#include "dns.h"

#include <arpa/nameser.h>

#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>

#include "alloc.h"
#include "ip.h"
#include "str.h"
#include "stralloc.h"

#include "ipalloc.h"

/**
 * @file dns.c
 * @brief DNS helpers: dns_ipplus, dns_ipalloc, dns_ip (IPv4+IPv6), dns_mxip
 */

static stralloc glue = {0};
static stralloc ip = {0};

static int dns_ipplus(ipalloc *ia, stralloc *sa, int pref)
{
  struct ip_mx ix;
  int error = 0;
  char ip4[4];
  char ip6[16];
  int i;

  /* Case 1: sa is just IPv4 */

  if (ip4_scanbracket(sa->s, ip4)) {
    if (!stralloc_copys(&glue, sa->s)) return DNS_MEM;
    if (!stralloc_0(&glue)) return DNS_MEM;
    if (glue.s[0]) {
      ix.pref = 0;
      ix.af = AF_INET;
      byte_copy(&ix.addr, 4, ip4);  //  = ip; //cp
      if (!ipalloc_append(ia, &ix)) return DNS_MEM;
      return 0;
    }
  }

  /* Case 2: sa is just IPv6 */

  if (ip6_scanbracket(sa->s, ip6)) {
    if (!stralloc_copys(&glue, sa->s)) return DNS_MEM;
    if (!stralloc_0(&glue)) return DNS_MEM;
    if (glue.s[0]) {
      ix.pref = 0;
      ix.af = AF_INET6;
      byte_copy(&ix.addr, 16, ip6);  //  = ip; //cp
      if (!ipalloc_append(ia, &ix)) return DNS_MEM;
      return 0;
    }
  }

  /* Case 3: sa is fqdn and looking for IPv6 */

  if (dns_ip6(&ip, sa) > 0) {
    for (i = 0; i + 16 <= ip.len; i += 16) {
      if (ip6_isv4mapped(ip.s + i)) continue;
      ix.af = AF_INET6;
      ix.pref = pref;
      byte_copy(&ix.addr, 16, ip.s + i);  //  = ip; //cp
      str_copy(ix.mxh, sa->s);            // mx hostname
      if (!ipalloc_append(ia, &ix)) {
        error = DNS_MEM;
        break;
      }
      error = 0;
    }
  } else {
    error = 1;
  }

  /* Case 4: sa is fqdn and looking for IPv4 */

  if (dns_ip4(&ip, sa) > 0) {
    for (i = 0; i + 4 <= ip.len; i += 4) {
      ix.af = AF_INET;
      ix.pref = pref;
      byte_copy(&ix.addr, 4, ip.s + i);  //  = ip; //cp
      str_copy(ix.mxh, sa->s);           // mx hostname
      if (!ipalloc_append(ia, &ix)) {
        error = DNS_MEM;
        break;
      }
      error = 0;
    }
  } else {
    error += 2;
  }

  return error;
}

static int dns_ipalloc(ipalloc *ia, stralloc *sa)
{
  if (!ipalloc_readyplus(ia, 0)) return DNS_MEM;
  ia->len = 0;

  return dns_ipplus(ia, sa, 0);
}

/* dns_mxip */

int dns_mxip(ipalloc *ia, stralloc *sa, unsigned long random)
{
  struct mx {
    stralloc sa;
    unsigned short p;
  } *mx;
  struct ip_mx ix;
  int nummx;
  int i;
  int j = 0;
  int len;
  int flagsoft;
  uint16 pref;

  /* Case 1: sa is just IPv4 or IPv6 */

  if (!ipalloc_readyplus(ia, 0)) return DNS_MEM;
  ia->len = 0;

  if (!stralloc_copys(&glue, sa->s)) return DNS_MEM;
  if (!stralloc_0(&glue)) return DNS_MEM;
  if (glue.s[0]) {
    ix.pref = 0;
    if (!glue.s[ip4_scan(glue.s, (char *)&ix.addr.ip4)]
        || !glue.s[ip4_scanbracket(glue.s, (char *)&ix.addr.ip4)])
    {
      ix.af = AF_INET;
      if (!ipalloc_append(ia, &ix)) return DNS_MEM;
      return 0;
    }
    if (!glue.s[ip6_scan(glue.s, (char *)&ix.addr.ip6)]
        || !glue.s[ip6_scanbracket(glue.s, (char *)&ix.addr.ip6)])
    {
      ix.af = AF_INET6;
      if (!ipalloc_append(ia, &ix)) return DNS_MEM;
      return 0;
    }
  }

  /* Case 2:  sa is FQDN and do a mx lookup */

  DNS_INIT
  nummx = 0;
  len = 0;
  i = dns_mx(&ip, sa);
  mx = (struct mx *)alloc(i * sizeof(struct mx));
  if (!mx) return DNS_MEM;

  if (i) {
    do {
      j = str_chr(ip.s + len + 2, '\0'); /* several answers */
      mx[nummx].sa.s = 0;
      if (!stralloc_copys(&mx[nummx].sa, ip.s + len + 2)) { /* mxhost name */
        alloc_free(mx);
        return DNS_MEM;
      }
      ip.s[len + 3] = '\0';
      uint16_unpack_big(ip.s + len, &pref);
      mx[nummx].p = pref;
      len += j + 3;
      ++nummx;
    } while (len < ip.len);
  }

  if (!nummx) return dns_ipalloc(ia, sa); /* e.g., CNAME -> A */
  flagsoft = 0;

  while (nummx > 0) {
    unsigned long numsame;
    i = 0;
    numsame = 1;
    for (j = 1; j < nummx; ++j) {
      if (mx[j].p < mx[i].p) {
        i = j;
        numsame = 1;
      } else if (mx[j].p == mx[i].p) {
        ++numsame;
        random = random * 69069 + 1;
        if ((random / 2) < (2147483647 / numsame)) i = j;
      }
    }

    switch (dns_ipplus(ia, &mx[i].sa, mx[i].p)) {
      case -1: return DNS_MEM;
      case -2:
      case -3: flagsoft = -5; break;
    }

    alloc_free(mx[i].sa.s);
    mx[i] = mx[--nummx];
  }

  alloc_free(mx);
  return flagsoft;
}

int dns_ip(ipalloc *ia, stralloc *sa)
{

  if (!ipalloc_readyplus(ia, 0)) return DNS_MEM;
  ia->len = 0;

  return dns_ipplus(ia, sa, 0);
}