#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <unistd.h>

#define MAX_EVENTS 1024
#define TIMEOUT 250
#define PORT 80

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <subnet (e.g., 192.168.1)>\n", argv[0]);
        return EXIT_FAILURE;
    }

    struct sockaddr_in addr;
    struct epoll_event ev, events[MAX_EVENTS];
    int epoll_fd = epoll_create1(0);

    if (epoll_fd == -1) {
        perror("epoll_create1");
        return EXIT_FAILURE;
    }

    for (int i = 1; i < 255; i++) {
        char ip[16];
        snprintf(ip, sizeof(ip), "%s.%d", argv[1], i);

        int sock = socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
        if (sock < 0) {
            perror("socket");
            continue;  // Skip to next
        }

        memset(&addr, 0, sizeof(addr));
        addr.sin_family = AF_INET;
        addr.sin_port = htons(PORT);
        inet_pton(AF_INET, ip, &addr.sin_addr);

        if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
            if (errno != EINPROGRESS) {
                perror("connect");
                close(sock);
                continue;  // Skip to next
            }
        }

        ev.data.fd = sock;
        ev.events = EPOLLERR | EPOLLHUP | EPOLLOUT;

        if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, sock, &ev) == -1) {
            perror("epoll_ctl");
            close(sock);
            continue;  // Skip to next
        }
        //        printf("Trying to connect to %s...\n", ip);
    }

    while (1) {
        // TODO: Timout nicht bei jedem Poll von vorne beginnen lassen
        int n = epoll_wait(epoll_fd, events, MAX_EVENTS, TIMEOUT);
        if (n < 0) {
            perror("epoll_wait");
            break;
        }

        for (int i = 0; i < n; i++) {
            if (events[i].events & EPOLLOUT) {
                char ip[16];
                if (getpeername(events[i].data.fd, (struct sockaddr *)&addr, (socklen_t *)&(socklen_t){sizeof(addr)}) == 0) {
                    inet_ntop(AF_INET, &addr.sin_addr, ip, sizeof(ip));
                    printf("Successful connection to %s\n", ip);
                }
                close(events[i].data.fd);
            } else {
                perror("Error in epoll event");
                close(events[i].data.fd);
            }
        }

        if (n == 0) {
            printf("Timeout reached. Stopping.\n");
            break;
        }
    }

    close(epoll_fd);
    return EXIT_SUCCESS;
}