52 lines
1.6 KiB
Python
52 lines
1.6 KiB
Python
from hashlib import blake2b
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from pathlib import Path
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from typing import Final
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from uuid import UUID
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from ...song import Song
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# The maximum size for a BLAKE2b "person" value is sixteen bytes, so we need to be concise.
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HASH_PERSON_PREFIX: Final = b"mnp.mac."
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RECORDING_ID_HASH_PERSON: Final = HASH_PERSON_PREFIX + b"mb_rid"
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TRACK_ID_HASH_PERSON: Final = HASH_PERSON_PREFIX + b"mb_tid"
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FILE_HASH_PERSON: Final = HASH_PERSON_PREFIX + b"f"
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PERSISTENT_ID_BITS: Final = 64
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PERSISTENT_ID_BYTES: Final = PERSISTENT_ID_BITS // 8
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def digest_recording_id(recording_id: UUID) -> bytes:
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return blake2b(
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recording_id.bytes,
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digest_size=PERSISTENT_ID_BYTES,
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person=RECORDING_ID_HASH_PERSON,
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).digest()
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def digest_track_id(track_id: UUID) -> bytes:
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return blake2b(
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track_id.bytes,
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digest_size=PERSISTENT_ID_BYTES,
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person=TRACK_ID_HASH_PERSON,
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).digest()
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def digest_file_uri(file: Path) -> bytes:
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return blake2b(
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bytes(file), digest_size=PERSISTENT_ID_BYTES, person=FILE_HASH_PERSON
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).digest()
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# The MPMediaItemPropertyPersistentID is only 64 bits, while a UUID is 128
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# bits and not all tracks will even have their MusicBrainz track ID included.
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# To work around this, we compute a BLAKE2 hash from the UUID, or failing
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# that from the file URI. BLAKE2 can be customised to different digest sizes,
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# making it perfect for this problem.
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def song_to_persistent_id(song: Song) -> int:
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if song.musicbrainz.recording:
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hashed_id = digest_recording_id(song.musicbrainz.recording)
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elif song.musicbrainz.track:
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hashed_id = digest_track_id(song.musicbrainz.track)
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else:
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hashed_id = digest_file_uri(song.file)
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return int.from_bytes(hashed_id)
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