import Combine

public extension Bus {
  final class Async<Src, Dst> {
    let v = PassthroughSubject<Src, Never>()
    var subscriptions = [AnyCancellable]()

    public init(
      _ handler: @escaping ((Src) -> Dst?),
      _ src: String,
      _ dst: String
    ) {
      // Вход.
      Bus.receiveSync(
        [src],
        { [weak self] _, v in self?.v.send(v) },
        &subscriptions
      )
      // Выход.
      Bus.sendSync(
        dst,
        v
          .compactMap { (v: Src) in handler(v) }
          // Асинхронно.
          .receive(on: DispatchQueue.main)
          .eraseToAnyPublisher(),
        &subscriptions
      )
    }
  }
}