// Pipe Watch ("pw")
// Copyright 2022-2023 Kaz Kylheku <kaz@kylheku.com>
//
// BSD-2 License
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
//    this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

#include <stddef.h>
#include <sys/select.h>
#include <poll.h>
#include <limits.h>

// Would you believe it? MacOS poll() does not support devices, such as TTYs.
// Here we implement a lame poll using the inefficient select function.

int macpoll(struct pollfd *fds, nfds_t nfds, int timeout)
{
  fd_set readfds, writefds, exceptfds;
  struct timeval tv;
  int maxfd = 0;

  FD_ZERO(&readfds);
  FD_ZERO(&writefds);
  FD_ZERO(&exceptfds);

  for (nfds_t i = 0; i < nfds; i++) {
    int events = fds[i].events;
    int fd = fds[i].fd;
    if (fd < 0)
      continue;
    if (fd > maxfd)
      maxfd = fd;
    if (events & POLLIN)
      FD_SET(fd, &readfds);
    if (events & POLLOUT)
      FD_SET(fd, &writefds);
    if (events & POLLERR)
      FD_SET(fd, &exceptfds);
  }

  tv.tv_sec = timeout / 1000;
  tv.tv_usec = (timeout % 1000) * 1000;

  int ret = select(maxfd + 1, &readfds, &writefds, &exceptfds,
                   timeout >= 0 ? &tv : NULL);

  if (ret >= 0) {
    for (nfds_t i = 0; i < nfds; i++) {
      int fd = fds[i].fd;
      int revents = 0;
      fds[i].revents = 0;
      if (FD_ISSET(fd, &readfds))
        revents |= POLLIN;
      if (FD_ISSET(fd, &writefds))
        revents |= POLLOUT;
      if (FD_ISSET(fd, &exceptfds))
        revents |= POLLERR;
      fds[i].revents = revents;
    }
  }

  return ret;
}