import asyncio
import json
from typing import AsyncGenerator


class EventBroadcaster:
    def __init__(self):
        self._queues: set[asyncio.Queue] = set()

    async def subscribe(self) -> AsyncGenerator[str, None]:
        queue: asyncio.Queue[str] = asyncio.Queue(maxsize=32)
        self._queues.add(queue)
        try:
            while True:
                try:
                    msg = await asyncio.wait_for(queue.get(), timeout=25)
                    yield msg
                except asyncio.TimeoutError:
                    yield ": keepalive\n\n"
        except asyncio.CancelledError:
            pass
        finally:
            self._queues.discard(queue)

    def broadcast(self, event_type: str, data: dict | None = None) -> None:
        if not self._queues:
            return
        msg = f"event: {event_type}\ndata: {json.dumps(data or {})}\n\n"
        for queue in list(self._queues):
            try:
                queue.put_nowait(msg)
            except asyncio.QueueFull:
                pass


broadcaster = EventBroadcaster()