def apply_ args kwargs Decorator for per-view rules applying Usage app

def apply_(*args, **kwargs):
    """
    Decorator for per-view rules applying
    
    Usage:
        
        @apply_('rule1', 'rule2', 'rule3', default_context={'key': 'foo'})
        def some_view(request, arg1, arg2):
            pass
    """
    rules = []
    for arg in args:
        if isinstance(arg, (list, tuple)):
            rules += list(arg)
        elif isinstance(arg, str):
            rules += [arg]
        else:
            raise ValueError("Wrong arg %s for apply_" % (arg,))
    default_context = None
    if kwargs:
        if kwargs.keys() != ['default_context']:
            raise ValueError('Only default_context is allowed keyword argument')
        else:
            default_context = kwargs['default_context']
    
    def checker(view_func):
        def wrapper(*args, **kwargs):
            if default_context is not None:
                extra = default_context
            else:    
                extra = {}
            extra['caller'] = view_func.__name__
            keys = getargspec(view_func).args
            for i, key in enumerate(keys):
                try:
                    extra[key] = args[i]
                except IndexError:
                    extra[key] = kwargs[key]
            if 'city' not in extra:
                raise ValueError('Each rule requires city in args')
            city = extra['city']
            for rule_name in rules:
                rule = RULES[rule_name]
                ok, reason = rule(city, extra)
                if not ok:
                    return HttpResponse(unicode(reason),
                                        mimetype='text/plain',
                                        status=404)
            return view_func(*args, **kwargs)
        view_func._applied_rules = rules
        return wraps(view_func)(wrapper)
    return checker