ncclient:NETCONF Python client

# Copyright 2009 Shikhar Bhushan

#

# 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.

from threading import Event, Lock

from uuid import uuid1

from weakref import WeakValueDictionary

from ncclient.content import TreeBuilder

from ncclient.content import qualify as _

from ncclient.content import unqualify as __

from ncclient.glue import Listener

from . import logger

from reply import RPCReply

# Cisco does not include message-id attribute in <rpc-reply> in case of an error.

# This is messed up however we have to deal with it.

# So essentially, there can be only one operation at a time if we are talking to

# a Cisco device.

def cisco_check(session):

    try:

        return session.is_remote_cisco

    except AttributeError:

        return False

class RPC(object):

    def __init__(self, session, async=False):

        if cisco_check(session) and async:

            raise UserWarning('Asynchronous mode not supported for Cisco devices')

        self._session = session

        self._async = async

        self._id = uuid1().urn

        self._listener = RPCReplyListener(session)

        self._listener.register(self._id, self)

        self._reply = None

        self._reply_event = Event()

    def _build(self, op, encoding='utf-8'):

        if isinstance(op, dict):

            return self.build_from_spec(self._id, op, encoding)

        else:

            return self.build_from_string(self._id, op, encoding)

    def _request(self, op):

        req = self._build(op)

        self._session.send(req)

        if self._async:

            return self._reply_event

        else:

            self._reply_event.wait()

            self._reply.parse()

            return self._reply

    def _delivery_hook(self):

        'For subclasses'

        pass

    def deliver(self, raw):

        self._reply = RPCReply(raw)

        self._delivery_hook()

        self._reply_event.set()

    @property

    def has_reply(self):

        return self._reply_event.isSet()

    @property

    def reply(self):

        return self._reply

    @property

    def is_async(self):

        return self._async

    @property

    def id(self):

        return self._id

    @property

    def session(self):

        return self._session

    @property

    def reply_event(self):

        return self._reply_event

    @staticmethod

    def build_from_spec(msgid, opspec, encoding='utf-8'):

        "TODO: docstring"

        spec = {

            'tag': _('rpc'),

            'attributes': {'message-id': msgid},

            'children': opspec

            }

        return TreeBuilder(spec).to_string(encoding)

    @staticmethod

    def build_from_string(msgid, opstr, encoding='utf-8'):

        "TODO: docstring"

        decl = '<?xml version="1.0" encoding="%s"?>' % encoding

        doc = (u'<rpc message-id="%s" xmlns="%s">%s</rpc>' %

               (msgid, BASE_NS, opstr)).encode(encoding)

        return '%s%s' % (decl, doc)

class RPCReplyListener(Listener):

    # TODO - determine if need locking

    # one instance per session

    def __new__(cls, session):

        instance = session.get_listener_instance(cls)

        if instance is None:

            instance = object.__new__(cls)

            instance._id2rpc = WeakValueDictionary()

            instance._cisco = cisco_check(session)

            instance._errback = None

            session.add_listener(instance)

        return instance

    def __str__(self):

        return 'RPCReplyListener'

    def set_errback(self, errback):

        self._errback = errback

    def register(self, id, rpc):

        self._id2rpc[id] = rpc

    def callback(self, root, raw):

        tag, attrs = root

        if __(tag) != 'rpc-reply':

            return

        rpc = None

        for key in attrs:

            if __(key) == 'message-id':

                id = attrs[key]

                try:

                    rpc = self._id2rpc.pop(id)

                except KeyError:

                    logger.warning('[RPCReplyListener.callback] no object '

                                   + 'registered for message-id: [%s]' % id)

                except Exception as e:

                    logger.debug('[RPCReplyListener.callback] error - %r' % e)

                break

        else:

            if self._cisco:

                assert(len(self._id2rpc) == 1)

                rpc = self._id2rpc.values()[0]

                self._id2rpc.clear()

            else:

                logger.warning('<rpc-reply> without message-id received: %s' % raw)

        logger.debug('[RPCReplyListener.callback] delivering to %r' % rpc)

        rpc.deliver(raw)

    def errback(self, err):

        if self._errback is not None:

            self._errback(err)