pekko/akka-docs/rst/java/code/docs/stream/RateTransformationDocTest.java

/*
 * Copyright (C) 2015-2016 Typesafe Inc. <http://www.typesafe.com>
 */

package docs.stream;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.stream.DoubleStream;
import java.util.stream.Stream;

import akka.NotUsed;
import docs.AbstractJavaTest;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;
import static org.junit.Assert.*;

import akka.actor.ActorSystem;
import akka.japi.Pair;
import akka.japi.tuple.Tuple3;
import akka.stream.*;
import akka.stream.javadsl.*;
import akka.stream.testkit.TestPublisher;
import akka.stream.testkit.TestSubscriber;
import akka.stream.testkit.javadsl.TestSink;
import akka.stream.testkit.javadsl.TestSource;
import akka.testkit.JavaTestKit;
import akka.testkit.TestLatch;
import scala.collection.Iterator;
import scala.concurrent.Await;
import scala.concurrent.Future;
import scala.concurrent.duration.Duration;
import scala.util.Random;

public class RateTransformationDocTest extends AbstractJavaTest {

  static ActorSystem system;
  static Materializer mat;

  @BeforeClass
  public static void setup() {
    system = ActorSystem.create("RateTransformationDocTest");
    mat = ActorMaterializer.create(system);
  }

  @AfterClass
  public static void tearDown() {
    JavaTestKit.shutdownActorSystem(system);
    system = null;
    mat = null;
  }

  final Random r = new Random();

  @Test
  public void conflateShouldSummarize() throws Exception {
    //#conflate-summarize
    final Flow<Double, Tuple3<Double, Double, Integer>, NotUsed> statsFlow =
      Flow.of(Double.class)
        .conflateWithSeed(elem -> Collections.singletonList(elem), (acc, elem) -> {
          return Stream
            .concat(acc.stream(), Collections.singletonList(elem).stream())
            .collect(Collectors.toList());
        })
        .map(s -> {
          final Double mean = s.stream().mapToDouble(d -> d).sum() / s.size();
          final DoubleStream se = s.stream().mapToDouble(x -> Math.pow(x - mean, 2));
          final Double stdDev = Math.sqrt(se.sum() / s.size());
          return new Tuple3<>(stdDev, mean, s.size());
        });
    //#conflate-summarize

    final CompletionStage<List<Tuple3<Double, Double, Integer>>> fut = Source.repeat(0).map(i -> r.nextGaussian())
      .via(statsFlow)
      .grouped(10)
      .runWith(Sink.head(), mat);

    fut.toCompletableFuture().get(1, TimeUnit.SECONDS);
  }

  @Test
  public void conflateShouldSample() throws Exception {
    //#conflate-sample
    final Double p = 0.01;
    final Flow<Double, Double, NotUsed> sampleFlow = Flow.of(Double.class)
      .conflateWithSeed(elem -> Collections.singletonList(elem), (acc, elem) -> {
        if (r.nextDouble() < p) {
          return Stream
            .concat(acc.stream(), Collections.singletonList(elem).stream())
            .collect(Collectors.toList());
        }
        return acc;
      })
      .mapConcat(d -> d);
    //#conflate-sample

    final CompletionStage<Double> fut = Source.from(new ArrayList<Double>(Collections.nCopies(1000, 1.0)))
      .via(sampleFlow)
      .runWith(Sink.fold(0.0, (agg, next) -> agg + next), mat);

    final Double count = fut.toCompletableFuture().get(1, TimeUnit.SECONDS);
  }

  @Test
  public void expandShouldRepeatLast() throws Exception {
    //#expand-last
    final Flow<Double, Double, NotUsed> lastFlow = Flow.of(Double.class)
      .expand(in -> Stream.iterate(in, i -> i).iterator());
    //#expand-last

    final Pair<TestPublisher.Probe<Double>, CompletionStage<List<Double>>> probeFut = TestSource.<Double> probe(system)
      .via(lastFlow)
      .grouped(10)
      .toMat(Sink.head(), Keep.both())
      .run(mat);

    final TestPublisher.Probe<Double> probe = probeFut.first();
    final CompletionStage<List<Double>> fut = probeFut.second();
    probe.sendNext(1.0);
    final List<Double> expanded = fut.toCompletableFuture().get(1, TimeUnit.SECONDS);
    assertEquals(expanded.size(), 10);
    assertEquals(expanded.stream().mapToDouble(d -> d).sum(), 10, 0.1);
  }

  @Test
  public void expandShouldTrackDrift() throws Exception {
    @SuppressWarnings("unused")
    //#expand-drift
	final Flow<Double, Pair<Double, Integer>, NotUsed> driftFlow = Flow.of(Double.class)
      .expand(d -> Stream.iterate(0, i -> i + 1).map(i -> new Pair<>(d, i)).iterator());
    //#expand-drift
    final TestLatch latch = new TestLatch(2, system);
    final Flow<Double, Pair<Double, Integer>, NotUsed> realDriftFlow = Flow.of(Double.class)
    	      .expand(d -> { latch.countDown(); return Stream.iterate(0, i -> i + 1).map(i -> new Pair<>(d, i)).iterator(); });

    final Pair<TestPublisher.Probe<Double>, TestSubscriber.Probe<Pair<Double, Integer>>> pubSub = TestSource.<Double> probe(system)
      .via(realDriftFlow)
      .toMat(TestSink.<Pair<Double, Integer>> probe(system), Keep.both())
      .run(mat);

    final TestPublisher.Probe<Double> pub = pubSub.first();
    final TestSubscriber.Probe<Pair<Double, Integer>> sub = pubSub.second();

    sub.request(1);
    pub.sendNext(1.0);
    sub.expectNext(new Pair<>(1.0, 0));

    sub.requestNext(new Pair<>(1.0, 1));
    sub.requestNext(new Pair<>(1.0, 2));

    pub.sendNext(2.0);
    Await.ready(latch, Duration.create(1, TimeUnit.SECONDS));
    sub.requestNext(new Pair<>(2.0, 0));
  }

}