import 'dart:convert';

import 'package:http/http.dart' as http;
import 'package:latlong2/latlong.dart';

class OsrmRoutingService {
  const OsrmRoutingService({
    this.baseUrl = 'https://router.project-osrm.org',
    this.profile = 'driving',
  });

  final String baseUrl;
  final String profile;

  Future<List<LatLng>> fetchRoute(List<LatLng> waypoints) async {
    if (waypoints.length < 2) {
      return <LatLng>[];
    }

    final coordinates = waypoints
        .map((point) => '${point.longitude},${point.latitude}')
        .join(';');
    final uri = Uri.parse(
      '$baseUrl/route/v1/$profile/$coordinates'
      '?overview=full&geometries=geojson',
    );

    final response = await http.get(uri);
    if (response.statusCode != 200) {
      throw Exception('Routing request failed (${response.statusCode})');
    }

    final payload = jsonDecode(response.body) as Map<String, dynamic>;
    final routes = payload['routes'];
    if (routes is! List || routes.isEmpty) {
      throw Exception('No route returned');
    }

    final geometry = routes.first['geometry'] as Map<String, dynamic>?;
    final coordinatesList = geometry?['coordinates'];
    if (coordinatesList is! List || coordinatesList.isEmpty) {
      throw Exception('Route geometry missing');
    }

    return coordinatesList.map((pair) {
      if (pair is! List || pair.length < 2) {
        throw Exception('Invalid coordinate pair in route geometry');
      }
      final lon = (pair[0] as num).toDouble();
      final lat = (pair[1] as num).toDouble();
      return LatLng(lat, lon);
    }).toList();
  }
}