concept JuiceStrategy extends G22TradingStrategy {
  settableWithVar AbstractJuicer prototypeJuicer;
  
  persistable class Position extends G22TradingStrategy.Position {
    settable AbstractJuicer juicer;
  }
  
  selfType emptyClone() {
    JuiceStrategy clone = cast super.emptyClone();
    clone.prototypeJuicer(prototypeJuicer?.configClone());
    ret clone;
  }
  
  void price(double price) {
    if (currentPrice == price) ret;
    currentPrice = price;
    afterwards { change(); }
    
    for (p : openPositions()) {
      cast p to Position;
      
      if (p.juicer != null) {
        var signals = p.juicer.calculateCloseSignals();
        var strongest = highestBy(signals, s -> s.strength());
        if (strongest != null && strongest.isTrigger()) {
          p.close(strongest);
        }
      }
    }
  }
  
  Position openShort() { ret openPosition(-1); }
  Position openLong() { ret openPosition(1); }
  
  // 1 = use marginPerPosition, other value = scale position up or down
  Position openPosition(double direction) {
    new Position p;
    p.marginToUse = marginPerPosition*abs(direction);
    ret openPosition(p, sign(direction));
  }
}