import std/posix

type PollData* = object
  fds: seq[TPollFd]

iterator events*(ctx: PollData): TPollFd =
  let L = ctx.fds.len
  for i in 0 ..< L:
    let event = ctx.fds[i]
    if event.fd == -1 or ctx.fds[i].revents == 0:
      continue
    assert (event.revents and POLLNVAL) == 0
    yield event

proc register*(ctx: var PollData; fd: int; events: cshort) =
  if fd >= ctx.fds.len:
    ctx.fds.setLen(fd + 1)
  ctx.fds[fd].fd = cint(fd)
  ctx.fds[fd].events = events

proc register*(ctx: var PollData; fd: cint; events: cshort) =
  ctx.register(int(fd), events)

proc unregister*(ctx: var PollData; fd: int) =
  ctx.fds[fd].fd = -1

proc trim(ctx: var PollData) =
  var i = ctx.fds.high
  while i >= 0:
    if ctx.fds[i].fd != -1:
      break
    dec i
  ctx.fds.setLen(i + 1)

proc clear*(ctx: var PollData) =
  ctx.fds.setLen(0)

proc poll*(ctx: var PollData; timeout: cint) =
  ctx.trim()
  let fds = addr ctx.fds[0]
  let nfds = cint(ctx.fds.len)
  {.emit: """
  poll(`fds`, `nfds`, `timeout`);
  """.}