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));
  }
}