#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <time.h>

#define ERR(source) (fprintf(stderr,"%s:%d\n",__FILE__,__LINE__),\
                     perror(source),kill(0,SIGKILL),\
                         exit(EXIT_FAILURE))

volatile sig_atomic_t last_signal = 0;
int count_rec = 0;

void sethandler( void (*f)(int), int sigNo) {
    struct sigaction act;
    memset(&act, 0, sizeof(struct sigaction));
    act.sa_handler = f;
    if (-1==sigaction(sigNo, &act, NULL)) ERR("sigaction");
}

void sig_handler(int sig) {
    last_signal = sig;
}

void sigusr2_handler(int sig){
    last_signal = sig;
    count_rec++;

}

void sigchld_handler(int sig) {
    pid_t pid;
    for(;;){
        pid=waitpid(0, NULL, WNOHANG);
        if(pid==0) return;
        if(pid<=0) {
            if(errno==ECHILD) return;
            ERR("waitpid");
        }
    }
}

void child_work( int m, int p){

    int count = 0;
    struct timespec t = {0, m*10000};
    while(1){
        for(int i=0; i<p; i++){
            nanosleep(&t,NULL);
            if(kill(getppid(),SIGUSR1)) ERR("kill");
            }

    if(kill(getppid(),SIGUSR2)) ERR("kill");
    count++;
    printf("[%d] sent %d SIGUSR2\n", getpid(), count);
    }




}


void usage(char *name){
    fprintf(stderr,"USAGE: %s m  p\n",name);
    fprintf(stderr,"m - number of 1/1000 milliseconds between signals [1,999], i.e. one milisecond maximum\n");
    fprintf(stderr,"p - after p SIGUSR1 send one SIGUSER2  [1,999]\n");
    exit(EXIT_FAILURE);
}

void parent_work(sigset_t oldmask){

    while(1){

        last_signal=0;
        while(last_signal!=SIGUSR2){
            sigsuspend(&oldmask);
            }

        printf("[PARENT] received %d SIGURS\n", count_rec);
        }


}


int main(int argc, char**argv) {

int m,p;
if(argc!=3) usage(argv[0]);

m = atoi(argv[1]);
p = atoi(argv[2]);
if(m<=0 || m>999 || p <=0 || p>999) usage(argv[0]);

sethandler(sigchld_handler,SIGCHLD);
sethandler(sig_handler,SIGUSR1);
sethandler(sigusr2_handler,SIGUSR2);

sigset_t mask,omask;
sigemptyset(&mask);
sigaddset(&mask,SIGUSR1);
sigaddset(&mask,SIGUSR2);
sigprocmask(SIG_BLOCK, &mask, &omask);

pid_t pid;
if((pid=fork())<0) ERR("fork");


if(pid == 0){
    child_work(m,p);
}
else{

    parent_work(omask);
    while(wait(NULL)>0);
}

sigprocmask(SIG_UNBLOCK,&mask,NULL);
return (EXIT_SUCCESS);
}