/*
 * This utility constructs a 16-digit IMEISV from a 15-digit IMEI
 * (which must have a valid Luhn check digit) and a 2-digit SV field.
 * It is intended for use in shell scripts.
 */

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>

parse_imei_arg(input, buf)
	char *input, *buf;
{
	char *cp;
	int i;

	cp = input;
	if (!isdigit(*cp)) {
inv:		fprintf(stderr,
			"error: IMEI argument must have 15 decimal digits\n");
		exit(1);
	}
	for (i = 0; i < 15; i++) {
		if (ispunct(*cp))
			cp++;
		if (!isdigit(*cp))
			goto inv;
		buf[i] = *cp++;
	}
	if (*cp)
		goto inv;
}

check_luhn(digits)
	char *digits;
{
	int i, dig, sum;

	sum = 0;
	for (i = 0; i < 14; i++) {
		dig = digits[i] - '0';
		if (i & 1) {
			dig *= 2;
			if (dig > 9)
				dig -= 9;
		}
		sum += dig;
	}
	dig = sum % 10;
	if (dig)
		dig = 10 - dig;
	if (digits[14] != dig + '0') {
		fprintf(stderr, "error: given IMEI fails Luhn check\n");
		exit(1);
	}
}

main(argc, argv)
	char **argv;
{
	char imeibuf[15];

	if (argc != 3) {
		fprintf(stderr, "usage: %s IMEI SV\n", argv[0]);
		exit(1);
	}
	parse_imei_arg(argv[1], imeibuf);
	check_luhn(imeibuf);
	if (!isdigit(argv[2][0]) || !isdigit(argv[2][1]) || argv[2][2]) {
		fprintf(stderr,
			"error: SV argument must have 2 decimal digits\n");
		exit(1);
	}
	printf("%.8s-%.6s-%s\n", imeibuf, imeibuf + 8, argv[2]);
	exit(0);
}