#include <stdio.h>
#include <stdlib.h>
#include "txd.h"

void correctindices(int width, int height, char *indices)
{
	int i;
	unsigned char temp;
	char map[4] = {0, 16, 8, 24};
	for (i = 0; i < width*height; i++) {
		temp = indices[i];
		indices[i] = (temp & ~24) | map[(temp & 24) >> 3];
	}
}

void swizzle8(unsigned char *indices, unsigned char *rawindices,
		int width, int height)
{
	int y, x;
	for (y = 0; y < height; y++)
		for (x = 0; x < width; x++) {
			int block_loc = (y&(~0x0F))*width + (x&(~0x0F))*2;
			unsigned int swap_sel = (((y+2)>>2)&0x01)*4;
			int ypos = (((y&(~3))>>1) + (y&1))&0x07;
			int column_loc = ypos*width*2 + ((x+swap_sel)&0x07)*4;
			int byte_sum = ((y>>1)&1) + ((x>>2)&2);

			int swizzled = block_loc + column_loc + byte_sum;
			indices[swizzled] = rawindices[y*width+x];	
		}
}

unsigned char *ReadTga(unsigned char colors[][4], unsigned char *indices,
		image *img, FILE *tga)
{
	int i;
	unsigned short pallength;
	unsigned short txdpallength;
	unsigned char tempc;
	unsigned short temps;
	unsigned char bpp;
	unsigned short width;
	unsigned short height;
	int hasalpha;
	unsigned char *rawindices;

	/* Id length */
	fseek(tga, 1, 0);
	/* Has palette */
	fread(&tempc, 1, 1, tga);
	if (tempc != 1) {
		fprintf(stderr, "Only indexed pictures supported\n");
		exit(4);
	}
	/* picture type (1 = indexed) */
	fread(&tempc, 1, 1, tga);
	if (tempc != 1) {
		fprintf(stderr, "Only indexed pictures supported\n");
		exit(4);
	}
	/* begin of palette */
	fseek(tga, 2, SEEK_CUR);
	/* length of palette */
	fread(&pallength, 2, 1, tga);
	/* bits per palette entry */
	fread(&tempc, 1, 1, tga);
	if (tempc == 0x18)
		hasalpha = 0;	
	else
		hasalpha = 1;
	/* X origin */
	fread(&temps, 2, 1, tga);
	if (temps != 0) {
		fprintf(stderr, "X origin must be 0\n");
		exit(4);
	}
	/* Y origin */
	fread(&temps, 2, 1, tga);
	if (temps != 0) {
		fprintf(stderr, "Y origin must be 0\n");
		exit(4);
	}
	/* Width */
	fread(&width, 2, 1, tga);
	/* Height */
	fread(&height, 2, 1, tga);
	/* bits per pixel */
	fread(&bpp, 1, 1, tga);
	if (bpp != 8) {
		fprintf(stderr, "Only 8 bit pictures supported\n");
		exit(4);
	}
	/* attributes */
	fread(&tempc, 1, 1, tga);
	if ((tempc & 0x20) == 0) {
		fprintf(stderr, "Origin must be at upper left\n");
		exit(4);
	}

	/* Set pallength either as 16 or 256 */
	if (pallength > 16 && pallength <= 256)
		txdpallength = 256;
	else if (pallength <= 16)
		txdpallength = 16;
	else {
		fprintf(stderr, "Unsupported palette\n");
		exit(4);
	}

	printf("%lX\n", ftell(tga));
	for (i = 0; i < pallength; i++) {
		colors[i][2] = getc(tga);
		colors[i][1] = getc(tga);
		colors[i][0] = getc(tga);
		if (hasalpha)
			colors[i][3] = getc(tga) / 2 + 1;
		else
			colors[i][3] = 0x80;
	}
	for (; i < txdpallength; i++) {
		colors[i][2] = 0;
		colors[i][1] = 0;
		colors[i][0] = 0;
		colors[i][3] = 0x80;
	}

	indices = (unsigned char *) malloc(width*height);
	rawindices = (unsigned char *) malloc(width*height);

	fread(rawindices, 1, width*height, tga);
	correctindices(width, height, rawindices);
	swizzle8(indices, rawindices, width, height);
	free(rawindices);

	return indices;
}