105 lines
3.7 KiB
Dart
105 lines
3.7 KiB
Dart
import 'dart:async';
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import 'package:aves/geo/topojson.dart';
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import 'package:collection/collection.dart';
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import 'package:country_code/country_code.dart';
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import 'package:flutter/foundation.dart';
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import 'package:flutter/services.dart';
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import 'package:latlong2/latlong.dart';
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final CountryTopology countryTopology = CountryTopology._private();
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class CountryTopology {
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static const topoJsonAsset = 'assets/countries-50m.json';
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CountryTopology._private();
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Topology? _topology;
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Future<Topology?> getTopology() => _topology != null ? SynchronousFuture(_topology) : rootBundle.loadString(topoJsonAsset).then(TopoJson().parse);
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// returns the country containing given coordinates
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Future<CountryCode?> countryCode(LatLng position) async {
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return _countryOfNumeric(await numericCode(position));
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}
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// returns the ISO 3166-1 numeric code of the country containing given coordinates
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Future<int?> numericCode(LatLng position) async {
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final topology = await getTopology();
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if (topology == null) return null;
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final countries = (topology.objects['countries'] as GeometryCollection).geometries;
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return _getNumeric(topology, countries, position);
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}
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// returns a map of the given positions by country
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Future<Map<CountryCode, Set<LatLng>>> countryCodeMap(Set<LatLng> positions) async {
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final numericMap = await numericCodeMap(positions);
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if (numericMap == null) return {};
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return Map.fromEntries(numericMap.entries.map((kv) {
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final code = _countryOfNumeric(kv.key);
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return code != null ? MapEntry(code, kv.value) : null;
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}).whereNotNull());
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}
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// returns a map of the given positions by the ISO 3166-1 numeric code of the country containing them
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Future<Map<int, Set<LatLng>>?> numericCodeMap(Set<LatLng> positions) async {
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final topology = await getTopology();
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if (topology == null) return null;
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return compute<_IsoNumericCodeMapData, Map<int, Set<LatLng>>>(_isoNumericCodeMap, _IsoNumericCodeMapData(topology, positions));
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}
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static Future<Map<int, Set<LatLng>>> _isoNumericCodeMap(_IsoNumericCodeMapData data) async {
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try {
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final topology = data.topology;
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final countries = (topology.objects['countries'] as GeometryCollection).geometries;
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final byCode = <int, Set<LatLng>>{};
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for (final position in data.positions) {
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final code = _getNumeric(topology, countries, position);
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if (code != null) {
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byCode[code] = (byCode[code] ?? {})..add(position);
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}
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}
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return byCode;
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} catch (error, stack) {
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// an unhandled error in a spawn isolate would make the app crash
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debugPrint('failed to get country codes with error=$error\n$stack');
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}
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return {};
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}
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static int? _getNumeric(Topology topology, List<Geometry> mruCountries, LatLng position) {
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final point = [position.longitude, position.latitude];
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final hit = mruCountries.firstWhereOrNull((country) => country.containsPoint(topology, point));
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if (hit == null) return null;
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// promote hit countries, assuming given positions are likely to come from the same countries
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if (mruCountries.first != hit) {
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mruCountries.remove(hit);
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mruCountries.insert(0, hit);
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}
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final idString = (hit.id as String?);
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final code = idString == null ? null : int.tryParse(idString);
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return code;
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}
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static CountryCode? _countryOfNumeric(int? numeric) {
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if (numeric == null) return null;
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try {
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return CountryCode.ofNumeric(numeric);
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} catch (error) {
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debugPrint('failed to find country for numeric=$numeric with error=$error');
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}
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return null;
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}
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}
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class _IsoNumericCodeMapData {
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Topology topology;
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Set<LatLng> positions;
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_IsoNumericCodeMapData(this.topology, this.positions);
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}
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