/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 org.apache.flink.runtime.iterative.concurrent;

import com.google.common.collect.Lists;
import org.junit.Test;

import org.apache.flink.util.Preconditions;

import java.util.Collections;
import java.util.List;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

import static org.junit.Assert.assertEquals;

public class BrokerTest {

	@Test
	public void mediation() throws Exception {
		Random random = new Random();
		for (int n = 0; n < 20; n++) {
			mediate(random.nextInt(10) + 1);
		}
	}

	void mediate(int subtasks) throws InterruptedException, ExecutionException {

		final ExecutorService executorService = Executors.newFixedThreadPool(subtasks * 2);

		try {
			List<Callable<StringPair>> tasks = Lists.newArrayList();
			Broker<String> broker = new Broker<String>();

			for (int subtask = 0; subtask < subtasks; subtask++) {
				tasks.add(new IterationHead(broker, subtask, "value" + subtask));
				tasks.add(new IterationTail(broker, subtask));
			}

			Collections.shuffle(tasks);

			int numSuccessfulHandovers = 0;
			for (Future<StringPair> future : executorService.invokeAll(tasks)) {
				StringPair stringPair = future.get();
				if (stringPair != null) {
					assertEquals("value" + stringPair.getFirst(), stringPair.getSecond());
					numSuccessfulHandovers++;
				}
			}

			assertEquals(subtasks, numSuccessfulHandovers);
		}
		finally {
			executorService.shutdownNow();
		}
	}

	class IterationHead implements Callable<StringPair> {

		private final Random random;

		private final Broker<String> broker;

		private final String key;

		private final String value;

		IterationHead(Broker<String> broker, Integer key, String value) {
			this.broker = broker;
			this.key = String.valueOf(key);
			this.value = value;
			random = new Random();
		}

		@Override
		public StringPair call() throws Exception {
			Thread.sleep(random.nextInt(10));
			// System.out.println("Head " + key + " hands in " + value);
			broker.handIn(key, value);
			Thread.sleep(random.nextInt(10));
			return null;
		}

	}

	class IterationTail implements Callable<StringPair> {

		private final Random random;

		private final Broker<String> broker;

		private final String key;

		IterationTail(Broker<String> broker, Integer key) {
			this.broker = broker;
			this.key = String.valueOf(key);
			random = new Random();
		}

		@Override
		public StringPair call() throws Exception {

			Thread.sleep(random.nextInt(10));
//			System.out.println("Tail " + key + " asks for handover");
			String value = broker.getAndRemove(key);

//			System.out.println("Tail " + key + " received " + value);
			Preconditions.checkNotNull(value);

			return new StringPair(key, value);
		}
	}

}