# 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.
"""

from oslo.config import cfg
import routes
import stevedore
import webob.dec
import webob.exc

from nova.api.openstack import extensions
from nova.api.openstack import wsgi
from nova import exception
from nova import notifications
from nova.openstack.common import gettextutils
from nova.openstack.common.gettextutils import _
from nova.openstack.common import log as logging
from nova import utils
from nova import wsgi as base_wsgi


api_opts = [
        cfg.BoolOpt('enabled',
                    default=False,
                    help='Whether the V3 API is enabled or not'),
        cfg.ListOpt('extensions_blacklist',
                    default=[],
                    help='A list of v3 API extensions to never load. '
                    'Specify the extension aliases here.'),
        cfg.ListOpt('extensions_whitelist',
                    default=[],
                    help='If the list is not empty then a v3 API extension '
                    'will only be loaded if it exists in this list. Specify '
                    'the extension aliases here.')
]
api_opts_group = cfg.OptGroup(name='osapi_v3', title='API v3 Options')

LOG = logging.getLogger(__name__)
CONF = cfg.CONF
CONF.register_group(api_opts_group)
CONF.register_opts(api_opts, api_opts_group)

# List of v3 API extensions which are considered to form
# the core API and so must be present
# TODO(cyeoh): Expand this list as the core APIs are ported to V3
API_V3_CORE_EXTENSIONS = set(['consoles', 'extensions', 'flavors', 'ips',
                              'limits', 'servers', 'server-metadata',
                              'keypairs', 'console-output', 'versions'])


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:
            if isinstance(inner.msg_fmt, gettextutils.Message):
                user_locale = req.best_match_language()
                inner_msg = gettextutils.get_localized_message(
                        inner.msg_fmt, user_locale)
            else:
                inner_msg = unicode(inner)
            outer.explanation = '%s: %s' % (inner.__class__.__name__,
                                            inner_msg)

        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 'parent_resource' not 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 PlainMapper(APIMapper):
    def resource(self, member_name, collection_name, **kwargs):
        if 'parent_resource' in kwargs:
            parent_resource = kwargs['parent_resource']
            p_collection = parent_resource['collection_name']
            p_member = parent_resource['member_name']
            kwargs['path_prefix'] = '%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():
            collection = extension.collection
            controller = extension.controller

            msg_format_dict = {'collection': collection,
                               'ext_name': extension.extension.name}
            if collection not in self.resources:
                LOG.warning(_('Extension %(ext_name)s: Cannot extend '
                              'resource %(collection)s: No such resource'),
                            msg_format_dict)
                continue

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

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

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


class APIRouterV3(base_wsgi.Router):
    """
    Routes requests on the OpenStack v3 API to the appropriate controller
    and method.
    """

    API_EXTENSION_NAMESPACE = 'nova.api.v3.extensions'

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

    def __init__(self, init_only=None):
        # TODO(cyeoh): bp v3-api-extension-framework. Currently load
        # all extensions but eventually should be able to exclude
        # based on a config file
        def _check_load_extension(ext):
            if (self.init_only is None or ext.obj.alias in
                self.init_only) and isinstance(ext.obj,
                                               extensions.V3APIExtensionBase):

                # Check whitelist is either empty or if not then the extension
                # is in the whitelist
                if (not CONF.osapi_v3.extensions_whitelist or
                        ext.obj.alias in CONF.osapi_v3.extensions_whitelist):

                    # Check the extension is not in the blacklist
                    if ext.obj.alias not in CONF.osapi_v3.extensions_blacklist:
                        return self._register_extension(ext)
                    else:
                        LOG.warning(_("Not loading %s because it is "
                                      "in the blacklist"), ext.obj.alias)
                        return False
                else:
                    LOG.warning(
                        _("Not loading %s because it is not in the whitelist"),
                        ext.obj.alias)
                    return False
            else:
                return False

        if not CONF.osapi_v3.enabled:
            LOG.info("V3 API has been disabled by configuration")
            return

        self.init_only = init_only
        LOG.debug(_("v3 API Extension Blacklist: %s"),
                  CONF.osapi_v3.extensions_blacklist)
        LOG.debug(_("v3 API Extension Whitelist: %s"),
                  CONF.osapi_v3.extensions_whitelist)

        in_blacklist_and_whitelist = set(
            CONF.osapi_v3.extensions_whitelist).intersection(
                CONF.osapi_v3.extensions_blacklist)
        if len(in_blacklist_and_whitelist) != 0:
            LOG.warning(_("Extensions in both blacklist and whitelist: %s"),
                        list(in_blacklist_and_whitelist))

        self.api_extension_manager = stevedore.enabled.EnabledExtensionManager(
            namespace=self.API_EXTENSION_NAMESPACE,
            check_func=_check_load_extension,
            invoke_on_load=True,
            invoke_kwds={"extension_info": self.loaded_extension_info})

        mapper = PlainMapper()
        self.resources = {}

        # NOTE(cyeoh) Core API support is rewritten as extensions
        # but conceptually still have core
        if list(self.api_extension_manager):
            # NOTE(cyeoh): Stevedore raises an exception if there are
            # no plugins detected. I wonder if this is a bug.
            self.api_extension_manager.map(self._register_resources,
                                           mapper=mapper)
            self.api_extension_manager.map(self._register_controllers)

        missing_core_extensions = self.get_missing_core_extensions(
            self.loaded_extension_info.get_extensions().keys())
        if not self.init_only and missing_core_extensions:
            LOG.critical(_("Missing core API extensions: %s"),
                         missing_core_extensions)
            raise exception.CoreAPIMissing(
                missing_apis=missing_core_extensions)

        super(APIRouterV3, self).__init__(mapper)

    @staticmethod
    def get_missing_core_extensions(extensions_loaded):
        extensions_loaded = set(extensions_loaded)
        missing_extensions = API_V3_CORE_EXTENSIONS - extensions_loaded
        return missing_extensions

    @property
    def loaded_extension_info(self):
        raise NotImplementedError()

    def _register_extension(self, ext):
        raise NotImplementedError()

    def _register_resources(self, ext, mapper):
        """Register resources defined by the extensions

        Extensions define what resources they want to add through a
        get_resources function
        """

        handler = ext.obj
        LOG.debug(_("Running _register_resources on %s"), ext.obj)

        for resource in handler.get_resources():
            LOG.debug(_('Extended resource: %s'), resource.collection)

            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

            # non core-API plugins use the collection name as the
            # member name, but the core-API plugins use the
            # singular/plural convention for member/collection names
            if resource.member_name:
                member_name = resource.member_name
            else:
                member_name = resource.collection
            mapper.resource(member_name, resource.collection,
                            **kargs)

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

    def _register_controllers(self, ext):
        """Register controllers defined by the extensions

        Extensions define what resources they want to add through
        a get_controller_extensions function
        """

        handler = ext.obj
        LOG.debug(_("Running _register_controllers on %s"), ext.obj)

        for extension in handler.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'),
                              {'ext_name': ext_name, 'collection': collection})
                continue

            LOG.debug(_('Extension %(ext_name)s extending resource: '
                      '%(collection)s'),
                      {'ext_name': ext_name, 'collection': collection})

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