98 lines
3.6 KiB
Python
98 lines
3.6 KiB
Python
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#!/usr/bin/env python3
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"""List the tracks a sync has to copy again because their album was re-levelled.
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Reads rsync's `--out-format='%l %n'` output on stdin and writes mirror-relative
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paths on stdout, one per line, for feeding straight back to rsync as
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`--files-from`.
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The problem it solves: a ReplayGain album gain is a property of every track on
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the record, so one track arriving or leaving changes the tags on all of its
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siblings. rsgain writes the new values into the padding its previous write left
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behind, which leaves both the file's size and its mtime untouched -- and size
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and mtime are exactly what rsync's quick check compares. It sees nothing to do,
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and the device keeps the old gains.
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What rsync always can see is the track that arrived or left. So any album it
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touched has the rest of its tracks copied again, and nothing else does.
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Tracks rsync has already dealt with are left out of the list. After a quality
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upgrade that replaces every track on a record, listing them again would send
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the whole album twice.
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"""
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import argparse
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import re
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import sys
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from pathlib import Path
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# Under --out-format='%l %n' a transfer is reported as the size, a space and
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# the path. A removal is reported as "deleting <path>" whatever the format is.
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# Everything else on the stream is rsync talking to the operator -- the file
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# list preamble, the byte totals -- and is not a path.
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TRANSFER = re.compile(r"^(\d+) (.+)$")
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DELETION = re.compile(r"^deleting (.+)$")
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# What the mirror is made of, and so the only thing worth copying again. A
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# cover is not rewritten by a re-level.
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MIRROR_SUFFIX = ".mp3"
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def touched(lines):
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"""Return the paths rsync transferred and the directories it changed."""
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transferred = set()
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directories = set()
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for line in lines:
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line = line.rstrip("\n")
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deletion = DELETION.match(line)
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transfer = None if deletion else TRANSFER.match(line)
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if deletion:
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path = deletion.group(1)
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elif transfer:
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path = transfer.group(2)
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else:
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continue
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# Only a track can change an album's gains. rsync reports the
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# directories it creates and removes too, and a cover replaced on its
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# own is no reason to send the record again.
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if not path.endswith(MIRROR_SUFFIX):
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continue
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if transfer:
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transferred.add(path)
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directories.add(path.rpartition("/")[0])
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return transferred, directories
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def remaining(mirror, transferred, directories):
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"""Return the tracks in those directories that rsync has not just copied."""
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paths = []
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for directory in sorted(directories):
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album = mirror / directory if directory else mirror
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if not album.is_dir():
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# Removed along with the last of its tracks. Nothing to copy.
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continue
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for track in sorted(album.glob(f"*{MIRROR_SUFFIX}")):
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relative = f"{directory}/{track.name}" if directory else track.name
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if relative not in transferred:
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paths.append(relative)
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return paths
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def main(argv=None, stream=None, out=None):
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parser = argparse.ArgumentParser(
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prog="touched_albums.py",
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description="List the tracks to copy again after an album was re-levelled.",
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)
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parser.add_argument("--mirror", required=True, type=Path, help="root of the MP3 mirror")
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args = parser.parse_args(argv)
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transferred, directories = touched(stream if stream is not None else sys.stdin)
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for path in remaining(args.mirror, transferred, directories):
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print(path, file=out if out is not None else sys.stdout)
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return 0
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if __name__ == "__main__":
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sys.exit(main())
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