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129 lines
4.5 KiB
129 lines
4.5 KiB
from functools import partial
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from typing import TYPE_CHECKING
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from .callbacks import Callbacks
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from .callbacks import ConditionWrapper
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from .event import same_event_cond_builder
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from .events import Events
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from .exceptions import InvalidDefinition
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if TYPE_CHECKING:
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from .event_data import EventData
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class Transition:
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"""A transition holds reference to the source and target state.
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Args:
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source (State): The origin state of the transition.
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target (State): The target state of the transition.
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event (Optional[Union[str, List[str]]]): List of designators of events that trigger this
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transition. Can be either a list of strings, or a space-separated string list of event
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descriptors.
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internal (bool): Is the transition internal or external? Internal transitions
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don't execute the state entry/exit actions. Default ``False``.
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validators (Optional[Union[str, Callable, List[Callable]]]): The validation callbacks to
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be invoked before the transition is executed.
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cond (Optional[Union[str, Callable, List[Callable]]]): The condition callbacks to be
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invoked before the transition is executed that should evaluate to `True`.
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unless (Optional[Union[str, Callable, List[Callable]]]): The condition callbacks to be
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invoked if the `cond` is False before the transition is executed.
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on (Optional[Union[str, Callable, List[Callable]]]): The callbacks to be invoked
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when the transition is executed.
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before (Optional[Union[str, Callable, List[Callable]]]): The callbacks to be invoked
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before the transition is executed.
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after (Optional[Union[str, Callable, List[Callable]]]): The callbacks to be invoked
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after the transition is executed.
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"""
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def __init__(
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self,
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source,
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target,
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event=None,
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internal=False,
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validators=None,
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cond=None,
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unless=None,
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on=None,
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before=None,
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after=None,
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):
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self.source = source
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self.target = target
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self.internal = internal
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if internal and source is not target:
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raise InvalidDefinition("Internal transitions should be self-transitions.")
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self._events = Events().add(event)
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self.validators = Callbacks().add(validators)
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self.before = Callbacks().add(before)
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self.on = Callbacks().add(on)
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self.after = Callbacks().add(after)
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self.cond = (
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Callbacks(factory=ConditionWrapper)
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.add(cond)
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.add(unless, expected_value=False)
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)
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def __repr__(self):
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return (
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f"{type(self).__name__}({self.source!r}, {self.target!r}, event={self.event!r}, "
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f"internal={self.internal!r})"
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)
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def _upd_state_refs(self, machine):
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if self.source:
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self.source = machine.__dict__[self.source._storage]
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self.target = machine.__dict__[self.target._storage]
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def _setup(self, machine, resolver):
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self._upd_state_refs(machine)
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self.validators.setup(resolver)
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self.cond.setup(resolver)
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self.before.setup(resolver)
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self.on.setup(resolver)
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self.after.setup(resolver)
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def _add_observer(self, *resolvers):
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for r in resolvers:
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before = partial(self.before.add, resolver=r, suppress_errors=True)
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on = partial(self.on.add, resolver=r, suppress_errors=True)
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after = partial(self.after.add, resolver=r, suppress_errors=True)
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before("before_transition", prepend=True)
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on("on_transition", prepend=True)
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for event in self._events:
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before(f"before_{event}", cond=same_event_cond_builder(event))
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on(f"on_{event}", cond=same_event_cond_builder(event))
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after(f"after_{event}", cond=same_event_cond_builder(event))
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after("after_transition")
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def match(self, event):
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return self._events.match(event)
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@property
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def event(self):
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return str(self._events)
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@property
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def events(self):
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return self._events
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def add_event(self, value):
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self._events.add(value)
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def execute(self, event_data: "EventData"):
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args, kwargs = event_data.args, event_data.extended_kwargs
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self.validators.call(*args, **kwargs)
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if not self.cond.all(*args, **kwargs):
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return False
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result = event_data.machine._activate(event_data)
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event_data.result = result
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return True
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