//$Id: TransactionalCache.java 9278 2006-02-13 16:57:22Z steveebersole $
package org.hibernate.cache;

import java.util.Comparator;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Support for fully transactional cache implementations like
 * JBoss TreeCache. Note that this might be a less scalable
 * concurrency strategy than <tt>ReadWriteCache</tt>. This is
 * a "synchronous" concurrency strategy.
 *
 * @author Gavin King
 */
public class TransactionalCache implements CacheConcurrencyStrategy {

	private static final Log log = LogFactory.getLog( TransactionalCache.class );

	private Cache cache;

	public String getRegionName() {
		return cache.getRegionName();
	}

	public Object get(Object key, long txTimestamp) throws CacheException {
		if ( log.isDebugEnabled() ) {
			log.debug( "cache lookup: " + key );
		}
		Object result = cache.read( key );
		if ( log.isDebugEnabled() ) {
			log.debug( result == null ? "cache miss" : "cache hit" );
		}
		return result;
	}

	public boolean put(
			Object key,
	        Object value,
	        long txTimestamp,
	        Object version,
	        Comparator versionComparator,
	        boolean minimalPut) throws CacheException {
		if ( minimalPut && cache.read( key ) != null ) {
			if ( log.isDebugEnabled() ) {
				log.debug( "item already cached: " + key );
			}
			return false;
		}
		if ( log.isDebugEnabled() ) {
			log.debug( "caching: " + key );
		}
		if ( cache instanceof OptimisticCache ) {
			( ( OptimisticCache ) cache ).writeLoad( key, value, version );
		}
		else {
			cache.put( key, value );
		}
		return true;
	}

	/**
	 * Do nothing, returning null.
	 */
	public SoftLock lock(Object key, Object version) throws CacheException {
		//noop
		return null;
	}

	/**
	 * Do nothing.
	 */
	public void release(Object key, SoftLock clientLock) throws CacheException {
		//noop
	}

	public boolean update(
			Object key,
	        Object value,
	        Object currentVersion,
	        Object previousVersion) throws CacheException {
		if ( log.isDebugEnabled() ) {
			log.debug( "updating: " + key );
		}
		if ( cache instanceof OptimisticCache ) {
			( ( OptimisticCache ) cache ).writeUpdate( key, value, currentVersion, previousVersion );
		}
		else {
			cache.update( key, value );
		}
		return true;
	}

	public boolean insert(
			Object key,
	        Object value,
	        Object currentVersion) throws CacheException {
		if ( log.isDebugEnabled() ) {
			log.debug( "inserting: " + key );
		}
		if ( cache instanceof OptimisticCache ) {
			( ( OptimisticCache ) cache ).writeInsert( key, value, currentVersion );
		}
		else {
			cache.update( key, value );
		}
		return true;
	}

	public void evict(Object key) throws CacheException {
		cache.remove( key );
	}

	public void remove(Object key) throws CacheException {
		if ( log.isDebugEnabled() ) {
			log.debug( "removing: " + key );
		}
		cache.remove( key );
	}

	public void clear() throws CacheException {
		log.debug( "clearing" );
		cache.clear();
	}

	public void destroy() {
		try {
			cache.destroy();
		}
		catch ( Exception e ) {
			log.warn( "could not destroy cache", e );
		}
	}

	public void setCache(Cache cache) {
		this.cache = cache;
	}

	public Cache getCache() {
		return cache;
	}

	/**
	 * Do nothing.
	 */
	public boolean afterInsert(
			Object key,
	        Object value,
	        Object version) throws CacheException {
		return false;
	}

	/**
	 * Do nothing.
	 */
	public boolean afterUpdate(
			Object key,
	        Object value,
	        Object version,
	        SoftLock clientLock) throws CacheException {
		return false;
	}

	public String toString() {
		return cache + "(transactional)";
	}

}