/*
  ==============================================================================

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

#if (JUCE_MAC || JUCE_IOS) && USE_COREGRAPHICS_RENDERING && JUCE_USE_COREIMAGE_LOADER
 Image juce_loadWithCoreImage (InputStream& input);
#else

//==============================================================================
class GIFLoader
{
public:
    GIFLoader (InputStream& in)
        : input (in),
          dataBlockIsZero (false), fresh (false), finished (false),
          currentBit (0), lastBit (0), lastByteIndex (0),
          codeSize (0), setCodeSize (0), maxCode (0), maxCodeSize (0),
          firstcode (0), oldcode (0), clearCode (0), endCode (0)
    {
        int imageWidth, imageHeight;
        if (! getSizeFromHeader (imageWidth, imageHeight))
            return;

        uint8 buf [16];
        if (in.read (buf, 3) != 3)
            return;

        int numColours = 2 << (buf[0] & 7);
        int transparent = -1;

        if ((buf[0] & 0x80) != 0)
            readPalette (numColours);

        for (;;)
        {
            if (input.read (buf, 1) != 1 || buf[0] == ';')
                break;

            if (buf[0] == '!')
            {
                if (readExtension (transparent))
                    continue;

                break;
            }

            if (buf[0] != ',')
                continue;

            if (input.read (buf, 9) == 9)
            {
                imageWidth  = (int) ByteOrder::littleEndianShort (buf + 4);
                imageHeight = (int) ByteOrder::littleEndianShort (buf + 6);

                numColours = 2 << (buf[8] & 7);

                if ((buf[8] & 0x80) != 0)
                    if (! readPalette (numColours))
                        break;

                image = Image (transparent >= 0 ? Image::ARGB : Image::RGB,
                               imageWidth, imageHeight, transparent >= 0);

                image.getProperties()->set ("originalImageHadAlpha", transparent >= 0);

                readImage ((buf[8] & 0x40) != 0, transparent);
            }

            break;
        }
    }

    Image image;

private:
    InputStream& input;
    uint8 buffer [260];
    PixelARGB palette [256];
    bool dataBlockIsZero, fresh, finished;
    int currentBit, lastBit, lastByteIndex;
    int codeSize, setCodeSize;
    int maxCode, maxCodeSize;
    int firstcode, oldcode;
    int clearCode, endCode;
    enum { maxGifCode = 1 << 12 };
    int table [2] [maxGifCode];
    int stack [2 * maxGifCode];
    int* sp;

    bool getSizeFromHeader (int& w, int& h)
    {
        char b[6];

        if (input.read (b, 6) == 6
             && (strncmp ("GIF87a", b, 6) == 0
                  || strncmp ("GIF89a", b, 6) == 0))
        {
            if (input.read (b, 4) == 4)
            {
                w = (int) ByteOrder::littleEndianShort (b);
                h = (int) ByteOrder::littleEndianShort (b + 2);
                return w > 0 && h > 0;
            }
        }

        return false;
    }

    bool readPalette (const int numCols)
    {
        for (int i = 0; i < numCols; ++i)
        {
            uint8 rgb[4];
            input.read (rgb, 3);

            palette[i].setARGB (0xff, rgb[0], rgb[1], rgb[2]);
            palette[i].premultiply();
        }

        return true;
    }

    int readDataBlock (uint8* const dest)
    {
        uint8 n;
        if (input.read (&n, 1) == 1)
        {
            dataBlockIsZero = (n == 0);

            if (dataBlockIsZero || (input.read (dest, n) == n))
                return n;
        }

        return -1;
    }

    int readExtension (int& transparent)
    {
        uint8 type;
        if (input.read (&type, 1) != 1)
            return false;

        uint8 b [260];
        int n = 0;

        if (type == 0xf9)
        {
            n = readDataBlock (b);
            if (n < 0)
                return 1;

            if ((b[0] & 1) != 0)
                transparent = b[3];
        }

        do
        {
            n = readDataBlock (b);
        }
        while (n > 0);

        return n >= 0;
    }

    void clearTable()
    {
        int i;
        for (i = 0; i < clearCode; ++i)
        {
            table[0][i] = 0;
            table[1][i] = i;
        }

        for (; i < maxGifCode; ++i)
        {
            table[0][i] = 0;
            table[1][i] = 0;
        }
    }

    void initialise (const int inputCodeSize)
    {
        setCodeSize = inputCodeSize;
        codeSize = setCodeSize + 1;
        clearCode = 1 << setCodeSize;
        endCode = clearCode + 1;
        maxCodeSize = 2 * clearCode;
        maxCode = clearCode + 2;

        getCode (0, true);

        fresh = true;
        clearTable();
        sp = stack;
    }

    int readLZWByte()
    {
        if (fresh)
        {
            fresh = false;

            for (;;)
            {
                firstcode = oldcode = getCode (codeSize, false);

                if (firstcode != clearCode)
                    return firstcode;
            }
        }

        if (sp > stack)
            return *--sp;

        int code;

        while ((code = getCode (codeSize, false)) >= 0)
        {
            if (code == clearCode)
            {
                clearTable();
                codeSize = setCodeSize + 1;
                maxCodeSize = 2 * clearCode;
                maxCode = clearCode + 2;
                sp = stack;
                firstcode = oldcode = getCode (codeSize, false);
                return firstcode;
            }
            else if (code == endCode)
            {
                if (dataBlockIsZero)
                    return -2;

                uint8 buf [260];
                int n;

                while ((n = readDataBlock (buf)) > 0)
                {}

                if (n != 0)
                    return -2;
            }

            const int incode = code;

            if (code >= maxCode)
            {
                *sp++ = firstcode;
                code = oldcode;
            }

            while (code >= clearCode)
            {
                *sp++ = table[1][code];
                if (code == table[0][code])
                    return -2;

                code = table[0][code];
            }

            *sp++ = firstcode = table[1][code];

            if ((code = maxCode) < maxGifCode)
            {
                table[0][code] = oldcode;
                table[1][code] = firstcode;
                ++maxCode;

                if (maxCode >= maxCodeSize && maxCodeSize < maxGifCode)
                {
                    maxCodeSize <<= 1;
                    ++codeSize;
                }
            }

            oldcode = incode;

            if (sp > stack)
                return *--sp;
        }

        return code;
    }

    int getCode (const int codeSize_, const bool shouldInitialise)
    {
        if (shouldInitialise)
        {
            currentBit = 0;
            lastBit = 0;
            finished = false;
            return 0;
        }

        if ((currentBit + codeSize_) >= lastBit)
        {
            if (finished)
                return -1;

            buffer[0] = buffer [lastByteIndex - 2];
            buffer[1] = buffer [lastByteIndex - 1];

            const int n = readDataBlock (buffer + 2);

            if (n == 0)
                finished = true;

            lastByteIndex = 2 + n;
            currentBit = (currentBit - lastBit) + 16;
            lastBit = (2 + n) * 8 ;
        }

        int result = 0;
        int i = currentBit;

        for (int j = 0; j < codeSize_; ++j)
        {
            result |= ((buffer[i >> 3] & (1 << (i & 7))) != 0) << j;
            ++i;
        }

        currentBit += codeSize_;
        return result;
    }

    bool readImage (const int interlace, const int transparent)
    {
        uint8 c;
        if (input.read (&c, 1) != 1)
            return false;

        initialise (c);

        if (transparent >= 0)
            palette [transparent].setARGB (0, 0, 0, 0);

        int xpos = 0, ypos = 0, yStep = 8, pass = 0;

        const Image::BitmapData destData (image, Image::BitmapData::writeOnly);
        uint8* p = destData.getPixelPointer (0, 0);
        const bool hasAlpha = image.hasAlphaChannel();

        for (;;)
        {
            const int index = readLZWByte();
            if (index < 0)
                break;

            if (hasAlpha)
                ((PixelARGB*) p)->set (palette [index]);
            else
                ((PixelRGB*)  p)->set (palette [index]);

            p += destData.pixelStride;

            if (++xpos == destData.width)
            {
                xpos = 0;

                if (interlace)
                {
                    ypos += yStep;

                    while (ypos >= destData.height)
                    {
                        switch (++pass)
                        {
                            case 1:     ypos = 4; yStep = 8; break;
                            case 2:     ypos = 2; yStep = 4; break;
                            case 3:     ypos = 1; yStep = 2; break;
                            default:    return true;
                        }
                    }
                }
                else
                {
                    if (++ypos >= destData.height)
                        break;
                }

                p = destData.getPixelPointer (xpos, ypos);
            }
        }

        return true;
    }

    JUCE_DECLARE_NON_COPYABLE (GIFLoader)
};

#endif

//==============================================================================
GIFImageFormat::GIFImageFormat() {}
GIFImageFormat::~GIFImageFormat() {}

String GIFImageFormat::getFormatName()                  { return "GIF"; }
bool GIFImageFormat::usesFileExtension (const File& f)  { return f.hasFileExtension ("gif"); }

bool GIFImageFormat::canUnderstand (InputStream& in)
{
    char header [4];

    return (in.read (header, sizeof (header)) == (int) sizeof (header))
             && header[0] == 'G'
             && header[1] == 'I'
             && header[2] == 'F';
}

Image GIFImageFormat::decodeImage (InputStream& in)
{
   #if (JUCE_MAC || JUCE_IOS) && USE_COREGRAPHICS_RENDERING && JUCE_USE_COREIMAGE_LOADER
    return juce_loadWithCoreImage (in);
   #else
    const std::unique_ptr<GIFLoader> loader (new GIFLoader (in));
    return loader->image;
   #endif
}

bool GIFImageFormat::writeImageToStream (const Image& /*sourceImage*/, OutputStream& /*destStream*/)
{
    jassertfalse; // writing isn't implemented for GIFs!
    return false;
}

} // namespace juce