asyncio.py

"""
    transitions.extensions.asyncio
    ------------------------------

    This module contains machine, state and event implementations for asynchronous callback processing.
    `AsyncMachine` and `HierarchicalAsyncMachine` use `asyncio` for concurrency. The extension `transitions-anyio`
    found at https://github.com/pytransitions/transitions-anyio illustrates how they can be extended to
    make use of other concurrency libraries.
    The module also contains the state mixin `AsyncTimeout` to asynchronously trigger timeout-related callbacks.
"""

# Overriding base methods of states, transitions and machines with async variants is not considered good practise.
# However, the alternative would mean to either increase the complexity of the base classes or copy code fragments
# and thus increase code complexity and reduce maintainability. If you know a better solution, please file an issue.
# pylint: disable=invalid-overridden-method

import logging
import asyncio
import contextvars
import inspect
import sys
import warnings
from collections import deque
from functools import partial, reduce
import copy

from ..core import State, Condition, Transition, EventData, listify
from ..core import Event, MachineError, Machine
from .nesting import HierarchicalMachine, NestedState, NestedEvent, NestedTransition, resolve_order


_LOGGER = logging.getLogger(__name__)
_LOGGER.addHandler(logging.NullHandler())


CANCELLED_MSG = "_transition"
"""A message passed to a cancelled task to indicate that the cancellation was caused by transitions."""


class AsyncState(State):
    """A persistent representation of a state managed by a ``Machine``. Callback execution is done asynchronously."""

    async def enter(self, event_data):
        """Triggered when a state is entered.
        Args:
            event_data: (AsyncEventData): The currently processed event.
        """
        _LOGGER.debug("%sEntering state %s. Processing callbacks...", event_data.machine.name, self.name)
        await event_data.machine.callbacks(self.on_enter, event_data)
        _LOGGER.info("%sFinished processing state %s enter callbacks.", event_data.machine.name, self.name)

    async def exit(self, event_data):
        """Triggered when a state is exited.
        Args:
            event_data: (AsyncEventData): The currently processed event.
        """
        _LOGGER.debug("%sExiting state %s. Processing callbacks...", event_data.machine.name, self.name)
        await event_data.machine.callbacks(self.on_exit, event_data)
        _LOGGER.info("%sFinished processing state %s exit callbacks.", event_data.machine.name, self.name)


class NestedAsyncState(NestedState, AsyncState):
    """A state that allows substates. Callback execution is done asynchronously."""

    async def scoped_enter(self, event_data, scope=None):
        self._scope = scope or []
        await self.enter(event_data)
        self._scope = []

    async def scoped_exit(self, event_data, scope=None):
        self._scope = scope or []
        await self.exit(event_data)
        self._scope = []


class AsyncCondition(Condition):
    """A helper class to await condition checks in the intended way."""

    async def check(self, event_data):
        """Check whether the condition passes.
        Args:
            event_data (EventData): An EventData instance to pass to the
                condition (if event sending is enabled) or to extract arguments
                from (if event sending is disabled). Also contains the data
                model attached to the current machine which is used to invoke
                the condition.
        """
        func = event_data.machine.resolve_callable(self.func, event_data)
        res = func(event_data) if event_data.machine.send_event else func(*event_data.args, **event_data.kwargs)
        if inspect.isawaitable(res):
            return await res == self.target
        return res == self.target


class AsyncTransition(Transition):
    """Representation of an asynchronous transition managed by a ``AsyncMachine`` instance."""

    condition_cls = AsyncCondition

    async def _eval_conditions(self, event_data):
        res = await event_data.machine.await_all([partial(cond.check, event_data) for cond in self.conditions])
        if not all(res):
            _LOGGER.debug("%sTransition condition failed: Transition halted.", event_data.machine.name)
            return False
        return True

    async def execute(self, event_data):
        """Executes the transition.
        Args:
            event_data (EventData): An instance of class EventData.
        Returns: boolean indicating whether or not the transition was
            successfully executed (True if successful, False if not).
        """
        _LOGGER.debug("%sInitiating transition from state %s to state %s...",
                      event_data.machine.name, self.source, self.dest)

        await event_data.machine.callbacks(self.prepare, event_data)
        _LOGGER.debug("%sExecuted callbacks before conditions.", event_data.machine.name)

        if not await self._eval_conditions(event_data):
            return False

        machine = event_data.machine
        # cancel running tasks since the transition will happen
        await machine.cancel_running_transitions(event_data.model)

        await event_data.machine.callbacks(event_data.machine.before_state_change, event_data)
        await event_data.machine.callbacks(self.before, event_data)
        _LOGGER.debug("%sExecuted callback before transition.", event_data.machine.name)

        if self.dest is not None:  # if self.dest is None this is an internal transition with no actual state change
            await self._change_state(event_data)

        await event_data.machine.callbacks(self.after, event_data)
        await event_data.machine.callbacks(event_data.machine.after_state_change, event_data)
        _LOGGER.debug("%sExecuted callback after transition.", event_data.machine.name)
        return True

    async def _change_state(self, event_data):
        if hasattr(event_data.machine, "model_graphs"):
            graph = event_data.machine.model_graphs[id(event_data.model)]
            graph.reset_styling()
            graph.set_previous_transition(self.source, self.dest)
        await event_data.machine.get_state(self.source).exit(event_data)
        event_data.machine.set_state(self.dest, event_data.model)
        event_data.update(getattr(event_data.model, event_data.machine.model_attribute))
        dest = event_data.machine.get_state(self.dest)
        await dest.enter(event_data)
        if dest.final:
            await event_data.machine.callbacks(event_data.machine.on_final, event_data)


class NestedAsyncTransition(AsyncTransition, NestedTransition):
    """Representation of an asynchronous transition managed by a ``HierarchicalMachine`` instance."""
    async def _change_state(self, event_data):
        if hasattr(event_data.machine, "model_graphs"):
            graph = event_data.machine.model_graphs[id(event_data.model)]
            graph.reset_styling()
            graph.set_previous_transition(self.source, self.dest)
        state_tree, exit_partials, enter_partials = self._resolve_transition(event_data)
        for func in exit_partials:
            await func()
        self._update_model(event_data, state_tree)
        for func in enter_partials:
            await func()
        with event_data.machine():
            on_final_cbs, _ = self._final_check(event_data, state_tree, enter_partials)
            for on_final_cb in on_final_cbs:
                await on_final_cb()


class AsyncEventData(EventData):
    """A redefinition of the base EventData intended to easy type checking."""


class AsyncEvent(Event):
    """A collection of transitions assigned to the same trigger"""

    async def trigger(self, model, *args, **kwargs):
        """Serially execute all transitions that match the current state,
        halting as soon as one successfully completes. Note that `AsyncEvent` triggers must be awaited.
        Args:
            args and kwargs: Optional positional or named arguments that will
                be passed onto the EventData object, enabling arbitrary state
                information to be passed on to downstream triggered functions.
        Returns: boolean indicating whether or not a transition was
            successfully executed (True if successful, False if not).
        """
        func = partial(self._trigger, EventData(None, self, self.machine, model, args=args, kwargs=kwargs))
        res = await self.machine.process_context(func, model)
        if res and await self.machine._can_trigger(model, "", *args, **kwargs):
            _LOGGER.debug("%sTriggering completion event", self.machine.name)
            res = await self.machine.events[""].trigger(model, *args, **kwargs)
        return res

    async def _trigger(self, event_data):
        event_data.state = self.machine.get_state(getattr(event_data.model, self.machine.model_attribute))
        try:
            if self._is_valid_source(event_data.state):
                await self._process(event_data)
        except BaseException as err:  # pylint: disable=broad-except; Exception will be handled elsewhere
            _LOGGER.error("%sException was raised while processing the trigger '%s': %s",
                          self.machine.name, event_data.event.name, repr(err))
            event_data.error = err
            if self.machine.on_exception:
                await self.machine.callbacks(self.machine.on_exception, event_data)
            else:
                raise
        finally:
            try:
                await self.machine.callbacks(self.machine.finalize_event, event_data)
                _LOGGER.debug("%sExecuted machine finalize callbacks", self.machine.name)
            except BaseException as err:  # pylint: disable=broad-except; Exception will be handled elsewhere
                _LOGGER.error("%sWhile executing finalize callbacks a %s occurred: %s.",
                              self.machine.name,
                              type(err).__name__,
                              str(err))
        return event_data.result

    async def _process(self, event_data):
        await self.machine.callbacks(self.machine.prepare_event, event_data)
        _LOGGER.debug("%sExecuted machine preparation callbacks before conditions.", self.machine.name)
        for trans in self.transitions[event_data.state.name]:
            event_data.transition = trans
            event_data.result = await trans.execute(event_data)
            if event_data.result:
                break


class NestedAsyncEvent(NestedEvent):
    """A collection of transitions assigned to the same trigger.
    This Event requires a (subclass of) `HierarchicalAsyncMachine`.
    """

    async def trigger_nested(self, event_data):
        """Serially execute all transitions that match the current state,
        halting as soon as one successfully completes. NOTE: This should only
        be called by HierarchicalMachine instances.
        Args:
            event_data (AsyncEventData): The currently processed event.
        Returns: boolean indicating whether or not a transition was
            successfully executed (True if successful, False if not).
        """
        machine = event_data.machine
        model = event_data.model
        state_tree = machine.build_state_tree(getattr(model, machine.model_attribute), machine.state_cls.separator)
        state_tree = reduce(dict.get, machine.get_global_name(join=False), state_tree)
        ordered_states = resolve_order(state_tree)
        done = set()
        event_data.event = self
        for state_path in ordered_states:
            state_name = machine.state_cls.separator.join(state_path)
            if state_name not in done and state_name in self.transitions:
                event_data.state = machine.get_state(state_name)
                event_data.source_name = state_name
                event_data.source_path = copy.copy(state_path)
                await self._process(event_data)
                if event_data.result:
                    elems = state_path
                    while elems:
                        done.add(machine.state_cls.separator.join(elems))
                        elems.pop()
        if event_data.result and await self.machine._can_trigger(model, "", *event_data.args, **event_data.kwargs):
            _LOGGER.debug("%sTriggering completion event", self.machine.name)
            event_data.result = await self.machine.events[""].trigger_nested(event_data)
        return event_data.result

    async def _process(self, event_data):
        machine = event_data.machine
        await machine.callbacks(event_data.machine.prepare_event, event_data)
        _LOGGER.debug("%sExecuted machine preparation callbacks before conditions.", machine.name)

        for trans in self.transitions[event_data.source_name]:
            event_data.transition = trans
            event_data.result = await trans.execute(event_data)
            if event_data.result:
                break


class AsyncMachine(Machine):
    """Machine manages states, transitions and models. In case it is initialized without a specific model
    (or specifically no model), it will also act as a model itself. Machine takes also care of decorating
    models with conveniences functions related to added transitions and states during runtime.

    Attributes:
        states (OrderedDict): Collection of all registered states.
        events (dict): Collection of transitions ordered by trigger/event.
        models (list): List of models attached to the machine.
        initial (str): Name of the initial state for new models.
        prepare_event (list): Callbacks executed when an event is triggered.
        before_state_change (list): Callbacks executed after condition checks but before transition is conducted.
            Callbacks will be executed BEFORE the custom callbacks assigned to the transition.
        after_state_change (list): Callbacks executed after the transition has been conducted.
            Callbacks will be executed AFTER the custom callbacks assigned to the transition.
        finalize_event (list): Callbacks will be executed after all transitions callbacks have been executed.
            Callbacks mentioned here will also be called if a transition or condition check raised an error.
        on_exception: A callable called when an event raises an exception. If not set,
            the Exception will be raised instead.
        queued (bool or str): Whether transitions in callbacks should be executed immediately (False) or sequentially.
        send_event (bool): When True, any arguments passed to trigger methods will be wrapped in an EventData
            object, allowing indirect and encapsulated access to data. When False, all positional and keyword
            arguments will be passed directly to all callback methods.
        auto_transitions (bool):  When True (default), every state will automatically have an associated
            to_{state}() convenience trigger in the base model.
        ignore_invalid_triggers (bool): When True, any calls to trigger methods that are not valid for the
            present state (e.g., calling an a_to_b() trigger when the current state is c) will be silently
            ignored rather than raising an invalid transition exception.
        name (str): Name of the ``Machine`` instance mainly used for easier log message distinction.
    """

    state_cls = AsyncState
    transition_cls = AsyncTransition
    event_cls = AsyncEvent
    async_tasks = {}
    protected_tasks = []
    current_context = contextvars.ContextVar('current_context', default=None)

    def __init__(self, model=Machine.self_literal, states=None, initial='initial', transitions=None,
                 send_event=False, auto_transitions=True,
                 ordered_transitions=False, ignore_invalid_triggers=None,
                 before_state_change=None, after_state_change=None, name=None,
                 queued=False, prepare_event=None, finalize_event=None, model_attribute='state',
                 model_override=False, on_exception=None, on_final=None, **kwargs):

        super().__init__(model=None, states=states, initial=initial, transitions=transitions,
                         send_event=send_event, auto_transitions=auto_transitions,
                         ordered_transitions=ordered_transitions, ignore_invalid_triggers=ignore_invalid_triggers,
                         before_state_change=before_state_change, after_state_change=after_state_change, name=name,
                         queued=bool(queued), prepare_event=prepare_event, finalize_event=finalize_event,
                         model_attribute=model_attribute, model_override=model_override,
                         on_exception=on_exception, on_final=on_final, **kwargs)

        self._transition_queue_dict = _DictionaryMock(self._transition_queue) if queued is True else {}
        self._queued = queued
        for model in listify(model):
            self.add_model(model)

    def add_model(self, model, initial=None):
        super().add_model(model, initial)
        if self.has_queue == 'model':
            for mod in listify(model):
                self._transition_queue_dict[id(self) if mod is self.self_literal else id(mod)] = deque()

    async def dispatch(self, trigger, *args, **kwargs):
        """Trigger an event on all models assigned to the machine.
        Args:
            trigger (str): Event name
            *args (list): List of arguments passed to the event trigger
            **kwargs (dict): Dictionary of keyword arguments passed to the event trigger
        Returns:
            bool The truth value of all triggers combined with AND
        """
        results = await self.await_all([partial(getattr(model, trigger), *args, **kwargs) for model in self.models])
        return all(results)

    async def callbacks(self, funcs, event_data):
        """Triggers a list of callbacks"""
        await self.await_all([partial(event_data.machine.callback, func, event_data) for func in funcs])

    async def callback(self, func, event_data):
        """Trigger a callback function with passed event_data parameters. In case func is a string,
            the callable will be resolved from the passed model in event_data. This function is not intended to
            be called directly but through state and transition callback definitions.
        Args:
            func (string, callable): The callback function.
                1. First, if the func is callable, just call it
                2. Second, we try to import string assuming it is a path to a func
                3. Fallback to a model attribute
            event_data (EventData): An EventData instance to pass to the
                callback (if event sending is enabled) or to extract arguments
                from (if event sending is disabled).
        """
        func = self.resolve_callable(func, event_data)
        res = func(event_data) if self.send_event else func(*event_data.args, **event_data.kwargs)
        if inspect.isawaitable(res):
            await res

    @staticmethod
    async def await_all(callables):
        """
        Executes callables without parameters in parallel and collects their results.
        Args:
            callables (list): A list of callable functions

        Returns:
            list: A list of results. Using asyncio the list will be in the same order as the passed callables.
        """
        return await asyncio.gather(*[func() for func in callables])

    async def switch_model_context(self, model):
        warnings.warn("Please replace 'AsyncMachine.switch_model_context' with "
                      "'AsyncMachine.cancel_running_transitions'.", category=DeprecationWarning)
        await self.cancel_running_transitions(model)

    async def cancel_running_transitions(self, model, msg=None):
        """
        This method is called by an `AsyncTransition` when all conditional tests have passed
        and the transition will happen. This requires already running tasks to be cancelled.
        Args:
            model (object): The currently processed model
            msg (str): Optional message to pass to a running task's cancel request (deprecated).
        """
        if msg is not None:
            warnings.warn(
                "When you call cancel_running_transitions with a custom message "
                "transitions will re-raise all raised CancelledError. "
                "Make sure to catch them in your code. "
                "The parameter 'msg' will likely be removed in a future release.", category=DeprecationWarning)
        for running_task in self.async_tasks.get(id(model), []):
            if self.current_context.get() == running_task or running_task in self.protected_tasks:
                continue
            if running_task.done() is False:
                _LOGGER.debug("Cancel running tasks...")
                running_task.cancel(msg or CANCELLED_MSG)

    async def process_context(self, func, model):
        """
        This function is called by an `AsyncEvent` to make callbacks processed in Event._trigger cancellable.
        Using asyncio this will result in a try-catch block catching CancelledEvents.
        Args:
            func (partial): The partial of Event._trigger with all parameters already assigned
            model (object): The currently processed model

        Returns:
            bool: returns the success state of the triggered event
        """
        if self.current_context.get() is None:
            token = self.current_context.set(asyncio.current_task())
            if id(model) in self.async_tasks:
                self.async_tasks[id(model)].append(asyncio.current_task())
            else:
                self.async_tasks[id(model)] = [asyncio.current_task()]
            try:
                res = await self._process_async(func, model)
            except asyncio.CancelledError as err:
                # raise CancelledError only if the task was not cancelled by internal processes
                # we indicate internal cancellation by passing CANCELLED_MSG to cancel()
                if CANCELLED_MSG not in err.args and sys.version_info >= (3, 11):
                    _LOGGER.debug("%sExternal cancellation of task. Raise CancelledError...", self.name)
                    raise
                res = False
            finally:
                self.async_tasks[id(model)].remove(asyncio.current_task())
                self.current_context.reset(token)
                if len(self.async_tasks[id(model)]) == 0:
                    del self.async_tasks[id(model)]
        else:
            res = await self._process_async(func, model)
        return res

    def remove_model(self, model):
        """Remove a model from the state machine. The model will still contain all previously added triggers
        and callbacks, but will not receive updates when states or transitions are added to the Machine.
        If an event queue is used, all queued events of that model will be removed."""
        models = listify(model)
        if self.has_queue == 'model':
            for mod in models:
                del self._transition_queue_dict[id(mod)]
                self.models.remove(mod)
        else:
            for mod in models:
                self.models.remove(mod)
        if len(self._transition_queue) > 0:
            queue = self._transition_queue
            new_queue = [queue.popleft()] + [e for e in queue if e.args[0].model not in models]
            self._transition_queue.clear()
            self._transition_queue.extend(new_queue)

    async def _can_trigger(self, model, trigger, *args, **kwargs):
        state = self.get_model_state(model)
        event_data = AsyncEventData(state, AsyncEvent(name=trigger, machine=self), self, model, args, kwargs)

        for trigger_name in self.get_triggers(state):
            if trigger_name != trigger:
                continue
            for transition in self.events[trigger_name].transitions[state.name]:
                try:
                    _ = self.get_state(transition.dest) if transition.dest is not None else transition.source
                except ValueError:
                    continue
                event_data.transition = transition
                try:
                    await self.callbacks(self.prepare_event, event_data)
                    await self.callbacks(transition.prepare, event_data)
                    if all(await self.await_all([partial(c.check, event_data) for c in transition.conditions])):
                        return True
                except BaseException as err:
                    event_data.error = err
                    if self.on_exception:
                        await self.callbacks(self.on_exception, event_data)
                    else:
                        raise
        return False

    def _process(self, trigger):
        raise RuntimeError("AsyncMachine should not call `Machine._process`. Use `Machine._process_async` instead.")

    async def _process_async(self, trigger, model):
        # default processing
        if not self.has_queue:
            if not self._transition_queue:
                # if trigger raises an Error, it has to be handled by the Machine.process caller
                return await trigger()
            raise MachineError("Attempt to process events synchronously while transition queue is not empty!")

        self._transition_queue_dict[id(model)].append(trigger)
        # another entry in the queue implies a running transition; skip immediate execution
        if len(self._transition_queue_dict[id(model)]) > 1:
            return True

        while self._transition_queue_dict[id(model)]:
            try:
                await self._transition_queue_dict[id(model)][0]()
            except BaseException:
                # if a transition raises an exception, clear queue and delegate exception handling
                self._transition_queue_dict[id(model)].clear()
                raise
            try:
                self._transition_queue_dict[id(model)].popleft()
            except KeyError:
                return True
        return True


class HierarchicalAsyncMachine(HierarchicalMachine, AsyncMachine):
    """Asynchronous variant of transitions.extensions.nesting.HierarchicalMachine.
        An asynchronous hierarchical machine REQUIRES AsyncNestedStates, AsyncNestedEvent and AsyncNestedTransitions
        (or any subclass of it) to operate.
    """

    state_cls = NestedAsyncState
    transition_cls = NestedAsyncTransition
    event_cls = NestedAsyncEvent

    async def trigger_event(self, model, trigger, *args, **kwargs):
        """Processes events recursively and forwards arguments if suitable events are found.
        This function is usually bound to models with model and trigger arguments already
        resolved as a partial. Execution will halt when a nested transition has been executed
        successfully.
        Args:
            model (object): targeted model
            trigger (str): event name
            *args: positional parameters passed to the event and its callbacks
            **kwargs: keyword arguments passed to the event and its callbacks
        Returns:
            bool: whether a transition has been executed successfully
        Raises:
            MachineError: When no suitable transition could be found and ignore_invalid_trigger
                          is not True. Note that a transition which is not executed due to conditions
                          is still considered valid.
        """
        event_data = AsyncEventData(state=None, event=None, machine=self, model=model, args=args, kwargs=kwargs)
        event_data.result = None

        return await self.process_context(partial(self._trigger_event, event_data, trigger), model)

    async def _trigger_event(self, event_data, trigger):
        try:
            with self():
                res = await self._trigger_event_nested(event_data, trigger, None)
            event_data.result = self._check_event_result(res, event_data.model, trigger)
        except BaseException as err:  # pylint: disable=broad-except; Exception will be handled elsewhere
            event_data.error = err
            if self.on_exception:
                await self.callbacks(self.on_exception, event_data)
            else:
                raise
        finally:
            try:
                await self.callbacks(self.finalize_event, event_data)
                _LOGGER.debug("%sExecuted machine finalize callbacks", self.name)
            except BaseException as err:  # pylint: disable=broad-except; Exception will be handled elsewhere
                _LOGGER.error("%sWhile executing finalize callbacks a %s occurred: %s.",
                              self.name,
                              type(err).__name__,
                              str(err))
        return event_data.result

    async def _trigger_event_nested(self, event_data, _trigger, _state_tree):
        model = event_data.model
        if _state_tree is None:
            _state_tree = self.build_state_tree(listify(getattr(model, self.model_attribute)),
                                                self.state_cls.separator)
        res = {}
        for key, value in _state_tree.items():
            if value:
                with self(key):
                    tmp = await self._trigger_event_nested(event_data, _trigger, value)
                    if tmp is not None:
                        res[key] = tmp
            if not res.get(key, None) and _trigger in self.events:
                tmp = await self.events[_trigger].trigger_nested(event_data)
                if tmp is not None:
                    res[key] = tmp
        return None if not res or all(v is None for v in res.values()) else any(res.values())

    async def _can_trigger(self, model, trigger, *args, **kwargs):
        state_tree = self.build_state_tree(getattr(model, self.model_attribute), self.state_cls.separator)
        ordered_states = resolve_order(state_tree)
        for state_path in ordered_states:
            with self():
                return await self._can_trigger_nested(model, trigger, state_path, *args, **kwargs)

    async def _can_trigger_nested(self, model, trigger, path, *args, **kwargs):
        if trigger in self.events:
            source_path = copy.copy(path)
            while source_path:
                event_data = AsyncEventData(self.get_state(source_path), AsyncEvent(name=trigger, machine=self), self,
                                            model, args, kwargs)
                state_name = self.state_cls.separator.join(source_path)
                for transition in self.events[trigger].transitions.get(state_name, []):
                    try:
                        _ = self.get_state(transition.dest) if transition.dest is not None else transition.source
                    except ValueError:
                        continue
                    event_data.transition = transition
                    try:
                        await self.callbacks(self.prepare_event, event_data)
                        await self.callbacks(transition.prepare, event_data)
                        if all(await self.await_all([partial(c.check, event_data) for c in transition.conditions])):
                            return True
                    except BaseException as err:
                        event_data.error = err
                        if self.on_exception:
                            await self.callbacks(self.on_exception, event_data)
                        else:
                            raise
                source_path.pop(-1)
        if path:
            with self(path.pop(0)):
                return await self._can_trigger_nested(model, trigger, path, *args, **kwargs)
        return False


class AsyncTimeout(AsyncState):
    """
    Adds timeout functionality to an asynchronous state. Timeouts are handled model-specific.

    Attributes:
        timeout (float): Seconds after which a timeout function should be
                         called.
        on_timeout (list): Functions to call when a timeout is triggered.
        runner (dict): Keeps track of running timeout tasks to cancel when a state is exited.
    """

    dynamic_methods = ["on_timeout"]

    def __init__(self, *args, **kwargs):
        """
        Args:
            **kwargs: If kwargs contain 'timeout', assign the float value to
                self.timeout. If timeout is set, 'on_timeout' needs to be
                passed with kwargs as well or an AttributeError will be thrown
                if timeout is not passed or equal 0.
        """
        self.timeout = kwargs.pop("timeout", 0)
        self._on_timeout = None
        if self.timeout > 0:
            try:
                self.on_timeout = kwargs.pop("on_timeout")
            except KeyError:
                raise AttributeError("Timeout state requires 'on_timeout' when timeout is set.") from None
        else:
            self.on_timeout = kwargs.pop("on_timeout", None)
        self.runner = {}
        super().__init__(*args, **kwargs)

    async def enter(self, event_data):
        """
        Extends `transitions.core.State.enter` by starting a timeout timer for
        the current model when the state is entered and self.timeout is larger
        than 0.

        Args:
            event_data (EventData): events representing the currently processed event.
        """
        if self.timeout > 0:
            self.runner[id(event_data.model)] = self.create_timer(event_data)
        await super().enter(event_data)

    async def exit(self, event_data):
        """
        Cancels running timeout tasks stored in `self.runner` first (when not note) before
        calling further exit callbacks.

        Args:
            event_data (EventData): Data representing the currently processed event.

        Returns:

        """
        timer_task = self.runner.get(id(event_data.model), None)
        if timer_task is not None and not timer_task.done():
            timer_task.cancel()
        await super().exit(event_data)

    def create_timer(self, event_data):
        """
        Creates and returns a running timer. Shields self._process_timeout to prevent cancellation when
        transitioning away from the current state (which cancels the timer) while processing timeout callbacks.
        Args:
            event_data (EventData): Data representing the currently processed event.

        Returns (cancellable): A running timer with a cancel method
        """
        async def _timeout():
            await asyncio.sleep(self.timeout)
            await asyncio.shield(self._process_timeout(event_data))
        return asyncio.create_task(_timeout())

    async def _process_timeout(self, event_data):
        _LOGGER.debug("%sTimeout state %s. Processing callbacks...", event_data.machine.name, self.name)
        event_data = AsyncEventData(event_data.state, AsyncEvent("timeout", event_data.machine),
                                    event_data.machine, event_data.model, args=tuple(), kwargs={})
        token = AsyncMachine.current_context.set(None)
        try:
            await event_data.machine.callbacks(self.on_timeout, event_data)
        except BaseException as err:
            _LOGGER.warning("%sException raised while processing timeout!",
                            event_data.machine.name)
            event_data.error = err
            try:
                if event_data.machine.on_exception:
                    await event_data.machine.callbacks(event_data.machine.on_exception, event_data)
                else:
                    raise
            except BaseException as err2:
                _LOGGER.error("%sHandling timeout exception '%s' caused another exception: %s. "
                              "Cancel running transitions...", event_data.machine.name, repr(err), repr(err2))
                await event_data.machine.cancel_running_transitions(event_data.model)
        finally:
            AsyncMachine.current_context.reset(token)
        _LOGGER.info("%sTimeout state %s processed.", event_data.machine.name, self.name)

    @property
    def on_timeout(self):
        """
        List of strings and callables to be called when the state timeouts.
        """
        return self._on_timeout

    @on_timeout.setter
    def on_timeout(self, value):
        """Listifies passed values and assigns them to on_timeout."""
        self._on_timeout = listify(value)


class _DictionaryMock(dict):

    def __init__(self, item):
        super().__init__()
        self._value = item

    def __setitem__(self, key, item):
        self._value = item

    def __getitem__(self, key):
        return self._value

    def __repr__(self):
        return repr("{{'*': {0}}}".format(self._value))