Reduce code duplication in datahandlers

freqtrade/data/history/idatahandler.py

@@ -39,7 +39,6 @@ class IDataHandler(ABC):
         raise NotImplementedError()
 
     @classmethod
-    @abstractmethod
     def ohlcv_get_available_data(
             cls, datadir: Path, trading_mode: TradingMode) -> ListPairsWithTimeframes:
         """
@@ -48,6 +47,18 @@ class IDataHandler(ABC):
         :param trading_mode: trading-mode to be used
         :return: List of Tuples of (pair, timeframe, CandleType)
         """
+        if trading_mode == TradingMode.FUTURES:
+            datadir = datadir.joinpath('futures')
+        _tmp = [
+            re.search(
+                cls._OHLCV_REGEX, p.name
+            ) for p in datadir.glob(f"*.{cls._get_file_extension()}")]
+        return [
+            (
+                cls.rebuild_pair_from_filename(match[1]),
+                cls.rebuild_timeframe_from_filename(match[2]),
+                CandleType.from_string(match[3])
+            ) for match in _tmp if match and len(match.groups()) > 1]
 
     @classmethod
     @abstractmethod