"""PDF → 图片 (使用 PyMuPDF，无需 poppler 系统依赖)"""
from __future__ import annotations

from pathlib import Path
from typing import List

import fitz  # PyMuPDF
from loguru import logger

from app.config import settings


def pdf_to_images(pdf_path: str | Path, dpi: int | None = None) -> List[Path]:
    """把 PDF 每页渲染成 PNG，返回文件路径列表"""
    dpi = dpi or settings.pdf_dpi
    pdf_path = Path(pdf_path)
    out_dir = pdf_path.parent / f".{pdf_path.stem}_pages"
    out_dir.mkdir(exist_ok=True)

    doc = fitz.open(str(pdf_path))
    saved: List[Path] = []
    try:
        # 1.0 = 72 DPI 的 zoom 系数
        zoom = dpi / 72.0
        mat = fitz.Matrix(zoom, zoom)
        for idx, page in enumerate(doc, start=1):
            pix = page.get_pixmap(matrix=mat, alpha=False)
            out_path = out_dir / f"page_{idx:03d}.png"
            pix.save(str(out_path))
            saved.append(out_path)
    finally:
        doc.close()

    logger.info("PDF 转图片: {} → {} 页 (dpi={})", pdf_path.name, len(saved), dpi)
    return saved