"""Enumeration metaclass."""

class EnumMetaclass(type):

    """Metaclass for enumeration.

    To define your own enumeration, do something like

    class Color(Enum):

        red = 1

        green = 2

        blue = 3

    Now, Color.red, Color.green and Color.blue behave totally

    different: they are enumerated values, not integers.

    Enumerations cannot be instantiated; however they can be

    subclassed.

    """

    def __init__(cls, name, bases, dict):

        super(EnumMetaclass, cls).__init__(name, bases, dict)

        cls._members = []

        for attr in dict.keys():

            if not (attr.startswith('__') and attr.endswith('__')):

                enumval = EnumInstance(name, attr, dict[attr])

                setattr(cls, attr, enumval)

                cls._members.append(attr)

    def __getattr__(cls, name):

        if name == "__members__":

            return cls._members

        raise AttributeError, name

    def __repr__(cls):

        s1 = s2 = ""

        enumbases = [base.__name__ for base in cls.__bases__

                     if isinstance(base, EnumMetaclass) and not base is Enum]

        if enumbases:

            s1 = "(%s)" % ", ".join(enumbases)

        enumvalues = ["%s: %d" % (val, getattr(cls, val))

                      for val in cls._members]

        if enumvalues:

            s2 = ": {%s}" % ", ".join(enumvalues)

        return "%s%s%s" % (cls.__name__, s1, s2)

class FullEnumMetaclass(EnumMetaclass):

    """Metaclass for full enumerations.

    A full enumeration displays all the values defined in base classes.

    """

    def __init__(cls, name, bases, dict):

        super(FullEnumMetaclass, cls).__init__(name, bases, dict)

        for obj in cls.__mro__:

            if isinstance(obj, EnumMetaclass):

                for attr in obj._members:

                    # XXX inefficient

                    if not attr in cls._members:

                        cls._members.append(attr)

class EnumInstance(int):

    """Class to represent an enumeration value.

    EnumInstance('Color', 'red', 12) prints as 'Color.red' and behaves

    like the integer 12 when compared, but doesn't support arithmetic.

    XXX Should it record the actual enumeration rather than just its

    name?

    """

    def __new__(cls, classname, enumname, value):

        return int.__new__(cls, value)

    def __init__(self, classname, enumname, value):

        self.__classname = classname

        self.__enumname = enumname

    def __repr__(self):

        return "EnumInstance(%s, %s, %d)" % (self.__classname, self.__enumname,

                                             self)

    def __str__(self):

        return "%s.%s" % (self.__classname, self.__enumname)

class Enum:

    __metaclass__ = EnumMetaclass

class FullEnum:

    __metaclass__ = FullEnumMetaclass

def _test():

    class Color(Enum):

        red = 1

        green = 2

        blue = 3

    print Color.red

    print repr(Color.red)

    print Color.red == Color.red

    print Color.red == Color.blue

    print Color.red == 1

    print Color.red == 2

    class ExtendedColor(Color):

        white = 0

        orange = 4

        yellow = 5

        purple = 6

        black = 7

    print ExtendedColor.orange

    print ExtendedColor.red

    print Color.red == ExtendedColor.red

    class OtherColor(Enum):

        white = 4

        blue = 5

    class MergedColor(Color, OtherColor):

        pass

    print MergedColor.red

    print MergedColor.white

    print Color

    print ExtendedColor

    print OtherColor

    print MergedColor

def _test2():

    class Color(FullEnum):

        red = 1

        green = 2

        blue = 3

    print Color.red

    print repr(Color.red)

    print Color.red == Color.red

    print Color.red == Color.blue

    print Color.red == 1

    print Color.red == 2

    class ExtendedColor(Color):

        white = 0

        orange = 4

        yellow = 5

        purple = 6

        black = 7

    print ExtendedColor.orange

    print ExtendedColor.red

    print Color.red == ExtendedColor.red

    class OtherColor(FullEnum):

        white = 4

        blue = 5

    class MergedColor(Color, OtherColor):

        pass

    print MergedColor.red

    print MergedColor.white

    print Color

    print ExtendedColor

    print OtherColor

    print MergedColor

if __name__ == '__main__':

    _test()

    _test2()