"""
RAG 检索流水线

整合基础检索、重排序和 RAG-Fusion 功能。
"""

from enum import Enum
from typing import List, Optional, Dict, Any
from langchain_core.documents import Document
from langchain_core.language_models import BaseLanguageModel

from .retriever import (
    create_base_retriever,
    create_hybrid_retriever,
    create_qdrant_client,
)
from .reranker import CrossEncoderReranker
from .query_transform import MultiQueryTransformer
from rag_core import QDRANT_URL, QDRANT_API_KEY


class RAGLevel(Enum):
    """RAG 级别"""
    BASIC = "basic"  # 基础向量检索
    RERANK = "rerank"  # 基础检索 + 重排序
    FUSION = "fusion"  # RAG-Fusion（多路查询 + RRF）


class RAGPipeline:
    """RAG 检索流水线"""
    
    def __init__(
        self,
        embeddings,
        llm: Optional[BaseLanguageModel] = None,
        config: Optional[Dict[str, Any]] = None,
    ):
        """
        初始化 RAG 流水线
        
        Args:
            embeddings: 嵌入模型
            llm: 语言模型（用于 RAG-Fusion）
            config: 配置参数
        """
        self.embeddings = embeddings
        self.llm = llm
        self.config = config or {}
        
        self.collection_name = self.config.get("collection_name", "rag_documents")
        self.rag_level = self.config.get("rag_level", RAGLevel.RERANK.value)
        self.num_queries = self.config.get("num_queries", 3)
        self.rerank_top_n = self.config.get("rerank_top_n", 5)
        
        # 初始化基础检索器
        self.base_retriever = create_base_retriever(
            collection_name=self.collection_name,
            embeddings=self.embeddings,
            search_kwargs={"k": 20},  # 召回 20 条
        )
        
        # 初始化重排序器
        try:
            self.reranker = CrossEncoderReranker(top_n=self.rerank_top_n)
        except Exception as e:
            print(f"警告: 无法创建重排序器，将使用基础检索。错误: {e}")
            self.reranker = None
        
        # 根据 RAG 级别创建检索器
        self.retriever = self._create_retriever()
    
    def _create_retriever(self):
        """根据 RAG 级别创建检索器"""
        if self.rag_level == RAGLevel.BASIC.value:
            return self.base_retriever
        
        # 基础检索 + 重排序
        def rerank_retriever(query):
            documents = self.base_retriever.invoke(query)
            if self.reranker:
                return self.reranker.compress_documents(documents, query)
            else:
                return documents[:self.rerank_top_n]
        
        if self.rag_level == RAGLevel.RERANK.value:
            return SimpleRetriever(rerank_retriever)
        
        # RAG-Fusion
        if self.rag_level == RAGLevel.FUSION.value:
            if not self.llm:
                raise ValueError("RAG-Fusion 需要提供 llm 参数")
            
            # 创建多路查询检索器
            transformer = MultiQueryTransformer(
                llm=self.llm,
                num_queries=self.num_queries
            )
            multi_query_retriever = transformer.create_multi_query_retriever(
                base_retriever=SimpleRetriever(rerank_retriever)
            )
            
            return multi_query_retriever
        
        return SimpleRetriever(rerank_retriever)
    
    def retrieve(self, query: str) -> List[Document]:
        """
        执行检索
        
        Args:
            query: 查询字符串
        
        Returns:
            相关文档列表
        """
        return self.retriever.invoke(query)
    
    async def aretrieve(self, query: str) -> List[Document]:
        """
        异步执行检索
        
        Args:
            query: 查询字符串
        
        Returns:
            相关文档列表
        """
        return await self.retriever.ainvoke(query)
    
    def format_context(self, documents: List[Document]) -> str:
        """
        格式化上下文
        
        Args:
            documents: 文档列表
        
        Returns:
            格式化后的上下文字符串
        """
        if not documents:
            return ""
        
        context_parts = []
        for i, doc in enumerate(documents, 1):
            content = doc.page_content
            metadata = doc.metadata or {}
            source = metadata.get("source", "未知来源")
            
            part = f"【资料 {i}】\n"
            part += f"来源: {source}\n"
            part += f"内容: {content}\n"
            part += "---\n"
            context_parts.append(part)
        
        return "".join(context_parts)


class SimpleRetriever:
    """简单检索器包装类"""
    
    def __init__(self, retrieve_func):
        self.retrieve_func = retrieve_func
    
    def invoke(self, query):
        return self.retrieve_func(query)
    
    async def ainvoke(self, query):
        return self.retrieve_func(query)