/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 * @flow
 */

'use strict';

const Promise = require('../../Promise');
const RCTDeviceEventEmitter = require('../../EventEmitter/RCTDeviceEventEmitter');

import NativeAccessibilityManager from './NativeAccessibilityManager';

const CHANGE_EVENT_NAME = {
  announcementFinished: 'announcementFinished',
  boldTextChanged: 'boldTextChanged',
  grayscaleChanged: 'grayscaleChanged',
  invertColorsChanged: 'invertColorsChanged',
  reduceMotionChanged: 'reduceMotionChanged',
  reduceTransparencyChanged: 'reduceTransparencyChanged',
  screenReaderChanged: 'screenReaderChanged',
};

type ChangeEventName = $Keys<{
  announcementFinished: string,
  boldTextChanged: string,
  change: string,
  grayscaleChanged: string,
  invertColorsChanged: string,
  reduceMotionChanged: string,
  reduceTransparencyChanged: string,
  screenReaderChanged: string,
  ...
}>;

const _subscriptions = new Map();

/**
 * Sometimes it's useful to know whether or not the device has a screen reader
 * that is currently active. The `AccessibilityInfo` API is designed for this
 * purpose. You can use it to query the current state of the screen reader as
 * well as to register to be notified when the state of the screen reader
 * changes.
 *
 * See https://reactnative.dev/docs/accessibilityinfo.html
 */
const AccessibilityInfo = {
  /**
   * Query whether bold text is currently enabled.
   *
   * Returns a promise which resolves to a boolean.
   * The result is `true` when bold text is enabled and `false` otherwise.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#isBoldTextEnabled
   */
  isBoldTextEnabled: function(): Promise<boolean> {
    return new Promise((resolve, reject) => {
      if (NativeAccessibilityManager) {
        NativeAccessibilityManager.getCurrentBoldTextState(resolve, reject);
      } else {
        reject(reject);
      }
    });
  },

  /**
   * Query whether grayscale is currently enabled.
   *
   * Returns a promise which resolves to a boolean.
   * The result is `true` when grayscale is enabled and `false` otherwise.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#isGrayscaleEnabled
   */
  isGrayscaleEnabled: function(): Promise<boolean> {
    return new Promise((resolve, reject) => {
      if (NativeAccessibilityManager) {
        NativeAccessibilityManager.getCurrentGrayscaleState(resolve, reject);
      } else {
        reject(reject);
      }
    });
  },

  /**
   * Query whether inverted colors are currently enabled.
   *
   * Returns a promise which resolves to a boolean.
   * The result is `true` when invert color is enabled and `false` otherwise.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#isInvertColorsEnabled
   */
  isInvertColorsEnabled: function(): Promise<boolean> {
    return new Promise((resolve, reject) => {
      if (NativeAccessibilityManager) {
        NativeAccessibilityManager.getCurrentInvertColorsState(resolve, reject);
      } else {
        reject(reject);
      }
    });
  },

  /**
   * Query whether reduced motion is currently enabled.
   *
   * Returns a promise which resolves to a boolean.
   * The result is `true` when a reduce motion is enabled and `false` otherwise.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#isReduceMotionEnabled
   */
  isReduceMotionEnabled: function(): Promise<boolean> {
    return new Promise((resolve, reject) => {
      if (NativeAccessibilityManager) {
        NativeAccessibilityManager.getCurrentReduceMotionState(resolve, reject);
      } else {
        reject(reject);
      }
    });
  },

  /**
   * Query whether reduced transparency is currently enabled.
   *
   * Returns a promise which resolves to a boolean.
   * The result is `true` when a reduce transparency is enabled and `false` otherwise.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#isReduceTransparencyEnabled
   */
  isReduceTransparencyEnabled: function(): Promise<boolean> {
    return new Promise((resolve, reject) => {
      if (NativeAccessibilityManager) {
        NativeAccessibilityManager.getCurrentReduceTransparencyState(
          resolve,
          reject,
        );
      } else {
        reject(reject);
      }
    });
  },

  /**
   * Query whether a screen reader is currently enabled.
   *
   * Returns a promise which resolves to a boolean.
   * The result is `true` when a screen reader is enabled and `false` otherwise.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#isScreenReaderEnabled
   */
  isScreenReaderEnabled: function(): Promise<boolean> {
    return new Promise((resolve, reject) => {
      if (NativeAccessibilityManager) {
        NativeAccessibilityManager.getCurrentVoiceOverState(resolve, reject);
      } else {
        reject(reject);
      }
    });
  },

  /**
   * Deprecated
   *
   * Same as `isScreenReaderEnabled`
   */
  get fetch(): $FlowFixMe {
    console.warn(
      'AccessibilityInfo.fetch is deprecated, call AccessibilityInfo.isScreenReaderEnabled instead',
    );
    return this.isScreenReaderEnabled;
  },

  /**
   * Add an event handler. Supported events:
   *
   * - `boldTextChanged`: iOS-only event. Fires when the state of the bold text toggle changes.
   *   The argument to the event handler is a boolean. The boolean is `true` when a bold text
   *   is enabled and `false` otherwise.
   * - `grayscaleChanged`: iOS-only event. Fires when the state of the gray scale toggle changes.
   *   The argument to the event handler is a boolean. The boolean is `true` when a gray scale
   *   is enabled and `false` otherwise.
   * - `invertColorsChanged`: iOS-only event. Fires when the state of the invert colors toggle
   *   changes. The argument to the event handler is a boolean. The boolean is `true` when a invert
   *   colors is enabled and `false` otherwise.
   * - `reduceMotionChanged`: Fires when the state of the reduce motion toggle changes.
   *   The argument to the event handler is a boolean. The boolean is `true` when a reduce
   *   motion is enabled (or when "Transition Animation Scale" in "Developer options" is
   *   "Animation off") and `false` otherwise.
   * - `reduceTransparencyChanged`: iOS-only event. Fires when the state of the reduce transparency
   *   toggle changes.  The argument to the event handler is a boolean. The boolean is `true`
   *   when a reduce transparency is enabled and `false` otherwise.
   * - `screenReaderChanged`: Fires when the state of the screen reader changes. The argument
   *   to the event handler is a boolean. The boolean is `true` when a screen
   *   reader is enabled and `false` otherwise.
   * - `announcementFinished`: iOS-only event. Fires when the screen reader has
   *   finished making an announcement. The argument to the event handler is a
   *   dictionary with these keys:
   *     - `announcement`: The string announced by the screen reader.
   *     - `success`: A boolean indicating whether the announcement was
   *       successfully made.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#addeventlistener
   */
  addEventListener: function(
    eventName: ChangeEventName,
    handler: Function,
  ): Object {
    let listener;

    if (eventName === 'change') {
      listener = RCTDeviceEventEmitter.addListener(
        CHANGE_EVENT_NAME.screenReaderChanged,
        handler,
      );
    } else if (CHANGE_EVENT_NAME[eventName]) {
      listener = RCTDeviceEventEmitter.addListener(eventName, handler);
    }

    _subscriptions.set(handler, listener);
    return {
      remove: AccessibilityInfo.removeEventListener.bind(
        null,
        eventName,
        handler,
      ),
    };
  },

  /**
   * Set accessibility focus to a react component.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#setaccessibilityfocus
   */
  setAccessibilityFocus: function(reactTag: number): void {
    if (NativeAccessibilityManager) {
      NativeAccessibilityManager.setAccessibilityFocus(reactTag);
    }
  },

  /**
   * Post a string to be announced by the screen reader.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#announceforaccessibility
   */
  announceForAccessibility: function(announcement: string): void {
    if (NativeAccessibilityManager) {
      NativeAccessibilityManager.announceForAccessibility(announcement);
    }
  },

  /**
   * Remove an event handler.
   *
   * See https://reactnative.dev/docs/accessibilityinfo.html#removeeventlistener
   */
  removeEventListener: function(
    eventName: ChangeEventName,
    handler: Function,
  ): void {
    const listener = _subscriptions.get(handler);
    if (!listener) {
      return;
    }
    listener.remove();
    _subscriptions.delete(handler);
  },
};

module.exports = AccessibilityInfo;