interface IFuturesMarket {

  // all open/close orders are market right now (not limit)

  sclass OpenOrCloseOrder {

    // input parameters

    settable S clientOrderID; // optional

    settable HoldSide holdSide;

    settable double cryptoAmount;

    // Limit order if set. Otherwise market order.

    // Limit orders are good-until-cancel.

    // (unimplemented)

    settable double limitPrice = Double.NaN;

    // output parameters

    // order ID returned by platform

    settable S orderID;

  }

  macro ExtendingOpenOrCloseOrder {

    public selfType clientOrderID(S clientOrderID) { super.clientOrderID(clientOrderID); this; }

    public selfType holdSide(HoldSide holdSide) { super.holdSide(holdSide); this; }

    public selfType cryptoAmount(double cryptoAmount) { super.cryptoAmount(cryptoAmount); this; }

    public selfType limitPrice(double limitPrice) { super.limitPrice(limitPrice); this; }

  }

  sclass OpenOrder extends OpenOrCloseOrder {

    ExtendingOpenOrCloseOrder

    settable double leverage = 1;

    settable bool isCross;

    settable double takeProfitPrice = Double.NaN;

    settable double stopLossPrice = Double.NaN;

  }

  sclass CloseOrder extends OpenOrCloseOrder {

    ExtendingOpenOrCloseOrder

  }

  // throws exception if order failed

  void openPosition(OpenOrder order);

  // throws exception if order failed

  void closePosition(CloseOrder order);

  sclass SwappableImplementation is IFuturesMarket {

    public swappable void openPosition(OpenOrder order) {}

    public swappable void closePosition(CloseOrder order) {}

    public swappable double drift() { unimplemented(); }

    public FutureCoinParameters getCoinParameters() { unimplemented(); }

  }

  // Get current drift (sum of longs+shorts in crypto units)

  double drift();

  FutureCoinParameters getCoinParameters();

}