/* Copyright (C) 2020  C. McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <sysexits.h>

typedef unsigned char byte;

static const char *uuidGen(void) {
	byte uuid[16];
	arc4random_buf(uuid, sizeof(uuid));
	uuid[6] &= 0x0F;
	uuid[6] |= 0x40;
	uuid[8] &= 0x3F;
	uuid[8] |= 0x80;

	static char str[sizeof("00000000-0000-0000-0000-000000000000")];
	snprintf(
		str, sizeof(str),
		"%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
		uuid[0], uuid[1], uuid[2], uuid[3],
		uuid[4], uuid[5], uuid[6], uuid[7],
		uuid[8], uuid[9], uuid[10], uuid[11],
		uuid[12], uuid[13], uuid[14], uuid[15]
	);
	return str;
}

int main(void) {
	printf("%s\n", uuidGen());
}