/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Middleware LLC.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 */
package org.hibernate.cache.access;

import org.hibernate.cache.EntityRegion;
import org.hibernate.cache.CacheException;

/**
 * Contract for managing transactional and concurrent access to cached entity
 * data.  The expected call sequences related to various operations are:<ul>
 * <li><b>INSERTS</b> : {@link #insert} -> {@link #afterInsert}</li>
 * <li><b>UPDATES</b> : {@link #lockItem} -> {@link #update} -> {@link #afterUpdate}</li>
 * <li><b>DELETES</b> : {@link #lockItem} -> {@link #remove} -> {@link #unlockItem}</li>
 * </ul>
 * <p/>
 * There is another usage pattern that is used to invalidate entries
 * after performing "bulk" HQL/SQL operations:
 * {@link #lockRegion} -> {@link #removeAll} -> {@link #unlockRegion}
 *
 * @author Gavin King
 * @author Steve Ebersole
 */
public interface EntityRegionAccessStrategy {

	/**
	 * Get the wrapped entity cache region
	 *
	 * @return The underlying region
	 */
	public EntityRegion getRegion();

	/**
	 * Attempt to retrieve an object from the cache. Mainly used in attempting
	 * to resolve entities/collections from the second level cache.
	 *
	 * @param key The key of the item to be retrieved.
	 * @param txTimestamp a timestamp prior to the transaction start time
	 * @return the cached object or <tt>null</tt>
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public Object get(Object key, long txTimestamp) throws CacheException;

	/**
	 * Attempt to cache an object, after loading from the database.
	 *
	 * @param key The item key
	 * @param value The item
	 * @param txTimestamp a timestamp prior to the transaction start time
	 * @param version the item version number
	 * @return <tt>true</tt> if the object was successfully cached
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public boolean putFromLoad(
			Object key,
			Object value,
			long txTimestamp,
			Object version) throws CacheException;

	/**
	 * Attempt to cache an object, after loading from the database, explicitly
	 * specifying the minimalPut behavior.
	 *
	 * @param key The item key
	 * @param value The item
	 * @param txTimestamp a timestamp prior to the transaction start time
	 * @param version the item version number
	 * @param minimalPutOverride Explicit minimalPut flag
	 * @return <tt>true</tt> if the object was successfully cached
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public boolean putFromLoad(
			Object key,
			Object value,
			long txTimestamp,
			Object version,
			boolean minimalPutOverride) throws CacheException;

	/**
	 * We are going to attempt to update/delete the keyed object. This
	 * method is used by "asynchronous" concurrency strategies.
	 * <p/>
	 * The returned object must be passed back to release(), to release the
	 * lock. Concurrency strategies which do not support client-visible
	 * locks may silently return null.
	 *
	 * @param key The key of the item to lock
	 * @param version The item's current version value
	 * @return A representation of our lock on the item; or null.
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public SoftLock lockItem(Object key, Object version) throws CacheException;

	/**
	 * Lock the entire region
	 *
	 * @return A representation of our lock on the item; or null.
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public SoftLock lockRegion() throws CacheException;

	/**
	 * Called when we have finished the attempted update/delete (which may or
	 * may not have been successful), after transaction completion.  This method
	 * is used by "asynchronous" concurrency strategies.
	 *
	 * @param key The item key
	 * @param lock The lock previously obtained from {@link #lockItem}
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public void unlockItem(Object key, SoftLock lock) throws CacheException;

	/**
	 * Called after we have finished the attempted invalidation of the entire
	 * region
	 *
	 * @param lock The lock previously obtained from {@link #lockRegion}
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public void unlockRegion(SoftLock lock) throws CacheException;

	/**
	 * Called after an item has been inserted (before the transaction completes),
	 * instead of calling evict().
	 * This method is used by "synchronous" concurrency strategies.
	 *
	 * @param key The item key
	 * @param value The item
	 * @param version The item's version value
	 * @return Were the contents of the cache actual changed by this operation?
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public boolean insert(Object key, Object value, Object version) throws CacheException;

	/**
	 * Called after an item has been inserted (after the transaction completes),
	 * instead of calling release().
	 * This method is used by "asynchronous" concurrency strategies.
	 *
	 * @param key The item key
	 * @param value The item
	 * @param version The item's version value
	 * @return Were the contents of the cache actual changed by this operation?
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public boolean afterInsert(Object key, Object value, Object version) throws CacheException;

	/**
	 * Called after an item has been updated (before the transaction completes),
	 * instead of calling evict(). This method is used by "synchronous" concurrency
	 * strategies.
	 *
	 * @param key The item key
	 * @param value The item
	 * @param currentVersion The item's current version value
	 * @param previousVersion The item's previous version value
	 * @return Were the contents of the cache actual changed by this operation?
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public boolean update(Object key, Object value, Object currentVersion, Object previousVersion) throws CacheException;

	/**
	 * Called after an item has been updated (after the transaction completes),
	 * instead of calling release().  This method is used by "asynchronous"
	 * concurrency strategies.
	 *
	 * @param key The item key
	 * @param value The item
	 * @param currentVersion The item's current version value
	 * @param previousVersion The item's previous version value
	 * @param lock The lock previously obtained from {@link #lockItem}
	 * @return Were the contents of the cache actual changed by this operation?
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public boolean afterUpdate(Object key, Object value, Object currentVersion, Object previousVersion, SoftLock lock) throws CacheException;

	/**
	 * Called after an item has become stale (before the transaction completes).
	 * This method is used by "synchronous" concurrency strategies.
	 *
	 * @param key The key of the item to remove
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public void remove(Object key) throws CacheException;

	/**
	 * Called to evict data from the entire region
	 *
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public void removeAll() throws CacheException;

	/**
	 * Forcibly evict an item from the cache immediately without regard for transaction
	 * isolation.
	 *
	 * @param key The key of the item to remove
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public void evict(Object key) throws CacheException;

	/**
	 * Forcibly evict all items from the cache immediately without regard for transaction
	 * isolation.
	 *
	 * @throws CacheException Propogated from underlying {@link org.hibernate.cache.Region}
	 */
	public void evictAll() throws CacheException;
}
