!include once #1015699 // websocket

sbool webSocketOnMessage_withIdler_verbose;

static WebSocketClient webSocketOnMessage_withIdler(S url, final VF1<S> onMessage, double idleInterval) {
  ret webSocketOnMessage_withIdler(url, onMessage, idleInterval, null);
}

static WebSocketClient webSocketOnMessage_withIdler(S url, final VF1<S> onMessage, final double idleInterval, fS initialMessage, fO... args) ctex {
  WebSocketClient client = new WebSocketClient(new URI(url)) {
    java.util.Timer idler;
    
    public void onMessage(S s) {
      if (!licensed()) ret with close(); // program exit
      s = dropTrailingNullChars(s);
      pcallF(onMessage, s);
    }

    public void onOpen(ServerHandshake handshake) {
      if (webSocketOnMessage_withIdler_verbose)
        print("WebSocket connected.");
      if (nempty(initialMessage))
        send(format(initialMessage, args));
      idler = doEvery(idleInterval, r {
        if (webSocketOnMessage_withIdler_verbose)
          print("websocket idling");
        send("");
      });
    }
    
    public void onClose(int code, S reason, bool remote) {
      cancelTimer(idler);
      idler = null;
    }
    
    public void onError(Exception e) { printStackTrace(e); }
  };
  
  if (webSocketOnMessage_withIdler_verbose)
    print("Connecting to WebSocket: " + url);
  client.connect();
  ret client;
}

Began life as a copy of #1015083