#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdbool.h>
#include <sys/wait.h>
#include <unistd.h>

int load(FILE *f_proc_stat)
{

    //declaration of variables to be read from /proc/stat
    const char cpu[3];
    int user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice;

    //variables to be computed in the function
    int cpu_idle, cpu_prev_idle;
    int cpu_nonidle, cpu_prev_nonidle;
    int prev_total, total, total_d, idle_d;
    int cpu_percentage;
    char test[255];

    fgets(test, 255, f_proc_stat);


        sscanf(test, "%s %d %d %d %d %d %d %d %d %d %d", cpu, &user, &nice, &system, &idle, &iowait, &irq, &softirq, &steal, &guest, &guest_nice);

        cpu_prev_nonidle = user + nice + system + irq + softirq + steal;
        cpu_prev_idle = idle + iowait;

        printf("cpu_prev_nonidle is %d\n", cpu_prev_nonidle);


        sleep(1);

    fgets(test, 255, f_proc_stat);

        sscanf(test, "%s %d %d %d %d %d %d %d %d %d %d", cpu, &user, &nice, &system, &idle, &iowait, &irq, &softirq, &steal, &guest, &guest_nice);
        /*fscanf(f_proc_stat, "%s %d %d %d %d %d %d %d %d %d %d",
            cpu, &user, &nice, &system, &idle, &iowait, &irq, &softirq,
            &steal, &guest, &guest_nice);*/

        cpu_nonidle = user + nice + system + irq + softirq + steal;
        cpu_idle = idle + iowait;

        prev_total = cpu_prev_idle + cpu_prev_nonidle;        total = cpu_idle + cpu_nonidle;

        //differentiate
        total_d = total - prev_total;
        idle_d = cpu_idle - cpu_prev_idle;

        cpu_percentage = (total_d - idle_d)/total_d;

    return cpu_percentage;
}


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

    FILE *f_shell_command;
    int refresh_time = 5;
    bool repeat;

                        if ((f_shell_command = fopen("/proc/stat", "r")) == NULL)
                        {
                            fprintf(stderr, "ERROR: Unable to open /proc/stat\n");
                            return 1;
                        }

                        pid_t pid;
                        int cpu_percentage;

                        pid = fork();
                        if (pid == 0)
                        {
                            while(1)
                            {
                                cpu_percentage = load(f_shell_command);
                                printf("cpu percentage is %d\n", cpu_percentage);
                            }
                        }
                        else if (pid < 0)
                        {
                            fprintf(stderr, "Unable to open process\n");
                            return 1;
                        }
                        else
                        {
                            do {
                                printf("cpu percentage in while is %d\n", cpu_percentage);
                                sleep(refresh_time);
                            } while(repeat);

                        }

                        fclose(f_shell_command);
}