/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// Holds optional fallback theme data that will be returned when no data for an
// active theme can be found. This the case for WebExtension Themes, for example.
var _fallbackThemeData = null;

export var LightweightThemeManager = {
  set fallbackThemeData(data) {
    if (data && Object.getOwnPropertyNames(data).length) {
      _fallbackThemeData = Object.assign({}, data);
    } else {
      _fallbackThemeData = null;
    }
  },

  /*
   * Returns the currently active theme, taking the fallback theme into account
   * if we'd be using the default theme otherwise.
   *
   * This will always return the original theme data and not make use of
   * locally persisted resources.
   */
  get currentThemeWithFallback() {
    return _fallbackThemeData && _fallbackThemeData.theme;
  },

  get themeData() {
    return _fallbackThemeData || { theme: null };
  },
};