"""
事件纲要生成进度广播 — 供 NDJSON 订阅端与后台流水线共享。
"""
from __future__ import annotations

import asyncio
from typing import Any, AsyncIterator, Dict, List

_subscribers: Dict[str, List[asyncio.Queue]] = {}


def emit(book_id: str, event: Dict[str, Any]) -> None:
    for q in list(_subscribers.get(book_id, [])):
        try:
            q.put_nowait(event)
        except asyncio.QueueFull:
            pass


async def subscribe(book_id: str) -> AsyncIterator[Dict[str, Any]]:
    q: asyncio.Queue = asyncio.Queue(maxsize=128)
    _subscribers.setdefault(book_id, []).append(q)
    try:
        while True:
            item = await q.get()
            yield item
            if item.get("type") in ("done", "error"):
                break
    finally:
        subs = _subscribers.get(book_id, [])
        if q in subs:
            subs.remove(q)
        if not subs:
            _subscribers.pop(book_id, None)