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

#include "render.h"

int main(int argc, char** argv) {
	FILE* outfile, * infile;
	char bmp_magic[2];
	int ret = 0;
	unsigned bmp_offset;
	int bmp_w, bmp_h, x, y, i, s;
	unsigned short bmp_bits;
	char magic[4] = { 'I', 'M', 'A', 'G' };
	Colour pixel;
	unsigned char t;

	if (argc < 3) {
		fprintf(stderr, "Usage: %s infile outfile.\n", argv[0]);
		return 1;
	}

	infile = fopen(argv[1], "rb");
	if (!infile) {
		fprintf(stderr, "Failed to open %s.\n", argv[1]);
		return 2;
	}

	outfile = fopen(argv[2], "wb");
	if (!outfile) {
		fprintf(stderr, "Failed to open %s.\n", argv[2]);
		fclose(infile);
		return 2;
	}

	fread(bmp_magic, 2, 1, infile);
	if (bmp_magic[0] != 'B' || bmp_magic[1] != 'M') {
		ret = 3;
		fprintf(stderr, "Not a valid bitmap file.\n");
		goto end;
	}
	
	fseek(infile, 10, SEEK_SET);
	fread(&bmp_offset, 4, 1, infile);

	fseek(infile, 18, SEEK_SET);
	fread(&bmp_w,    4, 1, infile);
	fread(&bmp_h,    4, 1, infile);
	fseek(infile, 28, SEEK_SET);
	fread(&bmp_bits, 2, 1, infile);

	if (bmp_bits != 32) {
		ret = 4;
		fprintf(stderr, "Bitmap must have 32 bit pixels. %d\n", bmp_bits);
		goto end;
	}

	fseek(infile, bmp_offset, SEEK_SET);

	fwrite(magic,  1, 4, outfile);
	fwrite(&bmp_w, 1, 4, outfile);
	fwrite(&bmp_h, 1, 4, outfile);

	s = bmp_w * bmp_h;
	/* Allocate space. */
	for (i = 0; i < s; i++) {
		fwrite(&pixel, 1, 4, outfile);
	}

	fseek(outfile, 12, SEEK_SET);
	for (y = 0; y < bmp_h; y++) {
		for (x = 0; x < bmp_w; x++) {
			fread(&pixel, 1, 4, infile);
			t = pixel.r;
			pixel.r = pixel.b;
			pixel.b = t;
			/* Do a lil flip. */
			fseek(
				outfile,
				12 + (x + (bmp_h - y - 1) * bmp_w) * 4,
				SEEK_SET
			);
			fwrite(&pixel, 1, 4, outfile);
		}
	}

end:
	fclose(infile);
	fclose(outfile);
	return ret;
}