from UserDict import UserDict
from MiscUtils import StringTypes

try: # for Python < 2.3
	True, False
except NameError:
	True, False = 1, 0


class MiddleDict(UserDict):
	"""A MiddleKit UserDict.

	A UserDict for the purposes of MiddleKit, specifically Klass and Attr
	which are subclasses.

	@@ 2004-04-02 CE: Should consider making this case-preserving, but
	   case-insensitive with respect to keys.
	   
	"""

	def boolForKey(self, key, default=False):
		"""Return True or False for the given key.

		Returns False if the key does not even exist.
		Raises a value error if the key exists, but cannot be parsed as a bool.

		"""
		original = self.get(key, default)
		s = original
		if type(s) in StringTypes:
			s = s.lower().strip()
		if s in (False, '', None, 0, 0.0, '0', 'false'):
			return False
		elif s in (True, 1, '1', 1.0, 'true'):
			return True
		else:
			raise ValueError, ('%r for attr %r should be a boolean value'
				' (1, 0, True, False) but is %r instead'
				% (key, self.get('Name', '(UNNAMED)'), original))
