Finch Auth

finch-auth.scala

def auth0[A, B](doAuth: Request => Future[A])(e: Endpoint[B])(implicit 
  adjoin: PairAdjoin[A, B]
): Endpoint[adjoin.Out] = new Endpoint[adjoin.Out] {
  def apply(input: Input): Option[(Input, () => Future[Output[adjoin.Out]])] =
    e(input).map {
      case (remainder, output) =>
        (remainder, () => for { 
          a <- doAuth(input.request)
          ob <- output()
        } yield b.copy(value = adjoin(a, b.value)))
    }
}

case class User(id: Int)

val auth: Endpoint[A] => Endpoint[User :: A :: HNil] = auth0(req => Future.value(User(1)))

// Usage

auth(put("users" / int)) { (u: User, id: Int) =>
  ...
}