static/js/count-in.js (389) — bodies VERBATIM. app.js 8,223 → 7,913.
The third slice out of the strongly-connected core, and the first that WRITES
shared state rather than only reading it. #889's container is what makes it possible.
imports: loops (setLoop/loopA/loopB — a count-in inside an A-B loop must begin at
A), audio-el, player-state, host
hooks : _audioSeek, setPlayButtonState, _songEventPayload, togglePlay + a
jucePlayer getter
Nothing imports count-in back — app.js and section-practice both reach it through
the seam — so the graph stays acyclic.
app.js's autoplay path used to reach IN and set this module's credits timers itself
(_creditsTimer, _creditsHideOnPlay) and read _countingIn. It cannot now, and should
not have to, so the module exports the OPERATIONS instead — armCreditsHideOnPlay(),
scheduleCreditsHide(), holdCreditsThen(start), isCountingIn() — and owns its own
timer invariants. Third time this has happened (section-practice's resetSelection,
loops' state) and each time the constraint produced better code than was there
before: the module keeps its own promises instead of trusting a caller 6,000 lines
away to zero the right fields.
THE no-undef GATE FOUND FIVE MISSED MEMBERS, one at a time: showSongCreditsOverlay
and startSongCountIn (my name regex matched startCountIn, not startSongCountIn),
then _creditLineLabel, _CREDITS_MAX_MS, and _CREDIT_ROLE_VERBS. A call-graph closure
does not see a const table; only the undefined-symbol pass does.
AND A REAL TRAP: I computed _CREDIT_ROLE_VERBS's span against the ALREADY-MODIFIED
app.js and applied it to the clean one — the line numbers had drifted, so the slice
would have cut somewhere else entirely. Recomputed every span from the clean file
with acorn. Never carry line numbers across an edit.
VERIFIED. A/B against origin/main in two browsers with a real song: playback state,
the public feedBack.isPlaying mirror, audio position, cancel-count-in — IDENTICAL,
zero page errors. Unit coverage moved with the code: loop_restart's count-in
cancellation-token test and the 5 song_credits_overlay tests now read count-in.js;
loop_restart's sandbox gains a `host` object routed at its EXISTING stubs, so every
assertion is unchanged.
HONEST LIMIT: I could not make the count-in OVERLAY actually render headlessly —
its autoplay path needs a fresh-load _pendingAutostart that a scripted playSong()
never arms. Behaviour is identical to main on every probe and the unit tests cover
the logic, but the on-screen 1-2-3-4 and the credits card want a human look.
pytest 2396, node 1040/1040, ESLint 0 (no-cycle clean), tailwind clean, Codex 0.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
