""" See the expected/unexpected behaviour at the end of the file. It behaves perfeclty well in
python 3.3

See:
    - Dict access in `MessageMeta`.__new__
    - End of the file showing the weird effect

Has been tested in:
    - py 3.2.2 - Failed
    - py 3.2.3 - Failed
    - py 3.3.2 - Succeeded
"""


__supported_types__ = (int, float, bool, str, bytes)
type_string = ', '.join([typ.__name__ for typ in __supported_types__])


class Attribute(object):

    __slots__ = ['_type', '_optional', '_value']

    def __init__(self, attr_type, optional=False):
        if attr_type not in __supported_types__:
            raise TypeError("Expected any of ({0}) as attr_type. Provided type ({1}) either not "
                            "supported or 'not yet' supported".format(type_string,
                                                                      attr_type.__name__))

        self._type     = attr_type
        self._optional = optional
        self._value    = None

    def __get__(self, ref, owner):
        return self._value

    def __set__(self, ref, value):
        if not isinstance(value, self._type):
            raise TypeError("Expected type is ({0}), "
                            "instead received ({1})".format(type(value).__name__,
                                                            self._type.__name__))
        else:
            self._value = value

    def __delete__(self, ref):
        raise Exception("You can not remove a messages Attribute, as it is part of the Message"
                        " definition")

class MessageMeta(type):

    def __new__(meta, name, parents, attrs):
        __metadict__ = {}

        """ By just commenting out the following lines, that access the dict_proxy to the attrs to
        become the __dict__, everything works just fine. Python 3.3 works.
        """
        for name, value in attrs.items():
            if isinstance(value, Attribute):
                __metadict__[name] = value

        attrs['__slots__']    = []  # Ensure all children have a empty def of this
        attrs['__metadict__'] = __metadict__

        return super(MessageMeta, meta).__new__(meta, name, parents, attrs)

class Message(object, metaclass=MessageMeta):
    pass


"""  Failed test case """
class TestMessage(Message):
    first_attr   = Attribute(int, False)
    secnond_attr = Attribute(str, True)

c = TestMessage()
type(c)                 # 'first_attr' instead of expected 'TestMessage' yet...
isinstance(c, Message)  # ...True