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

#define MESSAGE_LENGHT 64
#define USER_LENGHT 16
#define BACKLOG 1

//Server side

int sfd,cfd;
int masterpid;

static void signal_close_socket(int);

int main(int argc, char* argv[]) {

 //Init Phase:
 int ssockfd, csockfd, PORT; //defining socket filedes for both server/client
 char buffer[MESSAGE_LENGHT];
 char myuser[USER_LENGHT] = "server1";
 char otheruser[USER_LENGHT];
 struct sockaddr_in saddr, caddr; //defining server/client address
 struct sigaction act;
 pid_t fpid, childpid = 0, sread = 0, swrite = 0;
 sigset_t set;
 socklen_t slen, clen; //defining server/client address lenght

 //getting the port
 PORT = atoi(argv[1]);

 //defining the master
 masterpid = fpid = getpid();

 //signal handling
 sigfillset(&set);
 act.sa_handler = &signal_close_socket;
 act.sa_mask = set;
 act.sa_flags = SA_RESTART;
 sigaction(SIGINT, &act, 0);

 //Socket phase:
 //checking if the socket is created with success.
 if((ssockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
    perror("socket");
    exit(EXIT_FAILURE);
 }

 sfd = ssockfd; //assigning the server filedes to sfd.

 //Defining a name for our socket, then binding it.
 //NAME DEFINING PHASE:
 saddr.sin_family = AF_INET; //adding the family address
 saddr.sin_port = htons(PORT); //converting port from host protocol to network protocol, then assigning to current port.
 saddr.sin_addr.s_addr = htonl(INADDR_ANY); //same as above, but with the loopback address.


 //now binding
 slen = sizeof(saddr); //size of the address of the server
 if(bind(ssockfd, (struct sockaddr*)&saddr, slen) == -1) {
    perror("bind");
    exit(EXIT_FAILURE);
 }

 //defining listening phase
 if(listen(ssockfd, BACKLOG) == -1) {
    perror("listen");
    exit(EXIT_FAILURE);

 }

 printf("Server: correctly loaded.\n");
 printf("Choose your username: ");
 scanf("%s",myuser);
 myuser[strlen(myuser)] = '\0';
 printf("Hello %s!\n",myuser);

 //loop forever
 while(1) {
    printf("Waiting for connections..\n");
    clen = sizeof(caddr);
    //accept a pending connection
    if((csockfd = accept(ssockfd, (struct sockaddr*)&caddr, &clen)) == -1) {
        perror("accept");
        exit(EXIT_FAILURE);
    } else {
        send(csockfd, &myuser, strlen(myuser)+1, 0);
        recv(csockfd, &otheruser, USER_LENGHT, 0);
        printf("Client %s connected.\n", otheruser);
    }

    cfd = csockfd; //assigning client filedes to cfd.

    //creating two process that will manage read and write respectively
    if((childpid = fork()) == 0) {
        sread=getpid();
    } else if (childpid > 0) {
        childpid = 0;
        if((childpid = fork()) == 0) {
            swrite = getpid();
        } else if (childpid < 0) {
            perror("fork");
            exit(EXIT_FAILURE);
         }
      } else {
        perror("fork");
        exit(EXIT_FAILURE);
       }

    while(1) {
        if(sread) {
            recv(csockfd, &buffer, MESSAGE_LENGHT, MSG_WAITALL);
            printf("%s: %s\n",otheruser,buffer);
            fflush(stdin);
        }

        if(swrite) {
            scanf("%s",buffer);
            send(csockfd, &buffer, MESSAGE_LENGHT, 0);
            fflush(stdin);
        }
    }

  }

}


static void signal_close_socket(int signo) {

 if(getpid() == masterpid) {
    printf("\nClosing server..\n");
    close(cfd);
    close(sfd);
    while(wait(NULL) != -1);
    exit(EXIT_SUCCESS);
 } else exit(EXIT_SUCCESS);

}