from __future__ import annotations

import shutil
from datetime import datetime
from pathlib import Path


def backup_file(source: Path, backup_dir: Path) -> None:
    if not source.exists():
        return
    backup_dir.mkdir(parents=True, exist_ok=True)
    timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
    target = backup_dir / f"{source.stem}_{timestamp}{source.suffix}"
    shutil.copy2(source, target)