#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

int p[2];//pipe

void sigHandler (int sig) {
    char c;
    switch (sig) {
        case SIGUSR1:
            c = '1';
        break;
        case SIGUSR2:
            c = '2';
        break;
        case SIGALRM:
            c = '0';
        break;
        case SIGSTOP:
            exit (0);
        break;
    }
    write(p[1], &c, sizeof(char));
}


int main(int argc, char **argv) {
    int signals[3], sig, i;
    for (i=0; i< 3; i++) {
        signals[i] =0;
    }
    pid_t pid;
    char csig;
    pipe(p);

    /*fork code*/
    pid = fork();

    /*parent*/
    if (pid) {
        close(p[1]);
        int proceed = 1;

        /*cycle keeps on indefinitely*/
        while (proceed) {
            sleep(15); //increased the time so I have time to send signals
            while (read(p[0], &csig, sizeof(char)) > 0) {
                sig=atoi(&csig);
                signals[sig]++;

                /*if alternating sigals, error*/
                if (signals[1] && signals[2]) {
                    printf("Error: alternating SIGUSR1 and SIGUSR2n%dt%dn", signals[1], signals[2]);

                }
                /*if 2 consecutive signals, success*/
                if (signals[sig] == 2) {
                    printf("Success: two consecutive SIGUSR1 or SIGUSR2n");
                }
                /*if three consecutive signals, exit*/
                if (signals[sig] == 3) {
                    kill(pid, SIGSTOP);
                    proceed = 0;
                    break;
                }
                /*make 0 any non repeating signal != sig*/
                for(i = 0; i< 3; i++) {
                    if (i != sig) {
                        signals[i] = 0;
                    }
                }
            }
        }
    /*child*/
    } else {
        close(p[0]);
        signal(SIGUSR1, sigHandler);
        signal(SIGUSR2, sigHandler);
        signal(SIGALRM, sigHandler);
        signal(SIGSTOP, sigHandler);
        while (1) {
            sleep(5); //no need to do anything else
        }
        exit(1);

    }
    return 0;
}