#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (C) 2010  Étienne Loks  <etienne.loks_AT_peacefrogsDOTnet>

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.

# This program 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 General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# See the file COPYING for details.

"""
Permission backend to manage "own" objects
"""

from django.conf import settings
from django.contrib.auth.models import User

class ObjectOwnPermBackend(object):
    supports_object_permissions = True
    supports_anonymous_user = True

    def authenticate(self, username, password):
        # managed by the default backend
        return None

    def has_perm(self, user_obj, perm, obj=None):
        if not user_obj.is_authenticated():
            user_obj = User.objects.get(pk=settings.ANONYMOUS_USER_ID)

        if obj is None:
            # managed by the default backend
            return False

        try:
            # only manage "own" permissions
            assert perm.split('.')[-1].split('_')[1] == 'own'
        except (IndexError, AssertionError):
            return False

        return user_obj.has_perm(perm) and obj.is_own(user_obj)