from django.conf import settings

from django.db.models import Manager

from django.contrib.contenttypes.models import ContentType

from guardian.shortcuts import assign, remove_perm, get_objects_for_user

from guardian.core import ObjectPermissionChecker

def protect_models(user):

    for cls in get_models_to_protect():

            protect_model(cls, user)

def unprotect_models():

    for cls in get_models_to_protect():

            unprotect_model(cls)

def get_models_to_protect():        

    to_protect = []

    for cls_name in settings.USE_GROUP_PERMISSIONS:

        cls_type = ContentType.objects.get(app_label="ldt_utils", model=cls_name.lower())

        to_protect.append(cls_type.model_class())

    return to_protect

def protect_model(cls, user):

    cls.base_objects = cls.objects

    cls.objects = SafeManager(cls, user)

    cls.base_save = cls.save

    cls.save = save_security(user, cls.__name__.lower())(cls.save)

def unprotect_model(cls):    

    if hasattr(cls, 'base_objects'):

        cls.objects = cls.base_objects

        cls.save = cls.base_save

        del cls.base_objects    

        del cls.base_save

class SafeManager(Manager):

    def __init__(self, cls, user=None):

        super(SafeManager, self).__init__()

        self.model_name = cls.__name__.lower()

        self.model = cls  

        if user:

            self.check_perm_for(user)

        else:

            self.user = None

            self.checker = None     

    def check_perm_for(self, user):

        self.user = user

        self.checker = ObjectPermissionChecker(self.user)

    def stop_checking(self):

        self.user = None

        self.checker = None

    def has_user(self):

        return self.user != None        

    def get_query_set(self):

        if not self.has_user():

            raise AttributeError("A user has to be chosen to check permissions.")

        user_objects = get_objects_for_user(self.user, 'ldt_utils.view_%s' % self.model_name)

        return user_objects    

def save_security(user, cls_name):

    def wrapper(func):

        def wrapped(self, *args, **kwargs):

            if self.pk and not user.has_perm('change_%s' % cls_name, self):

                raise AttributeError('User %s is not allowed to change object %s' % (user, self))

            return func(self, *args, **kwargs)

        return wrapped

    return wrapper

            remove_perm('change_project', group, project)