chooser.scala

  private[this] def picker[Question, Yes, No, Value](
    question: Question, onSuccess: Yes => Left[Value, Unit]
  )(
    implicit mYes: Manifest[Yes], mNo: Manifest[No]
  ): Future[Either[Value, Unit]] = {
    // Promise for fallbacking that we're never going to fulfill.
    val unfulfilledPromise = Promise()

    val questions = actors.map { actor => actor ? question }

    val successQuestions = questions.map {
      _ mapTo mYes map onSuccess fallbackTo(unfulfilledPromise)
    }
    val success= Future.firstCompletedOf(successQuestions)

    val failureQuestions = questions.map { _ mapTo mNo }
    val failure = Future.sequence(failureQuestions) map { _ => Right() }

    Future.firstCompletedOf(Seq(success, failure))
  }