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/*
 * Copyright 2015 dorkbox, llc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package dorkbox.util.swing;

import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.Window;
import java.awt.image.BufferStrategy;

import javax.swing.JComponent;

import dorkbox.util.ActionHandlerLong;
import dorkbox.util.Property;

/**
 * Loop that controls the active rendering process
 */
public
class ActiveRenderLoop implements Runnable {

    @Property
    /**
     * How many frames per second we want the Swing ActiveRender thread to run at
     *
     * NOTE: The ActiveRenderLoop replaces the Swing EDT (only for specified JFrames) in order to enable smoother animations. It is also
     *       important to REMEMBER -- if you add a component to an actively managed JFrame, YOU MUST make sure to call
     *       {@link JComponent#setIgnoreRepaint(boolean)} otherwise this component will "fight" on the EDT for updates. You can completely
     *       disable the EDT by calling {@link NullRepaintManager#install()}
     */
    public static int TARGET_FPS = 30;

    @SuppressWarnings("WhileLoopReplaceableByForEach")
    @Override
    public
    void run() {
        long lastTime = System.nanoTime();

        // 30 FPS is usually just fine. This isn't a game where we need 60+ FPS. We permit this to be changed though, just in case it is.
        final long OPTIMAL_TIME = 1000000000 / TARGET_FPS;
        Graphics graphics = null;

        while (SwingActiveRender.hasActiveRenders) {
            long now = System.nanoTime();
            long updateDeltaNanos = now - lastTime;
            lastTime = now;

            // not synchronized, because we don't care. The worst case, is one frame of animation behind.
            for (int i = 0; i < SwingActiveRender.activeRenderEvents.size(); i++) {
                ActionHandlerLong actionHandlerLong = SwingActiveRender.activeRenderEvents.get(i);

                //noinspection unchecked
                actionHandlerLong.handle(updateDeltaNanos);
            }

            // this needs to be synchronized because we don't want to our frame removed WHILE we are rendering it.
            synchronized (SwingActiveRender.activeRenders) {
                for (int i = 0; i < SwingActiveRender.activeRenders.size(); i++) {
                    Window window = SwingActiveRender.activeRenders.get(i);

                    final BufferStrategy buffer = window.getBufferStrategy();

                    // maybe the frame was closed
                    if (buffer != null) {
                        try {
                            graphics = buffer.getDrawGraphics();
                            window.paint(graphics);
                        } catch (Exception e) {
                            e.printStackTrace();
                        } finally {
                            if (graphics != null) {
                                graphics.dispose();

                                // blit the back buffer to the screen
                                if (!buffer.contentsLost()) {
                                    buffer.show();
                                }
                            }
                        }
                    }
                }
            }

            // Sync the display on some systems (on Linux, this fixes event queue problems)
            Toolkit.getDefaultToolkit()
                   .sync();

            try {
                // Converted to int before the division, because IDIV is
                // 1 order magnitude faster than LDIV (and int's work for us anyways)
                // see: http://www.cs.nuim.ie/~jpower/Research/Papers/2008/lambert-qapl08.pdf
                // Also, down-casting (long -> int) is not expensive w.r.t IDIV/LDIV
                //noinspection NumericCastThatLosesPrecision
                final int l = (int) (lastTime - System.nanoTime() + OPTIMAL_TIME);
                final int millis = l / 1000000;
                if (millis > 1) {
                    Thread.sleep(millis);
                }
                else {
                    // try to keep the CPU from getting slammed. We couldn't match our target FPS, so loop again
                    Thread.yield();
                }
            } catch (InterruptedException ignored) {
            }
        }
    }
}