img_.onload = function() {
      // Only display the image if the thumbnail loaded successfully.
      this.art_.classList.remove('blank');
      container.classList.remove('noart');
    }.bind(this);
    this.img_.src = metadata.thumbnail.url;
  }
  this.title_.textContent = (metadata.media && metadata.media.title) ||
      this.getDefaultTitle();
  this.artist_.textContent = error ||
      (metadata.media && metadata.media.artist) || this.getDefaultArtist();
};

/**
 * Audio controls specific for the Audio Player.
 *
 * @param {HTMLElement} container Parent container.
 * @param {function(boolean)} advanceTrack Parameter: true=forward.
 * @param {function} onError Error handler.
 * @constructor
 */
function FullWindowAudioControls(container, advanceTrack, onError) {
  AudioControls.apply(this, arguments);

  document.addEventListener('keydown', function(e) {
    if (e.keyIdentifier == 'U+0020') {
      this.togglePlayState();
      e.preventDefault();
    }
  }.bind(this));
}

FullWindowAudioControls.prototype = { __proto__: AudioControls.prototype };

/**
 * Enable play state restore from the location hash.
 * @param {FileEntry} entry Source Entry.
 * @param {boolean} restore True if need to restore the play state.
 */
FullWindowAudioControls.prototype.load = function(entry, restore) {
  this.media_.src = entry.toURL();
  this.media_.load();
  this.restoreWhenLoaded_ = restore;
};

/**
 * Save the current state so that it survives page/app reload.
 */
FullWindowAudioControls.prototype.onPlayStateChanged = function() {
  this.encodeState();
};

/**
 * Restore the state after page/app reload.
 */
FullWindowAudioControls.prototype.restorePlayState = function() {
  if (this.restoreWhenLoaded_) {
    this.restoreWhenLoaded_ = false;  // This should only work once.
    if (this.decodeState())
      return;
  }
  this.play();
};