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import java.nio.ByteBuffer;

import java.util.List;

import java.util.concurrent.CompletionStage;

import java.util.concurrent.CountDownLatch;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.Flow.Subscription;

import java.util.concurrent.SubmissionPublisher;

import java.util.function.IntSupplier;

import java.util.stream.IntStream;

import jdk.incubator.http.HttpResponse.BodySubscriber;

import org.testng.annotations.DataProvider;

import org.testng.annotations.Test;

import static java.lang.Long.MAX_VALUE;

import static java.lang.System.out;

import static java.nio.ByteBuffer.wrap;

import static java.util.concurrent.TimeUnit.SECONDS;

import static jdk.incubator.http.HttpResponse.BodySubscriber.buffering;

import static org.testng.Assert.*;

/*

 * @test

 * @summary Direct test for HttpResponse.BodySubscriber.buffering() cancellation

 * @run testng/othervm BufferingSubscriberCancelTest

 */

public class BufferingSubscriberCancelTest {

    @DataProvider(name = "bufferSizes")

    public Object[][] bufferSizes() {

        return new Object[][]{

            // bufferSize should be irrelevant

            {1}, {100}, {511}, {512}, {513}, {1024}, {2047}, {2048}

        };

    }

    @Test(dataProvider = "bufferSizes")

    public void cancelWithoutAnyItemsPublished(int bufferSize) throws Exception {

        ExecutorService executor = Executors.newFixedThreadPool(1);

        SubmissionPublisher<List<ByteBuffer>> publisher =

                new SubmissionPublisher<>(executor, 1);

        CountDownLatch gate = new CountDownLatch(1);  // single onSubscribe

        ExposingSubscriber exposingSubscriber = new ExposingSubscriber(gate);

        BodySubscriber subscriber = buffering(exposingSubscriber, bufferSize);

        publisher.subscribe(subscriber);

        gate.await(30, SECONDS);

        assertEqualsWithRetry(publisher::getNumberOfSubscribers, 1);

        exposingSubscriber.subscription.cancel();

        assertEqualsWithRetry(publisher::getNumberOfSubscribers, 0);

        // further cancels/requests should be a no-op

        Subscription s = exposingSubscriber.subscription;

        s.cancel(); s.request(1);

        s.cancel(); s.request(100); s.cancel();

        s.cancel(); s.request(MAX_VALUE); s.cancel(); s.cancel();

        s.cancel(); s.cancel(); s.cancel(); s.cancel();

        s.request(MAX_VALUE); s.request(MAX_VALUE); s.request(MAX_VALUE);

        assertEqualsWithRetry(publisher::getNumberOfSubscribers, 0);

    }

    @DataProvider(name = "sizeAndItems")

    public Object[][] sizeAndItems() {

        return new Object[][] {

            // bufferSize and item bytes must be equal to count onNext calls

            // bufferSize        items

            { 1,   List.of(wrap(new byte[] { 1 }))                             },

            { 2,   List.of(wrap(new byte[] { 1, 2 }))                          },

            { 3,   List.of(wrap(new byte[] { 1, 2, 3}))                        },

            { 4,   List.of(wrap(new byte[] { 1, 2 , 3, 4}))                    },

            { 5,   List.of(wrap(new byte[] { 1, 2 , 3, 4, 5}))                 },

            { 6,   List.of(wrap(new byte[] { 1, 2 , 3, 4, 5, 6}))              },

            { 7,   List.of(wrap(new byte[] { 1, 2 , 3, 4, 5, 6, 7}))           },

            { 8,   List.of(wrap(new byte[] { 1, 2 , 3, 4, 5, 6, 7, 8}))        },

            { 9,   List.of(wrap(new byte[] { 1, 2 , 3, 4, 5, 6, 7, 8, 9}))     },

            { 10,  List.of(wrap(new byte[] { 1, 2 , 3, 4, 5, 6, 7, 8, 9, 10})) },

        };

    }

    @Test(dataProvider = "sizeAndItems")

    public void cancelWithItemsPublished(int bufferSize, List<ByteBuffer> items)

        throws Exception

    {

        ExecutorService executor = Executors.newFixedThreadPool(1);

        SubmissionPublisher<List<ByteBuffer>> publisher =

                new SubmissionPublisher<>(executor, 24);

        final int ITERATION_TIMES = 10;

        // onSubscribe + onNext ITERATION_TIMES

        CountDownLatch gate = new CountDownLatch(1 + ITERATION_TIMES);

        ExposingSubscriber exposingSubscriber = new ExposingSubscriber(gate);

        BodySubscriber subscriber = buffering(exposingSubscriber, bufferSize);

        publisher.subscribe(subscriber);

        assertEqualsWithRetry(publisher::getNumberOfSubscribers, 1);

        IntStream.range(0, ITERATION_TIMES).forEach(x -> publisher.submit(items));

        gate.await(30, SECONDS);

        exposingSubscriber.subscription.cancel();

        IntStream.range(0, ITERATION_TIMES+1).forEach(x -> publisher.submit(items));

        assertEqualsWithRetry(publisher::getNumberOfSubscribers, 0);

        assertEquals(exposingSubscriber.onNextInvocations, ITERATION_TIMES);

    }

    // same as above but with more racy conditions, do not wait on the gate

    @Test(dataProvider = "sizeAndItems")

    public void cancelWithItemsPublishedNoWait(int bufferSize, List<ByteBuffer> items)

        throws Exception

    {

        ExecutorService executor = Executors.newFixedThreadPool(1);

        SubmissionPublisher<List<ByteBuffer>> publisher =

                new SubmissionPublisher<>(executor, 24);

        final int ITERATION_TIMES = 10;

        // any callback will so, since onSub is guaranteed to be before onNext

        CountDownLatch gate = new CountDownLatch(1);

        ExposingSubscriber exposingSubscriber = new ExposingSubscriber(gate);

        BodySubscriber subscriber = buffering(exposingSubscriber, bufferSize);

        publisher.subscribe(subscriber);

        IntStream.range(0, ITERATION_TIMES).forEach(x -> publisher.submit(items));

        gate.await(30, SECONDS);

        exposingSubscriber.subscription.cancel();

        IntStream.range(0, ITERATION_TIMES+1).forEach(x -> publisher.submit(items));

        int onNextInvocations = exposingSubscriber.onNextInvocations;

        assertTrue(onNextInvocations <= ITERATION_TIMES,

                   "Expected <= " + ITERATION_TIMES + ", got " + onNextInvocations);

    }

    static class ExposingSubscriber implements BodySubscriber<Void> {

        final CountDownLatch gate;

        volatile Subscription subscription;

        volatile int onNextInvocations;

        ExposingSubscriber(CountDownLatch gate) {

            this.gate = gate;

        }

        @Override

        public void onSubscribe(Subscription subscription) {

            //out.println("onSubscribe " + subscription);

            this.subscription = subscription;

            gate.countDown();

            subscription.request(MAX_VALUE); // forever

        }

        @Override

        public void onNext(List<ByteBuffer> item) {

            //out.println("onNext " + item);

            onNextInvocations++;

            gate.countDown();

        }

        @Override

        public void onError(Throwable throwable) {

            out.println("onError " + throwable);

        }

        @Override

        public void onComplete() {

            out.println("onComplete ");

        }

        @Override

        public CompletionStage<Void> getBody() {

            throw new UnsupportedOperationException("getBody is unsupported");

        }

    }

    // There is a race between cancellation and subscriber callbacks, the

    // following mechanism retries a number of times to allow for this race. The

    // only requirement is that the expected result is actually observed.

    static final int TEST_RECHECK_TIMES = 30;

    static void assertEqualsWithRetry(IntSupplier actualSupplier, int expected)

        throws Exception

    {

        int actual = expected + 1; // anything other than expected

        for (int i=0; i< TEST_RECHECK_TIMES; i++) {

            actual = actualSupplier.getAsInt();

            if (actual == expected)

                return;

            Thread.sleep(100);

        }

        assertEquals(actual, expected); // will fail with the usual testng message

    }

}