import 'package:latlong2/latlong.dart';
import 'package:manager_api_new/api.dart';

class StepShape {
  final String type; // 'LineString' | 'Polygon'
  final List<LatLng> positions;
  const StepShape(this.type, this.positions);
}

/// Géométrie des GuidedStep : les coordonnées sont stockées en `[lat, lng]`
/// (et NON en GeoJSON `[lng, lat]`), en miroir du `map_geometry_picker` de
/// manager-app et de visitapp-web (voir `visitapp-web/src/lib/geo.ts`).
class GuidedPathGeo {
  static List<LatLng> _pairs(dynamic points) {
    if (points is! List) return const [];
    final result = <LatLng>[];
    for (final p in points) {
      if (p is List && p.length >= 2 && p[0] is num && p[1] is num) {
        result.add(LatLng((p[0] as num).toDouble(), (p[1] as num).toDouble()));
      }
    }
    return result;
  }

  static LatLng? _average(List<LatLng> pts) {
    if (pts.isEmpty) return null;
    final lat = pts.map((p) => p.latitude).reduce((a, b) => a + b) / pts.length;
    final lng = pts.map((p) => p.longitude).reduce((a, b) => a + b) / pts.length;
    return LatLng(lat, lng);
  }

  /// Point représentatif : Point → lui-même ; LineString/Polygon → centroïde.
  static LatLng? center(GeometryDTO? geometry) {
    final coords = geometry?.coordinates;
    if (coords is! List || coords.isEmpty) return null;
    if (geometry?.type == 'LineString') return _average(_pairs(coords));
    if (geometry?.type == 'Polygon') return _average(_pairs(coords[0]));
    if (coords[0] is num && coords[1] is num) {
      return LatLng((coords[0] as num).toDouble(), (coords[1] as num).toDouble());
    }
    return null;
  }

  /// Tracé réel d'un LineString/Polygon (pour dessiner sur la carte) ;
  /// null pour un Point.
  static StepShape? shape(GeometryDTO? geometry) {
    final coords = geometry?.coordinates;
    if (coords is! List) return null;
    if (geometry?.type == 'LineString') {
      final pos = _pairs(coords);
      return pos.length > 1 ? StepShape('LineString', pos) : null;
    }
    if (geometry?.type == 'Polygon') {
      final pos = _pairs(coords.isNotEmpty ? coords[0] : null);
      return pos.length > 2 ? StepShape('Polygon', pos) : null;
    }
    return null;
  }

  static bool hasPoint(GeometryDTO? geometry) => center(geometry) != null;
}