rugreefer/lib/rugreefer.dart

import 'dart:convert';
import 'dart:io';
import 'package:http/http.dart' as http;
import 'package:dart_geohash/dart_geohash.dart';
import 'package:latlong2/latlong.dart';
import 'package:turf/turf.dart';
import 'package:path_provider/path_provider.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:flutter/foundation.dart' show kIsWeb;

class GeoMetadataLookup {
  final String apiUrl;
  final bool enableCacheExpiration;
  final Duration cacheExpirationDuration;
  final Distance distance = const Distance();
  final http.Client httpClient;
  Directory? cacheDir;

  GeoMetadataLookup({
    required this.apiUrl,
    this.enableCacheExpiration = false,
    this.cacheExpirationDuration = const Duration(days: 14),
    http.Client? client,
  }) : httpClient = client ?? http.Client() {
    _initCacheDir();
  }

  Future<void> _initCacheDir() async {
    if (!kIsWeb) {
      cacheDir = await getApplicationDocumentsDirectory();
      if (enableCacheExpiration) {
        await _cleanExpiredCache();
      }
    }
  }

  Future<List<Map<String, dynamic>>> lookup(double latitude, double longitude, {double distanceThreshold = 10.0}) async {
    final String geohash = GeoHasher().encode(latitude, longitude, precision: 4);
    
    if (kIsWeb) {
      return _lookupWeb(geohash);
    } else {
      return _lookupFile(geohash, latitude, longitude, distanceThreshold);
    }
  }

  Future<List<Map<String, dynamic>>> _lookupFile(String geohash, double latitude, double longitude, double distanceThreshold) async {
    final File cacheFile = File('${cacheDir?.path}/$geohash.geojson.gz');

    await _updateLastAccessTime(geohash);
    final bool isExpired = await _isCacheExpired(geohash);

    if (!cacheFile.existsSync() || isExpired) {
      await _downloadGeoJson(geohash, cacheFile);
    }

    final String geoJsonStr = utf8.decode(GZipCodec().decode(cacheFile.readAsBytesSync()));
    final Map<String, dynamic> geoJson = jsonDecode(geoJsonStr);
    return _findMetadata(latitude, longitude, geoJson, distanceThreshold);
  }

  Future<List<Map<String, dynamic>>> _lookupWeb(String geohash) async {
    final prefs = await SharedPreferences.getInstance();
    final String? cachedGeoJson = prefs.getString('geojson_$geohash');

    if (cachedGeoJson == null || await _isCacheExpired(geohash)) {
      final response = await http.get(Uri.parse('$apiUrl?geohash=$geohash&format=geojson'));
      if (response.statusCode == 200) {
        await prefs.setString('geojson_$geohash', utf8.decode(response.bodyBytes));
        await _updateLastAccessTime(geohash);
        return _findMetadata(0, 0, jsonDecode(utf8.decode(response.bodyBytes)), 10.0);
      } else {
        throw Exception('Failed to download GeoJSON for geohash: $geohash');
      }
    }
    return _findMetadata(0, 0, jsonDecode(cachedGeoJson), 10.0);
  }

  Future<void> _downloadGeoJson(String geohash, File cacheFile) async {
  final response = await httpClient.get(Uri.parse('$apiUrl?geohash=$geohash&format=geojson'));
  if (response.statusCode == 200) {
    cacheFile.writeAsBytesSync(GZipCodec().encode(response.bodyBytes));
    await _updateLastAccessTime(geohash);
  } else {
    throw Exception('Failed to download GeoJSON for geohash: $geohash');
  }
}

  Future<void> _updateLastAccessTime(String geohash) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setInt('cache_last_access_$geohash', DateTime.now().millisecondsSinceEpoch);
  }

  Future<bool> _isCacheExpired(String geohash) async {
    if (!enableCacheExpiration) return false;
    final prefs = await SharedPreferences.getInstance();
    final int? lastAccess = prefs.getInt('cache_last_access_$geohash');
    if (lastAccess == null) return true;
    return DateTime.now().difference(DateTime.fromMillisecondsSinceEpoch(lastAccess)) > cacheExpirationDuration;
  }

  Future<void> _cleanExpiredCache() async {
    final prefs = await SharedPreferences.getInstance();
    final keys = prefs.getKeys().where((key) => key.startsWith('cache_last_access_')).toList();
    for (var key in keys) {
      final geohash = key.replaceFirst('cache_last_access_', '');
      if (await _isCacheExpired(geohash)) {
        final File cacheFile = File('${cacheDir?.path}/$geohash.geojson.gz');
        if (cacheFile.existsSync()) {
          cacheFile.deleteSync();
        }
        await prefs.remove(key);
      }
    }
  }

  List<Map<String, dynamic>> _findMetadata(double latitude, double longitude, Map<String, dynamic> geoJson, double distanceThreshold) {
    final Position point = Position(longitude, latitude);
    List<Map<String, dynamic>> results = [];

    for (var feature in geoJson['features']) {
      final geometry = feature['geometry'];
      final properties = feature['properties'] ?? {};
      final metadata = properties['tags']?.cast<String, dynamic>() ?? {};

      metadata.removeWhere((key, value) => value == null);

      if (geometry['type'] == 'Polygon') {
        final polygon = Polygon(
          coordinates: (geometry['coordinates'] as List)
              .map((ring) => (ring as List)
                  .map((p) => Position(p[0] as double, p[1] as double))
                  .toList())
              .toList(),
        );
        if (booleanPointInPolygon(point, polygon)) {
          results.add({"type": "polygon", ...metadata});
        }
      }
      
      else if (geometry['type'] == 'LineString') {
        final line = LineString(
          coordinates: (geometry['coordinates'] as List)
              .map((p) => Position(p[0] as double, p[1] as double))
              .toList(),
        );
        if (_isPointNearLine(point, line, distanceThreshold)) {
          results.add({"type": "line", ...metadata});
        }
      }
    }
    return results;
  }

  bool _isPointNearLine(Position point, LineString line, double distanceThreshold) {
    for (var p1 in line.coordinates) {
      final double dist = distance.distance(
        LatLng(point.lat.toDouble(), point.lng.toDouble()),
        LatLng(p1.lat.toDouble(), p1.lng.toDouble()),
      );
      if (dist <= distanceThreshold) return true;
    }
    return false;
  }
}