sclass RSI extends CandleBasedIndicator<Double> {
  settable int smoothingPeriod;
  settable SmoothedMovingAverage up;
  settable SmoothedMovingAverage down;
  settable double rsi = Double.NaN;
  
  Double value() { ret rsi(); }
  
  {
    length = 25;
    onCandleAdded((IVF1) c -> {
      if (isNull(up())) init();
      var x = c.move();
      var u = max(x, 0.0);
      var d = neg(min(x, 0.0));
      up().add(u);
      down().add(d);
      var rs = div(up()!, down()!);
      rsi(100-100/(1+rs));
    });
  }
  
  void init() {
    up = new SmoothedMovingAverage(this.length());
    down = new SmoothedMovingAverage(this.length());
  }
  
  TickerSequence asTicker(L<TradingCandle> candles) {
    var seq = new TickerSequence("RSI");
    fOr (candle : candles) {
      feed(candle);
      var value = this.get();
      if (not(isNaN(value)))
        seq.addIfPriceChanged(value, candle.endTime().toLong());
    }
    ret seq;
  }
}