famedlysdk/lib/src/event.dart

/*
 * Copyright (c) 2019 Zender & Kurtz GbR.
 *
 * Authors:
 *   Christian Pauly <krille@famedly.com>
 *   Marcel Radzio <mtrnord@famedly.com>
 *
 * This file is part of famedlysdk.
 *
 * famedlysdk is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * famedlysdk 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with famedlysdk.  If not, see <http://www.gnu.org/licenses/>.
 */

import 'dart:convert';
import 'dart:typed_data';
import 'package:famedlysdk/famedlysdk.dart';
import 'package:famedlysdk/src/utils/receipt.dart';
import 'package:http/http.dart' as http;
import 'package:matrix_file_e2ee/matrix_file_e2ee.dart';
import './room.dart';

/// All data exchanged over Matrix is expressed as an "event". Typically each client action (e.g. sending a message) correlates with exactly one event.
class Event {
  /// The Matrix ID for this event in the format '$localpart:server.abc'. Please not
  /// that account data, presence and other events may not have an eventId.
  final String eventId;

  /// The json payload of the content. The content highly depends on the type.
  Map<String, dynamic> content;

  /// The type String of this event. For example 'm.room.message'.
  final String typeKey;

  /// The ID of the room this event belongs to.
  final String roomId;

  /// The user who has sent this event if it is not a global account data event.
  final String senderId;

  User get sender => room.getUserByMXIDSync(senderId ?? '@unknown');

  /// The time this event has received at the server. May be null for events like
  /// account data.
  final DateTime time;

  /// Optional additional content for this event.
  Map<String, dynamic> unsigned;

  /// The room this event belongs to. May be null.
  final Room room;

  /// Optional. The previous content for this state.
  /// This will be present only for state events appearing in the timeline.
  /// If this is not a state event, or there is no previous content, this key will be null.
  Map<String, dynamic> prevContent;

  /// Optional. This key will only be present for state events. A unique key which defines
  /// the overwriting semantics for this piece of room state.
  final String stateKey;

  /// The status of this event.
  /// -1=ERROR
  ///  0=SENDING
  ///  1=SENT
  ///  2=TIMELINE
  ///  3=ROOM_STATE
  int status;

  static const int defaultStatus = 2;
  static const Map<String, int> STATUS_TYPE = {
    'ERROR': -1,
    'SENDING': 0,
    'SENT': 1,
    'TIMELINE': 2,
    'ROOM_STATE': 3,
  };

  /// Optional. The event that redacted this event, if any. Otherwise null.
  Event get redactedBecause =>
      unsigned != null && unsigned.containsKey('redacted_because')
          ? Event.fromJson(unsigned['redacted_because'], room)
          : null;

  bool get redacted => redactedBecause != null;

  User get stateKeyUser => room.getUserByMXIDSync(stateKey);

  Event(
      {this.status = defaultStatus,
      this.content,
      this.typeKey,
      this.eventId,
      this.roomId,
      this.senderId,
      this.time,
      this.unsigned,
      this.prevContent,
      this.stateKey,
      this.room});

  static Map<String, dynamic> getMapFromPayload(dynamic payload) {
    if (payload is String) {
      try {
        return json.decode(payload);
      } catch (e) {
        return {};
      }
    }
    if (payload is Map<String, dynamic>) return payload;
    return {};
  }

  /// Get a State event from a table row or from the event stream.
  factory Event.fromJson(Map<String, dynamic> jsonPayload, Room room) {
    final content = Event.getMapFromPayload(jsonPayload['content']);
    final unsigned = Event.getMapFromPayload(jsonPayload['unsigned']);
    final prevContent = Event.getMapFromPayload(jsonPayload['prev_content']);
    return Event(
      status: jsonPayload['status'] ?? defaultStatus,
      stateKey: jsonPayload['state_key'],
      prevContent: prevContent,
      content: content,
      typeKey: jsonPayload['type'],
      eventId: jsonPayload['event_id'],
      roomId: jsonPayload['room_id'],
      senderId: jsonPayload['sender'],
      time: jsonPayload.containsKey('origin_server_ts')
          ? DateTime.fromMillisecondsSinceEpoch(jsonPayload['origin_server_ts'])
          : DateTime.now(),
      unsigned: unsigned,
      room: room,
    );
  }

  Map<String, dynamic> toJson() {
    final data = <String, dynamic>{};
    if (stateKey != null) data['state_key'] = stateKey;
    if (prevContent != null && prevContent.isNotEmpty) {
      data['prev_content'] = prevContent;
    }
    data['content'] = content;
    data['type'] = typeKey;
    data['event_id'] = eventId;
    data['room_id'] = roomId;
    data['sender'] = senderId;
    data['origin_server_ts'] = time.millisecondsSinceEpoch;
    if (unsigned != null && unsigned.isNotEmpty) {
      data['unsigned'] = unsigned;
    }
    return data;
  }

  /// The unique key of this event. For events with a [stateKey], it will be the
  /// stateKey. Otherwise it will be the [type] as a string.
  @deprecated
  String get key => stateKey == null || stateKey.isEmpty ? typeKey : stateKey;

  User get asUser => User.fromState(
      stateKey: stateKey,
      prevContent: prevContent,
      content: content,
      typeKey: typeKey,
      eventId: eventId,
      roomId: roomId,
      senderId: senderId,
      time: time,
      unsigned: unsigned,
      room: room);

  /// Get the real type.
  EventTypes get type {
    switch (typeKey) {
      case 'm.room.avatar':
        return EventTypes.RoomAvatar;
      case 'm.room.name':
        return EventTypes.RoomName;
      case 'm.room.topic':
        return EventTypes.RoomTopic;
      case 'm.room.aliases':
        return EventTypes.RoomAliases;
      case 'm.room.canonical_alias':
        return EventTypes.RoomCanonicalAlias;
      case 'm.room.create':
        return EventTypes.RoomCreate;
      case 'm.room.redaction':
        return EventTypes.Redaction;
      case 'm.room.join_rules':
        return EventTypes.RoomJoinRules;
      case 'm.room.member':
        return EventTypes.RoomMember;
      case 'm.room.power_levels':
        return EventTypes.RoomPowerLevels;
      case 'm.room.guest_access':
        return EventTypes.GuestAccess;
      case 'm.room.history_visibility':
        return EventTypes.HistoryVisibility;
      case 'm.sticker':
        return EventTypes.Sticker;
      case 'm.room.message':
        return EventTypes.Message;
      case 'm.room.encrypted':
        return EventTypes.Encrypted;
      case 'm.room.encryption':
        return EventTypes.Encryption;
      case 'm.call.invite':
        return EventTypes.CallInvite;
      case 'm.call.answer':
        return EventTypes.CallAnswer;
      case 'm.call.candidates':
        return EventTypes.CallCandidates;
      case 'm.call.hangup':
        return EventTypes.CallHangup;
    }
    return EventTypes.Unknown;
  }

  ///
  MessageTypes get messageType {
    switch (content['msgtype'] ?? 'm.text') {
      case 'm.text':
        if (content.containsKey('m.relates_to')) {
          return MessageTypes.Reply;
        }
        return MessageTypes.Text;
      case 'm.notice':
        return MessageTypes.Notice;
      case 'm.emote':
        return MessageTypes.Emote;
      case 'm.image':
        return MessageTypes.Image;
      case 'm.video':
        return MessageTypes.Video;
      case 'm.audio':
        return MessageTypes.Audio;
      case 'm.file':
        return MessageTypes.File;
      case 'm.sticker':
        return MessageTypes.Sticker;
      case 'm.location':
        return MessageTypes.Location;
      case 'm.bad.encrypted':
        return MessageTypes.BadEncrypted;
      default:
        if (type == EventTypes.Message) {
          return MessageTypes.Text;
        }
        return MessageTypes.None;
    }
  }

  void setRedactionEvent(Event redactedBecause) {
    unsigned = {
      'redacted_because': redactedBecause.toJson(),
    };
    prevContent = null;
    var contentKeyWhiteList = <String>[];
    switch (type) {
      case EventTypes.RoomMember:
        contentKeyWhiteList.add('membership');
        break;
      case EventTypes.RoomCreate:
        contentKeyWhiteList.add('creator');
        break;
      case EventTypes.RoomJoinRules:
        contentKeyWhiteList.add('join_rule');
        break;
      case EventTypes.RoomPowerLevels:
        contentKeyWhiteList.add('ban');
        contentKeyWhiteList.add('events');
        contentKeyWhiteList.add('events_default');
        contentKeyWhiteList.add('kick');
        contentKeyWhiteList.add('redact');
        contentKeyWhiteList.add('state_default');
        contentKeyWhiteList.add('users');
        contentKeyWhiteList.add('users_default');
        break;
      case EventTypes.RoomAliases:
        contentKeyWhiteList.add('aliases');
        break;
      case EventTypes.HistoryVisibility:
        contentKeyWhiteList.add('history_visibility');
        break;
      default:
        break;
    }
    var toRemoveList = <String>[];
    for (var entry in content.entries) {
      if (!contentKeyWhiteList.contains(entry.key)) {
        toRemoveList.add(entry.key);
      }
    }
    toRemoveList.forEach((s) => content.remove(s));
  }

  /// Returns the body of this event if it has a body.
  String get text => content['body'] ?? '';

  /// Returns the formatted boy of this event if it has a formatted body.
  String get formattedText => content['formatted_body'] ?? '';

  @Deprecated('Use [body] instead.')
  String getBody() => body;

  /// Use this to get the body.
  String get body {
    if (redacted) return 'Redacted';
    if (text != '') return text;
    if (formattedText != '') return formattedText;
    return '$type';
  }

  /// Returns a list of [Receipt] instances for this event.
  List<Receipt> get receipts {
    if (!(room.roomAccountData.containsKey('m.receipt'))) return [];
    var receiptsList = <Receipt>[];
    for (var entry in room.roomAccountData['m.receipt'].content.entries) {
      if (entry.value['event_id'] == eventId) {
        receiptsList.add(Receipt(room.getUserByMXIDSync(entry.key),
            DateTime.fromMillisecondsSinceEpoch(entry.value['ts'])));
      }
    }
    return receiptsList;
  }

  /// Removes this event if the status is < 1. This event will just be removed
  /// from the database and the timelines. Returns false if not removed.
  Future<bool> remove() async {
    if (status < 1) {
      if (room.client.store != null) {
        await room.client.store.removeEvent(eventId);
      }

      room.client.onEvent.add(EventUpdate(
          roomID: room.id,
          type: 'timeline',
          eventType: typeKey,
          content: {
            'event_id': eventId,
            'status': -2,
            'content': {'body': 'Removed...'}
          }));
      return true;
    }
    return false;
  }

  /// Try to send this event again. Only works with events of status -1.
  Future<String> sendAgain({String txid}) async {
    if (status != -1) return null;
    await remove();
    final eventID = await room.sendTextEvent(text, txid: txid);
    return eventID;
  }

  /// Whether the client is allowed to redact this event.
  bool get canRedact => senderId == room.client.userID || room.canRedact;

  /// Redacts this event. Returns [ErrorResponse] on error.
  Future<dynamic> redact({String reason, String txid}) =>
      room.redactEvent(eventId, reason: reason, txid: txid);

  /// Whether this event is in reply to another event.
  bool get isReply =>
      content['m.relates_to'] is Map<String, dynamic> &&
      content['m.relates_to']['m.in_reply_to'] is Map<String, dynamic> &&
      content['m.relates_to']['m.in_reply_to']['event_id'] is String &&
      (content['m.relates_to']['m.in_reply_to']['event_id'] as String)
          .isNotEmpty;

  /// Searches for the reply event in the given timeline.
  Future<Event> getReplyEvent(Timeline timeline) async {
    if (!isReply) return null;
    final String replyEventId =
        content['m.relates_to']['m.in_reply_to']['event_id'];
    return await timeline.getEventById(replyEventId);
  }

  /// Trys to decrypt this event. Returns a m.bad.encrypted event
  /// if it fails and does nothing if the event was not encrypted.
  Event get decrypted => room.decryptGroupMessage(this);

  /// If this event is encrypted and the decryption was not successful because
  /// the session is unknown, this requests the session key from other devices
  /// in the room. If the event is not encrypted or the decryption failed because
  /// of a different error, this throws an exception.
  Future<void> requestKey() async {
    if (type != EventTypes.Encrypted ||
        messageType != MessageTypes.BadEncrypted ||
        content['body'] != DecryptError.UNKNOWN_SESSION) {
      throw ('Session key not unknown');
    }
    final users = await room.requestParticipants();
    await room.client.sendToDevice(
        [],
        'm.room_key_request',
        {
          'action': 'request_cancellation',
          'request_id': base64.encode(utf8.encode(content['session_id'])),
          'requesting_device_id': room.client.deviceID,
        },
        toUsers: users);
    await room.client.sendToDevice(
        [],
        'm.room_key_request',
        {
          'action': 'request',
          'body': {
            'algorithm': 'm.megolm.v1.aes-sha2',
            'room_id': roomId,
            'sender_key': content['sender_key'],
            'session_id': content['session_id'],
          },
          'request_id': base64.encode(utf8.encode(content['session_id'])),
          'requesting_device_id': room.client.deviceID,
        },
        encrypted: false,
        toUsers: users);
    return;
  }

  /// Downloads (and decryptes if necessary) the attachment of this
  /// event and returns it as a [MatrixFile]. If this event doesn't
  /// contain an attachment, this throws an error.
  Future<MatrixFile> downloadAndDecryptAttachment() async {
    if (![EventTypes.Message, EventTypes.Sticker].contains(type)) {
      throw ("This event has the type '$typeKey' and so it can't contain an attachment.");
    }
    if (!content.containsKey('url') && !content.containsKey('file')) {
      throw ("This event hasn't any attachment.");
    }
    final isEncrypted = !content.containsKey('url');

    if (isEncrypted && !room.client.encryptionEnabled) {
      throw ('Encryption is not enabled in your Client.');
    }
    var mxContent =
        MxContent(isEncrypted ? content['file']['url'] : content['url']);

    Uint8List uint8list;

    // Is this file storeable?
    final storeable = room.client.storeAPI.extended &&
        content['info'] is Map<String, dynamic> &&
        content['info']['size'] is int &&
        content['info']['size'] <= ExtendedStoreAPI.MAX_FILE_SIZE;

    if (storeable) {
      uint8list = await room.client.store.getFile(mxContent.mxc);
    }

    // Download the file
    if (uint8list == null) {
      uint8list =
          (await http.get(mxContent.getDownloadLink(room.client))).bodyBytes;
      await room.client.store.storeFile(uint8list, mxContent.mxc);
    }

    // Decrypt the file
    if (isEncrypted) {
      if (!content.containsKey('file') ||
          !content['file']['key']['key_ops'].contains('decrypt')) {
        throw ("Missing 'decrypt' in 'key_ops'.");
      }
      final encryptedFile = EncryptedFile();
      encryptedFile.data = uint8list;
      encryptedFile.iv = content['file']['iv'];
      encryptedFile.k = content['file']['key']['k'];
      encryptedFile.sha256 = content['file']['hashes']['sha256'];
      uint8list = await decryptFile(encryptedFile);
    }
    return MatrixFile(bytes: uint8list, path: '/$body');
  }
}

enum MessageTypes {
  Text,
  Emote,
  Notice,
  Image,
  Video,
  Audio,
  File,
  Location,
  Reply,
  Sticker,
  BadEncrypted,
  None,
}

enum EventTypes {
  Message,
  Sticker,
  Redaction,
  RoomAliases,
  RoomCanonicalAlias,
  RoomCreate,
  RoomJoinRules,
  RoomMember,
  RoomPowerLevels,
  RoomName,
  RoomTopic,
  RoomAvatar,
  GuestAccess,
  HistoryVisibility,
  Encryption,
  Encrypted,
  CallInvite,
  CallAnswer,
  CallCandidates,
  CallHangup,
  Unknown,
}