from django.conf import settings
from django.contrib.contenttypes.models import ContentType
from django.contrib.auth.models import User
from django.core.signals import request_started 

try:
    from threading import local
except ImportError:
    from django.utils._threading_local import local
    
_thread_locals = local()

# The function that protect models is called on the first
# HTTP request sent to the server (see function protect_models_request
# in this file), and can not be called in this file directly 
# because of circular import.
#
# To protect models from command line, use set_current_user(my_user)
# and protect_models().

_models_are_protected = False

def get_current_user():
    return getattr(_thread_locals, 'user', None)

def set_current_user(user):
    _thread_locals.user = user
    
def del_current_user():
    del _thread_locals.user
    
def get_anonymous_user():
    if hasattr(get_anonymous_user, 'anonymous_user'):
        return get_anonymous_user.anonymous_user
    
    get_anonymous_user.anonymous_user = User.objects.get(id=settings.ANONYMOUS_USER_ID)
    return get_anonymous_user.anonymous_user 

def protect_models():
    cls_list = get_models_to_protect()
    if cls_list:
        for cls in get_models_to_protect():
                protect_model(cls)
    
    _models_are_protected = True   
    
def unprotect_models():
    for cls in get_models_to_protect():
            unprotect_model(cls)
            
    _models_are_protected = False

def get_models_to_protect():
    if hasattr(get_models_to_protect, 'cls_list'):
        return get_models_to_protect.cls_list
        
    cls_list = []
    for cls_name in settings.USE_GROUP_PERMISSIONS:
        cls_type = ContentType.objects.get(model=cls_name.lower())
        cls_list.append(cls_type.model_class())
    get_models_to_protect.cls_list = cls_list
        
    return cls_list

def protect_model(cls):  
    
    cls.old_save = cls.save
    cls.old_delete = cls.delete
    class_name = cls.__name__.lower()
    cls.save = change_security(class_name)(cls.save)
    cls.delete = change_security(class_name)(cls.delete)    
    
def unprotect_model(cls): 
    if hasattr(cls, 'old_save'):
        cls.save = cls.old_save 
        cls.delete = cls.old_delete 
        del cls.old_save    
        del cls.old_delete
        cls.safe_objects.user = None 
        cls.safe_objects.check_perm = False
        
def change_security(cls_name):
    def wrapper(func):
        def wrapped(self, *args, **kwargs):  
                        
            if self.pk and not get_current_user().has_perm('change_%s' % cls_name, self):
                raise AttributeError('User %s is not allowed to change object %s' % (get_current_user(), self))
      
            return func(self, *args, **kwargs)
        return wrapped    
    return wrapper


def protect_models_request(sender, **kwargs):
    if not _models_are_protected:
        protect_models()

request_started.connect(protect_models_request)