import 'dart:async';

import '../dji_service.dart';
import '../flight_model.dart';

/// Keeps [FlightModel.flyZones] stocked with the GEO zones around (plan P8):
/// fetched around the aircraft's fix, or the phone's before it has one, again
/// after moving 2 km or every 10 minutes; plus the unlocked list once per
/// connection with the aircraft's licences, and the GEO database's state at
/// start. One fetch at a time; failures wait for the next position.
class FlyZoneLoader {
  FlyZoneLoader({required this.model, required this.dji});

  final FlightModel model;
  final DjiService dji;

  bool _busy = false;
  bool _unlockedLoaded = false;

  void start() {
    model.aircraft.addListener(_check);
    model.addListener(_onModel);
    unawaited(refreshDatabase());
    _check();
  }

  void dispose() {
    model.aircraft.removeListener(_check);
    model.removeListener(_onModel);
  }

  void _onModel() {
    if (!model.connected) _unlockedLoaded = false;
    _check();
  }

  /// The aircraft's fix, else the phone's.
  (double, double)? get _position {
    final double? lat = model.aircraft.latitude, lon = model.aircraft.longitude;
    if (lat != null && lon != null && !(lat == 0 && lon == 0)) return (lat, lon);
    final double? pLat = model.phoneLatitude, pLon = model.phoneLongitude;
    if (pLat != null && pLon != null) return (pLat, pLon);
    return null;
  }

  void _check() {
    if (model.connected && !_unlockedLoaded) {
      _unlockedLoaded = true;
      unawaited(refreshUnlocked());
      unawaited(refreshLicences());
    }
    final (double, double)? p = _position;
    if (p == null || _busy || !model.flyZones.needsZonesFor(p.$1, p.$2)) return;
    unawaited(_fetch(p));
  }

  Future<void> _fetch((double, double) p) async {
    _busy = true;
    try {
      final List<Map<String, dynamic>> zones = await dji.getFlyZonesNearby(latitude: p.$1, longitude: p.$2);
      model.flyZones.applyZones(zones, latitude: p.$1, longitude: p.$2);
    } catch (_) {
      // Database not ready or offline: retry when the position moves on.
    } finally {
      _busy = false;
    }
  }

  /// The aircraft's licences (custom unlock zones).
  Future<void> refreshLicences() async {
    try {
      model.flyZones.applyLicences(await dji.getFlyZoneLicences());
    } catch (_) {
      // Not reported by this aircraft.
    }
  }

  /// The GEO database's versions and state (app-level, no aircraft needed).
  Future<void> refreshDatabase() async {
    try {
      model.flyZones.applyDatabase(await dji.getFlyZoneDatabase());
    } catch (_) {
      // SDK not registered yet.
    }
  }

  Future<void> refreshUnlocked() async {
    try {
      model.flyZones.applyUnlocked(await dji.getUnlockedFlyZones());
    } catch (_) {
      // Not reported by this aircraft.
    }
  }
}