package dao;


import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.util.ArrayList;
import java.util.List;

import javax.annotation.PostConstruct;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceUnitUtil;

import org.springframework.transaction.annotation.Transactional;

public abstract class JpaDao<T, PK extends Serializable> implements Dao<T, PK> {
	protected Class<T> entityClass;

	// protected static EntityManagerFactory entityManagerFactory = null;

	@PersistenceContext
	protected EntityManager entityManager;

	protected PersistenceUnitUtil persistenceUnitUtil;

	// public static void setEntityManagerFactory(EntityManagerFactory factory)
	// {
	// entityManagerFactory = factory;
	// }

	public JpaDao() {
		ParameterizedType genericSuperclass = (ParameterizedType) getClass().getGenericSuperclass();
		this.entityClass = (Class<T>) genericSuperclass.getActualTypeArguments()[0];
		// entityManager = entityManagerFactory.createEntityManager();
	}

	@PostConstruct
	private void initPersistenceUnitUtil() {
		this.persistenceUnitUtil = entityManager.getEntityManagerFactory().getPersistenceUnitUtil();
	}

	@Transactional
	public T create(T t) {
		entityManager.persist(t);
		return t;
	}

	@Transactional(readOnly = true)
	public T read(PK id) {
		return entityManager.find(entityClass, id);
	}

	@Transactional
	public T update(T t) {
		return entityManager.merge(t);
	}

	@Transactional
	public void delete(T t) {
		t = entityManager.merge(t);
		entityManager.remove(t);
	}

	public List<T> getAll() {
		List<T> result = entityManager.createQuery("from " + entityClass.getSimpleName(), entityClass).getResultList();
		return result == null ? new ArrayList<T>() : result;
	}

	public long count() {
		return ((Number) entityManager.createQuery("select count(e) from " + entityClass.getSimpleName() + " e").getSingleResult()).longValue();
	}

	public boolean isLoaded(T t) {
		return persistenceUnitUtil.isLoaded(t);
	}

	protected boolean isFieldLoaded(T t, String fieldName) {
		return persistenceUnitUtil.isLoaded(t, fieldName);
	}
}