#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <stdbool.h>
#include <sys/time.h>

#define COUNT 10

int right = 0;
int wrong = 0;
bool timed_out;

void SIGALRM_handler(int signo);

int main(void)
{
    struct itimerval tval;
    char string[BUFSIZ];

    timerclear(&tval.it_interval);
    timerclear(&tval.it_value);
    tval.it_value.tv_sec = 2;    // 2 second timeout

    signal(SIGALRM, SIGALRM_handler);
    
    for (int k = 1; k <= COUNT; k++)
    {
        int i = rand()%10;
        int j = rand()%10;
        printf("Problem #%d: Solve %d+%d=", k, i, j);

        timed_out = false;
        setitimer(ITIMER_REAL, &tval, NULL);  // set timer

        if (fgets(string, sizeof string, stdin) != NULL)
        {
            if (!timed_out)
            {
                setitimer(ITIMER_REAL, NULL, NULL);  // turn off timer

                if (atoi(string) == i + j)
                {
                    right++;
                    printf("Correct!\n");
                }
                else
                {
                    wrong++;
                    printf("Wrong!\n");
                }
            }
        } 
    }

    printf("\nRight: %d, wrong: %d\n", right, wrong);
    return 0;
}

void SIGALRM_handler(int sig)
{
    printf("\nTime's up!\nPress return for another problem.\n");

    wrong++;
    timed_out = true;
}