#include <cstring>
#include <iostream>
#include <sys/wait.h>
#include <unistd.h>

#define BUF_SIZE 10

int main(int argc, char *argv[]) {
  int p_fds[2];
  if (pipe(p_fds) == -1) {
    std::cerr << "Error: pipe() - " << strerror(errno) << std::endl;
    exit(1);
  }

  switch (int pid = fork()) {
  case -1:
    std::cerr << "Error: fork() failed - " << strerror(errno) << std::endl;
    exit(1);
    break;
  case 0:
    // Child
    std::cout << "Child with PID: " << getpid() << " executing..." << std::endl;
    // close unwated file descriptors - write descriptor of the pipe end
    close(p_fds[1]); // IMPORTANT
    char buf[BUF_SIZE];
    int n_read;
    std::cout << "Child with PID: " << getpid() << ", reading from parent..."
              << std::endl;
    while ((n_read = read(p_fds[0], buf, BUF_SIZE)) != 0) {
      if (n_read == -1) {
        std::cerr << "Error reading: " << strerror(errno) << std::endl;
        exit(1);
      }
      // Write to stdout
      write(STDOUT_FILENO, buf, n_read);
    }

    // Write \n to stdout
    write(STDOUT_FILENO, "\n", 1);
    std::cout << "Completed read by child with PID " << getpid() << std::endl;
    close(p_fds[0]); // IMPORTANT
    break;
  default:
    // Parent
    std::cout << "Parent with PID: " << getpid() << " executing..."
              << std::endl;
    // close unwated file descriptors - read descriptor of the pipe end
    close(p_fds[0]); // IMPORTANT
    // Random data
    char to_send[] = {"BErGgTYpK6"
                      "KoAGxKxIdz"
                      "y4KdQIcTx2"
                      "YfDVUIxmQA"
                      "t3k6ErdzfB"
                      "kBpAX4UpBE"
                      "qi9f45TeFZ"
                      "WUUgONJ94I"
                      "UKJqXYjGO2"
                      "8qCpR4zQPl"
                      "2M4dPnMLbd"
                      "XEwwtYsTo3"
                      "9g9GoJSqrz"
                      "vdRvhPXlzU"
                      "ZRYQ91B7lE"};
    size_t to_send_len = strlen(to_send);
    std::cout << "Parent with PID: " << getpid() << ", writing to child..."
              << std::endl;
    int n_written = write(p_fds[1], to_send, to_send_len);
    if (n_written == -1) {
      std::cerr << "Error reading: " << strerror(errno) << std::endl;
      exit(1);
    }

    if (n_written != to_send_len) {
      std::cerr << "Incomplete write. To write: " << to_send_len
                << ". Actual written: " << n_written << std::endl;
    }

    // Notify write complete
    std::cout << "Completing write by parent with PID " << getpid()
              << std::endl;
    // close() notifies end-of-data on the fd
    close(p_fds[1]); // IMPORTANT
    break;
  }

  return 0;
}