from django.http import HttpResponseRedirect
from django.conf import settings
from re import compile

from django.core.urlresolvers import reverse

EXEMPT_URLS = [compile(settings.LOGIN_URL.lstrip('/'))]
if hasattr(settings, 'LOGIN_EXEMPT_URLS'):
    EXEMPT_URLS += [compile(expr) for expr in settings.LOGIN_EXEMPT_URLS]

class LoginRequiredMiddleware:
    """
    Middleware that requires a user to be authenticated to view any page other
    than reverse(LOGIN_URL_NAME). Exemptions to this requirement can optionally
    be specified in settings via a list of regular expressions in
    LOGIN_EXEMPT_URLS (which you can copy from your urls.py).
    Requires authentication middleware and template context processors to be
    loaded. You'll get an error if they aren't.
    """
    def process_request(self, request):
        assert hasattr(request, 'user'), "The Login Required middleware requires authentication middleware to be installed. Edit your MIDDLEWARE_CLASSES setting to insert 'django.contrib.auth.middlware.AuthenticationMiddleware'. If that doesn't work, ensure your TEMPLATE_CONTEXT_PROCESSORS setting includes 'django.core.context_processors.auth'."
        if not request.user.is_authenticated():
            path = request.path.lstrip('/')
            if not any(m.match(path) for m in EXEMPT_URLS):
                return HttpResponseRedirect(settings.LOGIN_URL + "?next=" + request.path)