104 lines
No EOL
3.5 KiB
Dart
104 lines
No EOL
3.5 KiB
Dart
import 'dart:convert';
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import 'dart:io';
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import 'package:http/http.dart' as http;
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import 'package:dart_geohash/dart_geohash.dart';
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import 'package:latlong2/latlong.dart';
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import 'package:turf/turf.dart';
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class GeoMetadataLookup {
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final String apiUrl;
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final Directory cacheDir;
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final Distance distance = const Distance();
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GeoMetadataLookup({
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required this.apiUrl,
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required this.cacheDir,
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}) {
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if (!cacheDir.existsSync()) {
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cacheDir.createSync(recursive: true);
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}
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}
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Future<List<Map<String, dynamic>>> lookup(double latitude, double longitude, {double distance = 10.0}) async {
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final String geohash = GeoHasher().encode(longitude, latitude);
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final File cacheFile = File('${cacheDir.path}/$geohash.geojson.gz');
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if (!cacheFile.existsSync()) {
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await _downloadGeoJson(geohash, cacheFile);
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}
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final String geoJsonStr = utf8.decode(GZipCodec().decode(cacheFile.readAsBytesSync()));
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final Map<String, dynamic> geoJson = jsonDecode(geoJsonStr);
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return _findMetadata(latitude, longitude, distance, geoJson);
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}
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Future<void> _downloadGeoJson(String geohash, File cacheFile) async {
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final response = await http.get(Uri.parse('$apiUrl$geohash'));
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if (response.statusCode == 200) {
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cacheFile.writeAsBytesSync(GZipCodec().encode(response.bodyBytes));
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} else {
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throw Exception('Failed to download GeoJSON for geohash: $geohash');
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}
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}
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List<Map<String, dynamic>> _findMetadata(double latitude, double longitude, double distanceThreshold, Map<String, dynamic> geoJson) {
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final Position point = Position(longitude, latitude);
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List<Map<String, dynamic>> results = [];
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for (var feature in geoJson['features']) {
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final geometry = feature['geometry'];
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final properties = feature['properties'] ?? {};
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if (geometry['type'] == 'Polygon') {
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final polygon = Polygon(
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coordinates: (geometry['coordinates'] as List)
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.map((ring) => (ring as List)
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.map((p) => Position(p[0] as double, p[1] as double))
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.toList())
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.toList(),
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);
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if (booleanPointInPolygon(point, polygon)) {
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results.add({'type': 'polygon', ...properties});
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}
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}
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else if (geometry['type'] == 'LineString') {
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final line = LineString(
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coordinates: (geometry['coordinates'] as List)
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.map((p) => Position(p[0] as double, p[1] as double))
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.toList(),
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);
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if (_isPointNearLine(point, line, distanceThreshold)) {
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results.add({'type': 'line', ...properties});
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}
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}
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else if (geometry['type'] == 'MultiLineString') {
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for (var lineCoords in geometry['coordinates']) {
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final line = LineString(
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coordinates: (lineCoords as List)
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.map((p) => Position(p[0] as double, p[1] as double))
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.toList(),
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);
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if (_isPointNearLine(point, line, distanceThreshold)) {
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results.add({'type': 'multi_line', ...properties});
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break;
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}
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}
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}
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}
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return results;
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}
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bool _isPointNearLine(Position point, LineString line, double distanceThreshold) {
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for (var i = 0; i < line.coordinates.length - 1; i++) {
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final p1 = line.coordinates[i];
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final double dist = distance.distance(
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LatLng(point.lat.toDouble(), point.lng.toDouble()),
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LatLng(p1.lat.toDouble(), p1.lng.toDouble()),
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);
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if (dist <= distanceThreshold) return true;
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}
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return false;
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}
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} |