/*
 * Copyright (c) 2000, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

/*
 * @(#)QueueBrowserImpl.java	1.12 06/27/07
 */

package com.sun.messaging.jmq.jmsclient;

import java.util.Enumeration;
import java.util.Vector;
import javax.jms.*;

import com.sun.messaging.AdministeredObject;

/**
 * A client uses a QueueBrowser to look at messages on a queue without removing them.
 *
 * <P>
 * The browse methods return a java.util.Enumeration that is used to scan the queue's messages. It may be an enumeration
 * of the entire content of a queue or it may only contain the messages matching a message selector.
 *
 * <P>
 * Messages may be arriving and expiring while the scan is done. JMS does not require the content of an enumeration to
 * be a static snapshot of queue content. Whether these changes are visible or not depends on the JMS provider.
 *
 * @see javax.jms.QueueSession#createBrowser(Queue)
 * @see javax.jms.QueueSession#createBrowser(Queue, String)
 * @see javax.jms.QueueReceiver
 */

public class QueueBrowserImpl implements QueueBrowser {

    private SessionImpl session = null;
    private Queue queue = null;
    private String messageSelector = null;
    private Vector consumers = new Vector();

    private boolean isClosed = false;

    public QueueBrowserImpl(SessionImpl session, Queue queue) throws JMSException {
        this(session, queue, null);
    }

    public QueueBrowserImpl(SessionImpl session, Queue queue, String selector) throws JMSException {
        if (queue == null) {
            String errorString = AdministeredObject.cr.getKString(AdministeredObject.cr.X_INVALID_DESTINATION_NAME, "null");
            throw new InvalidDestinationException(errorString, AdministeredObject.cr.X_INVALID_DESTINATION_NAME);
        }
        this.session = session;
        this.queue = queue;
        this.messageSelector = selector;
        init();
    }

    private void init() throws JMSException {
        // ConnectionConsumer workaround 4715054
        session.checkBrowserCreation();
        session.verifyDestination(queue, messageSelector, true);
    }

    /**
     * Get the queue associated with this queue browser.
     *
     * @return the queue
     *
     * @exception JMSException if JMS fails to get the queue associated with this Browser due to some JMS error.
     */

    @Override
    public Queue getQueue() throws JMSException {
        checkState();
        return queue;
    }

    /**
     * Get this queue browser's message selector expression.
     *
     * @return this queue browser's message selector
     *
     * @exception JMSException if JMS fails to get the message selector for this browser due to some JMS error.
     */

    @Override
    public String getMessageSelector() throws JMSException {
        checkState();
        return messageSelector;
    }

    /**
     * Get an enumeration for browsing the current queue messages in the order they would be received.
     *
     * @return an enumeration for browsing the messages
     *
     * @exception JMSException if JMS fails to get the enumeration for this browser due to some JMS error.
     */

    @Override
    public Enumeration getEnumeration() throws JMSException {

        checkState();

        return (new BrowserConsumer(this, queue, messageSelector));
    }

    protected void addBrowserConsumer(BrowserConsumer consumer) {
        consumers.addElement(consumer);
    }

    protected void removeBrowserConsumer(BrowserConsumer consumer) {
        consumers.removeElement(consumer);
    }

    /**
     * Since a provider may allocate some resources on behalf of a QueueBrowser outside the JVM, clients should close them
     * when they are not needed. Relying on garbage collection to eventually reclaim these resources may not be timely
     * enough.
     *
     * @exception JMSException if a JMS fails to close this Browser due to some JMS error.
     */

    @Override
    public void close() throws JMSException {
        BrowserConsumer consumer = null;
        for (int i = consumers.size() - 1; i >= 0; i--) {
            consumer = (BrowserConsumer) consumers.elementAt(i);
            consumer.close();
        }

        isClosed = true;
    }

    protected SessionImpl getSession() {
        return session;
    }

    protected void checkState() throws JMSException {

        if (isClosed) {
            String errorString = AdministeredObject.cr.getKString(AdministeredObject.cr.X_BROWSER_CLOSED);
            throw new javax.jms.IllegalStateException(errorString, AdministeredObject.cr.X_BROWSER_CLOSED);
        }

        session.checkSessionState();

    }
}
