/*
 * texture.c
 *
 * Handle textures
 *
 * (c) 2008 Thomas White <taw27@cam.ac.uk>
 *
 *  thrust3d - a silly game
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <png.h>
#include <stdlib.h>
#include <glew.h>
#include <glu.h>

#include "render.h"

void texture_load(RenderContext *ctx, char *name) {

	FILE *fh;
	png_bytep header;
	png_structp png_ptr;
	png_infop info_ptr;
	png_infop end_info;
	unsigned int width;
	unsigned int height;
	unsigned int bit_depth;
	unsigned int channels;
	png_bytep *row_pointers;
	unsigned int x;
	unsigned int y;
	char tmp[128];
	uint8_t *texels;
	
	/* Open file */
	snprintf(tmp, 127, "%s/textures/%s.png", DATADIR, name);
	fh = fopen(tmp, "rb");
	if ( !fh ) {
		fprintf(stderr, "Couldn't open texture file '%s'\n", tmp);
		return ;
	}

	/* Check it's actually a PNG file */
	header = malloc(8);
	fread(header, 1, 8, fh);
	if ( png_sig_cmp(header, 0, 8)) {
		fprintf(stderr, "Texture file '%s' is not a PNG file.\n", tmp);
		free(header);
		fclose(fh);
		return;
	}
	free(header);
	
	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	if ( !png_ptr ) {
		fprintf(stderr, "Couldn't create PNG read structure.\n");
		fclose(fh);
		return ;
	}

	info_ptr = png_create_info_struct(png_ptr);
	if ( !info_ptr ) {
		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
		fprintf(stderr, "Couldn't create PNG info structure.\n");
		fclose(fh);
		return;
	}

	end_info = png_create_info_struct(png_ptr);
	if ( !end_info ) {
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
		printf("Couldn't create PNG end info structure.\n");
		fclose(fh);
		return;
	}
	
	if ( setjmp(png_jmpbuf(png_ptr)) ) {
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		fclose(fh);
		fprintf(stderr, "PNG read failed.\n");
		return;
	}

	png_init_io(png_ptr, fh);
	png_set_sig_bytes(png_ptr, 8);
	
	/* Read! */
	png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);

	width = png_get_image_width(png_ptr, info_ptr);
	height = png_get_image_height(png_ptr, info_ptr);
	bit_depth = png_get_bit_depth(png_ptr, info_ptr);
	channels = png_get_channels(png_ptr, info_ptr);
	if ( bit_depth != 8 ) {
		fprintf(stderr, "Texture image '%s' isn't 8 bits per channel per pixel.\n", tmp);
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		fclose(fh);
		return;
	}
	if ( channels != 4 ) {
		fprintf(stderr, "Texture image '%s' doesn't have 4 channels.\n", tmp);
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		fclose(fh);
		return;
	}
	
	/* Get image data */
	row_pointers = png_get_rows(png_ptr, info_ptr);
	
	texels = malloc(4*width*height);
	for ( y=0; y<height; y++ ) {
		for ( x=0; x<width; x++ ) {
		
			unsigned int r, g, b, a;

			r = row_pointers[y][(channels*x)+0];
			g = row_pointers[y][(channels*x)+1];
			b = row_pointers[y][(channels*x)+2];
			a = row_pointers[y][(channels*x)+3];
			
			texels[4*(x + width*(height-1-y)) + 0] = r;
			texels[4*(x + width*(height-1-y)) + 1] = g;
			texels[4*(x + width*(height-1-y)) + 2] = b;
			texels[4*(x + width*(height-1-y)) + 3] = a;
			
		}
	}
	
	glGenTextures(1, &(ctx->textures[ctx->num_textures].texname));
	glBindTexture(GL_TEXTURE_2D, ctx->textures[ctx->num_textures].texname);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
	//glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, texels);
	gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGBA8, width, height, GL_RGBA, GL_UNSIGNED_BYTE, texels);
	free(texels);
	ctx->textures[ctx->num_textures].name = name;
	ctx->num_textures++;
	
	png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
	fclose(fh);

}

Texture *texture_lookup(RenderContext *ctx, const char *name) {
	
	int i, found;
	
	found = 0;
	for ( i=0; i<ctx->num_textures; i++ ) {
		if ( strcmp(ctx->textures[i].name, name) == 0 ) {
			found = 1;
			break;
		}
	}
	
	if ( found == 0 ) {
		return NULL;
	}
	
	return &(ctx->textures[i]);
	
}

void texture_free_all(RenderContext *ctx) {
	
	int i;
	
	for ( i=0; i<ctx->num_textures; i++ ) {
		glDeleteTextures(1, &(ctx->textures[ctx->num_textures].texname));
	}
	
}