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package br.com.jhonsapp.bootstrap.object.persistence.generic;

import java.util.List;

import javax.persistence.EntityExistsException;
import javax.persistence.EntityManager;
import javax.persistence.NoResultException;
import javax.persistence.PersistenceContext;
import javax.persistence.TypedQuery;

import br.com.jhonsapp.bootstrap.object.domain.generic.DomainObject;
import br.com.jhonsapp.bootstrap.object.persistence.parameter.Parameter;

public class AbstractGenericDAO implements GenericDAO {

	private final static String UNIT_NAME = "PERSISTENCE-UNIT";

	@PersistenceContext(unitName = UNIT_NAME)
	private EntityManager entityManager;
	private Class entityClass;

	public AbstractGenericDAO(Class entityClass) {
		this.entityClass = entityClass;
	}

	@Override
	public boolean persist(T object) {
		try {
			entityManager.persist(object);
			return true;
		} catch (EntityExistsException e) {
			return false;
		}
	}

	@Override
	public T update(T object) {
		return entityManager.merge(object);
	}

	@Override
	public boolean remove(T object) {
		if (object.getId() > 0L) {
			entityManager.remove(update(object));
			return true;
		} else {
			return false;
		}
	}

	@Override
	public T findById(long id) {

		if (id <= 0L) {
			throw new RuntimeException("The id can not be less than or equal to zero.");
		}

		return (T) entityManager.find(this.entityClass, id);
	}

	/**
	 * This generic method was designed to create a TypedQuery and return it
	 * there.
	 * 
	 * @param namedQuery
	 *            the query that will be executed.
	 * @param parameter
	 *            a set of keys and values as a parameter that will be used in
	 *            the query.
	 * @return an object that represents a TypedQuery.
	 */
	private TypedQuery generateNamedQuery(String namedQuery, Parameter parameter, Class returnType) {

		TypedQuery typedQuery = entityManager.createNamedQuery(namedQuery, returnType);

		if (parameter != null) {

			for (String key : parameter.getKeySet()) {

				if (key != null) {
					typedQuery = typedQuery.setParameter(key, parameter.get(key));
				}
			}
		}
		return typedQuery;
	}

	/**
	 * This generic method was designed to perform queries that return a single
	 * result.
	 * 
	 * @param namedQuery
	 *            the query that will be executed.
	 * @param parameter
	 *            a set of keys and values as a parameter that will be used in
	 *            the query.
	 * @return an object or null if the query does not return results.
	 **/
	@SuppressWarnings("unchecked")
	protected T find(String namedQuery, Parameter parameter) {
		T entity = null;

		try {
			entity = (T) this.generateNamedQuery(namedQuery, parameter, this.entityClass).getSingleResult();

			return entity;
		} catch (NoResultException exception) {
			return entity;
		}
	}

	/**
	 * This generic method was designed to perform queries that return objects
	 * of the primitive type.
	 * 
	 * @param namedQuery
	 *            the query that will be executed.
	 * @return objects of the primitive type.
	 */
	@SuppressWarnings("unchecked")
	protected  X find(String namedQuery, Parameter parameter, Class returnType) {

		X value = null;

		try {
			value = (X) this.generateNamedQuery(namedQuery, parameter, returnType).getSingleResult();

			return value;
		} catch (NoResultException exception) {
			return value;
		}
	}

	/**
	 * This generic method was designed to perform queries that return a set of
	 * objects.
	 * 
	 * @param namedQuery
	 *            the query that will be executed.
	 * @return a set of objects or null if the query does not return results.
	 */
	@SuppressWarnings("unchecked")
	protected List findList(String namedQuery, Parameter parameter) {
		List entities = null;

		try {

			entities = (List) this.generateNamedQuery(namedQuery, parameter, this.entityClass).getResultList();

			return entities;
		} catch (NoResultException exception) {
			return entities;
		}
	}

	/**
	 * This generic method was designed to perform queries that return a set of
	 * objects.
	 * 
	 * @param namedQuery
	 *            the query that will be executed.
	 * @param startPosition
	 *            the position of the first result.
	 * @param maxResult
	 *            the maximum number of results to retrieve.
	 * @return a set of objects or null if the query does not return results.
	 **/
	@SuppressWarnings("unchecked")
	protected List findList(String namedQuery, Parameter parameter, int startPosition, int maxResult) {
		List entities = null;

		try {

			entities = (List) this.generateNamedQuery(namedQuery, parameter, this.entityClass)
					.setFirstResult(startPosition).setMaxResults(maxResult).getResultList();

			return entities;
		} catch (NoResultException exception) {
			return entities;
		}
	}

	/**
	 * This generic method was designed to perform native queries that return a
	 * set of objects.
	 * 
	 * @param sql
	 *            the query that will be executed.
	 * 
	 * @return a list of objects that satisfy the query.
	 */
	@SuppressWarnings("unchecked")
	protected List findList(String sql) {

		return entityManager.createNativeQuery(sql, this.entityClass).getResultList();
	}
}