Initial

resources/app/client/data/collections/playlists.js

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+/**
+ * The singleton collection of Playlist documents which exist within the active World.
+ * This Collection is accessible within the Game object as game.playlists.
+ * @extends {WorldCollection}
+ *
+ * @see {@link Playlist} The Playlist document
+ * @see {@link PlaylistDirectory} The PlaylistDirectory sidebar directory
+ */
+class Playlists extends WorldCollection {
+
+  /** @override */
+  static documentName = "Playlist";
+
+  /* -------------------------------------------- */
+
+  /**
+   * Return the subset of Playlist documents which are currently playing
+   * @type {Playlist[]}
+   */
+  get playing() {
+    return this.filter(s => s.playing);
+  }
+
+  /* -------------------------------------------- */
+
+  /**
+   * Perform one-time initialization to begin playback of audio.
+   * @returns {Promise<void>}
+   */
+  async initialize() {
+    await game.audio.unlock;
+    for ( let playlist of this ) {
+      for ( let sound of playlist.sounds ) sound.sync();
+    }
+    ui.playlists?.render();
+  }
+
+  /* -------------------------------------------- */
+
+  /**
+   * Handle changes to a Scene to determine whether to trigger changes to Playlist documents.
+   * @param {Scene} scene       The Scene document being updated
+   * @param {Object} data       The incremental update data
+   */
+  async _onChangeScene(scene, data) {
+    const currentScene = game.scenes.active;
+    const p0 = currentScene?.playlist;
+    const s0 = currentScene?.playlistSound;
+    const p1 = ("playlist" in data) ? game.playlists.get(data.playlist) : scene.playlist;
+    const s1 = "playlistSound" in data ? p1?.sounds.get(data.playlistSound) : scene.playlistSound;
+    const soundChange = (p0 !== p1) || (s0 !== s1);
+    if ( soundChange ) {
+      if ( s0 ) await s0.update({playing: false});
+      else if ( p0 ) await p0.stopAll();
+      if ( s1 ) await s1.update({playing: true});
+      else if ( p1 ) await p1.playAll();
+    }
+  }
+}