imonlinux
b62d07be7d
The EventHandler base class was modified to support the new decoupled __init__ pattern.
65 lines
2.3 KiB
Python
65 lines
2.3 KiB
Python
"""A simple synchronous publish/subscribe event bus."""
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import logging
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from typing import Any, Callable, Dict, List, Optional
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_LOGGER = logging.getLogger(__name__)
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class EventBus:
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"""A simple synchronous publish/subscribe event bus."""
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def __init__(self):
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self.topics: Dict[str, List[Callable[[Any], None]]] = {}
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def subscribe(self, topic: str, listener: Callable[[Any], None]) -> None:
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"""Subscribes a listener to a topic."""
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if topic not in self.topics:
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self.topics[topic] = []
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self.topics[topic].append(listener)
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_LOGGER.debug(f"Subscribed listener to topic '{topic}'")
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def publish(self, topic: str, data: Optional[Dict[str, Any]] = None) -> None:
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"""Publishes an event to all subscribed listeners."""
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if data is None:
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data = {}
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data['__topic'] = topic
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listeners = self.topics.get(topic, [])
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_LOGGER.debug(f"Publishing event to {len(listeners)} listeners on topic '{topic}'")
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for listener in listeners:
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try:
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listener(data)
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except Exception:
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_LOGGER.exception("Error in event listener for topic %s", topic)
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# -----------------------------------------------------------------------------
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# Client helpers for subscriptions
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# -----------------------------------------------------------------------------
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def subscribe(func: Callable) -> Callable:
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"""Decorator to mark a method for event bus subscription."""
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func._event_bus_subscribe = True
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return func
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class EventHandler:
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"""
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A base class for components that subscribe to events.
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Subclasses must call `self._subscribe_all_methods()` in their __init__.
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"""
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def __init__(self, event_bus: EventBus):
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self.event_bus = event_bus
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# Note: Subclasses must call self._subscribe_all_methods()
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# after their own __init__ is complete.
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def _subscribe_all_methods(self):
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"""Finds and subscribes all methods decorated with @subscribe."""
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for method_name in dir(self):
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method = getattr(self, method_name)
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if hasattr(method, '_event_bus_subscribe'):
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# The topic is the name of the method itself.
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self.event_bus.subscribe(method_name, method)
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