"""Simple async event bus for inter-module communication."""

from __future__ import annotations

import asyncio
from collections import defaultdict
from typing import Any, Callable, Coroutine, Dict, List

from loguru import logger


class EventBus:
    """Publish-subscribe event bus using asyncio."""

    def __init__(self):
        self._subscribers: Dict[str, List[Callable]] = defaultdict(list)

    def subscribe(self, event_type: str, handler: Callable[..., Coroutine]) -> None:
        """Register an async handler for an event type."""
        self._subscribers[event_type].append(handler)
        logger.debug("Subscribed to '{}': {}", event_type, handler.__name__)

    def unsubscribe(self, event_type: str, handler: Callable) -> None:
        """Remove a handler from an event type."""
        self._subscribers[event_type] = [
            h for h in self._subscribers[event_type] if h != handler
        ]

    async def publish(self, event_type: str, data: Any = None) -> None:
        """Publish an event, calling all registered handlers concurrently."""
        handlers = self._subscribers.get(event_type, [])
        if not handlers:
            return
        logger.debug("Publishing '{}' to {} handler(s)", event_type, len(handlers))
        await asyncio.gather(*(h(data) for h in handlers), return_exceptions=True)


# Module-level singleton
event_bus = EventBus()