/*
 *   Famedly
 *   Copyright (C) 2020, 2021 Famedly GmbH
 *   Copyright (C) 2021 Fluffychat
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU Affero General Public License as
 *   published by the Free Software Foundation, either version 3 of the
 *   License, or (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *   GNU Affero General Public License for more details.
 *
 *   You should have received a copy of the GNU Affero General Public License
 *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:ui';

import 'package:flutter_cache_manager/flutter_cache_manager.dart';
import 'package:matrix/matrix.dart';
import 'package:fcm_shared_isolate/fcm_shared_isolate.dart';

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:unifiedpush/unifiedpush.dart';
import 'package:flutter_gen/gen_l10n/l10n.dart';
import 'package:flutter_gen/gen_l10n/l10n_en.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:vrouter/vrouter.dart';
import 'platform_infos.dart';
import '../config/app_config.dart';
import '../config/setting_keys.dart';
import 'famedlysdk_store.dart';
import 'matrix_sdk_extensions.dart/matrix_locals.dart';

class NoTokenException implements Exception {
  String get cause => 'Cannot get firebase token';
}

class BackgroundPush {
  static BackgroundPush _instance;
  final FlutterLocalNotificationsPlugin _flutterLocalNotificationsPlugin =
      FlutterLocalNotificationsPlugin();
  Client client;
  BuildContext context;
  GlobalKey<VRouterState> router;
  String _fcmToken;
  LoginState _loginState;
  void Function(String errorMsg) onFcmError;
  L10n l10n;
  Store _store;
  Store get store => _store ??= Store();
  Future<void> loadLocale() async {
    // inspired by _lookupL10n in .dart_tool/flutter_gen/gen_l10n/l10n.dart
    l10n ??= (context != null ? L10n.of(context) : null) ??
        (await L10n.delegate.load(window.locale)) ??
        L10nEn();
  }

  final pendingTests = <String, Completer<void>>{};

  DateTime lastReceivedPush;

  BackgroundPush._(this.client, {this.onFcmError}) {
    onLogin ??=
        client.onLoginStateChanged.stream.listen(handleLoginStateChanged);
    onRoomSync ??= client.onSync.stream
        .where((s) => s.hasRoomUpdate)
        .listen((s) => _onClearingPush(getFromServer: false));
    _fcmSharedIsolate.setListeners(
      onMessage: _onFcmMessage,
      onNewToken: _newFcmToken,
    );
    if (Platform.isAndroid) {
      UnifiedPush.initializeWithReceiver(
        onNewEndpoint: _newUpEndpoint,
        onRegistrationFailed: _upUnregistered,
        onRegistrationRefused: _upUnregistered,
        onUnregistered: _upUnregistered,
        onMessage: _onUpMessage,
      );
    }
  }

  factory BackgroundPush.clientOnly(Client client) {
    _instance ??= BackgroundPush._(client);
    return _instance;
  }

  factory BackgroundPush(
      Client _client, BuildContext _context, GlobalKey<VRouterState> router,
      {final void Function(String errorMsg) onFcmError}) {
    final instance = BackgroundPush.clientOnly(_client);
    instance.context = _context;
    instance.router = router;
    instance.onFcmError = onFcmError;
    instance.fullInit();
    return instance;
  }

  Future<void> fullInit() async {
    await setupPush();
  }

  void handleLoginStateChanged(LoginState state) {
    _loginState = state;
    setupPush();
  }

  void _newFcmToken(String token) {
    _fcmToken = token;
    setupPush();
  }

  final _fcmSharedIsolate = FcmSharedIsolate();

  StreamSubscription<LoginState> onLogin;
  StreamSubscription<SyncUpdate> onRoomSync;

  Future<void> setupPusher({
    String gatewayUrl,
    String token,
    Set<String> oldTokens,
    bool useDeviceSpecificAppId = false,
  }) async {
    if (PlatformInfos.isIOS) {
      await _fcmSharedIsolate.requestPermission();
    }
    final clientName = PlatformInfos.clientName;
    oldTokens ??= <String>{};
    final pushers = await client.getPushers().catchError((e) {
      Logs().w('[Push] Unable to request pushers', e);
      return <Pusher>[];
    });
    var setNewPusher = false;
    // Just the plain app id, we add the .data_message suffix later
    var appId = AppConfig.pushNotificationsAppId;
    // we need the deviceAppId to remove potential legacy UP pusher
    var deviceAppId = '$appId.${client.deviceID}';
    // appId may only be up to 64 chars as per spec
    if (deviceAppId.length > 64) {
      deviceAppId = deviceAppId.substring(0, 64);
    }
    if (!useDeviceSpecificAppId && PlatformInfos.isAndroid) {
      appId += '.data_message';
    }
    final thisAppId = useDeviceSpecificAppId ? deviceAppId : appId;
    if (gatewayUrl != null && token != null && clientName != null) {
      final currentPushers = pushers.where((pusher) => pusher.pushkey == token);
      if (currentPushers.length == 1 &&
          currentPushers.first.kind == 'http' &&
          currentPushers.first.appId == thisAppId &&
          currentPushers.first.appDisplayName == clientName &&
          currentPushers.first.deviceDisplayName == client.deviceName &&
          currentPushers.first.lang == 'en' &&
          currentPushers.first.data.url.toString() == gatewayUrl &&
          currentPushers.first.data.format ==
              AppConfig.pushNotificationsPusherFormat) {
        Logs().i('[Push] Pusher already set');
      } else {
        Logs().i('Need to set new pusher');
        oldTokens.add(token);
        if (client.isLogged()) {
          setNewPusher = true;
        }
      }
    } else {
      Logs().w('[Push] Missing required push credentials');
    }
    for (final pusher in pushers) {
      if ((token != null &&
              pusher.pushkey != token &&
              deviceAppId == pusher.appId) ||
          oldTokens.contains(pusher.pushkey)) {
        pusher.kind = null;
        try {
          await client.postPusher(
            pusher,
            append: true,
          );
          Logs().i('[Push] Removed legacy pusher for this device');
        } catch (err) {
          Logs().w('[Push] Failed to remove old pusher', err);
        }
      }
    }
    if (setNewPusher) {
      try {
        await client.postPusher(
          Pusher(
            pushkey: token,
            appId: thisAppId,
            appDisplayName: clientName,
            deviceDisplayName: client.deviceName,
            lang: 'en',
            data: PusherData(
              url: Uri.parse(gatewayUrl),
              format: AppConfig.pushNotificationsPusherFormat,
            ),
            kind: 'http',
          ),
          append: false,
        );
      } catch (e, s) {
        Logs().e('[Push] Unable to set pushers', e, s);
      }
    }
  }

  bool _wentToRoomOnStartup = false;

  Future<void> setupPush() async {
    await setupLocalNotificationsPlugin();
    if (_loginState != LoginState.loggedIn ||
        !PlatformInfos.isMobile ||
        context == null) {
      return;
    }
    if (!PlatformInfos.isIOS &&
        (await UnifiedPush.getDistributors()).isNotEmpty) {
      await setupUp();
    } else {
      await setupFirebase();
    }

    // ignore: unawaited_futures
    _flutterLocalNotificationsPlugin
        .getNotificationAppLaunchDetails()
        .then((details) {
      if (details == null ||
          !details.didNotificationLaunchApp ||
          _wentToRoomOnStartup ||
          router == null) {
        return;
      }
      _wentToRoomOnStartup = true;
      goToRoom(details.payload);
    });
  }

  Future<void> _noFcmWarning() async {
    if (context == null) {
      return;
    }
    if (await store.getItemBool(SettingKeys.showNoGoogle, true)) {
      await loadLocale();
      onFcmError?.call(PlatformInfos.isAndroid
          ? l10n.noGoogleServicesWarning
          : l10n.oopsPushError);

      if (null == await store.getItem(SettingKeys.showNoGoogle)) {
        await store.setItemBool(SettingKeys.showNoGoogle, false);
      }
    }
  }

  Future<void> setupFirebase() async {
    Logs().v('Setup firebase');
    if (_fcmToken?.isEmpty ?? true) {
      try {
        _fcmToken = await _fcmSharedIsolate.getToken();
      } catch (e, s) {
        Logs().e('[Push] cannot get token', e, s);
        await _noFcmWarning();
        return;
      }
    }
    await setupPusher(
      gatewayUrl: AppConfig.pushNotificationsGatewayUrl,
      token: _fcmToken,
    );
  }

  Future<void> goToRoom(String roomId) async {
    try {
      Logs().v('[Push] Attempting to go to room $roomId...');
      if (router == null) {
        return;
      }
      router.currentState.toSegments(['rooms', roomId]);
    } catch (e, s) {
      Logs().e('[Push] Failed to open room', e, s);
    }
  }

  bool _notificationsPluginSetUp = false;
  Future<void> setupLocalNotificationsPlugin() async {
    if (_notificationsPluginSetUp) {
      return;
    }

    // initialise the plugin. app_icon needs to be a added as a drawable resource to the Android head project
    final initializationSettingsAndroid =
        AndroidInitializationSettings('notifications_icon');
    final initializationSettingsIOS =
        IOSInitializationSettings(onDidReceiveLocalNotification: (i, a, b, c) {
      return null;
    });
    final initializationSettings = InitializationSettings(
      android: initializationSettingsAndroid,
      iOS: initializationSettingsIOS,
    );
    await _flutterLocalNotificationsPlugin.initialize(initializationSettings,
        onSelectNotification: goToRoom);

    _notificationsPluginSetUp = true;
  }

  Future<void> setupUp() async {
    await UnifiedPush.registerAppWithDialog();
  }

  Future<void> _onFcmMessage(Map<dynamic, dynamic> message) async {
    Logs().v('[Push] Foreground message received');
    Map<String, dynamic> data;
    try {
      data = Map<String, dynamic>.from(message['data'] ?? message);
      await _onMessage(data);
    } catch (e, s) {
      Logs().e('[Push] Error while processing notification', e, s);
      await _showDefaultNotification(data);
    }
  }

  Future<void> _newUpEndpoint(String newEndpoint) async {
    if (newEndpoint?.isEmpty ?? true) {
      await _upUnregistered();
      return;
    }
    var endpoint =
        'https://matrix.gateway.unifiedpush.org/_matrix/push/v1/notify';
    try {
      final url = Uri.parse(newEndpoint)
          .replace(
            path: '/_matrix/push/v1/notify',
            query: '',
          )
          .toString()
          .split('?')
          .first;
      final res =
          json.decode(utf8.decode((await http.get(Uri.parse(url))).bodyBytes));
      if (res['gateway'] == 'matrix' ||
          (res['unifiedpush'] is Map &&
              res['unifiedpush']['gateway'] == 'matrix')) {
        endpoint = url;
      }
    } catch (e) {
      Logs().i(
          '[Push] No self-hosted unified push gateway present: ' + newEndpoint);
    }
    Logs().i('[Push] UnifiedPush using endpoint ' + endpoint);
    final oldTokens = <String>{};
    try {
      final fcmToken = await _fcmSharedIsolate.getToken();
      oldTokens.add(fcmToken);
    } catch (_) {}
    await setupPusher(
      gatewayUrl: endpoint,
      token: newEndpoint,
      oldTokens: oldTokens,
      useDeviceSpecificAppId: true,
    );
    await store.setItem(SettingKeys.unifiedPushEndpoint, newEndpoint);
    await store.setItemBool(SettingKeys.unifiedPushRegistered, true);
  }

  Future<void> _upUnregistered() async {
    Logs().i('[Push] Removing UnifiedPush endpoint...');
    final oldEndpoint = await store.getItem(SettingKeys.unifiedPushEndpoint);
    await store.setItemBool(SettingKeys.unifiedPushRegistered, false);
    await store.deleteItem(SettingKeys.unifiedPushEndpoint);
    if (oldEndpoint?.isNotEmpty ?? false) {
      // remove the old pusher
      await setupPusher(
        oldTokens: {oldEndpoint},
      );
    }
  }

  Future<void> _onUpMessage(String message) async {
    Map<String, dynamic> data;
    try {
      data = Map<String, dynamic>.from(json.decode(message)['notification']);
      await _onMessage(data);
    } catch (e, s) {
      Logs().e('[Push] Error while processing notification', e, s);
      await _showDefaultNotification(data);
    }
  }

  Future<void> _onMessage(Map<String, dynamic> data) async {
    Logs().v('[Push] _onMessage');
    lastReceivedPush = DateTime.now();
    final roomId = data['room_id'];
    final eventId = data['event_id'];
    if (roomId == 'test') {
      Logs().v('[Push] Test $eventId was successful!');
      pendingTests.remove(eventId)?.complete();
      return;
    }
    final unread = ((data['counts'] is String
            ? json
                .decode(data.tryGet<String>('counts', TryGet.optional) ?? '{}')
            : data.tryGet<Map<String, dynamic>>('counts', TryGet.optional) ??
                <String, dynamic>{}) as Map<String, dynamic>)
        .tryGet<int>('unread');
    if ((roomId?.isEmpty ?? true) ||
        (eventId?.isEmpty ?? true) ||
        unread == 0) {
      await _onClearingPush();
      return;
    }
    var giveUp = false;
    var loaded = false;
    final stopwatch = Stopwatch();
    stopwatch.start();
    final syncSubscription = client.onSync.stream.listen((r) {
      if (stopwatch.elapsed.inSeconds >= 30) {
        giveUp = true;
      }
    });
    final eventSubscription = client.onEvent.stream.listen((e) {
      if (e.content['event_id'] == eventId) {
        loaded = true;
      }
    });
    try {
      if (!(await eventExists(roomId, eventId)) && !loaded) {
        do {
          Logs().v('[Push] getting ' + roomId + ', event ' + eventId);
          await client
              .oneShotSync()
              .catchError((e) => Logs().v('[Push] Error one-shot syncing', e));
          if (stopwatch.elapsed.inSeconds >= 60) {
            giveUp = true;
          }
        } while (!loaded && !giveUp);
      }
      Logs().v('[Push] ' +
          (giveUp ? 'gave up on ' : 'got ') +
          roomId +
          ', event ' +
          eventId);
    } finally {
      await syncSubscription.cancel();
      await eventSubscription.cancel();
    }
    await _showNotification(roomId, eventId);
  }

  Future<bool> eventExists(String roomId, String eventId) async {
    final room = client.getRoomById(roomId);
    if (room == null) return false;
    return (await client.database.getEventById(client.id, eventId, room)) !=
        null;
  }

  /// Workaround for the problem that local notification IDs must be int but we
  /// sort by [roomId] which is a String. To make sure that we don't have duplicated
  /// IDs we map the [roomId] to a number and store this number.
  Map<String, int> idMap;
  Future<void> _loadIdMap() async {
    idMap ??= Map<String, int>.from(json.decode(
        (await store.getItem(SettingKeys.notificationCurrentIds)) ?? '{}'));
  }

  Future<int> mapRoomIdToInt(String roomId) async {
    await _loadIdMap();
    int currentInt;
    try {
      currentInt = idMap[roomId];
    } catch (_) {
      currentInt = null;
    }
    if (currentInt != null) {
      return currentInt;
    }
    currentInt = 0;
    while (idMap.values.contains(currentInt)) {
      currentInt++;
    }
    idMap[roomId] = currentInt;
    await store.setItem(SettingKeys.notificationCurrentIds, json.encode(idMap));
    return currentInt;
  }

  bool _clearingPushLock = false;
  Future<void> _onClearingPush({bool getFromServer = true}) async {
    if (_clearingPushLock) {
      return;
    }
    try {
      _clearingPushLock = true;
      Iterable<String> emptyRooms;
      if (getFromServer) {
        Logs().v('[Push] Got new clearing push');
        var syncErrored = false;
        if (client.syncPending) {
          Logs().v('[Push] waiting for existing sync');
          // we need to catchError here as the Future might be in a different execution zone
          await client.oneShotSync().catchError((e) {
            syncErrored = true;
            Logs().v('[Push] Error one-shot syncing', e);
          });
        }
        if (!syncErrored) {
          Logs().v('[Push] single oneShotSync');
          // we need to catchError here as the Future might be in a different execution zone
          await client.oneShotSync().catchError((e) {
            syncErrored = true;
            Logs().v('[Push] Error one-shot syncing', e);
          });
          if (!syncErrored) {
            emptyRooms = client.rooms
                .where((r) =>
                    r.notificationCount == 0 || r.notificationCount == null)
                .map((r) => r.id);
          }
        }
        if (syncErrored) {
          try {
            Logs().v(
                '[Push] failed to sync for fallback push, fetching notifications endpoint...');
            final notifications = await client.getNotifications(limit: 20);
            final notificationRooms =
                notifications.notifications.map((n) => n.roomId).toSet();
            emptyRooms = client.rooms
                .where((r) => !notificationRooms.contains(r.id))
                .map((r) => r.id);
          } catch (e) {
            Logs().v(
                '[Push] failed to fetch pending notifications for clearing push, falling back...',
                e);
            emptyRooms = client.rooms
                .where((r) =>
                    r.notificationCount == 0 || r.notificationCount == null)
                .map((r) => r.id);
          }
        }
      } else {
        emptyRooms = client.rooms
            .where(
                (r) => r.notificationCount == 0 || r.notificationCount == null)
            .map((r) => r.id);
      }
      await _loadIdMap();
      var changed = false;
      for (final roomId in emptyRooms) {
        if (idMap[roomId] != null) {
          final id = idMap[roomId];
          idMap.remove(roomId);
          changed = true;
          await _flutterLocalNotificationsPlugin?.cancel(id);
        }
      }
      if (changed) {
        await store.setItem(
            SettingKeys.notificationCurrentIds, json.encode(idMap));
      }
    } finally {
      _clearingPushLock = false;
    }
  }

  Future<void> _showNotification(String roomId, String eventId) async {
    await setupLocalNotificationsPlugin();
    final room = client.getRoomById(roomId);
    if (room == null) {
      throw 'Room not found';
    }
    await room.postLoad();
    final event = await client.database.getEventById(client.id, eventId, room);

    final activeRoomId = router.currentState.pathParameters['roomid'];

    if (((activeRoomId?.isNotEmpty ?? false) &&
            activeRoomId == room.id &&
            client.syncPresence == null) ||
        (event != null &&
            (room.notificationCount == 0 || room.notificationCount == null))) {
      return;
    }

    // load the locale
    await loadLocale();

    // Count all unread events
    var unreadEvents = 0;
    client.rooms
        .forEach((Room room) => unreadEvents += room.notificationCount ?? 0);

    // Calculate title
    final title = l10n.unreadMessages(room.notificationCount ?? 0);

    // Calculate the body
    final body = event.getLocalizedBody(
      MatrixLocals(L10n.of(context)),
      withSenderNamePrefix: !room.isDirectChat,
      plaintextBody: true,
      hideReply: true,
      hideEdit: true,
    );

    // The person object for the android message style notification
    final avatar = room.avatar == null
        ? null
        : await DefaultCacheManager().getSingleFile(
            event.room.avatar
                .getThumbnail(
                  client,
                  width: 126,
                  height: 126,
                )
                .toString(),
          );
    final person = Person(
      name: room.getLocalizedDisplayname(MatrixLocals(l10n)),
      icon: avatar == null ? null : BitmapFilePathAndroidIcon(avatar.path),
    );

    // Show notification
    final androidPlatformChannelSpecifics = _getAndroidNotificationDetails(
      styleInformation: MessagingStyleInformation(
        person,
        conversationTitle: title,
        messages: [
          Message(
            body,
            event?.originServerTs ?? DateTime.now(),
            person,
          )
        ],
      ),
      ticker: l10n.newMessageInFluffyChat,
    );
    final iOSPlatformChannelSpecifics = IOSNotificationDetails();
    final platformChannelSpecifics = NotificationDetails(
      android: androidPlatformChannelSpecifics,
      iOS: iOSPlatformChannelSpecifics,
    );
    await _flutterLocalNotificationsPlugin.show(
      await mapRoomIdToInt(room.id),
      room.getLocalizedDisplayname(MatrixLocals(l10n)),
      body,
      platformChannelSpecifics,
      payload: roomId,
    );
  }

  Future<dynamic> _showDefaultNotification(Map<String, dynamic> data) async {
    try {
      await setupLocalNotificationsPlugin();

      await loadLocale();
      final String eventId = data['event_id'];
      final String roomId = data['room_id'];
      final unread = ((data['counts'] is String
                  ? json.decode(
                      data.tryGet<String>('counts', TryGet.optional) ?? '{}')
                  : data.tryGet<Map<String, dynamic>>(
                          'counts', TryGet.optional) ??
                      <String, dynamic>{}) as Map<String, dynamic>)
              .tryGet<int>('unread', TryGet.optional) ??
          1;
      if (unread == 0 || roomId == null || eventId == null) {
        await _onClearingPush();
        return;
      }

      // Display notification
      final androidPlatformChannelSpecifics = _getAndroidNotificationDetails();
      final iOSPlatformChannelSpecifics = IOSNotificationDetails();
      final platformChannelSpecifics = NotificationDetails(
        android: androidPlatformChannelSpecifics,
        iOS: iOSPlatformChannelSpecifics,
      );
      final title = l10n.unreadChats(unread);
      await _flutterLocalNotificationsPlugin.show(
        await mapRoomIdToInt(roomId),
        title,
        l10n.openAppToReadMessages,
        platformChannelSpecifics,
        payload: roomId,
      );
    } catch (e, s) {
      Logs().e('[Push] Error while processing background notification', e, s);
    }
  }

  AndroidNotificationDetails _getAndroidNotificationDetails(
      {MessagingStyleInformation styleInformation, String ticker}) {
    final color = (context != null ? Theme.of(context).primaryColor : null) ??
        Color(0xFF5625BA);

    return AndroidNotificationDetails(
      AppConfig.pushNotificationsChannelId,
      AppConfig.pushNotificationsChannelName,
      AppConfig.pushNotificationsChannelDescription,
      styleInformation: styleInformation,
      importance: Importance.max,
      priority: Priority.high,
      ticker: ticker,
      color: color,
    );
  }
}