by akka typed

RegisterAFP2_Akka.sc

// program 中のregisterの持ち回りを避ける

import akka.typed._
import akka.typed.scaladsl.Actor
import akka.typed.scaladsl.Actor.immutable
import cats.data.{ReaderT, WriterT}
import cats.effect.IO
import cats.instances.vector._

trait Command
final case class Purchase(amount: Int) extends Command
case object PrintTotal extends Command

object CashRegister {
  def apply(total: Int): Behavior[Command] = behavior(total)
  private def behavior(total: Int): Behavior[Command] = immutable {
    case (_, Purchase(amount)) => println(amount); behavior(total + amount)
    case (_, PrintTotal)       => println(total); Actor.same
  }
}
type PurchaseHistory = Vector[Purchase]
def execute(p: Purchase)
  : ReaderT[WriterT[IO, PurchaseHistory, ?], ActorRef[Command], Unit] =
  ReaderT { actor =>
    WriterT.lift[IO, PurchaseHistory, Unit](IO { actor ! p }) tell Vector(p)
  }

// test -------------------------------------------------------------------
val p1 = Purchase(100)
val p2 = Purchase(50)

def program = for {
  _ <- execute(p1)
  _ <- execute(p2)
} yield ()

val root = Actor.deferred[Nothing] { ctx =>
  val register = ctx.spawn(CashRegister(0), "register1")

  val (h, _) = program.run(register).run.unsafeRunSync()
  register ! PrintTotal

  //再実行
  val register2 = ctx.spawn(CashRegister(10), "register2")
  h.foreach(a => register2 ! a)
  register2 ! PrintTotal

  Actor.empty
}
ActorSystem[Nothing](root, "RegisterSample")
Thread.sleep(2000)