/* ===========================================================
 * TradeManager : a application to trade strategies for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2011-2011, by Simon Allen and Contributors.
 *
 * Project Info:  org.trade
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library 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.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 *
 * [Java is a trademark or registered trademark of Oracle, Inc.
 * in the United States and other countries.]
 *
 * (C) Copyright 2011-2011, by Simon Allen and Contributors.
 *
 * Original Author:  Simon Allen;
 * Contributor(s):   -;
 *
 * Changes
 * -------
 *
 */
package org.trade.persistent.dao;

import java.util.ArrayList;
import java.util.List;

import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Expression;
import javax.persistence.criteria.Join;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.trade.core.dao.EntityManagerHelper;

/**
 */
@Stateless
public class RuleHome {

	public RuleHome() {

	}

	/**
	 * Method findById.
	 * 
	 * @param id
	 *            Integer
	 * @return Rule
	 */
	public Rule findById(Integer id) {

		try {
			EntityManager entityManager = EntityManagerHelper.getEntityManager();
			entityManager.getTransaction().begin();
			Rule instance = entityManager.find(Rule.class, id);
			entityManager.getTransaction().commit();
			return instance;
		} catch (Exception re) {
			EntityManagerHelper.rollback();
			throw re;
		} finally {
			EntityManagerHelper.close();
		}
	}

	/**
	 * Method findByMaxVersion.
	 * 
	 * @param strategy
	 *            Strategy
	 * @return Integer
	 */
	public Integer findByMaxVersion(Strategy strategy) {

		try {
			EntityManager entityManager = EntityManagerHelper.getEntityManager();
			entityManager.getTransaction().begin();
			CriteriaBuilder builder = entityManager.getCriteriaBuilder();
			CriteriaQuery<Object> query = builder.createQuery();
			Root<Rule> from = query.from(Rule.class);

			Expression<Integer> id = from.get("version");
			Expression<Integer> minExpression = builder.max(id);
			CriteriaQuery<Object> select = query.select(minExpression);

			List<Predicate> predicates = new ArrayList<Predicate>();
			if (null != strategy) {
				Join<Rule, Strategy> strategies = from.join("strategy");
				Predicate predicate = builder.equal(strategies.get("idStrategy"), strategy.getIdStrategy());
				predicates.add(predicate);
			}
			query.where(predicates.toArray(new Predicate[] {}));
			TypedQuery<Object> typedQuery = entityManager.createQuery(select);
			Object item = typedQuery.getSingleResult();
			entityManager.getTransaction().commit();
			if (null == item)
				item = new Integer(0);

			return (Integer) item;

		} catch (Exception re) {
			EntityManagerHelper.rollback();
			throw re;
		} finally {
			EntityManagerHelper.close();
		}
	}
}