# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
#
#    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.

"""
WSGI middleware for OpenStack API controllers.
"""

import routes
import webob.dec
import webob.exc

from nova.api.openstack import wsgi
from nova import notifications
from nova.openstack.common import log as logging
from nova import utils
from nova import wsgi as base_wsgi


LOG = logging.getLogger(__name__)


class FaultWrapper(base_wsgi.Middleware):
    """Calls down the middleware stack, making exceptions into faults."""

    _status_to_type = {}

    @staticmethod
    def status_to_type(status):
        if not FaultWrapper._status_to_type:
            for clazz in utils.walk_class_hierarchy(webob.exc.HTTPError):
                FaultWrapper._status_to_type[clazz.code] = clazz
        return FaultWrapper._status_to_type.get(
                                  status, webob.exc.HTTPInternalServerError)()

    def _error(self, inner, req):
        LOG.exception(_("Caught error: %s"), unicode(inner))

        safe = getattr(inner, 'safe', False)
        headers = getattr(inner, 'headers', None)
        status = getattr(inner, 'code', 500)
        if status is None:
            status = 500

        msg_dict = dict(url=req.url, status=status)
        LOG.info(_("%(url)s returned with HTTP %(status)d") % msg_dict)
        outer = self.status_to_type(status)
        if headers:
            outer.headers = headers
        # NOTE(johannes): We leave the explanation empty here on
        # purpose. It could possibly have sensitive information
        # that should not be returned back to the user. See
        # bugs 868360 and 874472
        # NOTE(eglynn): However, it would be over-conservative and
        # inconsistent with the EC2 API to hide every exception,
        # including those that are safe to expose, see bug 1021373
        if safe:
            outer.explanation = '%s: %s' % (inner.__class__.__name__,
                                            unicode(inner))

        notifications.send_api_fault(req.url, status, inner)
        return wsgi.Fault(outer)

    @webob.dec.wsgify(RequestClass=wsgi.Request)
    def __call__(self, req):
        try:
            return req.get_response(self.application)
        except Exception as ex:
            return self._error(ex, req)


class APIMapper(routes.Mapper):
    def routematch(self, url=None, environ=None):
        if url == "":
            result = self._match("", environ)
            return result[0], result[1]
        return routes.Mapper.routematch(self, url, environ)

    def connect(self, *args, **kargs):
        # NOTE(vish): Default the format part of a route to only accept json
        #             and xml so it doesn't eat all characters after a '.'
        #             in the url.
        kargs.setdefault('requirements', {})
        if not kargs['requirements'].get('format'):
            kargs['requirements']['format'] = 'json|xml'
        return routes.Mapper.connect(self, *args, **kargs)


class ProjectMapper(APIMapper):
    def resource(self, member_name, collection_name, **kwargs):
        if not ('parent_resource' in kwargs):
            kwargs['path_prefix'] = '{project_id}/'
        else:
            parent_resource = kwargs['parent_resource']
            p_collection = parent_resource['collection_name']
            p_member = parent_resource['member_name']
            kwargs['path_prefix'] = '{project_id}/%s/:%s_id' % (p_collection,
                                                                p_member)
        routes.Mapper.resource(self, member_name,
                                     collection_name,
                                     **kwargs)


class APIRouter(base_wsgi.Router):
    """
    Routes requests on the OpenStack API to the appropriate controller
    and method.
    """
    ExtensionManager = None  # override in subclasses

    @classmethod
    def factory(cls, global_config, **local_config):
        """Simple paste factory, :class:`nova.wsgi.Router` doesn't have one"""
        return cls()

    def __init__(self, ext_mgr=None, init_only=None):
        if ext_mgr is None:
            if self.ExtensionManager:
                ext_mgr = self.ExtensionManager()
            else:
                raise Exception(_("Must specify an ExtensionManager class"))

        mapper = ProjectMapper()
        self.resources = {}
        self._setup_routes(mapper, ext_mgr, init_only)
        self._setup_ext_routes(mapper, ext_mgr, init_only)
        self._setup_extensions(ext_mgr)
        super(APIRouter, self).__init__(mapper)

    def _setup_ext_routes(self, mapper, ext_mgr, init_only):
        for resource in ext_mgr.get_resources():
            LOG.debug(_('Extended resource: %s'),
                      resource.collection)

            if init_only is not None and resource.collection not in init_only:
                continue

            inherits = None
            if resource.inherits:
                inherits = self.resources.get(resource.inherits)
                if not resource.controller:
                    resource.controller = inherits.controller
            wsgi_resource = wsgi.Resource(resource.controller,
                                          inherits=inherits)
            self.resources[resource.collection] = wsgi_resource
            kargs = dict(
                controller=wsgi_resource,
                collection=resource.collection_actions,
                member=resource.member_actions)

            if resource.parent:
                kargs['parent_resource'] = resource.parent

            mapper.resource(resource.collection, resource.collection, **kargs)

            if resource.custom_routes_fn:
                resource.custom_routes_fn(mapper, wsgi_resource)

    def _setup_extensions(self, ext_mgr):
        for extension in ext_mgr.get_controller_extensions():
            ext_name = extension.extension.name
            collection = extension.collection
            controller = extension.controller

            if collection not in self.resources:
                LOG.warning(_('Extension %(ext_name)s: Cannot extend '
                              'resource %(collection)s: No such resource') %
                            locals())
                continue

            LOG.debug(_('Extension %(ext_name)s extending resource: '
                        '%(collection)s') % locals())

            resource = self.resources[collection]
            resource.register_actions(controller)
            resource.register_extensions(controller)

    def _setup_routes(self, mapper, ext_mgr, init_only):
        raise NotImplementedError()
