feat: new timeline multi-selection (#19443)

* feat: new timeline multiselection

* select all from bucket

* wip

* group multi-select

* group multi-select

* pr feedback

* pr feedback

* lint

mobile/lib/providers/timeline/multiselect.provider.dart

@@ -0,0 +1,144 @@
+import 'package:collection/collection.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+
+import 'package:immich_mobile/domain/models/asset/base_asset.model.dart';
+import 'package:immich_mobile/domain/services/timeline.service.dart';
+import 'package:immich_mobile/providers/infrastructure/timeline.provider.dart';
+
+final multiSelectProvider =
+    NotifierProvider<MultiSelectNotifier, MultiSelectState>(
+  MultiSelectNotifier.new,
+  dependencies: [timelineServiceProvider],
+);
+
+class MultiSelectState {
+  final Set<BaseAsset> selectedAssets;
+
+  MultiSelectState({
+    required this.selectedAssets,
+  });
+
+  bool get isEnabled => selectedAssets.isNotEmpty;
+
+  MultiSelectState copyWith({
+    Set<BaseAsset>? selectedAssets,
+  }) {
+    return MultiSelectState(
+      selectedAssets: selectedAssets ?? this.selectedAssets,
+    );
+  }
+
+  @override
+  String toString() => 'MultiSelectState(selectedAssets: $selectedAssets)';
+
+  @override
+  bool operator ==(covariant MultiSelectState other) {
+    if (identical(this, other)) return true;
+    final listEquals = const DeepCollectionEquality().equals;
+
+    return listEquals(other.selectedAssets, selectedAssets);
+  }
+
+  @override
+  int get hashCode => selectedAssets.hashCode;
+}
+
+class MultiSelectNotifier extends Notifier<MultiSelectState> {
+  late final TimelineService _timelineService;
+
+  @override
+  MultiSelectState build() {
+    _timelineService = ref.read(timelineServiceProvider);
+
+    return MultiSelectState(
+      selectedAssets: {},
+    );
+  }
+
+  void selectAsset(BaseAsset asset) {
+    if (state.selectedAssets.contains(asset)) {
+      return;
+    }
+
+    state = state.copyWith(
+      selectedAssets: {...state.selectedAssets, asset},
+    );
+  }
+
+  void deselectAsset(BaseAsset asset) {
+    if (!state.selectedAssets.contains(asset)) {
+      return;
+    }
+
+    state = state.copyWith(
+      selectedAssets: state.selectedAssets.where((a) => a != asset).toSet(),
+    );
+  }
+
+  void toggleAssetSelection(BaseAsset asset) {
+    if (state.selectedAssets.contains(asset)) {
+      deselectAsset(asset);
+    } else {
+      selectAsset(asset);
+    }
+  }
+
+  /// Bucket bulk operations
+  void selectBucket(int offset, int bucketCount) async {
+    final assets = await _timelineService.loadAssets(offset, bucketCount);
+    final selectedAssets = state.selectedAssets.toSet();
+
+    selectedAssets.addAll(assets);
+
+    state = state.copyWith(
+      selectedAssets: selectedAssets,
+    );
+  }
+
+  void deselectBucket(int offset, int bucketCount) async {
+    final assets = await _timelineService.loadAssets(offset, bucketCount);
+    final selectedAssets = state.selectedAssets.toSet();
+
+    selectedAssets.removeAll(assets);
+
+    state = state.copyWith(selectedAssets: selectedAssets);
+  }
+
+  void toggleBucketSelection(int offset, int bucketCount) async {
+    final assets = await _timelineService.loadAssets(offset, bucketCount);
+    toggleBucketSelectionByAssets(assets);
+  }
+
+  void toggleBucketSelectionByAssets(List<BaseAsset> bucketAssets) {
+    if (bucketAssets.isEmpty) return;
+
+    // Check if all assets in this bucket are currently selected
+    final allSelected =
+        bucketAssets.every((asset) => state.selectedAssets.contains(asset));
+
+    final selectedAssets = state.selectedAssets.toSet();
+
+    if (allSelected) {
+      // If all assets in this bucket are selected, deselect them
+      selectedAssets.removeAll(bucketAssets);
+    } else {
+      // If not all assets in this bucket are selected, select them all
+      selectedAssets.addAll(bucketAssets);
+    }
+
+    state = state.copyWith(selectedAssets: selectedAssets);
+  }
+}
+
+final bucketSelectionProvider = Provider.family<bool, List<BaseAsset>>(
+  (ref, bucketAssets) {
+    final selectedAssets =
+        ref.watch(multiSelectProvider.select((s) => s.selectedAssets));
+
+    if (bucketAssets.isEmpty) return false;
+
+    // Check if all assets in the bucket are selected
+    return bucketAssets.every((asset) => selectedAssets.contains(asset));
+  },
+  dependencies: [multiSelectProvider],
+);