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