/*
 * 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
 */

/*
 * @(#)SessionQueue.java	1.25 06/27/07
 */

package com.sun.messaging.jmq.jmsclient;

import java.util.Vector;
import java.util.Hashtable;
import java.io.PrintStream;

import com.sun.messaging.jmq.io.*;

/**
 * A synchronized queue interface to allow threads to wait on a dequeue and be notified when another thread enqueues
 * data to the queue.
 */

class SessionQueue implements Traceable {

    private MessageQueue queue = null;

    protected boolean isLocked = false;
    private boolean sessionIsStopped = false;
    protected boolean isClosed = false;

    protected boolean listenerIsSetLate = false;

    protected boolean debug = Debug.debug;

    private long constructTime = 0;

    /**
     * This property (if defined) will make make the system use SequentialQueue instead of PriorityQueue.
     */
    private static String USE_SEQUENTIAL = System.getProperty("imq.useSequentialQueue");

    protected synchronized void enqueueNotify(Object pkt) {
        enqueue(pkt);
        notifyAll();
    }

    public SessionQueue() {

        if (USE_SEQUENTIAL == null) {
            queue = new PriorityQueue();
        } else {
            queue = new SequentialQueue();
        }
    }

    /**
     * Constructor.
     */
    public SessionQueue(boolean useSequential, int size) {

        if (useSequential) {
            queue = new SequentialQueue(size);
        } else {
            queue = new PriorityQueue();
        }
    }

    /**
     * This method is to respond to the JVM bug (MQ 6174742, 6089070). This is called from
     *
     * 1. SessionImpl's constructor, immediately after it is constructed. 2. From this.isEmpty(). Called only when queue is
     * null.
     */
    protected synchronized void validateQueue() {

        // the statement here is on purpose. set after a new Session is
        // constructed
        if (constructTime == 0) {
            constructTime = System.currentTimeMillis();
        }

        if (queue == null) {
            long diff = System.currentTimeMillis() - this.constructTime;
            throw new java.lang.Error("JVM Error. Message Queue is null. Create time: " + constructTime + " duration: " + diff);
        }
    }

    /**
     * queue size
     */
    protected int size() {
        return queue.size();
    }

    /**
     * Check if queue is empty.
     *
     * @return
     */
    protected boolean isEmpty() {

        if (queue == null) {
            validateQueue();
        }

        return queue.isEmpty();
    }

    /**
     * Clears all the elements from the queue
     **/
    protected void clear() {
        queue.clear();
    }

    /**
     * Get an array of objects from the queue.
     *
     * @return an array of objects from the queue.
     */
    protected Object[] toArray() {
        return queue.toArray();
    }

    /**
     * remove the specified object from the queue.
     *
     * @param obj the object to be removed from the queue.
     * @return true if the object was in the queue and removed.
     */
    protected boolean remove(Object obj) {
        return queue.remove(obj);
    }

    /**
     * Enqueues an object in the queue with no special synchronization.
     *
     * @param nobj new object to be enqueued
     */
    protected void enqueue(Object nobj) {

        queue.enqueue(nobj);

        if (debug) {
            Debug.println(this);
        }
    }

    /**
     * Adds an object to the front of the queue with no special synchronization.
     *
     * @param nobj new object to be added to the front of the queue
     */
    protected void enqueueFirst(Object nobj) {

        queue.enqueueFirst(nobj);

        if (debug) {
            Debug.println(this);
        }
    }

    /**
     * Dequeues an element from the queue without any special synchronization.
     *
     * @return dequeued object, or null if empty queue
     */
    protected Object dequeue() {

        Object obj = null;

        if (queue.isEmpty() == false) {
            obj = queue.dequeue();
        }

        if (debug) {
            Debug.println(this);
        }

        return obj;
    }

    /**
     * If this object is used for SessionReader, when Connection.stop() is called, the SessionReader will eventually come to
     * this method and call setSessionIsStopped(). The thread that blocks on Connection.stop() which calls Session.stop()
     * which calls SessionQueue.stop() will get notified and be able to return.
     *
     */
    protected synchronized Object dequeueWait(long timeout) {
        // if queue is empty or is stopped (isLocked set to true)
        while (isEmpty() || isLocked) {

            if (isClosed) {
                return null;
            }

            if (isLocked) {
                // set this value so that we are sure the session reader is
                // blocked.
                setSessionIsStopped(true);
            }

            if (listenerIsSetLate) {
                /**
                 * listenerIsSetLate flag is reset to false in SessionReader.deliver() method.
                 */
                return null;
            }

            // wait for notification that queue is not empty
            try {
                wait(timeout);
                // check if wait timeout.
                if (isEmpty() && (isLocked == false) && (timeout > 0)) {
                    // if it is timeout, return null.
                    return null;
                }
            } catch (InterruptedException e) {
                Debug.printStackTrace(e);
                // fall to dequeu below
            }

        }

        return dequeue();
    }

    /**
     * default wait forever.
     *
     * @return
     *
     */
    protected synchronized Object dequeueWait() {
        // dupsOkPerf
        return dequeueWait(0);
    }

    protected synchronized void setIsLocked(boolean state) {
        // System.out.println ("queue lock state:; " + state);
        isLocked = state;
        notifyAll();
    }

    protected synchronized boolean getIsLocked() {
        return isLocked;
    }

    // Session reader set this value to true if it is locked and in wait mode.
    protected synchronized void setSessionIsStopped(boolean state) {

        if (debug) {
            Debug.println("session reader is stopped: " + state);
        }

        sessionIsStopped = state;
        notifyAll();
    }

    /**
     * when Connection.stop is called, each session call this method to ensure no messages will be delivered until
     * Connection.start() is called.
     *
     * This method is not returned until SessionReader is locked and blocked.
     */
    protected synchronized void waitUntilSessionStopped() {

        try {
            while (isClosed == false && isLocked && sessionIsStopped == false) {
                wait();
            }
        } catch (InterruptedException e) {
            
        }

    }

    /**
     * Stop the session reader.
     *
     * This method is called from the thread that calls Connection.stop()
     */
    protected synchronized void stop(boolean doWait) {

        setIsLocked(true);

        if (doWait) {
            waitUntilSessionStopped();
        } else {
            sessionIsStopped = true;
        }
    }

    /**
     * Start the session reader
     *
     * This method is called from the thread that calls Connection.start()
     */
    protected synchronized void start() {
        setIsLocked(false);
        setSessionIsStopped(false);
    }

    protected synchronized void close() {
        // unlock queue
        isClosed = true;
        setIsLocked(false);
        if (debug) {
            Debug.println("Session queue closed ...");
        }
    }

    protected synchronized boolean waitMaxInterval(long interval) {
        long endtime = System.currentTimeMillis() + interval;
        long waittime = interval;
        while (!isClosed && !isLocked && !sessionIsStopped) {
            try {
                wait(waittime);
                long currtime = System.currentTimeMillis();
                if (currtime >= endtime) {
                    return true;
                }
                waittime = endtime - currtime;
            } catch (InterruptedException e) {
                return false;
            }
        }
        return false;
    }

    protected boolean getIsClosed() {
        return isClosed;
    }

    /**
     * Prints the queue to the debug display in a human-readable format.
     */
    @Override
    public String toString() {
        Object tmp;
        StringBuffer strbuf = null;

        int cntr = 0;
        strbuf = new StringBuffer(this.getClass().getName() + ": \n");

        Object[] objs = toArray();
        for (cntr = 0; cntr < objs.length; cntr++) {
            tmp = objs[cntr];
            strbuf.append("Element " + cntr + " :" + tmp.toString() + "\n");
        }

        return strbuf.toString();
    }

    protected synchronized void setListenerLateNotify() {
        listenerIsSetLate = true;
        notifyAll();
    }

    protected synchronized void setListenerLate(boolean state) {
        listenerIsSetLate = state;
    }

    protected synchronized boolean isListenerSetLate() {
        return listenerIsSetLate;
    }

    // PRIORITYQ
    @Override
    public void dump(PrintStream ps) {
        ps.println("------ SessionQueue dump ------");
        ps.println("queue size: " + size());

        // Get queu array
        Object[] objs = queue.toArray();
        // get array size
        int size = objs.length;
        for (int i = 0; i < size; i++) {
            // dump each element.
            Object element = objs[i];
            if (element instanceof ReadWritePacket) {
                ((ReadWritePacket) element).dump(ps);
            } else {
                if (element != null && element instanceof Traceable) {
                    ((Traceable) element).dump(ps);
                }
            }

        }
    }

    protected Hashtable getDebugState(boolean verbose) {
        Hashtable ht = new Hashtable();
        ht.put("isLocked", Boolean.valueOf(isLocked));
        ht.put("sessionIsStopped", Boolean.valueOf(sessionIsStopped));
        ht.put("isClosed", Boolean.valueOf(isClosed));
        ht.put("listenerIsSetLate", Boolean.valueOf(listenerIsSetLate));
        ht.put("constructTime", Long.valueOf(constructTime));
        ht.put("queueSize", queue.size());
        if (verbose) {
            Vector v = new Vector();
            Object[] objs = queue.toArray();
            int osize = objs.length;
            Object o = null;
            for (int i = 0; i < osize; i++) {
                o = objs[i];
                if (o instanceof ReadOnlyPacket) {
                    v.add(((ReadOnlyPacket) o).getMessageID());
                } else {
                    v.add(o.toString());
                }
            }
            ht.put("queue", v);
        }
        return ht;
    }
}
