mirror of
https://github.com/avatao-content/baseimage-tutorial-framework
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101 lines
3.3 KiB
Python
101 lines
3.3 KiB
Python
# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
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# All Rights Reserved. See LICENSE file for details.
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import logging
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from tfw.event_handlers import FrontendEventHandlerBase
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from tfw.crypto import KeyManager, sign_message, verify_message
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from tfw.networking import Scope
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LOG = logging.getLogger(__name__)
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class FSMManagingEventHandler(FrontendEventHandlerBase):
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"""
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EventHandler responsible for managing the state machine of
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the framework (TFW FSM).
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tfw.networking.TFWServer instances automatically send 'trigger'
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commands to the event handler listening on the 'fsm' key,
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which should be an instance of this event handler.
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This event handler accepts messages that have a
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data['command'] key specifying a command to be executed.
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An 'fsm_update' message is broadcasted after every successful
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command.
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"""
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def __init__(self, key, fsm_type, require_signature=False):
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super().__init__(key)
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self.fsm = fsm_type()
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self._fsm_updater = FSMUpdater(self.fsm)
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self.auth_key = KeyManager().auth_key
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self._require_signature = require_signature
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self.command_handlers = {
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'trigger': self.handle_trigger,
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'update': self.handle_update
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}
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def handle_event(self, message):
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try:
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message = self.command_handlers[message['data']['command']](message)
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if message:
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fsm_update_message = self._fsm_updater.fsm_update
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sign_message(self.auth_key, message)
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sign_message(self.auth_key, fsm_update_message)
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self.server_connector.send_message(fsm_update_message, Scope.BROADCAST)
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return message
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except KeyError:
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LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)
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def handle_trigger(self, message):
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"""
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Attempts to step the FSM with the supplied trigger.
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:param message: TFW message with a data field containing
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the action to try triggering in data['value']
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"""
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trigger = message['data']['value']
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if self._require_signature:
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if not verify_message(self.auth_key, message):
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LOG.error('Ignoring unsigned trigger command: %s', message)
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return None
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if self.fsm.step(trigger):
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return message
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return None
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def handle_update(self, message):
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"""
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Does nothing, but triggers an 'fsm_update' message.
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"""
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# pylint: disable=no-self-use
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return message
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class FSMUpdater:
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def __init__(self, fsm):
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self.fsm = fsm
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@property
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def fsm_update(self):
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return {
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'key': 'fsm_update',
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'data': self.fsm_update_data
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}
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@property
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def fsm_update_data(self):
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valid_transitions = [
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{'trigger': trigger}
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for trigger in self.fsm.get_triggers(self.fsm.state)
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]
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last_fsm_event = self.fsm.event_log[-1]
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last_fsm_event['timestamp'] = last_fsm_event['timestamp'].isoformat()
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return {
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'current_state': self.fsm.state,
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'valid_transitions': valid_transitions,
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'in_accepted_state': self.fsm.in_accepted_state,
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'last_event': last_fsm_event
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}
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