MobilApp/lib/gnss_sentences/gnrmc.dart

import 'package:nmea/nmea.dart';

class Gnrmc extends TalkerSentence {
  static const String id = 'GxRMC';

  Gnrmc({required super.raw});

  @override
  bool get valid => super.valid && fields.length >= 10;

  String get messageId => _field(0);

  String get utcOfPositionFix => _field(1);

  String get status => _field(2).toUpperCase();

  String get latitudeDirection => _field(4).toUpperCase();

  double get latitude => _parseLatitude(_field(3), latitudeDirection) ?? 0.0;

  String get longitudeDirection => _field(6).toUpperCase();

  double get longitude => _parseLongitude(_field(5), longitudeDirection) ?? 0.0;

  double get speedOverGroundKnots => _parseDouble(_field(7), fallback: 0.0);

  double get courseOverGround => _parseDouble(_field(8), fallback: 0.0);

  String get date => _field(9);

  // Opcionális mezők -> nullable getterek
  double? get magneticVariation => _parseDoubleOrNull(_field(10));

  String get magneticVariationDirection => _field(11).toUpperCase();

  String get positioningSystemModeIndicator => _field(12).toUpperCase();

  String _field(int index) {
    if (index < 0 || index >= fields.length) return '';
    return fields[index].trim();
  }

  double _parseDouble(String value, {required double fallback}) {
    return double.tryParse(value) ?? fallback;
  }

  double? _parseDoubleOrNull(String value) {
    if (value.isEmpty) return null;
    return double.tryParse(value);
  }

  double? _parseLatitude(String value, String direction) {
    if (value.length < 4) return null; // ddmm.mmmm
    final deg = double.tryParse(value.substring(0, 2));
    final min = double.tryParse(value.substring(2));
    if (deg == null || min == null) return null;

    final result = deg + (min / 60.0);
    return direction == 'S' ? -result : result;
  }

  double? _parseLongitude(String value, String direction) {
    if (value.length < 5) return null; // dddmm.mmmm
    final deg = double.tryParse(value.substring(0, 3));
    final min = double.tryParse(value.substring(3));
    if (deg == null || min == null) return null;

    final result = deg + (min / 60.0);
    return direction == 'W' ? -result : result;
  }
}