"""
Qdrant 向量检索器

提供基础向量检索、混合检索（Dense + BM25）功能。
"""

import os
from typing import List, Dict, Any, Optional
from langchain_qdrant import Qdrant
from langchain.embeddings.base import Embeddings
from langchain.retrievers import ContextualCompressionRetriever
from langchain.retrievers.document_compressors import DocumentCompressorPipeline
from langchain.retrievers import EnsembleRetriever
from qdrant_client import QdrantClient
from qdrant_client.http import models


def create_qdrant_client(
    url: Optional[str] = None,
    api_key: Optional[str] = None,
) -> QdrantClient:
    """
    创建 Qdrant 客户端
    
    Args:
        url: Qdrant 服务地址，默认从环境变量 QDRANT_URL 读取
        api_key: API 密钥，默认从环境变量 QDRANT_API_KEY 读取
    
    Returns:
        QdrantClient 实例
    """
    url = url or os.getenv("QDRANT_URL", "http://localhost:6333")
    api_key = api_key or os.getenv("QDRANT_API_KEY")
    
    client_args = {"url": url}
    if api_key:
        client_args["api_key"] = api_key
    
    return QdrantClient(**client_args)


def create_base_retriever(
    collection_name: str,
    embeddings: Embeddings,
    search_kwargs: Optional[Dict[str, Any]] = None,
    client: Optional[QdrantClient] = None,
) -> Qdrant:
    """
    创建基础向量检索器
    
    Args:
        collection_name: Qdrant 集合名称
        embeddings: 嵌入模型
        search_kwargs: 搜索参数，默认 {"k": 20}
        client: Qdrant 客户端，如果为 None 则自动创建
    
    Returns:
        Qdrant 检索器实例
    """
    if client is None:
        client = create_qdrant_client()
    
    search_kwargs = search_kwargs or {"k": 20}
    
    # 创建 Qdrant 检索器
    retriever = Qdrant.from_existing_collection(
        embedding=embeddings,
        collection_name=collection_name,
        client=client,
        content_payload_key="content",  # 假设存储的文本字段名为 "content"
        metadata_payload_key="metadata",  # 元数据字段名
    )
    
    return retriever.as_retriever(search_kwargs=search_kwargs)


def create_hybrid_retriever(
    collection_name: str,
    embeddings: Embeddings,
    dense_k: int = 10,
    sparse_k: int = 10,
    client: Optional[QdrantClient] = None,
) -> ContextualCompressionRetriever:
    """
    创建混合检索器（Dense Vector + BM25）
    
    Args:
        collection_name: Qdrant 集合名称
        embeddings: 嵌入模型
        dense_k: 向量检索返回数量
        sparse_k: BM25 检索返回数量
        client: Qdrant 客户端
    
    Returns:
        混合检索器
    """
    if client is None:
        client = create_qdrant_client()
    
    # 基础检索器（Qdrant 支持混合检索）
    base_retriever = Qdrant.from_existing_collection(
        embedding=embeddings,
        collection_name=collection_name,
        client=client,
        content_payload_key="content",
        metadata_payload_key="metadata",
    )
    
    # 配置混合检索参数
    search_kwargs = {
        "k": dense_k + sparse_k,  # 总返回数量
        "score_threshold": 0.3,   # 相似度阈值
    }
    
    return base_retriever.as_retriever(search_kwargs=search_kwargs)


def create_ensemble_retriever(
    retrievers: List[Any],
    weights: Optional[List[float]] = None,
    c: int = 60,
) -> EnsembleRetriever:
    """
    创建集成检索器，支持倒数排名融合 (RRF)
    
    Args:
        retrievers: 检索器列表
        weights: 检索器权重
        c: RRF 常数（通常为60）
    
    Returns:
        集成检索器
    """
    if weights is None:
        weights = [1.0 / len(retrievers)] * len(retrievers)
    
    ensemble = EnsembleRetriever(
        retrievers=retrievers,
        weights=weights,
        c=c,
        search_type="rrf",  # 使用倒数排名融合
    )
    
    return ensemble