feat(selection): implement multi-select functionality with action bar (#730) (#566)

lib/ui/component/multi_select_controller.dart

@@ -0,0 +1,121 @@
+import 'package:get/get.dart';
+import 'package:proxypin/utils/listenable_list.dart';
+
+class MultiSelectController {
+  final ListenableList<String> selectedIds = ListenableList<String>();
+
+  String? _anchorId;
+  RxBool selectionMode = false.obs;
+
+  bool get isSelectionMode => selectionMode.value;
+
+  int get selectedCount => selectedIds.length;
+
+  bool contains(String requestId) => selectedIds.contains(requestId);
+
+  void clear() {
+    if (selectedIds.isEmpty && !selectionMode.value) {
+      return;
+    }
+    selectedIds.clear();
+    _anchorId = null;
+    selectionMode.value = false;
+  }
+
+  void enterSelectionMode([String? requestId]) {
+    selectionMode.value = true;
+    if (requestId != null) {
+      selectedIds.add(requestId);
+      _anchorId = requestId;
+    }
+  }
+
+  void selectOnly(String requestId) {
+    selectionMode.value = true;
+    selectedIds
+      ..clear()
+      ..add(requestId);
+    _anchorId = requestId;
+  }
+
+  void toggleSelectionMode([String? requestId]) {
+    if (selectionMode.value) {
+      clear();
+    } else {
+      enterSelectionMode(requestId);
+    }
+  }
+
+  void toggle(String requestId) {
+    selectionMode.value = true;
+    if (selectedIds.contains(requestId)) {
+      selectedIds.remove(requestId);
+    } else {
+      selectedIds.add(requestId);
+    }
+
+    if (selectedIds.isEmpty) {
+      clear();
+      return;
+    }
+
+    _anchorId = requestId;
+  }
+
+  void selectRange(List<String> orderedIds, String requestId) {
+    final targetIndex = orderedIds.indexOf(requestId);
+    if (targetIndex < 0) {
+      return;
+    }
+
+    final anchorIndex = _anchorId == null ? -1 : orderedIds.indexOf(_anchorId!);
+    if (anchorIndex < 0) {
+      selectOnly(requestId);
+      return;
+    }
+
+    final start = anchorIndex < targetIndex ? anchorIndex : targetIndex;
+    final end = anchorIndex > targetIndex ? anchorIndex : targetIndex;
+    selectionMode.value = true;
+    selectedIds
+      ..clear()
+      ..addAll(orderedIds.sublist(start, end + 1));
+    _anchorId = requestId;
+  }
+
+  void prune(Iterable<String> visibleIds) {
+    final visibleIdSet = visibleIds.toSet();
+    selectedIds.removeWhere((requestId) => !visibleIdSet.contains(requestId));
+
+    if (selectedIds.isEmpty) {
+      clear();
+      return;
+    }
+
+    selectionMode.value = true;
+    if (_anchorId == null || !selectedIds.contains(_anchorId)) {
+      _anchorId = selectedIds.last;
+    }
+  }
+}
+
+class MultiSelectListener<T> extends ListenerListEvent<T> {
+  final Function(List<T> items) onChange;
+
+  MultiSelectListener(this.onChange);
+
+  @override
+  void onAdd(T item) => onChange.call([item]);
+
+  @override
+  void onRemove(T item) => onChange.call([item]);
+
+  @override
+  void onUpdate(T item) => onChange.call([item]);
+
+  @override
+  void onBatchRemove(List<T> items) => onChange.call(items);
+
+  @override
+  void clear(List<T> items) => onChange.call(items);
+}