RecommendAFriendAbbreviated.scala

object RecommendAFriend {
  type RecommendAFriendResult = Either[RecommendAFriendError, Seq[ReferralOutcome]]
  type RecommendAFriend = (UserId, NewAccountDetails) => Future[Either[RecommendAFriendError, Seq[ReferralOutcome]]]
  type ValidateNewAccount = NewAccountDetails => Option[RecommendAFriendError]
  type FindUser = UserId => Future[Option[User]]
  type CreateFriend = NewAccountDetails => Future[User]
  
  def apply(v: ValidateNewAccount, f: FindUser, c: CreateFriend, p: ReferralPolicy)
           (u: UserId, n: NewAccountDetails): Future[RecommendAFriendResult] = 
    v(n) map { err } getOrElse { f(u) flatMap {
      case Some(us) => c(n) map { p(us, _) }
      case None => fer
    }}
  
  private def err(e: RecommendAFriendError) = Future.successful(Left(e))
  private val fer = Left(RecommendAFriendError("Error finding user"))
}