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

Filename changes:
  ∆•MIX13.flac                          → ∆•MIX_013.flac
  ∆•MIX74 (07-04 Mix).flac              → ∆•MIX_074_(07-04_Mix).flac
  ∆•MIX (Ponies @ Dawn Fusion Mix).flac → ∆•MIX_(Ponies_@_Dawn_Fusion_Mix).flac
  ∆•MIXΩ (PVFM 13th Birthday).flac      → ∆•MIXΩ_(PVFM_13th_Birthday).flac
  ∆•RYZ • SPEEDWAGON B2B.flac           → ∆•RYZ_•_SPEEDWAGON_B2B.flac

Metadata title changes (same as mp3 script):
  ∆•MIX99 → ∆•MIX 099

Usage:
    python3 reformat_mixes_flac.py /path/to/FLAC/folder
    python3 reformat_mixes_flac.py /path/to/FLAC/folder --dry-run
"""

import os
import re
import sys
from pathlib import Path

try:
    from mutagen.flac import FLAC
except ImportError:
    print("Missing dependency. Install with:  pip install mutagen")
    sys.exit(1)

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


def transform_title(title: str) -> str:
    """∆•MIX99 → ∆•MIX 099"""
    m = MIX_NUMBER_RE.match(title)
    if not m:
        return title
    return f"{m.group(1)} {int(m.group(2)):03d}{m.group(3)}"


KEEP_AS_IS = {'∆•RYZ • SPEEDWAGON B2B', 'Δ•RYZ • SPEEDWAGON B2B'}


def transform_filename(name: str) -> str:
    """
    1. Replace spaces with underscores in the stem (except excluded files).
    2. Insert underscore + zero-pad number where present.
    """
    stem, ext = os.path.splitext(name)

    # Files explicitly excluded from space replacement
    if stem in KEEP_AS_IS:
        return name

    # Step 1: spaces → underscores
    stem = stem.replace(' ', '_')

    # Step 2: zero-pad number (∆•MIX13 → ∆•MIX_013)
    m = MIX_NUMBER_RE.match(stem)
    if m:
        stem = f"{m.group(1)}_{int(m.group(2)):03d}{m.group(3)}"

    return stem + ext


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

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

    rename_queue = []

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

        # --- metadata ---
        try:
            audio = FLAC(str(path))

            old_title = audio['title'][0] if 'title' in audio 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['title'] = 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:
            print(f"  file:   {path.name}  →  {new_name}")
            if not dry_run:
                rename_queue.append((path, path.parent / new_name))
        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)