/*
    * Copyright (C) 2011 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.cache;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.ImmutableMap;
  import com.google.common.collect.Lists;
  import com.google.common.util.concurrent.Futures;
  import com.google.common.util.concurrent.ListenableFuture;
  
  import junit.framework.TestCase;
  
  import java.util.LinkedList;
  import java.util.Map;
  import java.util.concurrent.Executor;
  import java.util.concurrent.atomic.AtomicInteger;
  
  /**
   * Unit tests for {@link CacheLoader}.
   *
   * @author Charles Fry
   */
  public class CacheLoaderTest extends TestCase {
  
    private static class QueuingExecutor implements Executor {
      private LinkedList<Runnable> tasks = Lists.newLinkedList();
  
      @Override
      public void execute(Runnable task) {
        tasks.add(task);
      }
  
      private void runNext() {
        tasks.removeFirst().run();
      }
    }
  
    public void testAsyncReload() throws Exception {
      final AtomicInteger loadCount = new AtomicInteger();
      final AtomicInteger reloadCount = new AtomicInteger();
      final AtomicInteger loadAllCount = new AtomicInteger();
  
      CacheLoader<Object, Object> baseLoader = new CacheLoader<Object, Object>() {
        @Override
        public Object load(Object key) {
          loadCount.incrementAndGet();
          return new Object();
        }
  
        @Override
        public ListenableFuture<Object> reload(Object key, Object oldValue) {
          reloadCount.incrementAndGet();
          return Futures.immediateFuture(new Object());
        }
  
        @Override
        public Map<Object, Object> loadAll(Iterable<? extends Object> keys) {
          loadAllCount.incrementAndGet();
          return ImmutableMap.of();
        }
      };
  
      assertEquals(0, loadCount.get());
      assertEquals(0, reloadCount.get());
      assertEquals(0, loadAllCount.get());
  
      baseLoader.load(new Object());
      baseLoader.reload(new Object(), new Object());
      baseLoader.loadAll(ImmutableList.of(new Object()));
      assertEquals(1, loadCount.get());
      assertEquals(1, reloadCount.get());
      assertEquals(1, loadAllCount.get());
  
      QueuingExecutor executor = new QueuingExecutor();
      CacheLoader<Object, Object> asyncReloader =
          CacheLoader.asyncReloading(baseLoader, executor);
  
      asyncReloader.load(new Object());
      asyncReloader.reload(new Object(), new Object());
      asyncReloader.loadAll(ImmutableList.of(new Object()));
      assertEquals(2, loadCount.get());
      assertEquals(1, reloadCount.get());
      assertEquals(2, loadAllCount.get());
  
      executor.runNext();
     assertEquals(2, loadCount.get());
     assertEquals(2, reloadCount.get());
     assertEquals(2, loadAllCount.get());
   }
 }