/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule NetInfo
 * @flow
 */
'use strict';

const Map = require('Map');
const NativeEventEmitter = require('NativeEventEmitter');
const NativeModules = require('NativeModules');
const Platform = require('Platform');
const RCTNetInfo = NativeModules.NetInfo;

const NetInfoEventEmitter = new NativeEventEmitter(RCTNetInfo);

const DEVICE_CONNECTIVITY_EVENT = 'networkStatusDidChange';

type ChangeEventName = $Enum<{
  connectionChange: string,
  change: string,
}>;

type ReachabilityStateIOS = $Enum<{
  cell: string,
  none: string,
  unknown: string,
  wifi: string,
}>;

type ConnectivityStateAndroid = $Enum<{
  NONE: string,
  MOBILE: string,
  WIFI: string,
  MOBILE_MMS: string,
  MOBILE_SUPL: string,
  MOBILE_DUN: string,
  MOBILE_HIPRI: string,
  WIMAX: string,
  BLUETOOTH: string,
  DUMMY: string,
  ETHERNET: string,
  MOBILE_FOTA: string,
  MOBILE_IMS: string,
  MOBILE_CBS: string,
  WIFI_P2P: string,
  MOBILE_IA: string,
  MOBILE_EMERGENCY: string,
  PROXY: string,
  VPN: string,
  UNKNOWN: string,
}>;


const _subscriptions = new Map();

let _isConnectedDeprecated;
if (Platform.OS === 'ios') {
  _isConnectedDeprecated = function(
    reachability: ReachabilityStateIOS,
  ): bool {
    return reachability !== 'none' && reachability !== 'unknown';
  };
} else if (Platform.OS === 'android') {
  _isConnectedDeprecated = function(
      connectionType: ConnectivityStateAndroid,
    ): bool {
    return connectionType !== 'NONE' && connectionType !== 'UNKNOWN';
  };
}

function _isConnected(connection) {
  return connection.type !== 'none' && connection.type !== 'unknown';
}

const _isConnectedSubscriptions = new Map();

/**
 * NetInfo exposes info about online/offline status.
 * 
 * See https://facebook.github.io/react-native/docs/netinfo.html
 */
const NetInfo = {
  /**
   * Adds an event handler.
   * 
   * See https://facebook.github.io/react-native/docs/netinfo.html#addeventlistener
   */
  addEventListener(
    eventName: ChangeEventName,
    handler: Function
  ): {remove: () => void} {
    let listener;
    if (eventName === 'connectionChange') {
      listener = NetInfoEventEmitter.addListener(
        DEVICE_CONNECTIVITY_EVENT,
        (appStateData) => {
          handler({
            type: appStateData.connectionType,
            effectiveType: appStateData.effectiveConnectionType
          });
        }
      );
    } else if (eventName === 'change') {
      console.warn('NetInfo\'s "change" event is deprecated. Listen to the "connectionChange" event instead.');

      listener = NetInfoEventEmitter.addListener(
        DEVICE_CONNECTIVITY_EVENT,
        (appStateData) => {
          handler(appStateData.network_info);
        }
      );
    } else {
      console.warn('Trying to subscribe to unknown event: "' + eventName + '"');
      return {
        remove: () => {}
      };
    }

    _subscriptions.set(handler, listener);
    return {
      remove: () => NetInfo.removeEventListener(eventName, handler)
    };
  },

  /**
   * Removes the listener for network status changes.
   * 
   * See https://facebook.github.io/react-native/docs/netinfo.html#removeeventlistener
   */
  removeEventListener(
    eventName: ChangeEventName,
    handler: Function
  ): void {
    const listener = _subscriptions.get(handler);
    if (!listener) {
      return;
    }
    listener.remove();
    _subscriptions.delete(handler);
  },

  /**
   * This function is deprecated. Use `getConnectionInfo` instead. 
   * Returns a promise that resolves with one of the deprecated connectivity
   * types:
   * 
   * The following connectivity types are deprecated. They're used by the
   * deprecated APIs `fetch` and the `change` event.
   *
   * iOS connectivity types (deprecated):
   * - `none` - device is offline
   * - `wifi` - device is online and connected via wifi, or is the iOS simulator
   * - `cell` - device is connected via Edge, 3G, WiMax, or LTE
   * - `unknown` - error case and the network status is unknown
   *
   * Android connectivity types (deprecated).
   * - `NONE` - device is offline
   * - `BLUETOOTH` - The Bluetooth data connection.
   * - `DUMMY` -  Dummy data connection.
   * - `ETHERNET` - The Ethernet data connection.
   * - `MOBILE` - The Mobile data connection.
   * - `MOBILE_DUN` - A DUN-specific Mobile data connection.
   * - `MOBILE_HIPRI` - A High Priority Mobile data connection.
   * - `MOBILE_MMS` - An MMS-specific Mobile data connection.
   * - `MOBILE_SUPL` -  A SUPL-specific Mobile data connection.
   * - `VPN` -  A virtual network using one or more native bearers. Requires 
   * API Level 21
   * - `WIFI` - The WIFI data connection.
   * - `WIMAX` -  The WiMAX data connection.
   * - `UNKNOWN` - Unknown data connection.
   *
   * The rest of the connectivity types are hidden by the Android API, but can 
   * be used if necessary.
   */
  fetch(): Promise<any> {
    console.warn('NetInfo.fetch() is deprecated. Use NetInfo.getConnectionInfo() instead.');
    return RCTNetInfo.getCurrentConnectivity().then(resp => resp.network_info);
  },

  /**
   * See https://facebook.github.io/react-native/docs/netinfo.html#getconnectioninfo
   */
  getConnectionInfo(): Promise<any> {
    return RCTNetInfo.getCurrentConnectivity().then(resp => {
      return {
        type: resp.connectionType,
        effectiveType: resp.effectiveConnectionType,
      };
    });
  },

  /**
   * An object with the same methods as above but the listener receives a
   * boolean which represents the internet connectivity.
   * 
   * See https://facebook.github.io/react-native/docs/netinfo.html#isconnected
   */
  isConnected: {
    addEventListener(
      eventName: ChangeEventName,
      handler: Function
    ): {remove: () => void} {
      const listener = (connection) => {
        if (eventName === 'change') {
          handler(_isConnectedDeprecated(connection));
        } else if (eventName === 'connectionChange') {
          handler(_isConnected(connection));
        }
      };
      _isConnectedSubscriptions.set(handler, listener);
      NetInfo.addEventListener(
        eventName,
        listener
      );
      return {
        remove: () => NetInfo.isConnected.removeEventListener(eventName, handler)
      };
    },

    removeEventListener(
      eventName: ChangeEventName,
      handler: Function
    ): void {
      const listener = _isConnectedSubscriptions.get(handler);
      NetInfo.removeEventListener(
        eventName,
        /* $FlowFixMe(>=0.36.0 site=react_native_fb,react_native_oss) Flow error
         * detected during the deploy of Flow v0.36.0. To see the error, remove
         * this comment and run Flow */
        listener
      );
      _isConnectedSubscriptions.delete(handler);
    },

    fetch(): Promise<any> {
      return NetInfo.getConnectionInfo().then(_isConnected);
    },
  },

  isConnectionExpensive(): Promise<boolean> {
    return (
      Platform.OS === 'android' ? RCTNetInfo.isConnectionMetered() : Promise.reject(new Error('Currently not supported on iOS'))
    );
  },
};

module.exports = NetInfo;