/* Copyright (2005-2007) Schibsted Søk AS

  * This file is part of SESAT.

  *

  *   SESAT is free software: you can redistribute it and/or modify

  *   it under the terms of the GNU Affero General Public License as published by

  *   the Free Software Foundation, either version 3 of the License, or

  *   (at your option) any later version.

  *

  *   SESAT is distributed in the hope that it will be useful,

  *   but WITHOUT ANY WARRANTY; without even the implied warranty of

  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  *   GNU Affero General Public License for more details.

  *

  *   You should have received a copy of the GNU Affero General Public License

  *   along with SESAT.  If not, see <http://www.gnu.org/licenses/>.

  *

  * Created on May 11, 2007, 8:16:37 PM

  */

 package no.sesat.search.view.velocity;

 import org.apache.velocity.app.Velocity;

 import org.apache.velocity.runtime.RuntimeConstants;

 import org.apache.velocity.runtime.RuntimeServices;

 import org.apache.velocity.runtime.resource.Resource;

 import org.apache.velocity.runtime.resource.ResourceCache;

 import java.util.HashMap;

 import java.util.Iterator;

 import java.util.Map;

 import java.util.concurrent.locks.ReadWriteLock;

 import java.util.concurrent.locks.ReentrantReadWriteLock;

 /**

  * A faster implementation of the resource cache than the default. The default implementation uses a fully synchronized

  * LRUMap.

  * <p> This implementation only supports an unbounded cache size and will throw <tt>IllegalArgumentException</tt> if

  * {@link org.apache.velocity.app.Velocity} is set to anything other than zero.

  *

  * @see org.apache.velocity.runtime.resource.ResourceCacheImpl

  *

  *

  */

 public final class QuickResourceCacheImpl implements ResourceCache {

     /** Property name for controlling the initial size of the cache. */

     public static final String INITIAL_SIZE_PROPERTY = "resource.manager.quickcache.size";

     private Map<Object, Resource> cache;

     private final ReadWriteLock lock = new ReentrantReadWriteLock();

     private static final String BOUNDED_CACHE_NOT_SUPPORTED =

             "This implementatation only supports an unbounded cache. Change impl using property ";

     /**

      * {@inheritDoc}

      */

     public void initialize(final RuntimeServices svc) {

         if (svc.getInt(RuntimeConstants.RESOURCE_MANAGER_DEFAULTCACHE_SIZE, 0) != 0) {

             throw new IllegalArgumentException(BOUNDED_CACHE_NOT_SUPPORTED + Velocity.RESOURCE_MANAGER_CLASS);

         }

         // Writes are rare once SESAT has inititalized a site so a HashMap should be faster than a ConcurrentHashMap.

         cache = new HashMap<Object, Resource>(svc.getInt(INITIAL_SIZE_PROPERTY, 100));

     }

     /**

      * {@inheritDoc}

      */

     public Resource get(final Object o) {

         try {

             lock.readLock().lock();

             return cache.get(o);

         } finally {

             lock.readLock().unlock();

         }

     }

     /**

      * {@inheritDoc}

      */

     public Resource put(final Object o, final Resource resource) {

         try {

             lock.writeLock().lock();

             return cache.put(o, resource);

         } finally {

             lock.writeLock().unlock();

         }

     }

     /**

      * {@inheritDoc}

      */

     public Resource remove(final Object o) {

         try {

             lock.writeLock().lock();

             return cache.remove(o);

         } finally {

             lock.writeLock().unlock();

         }

     }

     /**

      * {@inheritDoc}

      */

     public Iterator enumerateKeys() {

         try {

             lock.readLock().lock();

             return cache.keySet().iterator();

         } finally {

             lock.readLock().unlock();

         }

     }

 }