symuid/symuid/tag_interface.py

# -*- coding: utf-8 -*-

import mutagen.id3
import mutagen.mp4


class _mutagen:

    @property
    def track_path(self):
        return self._mutagen_file.filename

    def save(self):
        self._mutagen_file.save()


class ID3(_mutagen):

    def __init__(self, mutagen_file):
        assert mutagen_file.tags, mutagen_file
        assert isinstance(mutagen_file.tags, mutagen.id3.ID3), \
            mutagen_file.tags
        self._mutagen_file = mutagen_file

    def get_free_int(self, tag_label):
        values = self._mutagen_file.tags['TXXX:' + tag_label].text
        assert len(values) == 1, values
        return int(values[0])

    def set_free_int(self, tag_label, data):
        # mutagen.id3._specs.EncodedTextSpec.write encodes 'desc' and 'text'
        tag = mutagen.id3.TXXX(
            encoding=mutagen.id3.Encoding.LATIN1,
            desc=tag_label,
            text=[str(data)],
        )
        self._mutagen_file.tags.add(tag)
        return tag


class MP4(_mutagen):

    def __init__(self, mutagen_file):
        assert mutagen_file.tags, mutagen_file
        assert isinstance(mutagen_file.tags, mutagen.mp4.MP4Tags), \
            mutagen_file.tags
        self._mutagen_file = mutagen_file

    def get_free_int(self, tag_label):
        tag, = self._mutagen_file.tags['----:' + tag_label]
        # "a signed big-endian integer with length one of { 1,2,3,4,8 } bytes"
        assert tag.dataformat == mutagen.mp4.AtomDataType.INTEGER, tag.dataformat
        return int.from_bytes(tag, byteorder='big', signed=True)

    def set_free_int(self, tag_label, data):
        assert isinstance(data, int)
        tag = mutagen.mp4.MP4FreeForm(
            # "a signed big-endian integer with length one of { 1,2,3,4,8 } bytes"
            dataformat=mutagen.mp4.AtomDataType.INTEGER,
            # TODO set byte length properly
            data=data.to_bytes(1, byteorder='big', signed=True),
        )
        self._mutagen_file.tags['----:' + tag_label] = tag
        return tag