/*
 * Copyright 2005-2010 the original author or authors.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * 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.
 */
package org.wamblee.wicket.transactions;

import java.util.logging.Level;
import java.util.logging.Logger;

import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.transaction.Status;
import javax.transaction.UserTransaction;

import org.apache.wicket.Application;
import org.apache.wicket.Page;
import org.apache.wicket.Response;
import org.apache.wicket.protocol.http.WebApplication;
import org.apache.wicket.protocol.http.WebRequest;
import org.apache.wicket.protocol.http.WebRequestCycle;

/**
 * <p>
 * This class provides an <em>Open Transaction in View</em> implementation for
 * wicket. It provides a custom request cycle that uses the
 * {@link UserTransaction} to make sure that all work is done within a single
 * transaction. In Hibernate context, this is referred to as open session in
 * view. 
 * </p>
 * 
 * <p>
 * The method used by this class is more correctly called
 * <em>Open Transaction in View</em> and has a similar effect to open session in
 * view. It is however more general because it supports any (JTA) transactional
 * resource. Also it is more efficient/scalable than most open session in view
 * implementations because a database connection is only obtained from the
 * connection pool when it is needed.
 * </p>
 * 
 * <p>
 * To use this request cycle, add it in your wicket {@link Application} subclass
 * by overriding
 * {@link Application#newRequestCycle(org.apache.wicket.Request, Response)}. For
 * example:
 * </p>
 * 
 * <pre>
 * &#064;Override
 * public RequestCycle newRequestCycle(Request aRequest, Response aResponse) {
 *     return new OpenTransactionInViewRequestCycle(this, (WebRequest) aRequest,
 *         aResponse);
 * }
 * </pre>
 * 
 * @author Erik Brakkee
 * 
 */
public class OpenTransactionInViewRequestCycle extends WebRequestCycle {

    private static final Logger LOG = Logger.getLogger(OpenTransactionInViewRequestCycle.class.getName());
    
    private static final String JAVA_COMP_USER_TRANSACTION_JNDI = "java:comp/UserTransaction";
    private UserTransaction userTransaction;

    /**
     * Constructs the request cycle.
     * 
     * @param aApplication
     *            Application to use.
     * @param aRequest
     *            Request
     * @param aResponse
     *            Response.
     */
    public OpenTransactionInViewRequestCycle(final WebApplication aApplication,
        final WebRequest aRequest, final Response aResponse) {
        super(aApplication, aRequest, aResponse);
        userTransaction = getUserTransaction();
    }

    @Override
    protected void onBeginRequest() {
        try {
            userTransaction.begin();
        } catch (Exception e) {
            throw new RuntimeException("Could not start transaction", e);
        }
        super.onBeginRequest();
    }

    @Override
    protected void onEndRequest() {
        try {
            if ( LOG.isLoggable(Level.FINEST)) { 
                LOG.finest("Transaction status: " + userTransaction.getStatus());
            }
            if (userTransaction.getStatus() == Status.STATUS_ACTIVE) {
                userTransaction.commit();
            } else if (userTransaction.getStatus() == Status.STATUS_MARKED_ROLLBACK) {
                userTransaction.rollback();
            } else { 
                LOG.warning("Transaction status is '" + userTransaction.getStatus() + "' not committing or rolling back");
            }
        } catch (Exception e) {
            throw new RuntimeException("Could not commit transaction", e);
        }
        super.onEndRequest();
    }

    @Override
    public Page onRuntimeException(Page aPage, RuntimeException aE) {
        super.onEndRequest();
        try {
            userTransaction.rollback();
        } catch (Exception e) {
            throw new RuntimeException("Could not rollback transaction", e);
        }
        return super.onRuntimeException(aPage, aE);
    }

    private UserTransaction getUserTransaction() {
        try {
            InitialContext ctx = new InitialContext();
            return (UserTransaction) ctx
                .lookup(JAVA_COMP_USER_TRANSACTION_JNDI);
        } catch (NamingException e) {
            throw new RuntimeException(
                "Could not obtain user transaction object");
        }
    }
}