package edu.pjwstk.sri.lab2.dao;

import java.util.List;

import javax.annotation.Resource;
import javax.ejb.EJBContext;
import javax.ejb.Lock;
import javax.ejb.LockType;
import javax.ejb.Stateless;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;
import javax.ejb.TransactionManagement;
import javax.ejb.TransactionManagementType;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.TypedQuery;
import javax.rmi.CORBA.Util;

import edu.pjwstk.sri.lab2.dto.Cart;
import edu.pjwstk.sri.lab2.dto.OrderItem;
import edu.pjwstk.sri.lab2.model.Product;

/**
 * DAO for Product
 */
@Stateless
@TransactionManagement(TransactionManagementType.CONTAINER)
public class ProductDao {

    @Resource
    private EJBContext context;

    @PersistenceContext(unitName = "sri2-persistence-unit")
    private EntityManager em;
     @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
    public void create(Product entity) {
        em.persist(entity);
    }
     @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public void deleteById(Long id) {
        Product entity = em.find(Product.class, id);
        if (entity != null) {
            em.remove(entity);
        }
    }
     @TransactionAttribute(TransactionAttributeType.NEVER)
    public Product findById(Long id) {
        return em.find(Product.class, id);
    }
     @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public Product update(Product entity) {

        return em.merge(entity);

    }

     public void makeOrder(Cart cart) {
         try {
             for(OrderItem oi : cart.getCartItems()) {
                    Product prod_database = findById(oi.getProduct().getId());
                    prod_database.setStock(prod_database.getStock() - oi.getAmount());
                    update(prod_database);
                }
             }catch(Throwable th){
                    context.setRollbackOnly();
                }
     }

     @Lock(LockType.READ)
     @TransactionAttribute(TransactionAttributeType.NEVER)
    public List<Product> listAll(Integer startPosition, Integer maxResult) {
        TypedQuery<Product> findAllQuery = em
                .createQuery(
                        "SELECT DISTINCT p FROM Product p LEFT JOIN FETCH p.category ORDER BY p.id",
                        Product.class);
        if (startPosition != null) {
            findAllQuery.setFirstResult(startPosition);
        }
        if (maxResult != null) {
            findAllQuery.setMaxResults(maxResult);
        }
        return findAllQuery.getResultList();
    }
}