videojs-contrib-hls/src/rendition-mixin.js

import { isIncompatible, isEnabled } from './playlist.js';

/**
 * Returns a function that acts as the Enable/disable playlist function.
 *
 * @param {PlaylistLoader} loader - The master playlist loader
 * @param {String} playlistUri - uri of the playlist
 * @param {Function} changePlaylistFn - A function to be called after a
 * playlist's enabled-state has been changed. Will NOT be called if a
 * playlist's enabled-state is unchanged
 * @param {Boolean=} enable - Value to set the playlist enabled-state to
 * or if undefined returns the current enabled-state for the playlist
 * @return {Function} Function for setting/getting enabled
 */
const enableFunction = (loader, playlistUri, changePlaylistFn) => (enable) => {
  const playlist = loader.master.playlists[playlistUri];
  const incompatible = isIncompatible(playlist);
  const currentlyEnabled = isEnabled(playlist);

  if (typeof enable === 'undefined') {
    return currentlyEnabled;
  }

  if (enable) {
    delete playlist.disabled;
  } else {
    playlist.disabled = true;
  }

  if (enable !== currentlyEnabled && !incompatible) {
    // Ensure the outside world knows about our changes
    changePlaylistFn();
    if (enable) {
      loader.trigger('renditionenabled');
    } else {
      loader.trigger('renditiondisabled');
    }
  }
  return enable;
};

/**
 * The representation object encapsulates the publicly visible information
 * in a media playlist along with a setter/getter-type function (enabled)
 * for changing the enabled-state of a particular playlist entry
 *
 * @class Representation
 */
class Representation {
  constructor(hlsHandler, playlist, id) {
    // Get a reference to a bound version of fastQualityChange_
    let fastChangeFunction = hlsHandler
                              .masterPlaylistController_
                              .fastQualityChange_
                              .bind(hlsHandler.masterPlaylistController_);

    // some playlist attributes are optional
    if (playlist.attributes.RESOLUTION) {
      const resolution = playlist.attributes.RESOLUTION;

      this.width = resolution.width;
      this.height = resolution.height;
    }

    this.bandwidth = playlist.attributes.BANDWIDTH;

    // The id is simply the ordinality of the media playlist
    // within the master playlist
    this.id = id;

    // Partially-apply the enableFunction to create a playlist-
    // specific variant
    this.enabled = enableFunction(hlsHandler.playlists,
                                  playlist.uri,
                                  fastChangeFunction);
  }
}

/**
 * A mixin function that adds the `representations` api to an instance
 * of the HlsHandler class
 * @param {HlsHandler} hlsHandler - An instance of HlsHandler to add the
 * representation API into
 */
let renditionSelectionMixin = function(hlsHandler) {
  let playlists = hlsHandler.playlists;

  // Add a single API-specific function to the HlsHandler instance
  hlsHandler.representations = () => {
    return playlists
      .master
      .playlists
      .filter((media) => !isIncompatible(media))
      .map((e, i) => new Representation(hlsHandler, e, e.uri));
  };
};

export default renditionSelectionMixin;