baseimage-tutorial-framework/lib/tfw/networking/server/tfw_server.py

# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
# All Rights Reserved. See LICENSE file for details.

from collections import defaultdict

from tornado.web import Application

from tfw.networking import MessageSender
from tfw.networking.event_handlers import ServerUplinkConnector
from tfw.networking.server import EventHandlerConnector
from tfw.config.logs import logging
from .zmq_websocket_handler import ZMQWebSocketProxy

LOG = logging.getLogger(__name__)


class TFWServer:
    """
    This class handles the proxying of messages between the frontend and event handers.
    It proxies messages from the "/ws" route to all event handlers subscribed to a ZMQ
    SUB socket. It also manages an FSM you can define as a constructor argument.
    """
    def __init__(self, fsm_type):
        """
        :param fsm_type: the type of FSM you want TFW to use
        """
        self._fsm = fsm_type()
        self._fsm_updater = FSMUpdater(self._fsm)
        self._fsm_manager = FSMManager(self._fsm)
        self._fsm.subscribe_callback(self._fsm_updater.update)
        self._event_handler_connector = EventHandlerConnector()

        self.application = Application([(
            r'/ws', ZMQWebSocketProxy,{
                'make_eventhandler_message': self.make_eventhandler_message,
                'proxy_filter': self.proxy_filter,
                'handle_trigger': self.handle_trigger,
                'event_handler_connector': self._event_handler_connector
            })]
        )
        # self.controller_responder = ControllerResponder(self.fsm)
        # TODO: add this once controller stuff is resolved

    @property
    def fsm(self):
        return self._fsm

    @property
    def fsm_manager(self):
        return self._fsm_manager

    def make_eventhandler_message(self, message):
        self.trigger_fsm(message)
        message['FSMUpdate'] = self._fsm_updater.get_fsm_state_and_transitions()
        return message

    def handle_trigger(self, message):
        LOG.debug('Executing handler for trigger "%s"', message.get('trigger', ''))
        self.trigger_fsm(message)

    def trigger_fsm(self, message):
        trigger = message.get('trigger', '')
        try:
            self._fsm_manager.trigger(trigger, message)
        except AttributeError:
            LOG.debug('FSM failed to execute nonexistent trigger: "%s"', trigger)

    def proxy_filter(self, message):
        # pylint: disable=unused-argument,no-self-use
        return True

    def listen(self, port):
        self.application.listen(port)


class FSMManager:
    def __init__(self, fsm):
        self._fsm = fsm
        self.trigger_predicates = defaultdict(list)
        self.messenge_sender = MessageSender()

    @property
    def fsm(self):
        return self._fsm

    def trigger(self, trigger, message):
        predicate_results = []
        for predicate in self.trigger_predicates[trigger]:
            success, message = predicate(message)
            predicate_results.append(success)
            self.messenge_sender.send('FSM', message)

        if all(predicate_results):
            try:
                self.fsm.trigger(trigger, message=message)
            except AttributeError:
                LOG.debug('FSM failed to execute nonexistent trigger: "%s"', trigger)

    def subscribe_predicate(self, trigger, *predicates):
        self.trigger_predicates[trigger].extend(predicates)

    def unsubscribe_predicate(self, trigger, *predicates):
        self.trigger_predicates[trigger] = [
            predicate
            for predicate in self.trigger_predicates[trigger]
            not in predicates
        ]


class FSMUpdater:
    def __init__(self, fsm):
        self.fsm = fsm
        self.uplink = ServerUplinkConnector()

    def update(self, kwargs_dict):
        # pylint: disable=unused-argument
        self.uplink.send(self.generate_fsm_update())

    def generate_fsm_update(self):
        return {
            'key': 'FSMUpdate',
            'data': self.get_fsm_state_and_transitions()
        }

    def get_fsm_state_and_transitions(self):
        state = self.fsm.state
        valid_transitions = [
            {'trigger': trigger}
            for trigger in self.fsm.machine.get_triggers(self.fsm.state)
        ]
        return {
            'current_state': state,
            'valid_transitions': valid_transitions
        }