#!/usr/bin/env python3
"""
Reformat ƥMIX mp3 filenames and metadata titles.

Filename: ∆•MIX01.mp3 → ∆•MIX_001.mp3
Metadata title: ∆•MIX01 → ∆•MIX 001

Files with no number (∆•MIXΩ, ∆•MIX+, ∆•RYZ...) are left alone.
Files with extra text (ƥMIX12_(PVFM_12th_Anniversary)) are handled correctly.

Usage:
    python3 reformat_mixes.py /path/to/folder
    python3 reformat_mixes.py /path/to/folder --dry-run   (preview only)
"""

import os
import re
import sys
from pathlib import Path

try:
    from mutagen.mp3 import MP3
    from mutagen.id3 import ID3, TIT2
except ImportError:
    print("Missing dependency. Install with:  pip install mutagen")
    sys.exit(1)

MIX_PREFIX = r'([∆Δ]•MIX)'
NUMBER_RE = re.compile(MIX_PREFIX + r'(\d+)(.*)', re.DOTALL)


def transform_title(title: str) -> str:
    """∆•MIX01 → ∆•MIX 001  (space + zero-padded)"""
    m = NUMBER_RE.match(title)
    if not m:
        return title
    prefix, num, rest = m.group(1), m.group(2), m.group(3)
    return f"{prefix} {int(num):03d}{rest}"


def transform_filename(name: str) -> str:
    """∆•MIX01_(extra).mp3 → ∆•MIX_001_(extra).mp3"""
    stem, ext = os.path.splitext(name)
    m = NUMBER_RE.match(stem)
    if not m:
        return name
    prefix, num, rest = m.group(1), m.group(2), m.group(3)
    return f"{prefix}_{int(num):03d}{rest}{ext}"


def process(directory: str, dry_run: bool = False):
    folder = Path(directory)
    mp3_files = sorted(folder.glob('*.mp3'))

    if not mp3_files:
        print(f"No .mp3 files found in {folder}")
        return

    rename_queue = []

    for path in mp3_files:
        print(f"\n{path.name}")

        # --- metadata ---
        try:
            audio = MP3(str(path), ID3=ID3)
            if audio.tags is None:
                audio.add_tags()

            old_title = str(audio.tags['TIT2']) if 'TIT2' in audio.tags else None
            new_title = transform_title(old_title) if old_title else None

            if new_title and new_title != old_title:
                print(f"  title:  {old_title!r}  →  {new_title!r}")
                if not dry_run:
                    audio.tags['TIT2'] = TIT2(encoding=3, text=new_title)
                    audio.save()
            else:
                print(f"  title:  {old_title!r}  (no change)")
        except Exception as e:
            print(f"  ERROR reading metadata: {e}")

        # --- filename ---
        new_name = transform_filename(path.name)
        if new_name != path.name:
            new_path = path.parent / new_name
            print(f"  file:   {path.name}  →  {new_name}")
            if not dry_run:
                rename_queue.append((path, new_path))
        else:
            print(f"  file:   {path.name}  (no change)")

    for old, new in rename_queue:
        old.rename(new)

    renamed = len(rename_queue)
    if dry_run:
        print(f"\n[dry run] would rename {renamed} files. Run without --dry-run to apply.")
    else:
        print(f"\nDone. {renamed} files renamed.")


if __name__ == '__main__':
    args = sys.argv[1:]
    dry = '--dry-run' in args
    args = [a for a in args if a != '--dry-run']
    directory = args[0] if args else '.'
    process(directory, dry_run=dry)