views.py

"""
Student Views
"""
import datetime
import logging
import re
import uuid
import time
import json
from collections import defaultdict
from pytz import UTC

from django.conf import settings
from django.contrib.auth import logout, authenticate, login
from django.contrib.auth.models import User, AnonymousUser
from django.contrib.auth.decorators import login_required
from django.contrib.auth.views import password_reset_confirm
from django.contrib import messages
from django.core.context_processors import csrf
from django.core.mail import send_mail
from django.core.urlresolvers import reverse
from django.core.validators import validate_email, validate_slug, ValidationError
from django.db import IntegrityError, transaction
from django.http import (HttpResponse, HttpResponseBadRequest, HttpResponseForbidden,
                         Http404)
from django.shortcuts import redirect
from django.utils.translation import ungettext
from django_future.csrf import ensure_csrf_cookie
from django.utils.http import cookie_date, base36_to_int
from django.utils.translation import ugettext as _, get_language
from django.views.decorators.cache import never_cache
from django.views.decorators.http import require_POST, require_GET

from django.db.models.signals import post_save
from django.dispatch import receiver

from django.template.response import TemplateResponse

from ratelimitbackend.exceptions import RateLimitException

from edxmako.shortcuts import render_to_response, render_to_string
from mako.exceptions import TopLevelLookupException

from course_modes.models import CourseMode
from student.models import (
    Registration, UserProfile, PendingNameChange,
    PendingEmailChange, CourseEnrollment, unique_id_for_user,
    CourseEnrollmentAllowed, UserStanding, LoginFailures,
    create_comments_service_user, PasswordHistory, UserSignupSource
)
from student.forms import PasswordResetFormNoActive

from verify_student.models import SoftwareSecurePhotoVerification, MidcourseReverificationWindow
from certificates.models import CertificateStatuses, certificate_status_for_student
from dark_lang.models import DarkLangConfig

from xmodule.modulestore.django import modulestore
from opaque_keys import InvalidKeyError
from opaque_keys.edx.locations import SlashSeparatedCourseKey
from xmodule.modulestore import ModuleStoreEnum

from collections import namedtuple

from courseware.courses import get_courses, sort_by_announcement
from courseware.access import has_access

from django_comment_common.models import Role

from external_auth.models import ExternalAuthMap
import external_auth.views

from bulk_email.models import Optout, CourseAuthorization
import shoppingcart
from user_api.models import UserPreference
from lang_pref import LANGUAGE_KEY

import track.views

from dogapi import dog_stats_api

from util.json_request import JsonResponse
from util.bad_request_rate_limiter import BadRequestRateLimiter

from microsite_configuration import microsite

from util.password_policy_validators import (
    validate_password_length, validate_password_complexity,
    validate_password_dictionary
)

from third_party_auth import pipeline, provider
from xmodule.error_module import ErrorDescriptor
from shoppingcart.models import CourseRegistrationCode

import analytics
from eventtracking import tracker


log = logging.getLogger("edx.student")
AUDIT_LOG = logging.getLogger("audit")

ReverifyInfo = namedtuple('ReverifyInfo', 'course_id course_name course_number date status display')  # pylint: disable=C0103


def csrf_token(context):
    """A csrf token that can be included in a form."""
    token = context.get('csrf_token', '')
    if token == 'NOTPROVIDED':
        return ''
    return (u'<div style="display:none"><input type="hidden"'
            ' name="csrfmiddlewaretoken" value="%s" /></div>' % (token))


# NOTE: This view is not linked to directly--it is called from
# branding/views.py:index(), which is cached for anonymous users.
# This means that it should always return the same thing for anon
# users. (in particular, no switching based on query params allowed)
def index(request, extra_context=None, user=AnonymousUser()):
    """
    Render the edX main page.

    extra_context is used to allow immediate display of certain modal windows, eg signup,
    as used by external_auth.
    """
    if extra_context is None:
        extra_context = {}
    # The course selection work is done in courseware.courses.
    domain = settings.FEATURES.get('FORCE_UNIVERSITY_DOMAIN')  # normally False
    # do explicit check, because domain=None is valid
    if domain is False:
        domain = request.META.get('HTTP_HOST')

    courses = get_courses(user, domain=domain)
    courses = sort_by_announcement(courses)

    context = {'courses': courses}

    context.update(extra_context)
    return render_to_response('index.html', context)


def embargo(_request):
    """
    Render the embargo page.

    Explains to the user why they are not able to access a particular embargoed course.
    Tries to use the themed version, but fall back to the default if not found.
    """
    try:
        if settings.FEATURES["USE_CUSTOM_THEME"]:
            return render_to_response("static_templates/theme-embargo.html")
    except TopLevelLookupException:
        pass
    return render_to_response("static_templates/embargo.html")


def process_survey_link(survey_link, user):
    """
    If {UNIQUE_ID} appears in the link, replace it with a unique id for the user.
    Currently, this is sha1(user.username).  Otherwise, return survey_link.
    """
    return survey_link.format(UNIQUE_ID=unique_id_for_user(user))


def cert_info(user, course):
    """
    Get the certificate info needed to render the dashboard section for the given
    student and course.  Returns a dictionary with keys:

    'status': one of 'generating', 'ready', 'notpassing', 'processing', 'restricted'
    'show_download_url': bool
    'download_url': url, only present if show_download_url is True
    'show_disabled_download_button': bool -- true if state is 'generating'
    'show_survey_button': bool
    'survey_url': url, only if show_survey_button is True
    'grade': if status is not 'processing'
    """
    if not course.may_certify():
        return {}

    return _cert_info(user, course, certificate_status_for_student(user, course.id))


def reverification_info(course_enrollment_pairs, user, statuses):
    """
    Returns reverification-related information for *all* of user's enrollments whose
    reverification status is in status_list

    Args:
        course_enrollment_pairs (list): list of (course, enrollment) tuples
        user (User): the user whose information we want
        statuses (list): a list of reverification statuses we want information for
            example: ["must_reverify", "denied"]

    Returns:
        dictionary of lists: dictionary with one key per status, e.g.
            dict["must_reverify"] = []
            dict["must_reverify"] = [some information]
    """
    reverifications = defaultdict(list)
    for (course, enrollment) in course_enrollment_pairs:
        info = single_course_reverification_info(user, course, enrollment)
        if info:
            reverifications[info.status].append(info)

    # Sort the data by the reverification_end_date
    for status in statuses:
        if reverifications[status]:
            reverifications[status].sort(key=lambda x: x.date)
    return reverifications


def single_course_reverification_info(user, course, enrollment):  # pylint: disable=invalid-name
    """Returns midcourse reverification-related information for user with enrollment in course.

    If a course has an open re-verification window, and that user has a verified enrollment in
    the course, we return a tuple with relevant information. Returns None if there is no info..

    Args:
        user (User): the user we want to get information for
        course (Course): the course in which the student is enrolled
        enrollment (CourseEnrollment): the object representing the type of enrollment user has in course

    Returns:
        ReverifyInfo: (course_id, course_name, course_number, date, status)
        OR, None: None if there is no re-verification info for this enrollment
    """
    window = MidcourseReverificationWindow.get_window(course.id, datetime.datetime.now(UTC))

    # If there's no window OR the user is not verified, we don't get reverification info
    if (not window) or (enrollment.mode != "verified"):
        return None
    return ReverifyInfo(
        course.id, course.display_name, course.number,
        window.end_date.strftime('%B %d, %Y %X %p'),
        SoftwareSecurePhotoVerification.user_status(user, window)[0],
        SoftwareSecurePhotoVerification.display_status(user, window),
    )


def get_course_enrollment_pairs(user, course_org_filter, org_filter_out_set):
    """
    Get the relevant set of (Course, CourseEnrollment) pairs to be displayed on
    a student's dashboard.
    """
    for enrollment in CourseEnrollment.enrollments_for_user(user):
        course = modulestore().get_course(enrollment.course_id)
        if course and not isinstance(course, ErrorDescriptor):

            # if we are in a Microsite, then filter out anything that is not
            # attributed (by ORG) to that Microsite
            if course_org_filter and course_org_filter != course.location.org:
                continue
            # Conversely, if we are not in a Microsite, then let's filter out any enrollments
            # with courses attributed (by ORG) to Microsites
            elif course.location.org in org_filter_out_set:
                continue

            yield (course, enrollment)
        else:
            log.error("User {0} enrolled in {2} course {1}".format(
                user.username, enrollment.course_id, "broken" if course else "non-existent"
            ))


def _cert_info(user, course, cert_status):
    """
    Implements the logic for cert_info -- split out for testing.
    """
    # simplify the status for the template using this lookup table
    template_state = {
        CertificateStatuses.generating: 'generating',
        CertificateStatuses.regenerating: 'generating',
        CertificateStatuses.downloadable: 'ready',
        CertificateStatuses.notpassing: 'notpassing',
        CertificateStatuses.restricted: 'restricted',
    }

    default_status = 'processing'

    default_info = {'status': default_status,
                    'show_disabled_download_button': False,
                    'show_download_url': False,
                    'show_survey_button': False,
                    }

    if cert_status is None:
        return default_info

    is_hidden_status = cert_status['status'] in ('unavailable', 'processing', 'generating', 'notpassing')

    if course.certificates_display_behavior == 'early_no_info' and is_hidden_status:
        return None

    status = template_state.get(cert_status['status'], default_status)

    status_dict = {
        'status': status,
        'show_download_url': status == 'ready',
        'show_disabled_download_button': status == 'generating',
        'mode': cert_status.get('mode', None)
    }

    if (status in ('generating', 'ready', 'notpassing', 'restricted') and
            course.end_of_course_survey_url is not None):
        status_dict.update({
            'show_survey_button': True,
            'survey_url': process_survey_link(course.end_of_course_survey_url, user)})
    else:
        status_dict['show_survey_button'] = False

    if status == 'ready':
        if 'download_url' not in cert_status:
            log.warning("User %s has a downloadable cert for %s, but no download url",
                        user.username, course.id)
            return default_info
        else:
            status_dict['download_url'] = cert_status['download_url']

    if status in ('generating', 'ready', 'notpassing', 'restricted'):
        if 'grade' not in cert_status:
            # Note: as of 11/20/2012, we know there are students in this state-- cs169.1x,
            # who need to be regraded (we weren't tracking 'notpassing' at first).
            # We can add a log.warning here once we think it shouldn't happen.
            return default_info
        else:
            status_dict['grade'] = cert_status['grade']

    return status_dict


@ensure_csrf_cookie
def signin_user(request):
    """
    This view will display the non-modal login form
    """
    if (settings.FEATURES['AUTH_USE_CERTIFICATES'] and
            external_auth.views.ssl_get_cert_from_request(request)):
        # SSL login doesn't require a view, so redirect
        # branding and allow that to process the login if it
        # is enabled and the header is in the request.
        return external_auth.views.redirect_with_get('root', request.GET)
    if settings.FEATURES.get('AUTH_USE_CAS'):
        # If CAS is enabled, redirect auth handling to there
        return redirect(reverse('cas-login'))
    if request.user.is_authenticated():
        return redirect(reverse('dashboard'))

    context = {
        'course_id': request.GET.get('course_id'),
        'enrollment_action': request.GET.get('enrollment_action'),
        # Bool injected into JS to submit form if we're inside a running third-
        # party auth pipeline; distinct from the actual instance of the running
        # pipeline, if any.
        'pipeline_running': 'true' if pipeline.running(request) else 'false',
        'platform_name': microsite.get_value(
            'platform_name',
            settings.PLATFORM_NAME
        ),
    }

    return render_to_response('login.html', context)


@ensure_csrf_cookie
def register_user(request, extra_context=None):
    """
    This view will display the non-modal registration form
    """
    if request.user.is_authenticated():
        return redirect(reverse('dashboard'))
    if settings.FEATURES.get('AUTH_USE_CERTIFICATES_IMMEDIATE_SIGNUP'):
        # Redirect to branding to process their certificate if SSL is enabled
        # and registration is disabled.
        return external_auth.views.redirect_with_get('root', request.GET)

    context = {
        'course_id': request.GET.get('course_id'),
        'email': '',
        'enrollment_action': request.GET.get('enrollment_action'),
        'name': '',
        'running_pipeline': None,
        'platform_name': microsite.get_value(
            'platform_name',
            settings.PLATFORM_NAME
        ),
        'selected_provider': '',
        'username': '',
    }

    # We save this so, later on, we can determine what course motivated a user's signup
    # if they actually complete the registration process
    request.session['registration_course_id'] = context['course_id']

    if extra_context is not None:
        context.update(extra_context)

    if context.get("extauth_domain", '').startswith(external_auth.views.SHIBBOLETH_DOMAIN_PREFIX):
        return render_to_response('register-shib.html', context)

    # If third-party auth is enabled, prepopulate the form with data from the
    # selected provider.
    if microsite.get_value('ENABLE_THIRD_PARTY_AUTH', settings.FEATURES.get('ENABLE_THIRD_PARTY_AUTH')) and pipeline.running(request):
        running_pipeline = pipeline.get(request)
        current_provider = provider.Registry.get_by_backend_name(running_pipeline.get('backend'))
        overrides = current_provider.get_register_form_data(running_pipeline.get('kwargs'))
        overrides['running_pipeline'] = running_pipeline
        overrides['selected_provider'] = current_provider.NAME
        context.update(overrides)

    return render_to_response('register.html', context)


def complete_course_mode_info(course_id, enrollment):
    """
    We would like to compute some more information from the given course modes
    and the user's current enrollment

    Returns the given information:
        - whether to show the course upsell information
        - numbers of days until they can't upsell anymore
    """
    modes = CourseMode.modes_for_course_dict(course_id)
    mode_info = {'show_upsell': False, 'days_for_upsell': None}
    # we want to know if the user is already verified and if verified is an
    # option
    if 'verified' in modes and enrollment.mode != 'verified':
        mode_info['show_upsell'] = True
        # if there is an expiration date, find out how long from now it is
        if modes['verified'].expiration_datetime:
            today = datetime.datetime.now(UTC).date()
            mode_info['days_for_upsell'] = (modes['verified'].expiration_datetime.date() - today).days

    return mode_info


def is_course_blocked(request, redeemed_registration_codes, course_key):
    """Checking either registration is blocked or not ."""
    blocked = False
    for redeemed_registration in redeemed_registration_codes:
        if not getattr(redeemed_registration.invoice, 'is_valid'):
            blocked = True
            # disabling email notifications for unpaid registration courses
            Optout.objects.get_or_create(user=request.user, course_id=course_key)
            log.info(u"User {0} ({1}) opted out of receiving emails from course {2}".format(request.user.username, request.user.email, course_key))
            track.views.server_track(request, "change-email1-settings", {"receive_emails": "no", "course": course_key.to_deprecated_string()}, page='dashboard')
            break

    return blocked


@login_required
@ensure_csrf_cookie
def dashboard(request):
    user = request.user

    # for microsites, we want to filter and only show enrollments for courses within
    # the microsites 'ORG'
    course_org_filter = microsite.get_value('course_org_filter')

    # Let's filter out any courses in an "org" that has been declared to be
    # in a Microsite
    org_filter_out_set = microsite.get_all_orgs()

    # remove our current Microsite from the "filter out" list, if applicable
    if course_org_filter:
        org_filter_out_set.remove(course_org_filter)

    # Build our (course, enrollment) list for the user, but ignore any courses that no
    # longer exist (because the course IDs have changed). Still, we don't delete those
    # enrollments, because it could have been a data push snafu.
    course_enrollment_pairs = list(get_course_enrollment_pairs(user, course_org_filter, org_filter_out_set))

    course_optouts = Optout.objects.filter(user=user).values_list('course_id', flat=True)

    message = ""
    if not user.is_active:
        message = render_to_string('registration/activate_account_notice.html', {'email': user.email})

    # Global staff can see what courses errored on their dashboard
    staff_access = False
    errored_courses = {}
    if has_access(user, 'staff', 'global'):
        # Show any courses that errored on load
        staff_access = True
        errored_courses = modulestore().get_errored_courses()

    show_courseware_links_for = frozenset(course.id for course, _enrollment in course_enrollment_pairs
                                          if has_access(request.user, 'load', course))

    course_modes = {course.id: complete_course_mode_info(course.id, enrollment) for course, enrollment in course_enrollment_pairs}
    cert_statuses = {course.id: cert_info(request.user, course) for course, _enrollment in course_enrollment_pairs}

    # only show email settings for Mongo course and when bulk email is turned on
    show_email_settings_for = frozenset(
        course.id for course, _enrollment in course_enrollment_pairs if (
            settings.FEATURES['ENABLE_INSTRUCTOR_EMAIL'] and
            modulestore().get_modulestore_type(course.id) != ModuleStoreEnum.Type.xml and
            CourseAuthorization.instructor_email_enabled(course.id)
        )
    )

    # Verification Attempts
    # Used to generate the "you must reverify for course x" banner
    verification_status, verification_msg = SoftwareSecurePhotoVerification.user_status(user)

    # Gets data for midcourse reverifications, if any are necessary or have failed
    statuses = ["approved", "denied", "pending", "must_reverify"]
    reverifications = reverification_info(course_enrollment_pairs, user, statuses)

    show_refund_option_for = frozenset(course.id for course, _enrollment in course_enrollment_pairs
                                       if _enrollment.refundable())

    block_courses = frozenset(course.id for course, enrollment in course_enrollment_pairs
                              if is_course_blocked(request, CourseRegistrationCode.objects.filter(course_id=course.id, registrationcoderedemption__redeemed_by=request.user), course.id))

    enrolled_courses_either_paid = frozenset(course.id for course, _enrollment in course_enrollment_pairs
                                             if _enrollment.is_paid_course())
    # get info w.r.t ExternalAuthMap
    external_auth_map = None
    try:
        external_auth_map = ExternalAuthMap.objects.get(user=user)
    except ExternalAuthMap.DoesNotExist:
        pass

    # If there are *any* denied reverifications that have not been toggled off,
    # we'll display the banner
    denied_banner = any(item.display for item in reverifications["denied"])

    language_options = DarkLangConfig.current().released_languages_list

    # add in the default language if it's not in the list of released languages
    if settings.LANGUAGE_CODE not in language_options:
        language_options.append(settings.LANGUAGE_CODE)
        # Re-alphabetize language options
        language_options.sort()

    # try to get the prefered language for the user
    cur_pref_lang_code = UserPreference.get_preference(request.user, LANGUAGE_KEY)
    # try and get the current language of the user
    cur_lang_code = get_language()
    if cur_pref_lang_code and cur_pref_lang_code in settings.LANGUAGE_DICT:
        # if the user has a preference, get the name from the code
        current_language = settings.LANGUAGE_DICT[cur_pref_lang_code]
    elif cur_lang_code in settings.LANGUAGE_DICT:
        # if the user's browser is showing a particular language,
        # use that as the current language
        current_language = settings.LANGUAGE_DICT[cur_lang_code]
    else:
        # otherwise, use the default language
        current_language = settings.LANGUAGE_DICT[settings.LANGUAGE_CODE]

    context = {
        'course_enrollment_pairs': course_enrollment_pairs,
        'course_optouts': course_optouts,
        'message': message,
        'external_auth_map': external_auth_map,
        'staff_access': staff_access,
        'errored_courses': errored_courses,
        'show_courseware_links_for': show_courseware_links_for,
        'all_course_modes': course_modes,
        'cert_statuses': cert_statuses,
        'show_email_settings_for': show_email_settings_for,
        'reverifications': reverifications,
        'verification_status': verification_status,
        'verification_msg': verification_msg,
        'show_refund_option_for': show_refund_option_for,
        'block_courses': block_courses,
        'denied_banner': denied_banner,
        'billing_email': settings.PAYMENT_SUPPORT_EMAIL,
        'language_options': language_options,
        'current_language': current_language,
        'current_language_code': cur_lang_code,
        'user': user,
        'duplicate_provider': None,
        'logout_url': reverse(logout_user),
        'platform_name': settings.PLATFORM_NAME,
        'enrolled_courses_either_paid': enrolled_courses_either_paid,
        'provider_states': [],
    }

    if microsite.get_value('ENABLE_THIRD_PARTY_AUTH', settings.FEATURES.get('ENABLE_THIRD_PARTY_AUTH')):
        context['duplicate_provider'] = pipeline.get_duplicate_provider(messages.get_messages(request))
        context['provider_user_states'] = pipeline.get_provider_user_states(user)

    return render_to_response('dashboard.html', context)


def try_change_enrollment(request):
    """
    This method calls change_enrollment if the necessary POST
    parameters are present, but does not return anything in most cases. It
    simply logs the result or exception. This is usually
    called after a registration or login, as secondary action.
    It should not interrupt a successful registration or login.
    """
    if 'enrollment_action' in request.POST:
        try:
            enrollment_response = change_enrollment(request)
            # There isn't really a way to display the results to the user, so we just log it
            # We expect the enrollment to be a success, and will show up on the dashboard anyway
            log.info(
                "Attempted to automatically enroll after login. Response code: {0}; response body: {1}".format(
                    enrollment_response.status_code,
                    enrollment_response.content
                )
            )
            # Hack: since change_enrollment delivers its redirect_url in the content
            # of its response, we check here that only the 200 codes with content
            # will return redirect_urls.
            if enrollment_response.status_code == 200 and enrollment_response.content != '':
                return enrollment_response.content
        except Exception as exc:  # pylint: disable=broad-except
            log.exception("Exception automatically enrolling after login: %s", exc)


@require_POST
def change_enrollment(request, auto_register=False, check_access=True):
    """
    Modify the enrollment status for the logged-in user.

    The request parameter must be a POST request (other methods return 405)
    that specifies course_id and enrollment_action parameters. If course_id or
    enrollment_action is not specified, if course_id is not valid, if
    enrollment_action is something other than "enroll" or "unenroll", if
    enrollment_action is "enroll" and enrollment is closed for the course, or
    if enrollment_action is "unenroll" and the user is not enrolled in the
    course, a 400 error will be returned. If the user is not logged in, 403
    will be returned; it is important that only this case return 403 so the
    front end can redirect the user to a registration or login page when this
    happens. This function should only be called from an AJAX request or
    as a post-login/registration helper, so the error messages in the responses
    should never actually be user-visible.
    The original version of the change enrollment handler,
    which does NOT perform auto-registration.

    TODO (ECOM-16): We created a second variation of this handler that performs
    auto-registration for an AB-test.  Depending on the results of that test,
    we should make the winning implementation the default.

    Args:
        request (`Request`): The Django request object

    Keyword Args:
        auto_register (boolean): If True, auto-register the user
            for a default course mode when they first enroll
            before sending them to the "choose your track" page

    Returns:
        Response

    """
    # Sets the auto_register flag, if that's desired
    # TODO (ECOM-16): Remove this once the auto-registration A/B test completes
    # If a user is in the experimental condition (auto-registration enabled),
    # immediately set a session flag so they stay in the experimental condition.
    # We keep them in the experimental condition even if later on the user
    # tries to register using the control URL (e.g. because of a redirect from the login page,
    # which is hard-coded to use the control URL).
    if auto_register:
        request.session['auto_register'] = True
    if request.session.get('auto_register') and not auto_register:
        auto_register = True

    # Get the user
    user = request.user

    # Ensure the user is authenticated
    if not user.is_authenticated():
        return HttpResponseForbidden()

    # Ensure we received a course_id
    action = request.POST.get("enrollment_action")
    if 'course_id' not in request.POST:
        return HttpResponseBadRequest(_("Course id not specified"))

    try:
        course_id = SlashSeparatedCourseKey.from_deprecated_string(request.POST.get("course_id"))
    except InvalidKeyError:
        log.warning(
            "User {username} tried to {action} with invalid course id: {course_id}".format(
                username=user.username,
                action=action,
                course_id=request.POST.get("course_id")
            )
        )
        return HttpResponseBadRequest(_("Invalid course id"))

    # Don't execute auto-register for the set of courses excluded from auto-registration
    # TODO (ECOM-16): Remove this once the auto-registration A/B test completes
    # We've agreed to exclude certain courses from the A/B test.  If we find ourselves
    # registering for one of these courses, immediately switch to the control.
    if unicode(course_id) in getattr(settings, 'AUTO_REGISTRATION_AB_TEST_EXCLUDE_COURSES', []):
        auto_register = False
        if 'auto_register' in request.session:
            del request.session['auto_register']

    if action == "enroll":
        # Make sure the course exists
        # We don't do this check on unenroll, or a bad course id can't be unenrolled from
        if not modulestore().has_course(course_id):
            log.warning("User {0} tried to enroll in non-existent course {1}"
                        .format(user.username, course_id))
            return HttpResponseBadRequest(_("Course id is invalid"))

        # We use this flag to determine which condition of an AB-test
        # for auto-registration we're currently in.
        # (We have two URLs that both point to this view, but vary the
        # value of `auto_register`)
        # In the auto-registration case, we automatically register the student
        # as "honor" before allowing them to choose a track.
        # TODO (ECOM-16): Once the auto-registration AB-test is complete, delete
        # one of these two conditions and remove the `auto_register` flag.
        if auto_register:
            available_modes = CourseMode.modes_for_course_dict(course_id)

            # Handle professional ed as a special case.
            # If professional ed is included in the list of available modes,
            # then do NOT automatically enroll the student (we want them to pay first!)
            # By convention, professional ed should be the *only* available course mode,
            # if it's included at all -- anything else is a misconfiguration.  But if someone
            # messes up and adds an additional course mode, we err on the side of NOT
            # accidentally giving away free courses.
            if "professional" not in available_modes:
                # Enroll the user using the default mode (honor)
                # We're assuming that users of the course enrollment table
                # will NOT try to look up the course enrollment model
                # by its slug.  If they do, it's possible (based on the state of the database)
                # for no such model to exist, even though we've set the enrollment type
                # to "honor".
                try:
                    CourseEnrollment.enroll(user, course_id, check_access=check_access)
                except Exception:
                    return HttpResponseBadRequest(_("Could not enroll"))

            # If we have more than one course mode or professional ed is enabled,
            # then send the user to the choose your track page.
            # (In the case of professional ed, this will redirect to a page that
            # funnels users directly into the verification / payment flow)
            if len(available_modes) > 1 or "professional" in available_modes:
                return HttpResponse(
                    reverse("course_modes_choose", kwargs={'course_id': unicode(course_id)})
                )

            # Otherwise, there is only one mode available (the default)
            return HttpResponse()

        # If auto-registration is disabled, do NOT register the student
        # before sending them to the "choose your track" page.
        # This is the control for the auto-registration AB-test.
        else:
            # If this course is available in multiple modes, redirect them to a page
            # where they can choose which mode they want.
            available_modes = CourseMode.modes_for_course(course_id)
            if len(available_modes) > 1:
                return HttpResponse(
                    reverse("course_modes_choose", kwargs={'course_id': unicode(course_id)})
                )

            current_mode = available_modes[0]
            # only automatically enroll people if the only mode is 'honor'
            if current_mode.slug != 'honor':
                return HttpResponse(
                    reverse("course_modes_choose", kwargs={'course_id': unicode(course_id)})
                )

            try:
                CourseEnrollment.enroll(user, course_id, mode=current_mode.slug, check_access=check_access)
            except Exception:
                return HttpResponseBadRequest(_("Could not enroll"))

            return HttpResponse()

    elif action == "add_to_cart":
        # Pass the request handling to shoppingcart.views
        # The view in shoppingcart.views performs error handling and logs different errors.  But this elif clause
        # is only used in the "auto-add after user reg/login" case, i.e. it's always wrapped in try_change_enrollment.
        # This means there's no good way to display error messages to the user.  So we log the errors and send
        # the user to the shopping cart page always, where they can reasonably discern the status of their cart,
        # whether things got added, etc

        shoppingcart.views.add_course_to_cart(request, course_id.to_deprecated_string())
        return HttpResponse(
            reverse("shoppingcart.views.show_cart")
        )

    elif action == "unenroll":
        if not CourseEnrollment.is_enrolled(user, course_id):
            return HttpResponseBadRequest(_("You are not enrolled in this course"))
        CourseEnrollment.unenroll(user, course_id)
        return HttpResponse()
    else:
        return HttpResponseBadRequest(_("Enrollment action is invalid"))


# TODO: This function is kind of gnarly/hackish/etc and is only used in one location.
# It'd be awesome if we could get rid of it; manually parsing course_id strings form larger strings
# seems Probably Incorrect
def _parse_course_id_from_string(input_str):
    """
    Helper function to determine if input_str (typically the queryparam 'next') contains a course_id.
    @param input_str:
    @return: the course_id if found, None if not
    """
    m_obj = re.match(r'^/courses/{}'.format(settings.COURSE_ID_PATTERN), input_str)
    if m_obj:
        return SlashSeparatedCourseKey.from_deprecated_string(m_obj.group('course_id'))
    return None


def _get_course_enrollment_domain(course_id):
    """
    Helper function to get the enrollment domain set for a course with id course_id
    @param course_id:
    @return:
    """
    course = modulestore().get_course(course_id)
    if course is None:
        return None

    return course.enrollment_domain


@never_cache
@ensure_csrf_cookie
def accounts_login(request):
    """
    This view is mainly used as the redirect from the @login_required decorator.  I don't believe that
    the login path linked from the homepage uses it.
    """
    if settings.FEATURES.get('AUTH_USE_CAS'):
        return redirect(reverse('cas-login'))
    if settings.FEATURES['AUTH_USE_CERTIFICATES']:
        # SSL login doesn't require a view, so login
        # directly here
        return external_auth.views.ssl_login(request)
    # see if the "next" parameter has been set, whether it has a course context, and if so, whether
    # there is a course-specific place to redirect
    redirect_to = request.GET.get('next')
    if redirect_to:
        course_id = _parse_course_id_from_string(redirect_to)
        if course_id and _get_course_enrollment_domain(course_id):
            return external_auth.views.course_specific_login(request, course_id.to_deprecated_string())

    context = {
        'pipeline_running': 'false',
        'platform_name': settings.PLATFORM_NAME,
    }
    return render_to_response('login.html', context)


# Need different levels of logging
@ensure_csrf_cookie
def login_user(request, error=""):  # pylint: disable-msg=too-many-statements,unused-argument
    """AJAX request to log in the user."""

    backend_name = None
    email = None
    password = None
    redirect_url = None
    response = None
    running_pipeline = None
    third_party_auth_requested = microsite.get_value('ENABLE_THIRD_PARTY_AUTH', settings.FEATURES.get('ENABLE_THIRD_PARTY_AUTH')) and pipeline.running(request)
    third_party_auth_successful = False
    trumped_by_first_party_auth = bool(request.POST.get('email')) or bool(request.POST.get('password'))
    user = None

    if third_party_auth_requested and not trumped_by_first_party_auth:
        # The user has already authenticated via third-party auth and has not
        # asked to do first party auth by supplying a username or password. We
        # now want to put them through the same logging and cookie calculation
        # logic as with first-party auth.
        running_pipeline = pipeline.get(request)
        username = running_pipeline['kwargs'].get('username')
        backend_name = running_pipeline['backend']
        requested_provider = provider.Registry.get_by_backend_name(backend_name)

        try:
            user = pipeline.get_authenticated_user(username, backend_name)
            third_party_auth_successful = True
        except User.DoesNotExist:
            AUDIT_LOG.warning(
                u'Login failed - user with username {username} has no social auth with backend_name {backend_name}'.format(
                    username=username, backend_name=backend_name))
            return HttpResponseBadRequest(
                _("You've successfully logged into your {provider_name} account, but this account isn't linked with an {platform_name} account yet.").format(
                    platform_name=settings.PLATFORM_NAME, provider_name=requested_provider.NAME
                )
                + "<br/><br/>" +
                _("Use your {platform_name} username and password to log into {platform_name} below, "
                  "and then link your {platform_name} account with {provider_name} from your dashboard.").format(
                      platform_name=settings.PLATFORM_NAME, provider_name=requested_provider.NAME
                  )
                + "<br/><br/>" +
                _("If you don't have an {platform_name} account yet, click <strong>Register Now</strong> at the top of the page.").format(
                    platform_name=settings.PLATFORM_NAME
                ),
                content_type="text/plain",
                status=401
            )

    else:

        if 'email' not in request.POST or 'password' not in request.POST:
            return JsonResponse({
                "success": False,
                "value": _('There was an error receiving your login information. Please email us.'),  # TODO: User error message
            })  # TODO: this should be status code 400  # pylint: disable=fixme

        email = request.POST['email']
        password = request.POST['password']
        try:
            user = User.objects.get(email=email)
        except User.DoesNotExist:
            if settings.FEATURES['SQUELCH_PII_IN_LOGS']:
                AUDIT_LOG.warning(u"Login failed - Unknown user email")
            else:
                AUDIT_LOG.warning(u"Login failed - Unknown user email: {0}".format(email))

    # check if the user has a linked shibboleth account, if so, redirect the user to shib-login
    # This behavior is pretty much like what gmail does for shibboleth.  Try entering some @stanford.edu
    # address into the Gmail login.
    if settings.FEATURES.get('AUTH_USE_SHIB') and user:
        try:
            eamap = ExternalAuthMap.objects.get(user=user)
            if eamap.external_domain.startswith(external_auth.views.SHIBBOLETH_DOMAIN_PREFIX):
                return JsonResponse({
                    "success": False,
                    "redirect": reverse('shib-login'),
                })  # TODO: this should be status code 301  # pylint: disable=fixme
        except ExternalAuthMap.DoesNotExist:
            # This is actually the common case, logging in user without external linked login
            AUDIT_LOG.info("User %s w/o external auth attempting login", user)

    # see if account has been locked out due to excessive login failures
    user_found_by_email_lookup = user
    if user_found_by_email_lookup and LoginFailures.is_feature_enabled():
        if LoginFailures.is_user_locked_out(user_found_by_email_lookup):
            return JsonResponse({
                "success": False,
                "value": _('This account has been temporarily locked due to excessive login failures. Try again later.'),
            })  # TODO: this should be status code 429  # pylint: disable=fixme

    # see if the user must reset his/her password due to any policy settings
    if PasswordHistory.should_user_reset_password_now(user_found_by_email_lookup):
        return JsonResponse({
            "success": False,
            "value": _('Your password has expired due to password policy on this account. You must '
                       'reset your password before you can log in again. Please click the '
                       '"Forgot Password" link on this page to reset your password before logging in again.'),
        })  # TODO: this should be status code 403  # pylint: disable=fixme

    # if the user doesn't exist, we want to set the username to an invalid
    # username so that authentication is guaranteed to fail and we can take
    # advantage of the ratelimited backend
    username = user.username if user else ""

    if not third_party_auth_successful:
        try:
            user = authenticate(username=username, password=password, request=request)
        # this occurs when there are too many attempts from the same IP address
        except RateLimitException:
            return JsonResponse({
                "success": False,
                "value": _('Too many failed login attempts. Try again later.'),
            })  # TODO: this should be status code 429  # pylint: disable=fixme

    if user is None:
        # tick the failed login counters if the user exists in the database
        if user_found_by_email_lookup and LoginFailures.is_feature_enabled():
            LoginFailures.increment_lockout_counter(user_found_by_email_lookup)

        # if we didn't find this username earlier, the account for this email
        # doesn't exist, and doesn't have a corresponding password
        if username != "":
            if settings.FEATURES['SQUELCH_PII_IN_LOGS']:
                loggable_id = user_found_by_email_lookup.id if user_found_by_email_lookup else "<unknown>"
                AUDIT_LOG.warning(u"Login failed - password for user.id: {0} is invalid".format(loggable_id))
            else:
                AUDIT_LOG.warning(u"Login failed - password for {0} is invalid".format(email))
        return JsonResponse({
            "success": False,
            "value": _('Email or password is incorrect.'),
        })  # TODO: this should be status code 400  # pylint: disable=fixme

    # successful login, clear failed login attempts counters, if applicable
    if LoginFailures.is_feature_enabled():
        LoginFailures.clear_lockout_counter(user)

    # Track the user's sign in
    if settings.FEATURES.get('SEGMENT_IO_LMS') and hasattr(settings, 'SEGMENT_IO_LMS_KEY'):
        tracking_context = tracker.get_tracker().resolve_context()
        analytics.identify(user.id, {
            'email': email,
            'username': username,
        })

        # If the user entered the flow via a specific course page, we track that
        registration_course_id = request.session.get('registration_course_id')
        analytics.track(