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https://github.com/avatao-content/baseimage-tutorial-framework
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85 lines
2.8 KiB
Python
85 lines
2.8 KiB
Python
import logging
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from collections import defaultdict
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from datetime import datetime
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from transitions import Machine, MachineError
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from tfw.internals.callback_mixin import CallbackMixin
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LOG = logging.getLogger(__name__)
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class FSMBase(Machine, CallbackMixin):
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"""
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A general FSM base class you can inherit from to track user progress.
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See linear_fsm.py for an example use-case.
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TFW uses the transitions library for state machines, please refer to their
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documentation for more information on creating your own machines:
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https://github.com/pytransitions/transitions
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"""
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states, transitions = [], []
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def __init__(self, initial=None, accepted_states=None):
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"""
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:param initial: which state to begin with, defaults to the last one
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:param accepted_states: list of states in which the challenge should be
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considered successfully completed
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"""
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self.accepted_states = accepted_states or [self.states[-1].name]
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self.trigger_predicates = defaultdict(list)
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self.event_log = []
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Machine.__init__(
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self,
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states=self.states,
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transitions=self.transitions,
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initial=initial or self.states[0],
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send_event=True,
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ignore_invalid_triggers=True,
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after_state_change='execute_callbacks'
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)
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def execute_callbacks(self, event_data):
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self._execute_callbacks(event_data.kwargs)
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def is_solved(self):
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return self.state in self.accepted_states # pylint: disable=no-member
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def subscribe_predicate(self, trigger, *predicates):
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self.trigger_predicates[trigger].extend(predicates)
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def unsubscribe_predicate(self, trigger, *predicates):
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self.trigger_predicates[trigger] = [
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predicate
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for predicate in self.trigger_predicates[trigger]
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not in predicates
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]
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def step(self, trigger):
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predicate_results = (
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predicate()
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for predicate in self.trigger_predicates[trigger]
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)
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if all(predicate_results):
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try:
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from_state = self.state
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self.trigger(trigger)
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self.update_event_log(from_state, trigger)
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return True
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except (AttributeError, MachineError):
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LOG.debug('FSM failed to execute nonexistent trigger: "%s"', trigger)
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return False
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def update_event_log(self, from_state, trigger):
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self.event_log.append({
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'from_state': from_state,
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'to_state': self.state,
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'trigger': trigger,
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'timestamp': datetime.utcnow().isoformat()
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})
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@property
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def in_accepted_state(self):
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return self.state in self.accepted_states
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