// client_udp_third.c

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

#define BUF_SIZE 4096
#define END_MARKER "END_OF_TRANSMISSION"

int main(int argc, char *argv[]) {
    if (argc < 4) {
        fprintf(stderr,
                "Usage: %s <server_ip> <server_port> <input_file>\n",
                argv[0]);
        fprintf(stderr,
                "Example: %s 127.0.0.1 5000 input.txt\n",
                argv[0]);
        return -1;
    }

    const char *server_ip = argv[1];
    const char *server_port = argv[2];
    const char *input_path = argv[3];

    char *endptr = NULL;
    errno = 0;
    long port_long = strtol(server_port, &endptr, 10);
    if (errno != 0 || endptr == server_port || *endptr != '\0' ||
        port_long <= 0 || port_long > 65535) {
        fprintf(stderr, "ERROR: invalid port '%s'\n", server_port);
        return -1;
    }
    int port = (int) port_long;

    FILE *fin = fopen(input_path, "r");
    if (!fin) {
        perror("fopen(input_file)");
        return -1;
    }

    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("socket");
        fclose(fin);
        return -1;
    }

    struct sockaddr_in servaddr;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(port);

    if (inet_pton(AF_INET, server_ip, &servaddr.sin_addr) != 1) {
        fprintf(stderr, "ERROR: invalid IP address '%s'\n", server_ip);
        close(sockfd);
        fclose(fin);
        return -1;
    }

    char buf[BUF_SIZE];

    for (;;) {
        size_t n = fread(buf, 1, sizeof(buf), fin);
        if (n > 0) {
            ssize_t sent = sendto(sockfd,
                                  buf,
                                  n,
                                  0,
                                  (struct sockaddr *) &servaddr,
                                  sizeof(servaddr));
            if (sent < 0 || (size_t) sent != n) {
                perror("sendto");
                close(sockfd);
                fclose(fin);
                return -1;
            }
        }

        if (n < sizeof(buf)) {
            if (ferror(fin)) {
                perror("fread");
                close(sockfd);
                fclose(fin);
                return -1;
            }
            break;
        }
    }

    if (fclose(fin) == EOF) {
        perror("fclose(input_file)");
    }

    ssize_t sent = sendto(sockfd,
                          END_MARKER,
                          strlen(END_MARKER),
                          0,
                          (struct sockaddr *) &servaddr,
                          sizeof(servaddr));
    if (sent < 0 || (size_t) sent != strlen(END_MARKER)) {
        perror("sendto(END_MARKER)");
        close(sockfd);
        return -1;
    }

    printf("File '%s' sent to %s:%d, END marker transmitted.\n",
           input_path, server_ip, port);

    close(sockfd);

    return 0;
}