/**
 * Copyright (C) 2014-2016 Typesafe Inc. <http://www.typesafe.com>
 */
package akka.stream.scaladsl

import scala.concurrent.Await
import scala.concurrent.Future
import scala.concurrent.duration._
import scala.concurrent.forkjoin.ThreadLocalRandom
import scala.util.control.NoStackTrace
import akka.stream.ActorMaterializer
import akka.stream.stage._
import akka.stream.testkit._
import akka.stream.testkit.Utils._
import akka.testkit.TestLatch
import akka.testkit.TestProbe
import akka.stream.ActorAttributes.supervisionStrategy
import akka.stream.Supervision.resumingDecider
import akka.stream.impl.ReactiveStreamsCompliance
import scala.util.Try
import scala.concurrent.ExecutionContext
import scala.util.Failure
import scala.util.Success
import scala.annotation.tailrec
import scala.concurrent.Promise
import java.util.concurrent.atomic.AtomicInteger
import java.util.concurrent.LinkedBlockingQueue
import org.scalatest.concurrent.ScalaFutures

class FlowMapAsyncSpec extends AkkaSpec with ScalaFutures {

  implicit val materializer = ActorMaterializer()

  "A Flow with mapAsync" must {

    "produce future elements" in assertAllStagesStopped {
      val c = TestSubscriber.manualProbe[Int]()
      implicit val ec = system.dispatcher
      val p = Source(1 to 3).mapAsync(4)(n ⇒ Future(n)).runWith(Sink.fromSubscriber(c))
      val sub = c.expectSubscription()
      sub.request(2)
      c.expectNext(1)
      c.expectNext(2)
      c.expectNoMsg(200.millis)
      sub.request(2)
      c.expectNext(3)
      c.expectComplete()
    }

    "produce future elements in order" in {
      val c = TestSubscriber.manualProbe[Int]()
      implicit val ec = system.dispatcher
      val p = Source(1 to 50).mapAsync(4)(n ⇒ Future {
        Thread.sleep(ThreadLocalRandom.current().nextInt(1, 10))
        n
      }).to(Sink.fromSubscriber(c)).run()
      val sub = c.expectSubscription()
      sub.request(1000)
      for (n ← 1 to 50) c.expectNext(n)
      c.expectComplete()
    }

    "not run more futures than requested parallelism" in {
      val probe = TestProbe()
      val c = TestSubscriber.manualProbe[Int]()
      implicit val ec = system.dispatcher
      val p = Source(1 to 20).mapAsync(8)(n ⇒ Future {
        probe.ref ! n
        n
      }).to(Sink.fromSubscriber(c)).run()
      val sub = c.expectSubscription()
      probe.expectNoMsg(500.millis)
      sub.request(1)
      probe.receiveN(9).toSet should be((1 to 9).toSet)
      probe.expectNoMsg(500.millis)
      sub.request(2)
      probe.receiveN(2).toSet should be(Set(10, 11))
      probe.expectNoMsg(500.millis)
      sub.request(10)
      probe.receiveN(9).toSet should be((12 to 20).toSet)
      probe.expectNoMsg(200.millis)

      for (n ← 1 to 13) c.expectNext(n)
      c.expectNoMsg(200.millis)
    }

    "signal future failure" in assertAllStagesStopped {
      val latch = TestLatch(1)
      val c = TestSubscriber.manualProbe[Int]()
      implicit val ec = system.dispatcher
      val p = Source(1 to 5).mapAsync(4)(n ⇒ Future {
        if (n == 3) throw new RuntimeException("err1") with NoStackTrace
        else {
          Await.ready(latch, 10.seconds)
          n
        }
      }).to(Sink.fromSubscriber(c)).run()
      val sub = c.expectSubscription()
      sub.request(10)
      c.expectError().getMessage should be("err1")
      latch.countDown()
    }

    "signal error from mapAsync" in assertAllStagesStopped {
      val latch = TestLatch(1)
      val c = TestSubscriber.manualProbe[Int]()
      implicit val ec = system.dispatcher
      val p = Source(1 to 5).mapAsync(4)(n ⇒
        if (n == 3) throw new RuntimeException("err2") with NoStackTrace
        else {
          Future {
            Await.ready(latch, 10.seconds)
            n
          }
        }).
        to(Sink.fromSubscriber(c)).run()
      val sub = c.expectSubscription()
      sub.request(10)
      c.expectError().getMessage should be("err2")
      latch.countDown()
    }

    "resume after future failure" in assertAllStagesStopped {
      val c = TestSubscriber.manualProbe[Int]()
      implicit val ec = system.dispatcher
      val p = Source(1 to 5)
        .mapAsync(4)(n ⇒ Future {
          if (n == 3) throw new RuntimeException("err3") with NoStackTrace
          else n
        })
        .withAttributes(supervisionStrategy(resumingDecider))
        .to(Sink.fromSubscriber(c)).run()
      val sub = c.expectSubscription()
      sub.request(10)
      for (n ← List(1, 2, 4, 5)) c.expectNext(n)
      c.expectComplete()
    }

    "resume after multiple failures" in assertAllStagesStopped {
      val futures: List[Future[String]] = List(
        Future.failed(Utils.TE("failure1")),
        Future.failed(Utils.TE("failure2")),
        Future.failed(Utils.TE("failure3")),
        Future.failed(Utils.TE("failure4")),
        Future.failed(Utils.TE("failure5")),
        Future.successful("happy!"))

      Await.result(
        Source(futures)
          .mapAsync(2)(identity).withAttributes(supervisionStrategy(resumingDecider))
          .runWith(Sink.head), 3.seconds) should ===("happy!")
    }

    "finish after future failure" in assertAllStagesStopped {
      import system.dispatcher
      Await.result(Source(1 to 3).mapAsync(1)(n ⇒ Future {
        if (n == 3) throw new RuntimeException("err3b") with NoStackTrace
        else n
      }).withAttributes(supervisionStrategy(resumingDecider))
        .grouped(10)
        .runWith(Sink.head), 1.second) should be(Seq(1, 2))
    }

    "resume when mapAsync throws" in {
      val c = TestSubscriber.manualProbe[Int]()
      implicit val ec = system.dispatcher
      val p = Source(1 to 5)
        .mapAsync(4)(n ⇒
          if (n == 3) throw new RuntimeException("err4") with NoStackTrace
          else Future(n))
        .withAttributes(supervisionStrategy(resumingDecider))
        .to(Sink.fromSubscriber(c)).run()
      val sub = c.expectSubscription()
      sub.request(10)
      for (n ← List(1, 2, 4, 5)) c.expectNext(n)
      c.expectComplete()
    }

    "signal NPE when future is completed with null" in {
      val c = TestSubscriber.manualProbe[String]()
      val p = Source(List("a", "b")).mapAsync(4)(elem ⇒ Future.successful(null)).to(Sink.fromSubscriber(c)).run()
      val sub = c.expectSubscription()
      sub.request(10)
      c.expectError().getMessage should be(ReactiveStreamsCompliance.ElementMustNotBeNullMsg)
    }

    "resume when future is completed with null" in {
      val c = TestSubscriber.manualProbe[String]()
      val p = Source(List("a", "b", "c"))
        .mapAsync(4)(elem ⇒ if (elem == "b") Future.successful(null) else Future.successful(elem))
        .withAttributes(supervisionStrategy(resumingDecider))
        .to(Sink.fromSubscriber(c)).run()
      val sub = c.expectSubscription()
      sub.request(10)
      for (elem ← List("a", "c")) c.expectNext(elem)
      c.expectComplete()
    }

    "should handle cancel properly" in assertAllStagesStopped {
      val pub = TestPublisher.manualProbe[Int]()
      val sub = TestSubscriber.manualProbe[Int]()

      Source.fromPublisher(pub).mapAsync(4)(Future.successful).runWith(Sink.fromSubscriber(sub))

      val upstream = pub.expectSubscription()
      upstream.expectRequest()

      sub.expectSubscription().cancel()

      upstream.expectCancellation()

    }

    "not run more futures than configured" in assertAllStagesStopped {
      val parallelism = 8

      val counter = new AtomicInteger
      val queue = new LinkedBlockingQueue[(Promise[Int], Long)]

      val timer = new Thread {
        val delay = 50000 // nanoseconds
        var count = 0
        @tailrec final override def run(): Unit = {
          val cont = try {
            val (promise, enqueued) = queue.take()
            val wakeup = enqueued + delay
            while (System.nanoTime() < wakeup) {}
            counter.decrementAndGet()
            promise.success(count)
            count += 1
            true
          } catch {
            case _: InterruptedException ⇒ false
          }
          if (cont) run()
        }
      }
      timer.start

      def deferred(): Future[Int] = {
        if (counter.incrementAndGet() > parallelism) Future.failed(new Exception("parallelism exceeded"))
        else {
          val p = Promise[Int]
          queue.offer(p -> System.nanoTime())
          p.future
        }
      }

      try {
        val N = 10000
        Source(1 to N)
          .mapAsync(parallelism)(i ⇒ deferred())
          .runFold(0)((c, _) ⇒ c + 1)
          .futureValue(PatienceConfig(3.seconds)) should ===(N)
      } finally {
        timer.interrupt()
      }
    }

  }

}