/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.event.internal;

import java.io.Serializable;

import org.hibernate.HibernateException;
import org.hibernate.collection.spi.PersistentCollection;
import org.hibernate.event.spi.EventSource;
import org.hibernate.persister.collection.CollectionPersister;
import org.hibernate.type.CollectionType;

When an entity is passed to update(), we must inspect all its collections and
1. associate any uninitialized PersistentCollections with this session
2. associate any initialized PersistentCollections with this session, using the
   existing snapshot
3. execute a collection removal (SQL DELETE) for each null collection property
   or "new" collection
Author:
Gavin King/**
 * When an entity is passed to update(), we must inspect all its collections and
 * 1. associate any uninitialized PersistentCollections with this session
 * 2. associate any initialized PersistentCollections with this session, using the
 *    existing snapshot
 * 3. execute a collection removal (SQL DELETE) for each null collection property
 *    or "new" collection
 *
 * @author Gavin King
 */
public class OnUpdateVisitor extends ReattachVisitor {

	OnUpdateVisitor(EventSource session, Serializable key, Object owner) {
		super( session, key, owner );
	}

	@Override
	Object processCollection(Object collection, CollectionType type) throws HibernateException {

		if ( collection == CollectionType.UNFETCHED_COLLECTION ) {
			return null;
		}

		EventSource session = getSession();
		CollectionPersister persister = session.getFactory().getCollectionPersister( type.getRole() );

		final Serializable collectionKey = extractCollectionKeyFromOwner( persister );
		if ( collection!=null && (collection instanceof PersistentCollection) ) {
			PersistentCollection wrapper = (PersistentCollection) collection;
			if ( wrapper.setCurrentSession(session) ) {
				//a "detached" collection!
				if ( !isOwnerUnchanged( wrapper, persister, collectionKey ) ) {
					// if the collection belonged to a different entity,
					// clean up the existing state of the collection
					removeCollection( persister, collectionKey, session );
				}
				reattachCollection(wrapper, type);
			}
			else {
				// a collection loaded in the current session
				// can not possibly be the collection belonging
				// to the entity passed to update()
				removeCollection(persister, collectionKey, session);
			}
		}
		else {
			// null or brand new collection
			// this will also (inefficiently) handle arrays, which have
			// no snapshot, so we can't do any better
			removeCollection(persister, collectionKey, session);
		}

		return null;
	}

}