#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <net/if.h>
#include <time.h>

#define BROADCAST_PORT 5000
#define MESSAGE "Hello from broadcast!"

void error_exit(const char *msg) {
    perror(msg);
    exit(EXIT_FAILURE);
}

void sleep_ms(int milliseconds) {
    struct timespec ts;
    ts.tv_sec = milliseconds / 1000;
    ts.tv_nsec = (milliseconds % 1000) * 1000000;
    nanosleep(&ts, NULL);
}

int main(int argc, char *argv[]) {
    if (argc != 3) {
        fprintf(stderr, "Usage: %s <interface> <period_ms>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    const char *iface = argv[1];
    int period_ms = atoi(argv[2]);

    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0)
        error_exit("socket");

    // Enable broadcast
    int broadcastEnable = 1;
    if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcastEnable, sizeof(broadcastEnable)) < 0)
        error_exit("setsockopt SO_BROADCAST");

    // Bind to a specific interface
    if (setsockopt(sockfd, SOL_SOCKET, SO_BINDTODEVICE, iface, strlen(iface)) < 0)
        error_exit("setsockopt SO_BINDTODEVICE");

    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(BROADCAST_PORT);
    addr.sin_addr.s_addr = inet_addr("255.255.255.255");

    while (1) {
        ssize_t sent = sendto(sockfd, MESSAGE, strlen(MESSAGE), 0,
                              (struct sockaddr *)&addr, sizeof(addr));
        if (sent < 0)
            perror("sendto");

        sleep_ms(period_ms);
    }

    close(sockfd);
    return 0;
}