#include <iostream>
#include <unistd.h>
#include <sys/wait.h>
#include <cstdlib>
#include <ctime>

void random_task(int id) {
	srand(time(0));
	int delay=1+rand()%3;
	std::cout<<"PID:" <<getpid()<<"task "<<id<<" delay :"<<delay<<"s\n";
	sleep(delay);
}

int main() {
	int total_tasks=10;
	int k=4;
	int pipefd[2];
	pipe(pipefd);

	pid_t rootpid=getpid();

	//~~ create workers ~~
	for (int w=0;w<k;w++)
		fork();
	//~~workers assigned tasks
	if (getpid()!=rootpid) {
		close(pipefd[1]);
		int task;
		while(read(pipefd[0],&task,sizeof(task))>0)
		{
			random_task(task);
		}
		close(pipefd[0]);
		_exit(0);
	}
	//~~root pid
	for(int t=0;t<total_tasks;t++) {
		write(pipefd[1],&t,sizeof(t));
	}
	close(pipefd[1]);
	while(wait(0)>0);
	std::cout<<"all tasks completed \n";

	return 0;
}