"""通过 ISBN 查询公开书目信息与章节目录。

优先 Open Library，其次 Google Books。网络不可用或 ISBN 无收录时返回空结果，
调用方继续使用书名 + ISBN 让大模型依据正式出版物内容生成。
"""
from __future__ import annotations

import re

import httpx


def _normalize_isbn(isbn: str) -> str:
    return re.sub(r"[^0-9Xx]", "", isbn).upper()


def _clean_toc_item(item: dict) -> str | None:
    title = str(item.get("title", "")).strip()
    label = str(item.get("label", "")).strip()
    if not title and not label:
        return None
    title = title or label
    # 去掉 Open Library 常见的前置编号/页眉，避免把“引言”“1”当标题
    title = re.sub(r"^\s*(?:page\s*)?\d+\s*[:.]?\s*", "", title, flags=re.I)
    return title.strip() or None


def fetch_isbn_context(isbn: str) -> dict:
    """返回 {source, title, description, chapter_titles}。"""
    normalized = _normalize_isbn(isbn)
    if not normalized:
        return {"source": "", "title": "", "description": "", "chapter_titles": []}

    # 1) Open Library 按 ISBN 查书目
    try:
        with httpx.Client(timeout=6.0, follow_redirects=True) as client:
            response = client.get(
                f"https://openlibrary.org/isbn/{normalized}.json"
            )
        if response.status_code == 200:
            payload = response.json()
            titles: list[str] = []
            for item in payload.get("table_of_contents") or []:
                if not isinstance(item, dict):
                    continue
                title = _clean_toc_item(item)
                if title and title not in titles:
                    titles.append(title)
            return {
                "source": "openlibrary",
                "title": str(payload.get("title", "")),
                "description": "",
                "chapter_titles": titles,
            }
    except httpx.HTTPError:
        pass

    # 2) Google Books 按 ISBN 查书目
    try:
        with httpx.Client(timeout=6.0) as client:
            response = client.get(
                "https://www.googleapis.com/books/v1/volumes",
                params={"q": f"isbn:{normalized}", "maxResults": 1},
            )
        if response.status_code == 200:
            data = response.json()
            items = data.get("items") or []
            if items:
                volume = items[0].get("volumeInfo", {})
                return {
                    "source": "google_books",
                    "title": str(volume.get("title", "")),
                    "description": str(volume.get("description", ""))[:1500],
                    "chapter_titles": [],
                }
    except httpx.HTTPError:
        pass

    return {"source": "", "title": "", "description": "", "chapter_titles": []}