/*
 * otpcli - CLI utility for generating OTPs
 *
 * Written in 2020-2021 by Lucas
 *
 * To the extent possible under law, the author(s) have dedicated all
 * copyright and related and neighboring rights to this software to the
 * public domain worldwide. This software is distributed without any
 * warranty.
 *
 * You should have received a copy of the CC0 Public Domain Dedication
 * along with this software. If not, see
 * <http://creativecommons.org/publicdomain/zero/1.0/>.
 */

#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "err.h"
#include "strtonum.h"
#include "otp.h"

#define LINE_SIZE 16384

extern const char *__progname;

static void
usage(void)
{
	fprintf(stderr, "Usage:\n"
	    "    %s [-d digits] [-h HMAC] -H counter SECRET\n"
	    "    %s [-d digits] [-h HMAC] [-s step] [-T counter] SECRET\n",
	    __progname, __progname);
	exit(1);
}

int
main(int argc, char *argv[])
{
	const char *errstr;
	char *key;
	size_t key_len;
	uint64_t counter;
	unsigned int step;
	int32_t r;
	int ch, digits, do_hotp, do_totp;
	enum otp_hmac hmac;

	counter = (uint64_t)time(NULL);
	digits = 6;
	do_hotp = do_totp = 0;
	hmac = OTP_HMAC_SHA1;
	step = 30;
	while ((ch = getopt(argc, argv, "d:H:h:s:T:")) != -1) {
		switch (ch) {
		case 'd':
			digits = strtonum(optarg, 6, 10, &errstr);
			if (errstr != NULL)
				errx(1, "digits is %s: %s", errstr, optarg);
			break;
		case 'H':
			counter = strtonum(optarg, 0, LLONG_MAX, &errstr);
			if (errstr != NULL)
				errx(1, "counter is %s: %s", errstr, optarg);
			do_hotp = 1;
			break;
		case 'h':
			if (strcasecmp(optarg, "sha1") == 0)
				hmac = OTP_HMAC_SHA1;
			else if (strcasecmp(optarg, "sha256") == 0)
				hmac = OTP_HMAC_SHA256;
			else if (strcasecmp(optarg, "sha512") == 0)
				hmac = OTP_HMAC_SHA512;
			else
				usage();
			break;
		case 's':
			step = strtonum(optarg, 1, UINT_MAX, &errstr);
			if (errstr != NULL)
				errx(1, "step is %s: %s", errstr, optarg);
			break;
		case 'T':
			counter = strtonum(optarg, 0, LLONG_MAX, &errstr);
			if (errstr != NULL)
				errx(1, "counter is %s: %s", errstr, optarg);
			do_totp = 1;
			break;
		default:
			usage();
		}
	}
	argc -= optind;
	argv += optind;

	if (do_hotp && do_totp) {
		warnx("-H and -T are mutually exclusive");
		usage();
	}

	if (argc > 1)
		usage();

	if (argc == 1) {
		key = argv[0];
		key_len = strlen(key);
	} else {
		key = malloc(sizeof(uint8_t) * (LINE_SIZE + 1));
		if (key == NULL)
			err(1, "malloc");
		if (fgets(key, LINE_SIZE + 1, stdin) == NULL)
			err(1, "fgets");
		key_len = strlen(key);
		if (key[key_len - 1] == '\n') {
			key[key_len - 1] = '\0';
			key_len--;
		}
	}

	if (do_hotp) {
		r = hotp(hmac, key, key_len, counter, digits);
		if (r == -1)
			errx(1, "couldn't calculate HOTP");
		printf("%0*" PRId32 "\n", digits, r);
	} else {
		r = totp(hmac, key, key_len, counter, step, digits);
		if (r == -1)
			errx(1, "couldn't calculate TOTP");
		printf("%0*" PRId32 "\n", digits, r);
	}

	return 0;
}