"""全局一炁事件 SSE 端点（非 run-scoped）。

供前端 useGlobalEventStream hook 订阅全局广播事件：
- ``proactive.session`` —— 叩心枢新建的主动会话
- ``proactive.message`` —— 叩心枢追加到已有会话的消息
"""

from __future__ import annotations

import asyncio
from collections.abc import AsyncGenerator
from typing import Any

from fastapi import APIRouter, Request
from sse_starlette.sse import EventSourceResponse

from app.core.config import settings
from app.services.event_store import DbEventStore

router = APIRouter(prefix="/events", tags=["events"])


def _get_event_store(request: Request) -> DbEventStore:
    return request.app.state.event_store


@router.get("")
async def global_event_stream(
    request: Request,
) -> EventSourceResponse:
    """全局事件 SSE 流：通过 EventStore.subscribe_by_pattern 监听所有
    proactive.* 事件，推送给前端。"""
    if not settings.enable_sse:
        from app.core.errors import AppError

        raise AppError("invalid_request", "SSE 当前未启用。")

    event_store = _get_event_store(request)
    return EventSourceResponse(_event_generator(event_store))


async def _event_generator(
    event_store: DbEventStore,
) -> AsyncGenerator[dict[str, Any], None]:
    queue = event_store.subscribe_by_pattern("proactive.*")
    try:
        while True:
            try:
                event = await asyncio.wait_for(queue.get(), timeout=settings.sse_heartbeat_seconds)
                yield {
                    "id": event.id,
                    "event": event.type,
                    "data": event.model_dump_json(),
                }
            except TimeoutError:
                yield {
                    "event": "heartbeat",
                    "data": '{"type":"heartbeat"}',
                }
    except asyncio.CancelledError:
        pass
    finally:
        event_store.unsubscribe_by_pattern("proactive.*", queue)