whut.scala

def initiateRegistration(userName: UserName, emailAddress: EmailAddress): Reader[RegistrationRepository, Future[Registration]] = Reader { repo =>
  val exists: OptionT[Future, (Registration, Registration)] = for {
    e <- repo.findByUserName(userName)
    u <- repo.findByEmailAddress(emailAddress)
  } yield (e, u)

  exists.run.flatMap {
    case None =>
        val hash = Random.alphanumeric take 32 mkString ""
        val reg = Registration(UUID.randomUUID(), userName, emailAddress, hash, DateTime.now())

        repo.add(reg).map(_ => reg)

    case _ =>
      Future.failed(new Exception("Thing already exists."))
  }
}