/*
    * EL4J, the Extension Library for the J2EE, adds incremental enhancements to
    * the spring framework, http://el4j.sf.net
    * Copyright (C) 2006 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.util.Iterator;
  import java.util.List;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.hibernate.criterion.Criterion;
  import org.hibernate.criterion.DetachedCriteria;
  import org.hibernate.criterion.Junction;
  import org.hibernate.criterion.Restrictions;
  
  import ch.elca.el4j.services.search.QueryObject;
  import ch.elca.el4j.services.search.criterias.AbstractCriteria;
  import ch.elca.el4j.services.search.criterias.AndCriteria;
  import ch.elca.el4j.services.search.criterias.ComparisonCriteria;
  import ch.elca.el4j.services.search.criterias.Criteria;
  import ch.elca.el4j.services.search.criterias.LikeCriteria;
  import ch.elca.el4j.services.search.criterias.NotCriteria;
  import ch.elca.el4j.services.search.criterias.OrCriteria;
  import ch.elca.el4j.services.search.criterias.Order;
  
  /**
   *
   * This class transforms the EL4J Criteria of a given <code>QueryObject</code>
   * into the corresponding Hibernate DetachedCriteria.
   *
   * @svnLink $Revision: 3874 $;$Date: 2009-08-04 14:25:40 +0200 (Di, 04. Aug 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/CriteriaTransformer.java $
   *
   * @author Alex Mathey (AMA)
   * @author Philipp Oser (POS)
   */
  public class CriteriaTransformer {
  
  	private static Logger s_logger = LoggerFactory.getLogger(CriteriaTransformer.class);
  	
  	/**
  	 * Hide default constructor.
  	 */
  	protected CriteriaTransformer() { };
  	
  	/**
  	 * Transforms EL4J Criteria of the given <code>QueryObject</code> into the
  	 * corresponding Hibernate DetachedCriteria.
  	 *
  	 * @param query
  	 *            the query object whose criteria will be transformed
  	 * @param domainObjectClass
  	 *            the class of the domain object for which the Hibernate
  	 *            criteria will be generated
  	 * @return the Hibernate criteria corresponding to the
  	 *         <code>QueryObject</code>'s EL4J criteria.
  	 */
  	public static DetachedCriteria transform(QueryObject query,
  		Class<?> domainObjectClass) {
  		
  		// Hibernate criteria for the domain object.
  		DetachedCriteria hibernateCriteria
  			= DetachedCriteria.forClass(domainObjectClass);
  		
  		// List of EL4J criteria.
  		List<Criteria> el4jCriteriaList = query.getCriteriaList();
  		
  		// Conversion from EL4J criteria to Hibernate criteria.
  		Iterator<Criteria> it = el4jCriteriaList.iterator();
  		
  		while (it.hasNext()) {
  			Criteria currentEl4jCriteria = (Criteria) it.next();
  			
  			Criterion hibernateCriterion =
  				el4jCriteria2HibernateCriterion(currentEl4jCriteria);
  			if (hibernateCriterion != null) {
  				hibernateCriteria.add(hibernateCriterion);
  			}
  		}
  		
  		addOrderConstraints(hibernateCriteria, query);
  		
  		return hibernateCriteria;
  	}
  
  	protected static void addOrderConstraints (DetachedCriteria hibernateCriteria,
 		QueryObject query) {
 		
 		List<Order> orderConstraints = query.getOrderConstraints();
 		for (Order o : orderConstraints){
 			if (o.isAscending()) {
 				hibernateCriteria.addOrder(org.hibernate.criterion.Order.asc(o.getPropertyName()));
 			} else {
 				hibernateCriteria.addOrder(org.hibernate.criterion.Order.desc(o.getPropertyName()));
 			}
 		}
 		
 	}
 	
 	
 	/**
 	 * Converts EL4J Criteria to Hibernate Criterion.
 	 * @param criteria
 	 * @return the converted Criterion
 	 */
 	protected static Criterion el4jCriteria2HibernateCriterion(Criteria criteria) {
 		Criterion criterion = null;
 		
 		if (criteria instanceof OrCriteria) {
 			Junction combination = Restrictions.disjunction();
 			
 			addCriteriaListToJunction(((OrCriteria) criteria).getCriterias(), combination);
 			criterion = combination;
 		} else if (criteria instanceof AndCriteria) {
 			Junction combination = Restrictions.conjunction();
 			
 			addCriteriaListToJunction(((AndCriteria) criteria).getCriterias(), combination);
 			criterion = combination;
 		} else if (criteria instanceof NotCriteria) {
 			Criteria innerCriteria = ((NotCriteria) criteria).getCriteria();
 			criterion = Restrictions.not(el4jCriteria2HibernateCriterion(innerCriteria));
 		} else if (criteria instanceof AbstractCriteria) {
 			AbstractCriteria abstractCrit = (AbstractCriteria) criteria;
 			
 			String currentCriteriaField = abstractCrit.getField();
 			Object currentCriteriaValue = abstractCrit.getValue();
 
 			if (criteria instanceof LikeCriteria) {
 				LikeCriteria currentEl4jLikeCriteria = (LikeCriteria) criteria;
 				if (currentEl4jLikeCriteria.isCaseSensitive().booleanValue()) {
 					criterion = Restrictions.like(currentCriteriaField,
 						currentCriteriaValue);
 				} else {
 					criterion = Restrictions.like(currentCriteriaField,
 						currentCriteriaValue).ignoreCase();
 				}
 			} else if (criteria instanceof ComparisonCriteria) {
 				String operator = ((ComparisonCriteria) criteria).getOperator();
 				if (operator.equals("=")) {
 					criterion = Restrictions.eq(currentCriteriaField,
 										currentCriteriaValue);
 				} else if (operator.equals("<")) {
 					criterion = Restrictions.lt(currentCriteriaField,
 						currentCriteriaValue);
 				} else if (operator.equals("<=")) {
 					criterion = Restrictions.le(currentCriteriaField,
 						currentCriteriaValue);
 				} else if (operator.equals(">")) {
 					criterion = Restrictions.gt(currentCriteriaField,
 						currentCriteriaValue);
 				} else if (operator.equals(">=")) {
 					criterion = Restrictions.ge(currentCriteriaField,
 						currentCriteriaValue);
 				} else if (operator.equals("!=")) {
 					criterion = Restrictions.ne(currentCriteriaField,
 						currentCriteriaValue);
 				} else {
 					s_logger.info(" Operator not handled " + operator);
 				}
 				
 			} else {
 				s_logger.info(" Criteria not handled " + criteria);
 			}
 		} else {
 			s_logger.info(" Criteria not handled " + criteria);
 		}
 		return criterion;
 	}
 
 	/**
 	 * @param currentEl4jCriteria
 	 * @param combination
 	 */
 	protected static void addCriteriaListToJunction(
 		List<Criteria> criterias, Junction combination) {
 		for (Criterion c : apply2HibernateCriterion(criterias)) {
 			combination.add(c);
 		}
 	}
 	
 	/**
 	 * Apply operator (from functional programming)
 	 * @param criterias must not be null
 	 * @return
 	 */
 	protected static Criterion[] apply2HibernateCriterion(List<Criteria> criterias ){
 		Criterion[] result = new Criterion[criterias.size()];
 		
 		for (int i = 0; i < criterias.size(); i++) {
 			result[i] = el4jCriteria2HibernateCriterion(criterias.get(i));
 		}
 		return result;
 	}
 	
 }