baseimage-tutorial-framework/lib/tfw/fsm_base.py

from typing import List

from transitions import Machine


class FSMBase:
    states, transitions = [], []

    def __init__(self, initial: str = None, accepted_states: List[str] = None):
        self.callbacks = []
        self.accepted_states = accepted_states or [self.states[-1]]
        self.machine = Machine(model=self,
                               states=self.states,
                               transitions=self.transitions,
                               initial=initial or self.states[0],
                               send_event=True,
                               ignore_invalid_triggers=True,
                               after_state_change='execute_callbacks')

    def execute_callbacks(self, event_data):
        for callback in self.callbacks:
            callback(event_data.kwargs)

    def subscribe(self, callback):
        self.callbacks.append(callback)

    def unsubscribe(self, callback):
        self.callbacks.remove(callback)

    def is_solved(self):
        return self.state in self.accepted_states