"""
  重排客户端：调用外部 BGE 重排服务，并对 ES 分数与重排分数进行融合。
  
  流程：
  1. 从 ES hits 构造用于重排的文档文本列表
  2. POST 请求到重排服务 /rerank，获取每条文档的 relevance 分数
  3. 将 ES 分数（归一化）与重排分数线性融合，写回 hit["_score"] 并重排序
  """
  
  from typing import Dict, Any, List, Optional, Tuple

  import logging
  

  from providers import create_rerank_provider
  

  logger = logging.getLogger(__name__)
  
  # 默认融合权重：ES 归一化分数权重、重排分数权重（相加为 1）
  DEFAULT_WEIGHT_ES = 0.4
  DEFAULT_WEIGHT_AI = 0.6
  # 重排服务默认超时（文档较多时需更大，建议 config 中 timeout_sec 调大）
  DEFAULT_TIMEOUT_SEC = 15.0
  
  
  def build_docs_from_hits(
      es_hits: List[Dict[str, Any]],
      language: str = "zh",

      doc_template: str = "{title}",

  ) -> List[str]:
      """
      从 ES 命中结果构造重排服务所需的文档文本列表（与 hits 一一对应）。
  

      使用 doc_template 将文档字段组装为重排服务输入。
      支持占位符：{title} {brief} {vendor} {description} {category_path}

  
      Args:
          es_hits: ES 返回的 hits 列表，每项含 _source
          language: 语言代码，如 "zh"、"en"
  
      Returns:
          与 es_hits 等长的字符串列表，用于 POST /rerank 的 docs
      """
      lang = (language or "zh").strip().lower()
      if lang not in ("zh", "en"):
          lang = "zh"
  
      def pick_lang_text(obj: Any) -> str:
          if obj is None:
              return ""
          if isinstance(obj, dict):
              return str(obj.get(lang) or obj.get("zh") or obj.get("en") or "").strip()
          return str(obj).strip()
  

      class _SafeDict(dict):
          def __missing__(self, key: str) -> str:
              return ""
  

      docs: List[str] = []

      only_title = "{title}" == doc_template
      need_brief = "{brief}" in doc_template
      need_vendor = "{vendor}" in doc_template
      need_description = "{description}" in doc_template
      need_category_path = "{category_path}" in doc_template

      for hit in es_hits:
          src = hit.get("_source") or {}

          if only_title:
              docs.append(pick_lang_text(src.get("title")))
          else:
              values = _SafeDict(
                  title=pick_lang_text(src.get("title")),
                  brief=pick_lang_text(src.get("brief")) if need_brief else "",
                  vendor=pick_lang_text(src.get("vendor")) if need_vendor else "",
                  description=pick_lang_text(src.get("description")) if need_description else "",
                  category_path=pick_lang_text(src.get("category_path")) if need_category_path else "",
              )
              docs.append(str(doc_template).format_map(values))

      return docs
  
  
  def call_rerank_service(
      query: str,
      docs: List[str],

      timeout_sec: float = DEFAULT_TIMEOUT_SEC,

      top_n: Optional[int] = None,

  ) -> Tuple[Optional[List[float]], Optional[Dict[str, Any]]]:
      """
      调用重排服务 POST /rerank，返回分数列表与 meta。

      Provider 和 URL 从 services_config 读取。

      """
      if not docs:
          return [], {}
      try:

          client = create_rerank_provider()

          return client.rerank(query=query, docs=docs, timeout_sec=timeout_sec, top_n=top_n)

      except Exception as e:
          logger.warning("Rerank request failed: %s", e, exc_info=True)
          return None, None
  
  
  def fuse_scores_and_resort(
      es_hits: List[Dict[str, Any]],
      rerank_scores: List[float],
      weight_es: float = DEFAULT_WEIGHT_ES,
      weight_ai: float = DEFAULT_WEIGHT_AI,
  ) -> List[Dict[str, Any]]:
      """

      将 ES 分数与重排分数线性融合（不修改原始 _score），并按融合分数降序重排。

  
      对每条 hit 会写入：
      - _original_score: 原始 ES 分数

      - _rerank_score: 重排服务返回的分数

      - _fused_score: 融合分数

  
      Args:
          es_hits: ES hits 列表（会被原地修改）
          rerank_scores: 与 es_hits 等长的重排分数列表
          weight_es: ES 归一化分数权重
          weight_ai: 重排分数权重
  
      Returns:
          每条文档的融合调试信息列表，用于 debug_info
      """
      n = len(es_hits)
      if n == 0 or len(rerank_scores) != n:
          return []
  
      # 收集 ES 原始分数
      es_scores: List[float] = []
      for hit in es_hits:
          raw = hit.get("_score")
          try:
              es_scores.append(float(raw) if raw is not None else 0.0)
          except (TypeError, ValueError):
              es_scores.append(0.0)
  
      max_es = max(es_scores) if es_scores else 0.0
      fused_debug: List[Dict[str, Any]] = []
  
      for idx, hit in enumerate(es_hits):
          es_score = es_scores[idx]
          ai_score_raw = rerank_scores[idx]
          try:

              rerank_score = float(ai_score_raw)

          except (TypeError, ValueError):

              rerank_score = 0.0

  
          es_norm = (es_score / max_es) if max_es > 0 else 0.0

          fused = weight_es * es_norm + weight_ai * rerank_score

  
          hit["_original_score"] = hit.get("_score")

          hit["_rerank_score"] = rerank_score

          hit["_fused_score"] = fused

  
          fused_debug.append({
              "doc_id": hit.get("_id"),
              "es_score": es_score,
              "es_score_norm": es_norm,

              "rerank_score": rerank_score,

              "fused_score": fused,
          })
  
      # 按融合分数降序重排
      es_hits.sort(
          key=lambda h: h.get("_fused_score", h.get("_score", 0.0)),
          reverse=True,
      )
      return fused_debug
  
  
  def run_rerank(
      query: str,
      es_response: Dict[str, Any],
      language: str = "zh",

      timeout_sec: float = DEFAULT_TIMEOUT_SEC,
      weight_es: float = DEFAULT_WEIGHT_ES,
      weight_ai: float = DEFAULT_WEIGHT_AI,

      rerank_query_template: str = "{query}",
      rerank_doc_template: str = "{title}",

      top_n: Optional[int] = None,

  ) -> Tuple[Dict[str, Any], Optional[Dict[str, Any]], List[Dict[str, Any]]]:
      """
      完整重排流程：从 es_response 取 hits -> 构造 docs -> 调服务 -> 融合分数并重排 -> 更新 max_score。

      Provider 和 URL 从 services_config 读取。

      top_n 可选；若传入，会透传给 /rerank（供云后端按 page+size 做部分重排）。

      """

      hits = es_response.get("hits", {}).get("hits") or []
      if not hits:
          return es_response, None, []
  

      query_text = str(rerank_query_template).format_map({"query": query})
      docs = build_docs_from_hits(hits, language=language, doc_template=rerank_doc_template)

      scores, meta = call_rerank_service(
          query_text,
          docs,
          timeout_sec=timeout_sec,

          top_n=top_n,

      )

  
      if scores is None or len(scores) != len(hits):
          return es_response, None, []
  
      fused_debug = fuse_scores_and_resort(
          hits,
          scores,
          weight_es=weight_es,
          weight_ai=weight_ai,
      )
  
      # 更新 max_score 为融合后的最高分
      if hits:
          top = hits[0].get("_fused_score", hits[0].get("_score", 0.0)) or 0.0
          if "hits" in es_response:
              es_response["hits"]["max_score"] = top
  
      return es_response, meta, fused_debug