persistable sclass MAIndicator extends CandleBasedIndicator<Double> is IntegrityCheckable {

  // The MA calculator

  settable SimpleMovingAverage ma;

  // MA values collected as ticker

  settableWithVar TickerSequence history = new TickerSequence("MA");

  // MA value

  double value = Double.NaN;

  // How many historic items to keep

  settable int maxHistoryLength = 1000;

  Double value() { ret value; }

  *(int *length) {}

  {

    length = 7;

    onCandleAdded((IVF1<TradingCandle>) candle -> {

      if (ma == null) makeMA();

      ma.add(candle.close());

      value = ma.complete() ? ma! : Double.NaN;

      if (!isNaN(value)) {

        long time = candle.endTime().toLong();

        history?.addIfPriceChanged(value, time);

        shortenHistory();

      }

    });

  }

  TickerSequence asTicker(L<TradingCandle> candles) {

    feed(candles);

    ret history;

  }

  void makeMA {

    ma = new SimpleMovingAverage(length);

  }

  void reset :: after {

    resetFields(this, "value history");

    makeMA();

  }

  public void integrityCheck {

    history?.integrityCheck();

  }

  void shortenHistory {

    int increment = 10;

    if (history != null && history.size() > maxHistoryLength+increment)

      history(history.subSequence(history.size()-maxHistoryLength));

  }

}