Basic routing. Still some bugs.

lib/services/routing_service.dart

@@ -0,0 +1,164 @@
+import 'dart:convert';
+import 'package:flutter/foundation.dart';
+import 'package:http/http.dart' as http;
+import 'package:latlong2/latlong.dart';
+
+class RouteResult {
+  final List<LatLng> waypoints;
+  final double distanceMeters;
+  final double durationSeconds;
+  
+  const RouteResult({
+    required this.waypoints,
+    required this.distanceMeters,
+    required this.durationSeconds,
+  });
+  
+  @override
+  String toString() {
+    return 'RouteResult(waypoints: ${waypoints.length}, distance: ${(distanceMeters/1000).toStringAsFixed(1)}km, duration: ${(durationSeconds/60).toStringAsFixed(1)}min)';
+  }
+}
+
+class RoutingService {
+  static const String _baseUrl = 'https://router.project-osrm.org';
+  static const String _userAgent = 'DeFlock/1.0 (OSM surveillance mapping app)';
+  static const Duration _timeout = Duration(seconds: 15);
+  
+  /// Calculate route between two points using OSRM
+  Future<RouteResult> calculateRoute({
+    required LatLng start,
+    required LatLng end,
+    String profile = 'driving', // driving, walking, cycling
+  }) async {
+    debugPrint('[RoutingService] Calculating route from $start to $end');
+    
+    // OSRM uses lng,lat order (opposite of LatLng)
+    final startCoord = '${start.longitude},${start.latitude}';
+    final endCoord = '${end.longitude},${end.latitude}';
+    
+    final uri = Uri.parse('$_baseUrl/route/v1/$profile/$startCoord;$endCoord')
+        .replace(queryParameters: {
+      'overview': 'full', // Get full geometry
+      'geometries': 'polyline', // Use polyline encoding (more compact)
+      'steps': 'false', // Don't need turn-by-turn for now
+    });
+    
+    debugPrint('[RoutingService] OSRM request: $uri');
+    
+    try {
+      final response = await http.get(
+        uri,
+        headers: {
+          'User-Agent': _userAgent,
+        },
+      ).timeout(_timeout);
+      
+      if (response.statusCode != 200) {
+        throw RoutingException('HTTP ${response.statusCode}: ${response.reasonPhrase}');
+      }
+      
+      final data = json.decode(response.body) as Map<String, dynamic>;
+      
+      // Check OSRM response status
+      final code = data['code'] as String?;
+      if (code != 'Ok') {
+        final message = data['message'] as String? ?? 'Unknown routing error';
+        throw RoutingException('OSRM error ($code): $message');
+      }
+      
+      final routes = data['routes'] as List<dynamic>?;
+      if (routes == null || routes.isEmpty) {
+        throw RoutingException('No route found between these points');
+      }
+      
+      final route = routes[0] as Map<String, dynamic>;
+      final geometry = route['geometry'] as String?;
+      final distance = (route['distance'] as num?)?.toDouble() ?? 0.0;
+      final duration = (route['duration'] as num?)?.toDouble() ?? 0.0;
+      
+      if (geometry == null) {
+        throw RoutingException('Route geometry missing from response');
+      }
+      
+      // Decode polyline geometry to waypoints
+      final waypoints = _decodePolyline(geometry);
+      
+      if (waypoints.isEmpty) {
+        throw RoutingException('Failed to decode route geometry');
+      }
+      
+      final result = RouteResult(
+        waypoints: waypoints,
+        distanceMeters: distance,
+        durationSeconds: duration,
+      );
+      
+      debugPrint('[RoutingService] Route calculated: $result');
+      return result;
+      
+    } catch (e) {
+      debugPrint('[RoutingService] Route calculation failed: $e');
+      if (e is RoutingException) {
+        rethrow;
+      } else {
+        throw RoutingException('Network error: $e');
+      }
+    }
+  }
+  
+  /// Decode OSRM polyline geometry to LatLng waypoints
+  List<LatLng> _decodePolyline(String encoded) {
+    try {
+      final List<LatLng> points = [];
+      int index = 0;
+      int lat = 0;
+      int lng = 0;
+      
+      while (index < encoded.length) {
+        int b;
+        int shift = 0;
+        int result = 0;
+        
+        // Decode latitude
+        do {
+          b = encoded.codeUnitAt(index++) - 63;
+          result |= (b & 0x1f) << shift;
+          shift += 5;
+        } while (b >= 0x20);
+        
+        final deltaLat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
+        lat += deltaLat;
+        
+        shift = 0;
+        result = 0;
+        
+        // Decode longitude
+        do {
+          b = encoded.codeUnitAt(index++) - 63;
+          result |= (b & 0x1f) << shift;
+          shift += 5;
+        } while (b >= 0x20);
+        
+        final deltaLng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
+        lng += deltaLng;
+        
+        points.add(LatLng(lat / 1E5, lng / 1E5));
+      }
+      
+      return points;
+    } catch (e) {
+      debugPrint('[RoutingService] Manual polyline decoding failed: $e');
+      return [];
+    }
+  }
+}
+
+class RoutingException implements Exception {
+  final String message;
+  
+  const RoutingException(this.message);
+  
+  @override
+  String toString() => 'RoutingException: $message';
+}