gps-speedo/lib/ui/features/speedometer/speedometer_view_model.dart

import 'package:flutter/widgets.dart';
import 'package:provider/provider.dart';
import '../../../core/constants/speed_unit.dart';
import '../../../data/models/location_data.dart';
import '../../../data/repositories/location_repository.dart';
import '../../../providers/settings_provider.dart';

/// ViewModel for the speedometer UI.
///
/// Thin state manager — subscribes to [LocationRepository] and exposes
/// the current display state to the view. No data-layer logic here.
class SpeedometerViewModel extends ChangeNotifier {
  final LocationRepository _repository;
  SettingsProvider? _settings;

  SpeedUnit get displayUnit => _settings?.currentUnit ?? SpeedUnit.kmh;
  LocationData get displayData => _repository.currentData;
  String get displaySpeedText => _repository.currentData.displaySpeed;
  String get displayHeading => _repository.currentData.displayHeading;
  bool get isSpeedValid => _repository.currentData.isSpeedValid;
  bool get isHeadingValid => _repository.currentData.isHeadingValid;

  SpeedometerViewModel(this._repository);

  /// Call when the ViewModel is inserted into the provider tree so it
  /// can listen to SettingsProvider and repository state.
  void attach(BuildContext context) {
    _settings = context.read<SettingsProvider>();
  }

  double get displaySpeed {
    return displayUnit.convert(_repository.currentData.speed);
  }
}