/**
 * Copyright (c) 2014 Oracle and/or its affiliates. All rights reserved.
 *
 * You may not modify, use, reproduce, or distribute this software except in
 * compliance with  the terms of the License at:
 * https://github.com/javaee/tutorial-examples/LICENSE.txt
 */
package com.forest.ejb;

import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;

/**
 *
 * @author markito
 */
public abstract class AbstractFacade<T>  {
    private Class<T> entityClass;
    
    public AbstractFacade() {
        
    }

    public AbstractFacade(final Class<T> entityClass) {
        this.entityClass = entityClass;
    }

    protected abstract EntityManager getEntityManager();

    public void create(T entity) {
        getEntityManager().persist(entity);
    }

    public void edit(T entity) {
        getEntityManager().merge(entity);
    }

    public void remove(T entity) {
        getEntityManager().remove(getEntityManager().merge(entity));
    }

    public T find(Object id) {
        return getEntityManager().find(entityClass, id);
    }

    public List<T> findAll() {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        return getEntityManager().createQuery(cq).getResultList();
    }

    public List<T> findRange(int[] range) {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        cq.select(cq.from(entityClass));
        javax.persistence.Query q = getEntityManager().createQuery(cq);
        q.setMaxResults(range[1] - range[0]);
        q.setFirstResult(range[0]);
        return q.getResultList();
    }
    
    public List<T> findRange(int[] range, CriteriaQuery query) {
        javax.persistence.Query q = getEntityManager().createQuery(query);
        q.setMaxResults(range[1] - range[0]);
        q.setFirstResult(range[0]);
        return q.getResultList();
    }

    
    public CriteriaBuilder getCriteriaBuilder() {
        return getEntityManager().getCriteriaBuilder();
    }
    
    public int count() {
        javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
        javax.persistence.criteria.Root<T> rt = cq.from(entityClass);
        cq.select(getEntityManager().getCriteriaBuilder().count(rt));
        javax.persistence.Query q = getEntityManager().createQuery(cq);
        return ((Long) q.getSingleResult()).intValue();
    }

}
