"""PDF 下载与源码下载 — 从 arXiv 下载论文 PDF 和 LaTeX 源码包。"""

from __future__ import annotations

import logging
import shutil
import zipfile
from pathlib import Path

from app.utils import PAPERS_DIR, TMP_DIR, make_http_client

logger = logging.getLogger(__name__)


# ── 自定义异常 ──────────────────────────────────────────────────────────


class PdfDownloadError(Exception):
    pass


# ── 路径工具 ────────────────────────────────────────────────────────────


def paper_dir(arxiv_id: str) -> Path:
    return PAPERS_DIR / arxiv_id


def tmp_dir(arxiv_id: str) -> Path:
    return TMP_DIR / arxiv_id


# ── PDF 下载 ────────────────────────────────────────────────────────────


async def download_pdf(arxiv_id: str, pdf_url: str) -> Path:
    """下载 PDF 到 data/tmp/{arxiv_id}/paper.pdf。"""
    if not pdf_url:
        raise PdfDownloadError(f"no pdf_url for {arxiv_id}")

    dest_dir = tmp_dir(arxiv_id)
    dest_dir.mkdir(parents=True, exist_ok=True)
    dest = dest_dir / "paper.pdf"

    try:
        async with make_http_client(follow_redirects=True) as client:
            resp = await client.get(pdf_url)
            resp.raise_for_status()
            dest.write_bytes(resp.content)
    except Exception as exc:
        raise PdfDownloadError(f"failed to download PDF for {arxiv_id}: {exc}") from exc

    logger.info("Downloaded PDF: %s (%d bytes)", arxiv_id, dest.stat().st_size)
    return dest


# ── 源码下载 ────────────────────────────────────────────────────────────


async def download_source_zip(arxiv_id: str, source_url: str, dest_dir: Path) -> None:
    """下载 arXiv 源码并解压。"""
    dest_dir.mkdir(parents=True, exist_ok=True)
    zip_path = tmp_dir(arxiv_id) / "source.zip"

    try:
        async with make_http_client(follow_redirects=True) as client:
            resp = await client.get(source_url)
            resp.raise_for_status()
            zip_path.write_bytes(resp.content)
    except Exception as exc:
        logger.debug("Failed to download source for %s: %s", arxiv_id, exc)
        return

    try:
        with zipfile.ZipFile(zip_path, "r") as zf:
            zf.extractall(dest_dir)
        logger.debug("Extracted source for %s", arxiv_id)
    except zipfile.BadZipFile:
        # 可能是 tar.gz
        import tarfile

        try:
            with tarfile.open(zip_path, "r:*") as tf:
                tf.extractall(dest_dir, filter="data")
            logger.debug("Extracted source (tar) for %s", arxiv_id)
        except Exception:
            logger.warning("Cannot extract source for %s", arxiv_id)
    except Exception:
        logger.warning("Cannot extract source for %s", arxiv_id, exc_info=True)
    finally:
        if zip_path.exists():
            zip_path.unlink()


# ── 临时文件清理 ────────────────────────────────────────────────────────


def cleanup_tmp(arxiv_id: str) -> None:
    """清理 data/tmp/{arxiv_id}/ 目录。"""
    td = tmp_dir(arxiv_id)
    if td.exists():
        try:
            shutil.rmtree(td)
            logger.debug("Cleaned tmp: %s", arxiv_id)
        except Exception:
            logger.warning("Failed to clean tmp for %s", arxiv_id, exc_info=True)