"""实验进度 SSE（轮询 DB，轻量实现）。"""

from __future__ import annotations

import asyncio
import json

from fastapi import APIRouter, Header, Query
from fastapi.responses import StreamingResponse

from app.core.db import AsyncSessionLocal
from app.features.evaluation.admin_service import EvaluationAdminService
from app.features.evaluation.internal_auth import verify_internal_eval_key

router = APIRouter(tags=["internal-evaluation-stream"])


@router.get("/experiments/{experiment_id}/stream")
async def experiment_event_stream(
    experiment_id: str,
    key: str | None = Query(
        default=None,
        description="等同 X-Internal-Eval-Key，供 EventSource 使用",
    ),
    x_internal_eval_key: str | None = Header(default=None, alias="X-Internal-Eval-Key"),
):
    verify_internal_eval_key(
        header_value=x_internal_eval_key,
        query_value=key,
    )

    async def event_gen():
        while True:
            async with AsyncSessionLocal() as session:
                svc = EvaluationAdminService(session)
                payload = await svc.experiment_stream_snapshot(experiment_id)
                if payload is None:
                    yield f"data: {json.dumps({'error': 'not_found'})}\n\n"
                    break
                yield f"data: {json.dumps(payload, default=str)}\n\n"
                if payload.get("status") in ("completed", "failed"):
                    break
            await asyncio.sleep(1.0)

    return StreamingResponse(event_gen(), media_type="text/event-stream")