/*
 * Copyright (C) 2014 maartenl
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package mmud.rest.services.admin;

import java.util.List;
import java.util.Set;
import javax.persistence.EntityManager;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.SecurityContext;
import mmud.exceptions.MudWebException;

/**
 *
 * @author maartenl
 */
public abstract class AbstractFacade<T>
{

    private Class<T> entityClass;

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

    protected abstract EntityManager getEntityManager();

    abstract public void create(T entity, SecurityContext sc);

    protected void remove(T entity)
    {
        getEntityManager().remove(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] + 1);
        q.setFirstResult(range[0]);
        return q.getResultList();
    }

    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();
    }

    protected void checkValidation(String name, T attribute)
    {
        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
        Validator validator = factory.getValidator();
        Set<ConstraintViolation<T>> constraintViolations = validator.validate(attribute);
        StringBuffer buffer = null;
        if (!constraintViolations.isEmpty())
        {
            for (ConstraintViolation<T> cv : constraintViolations)
            {
                if (buffer == null)
                {
                    buffer = new StringBuffer();
                }
                buffer.append(cv.getRootBeanClass().getSimpleName()).append(".").append(cv.getPropertyPath()).append(" ").append(cv.getMessage());
            }
        }
        if (buffer != null)
        {
            throw new MudWebException(name, buffer.toString(), Response.Status.BAD_REQUEST);
        }
    }

}