protect<T> static method

Implementation

static Future<T> protect<T>(
  Future<T> Function() callback, {
  bool exclusive = true,
  String tag = 'mutex',
}) async {
  Mutex? mutex = exclusive ? _guards[tag] : Mutex();
  if (mutex == null) {
    mutex = Mutex();
    _guards[tag] = mutex;
  }

  return await mutex.protect(() async {
    // Web Locks API is unavailable for some reason, so proceed without it.
    if (!_locksAvailable()) {
      return await callback();
    }

    final Completer<T> completer = Completer();

    JSPromise function(JSAny? any) {
      return callback()
          .then((val) => completer.complete(val))
          .onError(
            (e, stackTrace) =>
                completer.completeError(e ?? Exception(), stackTrace),
          )
          .toJS;
    }

    try {
      await _requestLock(
        tag,
        {'mode': exclusive ? 'exclusive' : 'shared'}.jsify() as JSObject,
        function.toJS,
      ).toDart;
    } catch (e) {
      // If completer is completed, then the exception is already handled.
      if (!completer.isCompleted) {
        rethrow;
      }
    }

    return await completer.future;
  });
}