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

#define BUFSIZE 42000

void error(char *msg) {
	write(2, msg, strlen(msg));
	exit (1);
}

void broadcast(char *buf, fd_set *set, int max_fd, int server_fd, int sender_fd) {
	for(int i = 0; i <= max_fd; i++) {
		if (i == server_fd)
			continue;
		if (i == sender_fd)
			continue;
		if (FD_ISSET(i, set))
			send(i, buf, strlen(buf), 0);
	}
}

int main(int ac, char **av) {
	int									server_fd;
	int									client_fd;
	int									client_id;
	int									port;
	int									max_fd;
	int									ret;
	struct sockaddr_in	addr;
	socklen_t						addr_len;
	fd_set							fdset;
	fd_set							rdset;
	char								buf[BUFSIZE];
	char								tmp_buf[BUFSIZE];
	int									clients[FD_SETSIZE];

	if (ac != 2)
		error("Fatal error\n");
	port = atoi(av[1]);
	addr_len = sizeof(addr);

	// socket create and verification 
	server_fd = socket(AF_INET, SOCK_STREAM, 0);
	if (server_fd == -1)
		error("Fatal error\n");
	bzero(&addr, addr_len);
	addr.sin_family = AF_INET; 
	addr.sin_addr.s_addr = htonl(2130706433); //127.0.0.1
	addr.sin_port = htons(port); 
	if ((bind(server_fd, (const struct sockaddr *)&addr, addr_len)) == -1)
		error("Fatal error\n");
	if (listen(server_fd, 10) == -1)
		error("Fatal error\n");

	FD_ZERO(&fdset);
	FD_SET(server_fd, &fdset);
	max_fd = server_fd;
	client_id = 0;

	while(1) {
		rdset = fdset;

		select(max_fd + 1, &rdset, NULL, NULL, NULL);

		if (FD_ISSET(server_fd, &rdset)) {
			client_fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
			FD_SET(client_fd, &fdset);
			clients[client_fd] = client_id;
			if (client_fd > max_fd)
				max_fd = client_fd;
			sprintf(buf, "server: client %d just arrived\n", client_id);
			broadcast(buf, &fdset, max_fd, server_fd, client_fd);
			client_id++;
		}

		client_fd = 0;
		while(client_fd <= max_fd) {
			if (FD_ISSET(client_fd, &rdset)) {
				bzero(buf, BUFSIZE);
				ret = recv(client_fd, buf, BUFSIZE, 0);
				if (ret == 0) {
					sprintf(buf, "server: client %d just left\n", clients[client_fd]);
					broadcast(buf, &fdset, max_fd, server_fd, client_fd);
					FD_CLR(client_fd, &fdset);
				}
				else if (ret > 0) {
					sprintf(tmp_buf, "client %d: %s", clients[client_fd], buf);
					broadcast(tmp_buf, &fdset, max_fd, server_fd, client_fd);
				}
			}
			client_fd++;
		}
	}

	return (0);
}