# -*- coding: utf-8 -*- """ transitions.extensions.nesting ------------------------------ Adds the capability to work with nested states also known as hierarchical state machines. """ from copy import copy, deepcopy from functools import partial import logging from six import string_types from ..core import Machine, Transition, State, Event, listify, MachineError, EventData, Enum from .nesting import FunctionWrapper _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 class NestedState(State): """ A state which allows substates. Attributes: parent (NestedState): The parent of the current state. children (list): A list of child states of the current state. """ 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, parent=None, initial=None): if parent is not None and isinstance(name, Enum): raise AttributeError("NestedState does not support nested enumerations.") self._initial = initial self._parent = None self.parent = parent _super(NestedState, self).__init__(name=name, on_enter=on_enter, on_exit=on_exit, ignore_invalid_triggers=ignore_invalid_triggers) self.children = [] @property def parent(self): """ The parent state of this state. """ return self._parent @parent.setter def parent(self, value): if value is not None: self._parent = value self._parent.children.append(self) @property def initial(self): """ When this state is entered it will automatically enter the child with this name if not None. """ return self.name + self.separator + self._initial if self._initial else self._initial @initial.setter def initial(self, value): self._initial = value @property def level(self): """ Tracks how deeply nested this state is. This property is calculated from the state's parent (+1) or 0 when there is no parent. """ return self.parent.level + 1 if self.parent is not None else 0 @property def name(self): """ The computed name of this state. """ if self.parent: return self.parent.name + self.separator + _super(NestedState, self).name return _super(NestedState, self).name @name.setter def name(self, value): self._name = value @property def value(self): return self.name if isinstance(self._name, string_types) else _super(NestedState, self).value def is_substate_of(self, state_name): """Check whether this state is a substate of a state named `state_name` Args: state_name (str): Name of the parent state to be checked Returns: bool True when `state_name` is a parent of this state """ temp_state = self while not temp_state.value == state_name and temp_state.level > 0: temp_state = temp_state.parent return temp_state.value == state_name def exit_nested(self, event_data, target_state): """ Tracks child states to exit when the states is exited itself. This should not be triggered by the user but will be handled by the hierarchical machine. Args: event_data (EventData): Event related data. target_state (NestedState): The state to be entered. Returns: int level of the currently investigated (sub)state. """ if self == target_state: self.exit(event_data) return self.level elif self.level > target_state.level: self.exit(event_data) return self.parent.exit_nested(event_data, target_state) elif self.level <= target_state.level: tmp_state = target_state while self.level != tmp_state.level: tmp_state = tmp_state.parent tmp_self = self while tmp_self.level > 0 and tmp_state.parent.name != tmp_self.parent.name: tmp_self.exit(event_data) tmp_self = tmp_self.parent tmp_state = tmp_state.parent if tmp_self == tmp_state: return tmp_self.level + 1 tmp_self.exit(event_data) return tmp_self.level def enter_nested(self, event_data, level=None): """ Tracks parent states to be entered when the states is entered itself. This should not be triggered by the user but will be handled by the hierarchical machine. Args: event_data (EventData): Event related data. level (int): The level of the currently entered parent. """ if level is not None and level <= self.level: if level != self.level: self.parent.enter_nested(event_data, level) self.enter(event_data) # Prevent deep copying of callback lists since these include either references to callables 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(value)) else: setattr(result, key, deepcopy(value, memo)) return result class NestedTransition(Transition): """ A transition which handles entering and leaving nested states. Attributes: dest (NestedState): The resolved transition destination in respect to initial states of nested states. """ def execute(self, event_data): """ Extends transitions.core.transitions to handle nested states. """ if self.dest is None: return _super(NestedTransition, self).execute(event_data) dest_state = event_data.machine.get_state(self.dest) while dest_state.initial: dest_state = event_data.machine.get_state(dest_state.initial) self.dest = dest_state.name return _super(NestedTransition, self).execute(event_data) # The actual state change method 'execute' in Transition was restructured to allow overriding def _change_state(self, event_data): machine = event_data.machine model = event_data.model dest_state = machine.get_state(self.dest) source_state = machine.get_model_state(model) lvl = source_state.exit_nested(event_data, dest_state) event_data.machine.set_state(self.dest, model) event_data.update(dest_state) dest_state.enter_nested(event_data, lvl) # 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(value)) else: setattr(result, key, deepcopy(value, memo)) return result class NestedEvent(Event): """ An event type to work with nested states. """ def _trigger(self, model, *args, **kwargs): state = self.machine.get_model_state(model) while state.parent and state.name not in self.transitions: state = state.parent if state.name not in self.transitions: msg = "%sCan't trigger event %s from state %s!" % (self.machine.name, self.name, self.machine.get_model_state(model)) if self.machine.get_model_state(model).ignore_invalid_triggers: _LOGGER.warning(msg) else: raise MachineError(msg) event_data = EventData(state, self, self.machine, model, args=args, kwargs=kwargs) return self._process(event_data) class HierarchicalMachine(Machine): """ Extends transitions.core.Machine by capabilities to handle nested states. A hierarchical machine REQUIRES NestedStates (or any subclass of it) to operate. """ state_cls = NestedState transition_cls = NestedTransition event_cls = NestedEvent def __init__(self, *args, **kwargs): self._buffered_transitions = [] _super(HierarchicalMachine, self).__init__(*args, **kwargs) @Machine.initial.setter def initial(self, value): if isinstance(value, NestedState): if value.name not in self.states: self.add_state(value) else: assert self._has_state(value) state = value else: state_name = value.name if isinstance(value, Enum) else value if state_name not in self.states: self.add_state(state_name) state = self.get_state(state_name) if state.initial: self.initial = state.initial else: self._initial = state.name def add_model(self, model, initial=None): """ Extends transitions.core.Machine.add_model by applying a custom 'to' function to the added model. """ _super(HierarchicalMachine, self).add_model(model, initial=initial) models = listify(model) for mod in models: mod = self if mod == 'self' else mod # TODO: Remove 'mod != self' in 0.7.0 if hasattr(mod, 'to') and mod != self: _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) def is_state(self, state_name, model, allow_substates=False): """ Extends transitions.core.Machine.is_state with an additional parameter (allow_substates) to Args: state_name (str): Name of the checked state. model (class): The model to be investigated. allow_substates (bool): Whether substates should be allowed or not. Returns: bool Whether the passed model is in queried state (or a substate of it) or not. """ if not allow_substates: return getattr(model, self.model_attribute) == state_name return self.get_model_state(model).is_substate_of(state_name) def _traverse(self, states, on_enter=None, on_exit=None, ignore_invalid_triggers=None, parent=None, remap=None): """ Parses passed value to build a nested state structure recursively. Args: states (list, str, dict, or State): a list, a State instance, the name of a new state, or a dict with keywords to pass on to the State initializer. If a list, each element can be of any of the latter three types. 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. parent (NestedState or str): parent state for nested states. remap (dict): reassigns transitions named `key from nested machines to parent state `value`. Returns: list of new `NestedState` objects """ states = listify(states) new_states = [] ignore = ignore_invalid_triggers remap = {} if remap is None else remap parent = self.get_state(parent) if isinstance(parent, (string_types, Enum)) else parent if ignore is None: ignore = self.ignore_invalid_triggers for state in states: tmp_states = [] # other state representations are handled almost like in the base class but a parent parameter is added if isinstance(state, (string_types, Enum)): if state in remap: continue tmp_states.append(self._create_state(state, on_enter=on_enter, on_exit=on_exit, parent=parent, ignore_invalid_triggers=ignore)) elif isinstance(state, dict): if state['name'] in remap: continue # shallow copy the dictionary to alter/add some parameters state = copy(state) if 'ignore_invalid_triggers' not in state: state['ignore_invalid_triggers'] = ignore if 'parent' not in state: state['parent'] = parent try: state_children = state.pop('children') # throws KeyError when no children set state_remap = state.pop('remap', None) state_parent = self._create_state(**state) nested = self._traverse(state_children, parent=state_parent, remap=state_remap) tmp_states.append(state_parent) tmp_states.extend(nested) except KeyError: tmp_states.insert(0, self._create_state(**state)) elif isinstance(state, HierarchicalMachine): # set initial state of parent if it is None if parent.initial is None: parent.initial = state.initial # (deep) copy only states not mentioned in remap copied_states = [s for s in deepcopy(state.states).values() if s.name not in remap] # inner_states are the root states of the passed machine # which have be attached to the parent inner_states = [s for s in copied_states if s.level == 0] for inner in inner_states: inner.parent = parent tmp_states.extend(copied_states) for trigger, event in state.events.items(): if trigger.startswith('to_'): path = trigger[3:].split(self.state_cls.separator) # do not copy auto_transitions since they would not be valid anymore; # trigger and destination do not exist in the new environment if path[0] in remap: continue ppath = parent.name.split(self.state_cls.separator) path = ['to_' + ppath[0]] + ppath[1:] + path trigger = '.'.join(path) # (deep) copy transitions and # adjust all transition start and end points to new state names for transitions in deepcopy(event.transitions).values(): for transition in transitions: src = transition.source # transitions from remapped states will be filtered to prevent # unexpected behaviour in the parent machine if src in remap: continue dst = parent.name + self.state_cls.separator + transition.dest\ if transition.dest not in remap else remap[transition.dest] conditions, unless = [], [] for cond in transition.conditions: # split a list in two lists based on the accessors (cond.target) truth value (unless, conditions)[cond.target].append(cond.func) self._buffered_transitions.append({'trigger': trigger, 'source': parent.name + self.state_cls.separator + src, 'dest': dst, 'conditions': conditions, 'unless': unless, 'prepare': transition.prepare, 'before': transition.before, 'after': transition.after}) elif isinstance(state, NestedState): tmp_states.append(state) if state.children: tmp_states.extend(self._traverse(state.children, on_enter=on_enter, on_exit=on_exit, ignore_invalid_triggers=ignore_invalid_triggers, parent=state, remap=remap)) else: raise ValueError("%s is not an instance or subclass of NestedState " "required by HierarchicalMachine." % state) new_states.extend(tmp_states) duplicate_check = [] for new in new_states: if new.name in duplicate_check: # collect state names for the following error message state_names = [s.name for s in new_states] raise ValueError("State %s cannot be added since it is already in state list %s." % (new.name, state_names)) else: duplicate_check.append(new.name) return new_states def add_states(self, states, on_enter=None, on_exit=None, ignore_invalid_triggers=None, **kwargs): """ Extends transitions.core.Machine.add_states by calling traverse to parse possible substates first.""" # preprocess states to flatten the configuration and resolve nesting new_states = self._traverse(states, on_enter=on_enter, on_exit=on_exit, ignore_invalid_triggers=ignore_invalid_triggers, **kwargs) _super(HierarchicalMachine, self).add_states(new_states, on_enter=on_enter, on_exit=on_exit, ignore_invalid_triggers=ignore_invalid_triggers, **kwargs) while self._buffered_transitions: args = self._buffered_transitions.pop(0) self.add_transition(**args) def get_nested_state_names(self): """ Returns all states of the state machine. """ return self.states def get_triggers(self, *args): """ Extends transitions.core.Machine.get_triggers to also include parent state triggers. """ # add parents to state set states = [] for state_name in args: state = self.get_state(state_name) while state.parent: states.append(state.parent.name) state = state.parent states.extend(args) return _super(HierarchicalMachine, self).get_triggers(*states) def _add_trigger_to_model(self, trigger, model): # 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) trig_func = partial(self.events[trigger].trigger, model) 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 setattr(model, 'to_' + path[0], FunctionWrapper(trig_func, path[1:])) else: _super(HierarchicalMachine, self)._add_trigger_to_model(trigger, model) # pylint: disable=protected-access 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 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. """ event = EventData(self.get_model_state(model), Event('to', self), self, model, args=args, kwargs=kwargs) self._create_transition(getattr(model, self.model_attribute), state_name).execute(event)