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/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * Licensed 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. See accompanying
 * LICENSE file.
 */
package com.gemstone.gemfire.internal;

import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

import junit.framework.TestCase;

/**
 * @author dsmith
 *
 */
@SuppressWarnings("synthetic-access")
public class OneTaskOnlyDecoratorJUnitTest extends TestCase {
  
  /**
   * Test to make sure we only execute the task once
   * no matter how many times we schedule it. 
   */
  public void testExecuteOnlyOnce() throws InterruptedException {
    ScheduledExecutorService ex = Executors.newScheduledThreadPool(1);
   
    MyConflationListener listener = new MyConflationListener();
    OneTaskOnlyExecutor decorator = new OneTaskOnlyExecutor(ex, listener);
    
    final CountDownLatch latch = new CountDownLatch(1);
    ex.submit(new Callable() {

      public Object call() throws Exception {
        latch.await();
        return null;
      }
    });
    
    final AtomicInteger counter = new AtomicInteger();
    
    Runnable increment = new Runnable() {

      public void run() {
        counter.incrementAndGet();
      }
    };
    
    for(int i = 0; i < 50; i++) {
      decorator.schedule(increment, 0, TimeUnit.SECONDS);
    }
    
    assertEquals(0, counter.get());
    latch.countDown();
    ex.shutdown();
    ex.awaitTermination(60, TimeUnit.SECONDS);
    assertEquals(1, counter.get());
    assertEquals(49, listener.getDropCount());
  }
  
  /**
   * Test to make sure we reschedule the task for execution 
   * if it has already in progress.
   */
  public void testReschedule() throws InterruptedException {
    ScheduledExecutorService ex = Executors.newScheduledThreadPool(1);
    OneTaskOnlyExecutor decorator = new OneTaskOnlyExecutor(ex);
    
    final CountDownLatch taskRunning = new CountDownLatch(1);
    final CountDownLatch continueTask = new CountDownLatch(1);
    final AtomicInteger counter = new AtomicInteger();
    
    Callable waitForLatch = new Callable() {

      public Object call() throws Exception {
        taskRunning.countDown();
        continueTask.await();
        counter.incrementAndGet();
        return null;
      }
    };
    
    Runnable increment = new Runnable() {

      public void run() {
        counter.incrementAndGet();
      }
    };
    
    decorator.schedule(waitForLatch, 0, TimeUnit.SECONDS);
    taskRunning.await();
    decorator.schedule(increment, 0, TimeUnit.SECONDS);
    
    assertEquals(0, counter.get());
    continueTask.countDown();
    
    ex.shutdown();
    ex.awaitTermination(60, TimeUnit.SECONDS);
    assertEquals(2, counter.get());
  }
  
  /**
   * Test to make sure we reschedule the task for execution 
   * if the new requested execution is earlier than the previous one
   */
  public void testRescheduleForEarlierTime() throws InterruptedException {
    ScheduledExecutorService ex = Executors.newScheduledThreadPool(1);
    MyConflationListener listener = new MyConflationListener();
    OneTaskOnlyExecutor decorator = new OneTaskOnlyExecutor(ex, listener);
    
    final CountDownLatch latch = new CountDownLatch(1);
    final AtomicInteger counter = new AtomicInteger();
    
    Runnable increment = new Runnable() {

      public void run() {
        counter.incrementAndGet();
      }
    };
    
    decorator.schedule(increment, 120, TimeUnit.SECONDS);
    decorator.schedule(increment, 10, TimeUnit.MILLISECONDS);
    
    long start = System.nanoTime();
    
    ex.shutdown();
    ex.awaitTermination(60, TimeUnit.SECONDS);
    long elapsed = System.nanoTime() - start;
    assertEquals(1, counter.get());
    assertEquals(1, listener.getDropCount());
    assertTrue(elapsed < TimeUnit.SECONDS.toNanos(120));
  }


  private static class MyConflationListener extends OneTaskOnlyExecutor.ConflatedTaskListenerAdapter {
    private int dropCount;

    public void taskDropped() {
      dropCount++;
    }
    
    public int getDropCount() {
      return dropCount;
    }
  }
}