/*
    CrossFire, A Multiplayer game for X-windows

    Copyright (C) 1992 Frank Tore Johansen

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

    The author can be reached via e-mail to mark@pyramid.com
*/

/**
 * \file
 * Low-level socket-related functions.
 *
 * \date 2003-12-02
 *
 * Contains some base functions that both the client and server
 * can use.  As such, depending what we are being compiled for will
 * determine what we can include.  the client is designed have
 * CFCLIENT defined as part of its compile flags.
 */

using namespace std;

#include <global.h>
#include <newclient.h>
#include <sproto.h>
#include <cstdarg>

#ifdef __linux__
# include <sys/types.h>
# include <sys/socket.h>
# include <netinet/in.h>
# define TCP_HZ 1000            // sorry...
# include <netinet/tcp.h>
#endif

// use a really low timeout, as it doesn't cost any bandwidth, and you can
// easily die in 20 seconds...
#define SOCKET_TIMEOUT1 10
#define SOCKET_TIMEOUT2 20

void
Socket_Flush (client_socket * ns)
{
#ifdef __linux__
  // check time of last ack, and, if too old, kill connection
  struct tcp_info tcpi;
  socklen_t len = sizeof (tcpi);

  if (!getsockopt (ns->fd, IPPROTO_TCP, TCP_INFO, &tcpi, &len) && len == sizeof (tcpi))
    {
      unsigned int diff = tcpi.tcpi_last_ack_recv - tcpi.tcpi_last_data_sent;

      if (tcpi.tcpi_unacked && SOCKET_TIMEOUT1 * TCP_HZ < diff && diff < 0x80000000UL   // ack delayed for 20s
          && SOCKET_TIMEOUT2 * TCP_HZ < tcpi.tcpi_last_data_sent)       // no data sent for 10s
        {
          LOG (llevDebug, "Connection on fd %d closed due to ack timeout (%u/%u/%u)\n", ns->fd,
               (unsigned) tcpi.tcpi_last_ack_recv, (unsigned) tcpi.tcpi_last_data_sent, (unsigned) tcpi.tcpi_unacked);
          ns->status = Ns_Dead;
        }
    }

  int val;

  val = 0; setsockopt (ns->fd, IPPROTO_TCP, TCP_CORK, &val, sizeof (val));
  val = 1; setsockopt (ns->fd, IPPROTO_TCP, TCP_CORK, &val, sizeof (val));
#endif
}

/***********************************************************************
 *
 * packet functions/utilities
 *
 **********************************************************************/

packet &packet::operator <<(const data   &v)
{
  if (room () < v.len)
    reset ();
  else
    {
      if (v.len)
        {
          memcpy (cur, v.ptr, v.len);
          cur += v.len;
        }
    }

  return *this;
}

packet &packet::operator <<(const data8  &v)
{
  unsigned int len = min (v.len, 0x00FF);
  return *this << uint8  (len) << data (v.ptr, len);
}

packet &packet::operator <<(const data16 &v)
{
  unsigned int len = min (v.len, 0xFFFF);
  return *this << uint16 (len) << data (v.ptr, len);
}

packet &packet::operator <<(const char *v)
{
  return *this << data (v, strlen (v ? v : 0));
}

void
packet::printf (const char *format, ...)
{
  int size = room ();

  va_list ap;
  va_start (ap, format);
  int len = vsnprintf ((char *)cur, size, format, ap);
  va_end (ap);

  if (len >= size)
    return reset ();

  cur += len;
}

/******************************************************************************
 *
 * Start of read routines.
 *
 ******************************************************************************/

int
client_socket::read_packet ()
{
  for (;;)
    {
      if (inbuf_len >= 2)
        {
          unsigned int pkt_len = (inbuf [0] << 8) | inbuf [1];

          if (inbuf_len >= 2 + pkt_len)
            return  pkt_len + 2;
        }

      int amount = sizeof (inbuf) - inbuf_len;

      if (amount <= 0)
        {
          LOG (llevError, "packet too large");//TODO
          return -1;
        }

      amount = read (fd, inbuf + inbuf_len, amount);

      if (!amount)
        {
          status = Ns_Dead;
          return -1;
        }
      else if (amount < 0)
        {
          if (errno != EAGAIN && errno != EINTR)
            {
              LOG (llevError, "read error: %s", strerror (errno));
              return -1;
            }

          return 0;
        }

      inbuf_len += amount;

      cst_tot.ibytes += amount;
      cst_lst.ibytes += amount;
    }
}

void
client_socket::skip_packet (int len)
{
  inbuf_len -= len;
  memmove (inbuf, inbuf + len, inbuf_len);
}

/*******************************************************************************
 *
 * Start of write related routines.
 *
 ******************************************************************************/

/**
 * Adds data to a socket buffer for whatever reason.
 *
 * ns is the socket we are adding the data to, buf is the start of the
 * data, and len is the number of bytes to add.
 */

static void
add_to_buffer (client_socket *ns, char *buf, int len)
{
  int avail, end;

  if ((len + ns->outputbuffer.len) > SOCKETBUFSIZE)
    {
      LOG (llevDebug, "Socket on fd %d has overrun internal buffer - marking as dead\n", ns->fd);
      ns->status = Ns_Dead;
      return;
    }

  /* data + end is where we start putting the new data.  The last byte
   * currently in use is actually data + end -1
   */

  end = ns->outputbuffer.start + ns->outputbuffer.len;
  /* The buffer is already in a wrapped state, so adjust end */
  if (end >= SOCKETBUFSIZE)
    end -= SOCKETBUFSIZE;

  avail = SOCKETBUFSIZE - end;

  /* We can all fit it behind the current data without wrapping */
  if (avail >= len)
    memcpy (ns->outputbuffer.data + end, buf, len);
  else
    {
      memcpy (ns->outputbuffer.data + end, buf, avail);
      memcpy (ns->outputbuffer.data, buf + avail, len - avail);
    }

  ns->outputbuffer.len += len;
#if 0
  LOG (llevDebug, "Added %d to output buffer, total length now %d, start=%d\n", len, ns->outputbuffer.len, ns->outputbuffer.start);
#endif
}

/**
 * Writes data to socket.
 *
 * When the socket is clear to write, and we have backlogged data, this
 * is called to write it out.
 */
void
write_socket_buffer (client_socket * ns)
{
  int amt, max;

  if (ns->outputbuffer.len == 0)
    {
      LOG (llevDebug, "write_socket_buffer called when there is no data, fd=%d\n", ns->fd);
      return;
    }

  do
    {
      max = SOCKETBUFSIZE - ns->outputbuffer.start;
      if (ns->outputbuffer.len < max)
        max = ns->outputbuffer.len;

      do
        {
          amt = write (ns->fd, ns->outputbuffer.data + ns->outputbuffer.start, max);
        }
      while ((amt < 0) && (errno == EINTR));

      if (amt < 0)
        {                       /* We got an error */

          if (errno != EWOULDBLOCK)
            {
              LOG (llevError, "New socket write failed (wsb) (%d: %s).\n", errno, strerror (errno));
              ns->status = Ns_Dead;
              return;
            }
          else
            {                   /* EWOULDBLOCK */
              /* can't write it, so store it away. */
              ns->can_write = 0;
              return;
            }
        }
      ns->outputbuffer.start += amt;
      /* wrap back to start of buffer */
      if (ns->outputbuffer.start == SOCKETBUFSIZE)
        ns->outputbuffer.start = 0;
      ns->outputbuffer.len -= amt;
#ifdef CS_LOGSTATS
      cst_tot.obytes += amt;
      cst_lst.obytes += amt;
#endif
    }
  while (ns->outputbuffer.len > 0);
}

/**
 * This writes data to the socket. - It is very low level -
 * all we try and do is write out the data to the socket
 * provided (ns).  buf is the data to write, len is the number
 * of bytes to write.  IT doesn't return anything - rather, it
 * updates the ns structure if we get an  error.
 */
void
client_socket::send (void *buf_, int len)
{
  char *buf = (char *)buf_;
  char *pos = buf;
  int amt = 0;

  if (status == Ns_Dead || !buf)
    {
      LOG (llevDebug, "Write_To_Socket called with dead socket\n");
      return;
    }

#ifndef __GNU__                 /* This caused problems on Hurd */
  if (!can_write)
    {
      add_to_buffer (this, buf, len);
      return;
    }
#endif

  /* If we manage to write more than we wanted, take it as a bonus */
  while (len > 0)
    {
      do
        {
          amt = write (fd, pos, len);
        }
      while ((amt < 0) && (errno == EINTR));

      if (amt < 0)
        {                       /* We got an error */
          if (errno != EWOULDBLOCK)
            {
              LOG (llevError, "New socket write failed WTS (%d: %s).\n",        /* ---WIN32 */
                   errno, strerror (errno));
              status = Ns_Dead;
              return;
            }
          else
            {                   /* EWOULDBLOCK */
              /* can't write it, so store it away. */
              add_to_buffer (this, pos, len);
              can_write = 0;
              return;
            }
        }
      /* amt gets set to 0 above in blocking code, so we do this as
       * an else if to make sure we don't reprocess it.
       */
      else if (amt == 0)
        LOG (llevError, "Write_To_Socket: No data written out.\n");

      len -= amt;
      pos += amt;
#ifdef CS_LOGSTATS
      cst_tot.obytes += amt;
      cst_lst.obytes += amt;
#endif
    }
}

/**
 * Takes a string of data, and writes it out to the socket. A very handy
 * shortcut function.
 */

void
client_socket::send_packet (packet &sl)
{
  Send_With_Handling (this, &sl);
}

void
client_socket::send_packet (const char *buf, int len)
{
  packet sl;

  sl << data (buf, len);
  send_packet (sl);
}

void
client_socket::send_packet (const char *buf)
{
  send_packet (buf, strlen (buf));
}

/**
 * Calls Write_To_Socket to send data to the client.
 *
 * The only difference in this function is that we take a packet
 *, and we prepend the length information.
 */
void
Send_With_Handling (client_socket *ns, packet *msg)
{
  unsigned char sbuf[4];

  if (ns->status == Ns_Dead || !msg)
    return;

  if (msg->length () >= MAXSOCKBUF)
    {
      LOG (llevError, "Trying to send a buffer beyond properly size, len =%d\n", msg->length ());
      /* Almost certainly we've overflowed a buffer, so quite now to make
       * it easier to debug.
       */
      abort ();
    }

  sbuf[0] = ((uint32) (msg->length ()) >> 8);
  sbuf[1] = ((uint32) (msg->length ())     );

  //TODO: single write, or writev
  ns->send (sbuf, 2);
  ns->send (msg->buf, msg->length ());
}

/******************************************************************************
 *
 * statistics logging functions.
 *
 ******************************************************************************/

#ifdef CS_LOGSTATS

/* cst_tot is for the life of the server, cst_last is for the last series of
 * stats
 */
CS_Stats cst_tot, cst_lst;

/**
 * Writes out the gathered stats.  We clear cst_lst.
 */
void
write_cs_stats (void)
{
  time_t now = time (NULL);

  /* If no connections recently, don't both to log anything */
  if (cst_lst.ibytes == 0 && cst_lst.obytes == 0)
    return;

  /* CSSTAT is put in so scripts can easily find the line */
  LOG (llevInfo, "CSSTAT: %.16s tot %d %d %d %d inc %d %d %d %d\n",
       ctime (&now), cst_tot.ibytes, cst_tot.obytes, cst_tot.max_conn,
       now - cst_tot.time_start, cst_lst.ibytes, cst_lst.obytes, cst_lst.max_conn, now - cst_lst.time_start);
  cst_lst.ibytes = 0;
  cst_lst.obytes = 0;
  cst_lst.time_start = now;
}
#endif