adts-in-practice.scala

import cats.effect.IO

class Server(http: Http, database: Database) {

  def process(request: Request): IO[Response] = {

    val respF =
      for {
        creds <- request.getCredentials()
        authorizedCreds <- authenticateUser(creds)
        userInfo <- getUserInfo(authorizedCreds)
        successfulResponse <- toSuccessfulResponse(userInfo)
      } yield successfulResponse

    respF.handleErrorWith(toFailedResponse)
  }

  def authenticateUser(creds: UserCredentials): IO[AuthCredentials] = ???

  def getUserInfo(authCreds: AuthCredentials): IO[UserInfo] = ???

  def toFailedResponse(err: Throwable): IO[Response] = ???

  def toSuccessfulResponse(userInfo: UserInfo): IO[UserInfoResponse] = ???

}

trait Request {
    def getCredentials(): IO[UserCredentials]
}

trait Http {
    def post(userCreds: UserCredentials): IO[AuthCredentials]
}

trait Database{
    def queryUser(userName: String): IO[UserInfo]
}

final case class UserCredentials(userId: String, password: String)

final case class AuthCredentials(userId: String, userName: String)

final case class UserInfo()

sealed trait Response

final case class UserInfoResponse(userInfo: UserInfo) extends Response

sealed trait CredentialErrorResponse

sealed trait AuthResponse
sealed trait AuthErrorResponse extends AuthResponse

sealed trait DBResponse
sealed trait DBErrorResponse extends DBResponse

final case class CredentialsMissing(msg: String) extends RuntimeException(msg) with CredentialErrorResponse
final case class UnauthorizedUser(msg: String) extends RuntimeException(msg) with CredentialErrorResponse
final case class NotFound(msg: String) extends RuntimeException(msg) with CredentialErrorResponse
final case class Forbidden(msg: String) extends RuntimeException(msg) with CredentialErrorResponse
final case class InternalServerError(msg: String) extends RuntimeException(msg) with CredentialErrorResponse

final case class AuthCredentialsResponse(authCredentials: AuthCredentials) extends AuthResponse

final case class UnauthorizedAuthUser(msg: String) extends RuntimeException(msg: String) with AuthErrorResponse
final case class AuthUserNotFound(msg: String) extends RuntimeException(msg: String) with AuthErrorResponse
final case class AuthServerError(msg: String) extends RuntimeException(msg: String) with AuthErrorResponse

final case class UserInfoFound() extends DBResponse
final case class UserInfoNotFound() extends DBResponse

final case class DBError(msg: String) extends RuntimeException(msg) with DBErrorResponse