#include <stdio.h>
#include <sys/select.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#define _GNU_SOURCE
#include <sched.h>

#define BUF_SIZE 512
#define MAX_FDS  1024

int *all_fds;

int handle_client(void *arg)
{
    int myfd = (int) arg;   /* the file descriptor associated with this client */
    char data[BUF_SIZE];    /* the buffer we use to store the data we receive from the client */
    int nbytes;             /* number of bytes we read from the socket */
    int i;

    /* zero out the buffer */
    memset(data, '\0', BUF_SIZE);

    while (1)
    {
        /* this will block until we receive some data */
        nbytes = read(myfd, data, BUF_SIZE-1);

        if (nbytes == -1)
        {   /* error */
            perror("read");
            exit(1);
        }
        else if (nbytes == 0)
        {   /* client disconnected */
            fprintf(stderr, "[%d] socket %d closed connection\n", getpid(), myfd);

            /* release the file descriptor */
            all_fds[myfd] = -1;

            /* terminate the child */
            exit(0);
        }
        else
        {
            /* print the message */
            data[nbytes - 1] = '\0';
            printf("[%d] - %s\n", getpid(), data);

            /* transmit the message to everyone */
            for (i = 0; i < MAX_FDS; i++)
            {
                if (all_fds[i] != myfd && all_fds[i] != -1)
                {
                    if (write(all_fds[i], data, nbytes) == -1)
                        fprintf(stderr, "write error i is %d, all_fds[i] is %d\n", i, all_fds[i]);
                }
            }
        }
    }
    return 0;
}

int main(int argc, char *argv[])
{
    int listen_fd;                  /* File descriptor for listening */
    struct sockaddr_in addr;        /* Struct that holds server address */
    struct sockaddr_in cli_addr;    /* Struct that holds client address */
    socklen_t cli_addrlen = sizeof(cli_addr);
    int client_fd, shmid, i;
    key_t key;

    key    = ftok("fork-server",'R');
    shmid  = shmget(key, MAX_FDS * sizeof(int), 0666 | IPC_CREAT);
    all_fds = (int *)shmat(shmid, (void *)0, 0);

    /* initialize all_fds with -1 */
    for (i = 0; i < MAX_FDS; i++)
        all_fds[i] = -1;

    /* initialize the struct with the server address */
    addr.sin_family      = AF_INET;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_port        = htons(1234);
    memset(addr.sin_zero, '\0', sizeof(addr.sin_zero));

    /* Create the listening socket */
    listen_fd = socket(PF_INET, SOCK_STREAM, 0);

    /* Assign server address to the socket */
    bind(listen_fd, (struct sockaddr *)&addr, sizeof(addr));

    /* Start listening for connections */
    listen(listen_fd, 10);

    for(;;)
    {
        /* accept blocks until we have a new connection */
        client_fd = accept(listen_fd, (struct sockaddr *)&cli_addr, &cli_addrlen);

        all_fds[client_fd] = client_fd;

        clone(handle_client, (void **) (malloc(0x10000) + 0xFFFC), CLONE_FILES, (void *)client_fd);
    }
    return 0;
}