package eu.mjdev.desktop.helpers.gif;

import java.net.*;
import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.image.*;

@SuppressWarnings("ALL")
public class GifDecoder {
    public static final int STATUS_OK = 0;
    public static final int STATUS_FORMAT_ERROR = 1;
    public static final int STATUS_OPEN_ERROR = 2;
    protected BufferedInputStream in;
    protected int status;
    protected int width;
    protected int height;
    protected boolean gctFlag;
    protected int gctSize;
    protected int loopCount = 1;
    protected int[] gct;
    protected int[] lct;
    protected int[] act;
    protected int bgIndex;
    protected int bgColor;
    protected int lastBgColor;
    protected int pixelAspect;
    protected boolean lctFlag;
    protected boolean interlace;
    protected int lctSize;
    protected int ix, iy, iw, ih;
    protected Rectangle lastRect;
    protected BufferedImage image;
    protected BufferedImage lastImage;
    protected byte[] block = new byte[256];
    protected int blockSize = 0;
    protected int dispose = 0;
    protected int lastDispose = 0;
    protected boolean transparency = false;
    protected int delay = 0;
    protected int transIndex;
    protected static final int MaxStackSize = 4096;
    protected short[] prefix;
    protected byte[] suffix;
    protected byte[] pixelStack;
    protected byte[] pixels;
    protected ArrayList frames;
    protected int frameCount;

    static class GifFrame {
        public GifFrame(BufferedImage im, int del) {
            image = im;
            delay = del;
        }

        public BufferedImage image;
        public int delay;
    }

    public int getDelay(int n) {
        delay = -1;
        if ((n >= 0) && (n < frameCount)) {
            delay = ((GifFrame) frames.get(n)).delay;
        }
        return delay;
    }

    public int getFrameCount() {
        return frameCount;
    }

    public BufferedImage getImage() {
        return getFrame(0);
    }

    public int getLoopCount() {
        return loopCount;
    }

    protected void setPixels() {
        int[] dest = ((DataBufferInt) image.getRaster().getDataBuffer()).getData();
        if (lastDispose > 0) {
            if (lastDispose == 3) {
                int n = frameCount - 2;
                if (n > 0) {
                    lastImage = getFrame(n - 1);
                } else {
                    lastImage = null;
                }
            }
            if (lastImage != null) {
                int[] prev = ((DataBufferInt) lastImage.getRaster().getDataBuffer()).getData();
                System.arraycopy(prev, 0, dest, 0, width * height);
                if (lastDispose == 2) {
                    Graphics2D g = image.createGraphics();
                    Color c;
                    if (transparency) {
                        c = new Color(0, 0, 0, 0);
                    } else {
                        c = new Color(lastBgColor);
                    }
                    g.setColor(c);
                    g.setComposite(AlphaComposite.Src);
                    g.fill(lastRect);
                    g.dispose();
                }
            }
        }
        int pass = 1;
        int inc = 8;
        int iline = 0;
        for (int i = 0; i < ih; i++) {
            int line = i;
            if (interlace) {
                if (iline >= ih) {
                    pass++;
                    switch (pass) {
                        case 2:
                            iline = 4;
                            break;
                        case 3:
                            iline = 2;
                            inc = 4;
                            break;
                        case 4:
                            iline = 1;
                            inc = 2;
                    }
                }
                line = iline;
                iline += inc;
            }
            line += iy;
            if (line < height) {
                int k = line * width;
                int dx = k + ix;
                int dlim = dx + iw;
                if ((k + width) < dlim) {
                    dlim = k + width;
                }
                int sx = i * iw;
                while (dx < dlim) {
                    int index = ((int) pixels[sx++]) & 0xff;
                    int c = act[index];
                    if (c != 0) {
                        dest[dx] = c;
                    }
                    dx++;
                }
            }
        }
    }

    public BufferedImage getFrame(int n) {
        BufferedImage im = null;
        if ((n >= 0) && (n < frameCount)) {
            im = ((GifFrame) frames.get(n)).image;
        }
        return im;
    }

    public Dimension getFrameSize() {
        return new Dimension(width, height);
    }

    public int read(BufferedInputStream is) {
        init();
        if (is != null) {
            in = is;
            readHeader();
            if (!err()) {
                readContents();
                if (frameCount < 0) {
                    status = STATUS_FORMAT_ERROR;
                }
            }
        } else {
            status = STATUS_OPEN_ERROR;
        }
        try {
            if (is != null) is.close();
        } catch (IOException e) {
            // no op
        }
        return status;
    }

    public int read(InputStream is) {
        init();
        if (is != null) {
            if (!(is instanceof BufferedInputStream))
                is = new BufferedInputStream(is);
            in = (BufferedInputStream) is;
            readHeader();
            if (!err()) {
                readContents();
                if (frameCount < 0) {
                    status = STATUS_FORMAT_ERROR;
                }
            }
        } else {
            status = STATUS_OPEN_ERROR;
        }
        try {
           if(is != null) is.close();
        } catch (IOException e) {
            // no op
        }
        return status;
    }

    public int read(String name) {
        status = STATUS_OK;
        try {
            name = name.trim().toLowerCase();
            //noinspection IndexOfReplaceableByContains
            if ((name.indexOf("file:") >= 0) || (name.indexOf(":/") > 0)) {
                URL url = new URL(name);
                in = new BufferedInputStream(url.openStream());
            } else {
                in = new BufferedInputStream(new FileInputStream(name));
            }
            status = read(in);
        } catch (IOException e) {
            status = STATUS_OPEN_ERROR;
        }
        return status;
    }

    protected void decodeImageData() {
        int NullCode = -1;
        int npix = iw * ih;
        int available,
                clear,
                code_mask,
                code_size,
                end_of_information,
                in_code,
                old_code,
                bits,
                code,
                count,
                i,
                datum,
                data_size,
                first,
                top,
                bi,
                pi;
        if ((pixels == null) || (pixels.length < npix)) {
            pixels = new byte[npix]; // allocate new pixel array
        }
        if (prefix == null) prefix = new short[MaxStackSize];
        if (suffix == null) suffix = new byte[MaxStackSize];
        if (pixelStack == null) pixelStack = new byte[MaxStackSize + 1];
        data_size = read();
        clear = 1 << data_size;
        end_of_information = clear + 1;
        available = clear + 2;
        old_code = NullCode;
        code_size = data_size + 1;
        code_mask = (1 << code_size) - 1;
        for (code = 0; code < clear; code++) {
            prefix[code] = 0;
            suffix[code] = (byte) code;
        }
        datum = bits = count = first = top = pi = bi = 0;
        for (i = 0; i < npix; ) {
            if (top == 0) {
                if (bits < code_size) {
                    if (count == 0) {
                        count = readBlock();
                        if (count <= 0)
                            break;
                        bi = 0;
                    }
                    datum += (((int) block[bi]) & 0xff) << bits;
                    bits += 8;
                    bi++;
                    count--;
                    continue;
                }
                code = datum & code_mask;
                datum >>= code_size;
                bits -= code_size;
                if ((code > available) || (code == end_of_information))
                    break;
                if (code == clear) {
                    code_size = data_size + 1;
                    code_mask = (1 << code_size) - 1;
                    available = clear + 2;
                    old_code = NullCode;
                    continue;
                }
                if (old_code == NullCode) {
                    pixelStack[top++] = suffix[code];
                    old_code = code;
                    first = code;
                    continue;
                }
                in_code = code;
                if (code == available) {
                    pixelStack[top++] = (byte) first;
                    code = old_code;
                }
                while (code > clear) {
                    pixelStack[top++] = suffix[code];
                    code = prefix[code];
                }
                first = ((int) suffix[code]) & 0xff;
                if (available >= MaxStackSize) {
                    pixelStack[top++] = (byte) first;
                    continue;
                }
                pixelStack[top++] = (byte) first;
                prefix[available] = (short) old_code;
                suffix[available] = (byte) first;
                available++;
                if (((available & code_mask) == 0)
                        && (available < MaxStackSize)) {
                    code_size++;
                    code_mask += available;
                }
                old_code = in_code;
            }
            top--;
            pixels[pi++] = pixelStack[top];
            i++;
        }
        for (i = pi; i < npix; i++) {
            pixels[i] = 0;
        }
    }

    protected boolean err() {
        return status != STATUS_OK;
    }

    protected void init() {
        status = STATUS_OK;
        frameCount = 0;
        frames = new ArrayList();
        gct = null;
        lct = null;
    }

    protected int read() {
        int curByte = 0;
        try {
            curByte = in.read();
        } catch (IOException e) {
            status = STATUS_FORMAT_ERROR;
        }
        return curByte;
    }

    protected int readBlock() {
        blockSize = read();
        int n = 0;
        if (blockSize > 0) {
            try {
                int count;
                while (n < blockSize) {
                    count = in.read(block, n, blockSize - n);
                    if (count == -1)
                        break;
                    n += count;
                }
            } catch (IOException e) {
                // no op
            }
            if (n < blockSize) {
                status = STATUS_FORMAT_ERROR;
            }
        }
        return n;
    }

    protected int[] readColorTable(int ncolors) {
        int nbytes = 3 * ncolors;
        int[] tab = null;
        byte[] c = new byte[nbytes];
        int n = 0;
        try {
            n = in.read(c);
        } catch (IOException e) {
            // no op
        }
        if (n < nbytes) {
            status = STATUS_FORMAT_ERROR;
        } else {
            tab = new int[256]; // max size to avoid bounds checks
            int i = 0;
            int j = 0;
            while (i < ncolors) {
                int r = ((int) c[j++]) & 0xff;
                int g = ((int) c[j++]) & 0xff;
                int b = ((int) c[j++]) & 0xff;
                tab[i++] = 0xff000000 | (r << 16) | (g << 8) | b;
            }
        }
        return tab;
    }

    protected void readContents() {
        boolean done = false;
        while (!(done || err())) {
            int code = read();
            switch (code) {
                case 0x2C:
                    readImage();
                    break;
                case 0x21:
                    code = read();
                    switch (code) {
                        case 0xf9:
                            readGraphicControlExt();
                            break;
                        case 0xff:
                            readBlock();
                            String app = "";
                            for (int i = 0; i < 11; i++) {
                                app += (char) block[i];
                            }
                            if (app.equals("NETSCAPE2.0")) {
                                readNetscapeExt();
                            } else
                                skip();
                            break;
                        default:
                            skip();
                    }
                    break;
                case 0x3b:
                    done = true;
                    break;
                case 0x00:
                    break;
                default:
                    status = STATUS_FORMAT_ERROR;
            }
        }
    }

    protected void readGraphicControlExt() {
        read();
        int packed = read();
        dispose = (packed & 0x1c) >> 2;
        if (dispose == 0) {
            dispose = 1;
        }
        transparency = (packed & 1) != 0;
        delay = readShort() * 10;
        transIndex = read();
        read();
    }

    protected void readHeader() {
        String id = "";
        for (int i = 0; i < 6; i++) {
            id += (char) read();
        }
        if (!id.startsWith("GIF")) {
            status = STATUS_FORMAT_ERROR;
            return;
        }
        readLSD();
        if (gctFlag && !err()) {
            gct = readColorTable(gctSize);
            bgColor = gct[bgIndex];
        }
    }

    protected void readImage() {
        ix = readShort();
        iy = readShort();
        iw = readShort();
        ih = readShort();
        int packed = read();
        lctFlag = (packed & 0x80) != 0;
        interlace = (packed & 0x40) != 0;
        lctSize = 2 << (packed & 7);
        if (lctFlag) {
            lct = readColorTable(lctSize);
            act = lct;
        } else {
            act = gct;
            if (bgIndex == transIndex)
                bgColor = 0;
        }
        int save = 0;
        if (transparency) {
            save = act[transIndex];
            act[transIndex] = 0;
        }
        if (act == null) {
            status = STATUS_FORMAT_ERROR;
        }
        if (err()) return;
        decodeImageData();
        skip();
        if (err()) return;
        frameCount++;
        image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB_PRE);
        setPixels();
        frames.add(new GifFrame(image, delay));
        if (transparency) {
            act[transIndex] = save;
        }
        resetFrame();
    }

    protected void readLSD() {
        width = readShort();
        height = readShort();
        int packed = read();
        gctFlag = (packed & 0x80) != 0;
        gctSize = 2 << (packed & 7);
        bgIndex = read();
        pixelAspect = read();
    }

    protected void readNetscapeExt() {
        do {
            readBlock();
            if (block[0] == 1) {
                int b1 = ((int) block[1]) & 0xff;
                int b2 = ((int) block[2]) & 0xff;
                loopCount = (b2 << 8) | b1;
            }
        } while ((blockSize > 0) && !err());
    }

    protected int readShort() {
        return read() | (read() << 8);
    }

    protected void resetFrame() {
        lastDispose = dispose;
        lastRect = new Rectangle(ix, iy, iw, ih);
        lastImage = image;
        lastBgColor = bgColor;
        int dispose = 0;
        boolean transparency = false;
        int delay = 0;
        lct = null;
    }

    protected void skip() {
        do {
            readBlock();
        } while ((blockSize > 0) && !err());
    }
}