/*

 * Copyright (c) 2019, 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

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 */

package sun.java2d.metal;

import sun.awt.util.ThreadGroupUtils;

import sun.java2d.pipe.RenderBuffer;

import sun.java2d.pipe.RenderQueue;

import java.security.AccessController;

import java.security.PrivilegedAction;

import static sun.java2d.pipe.BufferedOpCodes.DISPOSE_CONFIG;

import static sun.java2d.pipe.BufferedOpCodes.SYNC;

/**

 * OGL-specific implementation of RenderQueue.  This class provides a

 * single (daemon) thread that is responsible for periodically flushing

 * the queue, thus ensuring that only one thread communicates with the native

 * OpenGL libraries for the entire process.

 */

public class MTLRenderQueue extends RenderQueue {

    private static MTLRenderQueue theInstance;

    private final QueueFlusher flusher;

    private MTLRenderQueue() {

        /*

         * The thread must be a member of a thread group

         * which will not get GCed before VM exit.

         */

        flusher = AccessController.doPrivileged((PrivilegedAction<QueueFlusher>) QueueFlusher::new);

    }

    /**

     * Returns the single MTLRenderQueue instance.  If it has not yet been

     * initialized, this method will first construct the single instance

     * before returning it.

     */

    public static synchronized MTLRenderQueue getInstance() {

        if (theInstance == null) {

            theInstance = new MTLRenderQueue();

        }

        return theInstance;

    }

    /**

     * Flushes the single MTLRenderQueue instance synchronously.  If an

     * MTLRenderQueue has not yet been instantiated, this method is a no-op.

     * This method is useful in the case of Toolkit.sync(), in which we want

     * to flush the OGL pipeline, but only if the OGL pipeline is currently

     * enabled.  Since this class has few external dependencies, callers need

     * not be concerned that calling this method will trigger initialization

     * of the OGL pipeline and related classes.

     */

    public static void sync() {

        if (theInstance != null) {

            theInstance.lock();

            try {

                theInstance.ensureCapacity(4);

                theInstance.getBuffer().putInt(SYNC);

                theInstance.flushNow();

            } finally {

                theInstance.unlock();

            }

        }

    }

    /**

     * Disposes the native memory associated with the given native

     * graphics config info pointer on the single queue flushing thread.

     */

    public static void disposeGraphicsConfig(long pConfigInfo) {

        MTLRenderQueue rq = getInstance();

        rq.lock();

        try {

            // make sure we make the context associated with the given

            // GraphicsConfig current before disposing the native resources

            MTLContext.setScratchSurface(pConfigInfo);

            RenderBuffer buf = rq.getBuffer();

            rq.ensureCapacityAndAlignment(12, 4);

            buf.putInt(DISPOSE_CONFIG);

            buf.putLong(pConfigInfo);

            // this call is expected to complete synchronously, so flush now

            rq.flushNow();

        } finally {

            rq.unlock();

        }

    }

    /**

     * Returns true if the current thread is the OGL QueueFlusher thread.

     */

    public static boolean isQueueFlusherThread() {

        return (Thread.currentThread() == getInstance().flusher.thread);

    }

    @Override

    public void flushNow() {

        // assert lock.isHeldByCurrentThread();

        try {

            flusher.flushNow();

        } catch (Exception e) {

            System.err.println("exception in flushNow:");

            e.printStackTrace();

        }

    }

    public void flushAndInvokeNow(Runnable r) {

        // assert lock.isHeldByCurrentThread();

        try {

            flusher.flushAndInvokeNow(r);

        } catch (Exception e) {

            System.err.println("exception in flushAndInvokeNow:");

            e.printStackTrace();

        }

    }

    private native void flushBuffer(long buf, int limit);

    private void flushBuffer() {

        // assert lock.isHeldByCurrentThread();

        int limit = buf.position();

        if (limit > 0) {

            // process the queue

            flushBuffer(buf.getAddress(), limit);

        }

        // reset the buffer position

        buf.clear();

        // clear the set of references, since we no longer need them

        refSet.clear();

    }

    private class QueueFlusher implements Runnable {

        private boolean needsFlush;

        private Runnable task;

        private Error error;

        private final Thread thread;

        public QueueFlusher() {

            String name = "Java2D Queue Flusher";

            thread = new Thread(ThreadGroupUtils.getRootThreadGroup(),

                    this, name, 0, false);

            thread.setDaemon(true);

            thread.setPriority(Thread.MAX_PRIORITY);

            thread.start();

        }

        public synchronized void flushNow() {

            // wake up the flusher

            needsFlush = true;

            notify();

            // wait for flush to complete

            while (needsFlush) {

                try {

                    wait();

                } catch (InterruptedException e) {

                }

            }

            // re-throw any error that may have occurred during the flush

            if (error != null) {

                throw error;

            }

        }

        public synchronized void flushAndInvokeNow(Runnable task) {

            this.task = task;

            flushNow();

        }

        public synchronized void run() {

            boolean timedOut = false;

            while (true) {

                while (!needsFlush) {

                    try {

                        timedOut = false;

                        /*

                         * Wait until we're woken up with a flushNow() call,

                         * or the timeout period elapses (so that we can

                         * flush the queue periodically).

                         */

                        wait(100);

                        /*

                         * We will automatically flush the queue if the

                         * following conditions apply:

                         *   - the wait() timed out

                         *   - we can lock the queue (without blocking)

                         *   - there is something in the queue to flush

                         * Otherwise, just continue (we'll flush eventually).

                         */

                        if (!needsFlush && (timedOut = tryLock())) {

                            if (buf.position() > 0) {

                                needsFlush = true;

                            } else {

                                unlock();

                            }

                        }

                    } catch (InterruptedException e) {

                    }

                }

                try {

                    // reset the throwable state

                    error = null;

                    // flush the buffer now

                    flushBuffer();

                    // if there's a task, invoke that now as well

                    if (task != null) {

                        task.run();

                    }

                } catch (Error e) {

                    error = e;

                } catch (Exception x) {

                    System.err.println("exception in QueueFlusher:");

                    x.printStackTrace();

                } finally {

                    if (timedOut) {

                        unlock();

                    }

                    task = null;

                    // allow the waiting thread to continue

                    needsFlush = false;

                    notify();

                }

            }

        }

    }

}