import os
import logging

def build_user_index(user_id: str):
    # 设置日志
    logger = logging.getLogger(__name__)
    logger.setLevel(logging.INFO)

    logger.info(f"开始为用户 {user_id} 构建索引...")
    
    doc_dir = os.path.join(USER_DOC_PATH, user_id)
    if not os.path.exists(doc_dir):
        raise FileNotFoundError(f"文档目录不存在: {doc_dir}")
    
    logger.info(f"发现文档目录: {doc_dir}")
    
    documents = SimpleDirectoryReader(doc_dir).load_data()
    logger.info(f"载入文档数量: {len(documents)}")
    
    embed_model = BGEEmbedding(model_name=settings.MODEL_NAME)
    logger.info(f"使用模型: {settings.MODEL_NAME}")
    
    service_context = ServiceContext.from_defaults(embed_model=embed_model, llm=None)

    faiss_index = faiss.IndexFlatL2(1024)
    vector_store = FaissVectorStore(faiss_index=faiss_index)

    persist_dir = os.path.join(USER_INDEX_PATH, user_id)
    os.makedirs(persist_dir, exist_ok=True)
    logger.info(f"索引保存路径: {persist_dir}")

    # 检查目录中是否存在 index_store.json 文件
    index_store_path = os.path.join(persist_dir, "index_store.json")
    if not os.path.exists(index_store_path):
        logger.info(f"未找到 index_store.json，准备创建")
    else:
        logger.info(f"已找到 index_store.json，跳过创建")

    storage_context = StorageContext.from_defaults(
        persist_dir=persist_dir,
        vector_store=vector_store,
    )

    try:
        # 构建索引
        index = VectorStoreIndex.from_documents(
            documents,
            service_context=service_context,
            storage_context=storage_context
        )
        index.persist(persist_dir=persist_dir)
        logger.info(f"索引已保存到 {persist_dir}")
    except Exception as e:
        logger.error(f"索引构建失败: {e}")
        raise HTTPException(status_code=500, detail="索引构建失败")