129 lines
4.4 KiB
Python
129 lines
4.4 KiB
Python
from typing import Any, Callable, ClassVar, Dict, List, Optional, Set, Tuple, Type
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class StateGraph:
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"""
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Represents a graph of possible states and transitions to attempt on them.
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Does not support subclasses of existing graphs yet.
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"""
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states: ClassVar[Dict[str, "State"]]
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choices: ClassVar[List[Tuple[object, str]]]
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initial_state: ClassVar["State"]
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terminal_states: ClassVar[Set["State"]]
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def __init_subclass__(cls) -> None:
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# Collect state memebers
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cls.states = {}
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for name, value in cls.__dict__.items():
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if name in ["__module__", "__doc__", "states"]:
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pass
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elif name in ["initial_state", "terminal_states", "choices"]:
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raise ValueError(f"Cannot name a state {name} - this is reserved")
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elif isinstance(value, State):
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value._add_to_graph(cls, name)
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elif callable(value) or isinstance(value, classmethod):
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pass
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else:
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raise ValueError(
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f"Graph has item {name} of unallowed type {type(value)}"
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)
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# Check the graph layout
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terminal_states = set()
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initial_state = None
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for state in cls.states.values():
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# Check for multiple initial states
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if state.initial:
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if initial_state:
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raise ValueError(
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f"The graph has more than one initial state: {initial_state} and {state}"
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)
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initial_state = state
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# Collect terminal states
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if state.terminal:
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state.externally_progressed = True
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terminal_states.add(state)
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# Ensure they do NOT have a handler
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try:
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state.handler
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except AttributeError:
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pass
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else:
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raise ValueError(
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f"Terminal state '{state}' should not have a handler method ({state.handler_name})"
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)
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else:
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# Ensure non-terminal/manual states have a try interval and a handler
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if not state.externally_progressed:
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if not state.try_interval:
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raise ValueError(
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f"State '{state}' has no try_interval and is not terminal or manual"
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)
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try:
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state.handler
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except AttributeError:
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raise ValueError(
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f"State '{state}' does not have a handler method ({state.handler_name})"
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)
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if initial_state is None:
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raise ValueError("The graph has no initial state")
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cls.initial_state = initial_state
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cls.terminal_states = terminal_states
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# Generate choices
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cls.choices = [(name, name) for name in cls.states.keys()]
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class State:
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"""
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Represents an individual state
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"""
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def __init__(
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self,
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try_interval: Optional[float] = None,
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handler_name: Optional[str] = None,
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externally_progressed: bool = False,
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):
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self.try_interval = try_interval
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self.handler_name = handler_name
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self.externally_progressed = externally_progressed
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self.parents: Set["State"] = set()
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self.children: Set["State"] = set()
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def _add_to_graph(self, graph: Type[StateGraph], name: str):
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self.graph = graph
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self.name = name
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self.graph.states[name] = self
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if self.handler_name is None:
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self.handler_name = f"handle_{self.name}"
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def __repr__(self):
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return f"<State {self.name}>"
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def __eq__(self, other):
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if isinstance(other, State):
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return self is other
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return self.name == other
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def __hash__(self):
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return hash(id(self))
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def transitions_to(self, other: "State"):
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self.children.add(other)
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other.parents.add(other)
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@property
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def initial(self):
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return not self.parents
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@property
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def terminal(self):
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return not self.children
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@property
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def handler(self) -> Callable[[Any], Optional[str]]:
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# Retrieve it by name off the graph
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if self.handler_name is None:
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raise AttributeError("No handler defined")
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return getattr(self.graph, self.handler_name)
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