python ACL decorators

acl_decorators.py

from copy import copy

class NotAllowedError(Exception):
    code = 503
    def __init__(self, *args, **kwargs):
        super(NotAllowedError, self).__init__(*args, **kwargs)

def _base_decorator(check_rights_function, *decorator_args, **decorator_kwargs):
    def real_decorator(function):
        def wrapper(handler, *function_args, **function_kwargs):
            """:type handler: UserSessionHandlerMixin"""

            # try to take user_id from handler is not set
            if 'user_id' not in decorator_kwargs.keys():
                decorator_kwargs['user_id'] = handler.user_id

            # combine keyword arguments passed to function and decorator
            # decorator arguments will have higher priority
            can_kwargs = copy(function_kwargs)
            can_kwargs.update(decorator_kwargs)

            if check_rights_function(*decorator_args, **can_kwargs):
                function(handler, *function_args, **function_kwargs)
            else:
                raise NotAllowedError("Sorry, you don't have rights to do this action")

        return wrapper

    return real_decorator


def decorator_can_update_product(*decorator_args, **decorator_kwargs):
    return _base_decorator(can_update_product, *decorator_args, **decorator_kwargs)

def can_update_product(product_id = None, user_id = None, **kwargs):
    print 'checking if user',user_id,'can update product',product_id,'...'
    return False
    # real code should look like:
    #   product = get_product(product_id)
    #   return product.user_id == user_id

def decorator_can_create_product(*decorator_args, **decorator_kwargs):
    return _base_decorator(can_create_product, *decorator_args, **decorator_kwargs)

def can_create_product(user_id = None, **kwargs):
    print 'checking if user',user_id,'can create product','...'
    return True
    # real code should look like:
    #   product = get_product(product_id)
    #   return product.user_id == user_id








########################## TEST ##########################

class Handler:
    user_id = 2 # in real app we get user_id from session

    @decorator_can_create_product()
    def create(self):
        print 'Well done! Created new product!'

    # You can override params like:
    #   @decorator_can_update_product(user_id = 33)
    #   or
    #   @decorator_can_update_product(product_id = 33, user_id = 7879)
    @decorator_can_update_product()
    def update(self, product_id):
        print 'Well done! Updated product ' + str(product_id)


# in real app, router will do this call  ...
try:
    Handler().create()
    Handler().update(product_id = 111)
except NotAllowedError as e:
    print 'Error with code {}: {}'.format(e.code, e)