taskie.ex

defmodule Taskie do
  def pbump(n) do
    chunk_size = div(n, 10)
    1..n
    |> Enum.chunk(chunk_size, chunk_size, [])
    |> Enum.map(fn(chunk) ->
      chunk
      |> Enum.map(fn(v) -> Task.async(fn() -> Process.sleep(1000); bump(v) end)end)
      |> Enum.map(fn(t) -> Task.await(t) end)
    end)
  end

  defp bump(v), do: v + 1


  defstruct owner: nil, pid: nil, ref: nil

  def async(fun) do
    task_ref = make_ref()
    owner = self()

    pid = spawn_link(fn ->
      receive do
        {^task_ref, ref} ->
          result = fun.()
          send owner, {ref, result}
      end
    end)

    ref = Process.monitor(pid)
    send(pid, {task_ref, ref})

    %Taskie{ref: ref, pid: pid, owner: owner}
  end

  def await(task, timeout \\ 5_000) do
    %{ref: ref} = task

    receive do
      {^ref, result} ->
        Process.demonitor(ref, [:flush])
        result
    after
      timeout ->
        exit({:timeout, {__MODULE__,
                         :await,
                         [task, timeout]}})
    end
  end
end