types: make enum levels serializable

Add to/from_pod implementations to level, so that it may be serialized
properly. In order to make sure that serialization is a reversible
operation, ensure that the level value is numeric.

tests/test_utils.py

@@ -20,7 +20,9 @@ from unittest import TestCase
 from nose.tools import raises, assert_equal, assert_not_equal, assert_in, assert_not_in
 from nose.tools import assert_true, assert_false
 
-from wa.utils.types import list_or_integer, list_or_bool, caseless_string, arguments, prioritylist
+from wa.utils.types import (list_or_integer, list_or_bool, caseless_string,
+                            arguments, prioritylist, enum, level)
+
 
 
 class TestPriorityList(TestCase):
@@ -91,3 +93,18 @@ class TestPriorityList(TestCase):
         assert_equal(list(pl), ['a', 'b','y', 'x', 'm', 'n'])
         pl.add_after('z', 'm')
         assert_equal(list(pl), ['a', 'b', 'y', 'x', 'm', 'z', 'n'])
+
+
+class TestEnumLevel(TestCase):
+
+    def test_serialize_level(self):
+        l = level('test', 1)
+        s = l.to_pod()
+        l2 = level.from_pod(s)
+        assert_equal(l, l2)
+
+    def test_deserialize_enum(self):
+        e = enum(['one', 'two', 'three'])
+        s = e.one.to_pod()
+        l = e.from_pod(s)
+        assert_equal(l, e.one)

wa/utils/types.py

@@ -488,9 +488,17 @@ class level(object):
 
     """
 
+    @staticmethod
+    def from_pod(pod):
+        name, value_part =  pod.split('(')
+        return level(name, numeric(value_part.rstrip(')')))
+
     def __init__(self, name, value):
         self.name = caseless_string(name)
-        self.value = value
+        self.value = numeric(value)
+
+    def to_pod(self):
+        return repr(self)
 
     def __str__(self):
         return self.name
@@ -545,6 +553,15 @@ def enum(args, start=0, step=1):
 
     class Enum(object):
 
+        @classmethod
+        def from_pod(cls, pod):
+            lv = level.from_pod(pod)
+            for enum_level in cls.values:
+                if enum_level == lv:
+                    return enum_level
+            msg = 'Unexpected value "{}" for enum.'
+            raise ValueError(msg.format(pod))
+
         def __new__(cls, name):
             for attr_name in dir(cls):
                 if attr_name.startswith('__'):