A KV that can be observed for changes to key bindings.

observable_kv.dart

/// A KV that can be observed for changes to key bindings.
class ObservableKV {
  ObservableKV(this._kv);
  final KV _kv;
  final _listeners = <void Function(String, Object?)>[];

  Stream<(Object, Object?)> observe(String prefix) {
    late final StreamController<(Object, Object?)> controller;

    void listener(String key, Object? value) {
      if (key.startsWith(prefix)) {
        controller.sink.add((key, value));
      }
    }

    controller = StreamController<(Object, Object?)>(
      onListen: () => _listeners.add(listener),
      onCancel: () => _listeners.remove(listener),
    );
    return controller.stream;
  }

  Future<Object?> get(String key) => _kv.get(key);

  Future<Object?> set(String key, String? value) async {
    final old = _kv.set(key, value);
    final listeners = _listeners.toList();
    scheduleMicrotask(() {
      for (final listener in listeners) {
        listener(key, value);
      }
    });
    return old;
  }

  Stream<(String, Object)> list(String prefix) => _kv.list(prefix);

  Future<void> snapshot() => _kv.snapshot();

  Future<void> dispose() async => _listeners.clear();
}