import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.ImageConsumer;
import java.awt.image.IndexColorModel;
import java.io.*;
import java.util.*;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;

/**
 * This test makes sure an 8-bit PNG image is converted into a BufferedImage
 * in approximately the same amount of time whether we use ImageIO or
 * an ImageConsumer/ImageProducer.
 */
public class PNGImageDecoder_8bit_performance {

    interface Model {
        BufferedImage load(byte[] imagedata) throws Exception;
    }

    /**
     * This creates a BufferedImage using ImageIO.
     */
    static class ImageIOModel implements Model {

        @Override
        public BufferedImage load(byte[] imagedata) throws Exception {
            try (InputStream in = new ByteArrayInputStream(imagedata)) {
                return ImageIO.read(in);
            }
        }
    }

    /**
     * This creates a BufferedImage using an ImageConsumer and ImageProducer.
     */
    static class ImageConsumerModel implements Model {

        @Override
        public BufferedImage load(byte[] imagedata) throws Exception {
            Image img = Toolkit.getDefaultToolkit().createImage(imagedata);
            return createBufferedImage(img);
        }
    }

    static BufferedImage createBufferedImage(Image img) throws ExecutionException, InterruptedException {
        CompletableFuture<BufferedImage> future = new CompletableFuture<>();
        img.getSource().startProduction(new ImageConsumer() {
            private int imageWidth, imageHeight;
            private BufferedImage bi;

            @Override
            public void setDimensions(int width, int height) {
                imageWidth = width;
                imageHeight = height;
            }

            @Override
            public void setProperties(Hashtable<?, ?> props) {
                // intentionally empty
            }

            @Override
            public void setColorModel(ColorModel model) {
                // intentionally empty
            }

            @Override
            public void setHints(int hintflags) {
                // intentionally empty
            }

            @Override
            public void setPixels(int x, int y, int w, int h, ColorModel model, byte[] pixels, int off, int scansize) {
                if (bi == null) {
                    bi = new BufferedImage(imageWidth, imageHeight, BufferedImage.TYPE_BYTE_INDEXED, (IndexColorModel) model);
                }
                if (h != 1)
                    throw new UnsupportedOperationException("this test expects sequential rows of pixels");
                if (off != 0)
                    throw new UnsupportedOperationException("this test expects the incoming pixels to start at index zero");

                bi.getRaster().setDataElements(x, y, w, 1, pixels);
            }

            @Override
            public void setPixels(int x, int y, int w, int h, ColorModel model, int[] pixels, int off, int scansize) {
                throw new UnsupportedOperationException();
            }

            @Override
            public void imageComplete(int status) {
                future.complete(bi);
            }
        });
        return future.get();
    }

    public static void main(String[] args) throws Exception {
        for (int squareSize = 500; squareSize <= 10_000; squareSize += 500) {
            byte[] imagedata = createImageData(squareSize);

            Model[] models = new Model[]{
                    new ImageIOModel(),
                    new ImageConsumerModel()
            };

            BufferedImage expected = models[0].load(imagedata);
            BufferedImage actual = models[1].load(imagedata);

            testCorrectness(expected, actual);

            // both of these constants are arbitrary. IMO they help demonstrate
            // the problem (with reasonable accuracy, without excess waiting)

            // run our test sampleCount-many times, and only report the median:
            int sampleCount = 7;

            // each sample creates the image loopCount-many times
            int loopCount = 10;

            long[][] samples = new long[models.length][sampleCount];
            for (int sampleIndex = 0; sampleIndex < sampleCount; sampleIndex++) {
                for (int modelIndex = 0; modelIndex < models.length;
                     modelIndex++) {

                    long t = System.currentTimeMillis();
                    for (int b = 0; b < loopCount; b++) {
                        models[modelIndex].load(imagedata).flush();
                    }
                    t = System.currentTimeMillis() - t;
                    samples[modelIndex][sampleIndex] = t;
                }
            }
            long[] results = new long[models.length];
            long firstMedian = -1;
            for (int modelIndex = 0; modelIndex < models.length; modelIndex++) {
                Arrays.sort(samples[modelIndex]);
                long median = samples[modelIndex][samples[modelIndex].length / 2];
                results[modelIndex] = median;
            }

            System.out.println();
            System.out.println("Square Size\t%\tImageIOModel\tImageConsumerModel");

            StringBuilder sb = new StringBuilder(Integer.toString(squareSize));
            int imageConsumerPercentRelImageIO = Math.round(
                    results[1] * 100f / results[0]);
            sb.append("\t" + imageConsumerPercentRelImageIO);

            for (int a = 0; a < results.length; a++) {
                sb.append("\t" + results[a]);
            }

            System.out.println(sb);

            System.out.println("The ImageConsumer approach took " +
                    imageConsumerPercentRelImageIO + "% of the time the " +
                    "ImageIO approach took.");

            // in my tests the MINIMUM percent that we saw before this enhancement was 109.9%
            // and the MAXIMUM we saw after this enhancement was 104.4%, so a midway point is
            // 107%. We should always be under 107%
            if (imageConsumerPercentRelImageIO > 107)
                throw new Error("The ImageConsumer model should always take close to 100% of what the ImageIO model takes.");
        }
    }

    /**
     * Create a large sample image stored as an 8-bit PNG.
     *
     * @return the byte representation of the PNG image.
     */
    private static byte[] createImageData(int squareSize) throws Exception {
        BufferedImage bi = new BufferedImage(squareSize, squareSize,
                BufferedImage.TYPE_BYTE_INDEXED);
        Random r = new Random(0);
        Graphics2D g = bi.createGraphics();
        for (int a = 0; a < 20000; a++) {
            g.setColor(new Color(r.nextInt(0xffffff)));
            int radius = 10 + r.nextInt(90);
            g.fillOval(r.nextInt(bi.getWidth()), r.nextInt(bi.getHeight()),
                    radius, radius);
        }
        g.dispose();

        try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
            ImageIO.write(bi, "png", out);
            return out.toByteArray();
        }
    }

    /**
     * This unit test is intended to accompany a performance enhancement for
     * PNGImageDecoder. This method makes sure the enhancement didn't cost us
     * any accuracy.
     */
    private static void testCorrectness(BufferedImage expected,
                                        BufferedImage actual) {
        if (expected.getWidth() != actual.getWidth())
            throw new Error();
        if (expected.getHeight() != actual.getHeight())
            throw new Error();
        for (int y = 0; y < expected.getHeight(); y++) {
            for (int x = 0; x < expected.getWidth(); x++) {
                int argb1 = expected.getRGB(x, y);
                int argb2 = actual.getRGB(x, y);
                if (argb1 != argb2) {
                    throw new Error("x = " + x + ", y = " + y);
                }
            }
        }
//        System.out.println("Both models produced identical pixel data.");
    }
}