package org.alfresco.repo.avm.hibernate;

/*
 * Copyright (C) 2006 Alfresco, Inc.
 *
 * Licensed under the Mozilla Public License version 1.1 
 * with a permitted attribution clause. You may obtain a
 * copy of the License at
 *
 *   http://www.alfresco.org/legal/license.txt
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the
 * License.
 */

import java.util.Random;

import org.alfresco.repo.avm.AVMException;
import org.alfresco.repo.avm.AVMNotFoundException;
import org.hibernate.HibernateException;
import org.hibernate.JDBCException;
import org.hibernate.ObjectNotFoundException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.StaleStateException;
import org.hibernate.Transaction;
import org.hibernate.exception.GenericJDBCException;
import org.hibernate.exception.LockAcquisitionException;
import org.springframework.dao.DataRetrievalFailureException;
import org.springframework.dao.DeadlockLoserDataAccessException;
import org.springframework.dao.OptimisticLockingFailureException;
import org.springframework.orm.hibernate3.HibernateTemplate;

/**
 * Helper for DAOs.
 * @author britt
 */
public class HibernateTxn extends HibernateTemplate
{
    /**
     * The SessionFactory.
     */
    private SessionFactory fSessionFactory;
    
    /**
     * The random number generator for inter-retry sleep.
     */
    private Random fRandom;
    
    /**
     * Make one up.
     * @param sessionFactory The SessionFactory.
     */
    public HibernateTxn()
    {
        fRandom = new Random();
    }

    /**
     * Set the Hibernate Session factory.
     * @param factory
     */
    public void setSessionFactory(SessionFactory factory)
    {
        super.setSessionFactory(factory);
        fSessionFactory = factory;
    }
    
    /**
     * Perform a set of operations under a single Hibernate transaction.
     * Keep trying if the operation fails because of a concurrency issue.
     * @param callback The worker.
     * @param write Whether this is a write operation.
     */
    public void perform(HibernateTxnCallback callback, boolean write)
    {
        Session sess = null;
        Transaction txn = null;
        while (true)
        {
            try
            {
                sess = fSessionFactory.openSession();
                txn = sess.beginTransaction();
                callback.perform(sess);
                txn.commit();
                return;
            }
            catch (Throwable t)
            {
                // TODO Add appropriate logging.
                if (txn != null)
                {
                    try
                    {
                        txn.rollback();
                    }
                    catch (HibernateException he)
                    {
                        // Do nothing.
                    }
                    // Translate the exception.
                    if (t instanceof JDBCException)
                    {
                        t = convertJdbcAccessException((JDBCException)t);
                    }
                    else if (t instanceof HibernateException)
                    {
                        t = convertHibernateAccessException((HibernateException)t);
                    }
                    // If we've lost a race or we've deadlocked, retry.
                    if (t instanceof DeadlockLoserDataAccessException)
                    {
                        try
                        {
                            long interval;
                            synchronized (fRandom)
                            {
                                interval = fRandom.nextInt(1000);
                            }
                            Thread.sleep(interval);
                            continue;
                        }
                        catch (InterruptedException ie)
                        {
                           // Do nothing.
                        }
                        continue;
                    }
                    if (t instanceof OptimisticLockingFailureException)
                    {
                        continue;
                    }
                }
                if (t instanceof AVMException)
                {
                    throw (AVMException)t;
                }
                if (t instanceof DataRetrievalFailureException)
                {
                    throw new AVMNotFoundException("Object not found.", t);
                }
                throw new AVMException("Unrecoverable error.", t);
            }
            finally
            {
                if (sess != null)
                {
                    try
                    {
                        sess.close();
                    }
                    catch (HibernateException he)
                    {
                        // Do nothing.
                    }
                }
            }
        }
    }
}