from __future__ import annotations

import json
import urllib.error
import urllib.request

from config import get_settings


class LlmServiceError(Exception):
    pass


class LlmService:
    def is_configured(self) -> bool:
        return bool(get_settings().deepseek_api_key.strip())

    def model_name(self) -> str:
        return get_settings().deepseek_model

    def _chat_completion(
        self,
        *,
        messages: list[dict],
        temperature: float = 0.2,
        max_tokens: int = 1800,
        response_format: dict | None = None,
        timeout: int = 15,
    ) -> str:
        settings = get_settings()
        api_key = settings.deepseek_api_key.strip()
        if not api_key:
            raise LlmServiceError("DeepSeek API key is not configured")

        payload: dict = {
            "model": settings.deepseek_model,
            "messages": messages,
            "temperature": temperature,
            "max_tokens": max_tokens,
        }
        if response_format:
            payload["response_format"] = response_format

        request = urllib.request.Request(
            f"{settings.deepseek_base_url.rstrip('/')}/v1/chat/completions",
            data=json.dumps(payload).encode("utf-8"),
            headers={
                "Authorization": f"Bearer {api_key}",
                "Content-Type": "application/json",
            },
            method="POST",
        )
        try:
            with urllib.request.urlopen(request, timeout=timeout) as response:
                body = json.loads(response.read().decode("utf-8"))
        except urllib.error.HTTPError as exc:
            detail = exc.read().decode("utf-8", errors="replace")
            raise LlmServiceError(f"DeepSeek HTTP {exc.code}: {detail}") from exc
        except urllib.error.URLError as exc:
            raise LlmServiceError(f"DeepSeek request failed: {exc.reason}") from exc

        try:
            content = body["choices"][0]["message"]["content"]
        except (KeyError, IndexError, TypeError) as exc:
            raise LlmServiceError("DeepSeek response format is invalid") from exc
        return str(content).strip()

    @staticmethod
    def _strip_code_fence(text: str) -> str:
        cleaned = text.strip()
        if not cleaned.startswith("```"):
            return cleaned
        cleaned = cleaned.strip("`").strip()
        if cleaned.lower().startswith("json"):
            cleaned = cleaned[4:].lstrip()
        elif cleaned.lower().startswith("markdown"):
            cleaned = cleaned[8:].lstrip()
        return cleaned.strip()

    def enhance_wiki_page(self, *, title: str, draft_markdown: str) -> str:
        prompt = (
            "你是 WordLoop 个人学习 Wiki 的编译器，遵循 Karpathy Wiki 思路："
            "把原始学习事件整理成简洁、可检索的 Markdown 知识页。\n"
            "要求：\n"
            "1. 保留草稿中的事实数据（释义、掌握度、练习记录等），不要编造。\n"
            "2. 优化结构、摘要与关联说明，便于日后复习。\n"
            "3. 只输出 Markdown 正文，不要代码块包裹，不要额外解释。\n"
            f"\n页面标题：{title}\n\n草稿：\n{draft_markdown}"
        )
        content = self._chat_completion(
            messages=[
                {"role": "system", "content": "你是严谨的学习笔记整理助手。"},
                {"role": "user", "content": prompt},
            ],
            temperature=0.2,
            max_tokens=1800,
        )
        cleaned = self._strip_code_fence(content)
        return cleaned or draft_markdown

    def parse_word_pairs_from_text(self, text: str) -> list[dict[str, str]]:
        prompt = (
            "你是英语学习词表整理助手。从 OCR 识别文本中提取英汉单词对。\n"
            "要求：\n"
            "1. 只提取明确的单词/短语与其中文释义，不要编造。\n"
            "2. 忽略页码、标题、序号、噪声行。\n"
            "3. 输出 JSON 对象，格式为 {\"items\":[{\"en\":\"...\",\"zh\":\"...\"}]}。\n"
            "4. en 为英文，zh 为中文；若原文是中文在前英文在后，也要正确归位。\n"
            "5. 只输出 JSON，不要解释。\n"
            f"\nOCR 文本：\n{text.strip()}"
        )
        content = self._chat_completion(
            messages=[
                {"role": "system", "content": "你只输出合法 JSON。"},
                {"role": "user", "content": prompt},
            ],
            temperature=0.1,
            max_tokens=4000,
            response_format={"type": "json_object"},
            timeout=30,
        )
        cleaned = self._strip_code_fence(content)
        try:
            payload = json.loads(cleaned)
        except json.JSONDecodeError as exc:
            raise LlmServiceError("词表解析结果不是合法 JSON") from exc

        raw_items = payload.get("items") if isinstance(payload, dict) else payload
        if not isinstance(raw_items, list):
            raise LlmServiceError("词表解析结果缺少 items 数组")

        pairs: list[dict[str, str]] = []
        for item in raw_items:
            if not isinstance(item, dict):
                continue
            en = str(item.get("en") or item.get("source_text") or "").strip()
            zh = str(item.get("zh") or item.get("target_text") or "").strip()
            if en and zh:
                pairs.append({"en": en, "zh": zh})
        return pairs


llm_service = LlmService()