"""EPUB parsing: turn a .epub file into a spine-ordered list of chapters."""

from __future__ import annotations

import hashlib
from dataclasses import dataclass
from pathlib import Path

import ebooklib
from bs4 import BeautifulSoup
from ebooklib import epub


@dataclass
class Chapter:
    title: str
    paragraphs: list[str]


@dataclass
class Book:
    id: str
    title: str
    author: str
    path: Path
    chapters: list[Chapter]


def _book_id(path: Path) -> str:
    # Identifies a book by its resolved path for now. Once the sync API exists,
    # this should switch to whatever stable id diora assigns server-side.
    return hashlib.sha256(str(path.resolve()).encode()).hexdigest()[:16]


def _extract_paragraphs(html: bytes) -> list[str]:
    soup = BeautifulSoup(html, "html.parser")
    for tag in soup(["script", "style"]):
        tag.decompose()

    paragraphs = []
    for el in soup.find_all(["p", "h1", "h2", "h3", "h4", "li", "blockquote"]):
        text = el.get_text(" ", strip=True)
        if text:
            paragraphs.append(text)

    if not paragraphs:
        text = soup.get_text(" ", strip=True)
        if text:
            paragraphs.append(text)

    return paragraphs


def load_epub(path: Path) -> Book:
    raw = epub.read_epub(str(path), options={"ignore_ncx": True})

    title_meta = raw.get_metadata("DC", "title")
    title = title_meta[0][0] if title_meta else path.stem

    author_meta = raw.get_metadata("DC", "creator")
    author = author_meta[0][0] if author_meta else "Unbekannt"

    chapters: list[Chapter] = []
    for idref, linear in raw.spine:
        if linear == "no":
            continue
        item = raw.get_item_with_id(idref)
        if item is None or item.get_type() != ebooklib.ITEM_DOCUMENT:
            continue
        paragraphs = _extract_paragraphs(item.get_content())
        if not paragraphs:
            continue
        chapters.append(Chapter(title=paragraphs[0][:60], paragraphs=paragraphs))

    return Book(id=_book_id(path), title=title, author=author, path=path, chapters=chapters)


def scan_library(library_dir: Path) -> list[Path]:
    if not library_dir.exists():
        return []
    return sorted(library_dir.rglob("*.epub"))