#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#include <signal.h>
#include <sys/wait.h>

int counter = 1;
volatile int flag = 0;
int arr[1000000];
int arrsize = 0;

// должен закрывать все открытые дескрипторы
void handler(int s) {
    for (int i = 0; i < arrsize; ++i) {
        kill(arr[i], SIGTERM);
    }
    while (wait(NULL) > 0);
    exit(0);
}

int main(int argc, char *argv[]) {
    struct sigaction sa = {};
    sa.sa_flags = SA_RESTART;
    sa.sa_handler = handler;
    sigaction(SIGTERM, &sa, NULL);

    int fd = socket(PF_INET, SOCK_STREAM, 0);
    if (fd < 0) {
        perror("socket");
        return 1;
    }

    int val = 1;
    setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
    setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &val, sizeof(val));

    struct sockaddr_in s1;
    s1.sin_family = AF_INET;
    s1.sin_port = htons(strtol(argv[1], NULL, 10));
    s1.sin_addr.s_addr = INADDR_ANY;
    int r = bind(fd, (struct sockaddr*) &s1, sizeof(struct sockaddr_in));
    if (r < 0) {
        perror("bind");
        return 1;
    }

    listen(fd, 5);

    ssize_t res;
    char buf[1024];

    while (1) {
        while (waitpid(-1, NULL, WNOHANG) > 0);

        struct sockaddr_in s2;
        socklen_t slen = sizeof(s2);
        int fd2 = accept(fd, (struct sockaddr*) &s2, &slen);

        // для каждого клиента создаем отдельный процесс
        if (!fork()) {
            arr[arrsize] = getpid();
            arrsize++;

            close(fd);
            int myNum = counter++;

            sprintf(buf, "%s\r\n", argv[2]);
            res = write(fd2, buf, strlen(buf));
            if (res <= 0) {
                exit(0);
            }
            sprintf(buf, "%d\r\n", myNum);
            res = write(fd2, buf, strlen(buf));
            if (res <= 0) {
                exit(0);
            }

            int maxNum;

            res = read(fd2, buf, sizeof(buf));
            if (res <= 0) {
                exit(0);
            }
            buf[res] = '\0';
            maxNum = strtol(buf, NULL, 10);

            while (1) {
                res = read(fd2, buf, sizeof(buf));
                if (res <= 0) {
                    exit(0);
                }
                buf[res] = '\0';

                int num = strtol(buf, NULL, 10);
                if (num > maxNum || num > INT_MAX - myNum) {
                    strcpy(buf, "-1\r\n");
                    res = write(fd2, buf, 4);
                    if (res <= 0) {
                        exit(0);
                    }
                    close(fd2);
                    return 0;
                } else {
                    sprintf(buf, "%d\r\n", num + myNum);
                    res = write(fd2, buf, strlen(buf));
                    if (res <= 0) {
                        exit(0);
                    }
                }
            }
        }
        close(fd2);
    }
    exit(0);
}