#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "glm.h"
#include "glmint.h"

#ifdef HAVE_LIBPNG
/*
* Based heavily on example code in libpng. Some bugs fixed though.
*/

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

#include <png.h>

#define ERR_NO_ERROR     0
#define ERR_OPEN         1
#define ERR_MEM          2
#define ERR_PNGLIB       3
#define ERR_OPEN_WRITE   4
#define ERR_PNGLIB_WRITE 5
#define ERR_MEM_WRITE    6

static int pngerror = ERR_NO_ERROR;

/* my setjmp buffer */
static jmp_buf setjmp_buffer;

/* called my libpng */
static void 
warn_callback(png_structp ps, png_const_charp pc)
{
	fprintf(stderr,"PNG warn: %s\n", pc);
	/*FIXME: notify? */
}

static void 
err_callback(png_structp ps, png_const_charp pc)
{
	fprintf(stderr,"PNG error: %s\n", pc);

	/* FIXME: store error message? */
	longjmp(setjmp_buffer, 1);
}

GLubyte* 
glmReadPNG(const char* filename, GLboolean alpha, int* width_ret, int* height_ret, int* type_ret)
{
	png_structp png_ptr;
	png_infop info_ptr;
	png_uint_32 width, height;

	int bit_depth, color_type, interlace_type;
	FILE *fp;
	unsigned char *buffer;
	int y, bytes_per_row;
	int channels;
	int format;
	png_bytepp row_pointers;

	if ((fp = fopen(filename, "rb")) == NULL) {
		pngerror = ERR_OPEN;
		return NULL;
	}

	/* 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,
	(void *)user_error_ptr, user_error_fn, user_warning_fn);*/

	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
		NULL, err_callback, warn_callback);

	if (png_ptr == NULL) {
		pngerror = ERR_MEM;
		fclose(fp);
		return 0;
	}

	/* Allocate/initialize the memory for image information.  REQUIRED. */
	info_ptr = png_create_info_struct(png_ptr);
	if (info_ptr == NULL) {
		pngerror = ERR_MEM;
		fclose(fp);
		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
		return 0;
	}

	/* Set error handling if you are using the setjmp/longjmp method (this is
	* the normal method of doing things with libpng).  REQUIRED unless you
	* set up your own error handlers in the png_create_read_struct() earlier.
	*/

	buffer = NULL;

	if (setjmp(setjmp_buffer)) {
		pngerror = ERR_PNGLIB;
		/* Free all of the memory associated with the png_ptr and info_ptr */
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
		fclose(fp);
		/* If we get here, we had a problem reading the file */

		if (buffer) free(buffer);
		return NULL;
	}

	/* Set up the input control if you are using standard C streams */
	png_init_io(png_ptr, fp);

	/* The call to png_read_info() gives us all of the information from the
	* PNG file before the first IDAT (image data chunk).  REQUIRED
	*/
	png_read_info(png_ptr, info_ptr);

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

	/**** Set up the data transformations you want.  Note that these are all
	**** optional.  Only call them if you want/need them.  Many of the
	**** transformations only work on specific types of images, and many
	**** are mutually exclusive.
	****/

	/* tell libpng to strip 16 bit/color files down to 8 bits/color */
	png_set_strip_16(png_ptr);

	/* strip alpha bytes from the input data without combining with th
	* background (not recommended) */
	/* png_set_strip_alpha(png_ptr); */

	/* extract multiple pixels with bit depths of 1, 2, and 4 from a single
	* byte into separate bytes (useful for paletted and grayscale images).
	*/
	/* png_set_packing(png_ptr); */

	/* change the order of packed pixels to least significant bit first
	* (not useful if you are using png_set_packing). */
	/* png_set_packswap(png_ptr); */

	/* expand paletted colors into true RGB triplets */
	if (color_type == PNG_COLOR_TYPE_PALETTE)
		png_set_expand(png_ptr);

	/* expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
	if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
		png_set_expand(png_ptr);

	/* expand paletted or RGB images with transparency to full alpha channels
	* so the data will be available as RGBA quartets */
	if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
		png_set_expand(png_ptr);

	/* Add filler (or alpha) byte (before/after each RGB triplet) */
	/* png_set_filler(png_ptr, 0xff, PNG_FILLER_AFTER); */

	png_read_update_info(png_ptr, info_ptr);

	channels = png_get_channels(png_ptr, info_ptr);

	/* allocate the memory to hold the image using the fields of info_ptr. */

	bytes_per_row = png_get_rowbytes(png_ptr, info_ptr);


	buffer = (unsigned char*) malloc(bytes_per_row*height);

	format = channels;

	row_pointers = (png_bytepp) malloc(height*sizeof(png_bytep));
	for (y = 0; y < height; y++) {
		row_pointers[height-y-1] = buffer + y*bytes_per_row;
	}

	png_read_image(png_ptr, row_pointers);
	png_read_end(png_ptr, info_ptr);

	free(row_pointers);

	/* clean up after the read, and free any memory allocated - REQUIRED */
	png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);

	/* close the file */
	fclose(fp);

	/* that's it */
	if (buffer) {
		*width_ret = width;
		*height_ret = height;
		switch(format) {
	case 1:
		*type_ret = GL_LUMINANCE;
		break;
	case 2:
		*type_ret = GL_LUMINANCE_ALPHA;
		break;
	case 3:
		*type_ret = GL_RGB;
		break;
	case 4:
		*type_ret = GL_RGBA;
		break;
		}
		pngerror = ERR_NO_ERROR;
	}
	else {
		pngerror = ERR_MEM;
	}
	return buffer;
}

#endif
