"""LLM 客户端抽象层

提供统一的 `generate(prompt, json_mode)` 接口，底层实现可切换：
- OllamaLLMClient：走 Ollama HTTP /api/generate（本地或远程 Ollama 服务）
- OpenAICompatibleLLMClient：走 OpenAI 兼容 /v1/chat/completions（OpenAI / DeepSeek / 智谱 / Qwen API 等）

工厂 `create_llm_client(purpose)` 根据 runtime_settings 选择实现与参数。
所有客户端共享同一接口，业务侧无需感知底层协议差异。
"""

from __future__ import annotations

from typing import Literal, Protocol, runtime_checkable

import httpx
import structlog

from app.config import settings
from app.core.runtime_settings import LlmProviderConfig, get_runtime_settings
from app.services.ollama import OllamaClient

logger = structlog.get_logger()

LlmPurpose = Literal["summarize", "query", "classify"]


@runtime_checkable
class LLMClient(Protocol):
    """LLM 客户端统一接口"""

    async def generate(self, prompt: str, json_mode: bool = False) -> str:
        """生成文本

        Args:
            prompt: 输入提示词
            json_mode: True 时约束输出为 JSON（不支持时降级为普通生成）

        Returns:
            生成的文本内容
        """
        ...

    async def is_available(self) -> bool:
        """检查服务是否可用"""
        ...


class OllamaLLMClient:
    """Ollama HTTP API 客户端（包装现有 OllamaClient，便于统一接口）"""

    def __init__(self, base_url: str, model: str, timeout: float = 120.0) -> None:
        self._inner = OllamaClient(base_url=base_url, model=model, timeout=timeout)

    async def generate(self, prompt: str, json_mode: bool = False) -> str:
        return await self._inner.generate(prompt, json_mode=json_mode)

    async def is_available(self) -> bool:
        return await self._inner.is_available()


class OpenAICompatibleLLMClient:
    """OpenAI 兼容 chat/completions 客户端

    适用于 OpenAI 官方 API、DeepSeek、智谱 ChatGLM、Qwen DashScope、Moonshot 等
    所有兼容 OpenAI /v1/chat/completions 协议的服务。
    """

    def __init__(self, base_url: str, api_key: str, model: str, timeout: float = 120.0, temperature: float = 0.3) -> None:
        self.base_url = base_url.rstrip("/")
        self.api_key = api_key
        self.model = model
        self.timeout = timeout
        self.temperature = temperature

    async def generate(self, prompt: str, json_mode: bool = False) -> str:
        url = f"{self.base_url}/chat/completions"
        payload: dict = {
            "model": self.model,
            "messages": [{"role": "user", "content": prompt}],
            "temperature": self.temperature,
            "stream": False,
        }
        if json_mode:
            payload["response_format"] = {"type": "json_object"}

        headers = {
            "Authorization": f"Bearer {self.api_key}",
            "Content-Type": "application/json",
        }
        async with httpx.AsyncClient(timeout=self.timeout) as client:
            resp = await client.post(url, json=payload, headers=headers)
            resp.raise_for_status()
            data = resp.json()

        # OpenAI 标准响应结构：choices[0].message.content
        choices = data.get("choices") or []
        if not choices:
            logger.warning("OpenAI 兼容响应无 choices", model=self.model, raw_keys=list(data.keys()))
            return ""
        message = choices[0].get("message") or {}
        content = message.get("content") or ""
        logger.debug("OpenAI 兼容生成完成", model=self.model, output_length=len(content))
        return content

    async def is_available(self) -> bool:
        """简单探测：调 /models 列表接口（多数 OpenAI 兼容服务支持）"""
        try:
            async with httpx.AsyncClient(timeout=5.0) as client:
                resp = await client.get(
                    f"{self.base_url}/models",
                    headers={"Authorization": f"Bearer {self.api_key}"},
                )
                return resp.status_code == 200
        except httpx.HTTPError:
            return False


# ---------------------------------------------------------------------------- #
# 工厂
# ---------------------------------------------------------------------------- #

# 进程级客户端缓存（避免每请求新建 httpx client）
_client_cache: dict[str, LLMClient] = {}


def _resolve_provider_config(purpose: LlmPurpose) -> LlmProviderConfig:
    """从 runtime_settings 取指定用途的 LLM 配置"""
    rt = get_runtime_settings()
    return getattr(rt.models, purpose)


def _build_client(purpose: LlmPurpose) -> LLMClient:
    """按 runtime_settings 构造 LLM 客户端"""
    cfg = _resolve_provider_config(purpose)

    if cfg.provider == "ollama":
        base_url = cfg.base_url or settings.ollama_base_url
        model = cfg.model or settings.ollama_model
        return OllamaLLMClient(base_url=base_url, model=model, timeout=cfg.timeout)

    if cfg.provider == "openai_compatible":
        base_url = cfg.base_url or settings.openai_base_url
        api_key = cfg.api_key or settings.openai_api_key
        # openai_compatible 默认模型：若 cfg.model 为空，退化到 OpenAI 通用 chat 模型
        model = cfg.model or "gpt-4o-mini"
        if not api_key:
            logger.warning("OpenAI 兼容 provider 缺少 api_key，调用大概率会失败", purpose=purpose)
        return OpenAICompatibleLLMClient(
            base_url=base_url, api_key=api_key, model=model, timeout=cfg.timeout, temperature=cfg.temperature
        )

    raise ValueError(f"未知 LLM provider: {cfg.provider}")


def create_llm_client(purpose: LlmPurpose, *, use_cache: bool = True) -> LLMClient:
    """创建指定用途的 LLM 客户端

    Args:
        purpose: 用途（summarize / query / classify）
        use_cache: True 时复用进程级客户端单例（默认）；False 每次新建（测试用）

    Returns:
        LLMClient 实例
    """
    if not use_cache:
        return _build_client(purpose)

    cache_key = f"{purpose}"
    if cache_key not in _client_cache:
        _client_cache[cache_key] = _build_client(purpose)
    return _client_cache[cache_key]


def invalidate_llm_client_cache(purpose: LlmPurpose | None = None) -> None:
    """清除客户端缓存（runtime_settings 更新后调用，确保后续读取新配置）"""
    if purpose is None:
        _client_cache.clear()
    else:
        _client_cache.pop(purpose, None)