/* 
HostToMask()
  Convert a userhost like "user@host.name.org" into "*user@*.name.org"
or "user@1.2.3.4" into "*user@1.2.3.*"
*/

char *
HostToMask (char *username, char *hostname)

{
  char *realhost, /* user@host (without nick!) */
       *temp,
       *final, /* final product */
       *user, /* stores the username */
       *host, /* stores the hostname */
       /* 
        * first segment of hostname (ie: if host == "a.b.c",
        * topsegment == "c" (top-level domain)
        */
       *topsegment = NULL;
  char userhost[UHOSTLEN + 2];
  int ii, /* looping */
      cnt,
      len;

  if (!username || !hostname)
    return (NULL);

  ircsprintf(userhost, "%s@%s", username, hostname);

  len = strlen(userhost) + 32;

  final = (char *) MyMalloc(len);
  memset(final, 0, len);

  /* strip off a nick nick!user@host (if there is one) */
  realhost = (host = strchr(userhost, '!')) ? host + 1 : userhost;
  user = realhost;
  if ((host = strchr(realhost, '@')))
  {
    final[0] = '*';
    ii = 1;
    /* 
     * only use the last 8 characters of the username if there 
     * are more
     *
     * >=10, not >10. We lost one character to the * prefix
     *  -- asuffield
     */
    if ((host - realhost) >= 10)
      user = host - 8;

    /* now store the username into 'final' */
    while (*user != '@')
      final[ii++] = *user++;

    final[ii++] = '@';

    /* host == "@host.name", so point past the @ */
    host++;
  }
  else
  {
    /* there's no @ in the hostname, just make it *@*.host.com */
    strcpy(final, "*@");
    ii = 2;
    host = userhost;
  }

  /* 
   * ii now points to the offset in 'final' of where the 
   * converted hostname should go
   */

  realhost = strchr(host, '.');
  if (realhost)
    topsegment = strchr(realhost + 1, '.');
  if (!realhost || !topsegment)
  {
    /* 
     * if realhost is NULL, then the hostname must be a top-level
     * domain; and if topsegment is NULL, the hostname must be
     * 2 parts (ie: blah.org), so don't strip off "blah"
     */
    strcpy(final + ii, host);
  }
  else
  {
    /*
     * topsegment now contains the top-level domain - if it's
     * numerical, it MUST be an ip address, since there are
     * no numerical TLD's =P
     */

    /* advance to the end of topsegment */
    for (temp = topsegment; *temp; temp++);

    --temp; /* point to the last letter (number) of the TLD */
    if ((*temp >= '0') && (*temp <= '9'))
    {
      /* Numerical IP Address */
      while (*temp != '.')
        --temp;

      /* 
       * copy the ip address (except the last .XXX) into the 
       * right spot in 'final'
       */
      strncpy(final + ii, host, temp - host);

      /* stick a .* on the end :-) */
      ii += (temp - host);
      strcpy(final + ii, ".*");
    }
    else
    {
      /* its a regular hostname with >= 3 segments */

      if (SmartMasking)
      {
        /*
         * Pick up with temp from were we left off above.
         * Temp now points to the very last charater of userhost.
         * Go backwards, counting all the periods we encounter.
         * If we find 3 periods, make the hostmask:
         *   *.seg1.seg2.seg3
         * Since some users may have extremely long hostnames
         * because of some weird isp. Also, if they have
         * a second TLD, such as xx.xx.isp.com.au, this
         * routine will make their mask: *.isp.com.au, which
         * is much better than *.xx.isp.com.au
         */
        cnt = 0;
        while (temp--)
        {
          if (*temp == '.')
            if (++cnt >= 3)
              break;
        }

        if (cnt >= 3)
        {
          /*
           * We have a hostname with more than 3 segments.
           * Set topsegment to temp, so the final mask
           * will be *user@*.seg1.seg2.seg3
           */
          topsegment = temp;
        }
      } /* if (SmartMasking) */

      /*
       * topsegment doesn't necessarily point to the TLD.
       * It simply points one segment further than realhost.
       * Check if there is another period in topsegment,
       * and if so use it. Otherwise use realhost
       */
      ircsprintf(final + ii, "*%s", 
        strchr(topsegment + 1, '.') ? topsegment : realhost);
    }
  }

  return (final);
} /* HostToMask() */