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

#define MAX_PROC 8
#define SIZE 500
#define READ 0
#define WRITE 1

static int numArr[SIZE];

int getSum(int id) {
  int sum = 0;
  for (size_t i = id; i < SIZE; i+=MAX_PROC)
    sum += numArr[i];
  return sum;
}


void populateArray() {
    for (size_t i = 1; i <= SIZE; i++)
    {
        numArr[i] = i;
    }
}

void waitChildren() {
    pid_t child;
    while((child = wait(NULL)) > 0) {
        //printf("Child %d exited.\n", child);
    }
}

int main(int argc, char** argv) {
    int expected = (SIZE * (SIZE + 1)) / 2;
    pid_t child[MAX_PROC];
    int fd[2], sums[MAX_PROC], totalSum;

    if (pipe(fd) < 0) {
     perror("pipe");
     exit(EXIT_FAILURE);
    }

    populateArray();

    for (size_t i = 0; i < MAX_PROC; i++)
    {
        child[i] = fork();
        if(child[i] < 0) {
            perror("fork");
            exit(EXIT_FAILURE);
        }
        else if(child[i] == 0) {
            int sum=0;
            close(fd[READ]);
            for(int j = i; j < SIZE  ;j+=MAX_PROC) {
                sum += numArr[j];
            }
            printf("The sum for process %d is %d\n",i, sum);
            write(fd[WRITE], &sum, sizeof(sum));
            exit(0);
        }
    }

    waitChildren();
    close(fd[WRITE]);
    for(int i = 0; i < MAX_PROC; i++) {
        read(fd[READ], &sums, sizeof(sums));
    }

    for (int i = 0; i < MAX_PROC; i++)
    {
        totalSum += sums[i];
    }

    printf("Expected: %d\nTotal sum = %d\n", expected, totalSum);
    return 0;
}