"""
natsort with files which follows the pattern file_nn.xxx or file_nn (no extension)
where nn is an integer and xxx the extension.

The files are sorted by: name, extension, value
"""

from __future__ import annotations

from pathlib import Path
from typing import Iterable, TypeVar

T = TypeVar("T", str, Path)


def natsort(iterable: Iterable[T], reverse=False) -> list[T]:
    """
    Sort the files by name, extension, integer
    """

    def keyfunc(path: str | Path) -> tuple[str, str, int]:
        """
        Keyfunc takes a str or a path object and
        returns (name: str, suffix: str, value: int)
        """
        path = Path(path)

        try:
            name, number = path.stem.split("_")
        except ValueError:
            return path.name, path.suffix, -1

        return name, path.suffix, int(number)

    return sorted(iterable, key=keyfunc, reverse=reverse)


ns = natsort(["file1.txt", "file_2.txt", "file_3.txt"])
print(ns)