refactor(editor): move arrangement management to src/arrangement.js (R2, step 30)

[byrongamatos]

What

Step 30 of the R2 module-extraction refactor: move arrangement-level operations out of src/main.js into a new native ES module src/arrangement.js.

Covers:

• Part rename — the undoable RenameArrangementCmd + the @pure:rename-arr cross-kind guard (a rename can't silently change the name-inferred instrument kind and strand notes).
• Remove arrangement.
• Add Drums — drum_tab.json import from a GP or MIDI file. This is the drum sibling of the keys/guitar imports moved in step 29, and chains into import.js's two shared post-import dialogs (_maybeOfferMidiTempoMap / _showDrumImportUnmappedModal).

How the seam is drawn

• 7 window.editor* entry points become named exports; main.js re-attaches them.
• 0 back-exports — nothing in main.js references a symbol defined here.
• Every dependency that stays in main.js (draw, updateStatus, updateArrangementSelector, effectiveAudioOffset) routes through host; all four are pre-existing hooks, so no new host wiring this step.
• arrangement.js imports the two dialog helpers from import.js — a clean module→module edge.
• tests/rename_part.test.mjs retargeted to slice @pure:rename-arr + RenameArrangementCmd from src/arrangement.js; it now injects a host stub because the command refreshes the selector via host.updateArrangementSelector.

main.js drops ~377 lines. 31 modules.

Verification

• 90/90 JS suites pass; ESLint gate clean (0 errors); strict no-undef clean on arrangement.js.
• Codex preflight: 0 correctness issues.
• New headless harness (verify_arrangement.py) drives a real Add-Drums import of a 76-byte channel-9 drums SMF (kick+snare, 120 BPM, 4/4) through the actual #editor-add-drums-gp input and editorDoAddDrums: asserts the 7 handlers bind, the single-arrangement remove is a guarded no-op, host.effectiveAudioOffset is wired (POSTed audio_offset == a seeded +5s), and the arrangement.js → import.js edge works (the MIDI tempo-map modal appears). Negative-checked by dropping a re-attach → harness throws.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added arrangement renaming with validation for compatible instrument layouts, valid names, and uniqueness.
  • Added arrangement removal with confirmation and automatic editor state updates.
  • Added “Add Drums” import support for Guitar Pro and MIDI files, including track selection and import guidance.
• Bug Fixes
  • Improved arrangement management reliability while preserving undo/redo behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8f701bf0-e144-467e-819d-50cf4ae1c84e

📥 Commits

Reviewing files that changed from the base of the PR and between fba9977 and c05db6d.

📒 Files selected for processing (3)

• src/arrangement.js
• src/main.js
• tests/rename_part.test.mjs

---

📝 Walkthrough

Walkthrough

Changes

Arrangement editor operations

Layer / File(s)	Summary
Guarded arrangement rename src/arrangement.js, tests/rename_part.test.mjs	Arrangement renaming now validates names and instrument compatibility, supports undo/redo, refreshes the selector, and uses the relocated pure-function test harness.
Arrangement removal state updates src/arrangement.js	Removal confirms eligibility, optionally calls the backend, resets history, updates arrangement state, clears selection, and redraws the editor.
Drum-track import and editor wiring src/arrangement.js, src/main.js	The Add Drums flow parses GP and MIDI files, imports selected tracks, updates drum state, triggers follow-up dialogs, and exposes handlers through module wiring.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Editor as editorDrumsFileSelected
  participant ImportAPI as import-list endpoint
  participant Commit as editorDoAddDrums
  participant DrumAPI as drum import endpoint
  participant State as S.drumTab and UI
  Editor->>ImportAPI: submit GP or MIDI file
  ImportAPI-->>Editor: return candidate tracks
  Editor->>Commit: select drum track
  Commit->>DrumAPI: submit selected track and offset
  DrumAPI-->>Commit: return drum_tab
  Commit->>State: store and sort hits, clear selection, refresh UI

Loading

Possibly related PRs

• got-feedBack/feedBack-plugin-editor#89: Related undo and history handling for arrangement removal and drum edits.
• got-feedBack/feedBack-plugin-editor#124: Related undoable arrangement rename behavior and command wiring.
• got-feedBack/feedBack-plugin-editor#155: Related rename test harness changes involving KEYS_PATTERN and pure rename helpers.

🚥 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 accurately reflects the main change: moving editor arrangement management into src/arrangement.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 refactor/r2-step30-arrangement

---

_{Comment @coderabbitai help to get the list of available commands.}

[Copilot]

Pull request overview

This PR continues the R2 module-extraction refactor by moving arrangement-level editor operations out of src/main.js into a dedicated ES module (src/arrangement.js), with main.js re-attaching the public window.editor* entry points and routing retained main.js dependencies through the existing host hook object.

Changes:

• Extracts arrangement rename (including the cross-kind @pure:rename-arr guard), arrangement removal, and Add-Drums import flow into src/arrangement.js.
• Updates src/main.js to import these new module exports and re-attach the corresponding window.editor* handlers.
• Retargets tests/rename_part.test.mjs to slice @pure:rename-arr and RenameArrangementCmd from src/arrangement.js, injecting a host stub for selector refresh.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tests/rename_part.test.mjs	Updates the test harness to read/extract the pure rename guard and command from src/arrangement.js, and stubs host.updateArrangementSelector.
src/main.js	Removes arrangement-management implementations and re-attaches arrangement-related window.editor* entry points to src/arrangement.js exports; keeps dependencies routed via host.
src/arrangement.js	New module containing rename/remove/add-drums logic, calling back into main.js through host and reusing shared import dialogs from import.js.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.