from mutagen.id3 import ID3
from pathlib import Path


def get_reorganize_vars(filepath: Path) -> tuple[str, str]:
    """
    Takes in a path to an audio file
    returns the (artist, album) as a tuple of strings

    if no artist or album or ID3 tags at all are found,
    function will return ("Unknown Artist", "Unknown Album")
    """
    # logging.debug(f"getting reorganize vars for {filepath}")
    # TODO: fix this func. id3_remap(get_tags())
    # or is what i have less memory so more better? :shrug:
    audio = ID3(filepath)
    try:
        artist = str(audio["TPE1"].text[0])
        if artist == "":
            artist = "Unknown Artist"
    except KeyError:
        artist = "Unknown Artist"

    try:
        album = str(audio["TALB"].text[0])
        if album == "":
            album = "Unknown Album"
    except KeyError:
        album = "Unknown Album"

    return artist, album


def synchsafe_to_int(b):
    """Convert 4 synchsafe bytes to int (ID3v2.4)."""
    return (b[0] << 21) | (b[1] << 14) | (b[2] << 7) | b[3]


def decode_text_frame(data):
    """Decode ID3 text frame payload."""
    if not data:
        return None

    encoding_byte = data[0]
    text_bytes = data[1:]

    if encoding_byte == 0:
        return text_bytes.decode("iso-8859-1", errors="replace").rstrip("\x00")
    elif encoding_byte == 1:
        return text_bytes.decode("utf-16", errors="replace").rstrip("\x00")
    elif encoding_byte == 2:
        return text_bytes.decode("utf-16-be", errors="replace").rstrip("\x00")
    elif encoding_byte == 3:
        return text_bytes.decode("utf-8", errors="replace").rstrip("\x00")
    else:
        return None


def parse_artist_album(filepath) -> tuple[str, str]:
    with open(filepath, "rb") as f:
        header = f.read(10)

        if len(header) < 10 or header[0:3] != b"ID3":
            raise ValueError("No ID3v2 tag found")

        version_major = header[3]
        tag_size = synchsafe_to_int(header[6:10])

        artist = None
        album = None

        start_pos = f.tell()

        while f.tell() - start_pos < tag_size:
            frame_header = f.read(10)
            if len(frame_header) < 10:
                break

            frame_id = frame_header[0:4].decode("ascii", errors="replace")

            # Stop at padding
            if frame_id.strip("\x00") == "":
                break

            if version_major == 4:
                frame_size = synchsafe_to_int(frame_header[4:8])
            else:
                frame_size = int.from_bytes(frame_header[4:8], "big")

            # Skip flags (bytes 8–9 already included in header)
            frame_data = f.read(frame_size)

            if frame_id == "TPE1":
                artist = decode_text_frame(frame_data)
            elif frame_id == "TALB":
                album = decode_text_frame(frame_data)

            if artist and album:
                break

        if not artist:
            artist = "Unknown Arist"
        if not album:
            album = "Unknown Album"

        return artist, album