"""In-process revision notifications for SSE clients."""

from __future__ import annotations

import asyncio
import contextlib
from collections import defaultdict


class EventBroker:
    """Fan out room revisions; clients always reload the latest snapshot."""

    def __init__(self) -> None:
        """Initialize an empty subscription registry."""
        self._queues: dict[str, set[asyncio.Queue[int]]] = defaultdict(set)

    def subscribe(self, room_code: str) -> asyncio.Queue[int]:
        """Subscribe a bounded notification queue to a room."""
        queue: asyncio.Queue[int] = asyncio.Queue(maxsize=1)
        self._queues[room_code].add(queue)
        return queue

    def unsubscribe(self, room_code: str, queue: asyncio.Queue[int]) -> None:
        """Remove a room notification queue from the registry."""
        self._queues[room_code].discard(queue)
        if not self._queues[room_code]:
            self._queues.pop(room_code, None)

    def publish(self, room_code: str, revision: int) -> None:
        """Publish the newest room revision to every subscriber."""
        for queue in tuple(self._queues.get(room_code, ())):
            if queue.full():
                with contextlib.suppress(asyncio.QueueEmpty):
                    queue.get_nowait()
            queue.put_nowait(revision)