#!/usr/bin/env python
# -*- coding: utf-8  -*-
################################################################################
#
#  edbob -- Pythonic Software Framework
#  Copyright © 2010-2012 Lance Edgar
#
#  This file is part of edbob.
#
#  edbob is free software: you can redistribute it and/or modify it under the
#  terms of the GNU Affero General Public License as published by the Free
#  Software Foundation, either version 3 of the License, or (at your option)
#  any later version.
#
#  edbob is distributed in the hope that it will be useful, but WITHOUT ANY
#  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
#  FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for
#  more details.
#
#  You should have received a copy of the GNU Affero General Public License
#  along with edbob.  If not, see <http://www.gnu.org/licenses/>.
#
################################################################################

"""
``edbob.util`` -- Utilities
"""

import edbob


class requires_impl(edbob.Object):
    """
    Decorator for properties or methods defined on parent classes only for
    documentation's sake, but which in fact rely on the derived class entirely
    for implementation.

    This merely adds a helpful message to the ``NotImplementedError`` exception
    which will be raised.
    """

    is_property = False

    def __call__(self, func):
        if self.is_property:
            message = "Please define the %s.%s attribute"
        else:
            message = "Please implement the %s.%s() method"

        def wrapped(self, *args, **kwargs):
            msg = message % (self.__class__.__name__, func.__name__)
            msg += " (within the %s module)" % self.__class__.__module__
            raise NotImplementedError(msg)

        return wrapped