package example;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import org.junit.Test;

public class CompletableFutures {
  @Test
  public void chainFuturesInner() throws ExecutionException, InterruptedException {
    System.out.println("Executing chainFuturesInner()");
    final Integer result = future(1)
        .thenCompose(ignored1 -> future(2)
            .thenCompose(ignored2 -> future(3)))
        .get();

    System.out.println("The result is " + result);
    System.out.println();
  }

  @Test
  public void chainFuturesOuter() throws ExecutionException, InterruptedException {
    System.out.println("Executing chainFuturesOuter()");
    final Integer result = future(1)
        .thenCompose(ignored1 -> future(2))
        .thenCompose(ignored2 -> future(3))
        .get();

    System.out.println("The result is " + result);
    System.out.println();
  }

  public static CompletableFuture<Integer> future(int id) {
    return CompletableFuture.supplyAsync(() -> {
      try {
        Thread.sleep(500);

      } catch (InterruptedException e) {
        throw new RuntimeException(e);
      }

      System.out.println("Future " + id + " executed");

      return id;
    });
  }
}