/*
 * @(#)TimerQueue.java	1.28 01/11/29
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */



package javax.swing;



import java.util.*;



/**
 * Internal class to manage all Timers using one thread.
 * TimerQueue manages a queue of Timers. The Timers are chained
 * together in a linked list sorted by the order in which they will expire.
 *
 * @version 1.28 11/29/01
 * @author Dave Moore
 */
class TimerQueue implements Runnable
{
    private static final Object sharedInstanceKey =
        new StringBuffer("TimerQueue.sharedInstanceKey");
    private static final Object expiredTimersKey =
        new StringBuffer("TimerQueue.expiredTimersKey");

    Timer   firstTimer;
    boolean running;

    /* Lock object used in place of class object for synchronization. 
     * (4187686)
     */
    private static final Object classLock = new Object();


    /**
     * Constructor for TimerQueue.
     */
    public TimerQueue() {
        super();

        // Now start the TimerQueue thread.
        start();
    }


    public static TimerQueue sharedInstance() {
        synchronized (classLock) {
            TimerQueue sharedInst = (TimerQueue)
                                    SwingUtilities.appContextGet(
                                                        sharedInstanceKey);
            if (sharedInst == null) {
                sharedInst = new TimerQueue();
                SwingUtilities.appContextPut(sharedInstanceKey, sharedInst);
            }
            return sharedInst;
        }
    }


    synchronized void start() {
        if (running) {
            throw new RuntimeException("Can't start a TimerQueue " +
                                       "that is already running");
        }
        else {
            Thread timerThread = new Thread(this, "TimerQueue");
            try {
                timerThread.setDaemon(true);
            }
            catch (SecurityException e) {
            }
            timerThread.start();
            running = true;
        }
    }


    synchronized void stop() {
        running = false;
        notify();
    }


    synchronized void addTimer(Timer timer, long expirationTime) {
        Timer previousTimer;
        Timer nextTimer;

        // If the Timer is already in the queue, then ignore the add.
        if (timer.running) {
            return;
        }

        previousTimer = null;
        nextTimer = firstTimer;

        // Insert the Timer into the linked list in the order they will
        // expire.  If two timers expire at the same time, put the newer entry
        // later so they expire in the order they came in.

        while (nextTimer != null) {
            if (nextTimer.expirationTime > expirationTime) break;

            previousTimer = nextTimer;
            nextTimer = nextTimer.nextTimer;
        }

        if (previousTimer == null) {
            firstTimer = timer;
        }
        else {
            previousTimer.nextTimer = timer;
        }

        timer.expirationTime = expirationTime;
        timer.nextTimer = nextTimer;
        timer.running = true;
        notify();
    }


    synchronized void removeTimer(Timer timer) {
        Timer   previousTimer;
        Timer   nextTimer;
        boolean found;

        if (!timer.running) return;

        previousTimer = null;
        nextTimer = firstTimer;
        found = false;

        while (nextTimer != null) {
            if (nextTimer == timer) {
                found = true;
                break;
            }

            previousTimer = nextTimer;
            nextTimer = nextTimer.nextTimer;
        }

        if (!found) return;

        if (previousTimer == null) {
            firstTimer = timer.nextTimer;
        }
        else {
            previousTimer.nextTimer = timer.nextTimer;
        }

        timer.expirationTime = 0;
        timer.nextTimer = null;
        timer.running = false;
    }


    synchronized boolean containsTimer(Timer timer) {
        return timer.running;
    }


    /**
     * If there are a ton of timers, this method may never return.  It loops
     * checking to see if the head of the Timer list has expired.  If it has,
     * it posts the Timer and reschedules it if necessary.
     */
    synchronized long postExpiredTimers() {
        Timer   timer;
        long    currentTime;
        long    timeToWait;

        // The timeToWait we return should never be negative and only be zero
        // when we have no Timers to wait for.

        do {
            timer = firstTimer;
            if (timer == null) return 0;

            currentTime = System.currentTimeMillis();
            timeToWait = timer.expirationTime - currentTime;

            if (timeToWait <= 0) {
                try {
                    timer.post();  // have timer post an event
                }
                catch (SecurityException e) {
                }

                // Remove the timer from the queue
                removeTimer(timer);

                // This tries to keep the interval uniform at
                // the cost of drift.
                if (timer.isRepeats()) {
                    addTimer(timer, currentTime + timer.getDelay());
                }
            }

            // Allow other threads to call addTimer() and removeTimer()
            // even when we are posting Timers like mad.  Since the wait()
            // releases the lock, be sure not to maintain any state
            // between iterations of the loop.

            try {
                wait(1);
            }
            catch (InterruptedException e) {
            }
        } while (timeToWait <= 0);

        return timeToWait;
    }


    public synchronized void run() {
        long timeToWait;

        try {
            while (running) {
                timeToWait = postExpiredTimers();
                try {
                    wait(timeToWait);
                }
                catch (InterruptedException e) {
                }
            }
        }
        catch (ThreadDeath td) {
            running = false;
            // Mark all the timers we contain as not being queued.
            Timer timer = firstTimer;
            while (timer != null) {
                timer.eventQueued = false;
                timer = timer.nextTimer;
            }
            SystemEventQueueUtilities.restartTimerQueueThread();
            throw td;
        }
    }


    public synchronized String toString() {
        StringBuffer buf;
        Timer nextTimer;

        buf = new StringBuffer();
        buf.append("TimerQueue (");

        nextTimer = firstTimer;
        while (nextTimer != null) {
            buf.append(nextTimer.toString());

            nextTimer = nextTimer.nextTimer;
            if (nextTimer != null) buf.append(", ");
        }

        buf.append(")");
        return buf.toString();
    }
}