from django.conf import settings
from django.contrib.auth import REDIRECT_FIELD_NAME
from django.http import HttpResponseRedirect

class LoginRequiredMiddleware:
    """Middleware to redirect to the login page if the user isn't authenticated

    After successful authentication the user is redirected back to the page he
    initially wanted to access.
    """
    def __init__(self, get_response):
        self.get_response = get_response

    def __call__(self, request):
        # allow access to the login url
        response = self.get_response(request)
        if request.path == settings.LOGIN_URL:
            return response
        # redirect to the login url if the user isn't authenticated
        if not request.user.is_authenticated:
            if request.path not in (settings.LOGIN_URL,
                                    settings.LOGIN_REDIRECT_URL):
                return HttpResponseRedirect('%s?%s=%s' % (settings.LOGIN_URL,
                                                          REDIRECT_FIELD_NAME,
                                                          request.path))
            return HttpResponseRedirect(settings.LOGIN_URL)
        return response