/*
 *  multiplexed_echo_server.c -- modified from APUE book (tcp select echo server)
 */

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

#include "socket.h"

#define PORT 2345  // default port

int main(int argc, char *argv[])
{
   int   i, n, imax, fdmax, csock, conn, sock; 
   int   nready, client[FD_SETSIZE];
   fd_set master, cset;
   char   buf[256];

   sock = get_ssock(PORT, "tcp"); // get a server TCP socket at PORT

   fdmax = sock;

   imax = -1;

   for ( i = 0; i < FD_SETSIZE; i++ ) {
      client[i] = -1;
   }

   FD_ZERO(&master);
   FD_ZERO(&cset);

   FD_SET(sock, &master);
   
   for(;;) {
      cset = master;

      nready = select(fdmax+1, &cset, NULL, NULL, NULL);

      if ( FD_ISSET(sock, &cset) ) { // we have a new client connection
         struct  sockaddr_in caddr;
         socklen_t clen = sizeof(caddr);
         conn = accept(sock, (struct sockaddr *) &caddr, &clen);

         for ( i = 0; i < FD_SETSIZE; i++ ) {  // find a free slot
            if ( client[i] < 0 ) {
               client[i] = conn;   // save descriptor
               break;
            }
         }

         if ( i == FD_SETSIZE ) {  // no slot found
            fprintf(stderr, "Too many connections. quitting...\n");
            exit(EXIT_FAILURE);
         }

         FD_SET(conn, &master);

         if ( fdmax < conn ) {
            fdmax = conn;
         }

         if ( imax < i ) {
            imax = i; 
         }

         if ( --nready <= 0 ) { // nothing ready left for reading
            continue ; // the for loop 
         }
      }

      for ( i = 0; i <= imax; i++ ) {  // only client connections left for processing
         if ( (csock = client[i]) < 0 ) {
            continue; 
         }

         if ( FD_ISSET(csock, &cset) ) {
            if ( (n = recv(csock, buf, sizeof(buf), 0)) <= 0 ) {
               close(csock);
               FD_CLR(csock, &master);
               client[i] = -1;
            } else {
               write(csock, buf, n);
            }

            if ( --nready == 0 ) {
                break;
            }
         }
      }
   }
}