package org.activityinfo.server.database.hibernate.dao;

/*
 * #%L
 * ActivityInfo Server
 * %%
 * Copyright (C) 2009 - 2013 UNICEF
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the 
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public 
 * License along with this program.  If not, see
 * <http://www.gnu.org/licenses/gpl-3.0.html>.
 * #L%
 */

import com.google.inject.Inject;
import com.google.inject.Injector;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;
import java.util.logging.Logger;

/**
 * MethodInterceptor that implements declarative transaction management. See
 * {@link org.activityinfo.server.database.hibernate.dao.Transactional}
 *
 * @author Alex Bertram
 */
public class TransactionalInterceptor implements MethodInterceptor {

    private static final Logger LOGGER = Logger.getLogger(TransactionalInterceptor.class.getName());

    private Injector injector;

    @Inject
    public void setInjector(Injector injector) {
        this.injector = injector;
    }

    @Override
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
        EntityManager em = injector.getInstance(EntityManager.class);
        EntityTransaction tx = em.getTransaction();

        // allow joining of transactions if there is an enclosing @Transactional
        // method
        if (tx.isActive()) {
            return methodInvocation.proceed();
        }

        tx.begin();

        Object result = attemptInvocation(methodInvocation, tx);

        // everything was normal so commit the txn (do not move into try block
        // as it interferes with the advised method's throwing semantics)
        if (tx.isActive()) {
            tx.commit();
            LOGGER.fine("[invoke] Committed the transaction.");
        }

        return result;
    }

    private Object attemptInvocation(MethodInvocation methodInvocation, EntityTransaction tx) throws Throwable {
        try {
            return methodInvocation.proceed();
        } catch (Exception e) {
            // rollback database to original state
            tx.rollback();

            // propagate whatever exception is thrown anyway
            throw e;
        }
    }
}