#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>


void poll (int fd)
{
}

int valid_fn (unsigned char fn)
{
  switch (fn) {
  case 0x30:
  case 0x31:
  case 0x32:
  case 0x33:
  case 0x34:
  case 0x35:
  case 0x36:
  case 0x37:
  case 0x38:
  case 0x08:
  case 0x39:
  case 0x09:
  case 0x43:
  case 0x45:
  case 0x4E:
  case 0x4F:
  case 0x50:
  case 0x40:
  case 0x3F:
  case 0x23:
  case 0x26:
  case 0x41:
  case 0x58:
  case 0x4C:
  case 0x56:
  case 0x76:
  case 0x49:
    return 1;
  }

  return 0;
}


void ack (int fd)
{
  char buf[3];

  buf[0] = 0;
  buf[1] = 0x38;
  buf[2] = 0xff ^ buf[0] ^ buf[1];

  write (fd, buf, sizeof (buf));

}


void msg (char *account, char *event, char *ascii)
{
  printf ("%s %64s %s\n", account, event, ascii);
}


int rx_pkt (int fd, unsigned char *pkt, unsigned len)
{
  unsigned char parity = 0xff;
  unsigned i;

  static char account[65];
  static char event[65];
  static char ascii[65];



  for (i = 0; i < len; ++i)
    parity ^= pkt[i];

  if (parity) return -1;

  len--;


  switch (pkt[1]) {
  case 0x23:
    memcpy (account, &pkt[2], len - 2);
    account[len - 2] = 0;
    break;

  case 0x4e:
  case 0x4f:
    memcpy (event, &pkt[2], len - 2);
    event[len - 2] = 0;
    break;

  case 0x41:
    memcpy (ascii, &pkt[2], len - 2);
    ascii[len - 2] = 0;

    msg (account, event, ascii);
    break;
  }


  if (pkt[0] & 0x40) ack (fd);

  return 0;
}



int rx (int fd)
{
  static unsigned char pkt[67];
  static unsigned ptr;
  unsigned char byte;
  unsigned len;

  if (read (fd, &byte, 1) != 1) {
    ptr = 0;
    return -1;
  }

  pkt[ptr++] = byte;

  if (ptr > 2 && !valid_fn (pkt[1])) {
    ptr = 0;
    return 0;
  }

  len = pkt[0] & 0x3f;

  if (ptr == (len + 3)) {
    ptr = 0;
    return rx_pkt (fd, pkt, len + 3);
  }

  return 0;
}


int main (int argc, char *argv)
{
  struct sockaddr_in sin;
  struct timeval tv = {0};
  int rc;
  int fd;
  int afd = -1;
  fd_set rfds;
  fd_set wfds;


  fd = socket (PF_INET, SOCK_STREAM, 0);

  sin.sin_family = AF_INET;
  sin.sin_port = htons (10002);
  sin.sin_addr.s_addr = INADDR_ANY;

  bind (fd, (struct sockaddr *)&sin, sizeof (sin));

  listen (fd, 5);

  tv.tv_sec = 5;

  FD_ZERO (&wfds);

  for (;;) {

    FD_ZERO (&rfds);

    FD_SET (fd, &rfds);

    if (afd > 0)
      FD_SET (afd, &rfds);

    rc = select (afd > fd ? afd + 1 : fd + 1, &rfds, &wfds, NULL, &tv);

    if ((!rc)  && (afd > 0)) poll (afd);


    if (FD_ISSET (fd, &rfds)) {
      if (afd > 0) close (afd);

      afd = accept (fd, NULL, NULL);
    }

    if ((afd > 0) && (FD_ISSET (afd, &rfds))) {
      if (rx (afd)) {
        close (afd);
        afd = -1;
      }
    }

    if (!tv.tv_sec && !tv.tv_usec)
      tv.tv_sec = 5;




  }
}