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noteman-slicer/noteman_slicer/bundle.py
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Esa Kataja b8d93cee47 Specify the Score Bundle Format, and make tempo an integer
The bundle is documented as a standalone format rather than as a note
between two programs: producers and consumers are generic, the marker
vocabulary is defined musically rather than by what a viewer does with
it, and image properties are stated as guarantees with the reasoning
where it is not obvious. Anything that reads scores can implement it
without knowing this tool exists.

Taking that view changed the substance in three places. Marker types now
carry their musical meaning rather than a UI mapping. The rule against
re-importing became a statement about identity - indices mean something
only within one bundle, so two bundles of a piece are independent
documents. And forward-compatibility rules were added, which a protocol
needs and a handover note did not: ignore unknown fields and marker
types, refuse an unknown version.

Tempo is now an integer, beats per minute, exported as a JSON number and
omitted when blank; the editor accepts digits only. A figure can drive a
metronome or a click track where a verbal marking cannot, and readers do
not agree on what Andante means. This needs the consumer's column
changed from free-form text, which the format document flags.

Every figure in the document comes from a real export.
2026-07-29 09:22:43 +03:00

123 lines
4.1 KiB
Python

"""Bundle export — the only channel to noteman (ADR 0001).
song.zip
song.json
original.pdf
001.webp 002.webp …
Array order in `song.json` *is* slice order: one ordering, not two. Markers
nest inside the slice they sit on, so an index appears in exactly one place —
a jump source's `destination`.
"""
from __future__ import annotations
import json
import zipfile
from pathlib import Path
from .pdf import Source
from .project import Project
from .render import render_song
FORMAT_VERSION = 1
METADATA_FIELDS = (
"title",
"subtitle",
"composer",
"original_artist",
"arranger",
"lyricist",
"translator",
"tempo",
"voices",
)
# Beats per minute, exported as a JSON number. A figure is worth more than a
# word here: "Andante" cannot drive a metronome and two people will not agree
# what it means.
NUMERIC_FIELDS = frozenset({"tempo"})
def song_json(project: Project, files: list[str]) -> dict:
payload: dict = {"v": FORMAT_VERSION}
for field in METADATA_FIELDS:
value = (project.metadata.get(field) or "").strip()
if not value:
continue
if field in NUMERIC_FIELDS:
try:
payload[field] = int(value)
except ValueError:
continue # not a number, so not worth exporting as one
else:
payload[field] = value
kept = project.kept_slices()
# Markers reference slices by (page, slot) while editing, because that is
# what survives adding and removing cuts. In the bundle they become the
# array index, which is the only cross-reference the format has.
index_of = {position: i for i, position in enumerate(kept)}
slices: list[dict] = []
for name, (page, slot) in zip(files, kept):
entry: dict = {"file": name}
markers = []
for marker in project.pages[page].markers[slot]:
item: dict = {"type": marker.type}
if marker.label:
item["label"] = marker.label
if marker.destination is not None:
target = index_of.get(tuple(marker.destination))
# A jump whose target was discarded or re-cut away is dropped
# rather than exported dangling: noteman would have nothing to
# resolve it to.
if target is None:
continue
item["destination"] = target
markers.append(item)
if markers:
entry["markers"] = markers
slices.append(entry)
payload["slices"] = slices
return payload
def write(project: Project, source: Source, path: Path) -> Path:
"""Render the song and write the bundle. Returns the zip path.
A title is required; every other metadata field is optional. noteman's own
rule is that a song needs a title and at least one slice, and a bundle that
cannot become a song is not worth writing.
"""
if not project.metadata.get("title", "").strip():
raise ValueError("a title is required before a song can be exported")
images = render_song(project, source)
if not images:
raise ValueError("no slices to export — every slice is discarded")
names = [f"{i + 1:03}.webp" for i in range(len(images))]
path = Path(path)
path.parent.mkdir(parents=True, exist_ok=True)
# ZIP_STORED for the images: WebP is already compressed, so deflating it
# only costs time. The JSON is small enough not to care.
with zipfile.ZipFile(path, "w") as zf:
zf.writestr(
"song.json",
json.dumps(song_json(project, names), indent=2, ensure_ascii=False),
zipfile.ZIP_DEFLATED,
)
if project.source.exists():
zf.write(project.source, "original.pdf")
for name, data in zip(names, images):
zf.writestr(name, data, zipfile.ZIP_STORED)
# The project is spent once its song has been exported: the next edit
# session starts fresh from detection rather than resuming these decisions.
# Recorded here so no caller can forget it.
project.exported = True
project.save()
return path