text: /*
   * Backpack - Skyscanner's Design System
   *
   * Copyright 2016-2021 Skyscanner Ltd
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  /* @flow */
  
  import { initialMode, eventEmitter } from 'react-native-dark-mode';
  
  export type ColorSchemeName = 'light' | 'dark';
  
  export type BpkAppearancePreferences = {
    colorScheme?: ColorSchemeName,
  };
  
  export type BpkAppearanceChangeListener = (BpkAppearancePreferences) => void;
  
  let currentPreferences: BpkAppearancePreferences = { colorScheme: initialMode };
  const listeners: Set<BpkAppearanceChangeListener> = new Set([]);
  
  const appearance = {
    get: () => currentPreferences,
    set: (preferences: BpkAppearancePreferences) => {
      if (currentPreferences.colorScheme !== preferences.colorScheme) {
        currentPreferences = preferences;
        listeners.forEach((listener) => listener(currentPreferences));
      }
    },
    addChangeListener: (listener: BpkAppearanceChangeListener) => {
      listeners.add(listener);
    },
    removeChangeListener: (listener: BpkAppearanceChangeListener) => {
      listeners.delete(listener);
    },
  };
  
  eventEmitter.on('currentModeChanged', (newMode) => {
    appearance.set({ ...currentPreferences, colorScheme: newMode });
  });
  
  export default appearance;
  