# -*- coding: utf-8 -*-

# copyright 2012 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr

#

# This file is part of CubicWeb.

#

# CubicWeb is free software: you can redistribute it and/or modify it under the

# terms of the GNU Lesser General Public License as published by the Free

# Software Foundation, either version 2.1 of the License, or (at your option)

# any later version.

#

# CubicWeb is distributed in the hope that it will be useful, but WITHOUT

# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more

# details.

#

# You should have received a copy of the GNU Lesser General Public License along

# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.

from threading import Thread

import cPickle

import traceback

import zmq

from zmq.eventloop import ioloop

import zmq.eventloop.zmqstream

from logging import getLogger

from cubicweb import set_log_methods

from cubicweb.server.server import QuitEvent

ctx = zmq.Context()

class ZMQComm(object):

    """

    A simple ZMQ-based notification bus.

    There should at most one instance of this class attached to a

    Repository. A typical usage may be something like::

        def callback(msg):

            self.info('received message: %s', ' '.join(msg))

        repo.app_instances_bus.subscribe('hello', callback)

    to subsribe to the 'hello' kind of message. On the other side, to

    emit a notification, call::

       repo.app_instances_bus.publish(['hello', 'world'])

    See http://docs.cubicweb.org for more details.

    """

    def __init__(self):

        self.ioloop = ioloop.IOLoop()

        self._topics = {}

        self._subscribers = []

        self.publisher = None

    def add_publisher(self, address):

        assert self.publisher is None, "more than one publisher is not supported"

        self.publisher = Publisher(self.ioloop, address)

    def add_subscription(self, topic, callback):

        for subscriber in self._subscribers:

            subscriber.subscribe(topic, callback)

        self._topics[topic] = callback

    def add_subscriber(self, address):

        subscriber = Subscriber(self.ioloop, address)

        for topic, callback in self._topics.iteritems():

            subscriber.subscribe(topic, callback)

        self._subscribers.append(subscriber)

    def publish(self, msg):

        assert self.publisher is not None, "can't publish without a publisher"

        self.publisher.send(msg)

    def start(self):

        Thread(target=self.ioloop.start).start()

    def stop(self):

        self.ioloop.add_callback(self.ioloop.stop)

    def __del__(self):

        self.ioloop.close()

class Publisher(object):

    def __init__(self, ioloop, address):

        self.address = address

        self._topics = {}

        self._subscribers = []

        self.ioloop = ioloop

        def callback():

            s = ctx.socket(zmq.PUB)

            self.stream = zmq.eventloop.zmqstream.ZMQStream(s, io_loop=ioloop)

            self.stream.bind(self.address)

            self.debug('start publisher on %s', self.address)

        ioloop.add_callback(callback)

    def send(self, msg):

        self.ioloop.add_callback(lambda:self.stream.send_multipart(msg))

class Subscriber(object):

    def __init__(self, ioloop, address):

        self.address = address

        self.dispatch_table = {}

        self.ioloop = ioloop

        def callback():

            s = ctx.socket(zmq.SUB)

            self.stream = zmq.eventloop.zmqstream.ZMQStream(s, io_loop=ioloop)

            self.stream.on_recv(self.dispatch)

            self.stream.connect(self.address)

            self.debug('start subscriber on %s', self.address)

        ioloop.add_callback(callback)

    def dispatch(self, msg):

        try:

            f = self.dispatch_table[msg[0]]

        except KeyError:

            return

        f(msg)

    def subscribe(self, topic, callback):

        self.dispatch_table[topic] = callback

        self.ioloop.add_callback(lambda: self.stream.setsockopt(zmq.SUBSCRIBE, topic))

class ZMQRepositoryServer(object):

    def __init__(self, repository):

        """make the repository available as a PyRO object"""

        self.address = None

        self.repo = repository

        self.socket = None

        self.stream = None

        self.loop = ioloop.IOLoop()

        # event queue

        self.events = []

    def connect(self, address):

        self.address = address

    def run(self):

        """enter the service loop"""

        # start repository looping tasks

        self.socket = ctx.socket(zmq.REP)

        self.stream = zmq.eventloop.zmqstream.ZMQStream(self.socket, io_loop=self.loop)

        self.stream.bind(self.address)

        self.info('ZMQ server bound on: %s', self.address)

        self.stream.on_recv(self.process_cmds)

        try:

            self.loop.start()

        except zmq.ZMQError:

            self.warning('ZMQ event loop killed')

        self.quit()

    def trigger_events(self):

        """trigger ready events"""

        for event in self.events[:]:

            if event.is_ready():

                self.info('starting event %s', event)

                event.fire(self)

                try:

                    event.update()

                except Finished:

                    self.events.remove(event)

    def process_cmd(self, cmd):

        """Delegate the given command to the repository.

        ``cmd`` is a list of (method_name, args, kwargs)

        where ``args`` is a list of positional arguments

        and ``kwargs`` is a dictionnary of named arguments.

        >>> rset = delegate_to_repo(["execute", [sessionid], {'rql': rql}])

        :note1: ``kwargs`` may be ommited

            >>> rset = delegate_to_repo(["execute", [sessionid, rql]])

        :note2: both ``args`` and ``kwargs`` may be omitted

            >>> schema = delegate_to_repo(["get_schema"])

            >>> schema = delegate_to_repo("get_schema") # also allowed

        """

        cmd = cPickle.loads(cmd)

        if not cmd:

            raise AttributeError('function name required')

        if isinstance(cmd, basestring):

            cmd = [cmd]

        if len(cmd) < 2:

            cmd.append(())

        if len(cmd) < 3:

            cmd.append({})

        cmd  = list(cmd) + [(), {}]

        funcname, args, kwargs = cmd[:3]

        result = getattr(self.repo, funcname)(*args, **kwargs)

        return result

    def process_cmds(self, cmds):

        """Callback intended to be used with ``on_recv``.

        Call ``delegate_to_repo`` on each command and send a pickled of

        each result recursively.

        Any exception are catched, pickled and sent.

        """

        try:

            for cmd in cmds:

                result = self.process_cmd(cmd)

                self.send_data(result)

        except Exception, exc:

            traceback.print_exc()

            self.send_data(exc)

    def send_data(self, data):

        self.socket.send_pyobj(data)

    def quit(self, shutdown_repo=False):

        """stop the server"""

        self.info('Quitting ZMQ server')

        try:

            self.loop.add_callback(self.loop.stop)

            self.stream.on_recv(None)

            self.stream.close()

        except Exception, e:

            print e

            pass

        if shutdown_repo and not self.repo.shutting_down:

            event = QuitEvent()

            event.fire(self)

    # server utilitities ######################################################

    def install_sig_handlers(self):

        """install signal handlers"""

        import signal

        self.info('installing signal handlers')

        signal.signal(signal.SIGINT, lambda x, y, s=self: s.quit(shutdown_repo=True))

        signal.signal(signal.SIGTERM, lambda x, y, s=self: s.quit(shutdown_repo=True))

    # these are overridden by set_log_methods below

    # only defining here to prevent pylint from complaining

    @classmethod

    def info(cls, msg, *a, **kw):

        pass

set_log_methods(Publisher, getLogger('cubicweb.zmq.pub'))

set_log_methods(Subscriber, getLogger('cubicweb.zmq.sub'))

set_log_methods(ZMQRepositoryServer, getLogger('cubicweb.zmq.repo'))