#include "byte.h"
#include "dnsresolv.h"
#include "stralloc.h"
#include "uint_t.h"

int dns_txt_packet(stralloc *out, const char *buf, unsigned int len)
{
  unsigned int pos;
  char header[12];
  uint16 numanswers;
  uint16 datalen;
  char ch;
  unsigned int txtlen;
  int i;
  int ranswers = 0;

  if (!stralloc_copys(out, "")) return DNS_MEM;

  pos = dns_packet_copy(buf, len, 0, header, 12);
  if (!pos) return DNS_ERR;
  uint16_unpack_big(header + 6, &numanswers);
  pos = dns_packet_skipname(buf, len, pos);
  if (!pos) return DNS_ERR;
  pos += 4;

  while (numanswers--) {
    pos = dns_packet_skipname(buf, len, pos);
    if (!pos) return DNS_ERR;
    pos = dns_packet_copy(buf, len, pos, header, 10);
    if (!pos) return DNS_ERR;
    uint16_unpack_big(header + 8, &datalen);
    if (byte_equal(header, 2, DNS_T_TXT))
      if (byte_equal(header + 2, 2, DNS_C_IN)) {
        if (pos + datalen > len) return DNS_ERR;
        txtlen = (unsigned char)buf[pos];
        for (i = 1; i < datalen; ++i) {
          ch = buf[pos + i];
          if (i == txtlen + 1)  // next label
            txtlen += (unsigned char)ch + 1;
          else {
            if (ch < 32) ch = '?';
            if (ch > 126) ch = '?';
            if (!stralloc_append(out, &ch)) return DNS_MEM;
          }
        }
      }
    pos += datalen;
    ++ranswers;
    if (numanswers)
      if (!stralloc_append(out, "\n")) return DNS_MEM;
  }

  return ranswers;
}

static char *q = 0;

int dns_txt(stralloc *out, const stralloc *fqdn)
{
  int rc;

  if (dns_domain_fromdot(&q, fqdn->s, fqdn->len) <= 0) return DNS_ERR;
  if (dns_resolve(q, DNS_T_TXT) < 0) return DNS_ERR;
  if ((rc = dns_txt_packet(out, dns_resolve_tx.packet, dns_resolve_tx.packetlen)) < 0) return DNS_ERR;
  dns_transmit_free(&dns_resolve_tx);
  dns_domain_free(&q);

  return rc;
}