ZIO learning - an enhanced authentication service with http service used multiple times / published by https://github.com/dacr/code-examples-manager #4917e032-083a-4844-8104-3044fcb53f3e/3bc6f193ec7ef8e5d1a52073e811c8ac3a731355

zio-learning-14-service-4.sc

// summary : ZIO learning - an enhanced authentication service with http service used multiple times
// keywords : scala, zio, learning, authentication, pure-functional, @testable
// publish : gist
// authors : David Crosson
// license : Apache License Version 2.0 (https://www.apache.org/licenses/LICENSE-2.0.txt)
// id : 4917e032-083a-4844-8104-3044fcb53f3e
// created-on : 2022-01-16T19:12:41+01:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala "3.4.2"
//> using dep "dev.zio::zio:2.0.13"
//> using dep "fr.janalyse::zio-worksheet:2.0.13.0"
// ---------------------
import zio.*, zio.worksheet.*

// -------------------------------------------------------------
trait HttpService:
  def httpGet(query: String): Task[String]

case class HttpServiceLive() extends HttpService:
  override def httpGet(query: String): Task[String] =
    for
      httpProxy <- System.env("http_proxy")
      body      <- ZIO.succeed("secured-auth-token")
    yield body

object HttpService:
  val live = ZLayer.succeed(HttpServiceLive())

  def httpGet(query: String): RIO[HttpService, String] = ZIO.serviceWithZIO(_.httpGet(query))

// -------------------------------------------------------------

case class AuthToken(token: String)

trait Authenticator:
  def authenticate: Task[AuthToken]

case class AuthenticatorLive(httpService: HttpService) extends Authenticator:
  override def authenticate: Task[AuthToken] =
    for
      username <- System.env("APP_USERNAME")
      password <- System.env("APP_PASSWORD")
      body     <- httpService.httpGet("http://127.0.0.1/auth")
      token     = "secured-auth-token"
    yield AuthToken(token)

object Authenticator:
  val live = ZLayer(
    for httpService <- ZIO.service[HttpService]
    yield AuthenticatorLive(httpService)
  )

  def authenticate: RIO[Authenticator, AuthToken] = ZIO.serviceWithZIO(_.authenticate)

// -------------------------------------------------------------

val app: ZIO[HttpService & Authenticator, Throwable, Unit] =
  for
    _     <- Console.printLine("started")
    token <- Authenticator.authenticate
    _     <- Console.printLine(s"got token $token")
  yield ()

// -------------------------------------------------------------

// -- Better to write :
val layers    = ZLayer.make[HttpService & Authenticator](
  HttpService.live,
  Authenticator.live
)
// -- Rather than that which requires to resolve by yourself the dependencies graph
val layersAlt = HttpService.live >>> Authenticator.live ++ HttpService.live

// -------------------------------------------------------------
// -- And even better we can use provide in order to let ZIO build the dependency graph for us :)
app.provide(HttpService.live, Authenticator.live).unsafeRun