"""Rerank 服务：调用硅基流动 bge-reranker-v2-m3 对检索结果精排"""

import httpx
from config import SILICONFLOW_API_KEY, SILICONFLOW_BASE_URL, RERANK_MODEL


async def rerank(
    query: str,
    documents: list[str],
    top_n: int = 5,
) -> list[dict]:
    """对候选文档重新打分排序，返回 top_n 结果。

    每个结果包含:
        - index: 原始 documents 数组中的位置
        - score: 相关性分数 (0.0-1.0)
        - text: 文档原文
    """
    if not documents:
        return []

    async with httpx.AsyncClient(timeout=30) as client:
        resp = await client.post(
            f"{SILICONFLOW_BASE_URL}/rerank",
            headers={"Authorization": f"Bearer {SILICONFLOW_API_KEY}"},
            json={
                "model": RERANK_MODEL,
                "query": query,
                "documents": documents,
                "top_n": min(top_n, len(documents)),
                "return_documents": True,
                "max_chunks_per_doc": 1024,
            },
        )
        if resp.status_code != 200:
            raise RuntimeError(f"Rerank API error: {resp.status_code} {resp.text}")

        data = resp.json()
        return [
            {
                "index": r["index"],
                "score": r["relevance_score"],
                "text": r.get("document", {}).get("text", documents[r["index"]]),
            }
            for r in data["results"]
        ]