import 'package:flutter/foundation.dart';
import 'package:latlong2/latlong.dart';

import 'hud_geometry.dart';
import 'state/aircraft_state.dart';

/// The path the aircraft has flown this session, for the minimap. Follows an
/// [AircraftState] and keeps a point every [minSpacing] metres, so a 10 Hz
/// hover does not grow the list.
class FlightTrail extends ChangeNotifier {
  FlightTrail(this.aircraft, {this.minSpacing = 2, this.maxPoints = 5000}) {
    aircraft.addListener(_onAircraft);
    _onAircraft();
  }

  final AircraftState aircraft;
  final double minSpacing; // m
  final int maxPoints;

  final List<LatLng> _points = <LatLng>[];

  List<LatLng> get points => List<LatLng>.unmodifiable(_points);

  void _onAircraft() {
    final double? lat = aircraft.latitude, lon = aircraft.longitude;
    if (lat == null || lon == null || (lat == 0 && lon == 0)) return;
    if (_points.isNotEmpty) {
      final LatLng last = _points.last;
      if (HudGeometry.distance(last.latitude, last.longitude, lat, lon) < minSpacing) return;
    }
    _points.add(LatLng(lat, lon));
    if (_points.length > maxPoints) _points.removeRange(0, _points.length - maxPoints);
    notifyListeners();
  }

  void clear() {
    if (_points.isEmpty) return;
    _points.clear();
    notifyListeners();
  }

  @override
  void dispose() {
    aircraft.removeListener(_onAircraft);
    super.dispose();
  }
}