/*
 * 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.proton.plug.test.util;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

import org.junit.Assert;
import org.junit.Test;
import org.proton.plug.util.CreditsSemaphore;

public class CreditsSemaphoreTest {

   final CreditsSemaphore semaphore = new CreditsSemaphore(10);

   final AtomicInteger errors = new AtomicInteger(0);

   final AtomicInteger acquired = new AtomicInteger(0);

   final CountDownLatch waiting = new CountDownLatch(1);

   Thread thread = new Thread() {
      public void run() {
         try {
            for (int i = 0; i < 12; i++) {
               if (!semaphore.tryAcquire()) {
                  waiting.countDown();
                  semaphore.acquire();
               }
               acquired.incrementAndGet();
            }
         }
         catch (Throwable e) {
            e.printStackTrace();
            errors.incrementAndGet();
         }
      }
   };

   @Test
   public void testSetAndRelease() throws Exception {
      thread.start();

      // 5 seconds would be an eternity here
      Assert.assertTrue(waiting.await(5, TimeUnit.SECONDS));

      Assert.assertEquals(0, semaphore.getCredits());

      long timeout = System.currentTimeMillis() + 1000;
      while (!semaphore.hasQueuedThreads() && System.currentTimeMillis() < timeout) {
         Thread.sleep(10);
      }

      Assert.assertTrue(semaphore.hasQueuedThreads());

      semaphore.setCredits(2);

      thread.join();

      Assert.assertEquals(12, acquired.get());

      Assert.assertFalse(semaphore.hasQueuedThreads());
   }

   @Test
   public void testDownAndUp() throws Exception {
      thread.start();

      // 5 seconds would be an eternity here
      Assert.assertTrue(waiting.await(5, TimeUnit.SECONDS));

      Assert.assertEquals(0, semaphore.getCredits());

      long timeout = System.currentTimeMillis() + 1000;
      while (!semaphore.hasQueuedThreads() && System.currentTimeMillis() < timeout) {
         Thread.sleep(10);
      }

      Assert.assertTrue(semaphore.hasQueuedThreads());

      semaphore.release(2);

      thread.join();

      Assert.assertEquals(12, acquired.get());

      Assert.assertFalse(semaphore.hasQueuedThreads());
   }

   @Test
   public void testStartedZeroedSetLater() throws Exception {
      semaphore.setCredits(0);

      thread.start();

      // 5 seconds would be an eternity here
      Assert.assertTrue(waiting.await(5, TimeUnit.SECONDS));

      Assert.assertEquals(0, semaphore.getCredits());

      long timeout = System.currentTimeMillis() + 1000;
      while (!semaphore.hasQueuedThreads() && System.currentTimeMillis() < timeout) {
         Thread.sleep(10);
      }

      Assert.assertTrue(semaphore.hasQueuedThreads());

      Assert.assertEquals(0, acquired.get());

      semaphore.setCredits(12);

      thread.join();

      Assert.assertEquals(12, acquired.get());

      Assert.assertFalse(semaphore.hasQueuedThreads());
   }

}
