refactor(studio): reassigned scalars → S container in src/state.js (step 3)

[byrongamatos]

What

Step 3 — the foundational state lift (like stems' S). All 66 module-scope _foo scalars move into a single exported S container in src/state.js; every _foo reference becomes S.foo (608 sites, underscore dropped). ES imports are read-only bindings, so export let x can't be reassigned from main.js — S.x = … can. main.js 2799 → 2731.

Rewrite safety

Audited before touching: no name is an object key or appears inside a string/comment literal — the "string-adjacent" grep hits were all ${} template expressions or function args. Scripted \b_foo\b → S.foo rewrite, then verified: 0 bare scalar refs, 0 double-prefix, parse-clean. Local objects (e.g. the parsed-JSON s.userName) correctly stayed put; only module scalars became S.*.

Move-only, no behaviour change. Keystone for extracting the functional modules (audio graph, waveform, recording, …) next.

Tests

node --test 7/7, pytest 25/25 (backend unaffected). Codex preflight: 0.

Big behavioral surface (all state access) — recommend an on-device pass (playback, mix, record) before/at merge.

Summary by CodeRabbit

• Refactor
  • Consolidated shared session, playback, UI, recording, and undo/redo state into a single exported container for easier cross-module updates.
  • Updated references to use the new container-based state shape (dropping module-scope underscore variables) with no expected behavior change.
• Documentation
  • Updated the changelog to reflect the ES-module migration step and the move-only, behavior-preserving rewrite.

[Copilot]

Pull request overview

This PR continues the studio’s ES-module migration by consolidating previously private, reassigned state into a single exported container object (S) in src/state.js, and updating src/main.js to read/write all state via S.* instead of _foo locals. This is intended to enable safe cross-module reassignment (since ES module imports are read-only bindings) and sets up the codebase for further modular extraction.

Changes:

• Introduces src/state.js exporting a single mutable S object containing all reassigned studio state.
• Refactors src/main.js to replace state locals (_foo) with S.foo across playback, mixing, undo, recording, punch-in, and highway recording paths.
• Documents the migration step in CHANGELOG.md.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/state.js	Adds exported S container holding the consolidated mutable studio state.
src/main.js	Switches all reassigned state access from _foo locals to S.foo and imports S.
CHANGELOG.md	Adds an entry describing ES-module migration step 3 (state lift to S).

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 5512c547-8660-46d8-b6c8-de31ed22265e

📥 Commits

Reviewing files that changed from the base of the PR and between 28c181d and f0a3fef.

📒 Files selected for processing (2)

• CHANGELOG.md
• src/state.js

✅ Files skipped from review due to trivial changes (1)

• CHANGELOG.md

🚧 Files skipped from review as they are similar to previous changes (1)

• src/state.js

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📝 Walkthrough

Walkthrough

This PR introduces a new src/state.js module exporting a shared mutable object S for application state previously held in module-scope scalars. CHANGELOG.md adds an entry documenting the migration as move-only with no behavior change.

Changes

Shared State Module Migration

Layer / File(s)	Summary
Shared state container and changelog entry src/state.js, CHANGELOG.md	Adds an exported S object consolidating former module-scope state variables and documents the migration as move-only in the changelog.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: moving reassigned scalars into the exported S container in src/state.js.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/es-module-state-container

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[coderabbitai]

🧹 Nitpick comments (1)

src/state.js (1)

5-94: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Optional: consider a JSDoc @typedef for S.

With 66 flat properties on a single mutable object, an editor/tsc-checked JSDoc typedef (e.g., /** @type {{isPlaying: boolean, ...}} */) would give autocomplete and catch typos at S.foo call sites across main.js, without requiring a TS migration.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/state.js` around lines 5 - 94, Add a JSDoc typedef for the exported S
state object in state.js so editors and tsc can infer its shape and catch
invalid S.foo usages. Define the full property structure alongside the S
declaration, keeping the existing runtime object unchanged, and make sure the
typedef covers the main mutable fields used throughout main.js such as playback,
mixState, recording, and highway-related properties.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@src/state.js`:
- Around line 5-94: Add a JSDoc typedef for the exported S state object in
state.js so editors and tsc can infer its shape and catch invalid S.foo usages.
Define the full property structure alongside the S declaration, keeping the
existing runtime object unchanged, and make sure the typedef covers the main
mutable fields used throughout main.js such as playback, mixState, recording,
and highway-related properties.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: b717d19a-7b21-46bb-87a7-b6917dcffaef

📥 Commits

Reviewing files that changed from the base of the PR and between fc76386 and 28c181d.

📒 Files selected for processing (3)

• CHANGELOG.md
• src/main.js
• src/state.js

[byrongamatos]

On the CodeRabbit nitpick (JSDoc @typedef for S): declining. It's marked optional/low-value, and with no tsc type-checking in CI it'd be 66 lines of hand-maintained boilerplate for editor-only autocomplete — and a drift risk (the typedef and the object would need to stay in sync by hand). The grouped comments on the S object already document each field. Happy to revisit if the repo ever adopts checkJs/tsc.