120 lines
3.8 KiB
Dart
120 lines
3.8 KiB
Dart
import 'dart:async';
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import 'dart:io';
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import 'package:maplibre_gl/maplibre_gl.dart';
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import 'dart:math' as math;
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/// Service for managing offline map regions in Intaleq Maps.
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///
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/// This service allows you to download map tiles for a specific region
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/// so they can be accessed without an internet connection.
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class IntaleqOfflineService {
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static final IntaleqOfflineService instance = IntaleqOfflineService._();
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IntaleqOfflineService._();
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bool _isDownloading = false;
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LatLng? _lastDownloadedCenter;
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Timer? _debounceTimer;
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/// Calculate bounding box for a given center and radius in km.
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LatLngBounds _calculateBounds(LatLng center, double radiusKm) {
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const double earthRadius = 6371.0;
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// Latitude degrees per km
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double latDelta = (radiusKm / earthRadius) * (180 / math.pi);
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// Longitude degrees per km at given latitude
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double lngDelta = (radiusKm / earthRadius) *
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(180 / math.pi) /
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math.cos(center.latitude * math.pi / 180);
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return LatLngBounds(
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southwest:
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LatLng(center.latitude - latDelta, center.longitude - lngDelta),
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northeast:
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LatLng(center.latitude + latDelta, center.longitude + lngDelta),
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);
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}
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/// Downloads map tiles for a specified radius around a coordinate.
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///
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/// [center] is the midpoint of the region.
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/// [styleUrl] is the style to download (e.g. from IntaleqStyles).
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/// [radiusKm] defines the extent of the download.
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void downloadRegion(
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LatLng center, {
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required String styleUrl,
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double radiusKm = 5.0,
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double minZoom = 6.0,
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double maxZoom = 16.0,
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}) {
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// Debounce: Wait for user to stop moving for 2 seconds before starting download
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_debounceTimer?.cancel();
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_debounceTimer = Timer(const Duration(seconds: 2), () async {
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if (_isDownloading) return;
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// Avoid re-downloading if the user hasn't moved significantly (e.g. > 3km)
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if (_lastDownloadedCenter != null) {
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double distance = _calculateDistance(center, _lastDownloadedCenter!);
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if (distance < 3.0) return;
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}
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_isDownloading = true;
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try {
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final bounds = _calculateBounds(center, radiusKm);
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// iOS native crash guard for relative assets - only download remote styles
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// because local assets are already on disk.
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if (styleUrl.startsWith('asset://') || (Platform.isIOS && !styleUrl.startsWith('http'))) {
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return;
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}
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final regionDefinition = OfflineRegionDefinition(
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bounds: bounds,
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mapStyleUrl: styleUrl,
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minZoom: minZoom,
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maxZoom: maxZoom,
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);
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_lastDownloadedCenter = center;
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// Use maplibre_gl top-level function
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await downloadOfflineRegion(
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regionDefinition,
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metadata: {
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'name': 'Intaleq-${center.latitude}-${center.longitude}',
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'downloadDate': DateTime.now().toIso8601String(),
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},
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);
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} catch (e) {
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// Silently fail or log in debug
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print("❌ [OfflineService] Download failed: $e");
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} finally {
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_isDownloading = false;
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}
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});
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}
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/// Helper to calculate distance in km using Haversine formula.
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double _calculateDistance(LatLng p1, LatLng p2) {
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var p = 0.017453292519943295;
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var c = math.cos;
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var a = 0.5 -
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c((p2.latitude - p1.latitude) * p) / 2 +
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c(p1.latitude * p) *
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c(p2.latitude * p) *
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(1 - c((p2.longitude - p1.longitude) * p)) /
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2;
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return 12742 * math.asin(math.sqrt(a));
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}
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/// Clears all offline map regions and tiles.
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Future<void> clearCache() async {
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try {
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final List<OfflineRegion> regions = await getListOfRegions();
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for (var region in regions) {
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await deleteOfflineRegion(region.id);
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}
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} catch (_) {}
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}
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}
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