"""电子书种子：把 res/ 下已有的三本书挂到教材上。

幂等：只补不覆盖，管理员在后台重新上传的文件不会被种子冲掉。
"""
from __future__ import annotations

import shutil
from pathlib import Path

from sqlalchemy.orm import Session

from database import REPO_ROOT
from models import Textbook
from services import ebooks as store

RES_ROOT = REPO_ROOT / "res"

# res/ 里的文件名带书目后缀，展示时用干净的名称
PRINCETON = {
    "name": "普林斯顿微积分读本(修订版)",
    "author": "阿德里安·班纳 (Adrian Banner)",
    "publisher": "人民邮电出版社",
    "grade": "高中至大学先修",
    "description": "面向微积分入门的系统辅导书，覆盖极限、导数、积分与级数，"
    "按考点组织，适合自学与考前查漏补缺。",
    "resource": "普林斯顿微积分读本(修订版)",
    "display": "普林斯顿微积分读本(修订版).epub",
}

# 已有教材 → res/ 中的 PDF（按教材名前缀匹配）
PDF_LINKS = [
    ("函数和图像", "函数和图像", "函数和图像（盖尔范德中学生数学思维丛书）.pdf"),
    ("三角函数", "三角函数", "三角函数（盖尔范德中学生数学思维丛书）.pdf"),
]


def _find_resource(prefix: str, suffix: str) -> Path | None:
    """res/ 下的文件名带作者与来源后缀，只按标题前缀匹配。"""
    if not RES_ROOT.is_dir():
        return None
    for path in sorted(RES_ROOT.iterdir()):
        if (
            path.is_file()
            and path.suffix.lower() == suffix
            and path.name.startswith(prefix)
        ):
            return path
    return None


# 旧库里的教材：数据库只是引用磁盘上的文件，库一旦丢失，这些文件就成了孤儿。
# 按“大小 + SHA-256”认领已知电子书，重建教材条目并把文件挪进该书自己的目录，
# 管理员就不必重新上传，种子也不会再往 res/ 里复制第二份。
KNOWN_EBOOKS = [
    {
        "size": 44110741,
        "sha256": "f432fa058420f1032a169a91fe2dcefbc95c61a6793f1b0ec5fd1fcc84ee67da",
        "display": "柯西-施瓦茨大师课：不等式的艺术.pdf",
        "textbook": {
            "name": "柯西-施瓦茨大师课：不等式的艺术",
            "author": "J. Michael Steele 著；欧阳顺湘 译",
            "publisher": "高等教育出版社 · 世界数学精品译丛 7",
            "isbn": "9787040278678",
            "grade": "高中至大学",
            "description": (
                "Cambridge 出版的不等式专题大师课：以 Cauchy-Schwarz 不等式为主线，"
                "串起凸性、排序、切比雪夫、Young、Hölder、Minkowski 等常用不等式，"
                "每章配大量例题与习题，适合竞赛与数学分析进阶训练。"
            ),
        },
    },
]


def _referenced_files(db: Session) -> set[Path]:
    used: set[Path] = set()
    rows = db.query(Textbook).filter(Textbook.ebook_file != "").all()
    for row in rows:
        used.add((store.book_dir(row.id) / row.ebook_file).resolve())
    return used


def recover_lost_ebooks(db: Session) -> list[str]:
    """认领 data/ebooks 下未被引用的已知电子书，返回恢复的教材名。"""
    if not store.EBOOK_ROOT.is_dir():
        return []
    referenced = _referenced_files(db)
    recovered: list[str] = []
    for book in KNOWN_EBOOKS:
        meta = book["textbook"]
        if db.query(Textbook).filter(Textbook.name == meta["name"]).first():
            continue
        for path in sorted(store.EBOOK_ROOT.glob("*/*")):
            if not path.is_file() or path.suffix.lower() not in {".pdf", ".epub"}:
                continue
            if path.stat().st_size != book["size"] or path.resolve() in referenced:
                continue
            if store.sha256_file(path) != book["sha256"]:
                continue
            textbook = Textbook(
                **meta, position=db.query(Textbook).count()
            )
            db.add(textbook)
            db.commit()
            target_dir = store.book_dir(textbook.id)
            target_dir.mkdir(parents=True, exist_ok=True)
            shutil.move(str(path), str(target_dir / path.name))
            store.adopt_file(
                db, textbook, path.name, display_name=book["display"]
            )
            recovered.append(textbook.name)
            break
    return recovered


def ensure_ebooks(db: Session) -> None:
    created = False
    textbook = (
        db.query(Textbook).filter(Textbook.name == PRINCETON["name"]).first()
    )
    if textbook is None:
        position = (
            db.query(Textbook).count()
        )
        textbook = Textbook(
            name=PRINCETON["name"],
            author=PRINCETON["author"],
            publisher=PRINCETON["publisher"],
            grade=PRINCETON["grade"],
            description=PRINCETON["description"],
            position=position,
        )
        db.add(textbook)
        db.commit()
        created = True
    if created:
        epub = _find_resource(PRINCETON["resource"], ".epub")
        if epub is not None and not textbook.ebook_file:
            store.attach_local_file(
                db, textbook, epub, display_name=PRINCETON["display"]
            )

    for name_prefix, file_prefix, display in PDF_LINKS:
        textbook = (
            db.query(Textbook)
            .filter(Textbook.name.startswith(name_prefix))
            .first()
        )
        if textbook is None or textbook.ebook_file:
            continue
        pdf = _find_resource(file_prefix, ".pdf")
        if pdf is None:
            continue
        store.attach_local_file(db, textbook, pdf, display_name=display)

    recover_lost_ebooks(db)