#include <arpa/inet.h>
#include <errno.h>
#include <netdb.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

static int connect_ex(const char *host, int port) {
    struct addrinfo hints;
    struct addrinfo *result = NULL;
    char port_str[16];
    int fd = -1;
    int status = 0;

    snprintf(port_str, sizeof(port_str), "%d", port);

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;

    if (getaddrinfo(host, port_str, &hints, &result) != 0) {
        status = errno;
        printf("getaddrinfo failed (errno = %d)\n", status);
        return status;
    }

    fd = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
    if (fd < 0) {
        status = errno;
        printf("socket failed (errno = %d)\n", status);
        freeaddrinfo(result);
        return status;
    }

    int connect_result = connect(fd, result->ai_addr, result->ai_addrlen);
    if (connect_result != 0) {
        status = errno;
    }
    printf("connect returned %d (errno = %d)\n", connect_result, status);



    close(fd);
    freeaddrinfo(result);
    return status;
}

static bool is_port_in_use(int port, const char *host) {
    return connect_ex(host, port) == 0;
}

static int get_free_port(int port, const char *host) {
    while (is_port_in_use(port, host)) {
        port += 1;
    }
    return port;
}

int main(int argc, char **argv) {
    const char *host = "localhost";
    int port = 8000;
    char *end = NULL;

    if (argc > 1) {
        port = (int)strtol(argv[1], &end, 10);
        if (end == argv[1] || *end != '\0') {
            fprintf(stderr, "Invalid port: %s\n", argv[1]);
            return 1;
        }
    }

    if (argc > 2) {
        host = argv[2];
    }

    printf("Checking port %d, %s\n", port, host);

    if (is_port_in_use(port, host)) {
        printf("Port %d, %s is already in use. Finding a free port...\n", port, host);
        port = get_free_port(port, host);
    }

    printf("Using port %d, %s\n", port, host);
    return 0;
}