from transitions import Machine


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

    def __init__(self, initial: str = None):
        self.message_handlers = []
        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='forward_message')

    def forward_message(self, event_data):
        message = event_data.kwargs.get('message')
        for msghandler in self.message_handlers:
            msghandler(message)

    def subscribe_message_handler(self, msghandler):
        self.message_handlers.append(msghandler)

    def unsubscribe_message_handler(self, msghandler):
        self.message_handlers.remove(msghandler)