/******************************************************************************
 * acs - access control string
 ******************************************************************************/

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

struct acs_info {
	unsigned char level;
	unsigned flags;
};

static void acs_init(struct acs_info *ai, unsigned level, unsigned flags) {
	ai->level=level<=UCHAR_MAX?level:UCHAR_MAX;
	ai->flags=flags;
}

static int acs_testflag(struct acs_info *ai, unsigned flag) {
	unsigned i;
	flag=tolower((char)flag);
	if(flag>='a' && flag<='z') {
		i=flag-'a';
	} else if(flag>='0' && flag<='9') {
		i=flag-'0'+26;
	} else {
		fprintf(stderr, "unknown flag '%c'\n", flag);
		return 0;
	}
	return ((ai->flags>>i)&1)==1;
}

static int acs_check(struct acs_info *ai, const char *acsstring) {
	const char *s=acsstring;
	const char *endptr;
	unsigned long level;
retry:
	while(*s) switch(*s++) {
		case 's':
			level=strtoul(s, (char**)&endptr, 10);
			if(endptr==acsstring) {
				goto parse_failure;
			}
			if(ai->level<level) goto did_not_pass;
			s=endptr;
			break;
		case 'f':
			if(!acs_testflag(ai, (unsigned)*s)) goto did_not_pass;
			s++;
			break;
		case '|':
			return 1; /* short circuit the OR */
		default:
			goto parse_failure;
	}
	return 1; /* everything matched */
did_not_pass:
	while(*s) if(*s++=='|') goto retry; /* look for an | */
	return 0;
parse_failure:
	fprintf(stderr, "acs parser failure '%s' (off=%d)\n", acsstring, s-acsstring);
	return 0;
}

#ifndef NDEBUG
void acs_test(void) {
	struct acs_info ai_test;

	acs_init(&ai_test, 4, 0);

	printf("acs_check() %d\n", acs_check(&ai_test, "s6fA"));
	printf("acs_check() %d\n", acs_check(&ai_test, "s2"));
	printf("acs_check() %d\n", acs_check(&ai_test, "s2fA"));
	printf("acs_check() %d\n", acs_check(&ai_test, "s8|s2"));
}

int main(void) {
	acs_test();
	return 0;
}
#endif