gateio, ftx and binance all use same funding fee formula

freqtrade/exchange/binance.py

@@ -231,8 +231,8 @@ class Binance(Exchange):
         self,
         pair: str,
         contract_size: float,
-        mark_price: float,
-        funding_rate: Optional[float],
+        funding_rate: float,
+        mark_price: Optional[float],
     ) -> float:
         """
             Calculates a single funding fee
@@ -245,9 +245,6 @@ class Binance(Exchange):
         if mark_price is None:
             raise OperationalException("Mark price cannot be None for Binance._get_funding_fee")
         nominal_value = mark_price * contract_size
-        if funding_rate is None:
-            raise OperationalException(
-                "Funding rate should never be none on Binance._get_funding_fee")
         return nominal_value * funding_rate
 
     async def _async_get_historic_ohlcv(

freqtrade/exchange/exchange.py

@@ -1694,17 +1694,19 @@ class Exchange:
         self,
         pair: str,
         contract_size: float,
+        funding_rate: float,
         mark_price: float,
-        funding_rate: Optional[float]
     ) -> float:
         """
             Calculates a single funding fee
             :param contract_size: The amount/quanity
             :param mark_price: The price of the asset that the contract is based off of
             :param funding_rate: the interest rate and the premium
+                - interest rate:
                 - premium: varies by price difference between the perpetual contract and mark price
         """
-        raise OperationalException(f"Funding fee has not been implemented for {self.name}")
+        nominal_value = mark_price * contract_size
+        return nominal_value * funding_rate
 
     def fill_leverage_brackets(self):
         """

freqtrade/exchange/ftx.py

@@ -186,23 +186,4 @@ class Ftx(Exchange):
         return 20.0
 
     def _get_funding_rate(self, pair: str, when: datetime) -> Optional[float]:
-        """FTX doesn't use this"""
-        return None
-
-    def _get_funding_fee(
-        self,
-        pair: str,
-        contract_size: float,
-        mark_price: float,
-        premium_index: Optional[float],
-        # index_price: float,
-        # interest_rate: float)
-    ) -> float:
-        """
-            Calculates a single funding fee
-            Always paid in USD on FTX  # TODO: How do we account for this
-            : param contract_size: The amount/quanity
-            : param mark_price: The price of the asset that the contract is based off of
-            : param funding_rate: Must be None on ftx
-        """
-        return (contract_size * mark_price) / 24
+        raise OperationalException(f'_get_mark_price has not been implemented on {self.name}')