/*
    * EL4J, the Extension Library for the J2EE, adds incremental enhancements to
    * the spring framework, http://el4j.sf.net
    * Copyright (C) 2009 by ELCA Informatique SA, Av. de la Harpe 22-24,
    * 1000 Lausanne, Switzerland, http://www.elca.ch
    *
    * EL4J is published under the GNU Lesser General Public License (LGPL)
    * Version 2.1. See http://www.gnu.org/licenses/
    *
   * 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.
   *
   * For alternative licensing, please contact info@elca.ch
   */
  package ch.elca.el4j.services.persistence.hibernate.criteria;
  
  import java.lang.reflect.Field;
  import java.util.List;
  
  import org.apache.commons.lang.SerializationUtils;
  import org.hibernate.Criteria;
  import org.hibernate.criterion.Criterion;
  import org.hibernate.criterion.DetachedCriteria;
  import org.hibernate.criterion.Order;
  import org.hibernate.impl.CriteriaImpl;
  import org.hibernate.impl.CriteriaImpl.OrderEntry;
  
  /**
   * A utility class that allows to perform some modifications on {@link DetachedCriteria}s.
   * <b>ATTENTION: This class depends on the actual Hibernate Criteria implementation ({@link CriteriaImpl})</b>
   *
   * @svnLink $Revision: 3916 $;$Date: 2009-09-15 12:19:53 +0200 (Di, 15. Sep 2009) $;$Author: swismer $;$URL: https://el4j.svn.sourceforge.net/svnroot/el4j/branches/el4j_3_1/el4j/framework/modules/hibernate/src/main/java/ch/elca/el4j/services/persistence/hibernate/criteria/DetachedCriteriaUtils.java $
   *
   * @author Stefan Wismer (SWI)
   */
  public final class DetachedCriteriaUtils {
  	
  	/**
  	 * The hidden constructor.
  	 */
  	private DetachedCriteriaUtils() { }
  	
  	/**
  	 * @param criteria    the criteria to clone
  	 * @return            the cloned criteria
  	 */
  	public static DetachedCriteria clone(DetachedCriteria criteria) {
  		return (DetachedCriteria) SerializationUtils.clone(criteria);
  	}
  	
  	/**
  	 * @param criteria    the criteria to manipulate
  	 * @param orders      the orders to remove. If no orders are provided, all orders will be removed
  	 * @return            the criteria
  	 */
  	@SuppressWarnings("unchecked")
  	public static DetachedCriteria removeOrders(DetachedCriteria criteria, Order... orders) {
  		List<OrderEntry> orderEntries = (List<OrderEntry>) getCriteriaField(criteria, "orderEntries");
  		orderEntries.clear();
  		
  		return criteria;
  	}
  	
  	/**
  	 * @param criteria    the criteria whose projection should be removed
  	 * @return            the "clean" criteria
  	 */
  	public static DetachedCriteria removeProjection(DetachedCriteria criteria) {
  		criteria.setProjection(null);
  		criteria.setResultTransformer(Criteria.ROOT_ENTITY);
  		return criteria;
  	}
  	
  	/**
  	 * @param criteria    the criteria whose projection should be removed
  	 * @return            the "clean" criteria
  	 */
  	@SuppressWarnings("unchecked")
  	public static DetachedCriteria removeCriterionEntries(DetachedCriteria criteria) {
  		List<Criterion> criterionEntries = (List<Criterion>) getCriteriaField(criteria, "criterionEntries");
  		criterionEntries.clear();
  		
  		return criteria;
  	}
  	
  	/**
  	 * @param criteria    the criteria whose criterion entries to get
  	 * @return            a list of criterion entries
  	 */
  	@SuppressWarnings("unchecked")
  	public static List<Criterion> getCriterionEntries(DetachedCriteria criteria) {
  		return (List<Criterion>) getCriteriaField(criteria, "criterionEntries");
  	}
  	
  	/**
  	 * Get the field value of the Criteria.
  	 * 
 	 * @param criteria     the criteria to get the field
 	 * @param fieldName    the field name
 	 * @return             the value stored in that field
 	 */
 	private static Object getCriteriaField(DetachedCriteria criteria, String fieldName) {
 		try {
 			Field implField = DetachedCriteria.class.getDeclaredField("impl");
 			implField.setAccessible(true);
 			CriteriaImpl impl = (CriteriaImpl) implField.get(criteria);
 			
 			Field orderField = CriteriaImpl.class.getDeclaredField(fieldName);
 			orderField.setAccessible(true);
 			
 			return orderField.get(impl);
 		} catch (Exception e) {
 			throw new IllegalStateException("Implementation of DetachedCriteria or CriteriaImpl has changed!");
 		}
 	}
 }