/*

 * Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.awt;

import java.util.LinkedList;

import sun.awt.AWTAccessor;

import sun.awt.AppContext;

import sun.awt.SunToolkit;

/**

 * A mechanism for ensuring that a series of AWTEvents are executed in a

 * precise order, even across multiple AppContexts. The nested events will be

 * dispatched in the order in which their wrapping SequencedEvents were

 * constructed. The only exception to this rule is if the peer of the target of

 * the nested event was destroyed (with a call to Component.removeNotify)

 * before the wrapping SequencedEvent was able to be dispatched. In this case,

 * the nested event is never dispatched.

 *

 * @author David Mendenhall

 */

class SequencedEvent extends AWTEvent implements ActiveEvent {

    /*

     * serialVersionUID

     */

    private static final long serialVersionUID = 547742659238625067L;

    private static final int ID =

        java.awt.event.FocusEvent.FOCUS_LAST + 1;

    private static final LinkedList<SequencedEvent> list = new LinkedList<>();

    private final AWTEvent nested;

    private AppContext appContext;

    private boolean disposed;

    static {

        AWTAccessor.setSequencedEventAccessor(new AWTAccessor.SequencedEventAccessor() {

            public AWTEvent getNested(AWTEvent sequencedEvent) {

                return ((SequencedEvent)sequencedEvent).nested;

            }

            public boolean isSequencedEvent(AWTEvent event) {

                return event instanceof SequencedEvent;

            }

        });

    }

    /**

     * Constructs a new SequencedEvent which will dispatch the specified

     * nested event.

     *

     * @param nested the AWTEvent which this SequencedEvent's dispatch()

     *        method will dispatch

     */

    public SequencedEvent(AWTEvent nested) {

        super(nested.getSource(), ID);

        this.nested = nested;

        // All AWTEvents that are wrapped in SequencedEvents are (at

        // least currently) implicitly generated by the system

        SunToolkit.setSystemGenerated(nested);

        synchronized (SequencedEvent.class) {

            list.add(this);

        }

    }

    /**

     * Dispatches the nested event after all previous nested events have been

     * dispatched or disposed. If this method is invoked before all previous nested events

     * have been dispatched, then this method blocks until such a point is

     * reached.

     * While waiting disposes nested events to disposed AppContext

     *

     * NOTE: Locking protocol.  Since dispose() can get EventQueue lock,

     * dispatch() shall never call dispose() while holding the lock on the list,

     * as EventQueue lock is held during dispatching.  The locks should be acquired

     * in the same order.

     */

    public final void dispatch() {

        try {

            appContext = AppContext.getAppContext();

            if (getFirst() != this) {

                if (EventQueue.isDispatchThread()) {

                    EventDispatchThread edt = (EventDispatchThread)

                        Thread.currentThread();

                    edt.pumpEvents(SentEvent.ID, new Conditional() {

                        public boolean evaluate() {

                            return !SequencedEvent.this.isFirstOrDisposed();

                        }

                    });

                } else {

                    while(!isFirstOrDisposed()) {

                        synchronized (SequencedEvent.class) {

                            try {

                                SequencedEvent.class.wait(1000);

                            } catch (InterruptedException e) {

                                break;

                            }

                        }

                    }

                }

            }

            if (!disposed) {

                KeyboardFocusManager.getCurrentKeyboardFocusManager().

                    setCurrentSequencedEvent(this);

                Toolkit.getEventQueue().dispatchEvent(nested);

            }

        } finally {

            dispose();

        }

    }

    /**

     * true only if event exists and nested source appContext is disposed.

     */

    private final static boolean isOwnerAppContextDisposed(SequencedEvent se) {

        if (se != null) {

            Object target = se.nested.getSource();

            if (target instanceof Component) {

                return ((Component)target).appContext.isDisposed();

            }

        }

        return false;

    }

    /**

     * Sequenced events are dispatched in order, so we cannot dispatch

     * until we are the first sequenced event in the queue (i.e. it's our

     * turn).  But while we wait for our turn to dispatch, the event

     * could have been disposed for a number of reasons.

     */

    public final boolean isFirstOrDisposed() {

        if (disposed) {

            return true;

        }

        // getFirstWithContext can dispose this

        return this == getFirstWithContext() || disposed;

    }

    private final synchronized static SequencedEvent getFirst() {

        return list.getFirst();

    }

    /* Disposes all events from disposed AppContext

     * return first valid event

     */

    private final static SequencedEvent getFirstWithContext() {

        SequencedEvent first = getFirst();

        while(isOwnerAppContextDisposed(first)) {

            first.dispose();

            first = getFirst();

        }

        return first;

    }

    /**

     * Disposes of this instance. This method is invoked once the nested event

     * has been dispatched and handled, or when the peer of the target of the

     * nested event has been disposed with a call to Component.removeNotify.

     *

     * NOTE: Locking protocol.  Since SunToolkit.postEvent can get EventQueue lock,

     * it shall never be called while holding the lock on the list,

     * as EventQueue lock is held during dispatching and dispatch() will get

     * lock on the list. The locks should be acquired in the same order.

     */

    final void dispose() {

      synchronized (SequencedEvent.class) {

            if (disposed) {

                return;

            }

            if (KeyboardFocusManager.getCurrentKeyboardFocusManager().

                    getCurrentSequencedEvent() == this) {

                KeyboardFocusManager.getCurrentKeyboardFocusManager().

                    setCurrentSequencedEvent(null);

            }

            disposed = true;

        }

        // Wake myself up

        if (appContext != null) {

            SunToolkit.postEvent(appContext, new SentEvent());

        }

        SequencedEvent next = null;

        synchronized (SequencedEvent.class) {

          SequencedEvent.class.notifyAll();

          if (list.getFirst() == this) {

              list.removeFirst();

              if (!list.isEmpty()) {

                    next = list.getFirst();

              }

          } else {

              list.remove(this);

          }

      }

        // Wake up waiting threads

        if (next != null && next.appContext != null) {

            SunToolkit.postEvent(next.appContext, new SentEvent());

        }

    }

}