// lib/services/gnss/gnss_service.dart
import 'dart:async';
import 'dart:typed_data';

import 'package:geolocator/geolocator.dart';
import 'package:get/get.dart';
import 'package:googleapis/privateca/v1.dart';
import 'package:nmea/nmea.dart';
import 'package:terepi_seged/services/gnss/gnss_device_service.dart';
import 'package:terepi_seged/services/gnss/phone_gps_connection.dart';

import '../../gnss_sentences/gngga.dart';
import '../../gnss_sentences/gngst.dart';
import '../../gnss_sentences/gnrmc.dart';
import 'bt_serial_gnss_connection.dart';
import 'ble_gnss_connection.dart';
import 'gnss_connection.dart';

class GnssService extends GetxService {
  static GnssService get to => Get.find();

  GnssConnection? _connection;

  // ── Kapcsolat állapot ─────────────────────────────────────────────
  final connectionState = GnssConnectionState.disconnected.obs;
  final activeConnectionType = Rxn<GnssConnectionType>();

  // ── GGA adatok ────────────────────────────────────────────────────
  final latitude = 0.0.obs;
  final longitude = 0.0.obs;
  final altitude = 0.0.obs; // MSL (ortometrikus)
  final geoidSeparation = 0.0.obs; // N — geoid undulációja
  final gpsQuality = 0.obs;
  final utcFix = ''.obs;
  final satelliteCount = 0.obs;
  final hdop = 0.0.obs;

  // Utolsó nyers GGA sor — NtripService küldi vissza a casternek
  final lastGgaLine = ''.obs;

  // ── GST adatok (pontossági hibák) ─────────────────────────────────
  final latitudeError = 0.0.obs;
  final longitudeError = 0.0.obs;
  final altitudeError = 0.0.obs;

  // ── RMC adatok (dátum/idő) ────────────────────────────────────────
  final gpsDateTime = DateTime(2000).obs;

  Timer? _reconnectTimer;
  bool _isClosing = false;

  // Segédmező: van-e érvényes adat
  bool get hasValidData => gpsQuality.value > 0;

  // ── Belső ─────────────────────────────────────────────────────────
  final NmeaDecoder _decoder = NmeaDecoder();
  StreamSubscription? _nmeaSub;
  StreamSubscription? _stateSub;
  StreamSubscription<Position>? _positionSub;

  final _updateController = StreamController<void>.broadcast();
  Stream<void> get onDataUpdated => _updateController.stream;

  String _utcTime = '';
  String _utcDate = '';

  bool _intentionalDisconnection = false;

  String _digitsOnly(String value) => value.replaceAll(RegExp(r'[^0-9]'), '');

  @override
  void onInit() {
    super.onInit();
    _decoder
      ..registerTalkerSentence('GGA', (l) => Gngga(raw: l))
      ..registerTalkerSentence('GST', (l) => Gngst(raw: l))
      ..registerTalkerSentence('RMC', (l) => Gnrmc(raw: l));
  }

  // ── Kapcsolódás ───────────────────────────────────────────────────

  Future<void> connectBtSerial(String macAddress) async {
    await _disconnect();
    _connection = BtSerialGnssConnection();
    activeConnectionType.value = GnssConnectionType.btSerial;
    await _doConnect(macAddress);
  }

  Future<void> connectBle(
    String deviceId, {
    String? serviceUuid,
    String? txCharUuid,
  }) async {
    await _disconnect();
    _connection = BleGnssConnection(
      serviceUuid: serviceUuid ?? '6e400001-b5b3-f393-e0a9-e50e24dcca9e',
      txCharUuid: txCharUuid ?? '6e400003-b5b3-f393-e0a9-e50e24dcca9e',
    );
    activeConnectionType.value = GnssConnectionType.ble;
    await _doConnect(deviceId);
  }

  /// Eszközváltás — GnssDevicePicker hívja.
  Future<void> onDeviceChanged(GnssDevice? device) async {
    if (device == null) {
      await _disconnect();
      activeConnectionType.value = GnssConnectionType.none;
      return;
    }

    switch (device.type) {
      case GnssConnectionType.none:
        await _disconnect();
        activeConnectionType.value = GnssConnectionType.none;
        break;
      case GnssConnectionType.btSerial:
        await connectBtSerial(device.address);
        break;
      case GnssConnectionType.ble:
        await connectBle(device.address);
        break;
      case GnssConnectionType.phoneGps:
        await _disconnect();
        _connection = PhoneGpsConnection();
        //connectionState.value = GnssConnectionState.disconnected;
        activeConnectionType.value = GnssConnectionType.phoneGps;
        await _doConnect('iternal');
        break;
    }
  }

  Future<void> reconnect() async {
    final device = GnssDeviceService.to.selectedDevice.value;
    if (device == null) return;
    await _disconnect();
    await onDeviceChanged(device);
  }

  Future<void> _doConnect(String address) async {
    _stateSub = _connection!.connectionState.listen((s) {
      connectionState.value = s;
      if (s == GnssConnectionState.connected) {
        _reconnectTimer?.cancel();
        return;
      }

      if (s == GnssConnectionState.disconnected) {
        _scheduleReconnect();
      }
    });

    _nmeaSub = _connection!.nmeaLines.listen(_parseNmea);
    _positionSub = _connection!.positionStream.listen(_parseDirectPosition);

    _intentionalDisconnection = false;
    await _connection!.connect(address);
  }

  void _parseDirectPosition(Position pos) {
    if (_isClosing) return;

    latitude.value = pos.latitude;
    longitude.value = pos.longitude;
    altitude.value = pos.altitude;

    gpsQuality.value = 1; // 1 = Standard (nem-RTK) minőség
    satelliteCount.value = 0; // A Geolocator nem ad műholdszámot direktben

    // A Geolocator a pontosságot (accuracy) méterben adja vissza
    latitudeError.value = pos.accuracy;
    longitudeError.value = pos.accuracy;
    altitudeError.value = pos.altitudeAccuracy;

    // Az RMC (idő) adatait is beállítjuk a telefon idejéből
    gpsDateTime.value = pos.timestamp;

    _emitUpdate();
  }

  Future<void> _disconnect() async {
    _intentionalDisconnection = true;
    _reconnectTimer?.cancel();

    await _nmeaSub?.cancel();
    await _positionSub?.cancel();
    await _stateSub?.cancel();

    await _connection?.disconnect();
    _connection?.dispose();
    _connection = null;
    connectionState.value = GnssConnectionState.disconnected;
  }

  Future<void> disconnect() => _disconnect();

  /// RTCM adat továbbítása a GNSS vevőnek (NtripService hívja).
  void sendToReceiver(Uint8List data) {
    if (_connection == null) return;
    if (connectionState.value != GnssConnectionState.connected) return;
    _connection?.sendData(data);
  }

  // ── NMEA parsing ──────────────────────────────────────────────────

  void _parseNmea(String line) {
    if (_isClosing || line.length < 6 || !line.startsWith(r'$')) return;

    final sentenceType = line.substring(3, 6);

    if (sentenceType == 'GGA') {
      _parseGga(line);
    } else if (sentenceType == 'GST' && hasValidData) {
      _parseGst(line);
    } else if (sentenceType == 'RMC' && hasValidData) {
      _parseRmc(line);
    }
  }

  void _parseGga(String line) {
    try {
      final s = _decoder.decode(line);
      if (s == null || !s.valid || s is! Gngga) return;
      if (s.gpsQualityIndicator == 0) return;

      latitude.value = s.latitude;
      longitude.value = s.longitude;
      altitude.value = s.altitudeAboveMeanSeaLevel;
      geoidSeparation.value = s.geoidSeparation;
      gpsQuality.value = s.gpsQualityIndicator;
      utcFix.value = s.utcOfPositionFix;
      satelliteCount.value = s.numberOfSvsInUse;
      hdop.value = s.hdop;
      lastGgaLine.value = line;
      _utcTime = s.utcOfPositionFix;

      _emitUpdate();
    } catch (e) {
      print('GGA parsing error: $e');
    }
  }

  void _parseGst(String line) {
    try {
      final s = _decoder.decode(line);
      if (s == null || !s.valid || s is! Gngst) return;
      latitudeError.value = s.latitudeError;
      longitudeError.value = s.longitudeError;
      altitudeError.value = s.heightError;
    } catch (e) {
      print('GST parse error: $e');
    }
  }

  void _parseRmc(String line) {
    try {
      final s = _decoder.decode(line);
      if (s == null || !s.valid || s is! Gnrmc) return;

      _utcDate = s.date;
      final date = _digitsOnly(_utcDate);
      final time = _digitsOnly(s.utcOfPositionFix);

      if (date.length >= 6 && time.length >= 6) {
        gpsDateTime.value = DateTime.utc(
          2000 + int.parse(date.substring(4, 6)),
          int.parse(date.substring(2, 4)),
          int.parse(date.substring(0, 2)),
          int.parse(time.substring(0, 2)),
          int.parse(time.substring(2, 4)),
          int.parse(time.substring(4, 6)),
        );
      }
    } catch (e) {
      print('RMC parse error: $e');
    }
  }

  @override
  void onClose() async {
    _isClosing = true;

    await _disconnect();

    if (!_updateController.isClosed) {
      _updateController.close();
    }

    super.onClose();
  }

  Future<void> determineInitialPosition() async {
    // 1. Ha már van élő adatunk (pl. a külső vevő már küldött koordinátát),
    // akkor nincs szükség extra lekérdezésre.
    if (latitude.value != 0 && longitude.value != 0) return;

    try {
      // 2. Gyors lekérdezés: megkérdezzük a telefont, hol voltunk utoljára.
      // Ez szinte azonnal visszatér, nem pörgeti fel a GPS chipet.
      final lastPosition = await Geolocator.getLastKnownPosition();

      if (lastPosition != null) {
        latitude.value = lastPosition.latitude;
        longitude.value = lastPosition.longitude;
        return;
      }

      // 3. Ha nincs utolsó ismert pozíció (pl. friss telepítés),
      // kérünk egy friss pozíciót, de alacsony pontossággal, hogy gyors legyen.
      final currentPosition = await Geolocator.getCurrentPosition(
        desiredAccuracy: LocationAccuracy.low,
        timeLimit: const Duration(seconds: 3), // Ne akassza meg az appot sokáig
      );

      latitude.value = currentPosition.latitude;
      longitude.value = currentPosition.longitude;
    } catch (e) {
      // Engedélyhiány vagy kikapcsolt helymeghatározás esetén a térkép
      // marad a (0,0)-n vagy egy alapértelmezett (pl. budapesti) koordinátán.
      print('Nem sikerült lekérni a kezdőpozíciót: $e');
    }
  }

  void _emitUpdate() {
    if (_isClosing || _updateController.isClosed) return;
    _updateController.add(null);
  }

  void _scheduleReconnect() {
    if (_intentionalDisconnection || _isClosing) return;
    if (_reconnectTimer?.isActive ?? false) return;

    _reconnectTimer = Timer(const Duration(seconds: 3), () {
      if (_intentionalDisconnection || _isClosing) return;
      unawaited(reconnect());
    });
  }
}