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

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# 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
}