#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <time.h>

#include <fcntl.h>

// Receive an array of random numbers through FIFO from another process

// Calculate the sum and send it back through FIFO to that process

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

    // read numbers from process

    // calculate sum

    // send sum back

    int a2b = open("./a2b", O_RDONLY);

    if(-1 == a2b) {

        perror("Error on opening fifo a2b");

        exit(1);

    }

    int b2a = open("./b2a", O_WRONLY);

    if(-1 == b2a) {

        close(a2b);

        perror("Error on opening fifo b2a");

        exit(1);

    }

    int sum = 0;

    int nr;

    int n;

    if(-1 == read(a2b, &n, sizeof(int))) {

        perror("Error reading number of elems");

        close(a2b);

        close(b2a);

        exit(1);

    }

    for(int i = 0; i < n; i++) {

        if(-1 == read(a2b, &nr, sizeof(int))) {

            perror("Error reading number");

            close(a2b);

            close(b2a);

            exit(1);

        }

        sum += nr;

    }

    if(-1 == write(b2a, &sum, sizeof(int))) {

        perror("Error writing sum to parent");

        close(a2b);

        close(b2a);

        exit(1);

    }

    close(a2b);

    close(b2a);

    return 0;

}