Cats Effect ConcurrentEffect example

ConcurrentEffectDemo.scala

package cats_effect_typeclass_exericise.concurrent_effect

import java.time.format.DateTimeFormatter

import cats.data.{Chain, EitherT, WriterT}
import cats.effect._

import scala.language.higherKinds

object Util {
  val formatter = DateTimeFormatter.ofPattern("mm:ss")

  def putIn(milli: Int, s: Any): String = {
    Thread.sleep(milli)
    val threadId      = Thread.currentThread.getId
    val currentMinSec = java.time.LocalTime.now.format(formatter)
    println(s"in thread($threadId) at $currentMinSec): $s")
    s.toString
  }
  def putLine(s: Any):   String = putIn(1000, s)
  def putIn1Sec(s: Any): String = putIn(1000, s)
  def putNow(s: Any):    String = putIn(0,    s)
  def putRnd(s: Any):    String = putIn((math.random * 1000 + 500).toInt, s)
}
import Util._


object ConcurrentEffectRunCancelableDemo extends IOApp {
  type EitherIO[T] = EitherT[IO, Throwable, T]
  type WriterIO[T] = WriterT[IO, Chain[String], T]

  val CEE: ConcurrentEffect[EitherIO] = implicitly[ConcurrentEffect[EitherIO]]
  val CEW: ConcurrentEffect[WriterIO] = implicitly[ConcurrentEffect[WriterIO]]

  def convert[F[_], G[_], A](fa: F[A])(implicit F: ConcurrentEffect[F], G: Concurrent[G]): G[A] = {
    G.cancelable { cb =>
      val token: CancelToken[F] = F.runCancelable(fa)(x => IO(cb(x))).unsafeRunSync()
      convert[F, G, Unit](token)
    }
  }
  def tell(line: String): WriterIO[Unit] = WriterT.tell(Chain(line))

  override def run(args: List[String]): IO[ExitCode] = {
    val a: EitherIO[String] = EitherT[IO, Throwable, String](IO(Right("1234")))
    val b: WriterIO[String] = convert[EitherIO, WriterIO, String](a)

    val d = for {
      v <- b
      _ <- tell("line A")
      _ <- tell("line B")
    } yield v
    putLine("before run")
    d.run.map { case (log, value) =>
      putLine(s"value=$value: log=$log")
      ExitCode.Success
    }
  }
  //  in thread(1)  at 10:08): before run
  //  in thread(11) at 10:09): value=1234: log=Chain(line A, line B)
  //
  //  Process finished with exit code 0
}