# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
# All Rights Reserved. See LICENSE file for details.

from collections import defaultdict

from transitions import Machine, MachineError

from tfw.mixins import CallbackMixin
from tfw.config.logs import logging

LOG = logging.getLogger(__name__)


class FSMBase(Machine, CallbackMixin):
    """
    A general FSM base class you can inherit from to track user progress.
    See linear_fsm.py for an example use-case.
    TFW uses the transitions library for state machines, please refer to their
    documentation for more information on creating your own machines:
    https://github.com/pytransitions/transitions
    """
    states, transitions = [], []

    def __init__(self, initial=None, accepted_states=None):
        self.accepted_states = accepted_states or [self.states[-1]]
        self.trigger_predicates = defaultdict(list)
        self.trigger_history = []

        Machine.__init__(
            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):
        self._execute_callbacks(event_data.kwargs)

    def is_solved(self):
        return self.state in self.accepted_states  # pylint: disable=no-member

    def subscribe_predicate(self, trigger, *predicates):
        self.trigger_predicates[trigger].extend(predicates)

    def unsubscribe_predicate(self, trigger, *predicates):
        self.trigger_predicates[trigger] = [
            predicate
            for predicate in self.trigger_predicates[trigger]
            not in predicates
        ]

    def step(self, trigger):
        predicate_results = (
            predicate()
            for predicate in self.trigger_predicates[trigger]
        )

        if all(predicate_results):
            try:
                self.trigger(trigger)
                self.trigger_history.append(trigger)
            except (AttributeError, MachineError):
                LOG.debug('FSM failed to execute nonexistent trigger: "%s"', trigger)