1 files changed, 97 insertions, 0 deletions
diff --git a/python/cru/_decorator.py b/python/cru/_decorator.py
new file mode 100644
index 0000000..137fc05
--- /dev/null
+++ b/python/cru/_decorator.py
@@ -0,0 +1,97 @@
+from __future__ import annotations
+
+from collections.abc import Callable
+from typing import (
+    Concatenate,
+    Generic,
+    ParamSpec,
+    TypeVar,
+    cast,
+)
+
+from ._base import CRU
+
+_P = ParamSpec("_P")
+_T = TypeVar("_T")
+_O = TypeVar("_O")
+_R = TypeVar("_R")
+
+
+class CruDecorator:
+
+    class ConvertResult(Generic[_T, _O]):
+        def __init__(
+            self,
+            converter: Callable[[_T], _O],
+        ) -> None:
+            self.converter = converter
+
+        def __call__(self, origin: Callable[_P, _T]) -> Callable[_P, _O]:
+            converter = self.converter
+
+            def real_impl(*args: _P.args, **kwargs: _P.kwargs) -> _O:
+                return converter(origin(*args, **kwargs))
+
+            return real_impl
+
+    class ImplementedBy(Generic[_T, _O, _P, _R]):
+        def __init__(
+            self,
+            impl: Callable[Concatenate[_O, _P], _R],
+            converter: Callable[[_T], _O],
+        ) -> None:
+            self.impl = impl
+            self.converter = converter
+
+        def __call__(
+            self, _origin: Callable[[_T], None]
+        ) -> Callable[Concatenate[_T, _P], _R]:
+            converter = self.converter
+            impl = self.impl
+
+            def real_impl(_self: _T, *args: _P.args, **kwargs: _P.kwargs) -> _R:
+                return cast(Callable[Concatenate[_O, _P], _R], impl)(
+                    converter(_self), *args, **kwargs
+                )
+
+            return real_impl
+
+        @staticmethod
+        def create_factory(converter: Callable[[_T], _O]) -> Callable[
+            [Callable[Concatenate[_O, _P], _R]],
+            CruDecorator.ImplementedBy[_T, _O, _P, _R],
+        ]:
+            def create(
+                m: Callable[Concatenate[_O, _P], _R],
+            ) -> CruDecorator.ImplementedBy[_T, _O, _P, _R]:
+                return CruDecorator.ImplementedBy(m, converter)
+
+            return create
+
+    class ImplementedByNoSelf(Generic[_P, _R]):
+        def __init__(self, impl: Callable[_P, _R]) -> None:
+            self.impl = impl
+
+        def __call__(
+            self, _origin: Callable[[_T], None]
+        ) -> Callable[Concatenate[_T, _P], _R]:
+            impl = self.impl
+
+            def real_impl(_self: _T, *args: _P.args, **kwargs: _P.kwargs) -> _R:
+                return cast(Callable[_P, _R], impl)(*args, **kwargs)
+
+            return real_impl
+
+        @staticmethod
+        def create_factory() -> (
+            Callable[[Callable[_P, _R]], CruDecorator.ImplementedByNoSelf[_P, _R]]
+        ):
+            def create(
+                m: Callable[_P, _R],
+            ) -> CruDecorator.ImplementedByNoSelf[_P, _R]:
+                return CruDecorator.ImplementedByNoSelf(m)
+
+            return create
+
+
+CRU.add_objects(CruDecorator)