findNearestFeature method

GeoJSONFeature? findNearestFeature(double lat, double lon)

Finds the nearest GeoJSON feature to a given point.

This function iterates over a list of features and calculates the distance between the given point and each feature. The feature with the shortest distance to the point is considered the nearest.

lat and lon are the latitude and longitude coordinates of the given point.

Returns the nearest GeoJSON feature to the given point. If the features list is empty, returns null.

Note: This function only calculates distances for point, lineString, and polygon features. Distances for other types of features will need to be handled separately.

Implementation

GeoJSONFeature? findNearestFeature(double lat, double lon) {
  GeoJSONFeature? nearestFeature;
  double? shortestDistance;

  if (features.isEmpty) return null; // Return null if features list is empty

  for (var feature in features) {
    double? distance;
    switch (feature!.geometry.type) {
      case GeoJSONType.point:
        var coords = (feature.geometry as GeoJSONPoint).coordinates;
        distance = calculateHaversineDistance(lat, lon, coords[1], coords[0]);
        break;
      case GeoJSONType.lineString:
        var coords = (feature.geometry as GeoJSONLineString).coordinates;
        distance = coords
            .map((coord) =>
                calculateHaversineDistance(lat, lon, coord[1], coord[0]))
            .reduce(min);
        break;
      case GeoJSONType.polygon:
        var polygon = (feature.geometry as GeoJSONPolygon).coordinates;
        distance = polygon.first
            .map((coord) =>
                calculateHaversineDistance(lat, lon, coord[1], coord[0]))
            .reduce(min);
        break;
      // Handle other cases if needed
      case GeoJSONType.featureCollection:
        break;
      case GeoJSONType.feature:
        break;
      case GeoJSONType.multiPoint:
        break;
      case GeoJSONType.multiLineString:
        break;
      case GeoJSONType.multiPolygon:
        break;
      case GeoJSONType.geometryCollection:
        break;
    }

    // Only compare if distance is not null
    if (distance != null &&
        (shortestDistance == null || distance < shortestDistance)) {
      shortestDistance = distance;
      nearestFeature = feature;
    }
  }

  return nearestFeature;
}