/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.util.concurrent;

import io.netty.util.NettyRuntime;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;

@RunWith(Parameterized.class)
public class NonStickyEventExecutorGroupTest {

    private final int maxTaskExecutePerRun;

    @Test(expected = IllegalArgumentException.class)
    public void testInvalidGroup() {
        EventExecutorGroup group = new DefaultEventExecutorGroup(1);
        try {
            new NonStickyEventExecutorGroup(group);
        } finally {
            group.shutdownGracefully();
        }
    }

    @Parameterized.Parameters(name = "{index}: maxTaskExecutePerRun = {0}")
    public static Collection<Object[]> data() throws Exception {
        List<Object[]> params = new ArrayList<>();
        params.add(new Object[] {64});
        params.add(new Object[] {256});
        params.add(new Object[] {1024});
        params.add(new Object[] {Integer.MAX_VALUE});
        return params;
    }

    public NonStickyEventExecutorGroupTest(int maxTaskExecutePerRun) {
        this.maxTaskExecutePerRun = maxTaskExecutePerRun;
    }

    @Test(timeout = 10000)
    public void testOrdering() throws Throwable {
        final int threads = NettyRuntime.availableProcessors() * 2;
        final EventExecutorGroup group = new UnorderedThreadPoolEventExecutor(threads);
        final NonStickyEventExecutorGroup nonStickyGroup = new NonStickyEventExecutorGroup(group, maxTaskExecutePerRun);
        try {
            final CountDownLatch startLatch = new CountDownLatch(1);
            final AtomicReference<Throwable> error = new AtomicReference<>();
            List<Thread> threadList = new ArrayList<>(threads);
            for (int i = 0 ; i < threads; i++) {
                Thread thread = new Thread(() -> {
                    try {
                        execute(nonStickyGroup, startLatch);
                    } catch (Throwable cause) {
                        error.compareAndSet(null, cause);
                    }
                });
                threadList.add(thread);
                thread.start();
            }
            startLatch.countDown();
            for (Thread t: threadList) {
                t.join();
            }
            Throwable cause = error.get();
            if (cause != null) {
                throw cause;
            }
        } finally {
            nonStickyGroup.shutdownGracefully();
        }
    }

    @Test
    public void testRaceCondition() throws InterruptedException {
        EventExecutorGroup group = new UnorderedThreadPoolEventExecutor(1);
        NonStickyEventExecutorGroup nonStickyGroup = new NonStickyEventExecutorGroup(group, maxTaskExecutePerRun);

        try {
            EventExecutor executor = nonStickyGroup.next();

            for (int j = 0; j < 5000; j++) {
                final CountDownLatch firstCompleted = new CountDownLatch(1);
                final CountDownLatch latch = new CountDownLatch(2);
                for (int i = 0; i < 2; i++) {
                    executor.execute(() -> {
                        firstCompleted.countDown();
                        latch.countDown();
                    });
                    Assert.assertTrue(firstCompleted.await(1, TimeUnit.SECONDS));
                }

                Assert.assertTrue(latch.await(5, TimeUnit.SECONDS));
            }
        } finally {
            nonStickyGroup.shutdownGracefully();
        }
    }

    private static void execute(EventExecutorGroup group, CountDownLatch startLatch) throws Throwable {
        EventExecutor executor = group.next();
        Assert.assertTrue(executor instanceof OrderedEventExecutor);
        final AtomicReference<Throwable> cause = new AtomicReference<>();
        final AtomicInteger last = new AtomicInteger();
        int tasks = 10000;
        List<Future<?>> futures = new ArrayList<>(tasks);
        final CountDownLatch latch = new CountDownLatch(tasks);
        startLatch.await();

        for (int i = 1 ; i <= tasks; i++) {
            final int id = i;
            futures.add(executor.submit(() -> {
                try {
                    if (cause.get() == null) {
                        int lastId = last.get();
                        if (lastId >= id) {
                            cause.compareAndSet(null, new AssertionError(
                                    "Out of order execution id(" + id + ") >= lastId(" + lastId + ')'));
                        }
                        if (!last.compareAndSet(lastId, id)) {
                            cause.compareAndSet(null, new AssertionError("Concurrent execution of tasks"));
                        }
                    }
                } finally {
                    latch.countDown();
                }
            }));
        }
        latch.await();
        for (Future<?> future: futures) {
            future.syncUninterruptibly();
        }
        Throwable error = cause.get();
        if (error != null) {
            throw error;
        }
    }
}
