Enum refactoring.

Consolidate the common methods related to enum classes.

1 files changed, 77 insertions, 0 deletions

diff --git a/dns/enum.py b/dns/enum.py
new file mode 100644
index 0000000..62b4a44
--- /dev/null
+++ b/dns/enum.py
@@ -0,0 +1,77 @@
+# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
+
+# Copyright (C) 2003-2017 Nominum, Inc.
+#
+# Permission to use, copy, modify, and distribute this software and its
+# documentation for any purpose with or without fee is hereby granted,
+# provided that the above copyright notice and this permission notice
+# appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+import enum
+
+class IntEnum(enum.IntEnum):
+    @classmethod
+    def _check_value(cls, value):
+        max = cls._maximum()
+        if value < 0 or value > max:
+            name = cls._short_name()
+            raise ValueError(f"{name} must be between >= 0 and <= {max}")
+
+    @classmethod
+    def from_text(cls, text):
+        text = text.upper()
+        try:
+            return cls[text]
+        except KeyError:
+            pass
+        prefix = cls._prefix()
+        if text.startswith(prefix) and text[len(prefix):].isdigit():
+            value = int(text[len(prefix):])
+            cls._check_value(value)
+            try:
+                return cls(value)
+            except ValueError:
+                return value
+        raise cls._unknown_exception_class()
+
+    @classmethod
+    def to_text(cls, value):
+        cls._check_value(value)
+        try:
+            return cls(value).name
+        except ValueError:
+            return f"{cls._prefix()}{value}"
+
+    @classmethod
+    def to_enum(cls, value):
+        if isinstance(value, str):
+            return cls.from_text(value)
+        cls._check_value(value)
+        try:
+            return cls(value)
+        except ValueError:
+            return value
+
+    @classmethod
+    def _maximum(cls):
+        raise NotImplemented
+
+    @classmethod
+    def _short_name(cls):
+        return cls.__name__.lower()
+
+    @classmethod
+    def _prefix(cls):
+        return ''
+
+    @classmethod
+    def _unknown_exception_class(cls):
+        return ValueError