Add base class for feature flags.

BL_Python/platform/feature_flag_router.py

@@ -0,0 +1,67 @@
+from abc import ABC
+from logging import Logger
+from typing import Dict
+
+
+class FeatureFlagRouter(ABC):
+    """
+    The base feature flag router.
+    All feature flag routers should extend this class.
+    """
+
+    _logger: Logger
+    _feature_flags: Dict[str, bool]
+
+    def __init__(self, logger: Logger) -> None:
+        self._logger = logger
+        self._feature_flags = {}
+
+    def set_feature_is_enabled(self, name: str, is_enabled: bool) -> None:
+        """
+        Enables or disables a feature flag in the in-memory dictionary of feature flags.
+
+        Subclasses should call this method to validate parameters and cache values.
+
+        name: The feature flag to check.
+
+        is_enabled: Whether the feature flag is to be enabled or disabled.
+        """
+        if name in self._feature_flags:
+            self._logger.warn(
+                f"Overridding feature flag value for '{name}'. Toggling from {self._feature_flags[name]} to {self._feature_flags[name]}"
+            )
+        if type(name) != str:
+            raise TypeError("`name` must be a string.")
+
+        if type(is_enabled) != bool:
+            raise TypeError("`is_enabled` must be a boolean.")
+
+        if not name:
+            raise ValueError("`name` parameter is required and cannot be empty.")
+
+        self._feature_flags[name] = is_enabled
+
+    def feature_is_enabled(
+        self, name: str, default: bool | None = False
+    ) -> bool | None:
+        """
+        Determine whether a feature flag is enabled or disabled.
+
+        Subclasses should call this method to validate parameters and use cached values.
+
+        name: The feature flag to check.
+
+        default: If the feature flag is not in the in-memory dictionary of flags,
+            this is the default value to return. The default parameter value
+            when not specified is `False`.
+        """
+        if type(name) != str:
+            raise TypeError("`name` must be a string.")
+
+        if not name:
+            raise ValueError("`name` parameter is required and cannot be empty.")
+
+        if name in self._feature_flags:
+            return self._feature_flags[name]
+
+        return default