!747

m {
  static new Map<S, Long> lastSeen; // computer ID to timestamp
  
  p {
    readLocally("lastSeen");
    makeAndroid3("Who Is Online Bot.");
  }
  
  static synchronized S answer(S s) {
    new Matches m;
    if (match3("I am online. -*", s, m)) {
      S computerID = m.unq(0);
      lastSeen.put(computerID, now());
      saveLocally("lastSeen");
      print("Got ping from " + computerID + ".");
      ret "OK, noted.";
    }
    
    if (match3("When was * last online?", s, m)) {
      Long time = lastSeen.get(m.unq(0));
      ret time != null ? format3("at *", time) : "never";
    }
    
    ret standardQuery(s, "lastSeen");
  }
}