interface IFuturesMarket {
  // all open/close orders are market right now (not limit)
  
  sclass OpenOrder {
    settable HoldSide holdSide;
    settable double cryptoAmount;
    settable double leverage = 1;
    settable bool isCross;
  }
  
  sclass CloseOrder {
    settable HoldSide holdSide;
    settable double cryptoAmount;
  }
  
  // throws exception if order failed
  void openPosition(OpenOrder order);
  
  // throws exception if order failed
  void closePosition(CloseOrder order);
}