twonly-app/lib/src/providers/api/server_messages.dart

import 'dart:convert';
import 'dart:typed_data';
import 'package:cryptography_plus/cryptography_plus.dart';
import 'package:drift/drift.dart';
import 'package:fixnum/fixnum.dart';
import 'package:libsignal_protocol_dart/libsignal_protocol_dart.dart';
import 'package:logging/logging.dart';
import 'package:twonly/globals.dart';
import 'package:twonly/src/app.dart';
import 'package:twonly/src/database/database.dart';
import 'package:twonly/src/database/messages_db.dart';
import 'package:twonly/src/model/json/message.dart';
import 'package:twonly/src/proto/api/client_to_server.pb.dart' as client;
import 'package:twonly/src/proto/api/client_to_server.pbserver.dart';
import 'package:twonly/src/proto/api/error.pb.dart';
import 'package:twonly/src/proto/api/server_to_client.pb.dart' as server;
import 'package:twonly/src/proto/api/server_to_client.pbserver.dart';
import 'package:twonly/src/providers/api/api.dart';
import 'package:twonly/src/providers/api/api_utils.dart';
import 'package:twonly/src/providers/api/media.dart';
import 'package:twonly/src/providers/hive.dart';
import 'package:twonly/src/services/notification_service.dart';
// ignore: library_prefixes
import 'package:twonly/src/utils/signal.dart' as SignalHelper;

Future handleServerMessage(server.ServerToClient msg) async {
  client.Response? response;

  try {
    if (msg.v0.hasRequestNewPreKeys()) {
      response = await handleRequestNewPreKey();
    } else if (msg.v0.hasNewMessage()) {
      Uint8List body = Uint8List.fromList(msg.v0.newMessage.body);
      int fromUserId = msg.v0.newMessage.fromUserId.toInt();
      response = await handleNewMessage(fromUserId, body);
    } else if (msg.v0.hasDownloaddata()) {
      response = await handleDownloadData(msg.v0.downloaddata);
    } else {
      Logger("handleServerMessage")
          .shout("Got a new message from the server: $msg");
      return;
    }
  } catch (e) {
    response = client.Response()..error = ErrorCode.InternalError;
  }

  var v0 = client.V0()
    ..seq = msg.v0.seq
    ..response = response;

  apiProvider.sendResponse(ClientToServer()..v0 = v0);
}

Future<client.Response> handleDownloadData(DownloadData data) async {
  if (globalIsAppInBackground) {
    // download should only be done when the app is open
    return client.Response()..error = ErrorCode.InternalError;
  }

  Logger("server_messages")
      .info("downloading: ${data.downloadToken} ${data.fin}");

  final box = await getMediaStorage();

  String boxId = data.downloadToken.toString();

  int? messageId = box.get("${data.downloadToken}_messageId");

  if (messageId == null) {
    Logger("server_messages")
        .info("download data received, but unknown messageID");
    // answers with ok, so the server will delete the message
    var ok = client.Response_Ok()..none = true;
    return client.Response()..ok = ok;
  }

  if (data.fin && data.data.isEmpty) {
    // media file was deleted by the server. remove the media from device
    await twonlyDatabase.deleteMessageById(messageId);
    box.delete(boxId);
    box.delete("${data.downloadToken}_downloaded");
    var ok = client.Response_Ok()..none = true;
    return client.Response()..ok = ok;
  }

  Uint8List? buffered = box.get(boxId);
  Uint8List downloadedBytes;
  if (buffered != null) {
    if (data.offset != buffered.length) {
      Logger("server_messages")
          .info("server send wrong offset: ${data.offset} ${buffered.length}");
      // Logger("handleDownloadData").error(object)
      return client.Response()..error = ErrorCode.InvalidOffset;
    }
    var b = BytesBuilder();
    b.add(buffered);
    b.add(data.data);

    downloadedBytes = b.takeBytes();
  } else {
    downloadedBytes = Uint8List.fromList(data.data);
  }

  if (!data.fin) {
    // download not finished, so waiting for more data...
    box.put(boxId, downloadedBytes);
    var ok = client.Response_Ok()..none = true;
    return client.Response()..ok = ok;
  }

  // Uint8List? rawBytes =
  //     await SignalHelper.decryptBytes(downloadedBytes, fromUserId);

  Message? msg =
      await twonlyDatabase.getMessageByMessageId(messageId).getSingleOrNull();
  if (msg == null) {
    Logger("server_messages")
        .info("messageId not found in database. Ignoring download");
    // answers with ok, so the server will delete the message
    var ok = client.Response_Ok()..none = true;
    return client.Response()..ok = ok;
  }

  MediaMessageContent content =
      MediaMessageContent.fromJson(jsonDecode(msg.contentJson!));

  final xchacha20 = Xchacha20.poly1305Aead();
  SecretKeyData secretKeyData = SecretKeyData(content.encryptionKey!);

  SecretBox secretBox = SecretBox(
    downloadedBytes,
    nonce: content.encryptionNonce!,
    mac: Mac(content.encryptionMac!),
  );

  try {
    final rawBytes =
        await xchacha20.decrypt(secretBox, secretKey: secretKeyData);

    box.put("${data.downloadToken}_downloaded", rawBytes);
  } catch (e) {
    Logger("server_messages").info("Decryption error: $e");
    // deleting message as this is an invalid image
    await twonlyDatabase.deleteMessageById(messageId);
    // answers with ok, so the server will delete the message
    var ok = client.Response_Ok()..none = true;
    return client.Response()..ok = ok;
  }

  await twonlyDatabase.updateMessageByOtherUser(
    msg.contactId,
    messageId,
    MessagesCompanion(downloadState: Value(DownloadState.downloaded)),
  );

  box.delete(boxId);

  var ok = client.Response_Ok()..none = true;
  return client.Response()..ok = ok;
}

Future<client.Response> handleNewMessage(int fromUserId, Uint8List body) async {
  MessageJson? message = await SignalHelper.getDecryptedText(fromUserId, body);
  if (message != null) {
    switch (message.kind) {
      case MessageKind.contactRequest:
        Result username = await apiProvider.getUsername(fromUserId);
        if (username.isSuccess) {
          Uint8List name = username.value.userdata.username;

          int added = await twonlyDatabase.insertContact(ContactsCompanion(
            username: Value(utf8.decode(name)),
            userId: Value(fromUserId),
            requested: Value(true),
          ));
          if (added > 0) {
            localPushNotificationNewMessage(
              fromUserId.toInt(),
              message,
              999999,
            );
          }
        }
        break;
      case MessageKind.opened:
        final update = MessagesCompanion(openedAt: Value(message.timestamp));
        await twonlyDatabase.updateMessageByOtherUser(
          fromUserId,
          message.messageId!,
          update,
        );
        break;
      case MessageKind.rejectRequest:
        await twonlyDatabase.deleteContactByUserId(fromUserId);
        break;
      case MessageKind.acceptRequest:
        final update = ContactsCompanion(accepted: Value(true));
        twonlyDatabase.updateContact(fromUserId, update);
        localPushNotificationNewMessage(fromUserId.toInt(), message, 8888888);
        break;
      case MessageKind.ack:
        final update = MessagesCompanion(acknowledgeByUser: Value(true));
        await twonlyDatabase.updateMessageByOtherUser(
          fromUserId,
          message.messageId!,
          update,
        );
        break;
      default:
        if (message.kind != MessageKind.textMessage &&
            message.kind != MessageKind.media) {
          Logger("handleServerMessages")
              .shout("Got unknown MessageKind $message");
        } else {
          String content = jsonEncode(message.content!.toJson());

          final update = MessagesCompanion(
            contactId: Value(fromUserId),
            kind: Value(message.kind),
            messageOtherId: Value(message.messageId),
            contentJson: Value(content),
            acknowledgeByServer: Value(true),
            downloadState: Value(message.kind == MessageKind.media
                ? DownloadState.pending
                : DownloadState.downloaded),
            sendAt: Value(message.timestamp),
          );

          final messageId = await twonlyDatabase.insertMessage(
            update,
          );

          if (messageId == null) {
            return client.Response()..error = ErrorCode.InternalError;
          }

          encryptAndSendMessage(
            message.messageId!,
            fromUserId,
            MessageJson(
              kind: MessageKind.ack,
              messageId: message.messageId!,
              content: MessageContent(),
              timestamp: DateTime.now(),
            ),
          );

          if (message.kind == MessageKind.media) {
            twonlyDatabase.incFlameCounter(
              fromUserId,
              true,
              message.timestamp,
            );

            if (!globalIsAppInBackground) {
              final content = message.content;
              if (content is MediaMessageContent) {
                tryDownloadMedia(
                  messageId,
                  fromUserId,
                  content,
                );
              }
            }
          }
          localPushNotificationNewMessage(fromUserId, message, messageId);
        }
    }
  }
  var ok = client.Response_Ok()..none = true;
  return client.Response()..ok = ok;
}

Future<client.Response> handleRequestNewPreKey() async {
  List<PreKeyRecord> localPreKeys = await SignalHelper.getPreKeys();

  List<client.Response_PreKey> prekeysList = [];
  for (int i = 0; i < localPreKeys.length; i++) {
    prekeysList.add(client.Response_PreKey()
      ..id = Int64(localPreKeys[i].id)
      ..prekey = localPreKeys[i].getKeyPair().publicKey.serialize());
  }
  var prekeys = client.Response_Prekeys(prekeys: prekeysList);
  var ok = client.Response_Ok()..prekeys = prekeys;
  return client.Response()..ok = ok;
}