asyncthread.nim

import std/asyncdispatch

proc asyncThread*[T](worker: proc (arg: T) {.thread.}; arg: T): Future[void] {.async.} =
  ## Starts a thread that runs `worker` and completes the Future when the thread exits.
  var fut = newFuture[void]("asyncThread")
  let ev = newAsyncEvent()
  addEvent(ev) do (_: AsyncFD) -> bool:
    fut.complete()
    true

  proc wrapper(args: tuple[worker: proc (arg: T) {.thread.}; arg: T; ev: AsyncEvent]) {.thread.} =
    args.worker(args.arg)
    args.ev.trigger()

  var thr: Thread[(proc (arg: T) {.thread.}, T, AsyncEvent)]
  createThread(thr, wrapper, (worker, arg, ev))

  await fut
  joinThread(thr)

when isMainModule:
  import std/os

  proc worker(arg: string) {.thread.} =
    echo "\tthread arg: ", arg
    sleep(milsecs = 1000)
    echo "\tthread done."

  echo "program start"
  waitFor asyncThread(worker, "hello")
  echo "program done"