from urllib import urlencode

from urlparse import urlparse, urlunparse, parse_qsl

from django.contrib.auth import authenticate, login

from ldt.security import set_current_user

class CASAuthenticationMiddleware(object):

    '''

        Middleware class for authenticating a user through a CAS Server via the CAS Proxy protocol.

        The request must have a "cas_ticket" argument that contains the CAS Proxy ticket to be validated.

        Requires django-cas-ng authentication backend.

    '''

    def process_request(self, request):

        ticket = request.GET.get("casticket")

        if ticket is not None:

            parsed_url = urlparse(request.build_absolute_uri())

            # editing ticket parameter out of the request

            new_query_params = urlencode([param for param in parse_qsl(parsed_url.query) if str(param[0]) != "casticket"])

            service = urlunparse((

                parsed_url.scheme,

                parsed_url.netloc,

                parsed_url.path,

                parsed_url.params,

                new_query_params,

                parsed_url.fragment

            ))

            user = authenticate(ticket=ticket, service=service, request=request)

            if user is None:

                return False

            request.user = user

            login(request, user)

            set_current_user(user)