baseimage-tutorial-framework/tfw/components/fsm/fsm_handler.py

import logging

from tfw.internals.crypto import KeyManager, sign_message
from tfw.internals.networking import Scope

from .fsm_updater import FSMUpdater

LOG = logging.getLogger(__name__)


class FSMHandler:
    keys = ['fsm']

    def __init__(self, *, fsm_type, initial_trigger):
        self.fsm = fsm_type()
        self._fsm_updater = FSMUpdater(self.fsm)
        self.auth_key = KeyManager().auth_key
        self.initial_trigger = initial_trigger

        self.command_handlers = {
            'frontend.ready': self.handle_ready,
            'fsm.step'   : self.handle_step,
            'fsm.announce' : self.handle_announce
        }

    def start(self):
        self.connector.subscribe('frontend.ready')

    def handle_event(self, message, connector):
        try:
            message = self.command_handlers[message['key']](message)
            if message:
                fsm_update_message = self._fsm_updater.fsm_update
                sign_message(self.auth_key, fsm_update_message)
                connector.send_message(fsm_update_message, Scope.BROADCAST)
        except KeyError:
            LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)

    def handle_ready(self, message):
        self.fsm.step(self.initial_trigger)
        self.connector.unsubscribe('frontend.ready')
        return message

    def handle_step(self, message):
        if self.fsm.step(message['trigger']):
            return message

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