/*  Starshatter: The Open Source Project
    Copyright (c) 2021-2024, Starshatter: The Open Source Project Contributors
    Copyright (c) 2011-2012, Starshatter OpenSource Distribution Contributors
    Copyright (c) 1997-2006, Destroyer Studios LLC.

    AUTHOR:       John DiCamillo


    OVERVIEW
    ========
    BMP image file loader
*/


#include "PngImage.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "Types.h"

// Needed for compatibility with libpng 1.4++
#define png_infopp_NULL (png_infopp)NULL
#define png_voidp_NULL (png_voidp)NULL
#define int_p_NULL (int*)NULL

#include "png.h"

// +--------------------------------------------------------------------+

PngImage::PngImage()
: width(0), height(0), bpp(0), alpha_loaded(false), image(0)
{ }

PngImage::~PngImage()
{
    delete [] image;
}

// +--------------------------------------------------------------------+

int PngImage::Load(char *filename)
{
    int   status = PNG_INVALID;
    FILE* f;

    fopen_s(&f, filename,"rb");
    if (f == NULL)
    return PNG_NOFILE;

    BYTE buf[12];
    fread(buf, 8, 1, f);
    fseek(f, 0, SEEK_SET);

    if (png_sig_cmp(buf, (png_size_t)0, 8))
    return PNG_INVALID;

    png_structp png_ptr;
    png_infop   info_ptr;

    /* Create and initialize the png_struct with the desired error handler
    * functions.  If you want to use the default stderr and longjump method,
    * you can supply NULL for the last three parameters.  We also supply the
    * the compiler header file version, so that we know if the application
    * was compiled with a compatible version of the library.  REQUIRED
    */
    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);

    if (!png_ptr) {
        return PNG_NOMEM;
    }

    /* Allocate/initialize the memory for image information.  REQUIRED. */
    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL);
        return PNG_NOMEM;
    }

    png_init_io(png_ptr, f);
    png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, png_voidp_NULL);

    status = CreateImage(png_ptr, info_ptr);

    png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);

    fclose(f);
    return status;
}

// +--------------------------------------------------------------------+

struct PngIOStruct
{
    BYTE* fp;
    BYTE* buffer;
    DWORD length;
};

static void png_user_read_data(png_structp read_ptr, png_bytep data, png_size_t length)
{
    PngIOStruct* read_io_ptr = (PngIOStruct*) png_get_io_ptr(read_ptr);

    if (!read_io_ptr)
    return;

    if (read_io_ptr->fp + length < read_io_ptr->buffer + read_io_ptr->length) {
        memcpy(data, read_io_ptr->fp, length);
        read_io_ptr->fp += length;
    }
}

static void png_user_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
{
}

static void png_user_flush_data(png_structp png_ptr)
{
}

int PngImage::LoadBuffer(unsigned char* buf, int len)
{
    int status = PNG_INVALID;
    PngIOStruct io;

    if (buf == NULL)
    return PNG_NOFILE;

    if (png_sig_cmp(buf, (png_size_t)0, 8))
    return PNG_INVALID;

    io.buffer = buf;
    io.fp     = buf;
    io.length = len;

    png_structp png_ptr;
    png_infop   info_ptr;

    /* Create and initialize the png_struct with the desired error handler
    * functions.  If you want to use the default stderr and longjump method,
    * you can supply NULL for the last three parameters.  We also supply the
    * the compiler header file version, so that we know if the application
    * was compiled with a compatible version of the library.  REQUIRED
    */
    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);

    if (!png_ptr) {
        return PNG_NOMEM;
    }

    /* Allocate/initialize the memory for image information.  REQUIRED. */
    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL);
        return PNG_NOMEM;
    }

    png_set_read_fn(png_ptr, (void *) (&io), png_user_read_data);
    png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, png_voidp_NULL);

    status = CreateImage(png_ptr, info_ptr);

    png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);

    return status;
}

// +--------------------------------------------------------------------+

int
PngImage::CreateImage(png_structp png_ptr, png_infop info_ptr)
{
    int status = PNG_INVALID;

    width  = png_get_image_width(png_ptr, info_ptr);
    height = png_get_image_height(png_ptr, info_ptr);
    bpp    = png_get_bit_depth(png_ptr, info_ptr);

    if (width > 0 && width < 32768 && height > 0 && height < 32768) {
        // true-color:
        if (bpp >= 24) {
            status = PNG_OK;

            if ( png_get_channels(png_ptr, info_ptr) == 4)
            alpha_loaded = true;

            image = new DWORD[width*height];
            BYTE** rows = png_get_rows(png_ptr, info_ptr);

            for (DWORD row = 0; row < height; row++) {
                BYTE* p = rows[row];

                for (DWORD col = 0; col < width; col++) {
                    DWORD red   = *p++;
                    DWORD green = *p++;
                    DWORD blue  = *p++;
                    DWORD alpha = 0xff;

                    if ( png_get_channels(png_ptr, info_ptr) == 4)
                    alpha = *p++;

                    image[row*width+col] = (alpha << 24) | (red << 16) | (green << 8) | blue;
                }
            }
        }

        // paletted:
        else if (bpp == 8) {
            DWORD pal[256];

            png_bytep trans_alpha; int num_trans; png_color_16p trans_color;
            png_colorp palette;
            int num_palette;

            png_get_tRNS(png_ptr, info_ptr, &trans_alpha, &num_trans, &trans_color);
            png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette);

            if (num_trans > 0)
            alpha_loaded = true;

            for (int i = 0; i < 256; i++) {
                if (i < num_palette) {
                    DWORD red   = palette[i].red;
                    DWORD green = palette[i].green;
                    DWORD blue  = palette[i].blue;
                    DWORD alpha = 0xff;

                    if (i < num_trans)
                    alpha = trans_alpha[i];

                    pal[i] = (alpha << 24) | (red << 16) | (green << 8) | blue;
                }

                else {
                    pal[i] = 0;
                }
            }

            image = new DWORD[width*height];
            BYTE** rows = png_get_rows(png_ptr, info_ptr);

            for (DWORD row = 0; row < height; row++) {
                BYTE* p = rows[row];

                for (DWORD col = 0; col < width; col++) {
                    BYTE index = *p++;
                    image[row*width+col] = pal[index];
                }
            }
        }
    }

    return status;
}