/*
    * Copyright 2012-2013 smartics, Kronseder & Reiner GmbH
    *
    * 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 de.smartics.properties.spi.config.cache.guava;
  
  import java.util.Set;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantReadWriteLock;
  
  import com.google.common.cache.Cache;
  
  /**
   * Guava-Loading-Cache implementation of a cache.
   *
   * @param <K> type of the key.
   * @param <V> type of the value.
   */
  public final class GuavaDelegatingCache<K, V> implements
      de.smartics.properties.spi.config.cache.Cache<K, V>
  {
  
    // ********************************* Fields *********************************
  
    /**
     * The lock for synchronized access.
     *
     * @serial
     */
    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
  
    /**
     * The read lock for synchronized access.
     *
     * @serial
     */
    private final Lock readLock = lock.readLock();
  
    /**
     * The write lock for synchronized access.
     *
     * @serial
     */
    private final Lock writeLock = lock.writeLock();
  
    /**
     * They cache being used.
     */
    private final Cache<K, V> cache;
  
    // --- constants ------------------------------------------------------------
  
    // --- members --------------------------------------------------------------
  
    // ****************************** Initializer *******************************
  
    // ****************************** Constructors ******************************
  
    /**
     * Constructor.
     *
     * @param cache the cache to delegate to.
     */
    public GuavaDelegatingCache(final Cache<K, V> cache)
    {
      this.cache = cache;
    }
  
    // ****************************** Inner Classes *****************************
  
    // ********************************* Methods ********************************
  
    // --- init -----------------------------------------------------------------
  
    // --- get&set --------------------------------------------------------------
  
    // --- business -------------------------------------------------------------
  
    @Override
    public long size()
    {
      readLock.lock();
      try
      {
        return cache.size();
      }
      finally
     {
       readLock.unlock();
     }
   }
 
   @Override
   public V get(final K key)
   {
     readLock.lock();
     try
     {
       return cache.getIfPresent(key);
     }
     finally
     {
       readLock.unlock();
     }
   }
 
   @Override
   public void put(final K key, final V value)
   {
     writeLock.lock();
     try
     {
       cache.put(key, value);
     }
     finally
     {
       writeLock.unlock();
     }
   }
 
   @Override
   public void put(final K key, final V value, final long updateIntervalInMs,
       final TimeUnit milliseconds)
   {
     writeLock.lock();
     try
     {
       cache.put(key, value);
     }
     finally
     {
       writeLock.unlock();
     }
   }
 
   @Override
   // CHECKSTYLE:OFF
   public void put(final K key, final V value, final int lifespan,
       final TimeUnit lifespanTimeUnit, final int maxIdleTime,
       final TimeUnit maxIdleTimeTimeUnit)
   {
     writeLock.lock();
     try
     {
       cache.put(key, value);
     }
     finally
     {
       writeLock.unlock();
     }
   }
 
   // CHECKSTYLE:ON
 
   @Override
   public V remove(final K key)
   {
     writeLock.lock();
     try
     {
       final V returnValue = cache.getIfPresent(key);
       cache.invalidate(key);
       return returnValue;
     }
     finally
     {
       writeLock.unlock();
     }
   }
 
   @Override
   public Set<K> keySet()
   {
     readLock.lock();
     try
     {
       return cache.asMap().keySet();
     }
     finally
     {
       readLock.unlock();
     }
   }
 
 }