from argparse import ArgumentParser
from pathlib import Path
from logging import basicConfig, warning, WARNING
from shutil import copyfile

def main(music_folder: Path):
    music_folder = music_folder.resolve().absolute()

    for m3u in music_folder.rglob("*.m3u"):
        copyfile(m3u, m3u.with_suffix(".m3u.bak"))

        with m3u.open("r") as contents:
            tracks = [Path(p) for p in contents.readlines()]

        if not all(
            music_folder in track.parents 
            if track.is_absolute() 
            else music_folder in m3u.parent.joinpath(track).resolve().parents
            for track in tracks
        ):
            warning(f"{m3u} contains references to tracks that are not in {music_folder} and will be skipped")
            continue
       
        with m3u.open("w") as updated_contents:
            for track in tracks:
                if track.is_absolute():
                    updated_contents.write(track.relative_to(m3u, walk_up=True).as_posix())
                else:
                    updated_contents.write(track.as_posix())


if __name__ == "__main__":
    basicConfig(
        level=WARNING,
    )
    
    parser = ArgumentParser(
        description="Recursively traverse a music folder containing tracks and playlist files that reference them, replacing absolute paths in the playlists with equivalent relative paths."
    )

    parser.add_argument(
        "music_folder",
        required=True,
        type=Path
    )

    args = parser.parse_args()

    main(args.music_folder)