"""Shared utilities for file naming and organization."""

import os
import re
from pathlib import Path

import mutagen


def sanitize_filename(name):
    """Remove characters prohibited in Windows filenames."""
    name = re.sub(r'[<>:"/\\|?*]', '_', name)
    return name.strip().strip('.')


def rename_from_metadata(file_path):
    """Rename an audio file to 'Title - Artist1, Artist2.ext' using embedded metadata.

    Returns the new Path (or original if rename not possible).
    """
    file_path = Path(file_path)
    audio = mutagen.File(str(file_path), easy=True)
    if audio is None:
        return file_path

    try:
        title = audio.get("title", [None])[0]
        artist = audio.get("artist", [None])[0]
    except (IndexError, KeyError):
        return file_path

    if not title or not artist:
        return file_path

    new_name = sanitize_filename(f"{title} - {artist}{file_path.suffix}")
    new_path = file_path.parent / new_name

    if new_path == file_path:
        return file_path

    # Handle collisions
    counter = 2
    base_stem = new_path.stem
    while new_path.exists():
        new_path = new_path.with_stem(f"{base_stem} ({counter})")
        counter += 1

    file_path.rename(new_path)
    return new_path


def cleanup_empty_dirs(directory):
    """Remove empty subdirectories (bottom-up)."""
    directory = Path(directory)
    for dirpath, dirnames, filenames in os.walk(str(directory), topdown=False):
        dirpath = Path(dirpath)
        if dirpath == directory:
            continue
        if not any(dirpath.iterdir()):
            dirpath.rmdir()