"""LLM 客户端（OpenAI 兼容），无 KEY 时全部调用降级为 None。

设计原则（批次 B 计划）：**统计引擎是主交付，LLM 只做话术增强**。
未配置 AI_API_KEY 时不报错、不阻塞、不改变任何统计结果，只把 `available()` 置 False，
调用方据此走纯统计文案。
"""

from __future__ import annotations

import json
import logging

from django.conf import settings

logger = logging.getLogger("dealerhub.ai")


def available() -> bool:
    """是否可用 LLM 增强（需 provider + key 都配置）。"""
    return bool(getattr(settings, "AI_PROVIDER", "") and getattr(settings, "AI_API_KEY", ""))


def chat(messages: list, *, max_tokens: int = 400, temperature: float = 0.3) -> str | None:
    """调用 OpenAI 兼容 chat/completions。失败或未配置一律返回 None（调用方降级）。"""
    if not available():
        return None

    base = (settings.AI_BASE_URL or "").rstrip("/")
    url = f"{base}/chat/completions"
    payload = {
        "model": settings.AI_MODEL,
        "messages": messages,
        "max_tokens": max_tokens,
        "temperature": temperature,
    }
    headers = {
        "Content-Type": "application/json",
        "Authorization": f"Bearer {settings.AI_API_KEY}",
    }

    try:
        import httpx

        with httpx.Client(timeout=getattr(settings, "AI_TIMEOUT", 20)) as client:
            resp = client.post(url, headers=headers, json=payload)
            resp.raise_for_status()
            data = resp.json()
        return (data.get("choices") or [{}])[0].get("message", {}).get("content")
    except Exception as exc:  # 网络/鉴权/格式任何问题都降级
        logger.warning("LLM call failed, falling back to statistics: %s", exc)
        return None


def collect_advice(prompt: str) -> str | None:
    """催收/经营建议：单轮问答，返回一句话建议或 None。"""
    return chat(
        [
            {"role": "system", "content": "你是经销商进销存系统的经营参谋，回答要短、要具体、可执行，不超过 60 字。"},
            {"role": "user", "content": prompt},
        ],
        max_tokens=160,
    )


def extract_json(prompt: str) -> dict | None:
    """要求 LLM 返回 JSON 并解析；失败返回 None。"""
    raw = chat(
        [
            {"role": "system", "content": "你只输出合法 JSON，不要任何解释文字、不要 markdown 代码块。"},
            {"role": "user", "content": prompt},
        ],
        max_tokens=600,
        temperature=0.1,
    )
    if not raw:
        return None
    text = raw.strip()
    if text.startswith("```"):
        # 容错：剥掉可能的代码围栏
        text = text.split("```")[1] if "```" in text[3:] else text[3:]
        text = text.lstrip("json").lstrip()
    try:
        return json.loads(text)
    except Exception as exc:
        logger.warning("LLM JSON parse failed: %s | raw=%s", exc, raw[:200])
        return None