/*
    * Copyright (C) 2009 The Guava Authors
    *
    * 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.
   */
  
  package com.google.common.util.concurrent;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static junit.framework.Assert.assertEquals;
  import static junit.framework.Assert.assertFalse;
  import static junit.framework.Assert.assertTrue;
  import static junit.framework.Assert.fail;
  
  import java.util.concurrent.CancellationException;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.TimeUnit;
  
  import javax.annotation.Nullable;
  
  /**
   * Used to test listenable future implementations.
   *
   * @author Sven Mawson
   */
  public class ListenableFutureTester {
  
    private final ExecutorService exec;
    private final ListenableFuture<?> future;
    private final CountDownLatch latch;
  
    public ListenableFutureTester(ListenableFuture<?> future) {
      this.exec = Executors.newCachedThreadPool();
      this.future = checkNotNull(future);
      this.latch = new CountDownLatch(1);
    }
  
    public void setUp() {
      future.addListener(new Runnable() {
        @Override public void run() {
          latch.countDown();
        }
      }, exec);
  
      assertEquals(1, latch.getCount());
      assertFalse(future.isDone());
      assertFalse(future.isCancelled());
    }
  
    public void tearDown() {
      exec.shutdown();
    }
  
    public void testCompletedFuture(@Nullable Object expectedValue)
        throws InterruptedException, ExecutionException {
      assertTrue(future.isDone());
      assertFalse(future.isCancelled());
  
      assertTrue(latch.await(5, TimeUnit.SECONDS));
      assertTrue(future.isDone());
      assertFalse(future.isCancelled());
  
      assertEquals(expectedValue, future.get());
    }
  
    public void testCancelledFuture()
        throws InterruptedException, ExecutionException {
      assertTrue(future.isDone());
      assertTrue(future.isCancelled());
  
      assertTrue(latch.await(5, TimeUnit.SECONDS));
      assertTrue(future.isDone());
      assertTrue(future.isCancelled());
  
      try {
        future.get();
        fail("Future should throw CancellationException on cancel.");
      } catch (CancellationException expected) {}
    }
  
    public void testFailedFuture(@Nullable String message)
        throws InterruptedException {
      assertTrue(future.isDone());
      assertFalse(future.isCancelled());
  
      assertTrue(latch.await(5, TimeUnit.SECONDS));
     assertTrue(future.isDone());
     assertFalse(future.isCancelled());
 
     try {
       future.get();
       fail("Future should rethrow the exception.");
     } catch (ExecutionException e) {
       assertEquals(message, e.getCause().getMessage());
     }
   }
 }