// A is the value type we get for each candle
asclass CandleBasedIndicator<A> {
  replace Candle with TradingCandle.
  
  // Number of candles we need to look back to
  settable int length = 20;
  
  event candleAdded(Candle candle);
  event candleDropped(Candle candle);
  
  // get current indicator value
  abstract A value aka get();
  
  simplyCached CircularFifoBuffer<Candle> candles() {
    ret new CircularFifoBuffer(length);
  }
  
  Candle lastCandle() { ret candles().last(); }
  
  void feed(TradingCandleMaker candleMaker) {
    if (candleMaker != null)
      for (candle : candleMaker.candles())
        add(candle);
  }
  
  void add aka feed(Iterable<TradingCandle> candles) {
    fOr (candle : candles)
      add(candle);
  }
  
  void add aka feed(TradingCandle candle) {
    if (candle.ongoing()) ret;
    if (lastCandle() != null && lessOrEq(candle.startTime, lastCandle().startTime))
      ret;
      
    while (candles().size() > max(length-1, 0))
      candleDropped(candles().remove());
    candles().add(candle);
    
    candleAdded(candle);
  }
}