# 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

import django
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 import shortcuts
from django.utils import functional
from django.utils import http
from django.views.decorators.cache import never_cache  # noqa
from django.views.decorators.csrf import csrf_protect  # noqa
from django.views.decorators.debug import sensitive_post_parameters  # noqa
from keystoneclient import exceptions as keystone_exceptions
from keystoneclient.v2_0 import client as keystone_client_v2

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 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":
        # NOTE(saschpe): Since https://code.djangoproject.com/ticket/15198,
        # the 'request' object is passed directly to AuthenticationForm in
        # django.contrib.auth.views#login:
        if django.VERSION >= (1, 6):
            form = functional.curry(forms.Login)
        else:
            form = functional.curry(forms.Login, request)
    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)
    # 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


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')
    token = request.session.get('token')
    if token and endpoint:
        delete_token(endpoint=endpoint, token_id=token.id)
    """ 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."""

    insecure = getattr(settings, 'OPENSTACK_SSL_NO_VERIFY', False)
    ca_cert = getattr(settings, "OPENSTACK_SSL_CACERT", None)
    utils.remove_project_cache(token_id)
    try:
        if utils.get_keystone_version() < 3:
            client = keystone_client_v2.Client(
                endpoint=endpoint,
                token=token_id,
                insecure=insecure,
                cacert=ca_cert,
                debug=settings.DEBUG
            )
            client.tokens.delete(token=token_id)
            LOG.info('Deleted token %s' % token_id)
        else:
            # FIXME: KS-client does not have delete token available
            # Need to add this later when it is exposed.
            pass
    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))
    insecure = getattr(settings, 'OPENSTACK_SSL_NO_VERIFY', False)
    ca_cert = getattr(settings, "OPENSTACK_SSL_CACERT", None)
    endpoint = request.user.endpoint
    try:
        if utils.get_keystone_version() >= 3:
            if not utils.has_in_url_path(endpoint, '/v3'):
                endpoint = utils.url_path_replace(endpoint, '/v2.0', '/v3', 1)
        client = utils.get_keystone_client().Client(
            tenant_id=tenant_id,
            token=request.user.token.id,
            auth_url=endpoint,
            insecure=insecure,
            cacert=ca_cert,
            debug=settings.DEBUG)
        auth_ref = client.auth_ref
        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}
        LOG.warning(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.REQUEST.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), endpoint)
        auth_user.set_session_from_user(request, user)
    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.REQUEST.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