from django.conf import settings

REFRESH_AGE = getattr(settings, 'SESSION_COOKIE_REFRESH_AGE',
        int(settings.SESSION_COOKIE_AGE / 2))

class RefreshSessionMiddleware(object):
    """
    This middleware automatically refreshes the session after some time
    (default: settings.SESSION_COOKIE_AGE / 2).
    """
    def process_request(self, request):
        assert hasattr(request, 'session'), "RefreshSessionMiddleware " \
                "requires session middleware to be installed. Edit your " \
                "MIDDLEWARE_CLASSES setting to insert " \
                "'django.contrib.sessions.middleware.SessionMiddleware'."
        if request.session.get_expiry_age() < REFRESH_AGE:
            request.session.modified = True
        return None