#include "pngfile.h"

#pragma comment(lib,"libpng.lib")

FILE *png_stream;
#define png_ptr_stream png_stream//((FILE *)png_ptr->io_ptr)

void _flushpngfile(png_structp png_ptr)
{
    fflush(png_ptr_stream);
}

void _readpngfile(png_structp png_ptr,unsigned char *buf,int size)
{
    if (fread(buf,1,size,png_ptr_stream)==0)
        printf("Error reading stream for PNG file!\n");
}

void _writepngfile(png_structp png_ptr,unsigned char *buf,int size)
{
    if (fwrite(buf,1,size,png_ptr_stream)==0)
        printf("Error writing stream for PNG file!\n");
}

Pixelmap *LoadPNG(char *loadtarget)
{
    int bit_depth,color_type,interlace_type,compression_type,filter_method;
    char *filename;

    int x,y;
    char buf[8];
    char **rows;

    png_structp png_ptr;
    png_infop info_ptr;
    png_uint_32 width,height;

    //FILE *png_stream;
    Pixelmap *pixmap=NULL;

    if (!loadtarget) return 0;
    filename=loadtarget;

    //printf("Loading PNG image: \"%s\"\n",filename);

    if (!(png_stream=fopen(filename,"rb")))
    {
        return NULL;
    }

    if (fread(buf,1,8,png_stream)!=8) return 0;

    if (png_sig_cmp((unsigned char *)buf,0,8)!=0)
    {
        fclose(png_stream);
        return NULL;
    }

    png_ptr=png_create_read_struct(PNG_LIBPNG_VER_STRING,NULL,NULL,NULL);
    if (!png_ptr)
    {
        fclose(png_stream);
        return NULL;
    }
    png_ptr->io_ptr=png_stream;

    info_ptr=png_create_info_struct(png_ptr);

    if (!info_ptr)
    {
        fclose(png_stream);
        png_destroy_read_struct(&png_ptr,NULL,NULL);
        return 0;
    }

    png_set_sig_bytes(png_ptr,8);
    png_set_read_fn(png_ptr,NULL,(png_rw_ptr)_readpngfile);
    png_read_png(png_ptr,info_ptr,PNG_TRANSFORM_EXPAND|PNG_TRANSFORM_STRIP_16,0);

    png_get_IHDR(
        png_ptr,info_ptr,
        &width,&height,&bit_depth,
        &color_type,&interlace_type,
        &compression_type,
        &filter_method);

    if (bit_depth=8)
    {
        PixelFormat pixelformat=PixelsNone;
        int usestdcreator=0;
        switch (color_type)
        {
        case PNG_COLOR_TYPE_GRAY:
            pixelformat=PixelsI8;
            usestdcreator=1;
            break;
        case PNG_COLOR_TYPE_RGB:
            pixelformat=PixelsR8G8B8;
            usestdcreator=1;
            break;
        case PNG_COLOR_TYPE_RGBA:
            pixelformat=PixelsR8G8B8A8;
            usestdcreator=1;
            break;
        case PNG_COLOR_TYPE_GRAY_ALPHA:
            pixmap=new Pixelmap((int)width,(int)height,PixelsR8G8B8A8);
            rows=(char **)png_get_rows(png_ptr,info_ptr);
            for (y=0; y<(int)height; y++)
            {
                char *src=rows[y];
                char *dst=pixmap->PixPtr(0,y);
                for (x=0; x<(int)width; x++)
                {
                    char a=src[0];
                    char i=src[1];
                    dst[0]=i;
                    dst[1]=i;
                    dst[2]=i;
                    dst[3]=a;
                    src+=2;
                    dst+=4;
                }
            }
            break;
        }

        if (usestdcreator)
        {
            pixmap=new Pixelmap((int)width,(int)height,pixelformat);
            rows=(char **)png_get_rows(png_ptr,info_ptr);
            for (y=0; y<(int)height; y++)
            {
                if (!PixelBufferCopy((unsigned char *)rows[y],(unsigned char *)pixmap->PixPtr(0,y),pixelformat,width))
                {
                    png_destroy_read_struct(&png_ptr,&info_ptr,NULL);
                    fclose(png_stream);
                    delete pixmap;
                    return NULL;
                }
            }
        }
    }

    png_destroy_read_struct(&png_ptr,&info_ptr,NULL);
    fclose(png_stream);

    return pixmap;
}