import 'package:geolocator/geolocator.dart';

/// Supplies the device's *approximate* location (or null when unavailable or
/// denied). Behind an interface so the UI is fakeable in tests and the concrete
/// platform plugin stays at the composition root. The caller immediately reduces
/// the result to a low-precision geohash — a precise fix never leaves the device.
abstract interface class CoarseLocationProvider {
  Future<({double lat, double lon})?> currentCoarseLatLon();
}

/// [geolocator]-backed implementation. Requests low accuracy only, and returns
/// null on any denial/error rather than throwing, so the UI can degrade quietly.
class GeolocatorCoarseLocation implements CoarseLocationProvider {
  const GeolocatorCoarseLocation();

  @override
  Future<({double lat, double lon})?> currentCoarseLatLon() async {
    try {
      var permission = await Geolocator.checkPermission();
      if (permission == LocationPermission.denied) {
        permission = await Geolocator.requestPermission();
      }
      // Give the user a way out of a permanent denial.
      if (permission == LocationPermission.deniedForever) {
        await Geolocator.openAppSettings();
        return null;
      }
      if (permission == LocationPermission.denied) return null;
      if (!await Geolocator.isLocationServiceEnabled()) {
        await Geolocator.openLocationSettings();
        return null;
      }

      // A fresh coarse fix can take a while (or never come indoors); fall back
      // to the last known position so the button stays responsive.
      Position? position;
      try {
        position = await Geolocator.getCurrentPosition(
          locationSettings: const LocationSettings(
            accuracy: LocationAccuracy.low,
            timeLimit: Duration(seconds: 12),
          ),
        );
      } catch (_) {
        position = await Geolocator.getLastKnownPosition();
      }
      if (position == null) return null;
      return (lat: position.latitude, lon: position.longitude);
    } catch (_) {
      return null; // plugin unsupported (desktop), etc.
    }
  }
}