getSpeedLimit method

Future<SpeedLimitResult?> getSpeedLimit(LatLng location)

Fetches speed limit for given location (lat, lon) with intelligent rate-limiting.

Layer 1: In-flight lock (prevents duplicate simultaneous requests) Layer 2: Time cooldown check (minInterval) Layer 3: Distance threshold check (minDistanceMeters) Layer 4: Segment ID (ogc_fid) caching

Implementation

Future<SpeedLimitResult?> getSpeedLimit(LatLng location) async {
  final now = DateTime.now();

  // Layer 1: In-flight lock
  if (_isFetching) {
    return _cachedResult;
  }

  // Layer 2: Time cooldown check
  if (_lastFetchTime != null && now.difference(_lastFetchTime!) < minInterval) {
    return _cachedResult;
  }

  // Layer 3: Distance threshold check
  if (_lastFetchLocation != null) {
    final distMoved = NavigationMathUtils.haversineDistance(
      _lastFetchLocation!,
      location,
    );
    if (distMoved < minDistanceMeters && _cachedResult != null) {
      return _cachedResult;
    }
  }

  _isFetching = true;
  try {
    final baseUrl = PowerMapSDK.baseUrl;
    final headers = await PowerMapSDK.getServiceHeaders();

    final uri = Uri.parse('$baseUrl/api/v2/map/speed-limit').replace(
      queryParameters: {
        'lat': location.latitude.toString(),
        'lon': location.longitude.toString(),
      },
    );

    final response = await _client.get(uri, headers: headers).timeout(
      const Duration(seconds: 5),
    );

    if (response.statusCode == 200) {
      final Map<String, dynamic> jsonMap = json.decode(response.body);
      final result = SpeedLimitResult.fromJson(jsonMap);

      // Layer 4: Segment ID (ogc_fid) check
      _lastFetchTime = now;
      _lastFetchLocation = location;
      _lastOgcFid = result.ogcFid ?? _lastOgcFid;
      _cachedResult = result;

      return result;
    } else {
      if (kDebugMode) {
        print('SpeedLimitService API response error: ${response.statusCode}');
      }
    }
  } catch (e) {
    if (kDebugMode) {
      print('SpeedLimitService error fetching speed limit: $e');
    }
  } finally {
    _isFetching = false;
  }

  return _cachedResult;
}