/*
** selectserver.c -- a cheezy multiperson chat server (beej.us/guide/bgnet/)
*/

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

#define PORT 9034   // port we're listening on

int main(void)
{
    fd_set master;   // master file descriptor list
    fd_set read_fds; // temp file descriptor list for select()
    struct sockaddr_in myaddr;     // server address
    struct sockaddr_in remoteaddr; // client address
    int fdmax;        // maximum file descriptor number
    int listener;     // listening socket descriptor
    int newfd;        // newly accept()ed socket descriptor
    char buf[256];    // buffer for client data
    int nbytes;
    int yes=1;        // for setsockopt() SO_REUSEADDR, below
    socklen_t addrlen;
    int i, j;

    FD_ZERO(&master);    // clear the master and temp sets
    FD_ZERO(&read_fds);

    // get the listener
    if ((listener = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }

    // lose the pesky "address already in use" error message
    if (setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &yes,
                                                        sizeof(int)) == -1) {
        perror("setsockopt");
        exit(1);
    }

    // bind
    myaddr.sin_family = AF_INET;
    myaddr.sin_addr.s_addr = INADDR_ANY;
    myaddr.sin_port = htons(PORT);
    memset(myaddr.sin_zero, '\0', sizeof myaddr.sin_zero);
    if (bind(listener, (struct sockaddr *)&myaddr, sizeof myaddr) == -1) {
        perror("bind");
        exit(1);
    }

    // listen
    if (listen(listener, 10) == -1) {
        perror("listen");
        exit(1);
    }

    // add the listener to the master set
    FD_SET(listener, &master);

    // keep track of the biggest file descriptor
    fdmax = listener; // so far, it's this one

    // main loop
    for(;;) {
        read_fds = master; // copy it
        if (select(fdmax+1, &read_fds, NULL, NULL, NULL) == -1) {
            perror("select");
            exit(1);
        }

        // run through the existing connections looking for data to read
        for(i = 0; i <= fdmax; i++) {
            if (FD_ISSET(i, &read_fds)) { // we got one!!
                if (i == listener) {
                    // handle new connections
                    addrlen = sizeof remoteaddr;
                    if ((newfd = accept(listener, (struct sockaddr *)&remoteaddr,
                                                               &addrlen)) == -1) { 
                        perror("accept");
                    } else {
                        FD_SET(newfd, &master); // add to master set
                        if (newfd > fdmax) {    // keep track of the maximum
                            fdmax = newfd;
                        }
                        printf("selectserver: new connection from %s on "
                            "socket %d\n", inet_ntoa(remoteaddr.sin_addr), newfd);
                    }
                } else {
                    // handle data from a client
                    if ((nbytes = recv(i, buf, sizeof buf, 0)) <= 0) {
                        // got error or connection closed by client
                        if (nbytes == 0) {
                            // connection closed
                            printf("selectserver: socket %d hung up\n", i);
                        } else {
                            perror("recv");
                        }
                        close(i); // bye!
                        FD_CLR(i, &master); // remove from master set
                    } else {
                        // we got some data from a client
                        for(j = 0; j <= fdmax; j++) {
                            // send to everyone!
                            if (FD_ISSET(j, &master)) {
                                // except the listener and ourselves
                                if (j != listener && j != i) {
                                    if (send(j, buf, nbytes, 0) == -1) {
                                        perror("send");
                                    }
                                }
                            }
                        }
                    }
                } // it's SO UGLY!
            }
        }
    }
    
    return 0;
}