Add Song

from __future__ import annotations

from pathlib import Path

from typing import Self

import filecmp

from dataclasses import dataclass

@dataclass(frozen=True)

class Song:

    """

    A song, represented by a txt file and accompanying files (most importantly, an audio file).

    See https://usdx.eu/format/ for the specification.

    """

    title: str

    artist: str

    audio: Path | None

    video: Path | None

    cover: Path | None

    song_txt: Path

    @property

    def dir(self) -> Path:

        return self.song_txt.parent

    def has_identic_files(self, other: Song) -> bool:

        """

        Return if the directory for this song and the directory for the other song contain identic files.

        """

        comparison = filecmp.dircmp(self.dir, other.dir, shallow=False)

        # Two directories are identic if they don't have any differing files, and if there were also no

        # errors during comparison.

        #

        # See also:

        # - https://docs.python.org/3/library/filecmp.html#filecmp.dircmp.diff_files

        return not comparison.diff_files and not comparison.funny_files

    @classmethod

    def from_song_txt(cls, song_txt: Path) -> Self | None:

        with song_txt.open(encoding="utf-8", errors="ignore") as f:

            tags = dict(_parse_tag_line(line) for line in f if line.startswith("#"))

        title = tags.get("TITLE")

        artist = tags.get("ARTIST")

        audio_name = tags.get("AUDIO", tags.get("MP3"))

        video_name = tags.get("VIDEO")

        cover_name = tags.get("COVER")

        if not title or not artist:

            # Both are mandatory according to the specification

            return None

        return cls(

            title=title,

            artist=artist,

            audio=song_txt / audio_name if audio_name else None,

            video=song_txt / video_name if video_name else None,

            cover=song_txt / cover_name if cover_name else None,

            song_txt=song_txt,

        )

def _parse_tag_line(tag_line: str) -> tuple[str, str | None]:

    """

    Parse a tag line of the format:

        #KEY:Value

    or

        #KEY:

    Returns a tuple of (key, value), where the value might be None.

    """

    key_and_potentially_value = tuple(

        tag_line.strip().removeprefix("#").split(":", maxsplit=1)

    )

    return (

        key_and_potentially_value

        if len(key_and_potentially_value) == 2

        else (key_and_potentially_value[0], None)

    )