use time

-- iteration 24 T5: the CANCEL idiom — no cancel builtin, a generation
-- counter instead. The actor bumps its generation; a stale timer's
-- message names the old one and is recognized and ignored on arrival.
class Timer {
  gen: Int
}

class Gate {
  gen: Int
  fn receive(msg: Timer) {
    if msg.gen == self.gen {
      print("fired gen ${msg.gen}");
    } else {
      print("stale gen ${msg.gen} ignored");
    }
  }
}

fn main() -> Int {
  let g: actor Timer = spawn Gate { gen: 2 };
  time.after(30, g, Timer { gen: 1 });
  time.after(60, g, Timer { gen: 2 });
  time.sleep(200);
  print("done");
  return 0;
}