import 'dart:async';

import 'package:flutter/foundation.dart';

import '../../data/models/gps_speed.dart';
import '../../data/services/telemetry_bridge.dart';

/// Polls the native GPS speed snapshot. Starting never asks for permission; it
/// simply returns false when precise location is not already allowed or GPS is
/// disabled.
class GpsSpeedController extends ChangeNotifier {
  GpsSpeedController(this._platform, {DateTime Function()? clock})
    : _clock = clock ?? DateTime.now;

  final TelemetryPlatform _platform;
  final DateTime Function() _clock;

  GpsSpeed _state = const GpsSpeed();
  Timer? _timer;
  bool _active = false;
  bool _polling = false;
  bool _disposed = false;

  bool get hasPermission => _state.hasPermission;

  bool get hasSpeed => _state.isFresh(_clock());

  double? get speedKmh => hasSpeed ? _state.speedKmh : null;

  Future<void> start() async {
    if (_active) return;
    _active = true;
    final started = await _platform.startGpsSpeed();
    if (!started) {
      _notify();
      return;
    }
    _timer = Timer.periodic(const Duration(seconds: 1), (_) => _poll());
    await _poll();
  }

  void stop() {
    _active = false;
    _timer?.cancel();
    _timer = null;
    _state = const GpsSpeed();
    unawaited(_platform.stopGpsSpeed());
    _notify();
  }

  Future<void> _poll() async {
    if (!_active || _polling) return;
    _polling = true;
    try {
      final next = await _platform.getGpsSpeed();
      if (next != _state) {
        _state = next;
        _notify();
      }
    } finally {
      _polling = false;
    }
  }

  void _notify() {
    if (!_disposed) notifyListeners();
  }

  @override
  void dispose() {
    _disposed = true;
    _timer?.cancel();
    unawaited(_platform.stopGpsSpeed());
    super.dispose();
  }
}