"""
LLM-based translation backend (DashScope-compatible OpenAI API).

Failure semantics are strict:
- success: translated string
- failure: None
"""

from __future__ import annotations

import logging
import os
import time
from typing import Optional

from openai import OpenAI

from config.env_config import DASHSCOPE_API_KEY
from config.services_config import get_translation_config
from config.translate_prompts import TRANSLATION_PROMPTS, SOURCE_LANG_CODE_MAP


logger = logging.getLogger(__name__)


DEFAULT_QWEN_BASE_URL = "https://dashscope-us.aliyuncs.com/compatible-mode/v1"
DEFAULT_LLM_MODEL = "qwen-flash"


def _build_prompt(
    text: str,
    *,
    source_lang: Optional[str],
    target_lang: str,
    scene: Optional[str],
) -> str:
    """
    从 config.translate_prompts.TRANSLATION_PROMPTS 中构建提示词。

    要求：模板必须包含 {source_lang}（{src_lang_code}）{target_lang}（{tgt_lang_code}）。
    这里统一使用 code 作为占位的 lang 与 label，外部接口仍然只传语言 code。
    """
    tgt = (target_lang or "").lower() or "en"
    src = (source_lang or "auto").lower()

    # 将业务上下文 scene 映射为模板分组名
    normalized_scene = (scene or "").strip() or "general"
    # 如果出现历史词，则报错，用于发现错误
    if normalized_scene in {"query", "ecommerce_search", "ecommerce_search_query"}:
        group_key = "ecommerce_search_query"
    elif normalized_scene in {"product_title", "sku_name"}:
        group_key = "sku_name"
    else:
        group_key = normalized_scene
    group = TRANSLATION_PROMPTS.get(group_key) or TRANSLATION_PROMPTS["general"]

    # 先按目标语言 code 取模板，取不到回退到英文
    template = group.get(tgt) or group.get("en")
    if not template:
        # 理论上不会发生，兜底一个简单模板
        template = (
            "You are a professional {source_lang} ({src_lang_code}) to "
            "{target_lang} ({tgt_lang_code}) translator, output only the translation: {text}"
        )

    # 目前不额外维护语言名称映射，直接使用 code 作为 label
    source_lang_label = SOURCE_LANG_CODE_MAP.get(src, src)
    target_lang_label = SOURCE_LANG_CODE_MAP.get(tgt, tgt)

    return template.format(
        source_lang=source_lang_label,
        src_lang_code=src,
        target_lang=target_lang_label,
        tgt_lang_code=tgt,
        text=text,
    )


class LLMTranslatorProvider:
    def __init__(
        self,
        *,
        model: Optional[str] = None,
        timeout_sec: float = 30.0,
        base_url: Optional[str] = None,
    ) -> None:
        cfg = get_translation_config()
        llm_cfg = cfg.providers.get("llm", {}) if isinstance(cfg.providers, dict) else {}
        self.model = model or llm_cfg.get("model") or DEFAULT_LLM_MODEL
        self.timeout_sec = float(llm_cfg.get("timeout_sec") or timeout_sec or 30.0)
        self.base_url = (
            (base_url or "").strip()
            or (llm_cfg.get("base_url") or "").strip()
            or os.getenv("DASHSCOPE_BASE_URL")
            or DEFAULT_QWEN_BASE_URL
        )
        self.client = self._create_client()

    def _create_client(self) -> Optional[OpenAI]:
        api_key = DASHSCOPE_API_KEY or os.getenv("DASHSCOPE_API_KEY")
        if not api_key:
            logger.warning("DASHSCOPE_API_KEY not set; llm translation unavailable")
            return None
        try:
            return OpenAI(api_key=api_key, base_url=self.base_url)
        except Exception as exc:
            logger.error("Failed to initialize llm translation client: %s", exc, exc_info=True)
            return None

    def translate(
        self,
        text: str,
        target_lang: str,
        source_lang: Optional[str] = None,
        context: Optional[str] = None,
        prompt: Optional[str] = None,
    ) -> Optional[str]:
        if not text or not str(text).strip():
            return text
        if not self.client:
            return None

        tgt = (target_lang or "").lower() or "en"
        src = (source_lang or "auto").lower()
        scene = context or "default"
        user_prompt = prompt or _build_prompt(
            text=text,
            source_lang=src,
            target_lang=tgt,
            scene=scene,
        )
        start = time.time()
        try:
            logger.info(
                "[llm] Request | src=%s tgt=%s model=%s prompt=%s",
                src,
                tgt,
                self.model,
                user_prompt,
            )
            completion = self.client.chat.completions.create(
                model=self.model,
                messages=[{"role": "user", "content": user_prompt}],
                timeout=self.timeout_sec,
            )
            content = (completion.choices[0].message.content or "").strip()
            latency_ms = (time.time() - start) * 1000
            if not content:
                logger.warning("[llm] Empty result | src=%s tgt=%s latency=%.1fms", src, tgt, latency_ms)
                return None
            logger.info("[llm] Success | src=%s tgt=%s src_text=%s response=%s latency=%.1fms", src, tgt, text, content, latency_ms)
            return content
        except Exception as exc:
            latency_ms = (time.time() - start) * 1000
            logger.warning(
                "[llm] Failed | src=%s tgt=%s latency=%.1fms error=%s",
                src,
                tgt,
                latency_ms,
                exc,
                exc_info=True,
            )
            return None


def llm_translate(
    text: str,
    target_lang: str,
    *,
    source_lang: Optional[str] = None,
    source_lang_label: Optional[str] = None,
    target_lang_label: Optional[str] = None,
    timeout_sec: Optional[float] = None,
) -> Optional[str]:
    provider = LLMTranslatorProvider(timeout_sec=timeout_sec or 30.0)
    return provider.translate(
        text=text,
        target_lang=target_lang,
        source_lang=source_lang,
        context=None,
    )


__all__ = ["LLMTranslatorProvider", "llm_translate"]