refactor(bailian_rerank): 修复误删除并优化top_n参数处理

- 移除不合理的知识库配置读取逻辑
- 添加os模块导入（用于读取环境变量）
- 抽取辅助函数：_build_payload()、_parse_results()、_log_usage()
- 添加自定义异常类：BailianRerankError、BailianAPIError、BailianNetworkError
- 使用.get()安全访问API响应字段，避免KeyError
- 使用raise ... from e保持异常链

astrbot/core/provider/sources/bailian_rerank_source.py

@@ -1,3 +1,5 @@
+import os
+
 import aiohttp
 
 from astrbot import logger
@@ -7,6 +9,24 @@ from ..provider import RerankProvider
 from ..register import register_provider_adapter
 
 
+class BailianRerankError(Exception):
+    """百炼重排序服务异常基类"""
+
+    pass
+
+
+class BailianAPIError(BailianRerankError):
+    """百炼API返回错误"""
+
+    pass
+
+
+class BailianNetworkError(BailianRerankError):
+    """百炼网络请求错误"""
+
+    pass
+
+
 @register_provider_adapter(
     "bailian_rerank", "阿里云百炼文本排序适配器", provider_type=ProviderType.RERANK
 )
@@ -19,7 +39,9 @@ class BailianRerankProvider(RerankProvider):
         self.provider_settings = provider_settings
 
         # API配置
-        self.api_key = provider_config.get("rerank_api_key", "")
+        self.api_key = provider_config.get("rerank_api_key") or os.getenv(
+            "DASHSCOPE_API_KEY", ""
+        )
         if not self.api_key:
             raise ValueError("阿里云百炼 API Key 不能为空。")
 
@@ -48,6 +70,96 @@ class BailianRerankProvider(RerankProvider):
 
         logger.info(f"AstrBot 百炼 Rerank 初始化完成。模型: {self.model}")
 
+    def _build_payload(
+        self, query: str, documents: list[str], top_n: int | None
+    ) -> dict:
+        """构建请求载荷
+
+        Args:
+            query: 查询文本
+            documents: 文档列表
+            top_n: 返回前N个结果，如果为None则返回所有结果
+
+        Returns:
+            请求载荷字典
+        """
+        base = {"model": self.model, "input": {"query": query, "documents": documents}}
+
+        params = {
+            k: v
+            for k, v in [
+                ("top_n", top_n if top_n is not None and top_n > 0 else None),
+                ("return_documents", True if self.return_documents else None),
+                (
+                    "instruct",
+                    self.instruct
+                    if self.instruct and self.model == "qwen3-rerank"
+                    else None,
+                ),
+            ]
+            if v is not None
+        }
+
+        if params:
+            base["parameters"] = params
+
+        return base
+
+    def _parse_results(self, data: dict) -> list[RerankResult]:
+        """解析API响应结果
+
+        Args:
+            data: API响应数据
+
+        Returns:
+            重排序结果列表
+
+        Raises:
+            BailianAPIError: API返回错误
+            KeyError: 结果缺少必要字段
+        """
+        # 检查响应状态
+        if data.get("code", "200") != "200":
+            raise BailianAPIError(
+                f"百炼 API 错误: {data.get('code')} – {data.get('message', '')}"
+            )
+
+        results = data.get("output", {}).get("results", [])
+        if not results:
+            logger.warning(f"百炼 Rerank 返回空结果: {data}")
+            return []
+
+        # 转换为RerankResult对象，使用.get()避免KeyError
+        rerank_results = []
+        for idx, result in enumerate(results):
+            try:
+                index = result.get("index", idx)
+                relevance_score = result.get("relevance_score", 0.0)
+
+                if relevance_score is None:
+                    logger.warning(f"结果 {idx} 缺少 relevance_score，使用默认值 0.0")
+                    relevance_score = 0.0
+
+                rerank_result = RerankResult(
+                    index=index, relevance_score=relevance_score
+                )
+                rerank_results.append(rerank_result)
+            except Exception as e:
+                logger.warning(f"解析结果 {idx} 时出错: {e}, result={result}")
+                continue
+
+        return rerank_results
+
+    def _log_usage(self, data: dict) -> None:
+        """记录使用量信息
+
+        Args:
+            data: API响应数据
+        """
+        tokens = data.get("usage", {}).get("total_tokens", 0)
+        if tokens > 0:
+            logger.debug(f"百炼 Rerank 消耗 Token: {tokens}")
+
     async def rerank(
         self,
         query: str,
@@ -60,7 +172,7 @@ class BailianRerankProvider(RerankProvider):
         Args:
             query: 查询文本
             documents: 待排序的文档列表
-            top_n: 返回前N个结果，如果为None则返回所有重排序结果
+            top_n: 返回前N个结果，如果为None则使用配置中的默认值
 
         Returns:
             重排序结果列表
@@ -81,23 +193,8 @@ class BailianRerankProvider(RerankProvider):
             documents = documents[:500]
 
         try:
-            # 构建请求载荷
-            payload = {
-                "model": self.model,
-                "input": {"query": query, "documents": documents},
-            }
-
-            # 添加可选参数
-            parameters = {}
-            if top_n is not None and top_n > 0:
-                parameters["top_n"] = top_n
-            if self.return_documents:
-                parameters["return_documents"] = True
-            if self.instruct and self.model == "qwen3-rerank":
-                parameters["instruct"] = self.instruct
-
-            if parameters:
-                payload["parameters"] = parameters
+            # 构建请求载荷，如果top_n为None则返回所有重排序结果
+            payload = self._build_payload(query, documents, top_n)
 
             logger.debug(
                 f"百炼 Rerank 请求: query='{query[:50]}...', 文档数量={len(documents)}"
@@ -108,48 +205,24 @@ class BailianRerankProvider(RerankProvider):
                 response.raise_for_status()
                 response_data = await response.json()
 
-                # 检查响应状态
-                if "code" in response_data and response_data["code"] != "200":
-                    error_msg = response_data.get("message", "未知错误")
-                    api_error_msg = (
-                        f"百炼 API 返回错误: {response_data['code']} - {error_msg}"
-                    )
-                    raise RuntimeError(api_error_msg)
+                # 解析结果并记录使用量
+                results = self._parse_results(response_data)
+                self._log_usage(response_data)
 
-                # 解析结果
-                output = response_data.get("output", {})
-                results = output.get("results", [])
+                logger.debug(f"百炼 Rerank 成功返回 {len(results)} 个结果")
 
-                if not results:
-                    logger.warning(f"百炼 Rerank 返回空结果: {response_data}")
-                    return []
-
-                # 转换为RerankResult对象
-                rerank_results = []
-                for result in results:
-                    rerank_result = RerankResult(
-                        index=result["index"], relevance_score=result["relevance_score"]
-                    )
-                    rerank_results.append(rerank_result)
-
-                logger.debug(f"百炼 Rerank 成功返回 {len(rerank_results)} 个结果")
-
-                # 记录使用量信息
-                usage = response_data.get("usage", {})
-                total_tokens = usage.get("total_tokens", 0)
-                if total_tokens > 0:
-                    logger.debug(f"百炼 Rerank 消耗 Token 数量: {total_tokens}")
-
-                return rerank_results
+                return results
 
         except aiohttp.ClientError as e:
             error_msg = f"网络请求失败: {e}"
             logger.error(f"百炼 Rerank 网络请求失败: {e}")
-            raise RuntimeError(error_msg) from e
+            raise BailianNetworkError(error_msg) from e
+        except BailianRerankError:
+            raise
         except Exception as e:
             error_msg = f"重排序失败: {e}"
             logger.error(f"百炼 Rerank 处理失败: {e}")
-            raise RuntimeError(error_msg) from e
+            raise BailianRerankError(error_msg) from e
 
     async def terminate(self) -> None:
         """关闭HTTP客户端会话."""