location: use LatLng instead of Tuple for coordinates, approximation when calling geocoder, locate without storing address line

lib/model/image_entry.dart

@@ -8,13 +8,14 @@ import 'package:aves/services/image_file_service.dart';
 import 'package:aves/services/metadata_service.dart';
 import 'package:aves/services/service_policy.dart';
 import 'package:aves/utils/change_notifier.dart';
+import 'package:aves/utils/math_utils.dart';
 import 'package:aves/utils/time_utils.dart';
 import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:geocoder/geocoder.dart';
+import 'package:latlong/latlong.dart';
 import 'package:path/path.dart' as ppath;
-import 'package:tuple/tuple.dart';
 
 import 'mime_types.dart';
 
@@ -295,9 +296,14 @@ class ImageEntry {
 
   bool get isLocated => _addressDetails != null;
 
-  Tuple2<double, double> get latLng => isCatalogued ? Tuple2(_catalogMetadata.latitude, _catalogMetadata.longitude) : null;
+  LatLng get latLng => isCatalogued ? LatLng(_catalogMetadata.latitude, _catalogMetadata.longitude) : null;
 
-  String get geoUri => hasGps ? 'geo:${_catalogMetadata.latitude},${_catalogMetadata.longitude}?q=${_catalogMetadata.latitude},${_catalogMetadata.longitude}' : null;
+  String get geoUri {
+    if (!hasGps) return null;
+    final latitude = roundToPrecision(_catalogMetadata.latitude, decimals: 6);
+    final longitude = roundToPrecision(_catalogMetadata.longitude, decimals: 6);
+    return 'geo:$latitude,$longitude?q=$latitude,$longitude';
+  }
 
   List<String> get xmpSubjects => _catalogMetadata?.xmpSubjects?.split(';')?.where((tag) => tag.isNotEmpty)?.toList() ?? [];
 
@@ -366,7 +372,6 @@ class ImageEntry {
         final address = addresses.first;
         addressDetails = AddressDetails(
           contentId: contentId,
-          addressLine: address.addressLine,
           countryCode: address.countryCode,
           countryName: address.countryName,
           adminArea: address.adminArea,
@@ -378,11 +383,29 @@ class ImageEntry {
     }
   }
 
+  Future<String> findAddressLine() async {
+    final latitude = _catalogMetadata?.latitude;
+    final longitude = _catalogMetadata?.longitude;
+    if (latitude == null || longitude == null || (latitude == 0 && longitude == 0)) return null;
+
+    final coordinates = Coordinates(latitude, longitude);
+    try {
+      final addresses = await Geocoder.local.findAddressesFromCoordinates(coordinates);
+      if (addresses != null && addresses.isNotEmpty) {
+        final address = addresses.first;
+        return address.addressLine;
+      }
+    } catch (error, stackTrace) {
+      debugPrint('$runtimeType findAddressLine failed with path=$path coordinates=$coordinates error=$error\n$stackTrace');
+    }
+    return null;
+  }
+
   String get shortAddress {
     if (!isLocated) return '';
 
-    // admin area examples: Seoul, Geneva, null
+    // `admin area` examples: Seoul, Geneva, null
-    // locality examples: Mapo-gu, Geneva, Annecy
+    // `locality` examples: Mapo-gu, Geneva, Annecy
     return {
       _addressDetails.countryName,
       _addressDetails.adminArea,
@@ -390,12 +413,13 @@ class ImageEntry {
     }.where((part) => part != null && part.isNotEmpty).join(', ');
   }
 
-  bool search(String query) {
+  bool search(String query) => {
-    if (bestTitle?.toUpperCase()?.contains(query) ?? false) return true;
+        bestTitle,
-    if (_catalogMetadata?.xmpSubjects?.toUpperCase()?.contains(query) ?? false) return true;
+        _catalogMetadata?.xmpSubjects,
-    if (_addressDetails?.addressLine?.toUpperCase()?.contains(query) ?? false) return true;
+        _addressDetails?.countryName,
-    return false;
+        _addressDetails?.adminArea,
-  }
+        _addressDetails?.locality,
+      }.any((s) => s != null && s.toUpperCase().contains(query));
 
   Future<void> _applyNewFields(Map newFields) async {
     final uri = newFields['uri'];

lib/model/image_metadata.dart

@@ -142,13 +142,12 @@ class OverlayMetadata {
 
 class AddressDetails {
   final int contentId;
-  final String addressLine, countryCode, countryName, adminArea, locality;
+  final String countryCode, countryName, adminArea, locality;
 
   String get place => locality != null && locality.isNotEmpty ? locality : adminArea;
 
   AddressDetails({
     this.contentId,
-    this.addressLine,
     this.countryCode,
     this.countryName,
     this.adminArea,
@@ -160,7 +159,6 @@ class AddressDetails {
   }) {
     return AddressDetails(
       contentId: contentId ?? this.contentId,
-      addressLine: addressLine,
       countryCode: countryCode,
       countryName: countryName,
       adminArea: adminArea,
@@ -171,7 +169,6 @@ class AddressDetails {
   factory AddressDetails.fromMap(Map map) {
     return AddressDetails(
       contentId: map['contentId'],
-      addressLine: map['addressLine'] ?? '',
       countryCode: map['countryCode'] ?? '',
       countryName: map['countryName'] ?? '',
       adminArea: map['adminArea'] ?? '',
@@ -181,7 +178,6 @@ class AddressDetails {
 
   Map<String, dynamic> toMap() => {
         'contentId': contentId,
-        'addressLine': addressLine,
         'countryCode': countryCode,
         'countryName': countryName,
         'adminArea': adminArea,
@@ -190,7 +186,7 @@ class AddressDetails {
 
   @override
   String toString() {
-    return 'AddressDetails{contentId=$contentId, addressLine=$addressLine, countryCode=$countryCode, countryName=$countryName, adminArea=$adminArea, locality=$locality}';
+    return 'AddressDetails{contentId=$contentId, countryCode=$countryCode, countryName=$countryName, adminArea=$adminArea, locality=$locality}';
   }
 }
 

lib/model/settings/coordinate_format.dart

@@ -1,4 +1,5 @@
 import 'package:aves/utils/geo_utils.dart';
+import 'package:latlong/latlong.dart';
 import 'package:tuple/tuple.dart';
 
 enum CoordinateFormat { dms, decimal }
@@ -15,12 +16,12 @@ extension ExtraCoordinateFormat on CoordinateFormat {
     }
   }
 
-  String format(Tuple2<double, double> latLng) {
+  String format(LatLng latLng) {
     switch (this) {
       case CoordinateFormat.dms:
         return toDMS(latLng).join(', ');
       case CoordinateFormat.decimal:
-        return [latLng.item1, latLng.item2].map((n) => n.toStringAsFixed(6)).join(', ');
+        return [latLng.latitude, latLng.longitude].map((n) => n.toStringAsFixed(6)).join(', ');
       default:
         return toString();
     }

lib/model/source/location.dart

@@ -1,3 +1,5 @@
+import 'dart:math';
+
 import 'package:aves/model/filters/location.dart';
 import 'package:aves/model/image_entry.dart';
 import 'package:aves/model/image_metadata.dart';
@@ -30,15 +32,25 @@ mixin LocationMixin on SourceBase {
     final todo = byLocated[false] ?? [];
     if (todo.isEmpty) return;
 
-    // cache known locations to avoid querying the geocoder unless necessary
+    // geocoder calls take between 150ms and 250ms
-    // measuring the time it takes to process ~3000 coordinates (with ~10% of duplicates)
+    // approximation and caching can reduce geocoder usage
-    // does not clearly show whether it is an actual optimization,
+    // for example, for a set of 2932 entries:
-    // as results vary wildly (durations in "min:sec"):
+    // - 2476 calls (84%) when approximating to 6 decimal places (~10cm - individual humans)
-    // - with no cache: 06:17, 08:36, 08:34
+    // - 2433 calls (83%) when approximating to 5 decimal places (~1m - individual trees, houses)
-    // - with cache: 08:28, 05:42, 08:03, 05:58
+    // - 2277 calls (78%) when approximating to 4 decimal places (~10m - individual street, large buildings)
-    // anyway, in theory it should help!
+    // - 1521 calls (52%) when approximating to 3 decimal places (~100m - neighborhood, street)
-    final knownLocations = <Tuple2<double, double>, AddressDetails>{};
+    // -  652 calls (22%) when approximating to 2 decimal places (~1km - town or village)
-    byLocated[true]?.forEach((entry) => knownLocations.putIfAbsent(entry.latLng, () => entry.addressDetails));
+    // cf https://en.wikipedia.org/wiki/Decimal_degrees#Precision
+    final latLngFactor = pow(10, 2);
+    Tuple2 approximateLatLng(ImageEntry entry) {
+      final lat = entry.catalogMetadata?.latitude;
+      final lng = entry.catalogMetadata?.longitude;
+      if (lat == null || lng == null) return null;
+      return Tuple2((lat * latLngFactor).round(), (lng * latLngFactor).round());
+    }
+
+    final knownLocations = <Tuple2, AddressDetails>{};
+    byLocated[true]?.forEach((entry) => knownLocations.putIfAbsent(approximateLatLng(entry), () => entry.addressDetails));
 
     var progressDone = 0;
     final progressTotal = todo.length;
@@ -46,13 +58,14 @@ mixin LocationMixin on SourceBase {
 
     final newAddresses = <AddressDetails>[];
     await Future.forEach<ImageEntry>(todo, (entry) async {
-      if (knownLocations.containsKey(entry.latLng)) {
+      final latLng = approximateLatLng(entry);
-        entry.addressDetails = knownLocations[entry.latLng]?.copyWith(contentId: entry.contentId);
+      if (knownLocations.containsKey(latLng)) {
+        entry.addressDetails = knownLocations[latLng]?.copyWith(contentId: entry.contentId);
       } else {
         await entry.locate(background: true);
         // it is intended to insert `null` if the geocoder failed,
         // so that we skip geocoding of following entries with the same coordinates
-        knownLocations[entry.latLng] = entry.addressDetails;
+        knownLocations[latLng] = entry.addressDetails;
       }
       if (entry.isLocated) {
         newAddresses.add(entry.addressDetails);

lib/utils/constants.dart

@@ -1,6 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/painting.dart';
-import 'package:tuple/tuple.dart';
+import 'package:latlong/latlong.dart';
 
 class Constants {
   // as of Flutter v1.22.3, overflowing `Text` miscalculates height and some text (e.g. 'Å') is clipped
@@ -21,7 +21,7 @@ class Constants {
   static const String overlayUnknown = '—'; // em dash
   static const String infoUnknown = 'unknown';
 
-  static const pointNemo = Tuple2(-48.876667, -123.393333);
+  static final pointNemo = LatLng(-48.876667, -123.393333);
 
   static const int infoGroupMaxValueLength = 140;
 

lib/utils/geo_utils.dart

@@ -1,15 +1,12 @@
-import 'dart:math';
+import 'package:aves/utils/math_utils.dart';
-
 import 'package:intl/intl.dart';
-import 'package:tuple/tuple.dart';
+import 'package:latlong/latlong.dart';
 
 String _decimal2sexagesimal(final double degDecimal) {
-  double _round(final double value, {final int decimals = 6}) => (value * pow(10, decimals)).round() / pow(10, decimals);
-
   List<int> _split(final double value) {
     // NumberFormat is necessary to create digit after comma if the value
     // has no decimal point (only necessary for browser)
-    final tmp = NumberFormat('0.0#####').format(_round(value, decimals: 10)).split('.');
+    final tmp = NumberFormat('0.0#####').format(roundToPrecision(value, decimals: 10)).split('.');
     return <int>[
       int.parse(tmp[0]).abs(),
       int.parse(tmp[1]),
@@ -21,14 +18,14 @@ String _decimal2sexagesimal(final double degDecimal) {
   final min = _split(minDecimal)[0];
   final sec = (minDecimal - min) * 60;
 
-  return '$deg° $min′ ${_round(sec, decimals: 2).toStringAsFixed(2)}″';
+  return '$deg° $min′ ${roundToPrecision(sec, decimals: 2).toStringAsFixed(2)}″';
 }
 
 // return coordinates formatted as DMS, e.g. ['41° 24′ 12.2″ N', '2° 10′ 26.5″ E']
-List<String> toDMS(Tuple2<double, double> latLng) {
+List<String> toDMS(LatLng latLng) {
   if (latLng == null) return [];
-  final lat = latLng.item1;
+  final lat = latLng.latitude;
-  final lng = latLng.item2;
+  final lng = latLng.longitude;
   return [
     '${_decimal2sexagesimal(lat)} ${lat < 0 ? 'S' : 'N'}',
     '${_decimal2sexagesimal(lng)} ${lng < 0 ? 'W' : 'E'}',

lib/utils/math_utils.dart

@@ -1,5 +1,7 @@
 import 'dart:math';
 
+import 'package:flutter/foundation.dart';
+
 final double _log2 = log(2);
 const double _piOver180 = pi / 180.0;
 
@@ -9,6 +11,8 @@ double toRadians(num degrees) => degrees * _piOver180;
 
 int highestPowerOf2(num x) => x < 1 ? 0 : pow(2, (log(x) / _log2).floor());
 
+double roundToPrecision(final double value, {@required final int decimals}) => (value * pow(10, decimals)).round() / pow(10, decimals);
+
 // e.g. x=12345, precision=3 should return 13000
 int ceilBy(num x, int precision) {
   final factor = pow(10, precision);

lib/widgets/fullscreen/debug/db.dart

@@ -128,7 +128,6 @@ class _DbTabState extends State<DbTab> {
                 Text('DB address:${data == null ? ' no row' : ''}'),
                 if (data != null)
                   InfoRowGroup({
-                    'addressLine': '${data.addressLine}',
                     'countryCode': '${data.countryCode}',
                     'countryName': '${data.countryName}',
                     'adminArea': '${data.adminArea}',

lib/widgets/fullscreen/info/location_section.dart

@@ -12,6 +12,7 @@ import 'package:aves/widgets/fullscreen/info/maps/google_map.dart';
 import 'package:aves/widgets/fullscreen/info/maps/leaflet_map.dart';
 import 'package:aves/widgets/fullscreen/info/maps/marker.dart';
 import 'package:flutter/material.dart';
+import 'package:tuple/tuple.dart';
 
 class LocationSection extends StatefulWidget {
   final CollectionLens collection;
@@ -79,11 +80,9 @@ class _LocationSectionState extends State<LocationSection> with TickerProviderSt
     final showMap = (_loadedUri == entry.uri) || (entry.hasGps && widget.visibleNotifier.value);
     if (showMap) {
       _loadedUri = entry.uri;
-      var location = '';
       final filters = <LocationFilter>[];
       if (entry.isLocated) {
         final address = entry.addressDetails;
-        location = address.addressLine;
         final country = address.countryName;
         if (country != null && country.isNotEmpty) filters.add(LocationFilter(LocationLevel.country, '$country${LocationFilter.locationSeparator}${address.countryCode}'));
         final place = address.place;
@@ -114,7 +113,8 @@ class _LocationSectionState extends State<LocationSection> with TickerProviderSt
               vsync: this,
               child: settings.infoMapStyle.isGoogleMaps
                   ? EntryGoogleMap(
-                      latLng: entry.latLng,
+                      // `LatLng` used by `google_maps_flutter` is not the one from `latlong` package
+                      latLng: Tuple2<double, double>(entry.latLng.latitude, entry.latLng.longitude),
                       geoUri: entry.geoUri,
                       initialZoom: settings.infoMapZoom,
                       markerId: entry.uri ?? entry.path,
@@ -130,11 +130,7 @@ class _LocationSectionState extends State<LocationSection> with TickerProviderSt
                     ),
             ),
           ),
-          if (entry.hasGps)
+          if (entry.hasGps) _AddressInfoGroup(entry: entry),
-            InfoRowGroup(Map.fromEntries([
-              MapEntry('Coordinates', settings.coordinateFormat.format(entry.latLng)),
-              if (location.isNotEmpty) MapEntry('Address', location),
-            ])),
           if (filters.isNotEmpty)
             Padding(
               padding: EdgeInsets.symmetric(horizontal: AvesFilterChip.outlineWidth / 2) + EdgeInsets.only(top: 8),
@@ -160,6 +156,41 @@ class _LocationSectionState extends State<LocationSection> with TickerProviderSt
   void _handleChange() => setState(() {});
 }
 
+class _AddressInfoGroup extends StatefulWidget {
+  final ImageEntry entry;
+
+  const _AddressInfoGroup({@required this.entry});
+
+  @override
+  _AddressInfoGroupState createState() => _AddressInfoGroupState();
+}
+
+class _AddressInfoGroupState extends State<_AddressInfoGroup> {
+  Future<String> _addressLineLoader;
+
+  ImageEntry get entry => widget.entry;
+
+  @override
+  void initState() {
+    super.initState();
+    _addressLineLoader = entry.findAddressLine();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return FutureBuilder<String>(
+      future: _addressLineLoader,
+      builder: (context, snapshot) {
+        final address = !snapshot.hasError && snapshot.connectionState == ConnectionState.done ? snapshot.data : '';
+        return InfoRowGroup({
+          'Coordinates': settings.coordinateFormat.format(entry.latLng),
+          if (address.isNotEmpty) 'Address': address,
+        });
+      },
+    );
+  }
+}
+
 // browse providers at https://leaflet-extras.github.io/leaflet-providers/preview/
 enum EntryMapStyle { googleNormal, googleHybrid, googleTerrain, osmHot, stamenToner, stamenWatercolor }
 

lib/widgets/fullscreen/info/maps/leaflet_map.dart

@@ -5,7 +5,6 @@ import 'package:flutter/material.dart';
 import 'package:flutter_map/flutter_map.dart';
 import 'package:flutter_markdown/flutter_markdown.dart';
 import 'package:latlong/latlong.dart';
-import 'package:tuple/tuple.dart';
 import 'package:url_launcher/url_launcher.dart';
 
 import '../location_section.dart';
@@ -18,16 +17,15 @@ class EntryLeafletMap extends StatefulWidget {
   final Size markerSize;
   final WidgetBuilder markerBuilder;
 
-  EntryLeafletMap({
+  const EntryLeafletMap({
     Key key,
-    Tuple2<double, double> latLng,
+    this.latLng,
     this.geoUri,
     this.initialZoom,
     this.style,
     this.markerBuilder,
     this.markerSize,
-  })  : latLng = LatLng(latLng.item1, latLng.item2),
+  }) : super(key: key);
-        super(key: key);
 
   @override
   State<StatefulWidget> createState() => EntryLeafletMapState();

test/utils/geo_utils_test.dart

@@ -1,12 +1,13 @@
 import 'package:aves/utils/geo_utils.dart';
+import 'package:latlong/latlong.dart';
 import 'package:test/test.dart';
-import 'package:tuple/tuple.dart';
 
 void main() {
   test('Decimal degrees to DMS (sexagesimal)', () {
-    expect(toDMS(Tuple2(37.496667, 127.0275)), ['37° 29′ 48.00″ N', '127° 1′ 39.00″ E']); // Gangnam
+    expect(toDMS(LatLng(37.496667, 127.0275)), ['37° 29′ 48.00″ N', '127° 1′ 39.00″ E']); // Gangnam
-    expect(toDMS(Tuple2(78.9243503, 11.9230465)), ['78° 55′ 27.66″ N', '11° 55′ 22.97″ E']); // Ny-Ålesund
+    expect(toDMS(LatLng(78.9243503, 11.9230465)), ['78° 55′ 27.66″ N', '11° 55′ 22.97″ E']); // Ny-Ålesund
-    expect(toDMS(Tuple2(-38.6965891, 175.9830047)), ['38° 41′ 47.72″ S', '175° 58′ 58.82″ E']); // Taupo
+    expect(toDMS(LatLng(-38.6965891, 175.9830047)), ['38° 41′ 47.72″ S', '175° 58′ 58.82″ E']); // Taupo
-    expect(toDMS(Tuple2(-64.249391, -56.6556145)), ['64° 14′ 57.81″ S', '56° 39′ 20.21″ W']); // Marambio
+    expect(toDMS(LatLng(-64.249391, -56.6556145)), ['64° 14′ 57.81″ S', '56° 39′ 20.21″ W']); // Marambio
+    expect(toDMS(LatLng(0, 0)), ['0° 0′ 0.00″ N', '0° 0′ 0.00″ E']);
   });
 }

test/utils/math_utils_test.dart

@@ -21,6 +21,11 @@ void main() {
     expect(highestPowerOf2(-42), 0);
   });
 
+  test('rounding to a given precision after the decimal', () {
+    expect(roundToPrecision(1.2345678, decimals: 3), 1.235);
+    expect(roundToPrecision(0, decimals: 3), 0);
+  });
+
   test('rounding up to a given precision before the decimal', () {
     expect(ceilBy(12345.678, 3), 13000);
     expect(ceilBy(42, 3), 1000);