[mob][photos] Create a SearchFilterDataProvider which will be used to update the recommended and applied filters list and make it possible to listen to applied and recommended state changes separately from it

mobile/lib/ui/viewer/gallery/state/search_filter_data_provider.dart

@@ -0,0 +1,78 @@
+import "package:flutter/material.dart";
+import "package:photos/models/search/hierarchical/hierarchical_search_filter.dart";
+
+class SearchFilterDataProvider {
+  final _appliedFiltersNotifier = _AppliedFiltersNotifier();
+  final _recommendedFiltersNotifier = _RecommendedFiltersNotifier();
+
+  get recommendations => _recommendedFiltersNotifier.recommendedFilters;
+  get appliedFilters => _appliedFiltersNotifier.appliedFilters;
+
+  void addRecommendations(List<HierarchicalSearchFilter> filters) {
+    _recommendedFiltersNotifier.addFilters(filters);
+  }
+
+  void applyFilters(List<HierarchicalSearchFilter> filters) {
+    _appliedFiltersNotifier.addFilters(filters);
+    _recommendedFiltersNotifier.removeFilters(filters);
+  }
+
+  void removeAppliedFilters(List<HierarchicalSearchFilter> filters) {
+    _appliedFiltersNotifier.removeFilters(filters);
+    _recommendedFiltersNotifier.addFilters(filters);
+  }
+
+  void clearRecommendations() {
+    _recommendedFiltersNotifier.clearFilters();
+  }
+
+  void addListener({
+    bool toApplied = false,
+    bool toRecommended = false,
+    required VoidCallback listener,
+  }) {
+    if (toApplied) {
+      _appliedFiltersNotifier.addListener(listener);
+    }
+    if (toRecommended) {
+      _recommendedFiltersNotifier.addListener(listener);
+    }
+  }
+}
+
+class _AppliedFiltersNotifier extends ChangeNotifier {
+  final List<HierarchicalSearchFilter> _appliedFilters = [];
+
+  List<HierarchicalSearchFilter> get appliedFilters => _appliedFilters;
+
+  void addFilters(List<HierarchicalSearchFilter> filters) {
+    _appliedFilters.addAll(filters);
+    notifyListeners();
+  }
+
+  void removeFilters(List<HierarchicalSearchFilter> filters) {
+    _appliedFilters.removeWhere((filter) => filters.contains(filter));
+    notifyListeners();
+  }
+}
+
+class _RecommendedFiltersNotifier extends ChangeNotifier {
+  final List<HierarchicalSearchFilter> _recommendedFilters = [];
+
+  List<HierarchicalSearchFilter> get recommendedFilters => _recommendedFilters;
+
+  void addFilters(List<HierarchicalSearchFilter> filters) {
+    _recommendedFilters.addAll(filters);
+    notifyListeners();
+  }
+
+  void removeFilters(List<HierarchicalSearchFilter> filters) {
+    _recommendedFilters.removeWhere((filter) => filters.contains(filter));
+    notifyListeners();
+  }
+
+  void clearFilters() {
+    _recommendedFilters.clear();
+    notifyListeners();
+  }
+}