MobilApp/lib/services/gnss/bt_serial_gnss_connection.dart

// lib/services/gnss/bt_serial_gnss_connection.dart
import 'dart:async';
import 'dart:typed_data';
import 'package:flutter_bluetooth_serial/flutter_bluetooth_serial.dart';
import 'gnss_connection.dart';
import 'gnss_device_service.dart';

class BtSerialGnssConnection implements GnssConnection {
  @override
  GnssConnectionType get type => GnssConnectionType.btSerial;

  BluetoothConnection? _connection;
  String _messageBuffer = '';

  final _nmeaController = StreamController<String>.broadcast();
  final _stateController = StreamController<GnssConnectionState>.broadcast();

  @override
  Stream<String> get nmeaLines => _nmeaController.stream;

  @override
  Stream<GnssConnectionState> get connectionState => _stateController.stream;

  @override
  Future<void> connect(String address) async {
    _stateController.add(GnssConnectionState.connecting);
    try {
      _connection = await BluetoothConnection.toAddress(address);
      _stateController.add(GnssConnectionState.connected);
      _connection!.input!.listen(
        _onData,
        onDone: () {
          _stateController.add(GnssConnectionState.disconnected);
        },
      );
    } catch (e) {
      _stateController.add(GnssConnectionState.error);
      rethrow;
    }
  }

  @override
  Future<void> disconnect() async {
    await _connection?.close();
    _connection = null;
    _stateController.add(GnssConnectionState.disconnected);
  }

  // A meglévő _onDataReceived logika változatlanul
  void _onData(Uint8List data) {
    int backspacesCounter = 0;
    for (var byte in data) {
      if (byte == 8 || byte == 127) backspacesCounter++;
    }

    Uint8List buffer = Uint8List(data.length - backspacesCounter);
    int bufferIndex = buffer.length;
    backspacesCounter = 0;

    for (int i = data.length - 1; i >= 0; i--) {
      if (data[i] == 8 || data[i] == 127) {
        backspacesCounter++;
      } else if (backspacesCounter > 0) {
        backspacesCounter--;
      } else {
        buffer[--bufferIndex] = data[i];
      }
    }

    final dataString = String.fromCharCodes(buffer);
    final index = buffer.indexOf(13); // \r

    String sentence;
    if (~index != 0) {
      sentence = _messageBuffer + dataString.substring(0, index);
      _messageBuffer = dataString.substring(index);
    } else {
      _messageBuffer += dataString;
      return;
    }

    // Soronként kibocsátjuk
    for (final line in sentence.split('\n')) {
      final trimmed = line.trim();
      if (trimmed.isNotEmpty) _nmeaController.add(trimmed);
    }
  }

  @override
  void dispose() {
    _connection?.close();
    _nmeaController.close();
    _stateController.close();
  }

  void sendData(Uint8List data) {
    _connection?.output.add(data);
  }
}