#include <iostream>
#include <sys/resource.h>
#include <unistd.h>

using namespace std;

void NiceMe(int level);
void ChangePrio(pid_t myPID, int level);
void PrintPrio(pid_t pid);
void ActiveDelay(void);
void PrintLimits(void);

int main() {
 
     PrintLimits();

     pid_t myPID{getpid()};
     PrintPrio(myPID);
     ActiveDelay();

     ChangePrio(myPID, -1);
     ChangePrio(myPID, -19);
     ChangePrio(myPID, 10);


     PrintPrio(myPID);
     ActiveDelay();

     NiceMe(-5);
     NiceMe(2);

     PrintPrio(myPID);
     ActiveDelay();


     return 0;
}

void NiceMe(int level) {
     cout << endl;
     cout << "Calling nice(" << level << ") " << endl;
     if (-1 == nice(level)) {
        perror("\tError nice: ");
     } else {
        cout << "\tSuccess" << endl;
     }
}

void PrintLimits(void){
    rlimit limits;

    if(-1 == getrlimit(RLIMIT_NICE, &limits)) {
         perror("\tError getrlimit: ");
    } else {
        cout << endl;
        cout << "For this process, the nice limit is:" << endl;
        cout << "\tHard: " <<  limits.rlim_max << endl;
        cout << "\tSoft: " <<  limits.rlim_cur << endl;
    }
}

void ChangePrio(pid_t myPID, int level){
     cout << "Changing Priority to  " << level << endl;

     if (setpriority(PRIO_PROCESS, myPID, level) == -1) {
         perror("\tError, Set Priority : ");
     } else {
         cout << "\tSuccess" << endl;
     }
}

void PrintPrio(pid_t pid) {
     int myPriority;

     cout << endl;
     errno = 0;
     myPriority = getpriority(PRIO_PROCESS, pid);
     if (errno != 0) {
        perror("\tError, Get Proiority: ");
     } else {
         cout << "For process " << pid << " my priority is "
              << myPriority << endl;
     }
}

void ActiveDelay() {
     for(int j = 0; j < 3'000; ++j) {
         for(int i =0; i < 1'000'000; i++) {
            int k = i * i - i + i;
         }
     }
}