//$Id: VersionType.java 7736 2005-08-03 20:03:34Z steveebersole $
package org.hibernate.type;

import java.util.Comparator;

import org.hibernate.engine.SessionImplementor;

/**
 * A <tt>Type</tt> that may be used to version data.
 * @author Gavin King
 */
public interface VersionType extends Type {
	/**
	 * Generate an initial version.
	 *
	 * @param session The session from which this request originates.
	 * @return an instance of the type
	 */
	public Object seed(SessionImplementor session);

	/**
	 * Increment the version.
	 *
	 * @param session The session from which this request originates.
	 * @param current the current version
	 * @return an instance of the type
	 */
	public Object next(Object current, SessionImplementor session);

	/**
	 * Get a comparator for version values.
	 *
	 * @return The comparator to use to compare different version values.
	 */
	public Comparator getComparator();

	/**
	 * Are the two version values considered equal?
	 *
	 * @param x One value to check.
	 * @param y The other value to check.
	 * @return true if the values are equal, false otherwise.
	 */
	public boolean isEqual(Object x, Object y);
}