baseimage-tutorial-framework/lib/tfw/components/fsm_managing_event_handler.py

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

from tfw import EventHandlerBase
from tfw.crypto import KeyManager, sign_message, verify_message
from tfw.config.logs import logging

LOG = logging.getLogger(__name__)


class FSMManagingEventHandler(EventHandlerBase):
    def __init__(self, key, fsm_type, require_signature=False):
        super().__init__(key)
        self.fsm = fsm_type()
        self._fsm_updater = FSMUpdater(self.fsm)
        self.auth_key = KeyManager().auth_key
        self._require_signature = require_signature

        self.command_handlers = {
            'trigger': self.handle_trigger,
            'update':  self.handle_update
        }

    def handle_event(self, message):
        try:
            message = self.command_handlers[message['data']['command']](message)
            if message:
                fsm_update_message = self._fsm_updater.generate_fsm_update()
                sign_message(self.auth_key, message)
                sign_message(self.auth_key, fsm_update_message)
                self.server_connector.broadcast(fsm_update_message)
            return message
        except KeyError:
            LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)

    def handle_trigger(self, message):
        trigger = message['data']['value']
        if self._require_signature:
            if not verify_message(self.auth_key, message):
                LOG.error('Ignoring unsigned trigger command: %s', message)
                return None
        if self.fsm.step(trigger):
            return message
        return None

    def handle_update(self, message):
        # pylint: disable=no-self-use
        return message


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

    def generate_fsm_update(self):
        return {
            'key': 'fsm_update',
            '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.get_triggers(self.fsm.state)
        ]
        last_trigger = self.fsm.trigger_history[-1] if self.fsm.trigger_history else None
        in_accepted_state = state in self.fsm.accepted_states
        return {
            'current_state': state,
            'valid_transitions': valid_transitions,
            'last_trigger': last_trigger,
            'in_accepted_state': in_accepted_state
        }