#include "kernel/types.h"
#include "user/user.h"

#define MAX 36
#define FIRST_PRIME 2

int
generate_natural(); // -> out_fd
int
prime_filter(int in_fd, int prime); // -> out_fd

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

  int in = generate_natural();
  while (read(in, &prime, sizeof(int))) {
    // printf("prime %d: in_fd: %d\n", prime, in);  // debug
    printf("prime %d\n", prime);
    in = prime_filter(in, prime);
  }

  close(in);

  exit(0);
}

int
generate_natural()
{
  int out_pipe[2];

  pipe(out_pipe);

  if (!fork()) {
    for (int i = FIRST_PRIME; i < MAX; i++) {
      write(out_pipe[1], &i, sizeof(int));
    }
    close(out_pipe[1]);

    exit(0);
  }

  close(out_pipe[1]);

  return out_pipe[0];
}

int
prime_filter(int in_fd, int prime)
{
  int num;
  int out_pipe[2];

  pipe(out_pipe);

  if (!fork()) {
    while (read(in_fd, &num, sizeof(int))) {
      if (num % prime) {
        write(out_pipe[1], &num, sizeof(int));
      }
    }
    close(in_fd);
    close(out_pipe[1]);

    exit(0);
  }

  close(in_fd);
  close(out_pipe[1]);

  return out_pipe[0];
}