#include <string.h>

#include <platon/misc/luhnchk.h>

int luhncheck(const char *number)
{
	register int i, ii, num, parity, sum = 0;
	register int len_number      = strlen(number);
	register int real_len_number = 0;

	for (i = 0; i < len_number; i++) {
		num = number[i] - 48;
		if (num < 0 || num > 9)
			continue;
		real_len_number++;
	}

	if (real_len_number <= 0)
		return 0;
	parity = real_len_number % 2;

	for (ii = 0, i = 0; i < len_number; i++) {
		num = number[i] - 48;
		if (num < 0 || num > 9)
			continue;

		if (ii % 2 == parity) {
			sum += num * 2;
			if (num * 2 > 9)
				sum -= 9;
		} else {
			sum += num;
		}
		ii++;
	}

	return ! (sum % 10);
}

#if defined(SELF) || defined(SELFTEST) || defined(SELF_LUHNCHK)

#include <stdio.h>

int main(int argc, char **argv)
{

	if (argc < 2) {
		printf("Usage: %s <credit_card_number>\n", argv[0]);
		return 1;
	}

	printf("Credit card with number '%s' is %svalid.\n",
			argv[1], luhnchk(argv[1]) ? "" : "not ");

	return 0;
}

#endif