//$Id: DefaultAutoFlushEventListener.java 7785 2005-08-08 23:24:44Z oneovthafew $
package org.hibernate.event.def;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.FlushMode;
import org.hibernate.HibernateException;
import org.hibernate.event.AutoFlushEvent;
import org.hibernate.event.AutoFlushEventListener;
import org.hibernate.event.EventSource;

/**
 * Defines the default flush event listeners used by hibernate for 
 * flushing session state in response to generated auto-flush events.
 *
 * @author Steve Ebersole
 */
public class DefaultAutoFlushEventListener extends AbstractFlushingEventListener implements AutoFlushEventListener {

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

    /** Handle the given auto-flush event.
     *
     * @param event The auto-flush event to be handled.
     * @throws HibernateException
     */
	public void onAutoFlush(AutoFlushEvent event) throws HibernateException {

		final EventSource source = event.getSession();
		
		if ( flushMightBeNeeded(source) ) {

			final int oldSize = source.getActionQueue().numberOfCollectionRemovals();

			flushEverythingToExecutions(event);
			
			if ( flushIsReallyNeeded(event, source) ) {

				log.trace("Need to execute flush");

				performExecutions(source);
				postFlush(source);
				// note: performExecutions() clears all collectionXxxxtion 
				// collections (the collection actions) in the session

				if ( source.getFactory().getStatistics().isStatisticsEnabled() ) {
					source.getFactory().getStatisticsImplementor().flush();
				}
				
			}
			else {

				log.trace("Dont need to execute flush");
				source.getActionQueue().clearFromFlushNeededCheck( oldSize );
			}
			
			event.setFlushRequired( flushIsReallyNeeded( event, source ) );

		}

	}

	private boolean flushIsReallyNeeded(AutoFlushEvent event, final EventSource source) {
		return source.getActionQueue()
				.areTablesToBeUpdated( event.getQuerySpaces() ) || 
						source.getFlushMode()==FlushMode.ALWAYS;
	}

	private boolean flushMightBeNeeded(final EventSource source) {
		return !source.getFlushMode().lessThan(FlushMode.AUTO) && 
				source.getDontFlushFromFind() == 0 &&
				source.getPersistenceContext().hasNonReadOnlyEntities();
	}

}