#include "platform.h"
#include "gnunet-dns-parser.h"
#include "gnunet-vpn-packet.h"

/**
 * Parse a name from DNS to a normal .-delimited, 0-terminated string.
 *
 * @param d The destination of the name. Should have at least 255 bytes allocated.
 * @param src The DNS-Packet
 * @param idx The offset inside the Packet from which on the name should be read
 * @returns The offset of the first unparsed byte (the byte right behind the name)
 */
static unsigned int
parse_dns_name (char *d, const unsigned char *src, unsigned short idx)
{                               /*{{{ */
  char *dest = d;

  int len = src[idx++];

  while (len != 0)
  {
    if (len & 0xC0)
    {                           /* Compressed name, offset in this and the next octet */
      unsigned short offset = ((len & 0x3F) << 8) | src[idx++];

      parse_dns_name (dest, src, offset - 12);  /* 12 for the Header of the DNS-Packet, idx starts at 0 which is 12 bytes from the start of the packet */
      return idx;
    }
    memcpy (dest, src + idx, len);
    idx += len;
    dest += len;
    *dest = '.';
    dest++;
    len = src[idx++];
  };
  *dest = 0;

  return idx;
}

/*}}}*/

/**
 * Parse a complete DNS-Record from raw DNS-data to a struct dns_record
 *
 * @param data The DNS-data
 * @param dst Pointer to count pointers; individual pointers will be allocated
 * @param count Number of records to parse
 * @param idx The offset inside the Packet from which on the name should be read
 * @returns The offset of the first unparsed byte (the byte right behind the last record)
 */
static unsigned short
parse_dns_record (unsigned char *data,  /*{{{ */
                  struct dns_record **dst, unsigned short count,
                  unsigned short idx)
{
  int i;
  unsigned short _idx;

  for (i = 0; i < count; i++)
  {
    dst[i] = GNUNET_malloc (sizeof (struct dns_record));
    dst[i]->name = alloca (255);        // see RFC1035, no name can be longer than this.
    char *name = dst[i]->name;

    _idx = parse_dns_name (name, data, idx);
    dst[i]->namelen = _idx - idx;

    dst[i]->name = GNUNET_malloc (dst[i]->namelen);
    memcpy (dst[i]->name, name, dst[i]->namelen);

    idx = _idx;

    dst[i]->type = *((unsigned short *) (data + idx));
    idx += 2;
    dst[i]->class = *((unsigned short *) (data + idx));
    idx += 2;
    dst[i]->ttl = *((unsigned int *) (data + idx));
    idx += 4;
    dst[i]->data_len = *((unsigned short *) (data + idx));
    idx += 2;
    dst[i]->data = GNUNET_malloc (ntohs (dst[i]->data_len));
    memcpy (dst[i]->data, data + idx, ntohs (dst[i]->data_len));
    idx += ntohs (dst[i]->data_len);
  }
  return idx;
}                               /*}}} */

/**
 * Parse a raw DNS-Packet into an usable struct
 */
struct dns_pkt_parsed *
parse_dns_packet (struct dns_pkt *pkt)
{                               /*{{{ */
  struct dns_pkt_parsed *ppkt = GNUNET_malloc (sizeof (struct dns_pkt_parsed));

  memcpy (&ppkt->s, &pkt->s, sizeof pkt->s);

  unsigned short qdcount = ntohs (ppkt->s.qdcount);
  unsigned short ancount = ntohs (ppkt->s.ancount);
  unsigned short nscount = ntohs (ppkt->s.nscount);
  unsigned short arcount = ntohs (ppkt->s.arcount);

  ppkt->queries = GNUNET_malloc (qdcount * sizeof (struct dns_query *));
  ppkt->answers = GNUNET_malloc (ancount * sizeof (struct dns_record *));
  ppkt->nameservers = GNUNET_malloc (nscount * sizeof (struct dns_record *));
  ppkt->additional = GNUNET_malloc (arcount * sizeof (struct dns_record *));

  unsigned short idx = 0, _idx; /* This keeps track how far we have parsed the data */

  /* Parse the Query */
  int i;

  for (i = 0; i < qdcount; i++)
  {                             /*{{{ */
    ppkt->queries[i] = GNUNET_malloc (sizeof (struct dns_query));
    char *name = alloca (255);  /* see RFC1035, it can't be more than this. */

    _idx = parse_dns_name (name, pkt->data, idx);
    ppkt->queries[i]->namelen = _idx - idx;
    idx = _idx;

    ppkt->queries[i]->name = GNUNET_malloc (ppkt->queries[i]->namelen);
    memcpy (ppkt->queries[i]->name, name, ppkt->queries[i]->namelen);

    ppkt->queries[i]->qtype = *((unsigned short *) (pkt->data + idx));
    idx += 2;
    ppkt->queries[i]->qclass = *((unsigned short *) (pkt->data + idx));
    idx += 2;
  }
  /*}}} */
  idx = parse_dns_record (pkt->data, ppkt->answers, ancount, idx);
  idx = parse_dns_record (pkt->data, ppkt->nameservers, nscount, idx);
  idx = parse_dns_record (pkt->data, ppkt->additional, arcount, idx);
  return ppkt;
}                               /*}}} */

static void
unparse_dns_name (char *dest, char *src, size_t len)
{
  char *b = dest;
  char cnt = 0;

  dest++;
  while (*src != 0)
  {
    while (*src != '.' && *src != 0)
    {
      *dest = *src;
      src++;
      dest++;
      cnt++;
    }
    *b = cnt;
    cnt = 0;
    b = dest;
    dest++;
    src++;
  }
  *b = 0;
}

struct dns_pkt *
unparse_dns_packet (struct dns_pkt_parsed *ppkt)
{
  size_t size = sizeof (struct dns_pkt) - 1;
  int i;

  for (i = 0; i < ntohs (ppkt->s.qdcount); i++)
    size += ppkt->queries[i]->namelen + 1;

  for (i = 0; i < ntohs (ppkt->s.ancount); i++)
  {
    size += ppkt->answers[i]->namelen + 1;
    size += ppkt->answers[i]->data_len;
  }
  for (i = 0; i < ntohs (ppkt->s.nscount); i++)
  {
    size += ppkt->nameservers[i]->namelen + 1;
    size += ppkt->nameservers[i]->data_len;
  }
  for (i = 0; i < ntohs (ppkt->s.arcount); i++)
  {
    size += ppkt->additional[i]->namelen + 1;
    size += ppkt->additional[i]->data_len;
  }

  size +=
      4 * ntohs (ppkt->s.qdcount) + 10 * (ntohs (ppkt->s.ancount) +
                                          ntohs (ppkt->s.arcount) +
                                          ntohs (ppkt->s.nscount));

  struct dns_pkt *pkt = GNUNET_malloc (size);
  char *pkt_c = (char *) pkt;

  memcpy (&pkt->s, &ppkt->s, sizeof ppkt->s);
  size_t idx = sizeof ppkt->s;

  for (i = 0; i < ntohs (ppkt->s.qdcount); i++)
  {
    unparse_dns_name (&pkt_c[idx], ppkt->queries[i]->name,
                      ppkt->queries[i]->namelen);
    idx += ppkt->queries[i]->namelen;
    struct dns_query_line *d = (struct dns_query_line *) &pkt_c[idx];

    d->class = ppkt->queries[i]->qclass;
    d->type = ppkt->queries[i]->qtype;
    idx += sizeof (struct dns_query_line);
  }

  for (i = 0; i < ntohs (ppkt->s.ancount); i++)
  {
    unparse_dns_name (&pkt_c[idx], ppkt->answers[i]->name,
                      ppkt->answers[i]->namelen);
    idx += ppkt->answers[i]->namelen;
    struct dns_record_line *r = (struct dns_record_line *) &pkt_c[idx];

    r->type = ppkt->answers[i]->type;
    r->class = ppkt->answers[i]->class;
    r->ttl = ppkt->answers[i]->ttl;
    r->data_len = ppkt->answers[i]->data_len;
    idx += sizeof (struct dns_record_line);
    memcpy (&r->data, ppkt->answers[i]->data, ppkt->answers[i]->data_len);
    idx += ppkt->answers[i]->data_len;
  }

  for (i = 0; i < ntohs (ppkt->s.nscount); i++)
  {
    unparse_dns_name (&pkt_c[idx], ppkt->nameservers[i]->name,
                      ppkt->nameservers[i]->namelen);
    idx += ppkt->nameservers[i]->namelen;
    struct dns_record_line *r = (struct dns_record_line *) &pkt_c[idx];

    r->type = ppkt->nameservers[i]->type;
    r->class = ppkt->nameservers[i]->class;
    r->ttl = ppkt->nameservers[i]->ttl;
    r->data_len = ppkt->nameservers[i]->data_len;
    idx += sizeof (struct dns_record_line);
    memcpy (&r->data, ppkt->nameservers[i]->data,
            ppkt->nameservers[i]->data_len);
    idx += ppkt->nameservers[i]->data_len;
  }

  for (i = 0; i < ntohs (ppkt->s.arcount); i++)
  {
    unparse_dns_name (&pkt_c[idx], ppkt->additional[i]->name,
                      ppkt->additional[i]->namelen);
    idx += ppkt->additional[i]->namelen;
    struct dns_record_line *r = (struct dns_record_line *) &pkt_c[idx];

    r->type = ppkt->additional[i]->type;
    r->class = ppkt->additional[i]->class;
    r->ttl = ppkt->additional[i]->ttl;
    r->data_len = ppkt->additional[i]->data_len;
    idx += sizeof (struct dns_record_line);
    memcpy (&r->data, ppkt->additional[i]->data, ppkt->additional[i]->data_len);
    idx += ppkt->additional[i]->data_len;
  }

  return pkt;
}

void
free_parsed_dns_packet (struct dns_pkt_parsed *ppkt)
{
  unsigned short qdcount = ntohs (ppkt->s.qdcount);
  unsigned short ancount = ntohs (ppkt->s.ancount);
  unsigned short nscount = ntohs (ppkt->s.nscount);
  unsigned short arcount = ntohs (ppkt->s.arcount);

  int i;

  for (i = 0; i < qdcount; i++)
  {
    GNUNET_free (ppkt->queries[i]->name);
    GNUNET_free (ppkt->queries[i]);
  }
  GNUNET_free (ppkt->queries);
  for (i = 0; i < ancount; i++)
  {
    GNUNET_free (ppkt->answers[i]->name);
    GNUNET_free (ppkt->answers[i]->data);
    GNUNET_free (ppkt->answers[i]);
  }
  GNUNET_free (ppkt->answers);
  for (i = 0; i < nscount; i++)
  {
    GNUNET_free (ppkt->nameservers[i]->name);
    GNUNET_free (ppkt->nameservers[i]->data);
    GNUNET_free (ppkt->nameservers[i]);
  }
  GNUNET_free (ppkt->nameservers);
  for (i = 0; i < arcount; i++)
  {
    GNUNET_free (ppkt->additional[i]->name);
    GNUNET_free (ppkt->additional[i]->data);
    GNUNET_free (ppkt->additional[i]);
  }
  GNUNET_free (ppkt->additional);
  GNUNET_free (ppkt);
}