import jsonfile
import youtube

MUSIC_FILE = "music.json"


def load_videos() -> tuple[dict, list[str]]:
    data = jsonfile.load(MUSIC_FILE)
    return data, data.setdefault("videos", [])


def find_index(videos: list[str], identifier: str) -> int | None:
    return next((index for index, video in enumerate(videos) if youtube.video_id(video) == identifier), None)


def list_songs(arguments) -> None:
    _, videos = load_videos()
    if not videos:
        print("The playlist is empty.")
        return
    for number, video in enumerate(videos, start=1):
        identifier = youtube.video_id(video) or "?"
        title = youtube.video_title(identifier) if arguments.titles else None
        print(f"{number:>3}. {identifier}  {title or video}")


def add_songs(arguments) -> None:
    data, videos = load_videos()
    added = 0
    for text in arguments.songs:
        identifier = youtube.video_id(text)
        if not identifier:
            print(f"Skipped {text}: not a YouTube link or video ID.")
            continue
        if find_index(videos, identifier) is not None:
            print(f"Skipped {identifier}: already in the playlist.")
            continue
        videos.append(youtube.watch_url(identifier))
        added += 1
        print(f"Added {youtube.video_title(identifier) or identifier}")
    if added:
        jsonfile.save(MUSIC_FILE, data)


def remove_song(arguments) -> None:
    data, videos = load_videos()
    identifier = youtube.video_id(arguments.song)
    index = find_index(videos, identifier) if identifier else None
    if index is None:
        print(f"{arguments.song} is not in the playlist.")
        return
    videos.pop(index)
    jsonfile.save(MUSIC_FILE, data)
    print(f"Removed {identifier}")


def register(subparsers) -> None:
    parser = subparsers.add_parser("music", help="Manage the music playlist")
    actions = parser.add_subparsers(dest="action", required=True)

    list_parser = actions.add_parser("list", help="List songs in the playlist")
    list_parser.add_argument("--titles", action="store_true", help="Look up song titles on YouTube")
    list_parser.set_defaults(handler=list_songs)

    add_parser = actions.add_parser("add", help="Add songs by YouTube link or video ID")
    add_parser.add_argument("songs", nargs="+", help="YouTube links or video IDs")
    add_parser.set_defaults(handler=add_songs)

    remove_parser = actions.add_parser("remove", help="Remove a song by YouTube link or video ID")
    remove_parser.add_argument("song", help="YouTube link or video ID")
    remove_parser.set_defaults(handler=remove_song)