Kanaka-io/play-monadic-actions

Hi! I have a case where I am retrieving an optional user (to see whether there exists already a user with the email adress that tries to sign up). And the happy path would be the case when there is None returned (then signup process goes on). Otherwise I want to return and tell the user that his email is already signed up. For me, the library seems not to be designed for such a use case. But maybe you can tell me some smart way to do it? Here is the code I want to transform:

def submit = silhouette.UnsecuredAction.async { implicit request: Request[AnyContent] =>
    SignUpForm.form.bindFromRequest.fold(
      form => Future.successful(BadRequest(views.html.signUp(form))),
      data => {
        val result = Redirect(routes.SignUpController.view()).flashing("info" -> Messages("sign.up.email.sent", data.email))
        val loginInfo = LoginInfo(CredentialsProvider.ID, data.email)
        userService.retrieve(loginInfo).flatMap {
          case Some(user) =>
            val url = routes.SignInController.view().absoluteURL()
            mailerClient.send(Email(
              subject = Messages("email.already.signed.up.subject"),
              from = Messages("email.from"),
              to = Seq(data.email),
              bodyText = Some(views.txt.emails.alreadySignedUp(user, url).body),
              bodyHtml = Some(views.html.emails.alreadySignedUp(user, url).body)
            ))

            Future.successful(result)
          case None =>
            val authInfo = passwordHasherRegistry.current.hash(data.password)
            val user = User(
              userID = UUID.randomUUID(),
              loginInfo = loginInfo,
              firstName = Some(data.firstName),
              lastName = Some(data.lastName),
              fullName = Some(data.firstName + " " + data.lastName),
              email = Some(data.email),
              avatarURL = None,
              activated = false
            )
            for {
              avatar <- avatarService.retrieveURL(data.email)
              user <- userService.save(user.copy(avatarURL = avatar))
              authInfo <- authInfoRepository.add(loginInfo, authInfo)
              authToken <- authTokenService.create(user.userID)
            } yield {
              val url = routes.ActivateAccountController.activate(authToken.id).absoluteURL()
              mailerClient.send(Email(
                subject = Messages("email.sign.up.subject"),
                from = Messages("email.from"),
                to = Seq(data.email),
                bodyText = Some(views.txt.emails.signUp(user, url).body),
                bodyHtml = Some(views.html.emails.signUp(user, url).body)
              ))

              silhouette.env.eventBus.publish(SignUpEvent(user, request))
              result
            }
        }
      }

(from here)