From 6beb56cd9101761c41615d6c8c3c64ef0327d52e Mon Sep 17 00:00:00 2001
From: glrs <5999366+glrs@users.noreply.github.com>
Date: Thu, 5 Dec 2024 13:58:45 +0100
Subject: [PATCH] Introduce `SingletonMeta` metaclass and refactor singleton
 decorator to a metaclass instead of a function decorator

---
 lib/core_utils/singleton_decorator.py | 41 ++++++++++++++++++---------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/lib/core_utils/singleton_decorator.py b/lib/core_utils/singleton_decorator.py
index 7b89733..475e8f2 100644
--- a/lib/core_utils/singleton_decorator.py
+++ b/lib/core_utils/singleton_decorator.py
@@ -1,25 +1,38 @@
-from typing import Any, Callable, Dict, Type, TypeVar
+from typing import Any, Dict, Type
 
-T = TypeVar("T")
 
+class SingletonMeta(type):
+    """
+    A metaclass that creates a singleton instance of a class.
+    """
+
+    _instances: Dict[type, Any] = {}
 
-def singleton(cls: Type[T]) -> Callable[..., T]:
-    """Decorator to make a class a singleton.
+    def __call__(cls, *args: Any, **kwargs: Any) -> Any:
+        if cls not in cls._instances:
+            cls._instances[cls] = super().__call__(*args, **kwargs)
+        return cls._instances[cls]
 
-    Ensures that only one instance of the class is created. Subsequent
-    calls to the class will return the same instance.
+
+def singleton(cls: Type[Any]) -> Type[Any]:
+    """
+    Decorator to make a class a singleton by setting its metaclass to SingletonMeta.
 
     Args:
-        cls (Type[T]): The class to be decorated.
+        cls (Type[Any]): The class to be decorated.
 
     Returns:
-        Callable[..., T]: A function that returns the singleton instance of the class.
+        Type[Any]: The singleton class with SingletonMeta as its metaclass.
     """
-    instances: Dict[Type[T], T] = {}
 
-    def get_instance(*args: Any, **kwargs: Any) -> T:
-        if cls not in instances:
-            instances[cls] = cls(*args, **kwargs)
-        return instances[cls]
+    # Create a new class with SingletonMeta as its metaclass
+    class SingletonClass(cls, metaclass=SingletonMeta):
+        pass
+
+    # Preserve class metadata
+    SingletonClass.__name__ = cls.__name__
+    SingletonClass.__doc__ = cls.__doc__
+    SingletonClass.__module__ = cls.__module__
+    SingletonClass.__annotations__ = getattr(cls, "__annotations__", {})
 
-    return get_instance
+    return SingletonClass