static Map<S, Status> status_map; // key = dialog id

static abstract class Status {
  abstract S answer(S s);
}

// get status
static synchronized Status status() {
  status_load();
  ret status_map.get(getDialogID());
}

static void status_load() {
  if (status_map == null) {
    status_map = new TreeMap;
    load("status_map");
  }
}

// set status
static synchronized void status(Status s) {
  status_load();
  if (s == null)
    status_map.remove(getDialogID());
  else
    status_map.put(getDialogID(), s);
  save("status_map");
}

static S status_answer(S s) {
  Status status = status();
  if (status != null)
    ret status.answer(s);
  ret null;
}

Began life as a copy of #1002567