package auction.dao.hibernate;

import auction.dao.*;
import auction.persistence.HibernateUtil;
import org.hibernate.*;
import org.hibernate.criterion.*;

import java.util.*;
import java.io.Serializable;
import java.lang.reflect.ParameterizedType;

/**
 * Implements the generic CRUD data access operations using Hibernate APIs.
 * <p>
 * To write a DAO, subclass and parameterize this class with your persistent class.
 * Of course, assuming that you have a traditional 1:1 appraoch for Entity:DAO design.
 * <p>
 * You have to inject a current Hibernate <tt>Session</tt> to use a DAO. Otherwise, this
 * generic implementation will use <tt>HibernateUtil.getSessionFactory()</tt> to obtain the
 * curren <tt>Session</tt>.
 *
 * @see HibernateDAOFactory
 *
 * @author Christian Bauer
 */
public abstract class GenericHibernateDAO<T, ID extends Serializable>
        implements GenericDAO<T, ID> {

    private Class<T> persistentClass;
    private Session session;

    public GenericHibernateDAO() {
        this.persistentClass = (Class<T>) ((ParameterizedType) getClass()
                                .getGenericSuperclass()).getActualTypeArguments()[0];
     }

    public void setSession(Session s) {
        this.session = s;
    }

    protected Session getSession() {
        if (session == null)
            session = HibernateUtil.getSessionFactory().getCurrentSession();
        return session;
    }

    public Class<T> getPersistentClass() {
        return persistentClass;
    }

    @SuppressWarnings("unchecked")
    public T findById(ID id, boolean lock) {
        T entity;
        if (lock)
            entity = (T) getSession().load(getPersistentClass(), id, LockMode.UPGRADE);
        else
            entity = (T) getSession().load(getPersistentClass(), id);

        return entity;
    }

    @SuppressWarnings("unchecked")
    public List<T> findAll() {
        return findByCriteria();
    }

    @SuppressWarnings("unchecked")
    public List<T> findByExample(T exampleInstance, String... excludeProperty) {
        Criteria crit = getSession().createCriteria(getPersistentClass());
        Example example =  Example.create(exampleInstance);
        for (String exclude : excludeProperty) {
            example.excludeProperty(exclude);
        }
        crit.add(example);
        return crit.list();
    }

    @SuppressWarnings("unchecked")
    public T makePersistent(T entity) {
        getSession().saveOrUpdate(entity);
        return entity;
    }

    public void makeTransient(T entity) {
        getSession().delete(entity);
    }

    public void flush() {
        getSession().flush();
    }

    public void clear() {
        getSession().clear();
    }

    /**
     * Use this inside subclasses as a convenience method.
     */
    @SuppressWarnings("unchecked")
    protected List<T> findByCriteria(Criterion... criterion) {
        Criteria crit = getSession().createCriteria(getPersistentClass());
        for (Criterion c : criterion) {
            crit.add(c);
        }
        return crit.list();
   }

}