"""In-process fan-out of workflow events to connected SSE clients.

The durable log in ``workflow_run_events`` is the source of truth; this hub only
shortens latency for the tail. Slow consumers lose the *oldest* queued frame
rather than blocking the executor, and the SSE endpoint reconciles any gap from
the database using the ``seq`` cursor.
"""

from __future__ import annotations

import asyncio
import logging
from collections import defaultdict
from collections.abc import Mapping
from typing import Any

logger = logging.getLogger(__name__)


class WorkflowLiveHub:
    def __init__(self, *, queue_size: int = 512) -> None:
        self._subscribers: dict[str, set[asyncio.Queue[dict[str, Any]]]] = defaultdict(set)
        self._queue_size = queue_size

    def subscribe(self, run_id: str) -> asyncio.Queue[dict[str, Any]]:
        queue: asyncio.Queue[dict[str, Any]] = asyncio.Queue(maxsize=self._queue_size)
        self._subscribers[run_id].add(queue)
        return queue

    def unsubscribe(self, run_id: str, queue: asyncio.Queue[dict[str, Any]]) -> None:
        subscribers = self._subscribers.get(run_id)
        if not subscribers:
            return
        subscribers.discard(queue)
        if not subscribers:
            self._subscribers.pop(run_id, None)

    def subscriber_count(self, run_id: str) -> int:
        return len(self._subscribers.get(run_id) or ())

    async def publish(self, event: Mapping[str, Any]) -> None:
        run_id = str(event.get("runId") or "")
        subscribers = self._subscribers.get(run_id)
        if not run_id or not subscribers:
            return
        payload = dict(event)
        for queue in list(subscribers):
            if queue.full():
                try:
                    queue.get_nowait()
                except asyncio.QueueEmpty:  # pragma: no cover - race with a reader
                    pass
            try:
                queue.put_nowait(payload)
            except asyncio.QueueFull:  # pragma: no cover - race with a reader
                logger.debug("workflow live queue still full for run %s", run_id)


__all__ = ["WorkflowLiveHub"]