"""
嵌入模型服务模块

本模块提供统一的嵌入模型服务获取接口，支持自动降级：
1. 优先使用本地 llama.cpp 嵌入服务
2. 本地服务不可用时，自动降级到智谱 API 嵌入服务

主要功能：
- LocalLlamaCppEmbeddingProvider：本地 llama.cpp 嵌入服务提供者
- ZhipuEmbeddingProvider：智谱 API 嵌入服务提供者
- get_embedding_service()：获取嵌入服务的统一接口
"""

import logging
from typing import List
import httpx
from langchain_core.embeddings import Embeddings

from .base import (
    BaseServiceProvider,
    FallbackServiceChain,
    SingletonServiceManager
)
from ..config import (
    LLAMACPP_EMBEDDING_URL,
    LLAMACPP_API_KEY,
    ZHIPUAI_API_KEY,
    ZHIPU_EMBEDDING_MODEL,
    ZHIPU_API_BASE
)

logger = logging.getLogger(__name__)


class LocalLlamaCppEmbeddingProvider(BaseServiceProvider[Embeddings]):
    """
    本地 llama.cpp 嵌入服务提供者
    """
    
    def __init__(self, model: str = "Qwen3-Embedding-0.6B-Q8_0"):
        super().__init__("local_llamacpp_embedding")
        self._model = model
    
    def is_available(self) -> bool:
        """
        检查本地 llama.cpp 嵌入服务是否可用
        
        Returns:
            bool: 服务是否可用
        """
        if not LLAMACPP_EMBEDDING_URL:
            logger.warning("LLAMACPP_EMBEDDING_URL 未配置")
            return False
        
        try:
            # 尝试嵌入一个测试字符串
            embedder = LocalLlamaCppEmbedder(model=self._model)
            test_embedding = embedder.embed_query("test")
            logger.info(f"本地 llama.cpp 嵌入服务可用，维度: {len(test_embedding)}")
            return True
        except Exception as e:
            logger.warning(f"本地 llama.cpp 嵌入服务不可用: {e}")
            return False
    
    def get_service(self) -> Embeddings:
        """
        获取本地 llama.cpp 嵌入服务
        
        Returns:
            Embeddings: LangChain 兼容的嵌入实例
        """
        if self._service_instance is None:
            embedder = LocalLlamaCppEmbedder(model=self._model)
            self._service_instance = embedder.as_langchain_embeddings()
        return self._service_instance


class ZhipuEmbeddingProvider(BaseServiceProvider[Embeddings]):
    """
    智谱 API 嵌入服务提供者
    """
    
    def __init__(self, model: str | None = None):
        super().__init__("zhipu_embedding")
        self._model = model or ZHIPU_EMBEDDING_MODEL
    
    def is_available(self) -> bool:
        """
        检查智谱 API 嵌入服务是否可用
        
        Returns:
            bool: 服务是否可用
        """
        if not ZHIPUAI_API_KEY:
            logger.warning("ZHIPUAI_API_KEY 未配置")
            return False
        
        try:
            # 测试智谱 API 是否可用
            from zhipuai import ZhipuAI
            client = ZhipuAI(api_key=ZHIPUAI_API_KEY)
            response = client.embeddings.create(
                model=self._model,
                input=["test"]
            )
            logger.info(f"智谱嵌入服务可用，维度: {len(response.data[0].embedding)}")
            return True
        except ImportError:
            logger.warning("zhipuai 库未安装")
            return False
        except Exception as e:
            logger.warning(f"智谱嵌入服务不可用: {e}")
            return False
    
    def get_service(self) -> Embeddings:
        """
        获取智谱 API 嵌入服务
        
        Returns:
            Embeddings: LangChain 兼容的嵌入实例
        """
        if self._service_instance is None:
            from langchain_zhipu import ZhipuAIEmbeddings
            self._service_instance = ZhipuAIEmbeddings(
                model=self._model,
                api_key=ZHIPUAI_API_KEY
            )
        return self._service_instance


class LocalLlamaCppEmbedder:
    """
    通过 OpenAI 兼容 API 封装 llama.cpp 嵌入服务
    """
    
    def __init__(self, model: str = "Qwen3-Embedding-0.6B-Q8_0"):
        self.base_url = LLAMACPP_EMBEDDING_URL
        self.api_key = LLAMACPP_API_KEY
        self.model = model
    
    def as_langchain_embeddings(self) -> Embeddings:
        """创建 LangChain 兼容的嵌入实例"""
        return _LlamaCppLangchainAdapter(self)
    
    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        """嵌入一批文档"""
        return self._call_embedding_api(texts)
    
    def embed_query(self, text: str) -> List[float]:
        """嵌入单个查询"""
        return self._call_embedding_api([text])[0]
    
    def _call_embedding_api(self, texts: List[str]) -> List[List[float]]:
        """直接调用 llama.cpp 嵌入 API"""
        headers = {"Content-Type": "application/json"}
        if self.api_key:
            headers["Authorization"] = f"Bearer {self.api_key}"
        
        base = self.base_url.rstrip("/")
        if not base.endswith("/v1"):
            base = base + "/v1"
        
        payload = {
            "input": texts,
            "model": self.model,
        }
        
        with httpx.Client(timeout=120) as client:
            response = client.post(
                f"{base}/embeddings",
                headers=headers,
                json=payload,
            )
            response.raise_for_status()
            data = response.json()
            
            if isinstance(data, list):
                return [item["embedding"] for item in data]
            elif isinstance(data, dict) and "data" in data:
                return [item["embedding"] for item in sorted(data["data"], key=lambda x: x["index"])]
            else:
                raise ValueError(f"未知的嵌入 API 响应格式: {data}")


class _LlamaCppLangchainAdapter(Embeddings):
    """
    将 LlamaCppEmbedder 适配为 LangChain Embeddings 接口
    """
    
    def __init__(self, embedder: "LocalLlamaCppEmbedder"):
        self._embedder = embedder
    
    def embed_documents(self, texts: List[str]) -> List[List[float]]:
        return self._embedder.embed_documents(texts)
    
    def embed_query(self, text: str) -> List[float]:
        return self._embedder.embed_query(text)


def get_embedding_service() -> Embeddings:
    """
    获取嵌入服务（带自动降级）
    
    Returns:
        Embeddings: LangChain 兼容的嵌入实例
    """
    def _create_chain():
        primary = LocalLlamaCppEmbeddingProvider()
        fallback = ZhipuEmbeddingProvider()
        return FallbackServiceChain(primary, [fallback])
    
    chain = SingletonServiceManager.get_or_create("embedding_service_chain", _create_chain)
    return chain.get_available_service()