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lib/features/core/utils/mutex.dart

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+import 'dart:async';
+import 'dart:collection';
+import 'dart:ui';
+
+/// A simple Mutex implementation using a [Completer].
+class Mutex {
+  final _completerQueue = Queue<Completer>();
+
+  /// Runs the given [run] function-block in a thread-safe/blocked zone. A convenient `unlock()`
+  /// is provided, which can be called anywhere to signal re-entry.
+  FutureOr<T> lockAndRun<T>({
+    required FutureOr<T> Function(VoidCallback unlock) run,
+  }) async {
+    final completer = Completer();
+    _completerQueue.add(completer);
+    if (_completerQueue.first != completer) {
+      await _completerQueue.removeFirst().future;
+    }
+    final value = await run(() => completer.complete());
+    return value;
+  }
+
+  Future<void> get lastOperationCompletionAwaiter =>
+      _completerQueue.isNotEmpty ? _completerQueue.last.future : Future.value();
+}