# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging

from django.conf import settings
from django.contrib import auth
from django.contrib.auth.decorators import login_required  # noqa
from django.contrib.auth import views as django_auth_views
from django.contrib import messages
from django import http as django_http
from django import shortcuts
from django.utils import functional
from django.utils import http
from django.utils.translation import ugettext_lazy as _
from django.views.decorators.cache import never_cache  # noqa
from django.views.decorators.csrf import csrf_exempt  # noqa
from django.views.decorators.csrf import csrf_protect  # noqa
from django.views.decorators.debug import sensitive_post_parameters  # noqa
from keystoneauth1 import exceptions as keystone_exceptions
from keystoneauth1 import token_endpoint
import six

from openstack_auth import exceptions
from openstack_auth import forms
# This is historic and is added back in to not break older versions of
# Horizon, fix to Horizon to remove this requirement was committed in
# Juno
from openstack_auth.forms import Login  # noqa
from openstack_auth import user as auth_user
from openstack_auth import utils

try:
    is_safe_url = http.is_safe_url
except AttributeError:
    is_safe_url = utils.is_safe_url


LOG = logging.getLogger(__name__)


@sensitive_post_parameters()
@csrf_protect
@never_cache
def login(request, template_name=None, extra_context=None, **kwargs):
    """Logs a user in using the :class:`~openstack_auth.forms.Login` form."""

    # If the user enabled websso and selects default protocol
    # from the dropdown, We need to redirect user to the websso url
    if request.method == 'POST':
        auth_type = request.POST.get('auth_type', 'credentials')
        if utils.is_websso_enabled() and auth_type != 'credentials':
            auth_url = request.POST.get('region')
            url = utils.get_websso_url(request, auth_url, auth_type)
            return shortcuts.redirect(url)

    if not request.is_ajax():
        # If the user is already authenticated, redirect them to the
        # dashboard straight away, unless the 'next' parameter is set as it
        # usually indicates requesting access to a page that requires different
        # permissions.
        if (request.user.is_authenticated() and
                auth.REDIRECT_FIELD_NAME not in request.GET and
                auth.REDIRECT_FIELD_NAME not in request.POST):
            return shortcuts.redirect(settings.LOGIN_REDIRECT_URL)

    # Get our initial region for the form.
    initial = {}
    current_region = request.session.get('region_endpoint', None)
    requested_region = request.GET.get('region', None)
    regions = dict(getattr(settings, "AVAILABLE_REGIONS", []))
    if requested_region in regions and requested_region != current_region:
        initial.update({'region': requested_region})

    if request.method == "POST":
        form = functional.curry(forms.Login)
    else:
        form = functional.curry(forms.Login, initial=initial)

    if extra_context is None:
        extra_context = {'redirect_field_name': auth.REDIRECT_FIELD_NAME}

    if not template_name:
        if request.is_ajax():
            template_name = 'auth/_login.html'
            extra_context['hide'] = True
        else:
            template_name = 'auth/login.html'

    res = django_auth_views.login(request,
                                  template_name=template_name,
                                  authentication_form=form,
                                  extra_context=extra_context,
                                  **kwargs)
    # Save the region in the cookie, this is used as the default
    # selected region next time the Login form loads.
    if request.method == "POST":
        utils.set_response_cookie(res, 'login_region',
                                  request.POST.get('region', ''))
        utils.set_response_cookie(res, 'login_domain',
                                  request.POST.get('domain', ''))

    # Set the session data here because django's session key rotation
    # will erase it if we set it earlier.
    if request.user.is_authenticated():
        auth_user.set_session_from_user(request, request.user)
        regions = dict(forms.Login.get_region_choices())
        region = request.user.endpoint
        region_name = regions.get(region)
        request.session['region_endpoint'] = region
        request.session['region_name'] = region_name
    return res


@sensitive_post_parameters()
@csrf_exempt
@never_cache
def websso(request):
    """Logs a user in using a token from Keystone's POST."""
    referer = request.META.get('HTTP_REFERER', settings.OPENSTACK_KEYSTONE_URL)
    auth_url = utils.clean_up_auth_url(referer)
    token = request.POST.get('token')
    try:
        request.user = auth.authenticate(request=request, auth_url=auth_url,
                                         token=token)
    except exceptions.KeystoneAuthException as exc:
        msg = 'Login failed: %s' % six.text_type(exc)
        res = django_http.HttpResponseRedirect(settings.LOGIN_URL)
        res.set_cookie('logout_reason', msg, max_age=10)
        return res

    auth_user.set_session_from_user(request, request.user)
    auth.login(request, request.user)
    if request.session.test_cookie_worked():
        request.session.delete_test_cookie()
    return django_http.HttpResponseRedirect(settings.LOGIN_REDIRECT_URL)


def logout(request, login_url=None, **kwargs):
    """Logs out the user if he is logged in. Then redirects to the log-in page.

    :param login_url:
        Once logged out, defines the URL where to redirect after login

    :param kwargs:
        see django.contrib.auth.views.logout_then_login extra parameters.

    """
    msg = 'Logging out user "%(username)s".' % \
        {'username': request.user.username}
    LOG.info(msg)
    endpoint = request.session.get('region_endpoint')

    # delete the project scoped token
    token = request.session.get('token')
    if token and endpoint:
        delete_token(endpoint=endpoint, token_id=token.id)

    # delete the domain scoped token if set
    domain_token = request.session.get('domain_token')
    if domain_token and endpoint:
        delete_token(endpoint=endpoint, token_id=domain_token.auth_token)

    """ Securely logs a user out. """
    return django_auth_views.logout_then_login(request, login_url=login_url,
                                               **kwargs)


def delete_token(endpoint, token_id):
    """Delete a token."""
    try:
        endpoint = utils.fix_auth_url_version(endpoint)

        session = utils.get_session()
        auth_plugin = token_endpoint.Token(endpoint=endpoint,
                                           token=token_id)
        client = utils.get_keystone_client().Client(session=session,
                                                    auth=auth_plugin)
        if utils.get_keystone_version() >= 3:
            client.tokens.revoke_token(token=token_id)
        else:
            client.tokens.delete(token=token_id)

        LOG.info('Deleted token %s' % token_id)
    except keystone_exceptions.ClientException:
        LOG.info('Could not delete token')


@login_required
def switch(request, tenant_id, redirect_field_name=auth.REDIRECT_FIELD_NAME):
    """Switches an authenticated user from one project to another."""
    LOG.debug('Switching to tenant %s for user "%s".'
              % (tenant_id, request.user.username))

    endpoint = utils.fix_auth_url_version(request.user.endpoint)
    session = utils.get_session()
    # Keystone can be configured to prevent exchanging a scoped token for
    # another token. Always use the unscoped token for requesting a
    # scoped token.
    unscoped_token = request.user.unscoped_token
    auth = utils.get_token_auth_plugin(auth_url=endpoint,
                                       token=unscoped_token,
                                       project_id=tenant_id)

    try:
        auth_ref = auth.get_access(session)
        msg = 'Project switch successful for user "%(username)s".' % \
            {'username': request.user.username}
        LOG.info(msg)
    except keystone_exceptions.ClientException:
        msg = (
            _('Project switch failed for user "%(username)s".') %
            {'username': request.user.username})
        messages.error(request, msg)
        auth_ref = None
        LOG.exception('An error occurred while switching sessions.')

    # Ensure the user-originating redirection url is safe.
    # Taken from django.contrib.auth.views.login()
    redirect_to = request.GET.get(redirect_field_name, '')
    if not is_safe_url(url=redirect_to, host=request.get_host()):
        redirect_to = settings.LOGIN_REDIRECT_URL

    if auth_ref:
        old_endpoint = request.session.get('region_endpoint')
        old_token = request.session.get('token')
        if old_token and old_endpoint and old_token.id != auth_ref.auth_token:
            delete_token(endpoint=old_endpoint, token_id=old_token.id)
        user = auth_user.create_user_from_token(
            request,
            auth_user.Token(auth_ref, unscoped_token=unscoped_token),
            endpoint)
        auth_user.set_session_from_user(request, user)
        message = (
            _('Switch to project "%(project_name)s" successful.') %
            {'project_name': request.user.project_name})
        messages.success(request, message)
    response = shortcuts.redirect(redirect_to)
    utils.set_response_cookie(response, 'recent_project',
                              request.user.project_id)
    return response


@login_required
def switch_region(request, region_name,
                  redirect_field_name=auth.REDIRECT_FIELD_NAME):
    """Switches the user's region for all services except Identity service.

    The region will be switched if the given region is one of the regions
    available for the scoped project. Otherwise the region is not switched.
    """
    if region_name in request.user.available_services_regions:
        request.session['services_region'] = region_name
        LOG.debug('Switching services region to %s for user "%s".'
                  % (region_name, request.user.username))

    redirect_to = request.GET.get(redirect_field_name, '')
    if not is_safe_url(url=redirect_to, host=request.get_host()):
        redirect_to = settings.LOGIN_REDIRECT_URL

    response = shortcuts.redirect(redirect_to)
    utils.set_response_cookie(response, 'services_region',
                              request.session['services_region'])
    return response