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

#include <netinet/in.h>
#include <arpa/nameser.h>
#include <netdb.h>
#include <resolv.h>

u_char a[512];	/* answer */
unsigned get(const u_char **p, size_t n);
const u_char *name(const u_char *p);

int main(int argc, char **argv)
{
	int i;
	unsigned x;
	const u_char *p = a;
	int answer = 0;

	i = res_ninit(&_res);
	if (i != 0) {
		fprintf(stderr, "%s: res_init returned %d\n", argv[0]);
		return 1;
	}

#if 0
	_res.options |= RES_USE_INET6;
#endif
	fp_resstat(&_res, stdout);

	i = res_nquery(&_res,
		"patah.belnet.be",
		/* "ipv6.linux-tech.com", */
		/* "i5.nyu.edu", */
		ns_c_in, ns_t_aaaa, a, sizeof a);

	if (i <= 0) {
		fprintf(stderr, "%s: res_nquery returned %u\n", i);
		return 2;
	}

	x = get(&p, NS_INT16SZ);
	printf("identification %u\n", x);

	x = get(&p, NS_INT16SZ);
	printf("flags %u\n", x);

	x = get(&p, NS_INT16SZ);
	printf("number of questions %u\n", x);

	x = get(&p, NS_INT16SZ);
	printf("number of answer RRs %u\n", x);

	x = get(&p, NS_INT16SZ);
	printf("number of authority RRs %u\n", x);

	x = get(&p, NS_INT16SZ);
	printf("number of additional RRs %u\n", x);

	p = name(p);

	x = get(&p, NS_INT16SZ);
	printf("query type %u", x);
	if (x == ns_t_a) {
		printf(" (A)");
	} else if (x == ns_t_ns) {
		printf(" (NS)");
	} else if (x == ns_t_aaaa) {
		printf(" (AAAA)");
	}
	printf("\n");

	x = get(&p, NS_INT16SZ);
	printf("query class %u\n", x);

	for (answer = 1; p < a + i; ++answer) {
		unsigned type;
		printf("answer number %d -------------------\n", answer);
		p = name(p);

		type = get(&p, NS_INT16SZ);
		printf("query type %u", type);
		if (type == ns_t_a) {
			printf(" (A)");
		} else if (type == ns_t_ns) {
			printf(" (NS)");
		} else if (type == ns_t_aaaa) {
			printf(" (AAAA)");
		}
		printf("\n");

		x = get(&p, NS_INT16SZ);
		printf("query class %u\n", x);

		x = get(&p, NS_INT32SZ);
		printf("time to live: %u hours %u minutes\n",
			x / 60 / 60, x % 60);

		x = get(&p, NS_INT16SZ);
		printf("resource data length %u\n", x);

		if (type == ns_t_a) {
			char buffer[INET_ADDRSTRLEN];
			if (inet_ntop(AF_INET, p, buffer, sizeof buffer) ==
				NULL) {
				fprintf(stderr, "%s: inet_ntop AF_INET failed\n",
					argv[0]);
				return 3;
			}
			p += NS_INADDRSZ;
			printf("%s\n", buffer);
		}

		else if (type == ns_t_aaaa) {
			char buffer[INET6_ADDRSTRLEN];
			if (inet_ntop(AF_INET6, p, buffer, sizeof buffer) ==
				NULL) {
				fprintf(stderr, "%s: inet_ntop AF_INET6 failed\n",
					argv[0]);
				return 4;
			}
			p += NS_IN6ADDRSZ;
			printf("%s\n", buffer);
		}

		else {
			p = name(p);
		}
	}
	return EXIT_SUCCESS;
}

const u_char *name(const u_char *p)
{
	int first = 1;

	while (*p != 0) {
		if (first) {
			first = 0;
		} else {
			putchar('.');
		}

		const u_char n = *p;
		if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
			unsigned short offset = n << 8 | p[1];
			offset &= ~(NS_CMPRSFLGS << 8);
			name(a + offset);
			return p + NS_INT16SZ;
		}

		printf("%.*s", n, ++p);
		p += n;
	}

	putchar('\n');
	return p + 1;
}

unsigned get(const u_char **p, size_t n)
{
	size_t i;
	unsigned x = 0;

	for (i = 0; i < n; ++i) {
		x <<= 8;
		x |= *(*p)++;
	}

	return x;
}