#include <osg/Image>
#include <osg/Notify>
#include <osg/Geode>
#include <osg/GL>
#include <osg/Endian>

#include <osgDB/Registry>
#include <osgDB/FileUtils>
#include <osgDB/FileNameUtils>

#include <sstream>

using namespace osg;

extern "C"
{
    #include <zlib.h>
    #include <png.h>
}


/* Transparency parameters */
#define PNG_ALPHA     -2         /* Use alpha channel in PNG file, if there is one */
#define PNG_SOLID     -1         /* No transparency                                */
#define PNG_STENCIL    0         /* Sets alpha to 0 for r=g=b=0, 1 otherwise       */

typedef struct
{
    unsigned int Width;
    unsigned int Height;
    unsigned int Depth;
    unsigned int Alpha;
} pngInfo;

class PNGError
{
public:
    PNGError(const char* message)
    {
        _message = "PNG lib error : ";
        _message += message;
    }
    friend std::ostream& operator<<(std::ostream& stream, const PNGError& err) 
    {
        stream << err._message;
        return stream;
    }
private:
    std::string _message;
};

void user_error_fn(png_structp png_ptr, png_const_charp error_msg)
{
    throw PNGError(error_msg);
}

void user_warning_fn(png_structp png_ptr, png_const_charp warning_msg)
{
    osg::notify(osg::WARN) << "PNG lib warning : " << warning_msg << std::endl;
}

void png_read_istream(png_structp png_ptr, png_bytep data, png_size_t length)
{
    std::istream *stream = (std::istream*)png_get_io_ptr(png_ptr); //Get pointer to istream
    stream->read((char*)data,length); //Read requested amount of data
}

void png_write_ostream(png_structp png_ptr, png_bytep data, png_size_t length)
{
    std::ostream *stream = (std::ostream*)png_get_io_ptr(png_ptr); //Get pointer to ostream
    stream->write((char*)data,length); //Write requested amount of data
}

void png_flush_ostream(png_structp png_ptr)
{
    std::ostream *stream = (std::ostream*)png_get_io_ptr(png_ptr); //Get pointer to ostream
    stream->flush();
}

class ReaderWriterPNG : public osgDB::ReaderWriter
{
    public:
        ReaderWriterPNG()
        {
            supportsExtension("png","PNG Image format");
        }
        
        virtual const char* className() const { return "PNG Image Reader/Writer"; }

        WriteResult::WriteStatus writePngStream(std::ostream& fout, const osg::Image& img, int compression_level) const
        {
            png_structp png = NULL;
            png_infop   info = NULL;
            int color;
            png_bytep *rows = NULL;

            //Create write structure
            png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
            if(!png) return WriteResult::ERROR_IN_WRITING_FILE;

            //Create infr structure
            info = png_create_info_struct(png);
            if(!info) return WriteResult::ERROR_IN_WRITING_FILE;

            //Set custom write function so it will write to ostream
            png_set_write_fn(png,&fout,png_write_ostream,png_flush_ostream);

            //Set compression level
            png_set_compression_level(png, compression_level);

            switch(img.getPixelFormat()) {
                case(GL_LUMINANCE): color = PNG_COLOR_TYPE_GRAY; break;
                case(GL_ALPHA): color = PNG_COLOR_TYPE_GRAY; break; //Couldn't find a color type for pure alpha, using gray instead
                case(GL_LUMINANCE_ALPHA): color = PNG_COLOR_TYPE_GRAY_ALPHA ; break;
                case(GL_RGB): color = PNG_COLOR_TYPE_RGB; break;
                case(GL_RGBA): color = PNG_COLOR_TYPE_RGB_ALPHA; break;
                default: return WriteResult::ERROR_IN_WRITING_FILE; break;                
            }

            //Create row data
            rows = new png_bytep[img.t()];
            for(int i = 0; i < img.t(); ++i) {
                rows[i] = (png_bytep)img.data(0,img.t() - i - 1);
            }

            //Write header info
            png_set_IHDR(png, info, img.s(), img.t(),
                        8, color, PNG_INTERLACE_NONE,
                        PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

            png_write_info(png, info);

            //Write data
            png_write_image(png, rows);

            //End write
            png_write_end(png, NULL);

            //Cleanup
            png_destroy_write_struct(&png,&info);
            delete [] rows;

            return WriteResult::FILE_SAVED;
        }

        ReadResult readPNGStream(std::istream& fin) const
        {
            int trans = PNG_ALPHA;
            pngInfo pInfo;
            pngInfo *pinfo = &pInfo;

            unsigned char header[8];
            png_structp png;
            png_infop   info;
            png_infop   endinfo;
            png_bytep   data;    //, data2;
            png_bytep  *row_p;
            double  fileGamma;

            png_uint_32 width, height;
            int depth, color;

            png_uint_32 i;
            png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
 
            // Set custom error handlers
            png_set_error_fn(png, png_get_error_ptr(png), user_error_fn, user_warning_fn);

            try
            {

                info = png_create_info_struct(png);
                endinfo = png_create_info_struct(png);

                fin.read((char*)header,8);
                if (fin.gcount() == 8 && png_check_sig(header, 8))
                    png_set_read_fn(png,&fin,png_read_istream); //Use custom read function that will get data from istream
                else
                {
                    png_destroy_read_struct(&png, &info, &endinfo);
                    return ReadResult::FILE_NOT_HANDLED;
                }
                png_set_sig_bytes(png, 8);

                png_read_info(png, info);
                png_get_IHDR(png, info, &width, &height, &depth, &color, NULL, NULL, NULL);

                if (pinfo != NULL)
                {
                    pinfo->Width  = width;
                    pinfo->Height = height;
                    pinfo->Depth  = depth;
                }

                osg::notify(osg::INFO)<<"width="<<width<<" height="<<height<<" depth="<<depth<<std::endl;
                if ( color == PNG_COLOR_TYPE_RGB) osg::notify(osg::INFO) << "color == PNG_COLOR_TYPE_RGB "<<std::endl;
                if ( color == PNG_COLOR_TYPE_GRAY) osg::notify(osg::INFO) << "color == PNG_COLOR_TYPE_GRAY "<<std::endl;
                if ( color == PNG_COLOR_TYPE_GRAY_ALPHA) osg::notify(osg::INFO) << "color ==  PNG_COLOR_TYPE_GRAY_ALPHA"<<std::endl;

                // png default to big endian, so we'll need to swap bytes if on a little endian machine.
                if (depth>8 && getCpuByteOrder()==osg::LittleEndian)
                    png_set_swap(png);


                if (color == PNG_COLOR_TYPE_GRAY || color == PNG_COLOR_TYPE_GRAY_ALPHA)
                {
                    //png_set_gray_to_rgb(png);
                }

                if (color&PNG_COLOR_MASK_ALPHA && trans != PNG_ALPHA)
                {
                    png_set_strip_alpha(png);
                    color &= ~PNG_COLOR_MASK_ALPHA;
                }



                //    if (!(PalettedTextures && mipmap >= 0 && trans == PNG_SOLID))
                //if (color == PNG_COLOR_TYPE_PALETTE)
                //    png_set_expand(png);

                // In addition to expanding the palette, we also need to check
                // to expand greyscale and alpha images.  See libpng man page.
                if (color == PNG_COLOR_TYPE_PALETTE)
                    png_set_palette_to_rgb(png);
                if (color == PNG_COLOR_TYPE_GRAY && depth < 8)
                    png_set_gray_1_2_4_to_8(png);
                if (png_get_valid(png, info, PNG_INFO_tRNS))
                    png_set_tRNS_to_alpha(png);

                // Make sure that files of small depth are packed properly.
                if (depth < 8)
                    png_set_packing(png);


                /*--GAMMA--*/
                //    checkForGammaEnv();
                double screenGamma = 2.2 / 1.0;
                if (png_get_gAMA(png, info, &fileGamma))
                    png_set_gamma(png, screenGamma, fileGamma);
                else
                    png_set_gamma(png, screenGamma, 1.0/2.2);

                png_read_update_info(png, info);

                data = (png_bytep) new unsigned char [png_get_rowbytes(png, info)*height];
                row_p = new png_bytep [height];

                bool StandardOrientation = true;
                for (i = 0; i < height; i++)
                {
                    if (StandardOrientation)
                        row_p[height - 1 - i] = &data[png_get_rowbytes(png, info)*i];
                    else
                        row_p[i] = &data[png_get_rowbytes(png, info)*i];
                }

                png_read_image(png, row_p);
                delete [] row_p;
                png_read_end(png, endinfo);

                GLenum pixelFormat = 0;
                GLenum dataType = depth<=8?GL_UNSIGNED_BYTE:GL_UNSIGNED_SHORT;
                switch(color)
                {
                  case(PNG_SOLID): pixelFormat = GL_LUMINANCE; break;
                  case(PNG_ALPHA): pixelFormat = GL_ALPHA; break;
                  case(PNG_COLOR_TYPE_GRAY): pixelFormat =GL_LUMINANCE ; break;
                  case(PNG_COLOR_TYPE_GRAY_ALPHA): pixelFormat = GL_LUMINANCE_ALPHA; break;
                  case(PNG_COLOR_TYPE_RGB): pixelFormat = GL_RGB; break;
                  case(PNG_COLOR_TYPE_PALETTE): pixelFormat = GL_RGB; break;
                  case(PNG_COLOR_TYPE_RGB_ALPHA): pixelFormat = GL_RGBA; break;
                  default: break;                
                }

                // Some paletted images contain alpha information.  To be
                // able to give that back to the calling program, we need to
                // check the number of channels in the image.  However, the
                // call might not return correct information unless
                // png_read_end is called first.  See libpng man page.
                if (pixelFormat == GL_RGB && png_get_channels(png, info) == 4)
                    pixelFormat = GL_RGBA;

                int internalFormat = pixelFormat;

                png_destroy_read_struct(&png, &info, &endinfo);

                //    delete [] data;

                if (pixelFormat==0) 
                    return ReadResult::FILE_NOT_HANDLED;

                osg::Image* pOsgImage = new osg::Image();

                pOsgImage->setImage(width, height, 1,
                    internalFormat,
                    pixelFormat, 
                    dataType,
                    data,
                    osg::Image::USE_NEW_DELETE);

                return pOsgImage;
            }
            catch (PNGError& err)
            {
                osg::notify(osg::WARN) << err << std::endl;
                png_destroy_read_struct(&png, &info, &endinfo);
                return ReadResult::ERROR_IN_READING_FILE;
            }
        }

        int getCompressionLevel(const osgDB::ReaderWriter::Options *options) const
        {
            if(options) {
                std::istringstream iss(options->getOptionString());
                std::string opt;
                while (iss >> opt) {
                    if(opt=="PNG_COMPRESSION") {
                        int level;
                        iss >> level;
                        return level;
                    }
                }
            }

            return Z_DEFAULT_COMPRESSION;
        }

        virtual ReadResult readObject(std::istream& fin,const osgDB::ReaderWriter::Options* options =NULL) const
        {
            return readImage(fin, options);
        }

        virtual ReadResult readObject(const std::string& file, const osgDB::ReaderWriter::Options* options =NULL) const
        {
            return readImage(file, options);
        }

        virtual ReadResult readImage(std::istream& fin,const Options* =NULL) const
        {
            return readPNGStream(fin);
        }

        virtual ReadResult readImage(const std::string& file, const osgDB::ReaderWriter::Options* options) const
        {
            std::string ext = osgDB::getLowerCaseFileExtension(file);
            if (!acceptsExtension(ext)) return ReadResult::FILE_NOT_HANDLED;

            std::string fileName = osgDB::findDataFile( file, options );
            if (fileName.empty()) return ReadResult::FILE_NOT_FOUND;

            std::ifstream istream(fileName.c_str(), std::ios::in | std::ios::binary);
            if(!istream) return ReadResult::FILE_NOT_HANDLED;
            ReadResult rr = readPNGStream(istream);
            if(rr.validImage()) rr.getImage()->setFileName(file);
            return rr;
        }

        virtual WriteResult writeImage(const osg::Image& img,std::ostream& fout,const osgDB::ReaderWriter::Options *options) const
        {
            WriteResult::WriteStatus ws = writePngStream(fout,img,getCompressionLevel(options));
            return ws;
        }

        virtual WriteResult writeImage(const osg::Image &img,const std::string& fileName, const osgDB::ReaderWriter::Options *options) const
        {
            std::string ext = osgDB::getFileExtension(fileName);
            if (!acceptsExtension(ext)) return WriteResult::FILE_NOT_HANDLED;

            std::ofstream fout(fileName.c_str(), std::ios::out | std::ios::binary);
            if(!fout) return WriteResult::ERROR_IN_WRITING_FILE;

            return writeImage(img,fout,options);
        }
};

// now register with Registry to instantiate the above
// reader/writer.
REGISTER_OSGPLUGIN(png, ReaderWriterPNG)
