#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <unistd.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define MAX_EVENTS 1024
#define RESPONSE_MESSAGE "epoll event bundle data"

typedef struct _Session Session;
typedef struct _Driver {
	int (*read)(Session* session);
	int (*write)(Session* session);
	int (*close)(Session* session);
} Driver;
typedef struct _Session {
	Driver* driver;
	int fd;
	void* data;
} Session;

Driver server_driver;

void loop(int epoll) {
	struct epoll_event events[MAX_EVENTS] = {};
	while(1) {
		int nevent = epoll_wait(epoll, events, MAX_EVENTS, 30);
		if(nevent == -1) return;

		for(int i = 0; i < nevent; ++i) {
			struct epoll_event* e = &events[i];
			Session* session = e->data.ptr;
			if(session->driver->read)
				session->driver->read(session);
		}
	}
}

int server_read(Session* session) {
	struct sockaddr_in client_addr = {};
	socklen_t client_addrlen = sizeof(client_addr);
	int client = accept(session->fd, (struct sockaddr*)&client_addr, &client_addrlen);
	if(client == -1) return 1;

	ssize_t nwrite = write(client, session->data, sizeof(RESPONSE_MESSAGE));
	if(nwrite <= 0) return 2;

	close(client);

	return 0;
}

int main(int argc, char *argv[]) {
	int error = 0;

	int epoll = epoll_create1(0);
	if(epoll == -1) return 1;

	// Server Socket: Prepare socket
	int server = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
	if(server == -1) return 2;
	struct sockaddr_in server_addr = {};
	socklen_t server_addrlen = sizeof(server_addr);
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(61235);
	server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	error = bind(server, (const struct sockaddr*)&server_addr, server_addrlen);
	if(error) return 3;
	error = listen(server, 16);
	if(error) return 4;

	Session server_session = {};
	server_driver.read = server_read;
	server_session.driver = &server_driver;
	server_session.fd = server;
	server_session.data = RESPONSE_MESSAGE;

	// Server Socket: Register epoll event
	struct epoll_event server_event = {};
	server_event.events = EPOLLIN;
	server_event.data.ptr = &server_session;
	error = epoll_ctl(epoll, EPOLL_CTL_ADD, server, &server_event);
	if(error) return 5;

	// Start main loop
	loop(epoll);

	return 0;
}