import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;
import java.util.stream.Collectors;

public class FutureTest {
    private static CompletableFuture<List<String>> getCompletableFutureResult() {
        return CompletableFuture.supplyAsync(() -> {
            try {
                TimeUnit.MILLISECONDS.sleep(2500);
                System.out.println("It async task that wait 2500 ms");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return getResult();
        });
    }

    private static ArrayList<String> getResult() {
        ArrayList<String> list = new ArrayList<>();
        list.add("one");
        list.add("two");
        return list;
    }

    private static CompletableFuture<List<List<String>>> testFutures() {
        int x = 3;
        List<CompletableFuture<List<String>>> futureList = new ArrayList<>();
        for (int i = 0; i < x; i++) {
            futureList.add(getCompletableFutureResult());
        }

        CompletableFuture[] futureArray = futureList.toArray(new CompletableFuture[0]);
        CompletableFuture<Void> combinedFuture = CompletableFuture.allOf(futureArray);

        return combinedFuture.thenApply(it ->
                futureList.stream().map(CompletableFuture::join).collect(Collectors.toList())
        );
    }

    public static void main(String[] args) {
        long startTime = System.currentTimeMillis();
        System.out.println("Main: " + Thread.currentThread().getName());
        int requestCount = 10;
        CountDownLatch countDownLatch = new CountDownLatch(requestCount);

        ExecutorService executorService = Executors.newFixedThreadPool(1);
        ForkJoinPool forkJoinPool = new ForkJoinPool(8);

        for (int i = 0; i < requestCount; i++) {
            executorService.execute(() -> {
                CompletableFuture.runAsync(() -> {
                    System.out.println("AsyncThreadStart: " + Thread.currentThread().getName());
                    testFutures().thenAccept(System.out::println).join();
                }, forkJoinPool).whenComplete((task, ex) -> {
                    if (ex != null) System.out.println(ex.getMessage());
                    countDownLatch.countDown();
                    if (countDownLatch.getCount() == 0) {
                        long endTime = System.currentTimeMillis();
                        System.out.println(endTime - startTime);
                        executorService.shutdown();
                    }
                });
            });
        }

        System.out.println("Execution not locking");
    }
}