after.pony

use "time"

interface Fn
  fun apply()

type Duration is U64

primitive Second
  fun apply(n: (U64 | USize)): Duration =>
    match n
    | let s: U64 => s * 1_000_000_000
    | let s: USize => U64.from[USize](s) * 1_000_000_000
    end

class After
  fun apply(duration: Duration, fn: Fn iso) =>
    let timers = Timers
    let timer = Timer(AfterNotify(consume fn), duration)
    timers(consume timer)

class AfterNotify is TimerNotify
  let _fn: Fn iso

  new iso create(fn: Fn iso) =>
    _fn = consume fn

  fun ref apply(timer: Timer, count: U64): Bool =>
    _fn()
    false

actor Main
  new create(env: Env) =>
    let out = env.out
    let messages = ["5"; "4"; "3"; "Ready"; "Steady"; "Go!"]

    for (i, message) in messages.pairs() do
      After(Second(i), recover this~print(out, message) end)
    end

  fun tag print(out: OutStream, s: String) =>
    out.print(s)