#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <sys/stat.h>

#include <time.h>

#include <fcntl.h>

// Send an array of random numbers through FIFO to another process

// The other process calculates the sum and sends it back through FIFO

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

    if(-1 == mkfifo("./a2b", 0600)) {

        perror("Error creating fifo a2b");

        exit(1);

    }

    if(-1 == mkfifo("./b2a", 0600)) {

        perror("Error creating fifo b2a");

        exit(1);

    }

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

    if(-1 == a2b) {

        perror("Error on opening fifo a2b");

        exit(1);

    }

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

    if(-1 == b2a) {

        close(a2b);

        perror("Error on opening fifo b2a");

        exit(1);

    }

    srandom(getpid());

    int n;

    printf("n=");

    scanf("%d", &n);

    if(n > 0) {

        int *arr = malloc(sizeof(int) * n);

        // initialize array with random values

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

            arr[i] = random() % 100;

            printf("a[%d] = %d\n", i, arr[i]);

        }

        // send array to other process

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

            perror("Error writing array size");

            free(arr);

            close(a2b);

            close(b2a);

            exit(1);

        }

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

            if(-1 == write(a2b, &arr[i], sizeof(int))) {

                perror("Error writing array");

                free(arr);

                close(a2b);

                close(b2a);

                exit(1);

            }

        }

        free(arr);

        int sum = 0;

        // read sum

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

            perror("Error reading sum");

            close(a2b);

            close(b2a);

            exit(1);

        }

        printf("sum = %d\n", sum);

    }

    close(a2b);

    close(b2a);

    unlink("./a2b");

    unlink("./b2a");

    return 0;

}