#!/usr/bin/env python3
"""One-time migration: clear iTunes' guessed ("computed") ratings from an
already-imported lintunes library, without touching anything else.

Reads the iTunes XML to find which tracks had `Rating Computed` set, then
zeroes `rating`/`album_rating` for those tracks in <data-dir>/library.json,
matching by persistent ID (track IDs are not stable across exports).

Usage:
    python3 scripts/clear_computed_ratings.py \
        --xml "itunes-test-library/iTunes Library.xml" --data-dir ./data
"""
import argparse
import json
import plistlib
import sys
from pathlib import Path


def main():
    parser = argparse.ArgumentParser(description=__doc__.splitlines()[0])
    parser.add_argument("--xml", required=True, help="iTunes Library XML file")
    parser.add_argument("--data-dir", required=True, help="lintunes data dir")
    parser.add_argument("--dry-run", action="store_true",
                        help="Report what would change without writing")
    args = parser.parse_args()

    xml_path = Path(args.xml)
    library_path = Path(args.data_dir) / "library.json"
    if not xml_path.exists():
        sys.exit(f"XML not found: {xml_path}")
    if not library_path.exists():
        sys.exit(f"Library not found: {library_path}")

    print(f"Reading {xml_path}...")
    with open(xml_path, "rb") as f:
        plist = plistlib.load(f)

    computed_rating_pids = set()
    computed_album_pids = set()
    for itunes_track in plist.get("Tracks", {}).values():
        pid = itunes_track.get("Persistent ID")
        if not pid:
            continue
        if itunes_track.get("Rating Computed"):
            computed_rating_pids.add(pid)
        if itunes_track.get("Album Rating Computed"):
            computed_album_pids.add(pid)
    print(f"XML: {len(computed_rating_pids)} computed track ratings, "
          f"{len(computed_album_pids)} computed album ratings")

    with open(library_path, "r", encoding="utf-8") as f:
        tracks = json.load(f)

    rated_before = sum(1 for t in tracks.values() if t.get("rating"))
    cleared = album_cleared = 0
    for track in tracks.values():
        pid = track.get("persistent_id", "")
        if pid in computed_rating_pids and track.get("rating"):
            del track["rating"]
            cleared += 1
        if pid in computed_album_pids:
            if track.pop("album_rating", None) is not None:
                album_cleared += 1
            track.pop("album_rating_computed", None)
    rated_after = sum(1 for t in tracks.values() if t.get("rating"))

    print(f"Track ratings: {rated_before} before -> {rated_after} after "
          f"({cleared} guessed ratings cleared, {album_cleared} album ratings)")

    if args.dry_run:
        print("Dry run — nothing written.")
        return
    tmp = library_path.with_suffix(".json.tmp")
    with open(tmp, "w", encoding="utf-8") as f:
        json.dump(tracks, f, indent=2, ensure_ascii=False)
    tmp.replace(library_path)
    print(f"Wrote {library_path}")


if __name__ == "__main__":
    main()