From aaa855e3839130a79193f38969f07763f2773c5d Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Mon, 11 Nov 2024 01:12:29 +0800
Subject: HALF WORK: 2024.11.27

---
 tools/cru-py/cru/_util/_const.py | 49 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 tools/cru-py/cru/_util/_const.py

(limited to 'tools/cru-py/cru/_util/_const.py')

diff --git a/tools/cru-py/cru/_util/_const.py b/tools/cru-py/cru/_util/_const.py
new file mode 100644
index 0000000..bc02c3a
--- /dev/null
+++ b/tools/cru-py/cru/_util/_const.py
@@ -0,0 +1,49 @@
+from enum import Enum, auto
+from typing import Self, TypeGuard, TypeVar
+
+from ._cru import CRU
+
+_T = TypeVar("_T")
+
+
+class CruConstantBase(Enum):
+    @classmethod
+    def check(cls, v: _T | Self) -> TypeGuard[Self]:
+        return isinstance(v, cls)
+
+    @classmethod
+    def check_not(cls, v: _T | Self) -> TypeGuard[_T]:
+        return not cls.check(v)
+
+    @classmethod
+    def value(cls) -> Self:
+        return cls.VALUE  # type: ignore
+
+
+class CruNotFound(CruConstantBase):
+    VALUE = auto()
+
+
+class CruUseDefault(CruConstantBase):
+    VALUE = auto()
+
+
+class CruDontChange(CruConstantBase):
+    VALUE = auto()
+
+
+class CruNoValue(CruConstantBase):
+    VALUE = auto()
+
+
+class CruPlaceholder(CruConstantBase):
+    VALUE = auto()
+
+
+CRU.add_objects(
+    CruNotFound,
+    CruUseDefault,
+    CruDontChange,
+    CruNoValue,
+    CruPlaceholder,
+)
-- 
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