package ejava.examples.ejbwar.inventory.dao;
   
   import java.util.List;
   
   import javax.inject.Inject;
   import javax.persistence.EntityManager;
   import javax.persistence.TypedQuery;
   
   import ejava.examples.ejbwar.inventory.bo.Category;
  import ejava.examples.ejbwar.inventory.bo.Product;
  import ejava.examples.ejbwar.inventory.cdi.Inventory;
  
  /**
   * This DAO implementation uses JPA and an injected entity manager to 
   * perform CRUD operations on inventory data.
   */
  public class InventoryDAOImpl implements InventoryDAO {
  	@Inject @Inventory
  	private EntityManager em;
  	
  	public void setEntityManager(EntityManager em) {
  		this.em = em;
  	}
  
  	@Override
  	public void createCategory(Category category) {
  		em.persist(category);
  	}
  	
  	@Override
  	public Category getCategory(int id) {
  		return em.find(Category.class, id);
  	}
  	
  	@Override
  	public List<Category> findCategoryByName(String criteria, int offset, int limit) {
  		TypedQuery<Category> query = em.createNamedQuery(Category.FIND_BY_NAME, Category.class)
  				.setParameter("criteria", criteria==null ? "%" : criteria);
  		applyBounds(query, offset, limit);
  		return query.getResultList();
  	}
  	
  	@Override
  	public void detachCategory(Category category) {
  		em.detach(category);
  	}
  	
  	@Override
  	public void deleteCategory(Category category) {
  		em.remove(category);
  	}
  	
  	@Override
  	public void addProduct(Product p) {
  		em.persist(p);
  	}
  	
  	@Override
  	public Product getProduct(int id) {
  		return em.find(Product.class, id);
  	}
  	
  	@Override
  	public Product updateProduct(Product product) {
  		return em.merge(product);
  	}
  	@Override
  	public List<Product> findProductsByName(String criteria, int offset, int limit) {
  		TypedQuery<Product> query = em.createNamedQuery(Product.FIND_BY_NAME, Product.class)
  				.setParameter("criteria", criteria==null ? "%" : criteria);
  		applyBounds(query, offset, limit);
  		return query.getResultList();
  	}
  	
  	@Override
  	public void deleteProduct(Product product) {
  		//make sure we are dealing with a managed instance
  		if (!em.contains(product)) {
  			product = getProduct(product.getId());
  		}
  		if (product!=null) {
  			for (Category category :em.createNamedQuery(Category.FIND_BY_PRODUCT, Category.class)
  					.setParameter("product", product)
  					.getResultList()) {
  				//since product and catagory are currently managed a simple
  				//object match should work here
  				category.getProducts().remove(product);
  			}
  		em.remove(product);
  		}
  	}
  	
  	private void applyBounds(TypedQuery<?> query, int offset, int limit) {
  		if (offset > 0) {
  			query.setFirstResult(offset);
  		}
  		if (limit > 0) {
  			query.setMaxResults(limit);
  		}
 	}
 	
 }