// A is the value type we get for each candle
asclass CandleBasedIndicator<A> extends MetaWithChangeListeners {
  replace Candle with TradingCandle.
  
  // Number of candles we need to look back to
  settable int length = 20;
  
  event candleAdded(Candle candle);
  event candleRemoved(Candle candle);
  
  // get current indicator value
  abstract A value aka get();
  
  simplyCached SimpleCircularBuffer<Candle> candles() {
    ret new SimpleCircularBuffer(candlesNeeded());
  }
  
  int candlesNeeded() { ret length; }
  
  Candle lastCandle() { ret candles().last(); }
  
  selfType feed(TradingCandleMaker candleMaker) {
    if (candleMaker != null)
      // TODO: cut list down first
      for (candle : candleMaker.candles())
        add(candle);
    this;
  }
  
  selfType add aka feed(Iterable<TradingCandle> candles) {
    fOr (candle : candles)
      add(candle);
    this;
  }
  
  // Can add candles twice, will automatically ignore the second time
  selfType add aka feed(TradingCandle candle) {
    if (candle.ongoing()) this;
    if (lastCandle() != null && lessOrEq(candle.startTime, lastCandle().startTime))
      this;
      
    while (candles().size() > max(length-1, 0))
      candleRemoved(candles().remove());
    candles().add(candle);
    
    candleAdded(candle);
    this;
  }
  
  void reset {
    resetFields(this, "candles_cache");
  }
  
  selfType emptyClone() {
    var clone = shallowNonTransientClone(this);
    clone.reset();
    ret clone;
  }
}

Began life as a copy of #1036443