feat: 5400 - flagging stores as favorite (#5533)

New file:
* `favorite_location_helper.dart`: Helper used to set/unset/sort stores as user favorites.

Impacted files:
* `dao_string_list.dart`: added a key for favorite price stores
* `search_location_preloaded_item.dart`: added a "favorite" `IconButton` for price locations

packages/smooth_app/lib/database/dao_string_list.dart

@@ -20,6 +20,9 @@ class DaoStringList extends AbstractDao {
   /// Key for the list of latest languages used in the app.
   static const String keyLanguages = 'languages';
 
+  /// Key for the list of favorite stores (for price additions).
+  static const String keyPriceStores = 'priceStores';
+
   /// Max lengths of each key (null means no limit).
   static const Map<String, int?> _maxLengths = <String, int?>{
     keySearchProductHistory: 10,

packages/smooth_app/lib/pages/locations/favorite_location_helper.dart

@@ -0,0 +1,48 @@
+import 'package:smooth_app/database/dao_string_list.dart';
+import 'package:smooth_app/database/local_database.dart';
+import 'package:smooth_app/pages/locations/osm_location.dart';
+
+/// Helper used to set/unset/sort stores as user favorites.
+class FavoriteLocationHelper {
+  static const String _key = DaoStringList.keyPriceStores;
+
+  /// Sets a store as a favorite store (or not, depending on [isFavorite]).
+  Future<void> setFavorite(
+    final LocalDatabase localDatabase,
+    final OsmLocation location,
+    final bool isFavorite,
+  ) async {
+    final DaoStringList daoStringList = DaoStringList(localDatabase);
+    final String locationKey = _locationToString(location);
+    await daoStringList.remove(_key, locationKey);
+    if (isFavorite) {
+      await daoStringList.add(_key, locationKey);
+    }
+  }
+
+  /// Returns true if a store was flagged as favorite.
+  bool isFavorite(
+    final LocalDatabase localDatabase,
+    final OsmLocation location,
+  ) {
+    final DaoStringList daoStringList = DaoStringList(localDatabase);
+    final List<String> favorites = daoStringList.getAll(_key);
+    return _isFavorite(favorites, location);
+  }
+
+  /// Returns true if a store was flagged as favorite, from stored keys.
+  bool _isFavorite(
+    final List<String> favorites,
+    final OsmLocation location,
+  ) {
+    for (final String favorite in favorites) {
+      if (favorite == _locationToString(location)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  String _locationToString(final OsmLocation location) =>
+      '${location.osmType}-${location.osmId}';
+}

packages/smooth_app/lib/pages/locations/search_location_preloaded_item.dart

@@ -4,6 +4,7 @@ import 'package:smooth_app/database/dao_osm_location.dart';
 import 'package:smooth_app/database/local_database.dart';
 import 'package:smooth_app/generic_lib/design_constants.dart';
 import 'package:smooth_app/generic_lib/widgets/smooth_card.dart';
+import 'package:smooth_app/pages/locations/favorite_location_helper.dart';
 import 'package:smooth_app/pages/locations/location_map_page.dart';
 import 'package:smooth_app/pages/locations/osm_location.dart';
 import 'package:smooth_app/pages/product/common/search_preloaded_item.dart';
@@ -20,10 +21,23 @@ class SearchLocationPreloadedItem extends SearchPreloadedItem {
     final BuildContext context, {
     final VoidCallback? onDismissItem,
   }) {
+    final LocalDatabase localDatabase = context.read<LocalDatabase>();
+    final bool isFavorite = FavoriteLocationHelper().isFavorite(
+      localDatabase,
+      osmLocation,
+    );
     final String? title = osmLocation.getTitle();
     final String? subtitle = osmLocation.getSubtitle();
     final Widget child = SmoothCard(
       child: ListTile(
+        leading: IconButton(
+          icon: Icon(isFavorite ? Icons.favorite : Icons.favorite_border),
+          onPressed: () async => FavoriteLocationHelper().setFavorite(
+            localDatabase,
+            osmLocation,
+            !isFavorite,
+          ),
+        ),
         onTap: () {
           if (popFirst) {
             // pops this result page