#include "csapp.h"

#define TICK_EVERY 3

int main(int argc, char**argv) {
  char *portno;
  struct addrinfo hints, *addrs;
  char host[256], serv[32];
  int s;
  int counter = 0;

  if (argc != 2)
    app_error("need <port>");

  portno = argv[1];

  memset(&hints, 0, sizeof(struct addrinfo));
  hints.ai_family = AF_INET;        /* Request IPv4 */
  hints.ai_socktype = SOCK_DGRAM;   /* Accept UDP connections */
  hints.ai_flags = AI_PASSIVE;      /* ... on any IP address */
  Getaddrinfo(NULL, portno, &hints, &addrs);

  s = Socket(addrs->ai_family, addrs->ai_socktype, addrs->ai_protocol);
  Bind(s, addrs->ai_addr, addrs->ai_addrlen);
  Freeaddrinfo(addrs);

  printf("Ticking at %d-second boundaries\n", TICK_EVERY);
  while (1) {
    struct timeval now;
    struct timespec delay;
    long now_s;

    char buffer[MAXBUF];
    size_t amt;
    struct sockaddr_in from_addr;
    unsigned int from_len = sizeof(from_addr);
    amt = Recvfrom(s, buffer, MAXBUF, 0,
                   (struct sockaddr *)&from_addr, &from_len);

    if (Fork() == 0) {
      gettimeofday(&now, NULL);
      if ((now.tv_usec == 0)
	  && ((now.tv_sec % TICK_EVERY) == 0)) {
	delay.tv_sec = TICK_EVERY;
	delay.tv_nsec = 0;
      } else {
	delay.tv_sec = (TICK_EVERY - 1 - (now.tv_sec % TICK_EVERY));
	delay.tv_nsec = (1000000 - now.tv_usec) * 1000;
      }

      while (nanosleep(&delay, &delay)) { }
    
      gettimeofday(&now, NULL);
      now_s = now.tv_sec;

      amt = Sendto(s, &now_s, 8, 0,
		   &from_addr, from_len);
      
      printf("tick %ld\n", now_s);

      return 0;
    }

    /* Note: we're not reaping the child process ID here, but we
       should. A good stretagy is to use a SIGCHLD handler to reap
       process IDS. */
  }
}