nesting.py

# -*- coding: utf-8 -*-
from collections import OrderedDict, defaultdict
import copy
from functools import partial, reduce
import inspect
import logging

from six import string_types

from ..core import State, Machine, Transition, Event, listify, MachineError, Enum, EnumMeta, EventData

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

# this is a workaround for dill issues when partials and super is used in conjunction
# without it, Python 3.0 - 3.3 will not support pickling
# https://github.com/pytransitions/transitions/issues/236
_super = super


# converts a hierarchical tree into a list of current states
def _build_state_list(state_tree, separator, prefix=[]):
    res = []
    for key, value in state_tree.items():
        if value:
            res.append(_build_state_list(value, separator, prefix=prefix + [key]))
        else:
            res.append(separator.join(prefix + [key]))
    return res if len(res) > 1 else res[0]


# custom breadth-first tree exploration
# makes sure that ALL children are evaluated before parents in parallel states
def _resolve_order(state_tree):
    s = state_tree
    q = []
    res = []
    p = []
    while True:
        for k in reversed(list(s.keys())):
            pk = p + [k]
            res.append(pk)
            if s[k]:
                q.append((pk, s[k]))
        if not q:
            break
        p, s = q.pop(0)
    return reversed(res)


class FunctionWrapper(object):
    """ A wrapper to enable transitions' convenience function to_<state> for nested states.
        This allows to call model.to_A.s1.C() in case a custom separator has been chosen."""
    def __init__(self, func, path):
        """
        Args:
            func: Function to be called at the end of the path.
            path: If path is an empty string, assign function
        """
        if path:
            self.add(func, path)
            self._func = None
        else:
            self._func = func

    def add(self, func, path):
        """ Assigns a `FunctionWrapper` as an attribute named like the next segment of the substates
            path.
        Args:
            func (callable): Function to be called at the end of the path.
            path (string): Remaining segment of the substate path.
        """
        if path:
            name = path[0]
            if name[0].isdigit():
                name = 's' + name
            if hasattr(self, name):
                getattr(self, name).add(func, path[1:])
            else:
                setattr(self, name, FunctionWrapper(func, path[1:]))
        else:
            self._func = func

    def __call__(self, *args, **kwargs):
        return self._func(*args, **kwargs)


class NestedEvent(Event):
    """ An event type to work with nested states.
        This subclass is NOT compatible with simple Machine instances.
    """

    def trigger(self, _model, _machine, *args, **kwargs):
        """ Executes all transitions that match the current state,
        halting as soon as one successfully completes. More precisely, it prepares a partial
        of the internal ``_trigger`` function, passes this to ``machine._process``.
        It is up to the machine's configuration of the Event whether processing happens queued (sequentially) or
        whether further Events are processed as they occur. NOTE: This should only
        be called by HierarchicalMachine instances.
        Args:
            _model (object): The currently processed model
            _machine (HierarchicalMachine): Since NestedEvents can be used in multiple machine instances, this one
                                            will be used to determine the current state separator and the current scope.
            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).
        """
        # Save the current scope (_machine.scoped, _machine.states, _machine.events) in partial
        # since queued transitions could otherwise loose their scope.
        func = partial(self._trigger, _model, _machine,
                       (_machine.scoped, _machine.states, _machine.events, _machine.prefix_path),
                       *args, **kwargs)
        # pylint: disable=protected-access
        # noinspection PyProtectedMember
        # Machine._process should not be called somewhere else. That's why it should not be exposed
        # to Machine users.
        return _machine._process(func)

    def _trigger(self, _model, _machine, _scope, *args, **kwargs):
        """ Internal trigger function called by the ``HierarchicalMachine`` instance. This should not
        be called directly but via the public method ``HierarchicalMachine.process``. In contrast to
        the inherited ``Event._trigger``, this requires a scope tuple to process triggers in the right context.
        Args:
            _model (object): The currently processed model
            _machine (HierarchicalMachine): The machine that should be used to process the event
            _scope (Tuple): A tuple containing information about the currently scoped object, states an transitions.
            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).
        """
        if _scope[0] != _machine.scoped:
            with _machine(_scope):
                return self._trigger_scoped(_model, _machine, *args, **kwargs)
        else:
            return self._trigger_scoped(_model, _machine, *args, **kwargs)

    def _trigger_scoped(self, _model, _machine, *args, **kwargs):
        """ Internal scope-adjusted trigger function called by the ``NestedEvent._trigger`` instance. This should not
        be called directly.
        Args:
            _model (object): The currently processed model
            _machine (HierarchicalMachine): The machine that should be used to process the event
            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).
        """
        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()
        res = None
        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:
                state = _machine.get_state(state_name)
                event_data = EventData(state, self, _machine, _model, args=args, kwargs=kwargs)
                event_data.source_name = state_name
                event_data.source_path = copy.copy(state_path)
                res = self._process(event_data)
                if res:
                    elems = state_path
                    while elems:
                        done.add(_machine.state_cls.separator.join(elems))
                        elems.pop()
        return res

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

        try:
            for trans in self.transitions[event_data.source_name]:
                event_data.transition = trans
                if trans.execute(event_data):
                    event_data.result = True
                    break
        except Exception as err:
            event_data.error = err
            if self.machine.on_exception:
                self.machine.callbacks(self.machine.on_exception, event_data)
            else:
                raise
        finally:
            try:
                machine.callbacks(machine.finalize_event, event_data)
                _LOGGER.debug("%sExecuted machine finalize callbacks", machine.name)
            except Exception as err:
                _LOGGER.error("%sWhile executing finalize callbacks a %s occurred: %s.",
                              self.machine.name,
                              type(err).__name__,
                              str(err))
        return event_data.result


class NestedState(State):
    """ A state which allows substates.
    Attributes:
        states (OrderedDict): A list of substates of the current state.
        events (dict): A list of events defined for the nested state.
        initial (list, str, NestedState or Enum): (Name of a) child or list of children that should be entered when the state is entered.
        exit_stack (defaultdict): A list of currently active substates
    """

    separator = '_'
    u""" Separator between the names of parent and child states. In case '_' is required for
        naming state, this value can be set to other values such as '.' or even unicode characters
        such as '↦' (limited to Python 3 though).
    """

    def __init__(self, name, on_enter=None, on_exit=None, ignore_invalid_triggers=None, initial=None):
        _super(NestedState, self).__init__(name=name, on_enter=on_enter, on_exit=on_exit,
                                           ignore_invalid_triggers=ignore_invalid_triggers)
        self.initial = initial
        self.events = {}
        self.states = OrderedDict()
        self._scope = []

    def add_substate(self, state):
        """ Adds a state as a substate.
        Args:
            state (NestedState): State to add to the current state.
        """
        self.add_substates(state)

    def add_substates(self, states):
        """ Adds a list of states to the current state.
        Args:
            states (list): List of states to add to the current state.
        """
        for state in listify(states):
            self.states[state.name] = state

    def scoped_enter(self, event_data, scope=[]):
        self._scope = scope
        try:
            self.enter(event_data)
        finally:
            self._scope = []

    def scoped_exit(self, event_data, scope=[]):
        self._scope = scope
        try:
            self.exit(event_data)
        finally:
            self._scope = []

    @property
    def name(self):
        return self.separator.join(self._scope + [_super(NestedState, self).name])


class NestedTransition(Transition):
    """ A transition which handles entering and leaving nested states.

    Attributes:
        source (str): Source state of the transition.
        dest (str): Destination state of the transition.
        prepare (list): Callbacks executed before conditions checks.
        conditions (list): Callbacks evaluated to determine if
            the transition should be executed.
        before (list): Callbacks executed before the transition is executed
            but only if condition checks have been successful.
        after (list): Callbacks executed after the transition is executed
            but only if condition checks have been successful.
    """

    def _resolve_transition(self, event_data):
        machine = event_data.machine
        dst_name_path = self.dest.split(event_data.machine.state_cls.separator)
        _ = machine.get_state(dst_name_path)
        model_states = listify(getattr(event_data.model, machine.model_attribute))
        state_tree = machine._build_state_tree(model_states, machine.state_cls.separator)

        scope = machine.get_global_name(join=False)
        src_name_path = event_data.source_path
        if src_name_path == dst_name_path:
            root = src_name_path[:-1]  # exit and enter the same state
            dst_name_path = dst_name_path[-1:]
        else:
            tmp_tree = state_tree.get(dst_name_path[0], None)
            root = []
            while tmp_tree is not None:
                root.append(dst_name_path.pop(0))
                tmp_tree = tmp_tree.get(dst_name_path[0], None) if len(dst_name_path) > 0 else None

        scoped_tree = reduce(dict.get, scope + root, state_tree)
        exit_partials = [partial(machine.get_state(root + state_name).scoped_exit,
                                 event_data, scope + root + state_name[:-1])
                         for state_name in _resolve_order(scoped_tree)]
        if dst_name_path:
            new_states, enter_partials = self._enter_nested(root, dst_name_path, scope + root, event_data)
        else:
            new_states, enter_partials = {}, []

        scoped_tree.clear()
        for new_key, value in new_states.items():
            scoped_tree[new_key] = value
            break

        return state_tree, exit_partials, enter_partials

    def _change_state(self, event_data):
        state_tree, exit_partials, enter_partials = self._resolve_transition(event_data)
        for func in exit_partials:
            func()
        self._update_model(event_data, state_tree)
        for func in enter_partials:
            func()

    def _enter_nested(self, root, dest, prefix_path, event_data):
        if root:
            state_name = root.pop(0)
            with event_data.machine(state_name):
                return self._enter_nested(root, dest, prefix_path, event_data)
        elif dest:
            new_states = OrderedDict()
            state_name = dest.pop(0)
            with event_data.machine(state_name):
                new_states[state_name], new_enter = self._enter_nested([], dest, prefix_path + [state_name], event_data)
                enter_partials = [partial(event_data.machine.scoped.scoped_enter, event_data, prefix_path)] + new_enter
            return new_states, enter_partials
        elif event_data.machine.scoped.initial:
            new_states = OrderedDict()
            enter_partials = []
            q = []
            prefix = prefix_path
            scoped_tree = new_states
            initial_names = [i.name if hasattr(i, 'name') else i for i in listify(event_data.machine.scoped.initial)]
            initial_states = [event_data.machine.scoped.states[n] for n in initial_names]
            while True:
                event_data.scope = prefix
                for state in initial_states:
                    enter_partials.append(partial(state.scoped_enter, event_data, prefix))
                    scoped_tree[state.name] = OrderedDict()
                    if state.initial:
                        q.append((scoped_tree[state.name], prefix + [state.name],
                                  [state.states[i.name] if hasattr(i, 'name') else state.states[i]
                                   for i in listify(state.initial)]))
                if not q:
                    break
                scoped_tree, prefix, initial_states = q.pop(0)
            return new_states, enter_partials
        else:
            return {}, []

    @staticmethod
    def _update_model(event_data, tree):
        model_states = _build_state_list(tree, event_data.machine.state_cls.separator)
        with event_data.machine():
            event_data.machine.set_state(model_states, event_data.model)
            states = event_data.machine.get_states(listify(model_states))
            event_data.state = states[0] if len(states) == 1 else states

    # Prevent deep copying of callback lists since these include either references to callable or
    # strings. Deep copying a method reference would lead to the creation of an entire new (model) object
    # (see https://github.com/pytransitions/transitions/issues/248)
    def __deepcopy__(self, memo):
        cls = self.__class__
        result = cls.__new__(cls)
        memo[id(self)] = result
        for key, value in self.__dict__.items():
            if key in cls.dynamic_methods:
                setattr(result, key, copy.copy(value))
            else:
                setattr(result, key, copy.deepcopy(value, memo))
        return result


class HierarchicalMachine(Machine):
    """ Extends transitions.core.Machine by capabilities to handle nested states.
        A hierarchical machine REQUIRES NestedStates, NestedEvent and NestedTransitions
        (or any subclass of it) to operate.
    """

    state_cls = NestedState
    transition_cls = NestedTransition
    event_cls = NestedEvent

    def __init__(self, *args, **kwargs):
        assert issubclass(self.state_cls, NestedState)
        assert issubclass(self.event_cls, NestedEvent)
        assert issubclass(self.transition_cls, NestedTransition)
        self._stack = []
        self.prefix_path = []
        self.scoped = self
        _super(HierarchicalMachine, self).__init__(*args, **kwargs)

    def __call__(self, to_scope=None):
        if isinstance(to_scope, string_types):
            state_name = to_scope.split(self.state_cls.separator)[0]
            state = self.states[state_name]
            to_scope = (state, state.states, state.events, self.prefix_path + [state_name])
        elif isinstance(to_scope, Enum):
            state = self.states[to_scope.name]
            to_scope = (state, state.states, state.events, self.prefix_path + [to_scope.name])
        elif to_scope is None:
            if self._stack:
                to_scope = self._stack[0]
            else:
                to_scope = (self, self.states, self.events, [])
        self._next_scope = to_scope

        return self

    def __enter__(self):
        self._stack.append((self.scoped, self.states, self.events, self.prefix_path))
        self.scoped, self.states, self.events, self.prefix_path = self._next_scope
        self._next_scope = None

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.scoped, self.states, self.events, self.prefix_path = self._stack.pop()

    def add_model(self, model, initial=None):
        """ Extends transitions.core.Machine.add_model by applying a custom 'to' function to
            the added model.
        """
        models = [self if mod is self.self_literal else mod for mod in listify(model)]
        _super(HierarchicalMachine, self).add_model(models, initial=initial)
        initial_name = getattr(models[0], self.model_attribute)
        if hasattr(initial_name, 'name'):
            initial_name = initial_name.name
        # initial states set by add_model or machine might contain initial states themselves.
        if isinstance(initial_name, string_types):
            initial_states = self._resolve_initial(models, initial_name.split(self.state_cls.separator))
        # when initial is set to a (parallel) state, we accept it as it is
        else:
            initial_states = initial_name
        for mod in models:
            self.set_state(initial_states, mod)
            if hasattr(mod, 'to'):
                _LOGGER.warning("%sModel already has a 'to'-method. It will NOT "
                                "be overwritten by NestedMachine", self.name)
            else:
                to_func = partial(self.to_state, mod)
                setattr(mod, 'to', to_func)

    @property
    def initial(self):
        """ Return the initial state. """
        return self._initial

    @initial.setter
    def initial(self, value):
        self._initial = self._recursive_initial(value)

    def add_ordered_transitions(self, states=None, trigger='next_state',
                                loop=True, loop_includes_initial=True,
                                conditions=None, unless=None, before=None,
                                after=None, prepare=None, **kwargs):
        if states is None:
            states = self.get_nested_state_names()
        _super(HierarchicalMachine, self).add_ordered_transitions(states=states, trigger=trigger, loop=loop,
                                                                  loop_includes_initial=loop_includes_initial,
                                                                  conditions=conditions,
                                                                  unless=unless, before=before, after=after,
                                                                  prepare=prepare, **kwargs)

    def add_states(self, states, on_enter=None, on_exit=None, ignore_invalid_triggers=None, **kwargs):
        """ Add new nested state(s).
        Args:
            states (list, str, dict, Enum, NestedState or Machine): a list, a NestedState instance, the
                name of a new state, an enumeration (member) or a dict with keywords to pass on to the
                NestedState initializer. If a list, each element can be a string, dict, NestedState or
                enumeration member.
            on_enter (str or list): callbacks to trigger when the state is
                entered. Only valid if first argument is string.
            on_exit (str or list): callbacks to trigger when the state is
                exited. Only valid if first argument is string.
            ignore_invalid_triggers: 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.
                Note that this argument takes precedence over the same
                argument defined at the Machine level, and is in turn
                overridden by any ignore_invalid_triggers explicitly
                passed in an individual state's initialization arguments.
            **kwargs additional keyword arguments used by state mixins.
        """
        remap = kwargs.pop('remap', None)
        ignore = self.ignore_invalid_triggers if ignore_invalid_triggers is None else ignore_invalid_triggers

        for state in listify(states):
            if isinstance(state, Enum):
                if isinstance(state.value, EnumMeta):
                    state = {'name': state, 'children': state.value}
                elif isinstance(state.value, dict):
                    state = dict(name=state, **state.value)
            if isinstance(state, string_types):
                if remap is not None and state in remap:
                    return
                domains = state.split(self.state_cls.separator, 1)
                if len(domains) > 1:
                    try:
                        self.get_state(domains[0])
                    except ValueError:
                        self.add_state(domains[0], on_enter=on_enter, on_exit=on_exit, ignore_invalid_triggers=ignore_invalid_triggers, **kwargs)
                    with self(domains[0]):
                        self.add_states(domains[1], on_enter=on_enter, on_exit=on_exit, ignore_invalid_triggers=ignore_invalid_triggers, **kwargs)
                else:
                    if state in self.states:
                        raise ValueError("State {0} cannot be added since it already exists.".format(state))
                    new_state = self._create_state(state, on_enter=on_enter, on_exit=on_exit,
                                                   ignore_invalid_triggers=ignore, **kwargs)
                    self.states[new_state.name] = new_state
                    self._init_state(new_state)
            elif isinstance(state, Enum):
                if self.state_cls.separator in state.name:
                    raise ValueError("State '{0}' contains '{1}' which is used as state name separator. "
                                     "Consider changing the NestedState.separator to avoid this issue."
                                     "".format(state.name, self.state_cls.separator))
                if remap is not None and state.name in remap:
                    return
                new_state = self._create_state(state, on_enter=on_enter, on_exit=on_exit,
                                               ignore_invalid_triggers=ignore, **kwargs)
                if state.name in self.states:
                    raise ValueError("State {0} cannot be added since it already exists.".format(state.name))
                self.states[new_state.name] = new_state
                self._init_state(new_state)
            elif isinstance(state, dict):
                if remap is not None and state['name'] in remap:
                    return
                state = state.copy()  # prevent messing with the initially passed dict
                remap = state.pop('remap', None)
                if 'ignore_invalid_triggers' not in state:
                    state['ignore_invalid_triggers'] = ignore

                # parallel: [states] is just a short handle for {children: [states], initial: [state_names]}
                state_parallel = state.pop('parallel', [])
                if state_parallel:
                    state_children = state_parallel
                    state['initial'] = [s['name'] if isinstance(s, dict)
                                        else s for s in state_children]
                else:
                    state_children = state.pop('children', state.pop('states', []))
                transitions = state.pop('transitions', [])
                new_state = self._create_state(**state)
                self.states[new_state.name] = new_state
                self._init_state(new_state)
                remapped_transitions = []
                with self(new_state.name):
                    self.add_states(state_children, remap=remap, **kwargs)
                    if remap is not None:
                        drop_event = []
                        for evt in self.events.values():
                            self.events[evt.name] = copy.copy(evt)
                        for trigger, event in self.events.items():
                            drop_source = []
                            event.transitions = copy.deepcopy(event.transitions)
                            for source_name, trans_source in event.transitions.items():
                                if source_name in remap:
                                    drop_source.append(source_name)
                                    continue
                                drop_trans = []
                                for trans in trans_source:
                                    if trans.dest in remap:
                                        conditions, unless = [], []
                                        for cond in trans.conditions:
                                            # split a list in two lists based on the accessors (cond.target) truth value
                                            (unless, conditions)[cond.target].append(cond.func)
                                        remapped_transitions.append({
                                            'trigger': trigger,
                                            'source': new_state.name + self.state_cls.separator + trans.source,
                                            'dest': remap[trans.dest],
                                            'conditions': conditions,
                                            'unless': unless,
                                            'prepare': trans.prepare,
                                            'before': trans.before,
                                            'after': trans.after})
                                        drop_trans.append(trans)
                                for t in drop_trans:
                                    trans_source.remove(t)
                                if not trans_source:
                                    drop_source.append(source_name)
                            for s in drop_source:
                                del event.transitions[s]
                            if not event.transitions:
                                drop_event.append(trigger)
                        for e in drop_event:
                            del self.events[e]
                    if transitions:
                        self.add_transitions(transitions)
                self.add_transitions(remapped_transitions)
            elif isinstance(state, NestedState):
                if state.name in self.states:
                    raise ValueError("State {0} cannot be added since it already exists.".format(state.name))
                self.states[state.name] = state
                self._init_state(state)
            elif isinstance(state, Machine):
                new_states = [s for s in state.states.values() if remap is None or s not in remap]
                self.add_states(new_states)
                for ev in state.events.values():
                    self.events[ev.name] = ev
                if self.scoped.initial is None:
                    self.scoped.initial = state.initial
            elif isinstance(state, State) and not isinstance(state, NestedState):
                raise ValueError("A passed state object must derive from NestedState! "
                                 "A default State object is not sufficient")
            else:
                raise ValueError("Cannot add state of type {0}. ".format(type(state).__name__))

    def add_transition(self, trigger, source, dest, conditions=None,
                       unless=None, before=None, after=None, prepare=None, **kwargs):
        if source != self.wildcard_all:
            source = [self.state_cls.separator.join(self._get_enum_path(s)) if isinstance(s, Enum) else s
                      for s in listify(source)]
        if dest != self.wildcard_same:
            dest = self.state_cls.separator.join(self._get_enum_path(dest)) if isinstance(dest, Enum) else dest
        _super(HierarchicalMachine, self).add_transition(trigger, source, dest, conditions,
                                                         unless, before, after, prepare, **kwargs)

    def get_global_name(self, state=None, join=True):
        domains = copy.copy(self.prefix_path)
        if state:
            state_name = state.name if hasattr(state, 'name') else state
            if state_name in self.states:
                domains.append(state_name)
            else:
                raise ValueError("State '{0}' not found in local states.".format(state))
        return self.state_cls.separator.join(domains) if join else domains

    def get_nested_state_names(self):
        ordered_states = []
        for state in self.states.values():
            ordered_states.append(self.get_global_name(state))
            with self(state.name):
                ordered_states.extend(self.get_nested_state_names())
        return ordered_states

    def get_nested_transitions(self, trigger="", src_path=None, dest_path=None):
        if src_path and dest_path:
            src = self.state_cls.separator.join(src_path)
            dest = self.state_cls.separator.join(dest_path)
            transitions = _super(HierarchicalMachine, self).get_transitions(trigger, src, dest)
            if len(src_path) > 1 and len(dest_path) > 1:
                with self(src_path[0]):
                    transitions.extend(self.get_nested_transitions(trigger, src_path[1:], dest_path[1:]))
        elif src_path:
            src = self.state_cls.separator.join(src_path)
            transitions = _super(HierarchicalMachine, self).get_transitions(trigger, src, "*")
            if len(src_path) > 1:
                with self(src_path[0]):
                    transitions.extend(self.get_nested_transitions(trigger, src_path[1:], None))
        elif dest_path:
            dest = self.state_cls.separator.join(dest_path)
            transitions = _super(HierarchicalMachine, self).get_transitions(trigger, "*", dest)
            if len(dest_path) > 1:
                for state_name in self.states:
                    with self(state_name):
                        transitions.extend(self.get_nested_transitions(trigger, None, dest_path[1:]))
        else:
            transitions = _super(HierarchicalMachine, self).get_transitions(trigger, "*", "*")
            for state_name in self.states:
                with self(state_name):
                    transitions.extend(self.get_nested_transitions(trigger, None, None))
        return transitions

    def get_nested_triggers(self, src_path=None):
        if src_path:
            triggers = _super(HierarchicalMachine, self).get_triggers(self.state_cls.separator.join(src_path))
            if len(src_path) > 1 and src_path[0] in self.states:
                with self(src_path[0]):
                    triggers.extend(self.get_nested_triggers(src_path[1:]))
        else:
            triggers = list(self.events.keys())
            for state_name in self.states:
                with self(state_name):
                    triggers.extend(self.get_nested_triggers())
        return triggers

    def get_state(self, state, hint=None):
        """ Return the State instance with the passed name. """
        if isinstance(state, Enum):
            state = self._get_enum_path(state)
        elif isinstance(state, string_types):
            state = state.split(self.state_cls.separator)
        if not hint:
            state = copy.copy(state)
            hint = copy.copy(state)
        if len(state) > 1:
            child = state.pop(0)
            try:
                with self(child):
                    return self.get_state(state, hint)
            except (KeyError, ValueError):
                try:
                    with self():
                        state = self
                        for elem in hint:
                            state = state.states[elem]
                        return state
                except KeyError:
                    raise ValueError("State '%s' is not a registered state." % self.state_cls.separator.join(hint))
        elif state[0] not in self.states:
            raise ValueError("State '%s' is not a registered state." % state)
        return self.states[state[0]]

    def get_states(self, states):
        res = []
        for state in states:
            if isinstance(state, list):
                res.append(self.get_states(state))
            else:
                res.append(self.get_state(state))
        return res

    def get_transitions(self, trigger="", source="*", dest="*", delegate=False):
        """ Return the transitions from the Machine.
        Args:
            trigger (str): Trigger name of the transition.
            source (str, State or Enum): Limits list to transitions from a certain state.
            dest (str, State or Enum): Limits list to transitions to a certain state.
            delegate (Optional[bool]): If True, consider delegations to parents of source
        """
        with self():
            source_path = [] if source == "*" \
                else source.split(self.state_cls.separator) if isinstance(source, string_types) \
                else self._get_enum_path(source) if isinstance(source, Enum) \
                else self._get_state_path(source)
            dest_path = [] if dest == "*" \
                else dest.split(self.state_cls.separator) if isinstance(dest, string_types) \
                else self._get_enum_path(dest) if isinstance(dest, Enum) \
                else self._get_state_path(dest)
            matches = self.get_nested_transitions(trigger, source_path, dest_path)
            # only consider delegations when source_path contains a nested state (len > 1)
            if delegate is False or len(source_path) < 2:
                return matches
            source_path.pop()
            while source_path:
                matches.extend(self.get_transitions(trigger,
                                                    source=self.state_cls.separator.join(source_path),
                                                    dest=dest))
                source_path.pop()
            return matches

    def get_triggers(self, *args):
        """ Extends transitions.core.Machine.get_triggers to also include parent state triggers. """
        triggers = []
        with self():
            for state in args:
                state_name = state.name if hasattr(state, 'name') else state
                state_path = state_name.split(self.state_cls.separator)
                if len(state_path) > 1:  # we only need to check substates when 'state_name' refers to a substate
                    with self(state_path[0]):
                        triggers.extend(self.get_nested_triggers(state_path[1:]))
                while state_path:  # check all valid transitions for parent states
                    triggers.extend(_super(HierarchicalMachine, self).get_triggers(self.state_cls.separator.join(state_path)))
                    state_path.pop()
        return triggers

    def has_trigger(self, trigger, state=None):
        """ Check whether an event/trigger is known to the machine
        Args:
            trigger (str): Event/trigger name
            state (optional[NestedState]): Limits the recursive search to this state and its children
        Returns:
            bool: True if event is known and False otherwise
        """

        state = state or self
        return trigger in state.events or any([self.has_trigger(trigger, sta) for sta in state.states.values()])

    def is_state(self, state_name, model, allow_substates=False):
        current_name = getattr(model, self.model_attribute)
        if allow_substates:
            if isinstance(current_name, Enum):
                current_name = self.state_cls.separator.join(self._get_enum_path(current_name))
            if isinstance(state_name, Enum):
                state_name = self.state_cls.separator.join(self._get_enum_path(state_name))
            return current_name.startswith(state_name)
        return current_name == state_name

    def on_enter(self, state_name, callback):
        """ Helper function to add callbacks to states in case a custom state separator is used.
        Args:
            state_name (str): Name of the state
            callback (str or callable): Function to be called. Strings will be resolved to model functions.
        """
        self.get_state(state_name).add_callback('enter', callback)

    def on_exit(self, state_name, callback):
        """ Helper function to add callbacks to states in case a custom state separator is used.
        Args:
            state_name (str): Name of the state
            callback (str or callable): Function to be called. Strings will be resolved to model functions.
        """
        self.get_state(state_name).add_callback('exit', callback)

    def set_state(self, states, model=None):
        """ Set the current state.
        Args:
            states (list of str or Enum or State): value of state(s) to be set
            model (optional[object]): targeted model; if not set, all models will be set to 'state'
        """
        values = [self._set_state(value) for value in listify(states)]
        models = self.models if model is None else listify(model)
        for mod in models:
            setattr(mod, self.model_attribute, values if len(values) > 1 else values[0])

    def to_state(self, model, state_name, *args, **kwargs):
        """ Helper function to add go to states in case a custom state separator is used.
        Args:
            model (class): The model that should be used.
            state_name (str): Name of the destination state.
        """

        current_state = getattr(model, self.model_attribute)
        if isinstance(current_state, list):
            raise MachineError("Cannot use 'to_state' from parallel state")

        event = EventData(self.get_state(current_state), Event('to', self), self,
                          model, args=args, kwargs=kwargs)
        if isinstance(current_state, Enum):
            event.source_path = self._get_enum_path(current_state)
            event.source_name = self.state_cls.separator.join(event.source_path)
        else:
            event.source_name = current_state
            event.source_path = current_state.split(self.state_cls.separator)
        self._create_transition(event.source_name, state_name).execute(event)

    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.
        """
        with self():
            res = self._trigger_event(_model, _trigger, None, *args, **kwargs)
        return self._check_event_result(res, _model, _trigger)

    def _add_model_to_state(self, state, model):
        name = self.get_global_name(state)
        if self.state_cls.separator == '_':
            value = state.value if isinstance(state.value, Enum) else name
            self._checked_assignment(model, 'is_%s' % name, partial(self.is_state, value, model))
            # Add dynamic method callbacks (enter/exit) if there are existing bound methods in the model
            # except if they are already mentioned in 'on_enter/exit' of the defined state
            for callback in self.state_cls.dynamic_methods:
                method = "{0}_{1}".format(callback, name)
                if hasattr(model, method) and inspect.ismethod(getattr(model, method)) and \
                        method not in getattr(state, callback):
                    state.add_callback(callback[3:], method)
        else:
            path = name.split(self.state_cls.separator)
            value = state.value if isinstance(state.value, Enum) else name
            trig_func = partial(self.is_state, value, model)
            if hasattr(model, 'is_' + path[0]):
                getattr(model, 'is_' + path[0]).add(trig_func, path[1:])
            else:
                self._checked_assignment(model, 'is_' + path[0], FunctionWrapper(trig_func, path[1:]))
        with self(state.name):
            for event in self.events.values():
                if not hasattr(model, event.name):
                    self._add_trigger_to_model(event.name, model)
            for state in self.states.values():
                self._add_model_to_state(state, model)

    def _add_trigger_to_model(self, trigger, model):
        trig_func = partial(self.trigger_event, model, trigger)
        # FunctionWrappers are only necessary if a custom separator is used
        if trigger.startswith('to_') and self.state_cls.separator != '_':
            path = trigger[3:].split(self.state_cls.separator)
            if hasattr(model, 'to_' + path[0]):
                # add path to existing function wrapper
                getattr(model, 'to_' + path[0]).add(trig_func, path[1:])
            else:
                # create a new function wrapper
                self._checked_assignment(model, 'to_' + path[0], FunctionWrapper(trig_func, path[1:]))
        else:
            self._checked_assignment(model, trigger, trig_func)
            self._checked_assignment(model, "may_%s" % trigger, partial(self._can_trigger, model, trigger))

    # converts a list of current states into a hierarchical state tree
    def _build_state_tree(self, model_states, separator, tree=None):
        tree = tree if tree is not None else OrderedDict()
        if isinstance(model_states, list):
            for state in model_states:
                _ = self._build_state_tree(state, separator, tree)
        else:
            tmp = tree
            if isinstance(model_states, (Enum, EnumMeta)):
                with self():
                    path = self._get_enum_path(model_states)
            else:
                path = model_states.split(separator)
            for elem in path:
                tmp = tmp.setdefault(elem.name if hasattr(elem, 'name') else elem, OrderedDict())
        return tree

    def _get_enum_path(self, enum_state, prefix=[]):
        if enum_state.name in self.states and self.states[enum_state.name].value == enum_state:
            return prefix + [enum_state.name]
        for name in self.states:
            with self(name):
                res = self._get_enum_path(enum_state, prefix=prefix + [name])
                if res:
                    return res
        return []

    def _get_state_path(self, state, prefix=[]):
        if state in self.states.values():
            return prefix + [state.name]
        for name in self.states:
            with self(name):
                res = self._get_state_path(state, prefix=prefix + [name])
                if res:
                    return res
        return []

    def _check_event_result(self, res, model, trigger):
        if res is None:
            state_names = getattr(model, self.model_attribute)
            msg = "%sCan't trigger event '%s' from state(s) %s!" % (self.name, trigger, state_names)
            for state_name in listify(state_names):
                state = self.get_state(state_name)
                ignore = state.ignore_invalid_triggers if state.ignore_invalid_triggers is not None \
                    else self.ignore_invalid_triggers
                if not ignore:
                    # determine whether a MachineError (valid event but invalid state) ...
                    if self.has_trigger(trigger):
                        raise MachineError(msg)
                    # or AttributeError (invalid event) is appropriate
                    else:
                        raise AttributeError("Do not know event named '%s'." % trigger)
            _LOGGER.warning(msg)
            res = False
        return res

    def _get_trigger(self, model, trigger_name, *args, **kwargs):
        """Convenience function added to the model to trigger events by name.
        Args:
            model (object): Model with assigned event trigger.
            trigger_name (str): Name of the trigger to be called.
            *args: Variable length argument list which is passed to the triggered event.
            **kwargs: Arbitrary keyword arguments which is passed to the triggered event.
        Returns:
            bool: True if a transitions has been conducted or the trigger event has been queued.
        """
        return self.trigger_event(model, trigger_name, *args, **kwargs)

    def _has_state(self, state, raise_error=False):
        """ This function
        Args:
            state (NestedState): state to be tested
            raise_error (bool): whether ValueError should be raised when the state
                                is not registered
       Returns:
            bool: Whether state is registered in the machine
        Raises:
            ValueError: When raise_error is True and state is not registered
        """
        found = _super(HierarchicalMachine, self)._has_state(state)
        if not found:
            for a_state in self.states:
                with self(a_state):
                    if self._has_state(state):
                        return True
        if not found and raise_error:
            msg = 'State %s has not been added to the machine' % (state.name if hasattr(state, 'name') else state)
            raise ValueError(msg)
        return found

    def _init_state(self, state):
        for model in self.models:
            self._add_model_to_state(state, model)
        if self.auto_transitions:
            state_name = self.get_global_name(state.name)
            parent = state_name.split(self.state_cls.separator, 1)
            with self():
                for a_state in self.get_nested_state_names():
                    if a_state == parent[0]:
                        self.add_transition('to_%s' % state_name, self.wildcard_all, state_name)
                    elif len(parent) == 1:
                        self.add_transition('to_%s' % a_state, state_name, a_state)
        with self(state.name):
            for substate in self.states.values():
                self._init_state(substate)

    def _recursive_initial(self, value):
        if isinstance(value, string_types):
            path = value.split(self.state_cls.separator, 1)
            if len(path) > 1:
                state_name, suffix = path
                # make sure the passed state has been created already
                _super(HierarchicalMachine, self.__class__).initial.fset(self, state_name)
                with self(state_name):
                    self.initial = suffix
                    self._initial = state_name + self.state_cls.separator + self._initial
            else:
                _super(HierarchicalMachine, self.__class__).initial.fset(self, value)
        elif isinstance(value, (list, tuple)):
            return [self._recursive_initial(v) for v in value]
        else:
            _super(HierarchicalMachine, self.__class__).initial.fset(self, value)
        return self._initial[0] if isinstance(self._initial, list) and len(self._initial) == 1 else self._initial

    def _resolve_initial(self, models, state_name_path, prefix=[]):
        if state_name_path:
            state_name = state_name_path.pop(0)
            with self(state_name):
                return self._resolve_initial(models, state_name_path, prefix=prefix + [state_name])
        if self.scoped.initial:
            entered_states = []
            for initial_state_name in listify(self.scoped.initial):
                with self(initial_state_name):
                    entered_states.append(self._resolve_initial(models, [], prefix=prefix + [self.scoped.name]))
            return entered_states if len(entered_states) > 1 else entered_states[0]
        return self.state_cls.separator.join(prefix)

    def _set_state(self, state_name):
        if isinstance(state_name, list):
            return [self._set_state(value) for value in state_name]
        else:
            a_state = self.get_state(state_name)
            return a_state.value if isinstance(a_state.value, Enum) else state_name

    def _trigger_event(self, _model, _trigger, _state_tree, *args, **kwargs):
        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 = self._trigger_event(_model, _trigger, value, *args, **kwargs)
                    if tmp is not None:
                        res[key] = tmp
            if res.get(key, False) is False and _trigger in self.events:
                tmp = self.events[_trigger].trigger(_model, self, *args, **kwargs)
                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())