package br.edu.ifpb.memoriam.filter;

import java.io.IOException;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import org.apache.log4j.Logger;
import org.hibernate.StaleObjectStateException;

import br.edu.ifpb.memoriam.dao.ManagedEMContext;
import br.edu.ifpb.memoriam.dao.PersistenceUtil;


/**
 * Este filtro controla o EntityManager para conversa��es longas. O EM � colocado e retirado
 * da HttpSession a cada request para servlets e JSPs. Quando o servlet e os JSPs utilizarem
 * o EM (via DAOs, por exemplo) ele estar� dispon�vel via PersistenceUtil.getCurrentEntityManager().
 * Este filtro redireciona para a p�gina principal de consulta caso a HttpSession tenha sido fechada. Ou seja,
 * se ele for ativado sem que uma sess~]ao tenha sido previamente criada, ele redirecionar� para esta p�gina index.jsp.
 * @author Fred
 *
 */
@WebFilter (urlPatterns = {"*.do", "*.jsp"})
public class EntityManagerConversationFilter implements Filter {
    private static Logger logger = Logger.getLogger(EntityManagerConversationFilter.class);

    private EntityManagerFactory emf;

    public static final String ENTITYMANAGER_FACTORY_KEY = "currentEntityManager";

    public static final String END_OF_CONVERSATION_FLAG = "endofconversation";

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {

        EntityManager currentEntityManager;

        // Try to get a EntityManager from the HttpSession
        HttpSession httpSession =
            ((HttpServletRequest) request).getSession();
        EntityManager disconnectedEM =
            (EntityManager) httpSession
                .getAttribute(ENTITYMANAGER_FACTORY_KEY);

        // Context path
        String context = ((HttpServletRequest) request).getServletPath();
        context += ": ";
        try {

            // Start a new conversation or in the middle?
            if (disconnectedEM == null) {
                logger.debug(context + ">>> Nova conversa��o");
                // Define o modo manual de flush
                currentEntityManager = emf.createEntityManager();
                ((org.hibernate.Session) currentEntityManager.getDelegate())
                    .setFlushMode(org.hibernate.FlushMode.MANUAL);
            } else {
                logger.debug(context + "< Continuando conversa��o");
                currentEntityManager = disconnectedEM;
            }

            ManagedEMContext.bind(emf, currentEntityManager);
            logger.debug(context + "Associou EntityManager ao contexto");

            logger.debug(context + "Processando servlet/JSP");
            chain.doFilter(request, response);

            // End or continue the long-running conversation?
            if (request.getAttribute(END_OF_CONVERSATION_FLAG) != null
                    || request.getParameter(END_OF_CONVERSATION_FLAG) != null) {

                currentEntityManager.close();
                logger.debug(context + "Fechando o EntityManager");

                ManagedEMContext.unbind(emf);
                logger.debug(context + "Desassociou EntityManager do contexto");

                if (((HttpServletRequest) request).isRequestedSessionIdValid()) {
                    httpSession.removeAttribute(ENTITYMANAGER_FACTORY_KEY);
                    logger.debug(context + "Retirou EntityManager da HttpSession");
                }

                logger.debug(context + "<<< Fim da conversa��o");

            } else {
                ManagedEMContext.unbind(emf);
                logger.debug(context + "Desassociou EntityManager do contexto");

                if (((HttpServletRequest) request).isRequestedSessionIdValid()) {
                    httpSession.setAttribute(ENTITYMANAGER_FACTORY_KEY, currentEntityManager);
                    logger.debug(context + "Associou EntityManager a HttpSession");
                }

                logger.debug(context + "> Retornando para o usuario");
            }

        } catch (StaleObjectStateException staleEx) {
            logger.error(context
                            + "This interceptor does not implement optimistic concurrency control!");
            logger.error(context
                            + "Your application will not work until you add compensation actions!");
            throw staleEx;
        } catch (Throwable ex) {
            // Rollback only
            logger.debug(context + "Original exception:", ex);
            try {
                if (PersistenceUtil.getCurrentEntityManager().getTransaction().isActive()) {
                    logger.debug(context
                                    + "Tentando rollback da transa��o ap�s exception");
                    PersistenceUtil.getCurrentEntityManager().getTransaction().rollback();
                }
            } catch (Throwable rbEx) {
                logger.error(context
                        + "Rollback n�o efetivado!",
                        rbEx);
            } finally {
                logger.error(context + "Cleanup after exception!");

                // Cleanup
                currentEntityManager = ManagedEMContext.unbind(emf);
                logger.debug(context + "Desassociou EntityManager do contexto");

                currentEntityManager.close();
                logger.debug(context + "Fechou EntityManager ap�s exception");

                if (((HttpServletRequest) request).isRequestedSessionIdValid()) {
                    httpSession.setAttribute(ENTITYMANAGER_FACTORY_KEY, null);
                    logger.debug(context + "Removeu EntityManager da HttpSession");
                }

            }

            // Let others handle it... maybe another interceptor for exceptions?
            throw new ServletException(ex);
        } finally {

        }
    }

    public void init(FilterConfig filterConfig) throws ServletException {
        emf = PersistenceUtil.getEntityManagerFactory();
    }

    public void destroy() {
    }

}