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Add writeMidiFile() with TEMPO/EVENTS/unrecognized-track emission#103

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Add writeMidiFile() with TEMPO/EVENTS/unrecognized-track emission#103
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@elicwhite elicwhite commented Apr 20, 2026

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First piece of the MIDI writer. Follow-ups add instrument/vocal track emission.

```ts
export function writeMidiFile(chart: ParsedChart): Uint8Array
```

Output track layout (Format 1 MIDI):

  • Track 0: TEMPO TRACK — `trackName` + `setTempo` + `timeSignature` meta events, all at absolute ticks converted to delta time at the end.
  • Track 1: EVENTS — `trackName` + section text events (unwrapped as `section name` to avoid YARG's `NormalizeTextEvent` stripping content containing `]`), `[end]` events, global events (bracket-wrapped when source was `.chart` so MIDI convention is followed), `[coda]` synthesized from `drumFreestyleSections[].isCoda` when not already in `unrecognizedEvents`.
  • Tracks 2..N: unrecognized MIDI tracks — verbatim pass-through with abs-tick → delta-tick conversion. Duplicate track names suffixed internally to keep the output trackMap unique.

`finalizeMidiTrack` shared helper handles the sort + absolute→delta conversion + `endOfTrack` append, with a type-priority tiebreaker for events at the same tick (trackName → timeSig → setTempo → noteOff → sysEx → noteOn → text/lyrics → other → endOfTrack). An optional `seq` field per `AbsoluteEvent` lets instrument-track emitters sequence paired events deterministically.

Deferred to follow-up PRs

  • `buildInstrumentTrack` (drum + guitar/ghl emission)
  • `buildVocalPartTrack` (PART VOCALS, HARM1/2/3, CopyDown)

Depends on

PRs #97 + #98 + #99 + #100 + #101 + #102 — stacked above.

@elicwhite elicwhite mentioned this pull request Apr 20, 2026
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@elicwhite elicwhite force-pushed the midi-writer-core branch 2 times, most recently from f8da23b to 0e82a25 Compare April 20, 2026 04:45
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@elicwhite elicwhite force-pushed the midi-writer-core branch 3 times, most recently from 3f8ca11 to 8f5478e Compare April 20, 2026 05:19
@elicwhite elicwhite mentioned this pull request Apr 20, 2026
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@elicwhite elicwhite force-pushed the midi-writer-core branch 6 times, most recently from 931507e to 206bb47 Compare April 21, 2026 16:51
@elicwhite
Add createEmptyChart() counterpart to parseChartAndIni
84b0e83 
Builds a minimal valid ParsedChart from scratch: default 480 resolution,
120 BPM at tick 0, 4/4 time signature at tick 0, empty tracks/sections/
metadata/vocal parts/unrecognized events. chartBytes defaults to an empty
Uint8Array (no source bytes), format defaults to 'chart', iniChartModifiers
to the library defaults.

Options let callers override resolution, bpm, timeSignature, and format.

Useful for programmatic chart generation (e.g. downstream code that builds
charts up from scratch rather than parsing source bytes).
@elicwhite
Add writeIniFile() for song.ini emission
75b92a6 
Serializes IniMetadata (Partial<typeof defaultMetadata> + extraIniFields)
back to song.ini text with:
- [song] header
- Known fields emitted in the canonical defaultMetadata order
- Undefined values skipped
- Booleans as True/False (Clone Hero convention)
- extraIniFields appended in insertion order
- CRLF line endings

Derives its field order from Object.keys(defaultMetadata) rather than
hardcoding a separate FIELD_ORDER list, so new fields added to
defaultMetadata automatically participate in writing.

Tests exercise writeIniFile only via round-trip through parseChartAndIni,
per reviewer feedback: build a metadata object, write it, re-parse, and
assert on parsedChart.metadata. No assertions about the serialized ini
text itself (CRLF, field order, True/False formatting, quoting) — those
are implementation details.
@elicwhite
Add writeChartFile() with Song/SyncTrack/Events/unrecognized-section …
78bd890 
…emission

Port of the non-instrument-track half of the chart writer into scan-chart:
- [Song] emits the subset of metadata the chart body supports (Name,
  Artist, Charter, Album, Genre, Year, Resolution, Offset, PreviewStart,
  Difficulty). Other fields live exclusively in song.ini.
- [SyncTrack] emits tempos as `B millibeats` and time signatures as
  `TS numerator [denominator-exponent]`, sorted by tick with TS before B
  at the same tick.
- [Events] emits section markers (wrapped as [section name] to survive
  the parser's greedy trailing-\] regex), end events, unrecognized global
  events (with bracket-stripping when source is .mid so round-trip to
  .chart emits naked text), and vocal phrase_start/phrase_end/lyric
  events from the normalized vocalTracks.parts.vocals.
- Unrecognized chart sections are re-emitted verbatim.

Instrument tracks ([ExpertSingle] etc.) land in a follow-up PR.
@elicwhite
writeChartFile: emit instrument track sections
914ea70 
Completes writeChartFile with per-track section emission:

- [ExpertSingle], [HardDrums], etc. named from instrument + difficulty.
- Drum tracks: base notes (N 0..4 or 0..5 for 5-lane), cymbal markers
  (N 66/67/68) only in fourLanePro, accent (N 34..38) and ghost (N 40..44)
  markers matching the emitted note's eventType, one N 109 flam per group,
  double kick as N 32 only.
- 5-lane round-trip: greenDrum+cymbal emits as N 4 (orange) while plain
  greenDrum stays at N 5; blueDrums coinciding with greenDrum+cymbal emit
  as N 5 to keep the parser's drumType detection on fiveLane.
- Fret/GHL tracks: notes via the 5-fret and 6-fret maps, tap as N 6,
  forceUnnatural (N 5) when the note's hopo/strum flag disagrees with
  the natural-HOPO state.
- Star power S 2, activation lanes S 64, flex lanes S 65/66, versus
  phrases S 0/1, solo sections as E 'solo'/'soloend' (tick + length - 1
  for soloend to round-trip).
- Per-track text events (including disco flip mix markers).
- Disco-flip state transitions per difficulty from red/yellow drum
  disco/discoNoflip flags → 'mix <diff> drums0[d|dnoflip]' text events.
- Coda events: if no 'coda' in unrecognizedEvents, synthesize from
  drumFreestyleSections where isCoda=true.
- hasForcedNotes backstop: if hasForcedNotes is set but no forceUnnatural
  emitted, append N 5 0 at a vacant tick in the first fret track to
  preserve the flag on round-trip.
@elicwhite
Add writeMidiFile() with TEMPO/EVENTS/unrecognized-track emission
96cb353 
Port of the core MIDI writer infrastructure:
- writeMidiFile(chart) entry point: builds a Format-1 MIDI and returns
  Uint8Array via midi-file's writeMidi
- TEMPO TRACK: trackName + setTempo (from chart.tempos) + timeSignature
  (from chart.timeSignatures), all at their absolute ticks
- EVENTS track: trackName + section text events (unwrapped so YARG's
  NormalizeTextEvent doesn't strip names containing ]) + [end] events +
  global events (bracket-wrap when source is .chart so MIDI output
  follows convention) + [coda] derived from drumFreestyleSections when
  not already present in unrecognizedEvents
- Unrecognized MIDI tracks: verbatim pass-through with abs-tick →
  delta-tick conversion; duplicate track names suffixed to keep the
  internal trackMap unique
- finalizeMidiTrack helper: sorts by tick with a type-priority
  tiebreaker, converts absolute ticks to delta times, appends endOfTrack

Instrument tracks (PART DRUMS, PART GUITAR, …) and vocal tracks
(PART VOCALS, HARM1/2/3) land in follow-up PRs.
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@elicwhite