#pragma once

#include <poll.h>
#include <signal.h>
#include <sys/types.h>
#include <unistd.h>
#include <atomic>
#include <cstdlib>
#include <thread>

namespace nix {

class MonitorFdHup {
 private:
  std::thread thread;

 public:
  MonitorFdHup(int fd) {
    thread = std::thread([fd]() {
      while (true) {
        /* Wait indefinitely until a POLLHUP occurs. */
        struct pollfd fds[1];
        fds[0].fd = fd;
        /* This shouldn't be necessary, but macOS doesn't seem to
           like a zeroed out events field.
           See rdar://37537852.
        */
        fds[0].events = POLLHUP;
        auto count = poll(fds, 1, -1);
        if (count == -1) abort();  // can't happen
        /* This shouldn't happen, but can on macOS due to a bug.
           See rdar://37550628.

           This may eventually need a delay or further
           coordination with the main thread if spinning proves
           too harmful.
         */
        if (count == 0) continue;
        assert(fds[0].revents & POLLHUP);
        triggerInterrupt();
        break;
      }
    });
  };

  ~MonitorFdHup() {
    pthread_cancel(thread.native_handle());
    thread.join();
  }
};

}  // namespace nix