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

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

   JUCE is an open source library subject to commercial or open-source
   licensing.

   By using JUCE, you agree to the terms of both the JUCE 6 End-User License
   Agreement and JUCE Privacy Policy (both effective as of the 16th June 2020).

   End User License Agreement: www.juce.com/juce-6-licence
   Privacy Policy: www.juce.com/juce-privacy-policy

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

   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