from django import http
from django import shortcuts
from django.conf import settings

import base64


class FilterPersistMiddleware(object):
    def process_request(self, request):

        path = request.path
        if path.find('/admin/django/') != -1:  # Dont waste time if we are not in admin
            query_string = request.META['QUERY_STRING']
            if 'HTTP_REFERER' not in request.META:
                return None

            session = request.session
            if session.get('redirected', False):  # so that we dont loop once redirected
                del session['redirected']
                return None

            referrer = request.META['HTTP_REFERER'].split('?')[0]
            referrer = referrer[referrer.find('/admin/django'):len(referrer)]
            key = 'key' + path.replace('/', '_')

            if path == referrer:  # We are in same page as before
                if query_string == '':  # Filter is empty, delete it
                    if session.get(key, False):
                        del session[key]
                    return None
                request.session[key] = query_string
            elif '_directlink=1' in query_string:  # Direct link to a filter, by ourselves, so remove it
                redirect_to = path + '?' + query_string.replace('&_directlink=1', '')
                if key in session:
                    del session[key]
                return http.HttpResponseRedirect(redirect_to)
            else:  # We are are coming from another page, restore filter if available
                if session.get(key, False):
                    query_string = request.session.get(key)
                    redirect_to = path + '?' + query_string
                    request.session['redirected'] = True
                    return http.HttpResponseRedirect(redirect_to)
                else:
                    return None
        else:
            return None


class GlobalLoginMiddleware(object):
    def process_view(self, request, callback, callback_args, callback_kwargs):
        if not settings.GLOBAL_LOGIN_USER or not settings.GLOBAL_LOGIN_PASSWORD:
            # Not configured to do global auth
            return None

        if getattr(callback, 'global_login_exempt', False):
            # No global auth on this specific url
            return None

        if 'HTTP_AUTHORIZATION' in request.META:
            auth = request.META['HTTP_AUTHORIZATION'].split()
            if len(auth) != 2:
                return http.HttpResponseForbidden("Invalid authentication")
            if auth[0].lower() == "basic":
                user, pwd = base64.b64decode(auth[1]).split(':')
                if user == settings.GLOBAL_LOGIN_USER and pwd == settings.GLOBAL_LOGIN_PASSWORD:
                    return None
            # Else we fall through and request a login prompt

        response = http.HttpResponse()
        response.status_code = 401
        response['WWW-Authenticate'] = 'Basic realm={0}'.format(settings.SITEBASE)
        return response


# Ability to redirect using raise()
class RedirectException(Exception):
    def __init__(self, url):
        self.url = url


class RedirectMiddleware(object):
    def process_exception(self, request, exception):
        if isinstance(exception, RedirectException):
            return shortcuts.redirect(exception.url)