Added Formula for FTX interest rate

freqtrade/leverage/interest.py

@@ -0,0 +1,43 @@
+from decimal import Decimal
+from math import ceil
+
+from freqtrade.exceptions import OperationalException
+
+
+one = Decimal(1.0)
+four = Decimal(4.0)
+twenty_four = Decimal(24.0)
+
+
+def interest(
+    exchange_name: str,
+    borrowed: Decimal,
+    rate: Decimal,
+    hours: Decimal
+) -> Decimal:
+    """
+        Equation to calculate interest on margin trades
+
+        :param exchange_name: The exchanged being trading on
+        :param borrowed: The amount of currency being borrowed
+        :param rate: The rate of interest (i.e daily interest rate)
+        :param hours: The time in hours that the currency has been borrowed for
+
+        Raises:
+            OperationalException: Raised if freqtrade does
+            not support margin trading for this exchange
+
+        Returns: The amount of interest owed (currency matches borrowed)
+    """
+    exchange_name = exchange_name.lower()
+    if exchange_name == "binance":
+        return borrowed * rate * ceil(hours)/twenty_four
+    elif exchange_name == "kraken":
+        # Rounded based on https://kraken-fees-calculator.github.io/
+        return borrowed * rate * (one+ceil(hours/four))
+    elif exchange_name == "ftx":
+        # As Explained under #Interest rates section in
+        # https://help.ftx.com/hc/en-us/articles/360053007671-Spot-Margin-Trading-Explainer
+        return borrowed * rate * ceil(hours)/twenty_four
+    else:
+        raise OperationalException(f"Leverage not available on {exchange_name} with freqtrade")