/*
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.qpid.client;

import org.apache.log4j.Logger;

import java.util.Enumeration;
import java.util.ArrayList;
import java.util.concurrent.atomic.AtomicBoolean;
import javax.jms.*;
import javax.jms.IllegalStateException;

public class AMQQueueBrowser implements QueueBrowser
{
    private static final Logger _logger = Logger.getLogger(AMQQueueBrowser.class);


    private AtomicBoolean _isClosed = new AtomicBoolean();
    private final AMQSession _session;
    private final AMQQueue _queue;
    private final ArrayList<BasicMessageConsumer> _consumers = new ArrayList<BasicMessageConsumer>();
    private final String _messageSelector;


    AMQQueueBrowser(AMQSession session, AMQQueue queue, String messageSelector) throws JMSException
    {
        _session = session;
        _queue = queue;
        _messageSelector = (messageSelector == null) || (messageSelector.trim().length() == 0) ? null : messageSelector;
        BasicMessageConsumer consumer = (BasicMessageConsumer) _session.createBrowserConsumer(_queue, _messageSelector, false);
        consumer.close();        
    }

    public Queue getQueue() throws JMSException
    {
        checkState();
        return _queue;
    }

    private void checkState() throws JMSException
    {
        if (_isClosed.get())
        {
            throw new IllegalStateException("Queue Browser");
        }
        if (_session.isClosed())
        {
            throw new IllegalStateException("Session is closed");
        }

    }

    public String getMessageSelector() throws JMSException
    {

        checkState();
        return _messageSelector;
    }

    public Enumeration getEnumeration() throws JMSException
    {
        checkState();
        final BasicMessageConsumer consumer = (BasicMessageConsumer) _session.createBrowserConsumer(_queue, _messageSelector, false);
        _consumers.add(consumer);

        return new Enumeration()
        {


            Message _nextMessage = consumer.receive();


            public boolean hasMoreElements()
            {
                _logger.info("QB:hasMoreElements:" + (_nextMessage != null));
                return (_nextMessage != null);
            }

            public Object nextElement()
            {
                Message msg = _nextMessage;
                try
                {
                    _logger.info("QB:nextElement about to receive");

                    _nextMessage = consumer.receive();
                    _logger.info("QB:nextElement received:" + _nextMessage);
                }
                catch (JMSException e)    
                {
                    _logger.warn("Exception caught while queue browsing", e);
                    _nextMessage = null;
                }

                return msg;
            }
        };
    }

    public void close() throws JMSException
    {
        for (BasicMessageConsumer consumer : _consumers)
        {
            consumer.close();
        }
        _consumers.clear();
    }


}
