feat(editor): tempo range operations — half/double/flatten/re-fit (tempo PR 8)

[ChrisBeWithYou]

What & why

Tempo-track PR 8 (charrette arch 2 / trans P5). Three operations over a selected barline range in Tempo Map mode — the tools for reshaping a whole passage's grid at once. Each declares its time contract (the charrette's declared-contract rule).

⚠ Two-parent stack. Depends on #226 (5a — the barline multi-selection this operates on) and #231 (PR 7 — the hardened _suggestFitPure the range re-fit extends with opts.toIdx). This PR is based on #231 with #226 merged in, so #226's selection code shows in the diff — review the final commit (tempo range operations …) for PR-8-only changes. After #226 and #231 squash-merge, rebase onto main: the diff becomes PR-8-only.

The three ops

• Half-time / Double-time the range — TempoGridCmd, so times HOLD (the audio positions and note seconds don't move; only the barline grid changes → the tempo halves or doubles).
  • _tempoHalveRangePure demotes every second downbeat (an odd bar count leaves the last bar unpaired — reported).
  • _tempoDoubleRangePure promotes the interior beat nearest each bar's time midpoint (a one-beat bar has nothing to split — skipped + reported).
• Flatten range to a steady tempo — TempoMapCmd, so times MOVE and the notes follow. _tempoFlattenRangePure re-times the beats between the two ends to uniform per-beat spacing, both ends pinned (no tail shift); interior locked barlines hold their time (the sub-range runs through _respaceWithLocksPure).
• Re-fit the range to onsets — _suggestFitPure gains opts.toIdx: the onset march stops cleanly at the range's last downbeat (stopDetail: 'bound'), never proposing past it. Pressing G with a multi-selection anchors at the range's first downbeat and bounds at its last; the accept path is unchanged.

Wired into the tempo-map context menu (the three rows appear when 2+ barlines are selected) and the Suggest (G) handler.

Verification

• npm test — 120 pass. New tests/tempo_range_ops.test.mjs (12): the range resolver; half/double keep every second fixed; half→double is identity on an even range; a one-beat bar is skipped; flatten's uniform interior + pinned ends + untouched tail + interior-lock hold; each command round-trips exec → undo → redo (flatten's note rides the retimed grid); the bounded re-fit never proposes past the range (and the unbounded one does).
• npm run lint — 0 errors (3 pre-existing ratchet warnings).
• Live on AC/DC — Back In Black: range re-fit → "Suggested a fit for the selected range (96 barlines)"; right-click ▸ Half-time → "merged 52 barlines — audio positions hold"; all three rows present; no page errors.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added Half-time, Double-time, and Flatten to steady tempo actions for selected tempo ranges.
  • Tempo suggestions can now be limited to a selected barline range.
  • Status messages indicate when suggestions apply only to the selected range.
• Bug Fixes
  • Improved consistency when regenerating bounded tempo suggestions.
• Tests
  • Added coverage for range operations, undo/redo behavior, note retiming, and bounded suggestions.

[coderabbitai]

📝 Walkthrough

Walkthrough

Tempo Map multi-selection now supports half-time, double-time, and flatten operations. Tempo suggestion fitting can also be constrained to the selected downbeat range, with option persistence during regeneration and coverage from unit and integration tests.

Changes

Tempo range editing

Layer / File(s)	Summary
Range operations and command wiring src/tempo.js, tests/tempo_range_ops.test.mjs	Adds selected-range detection, half-time, double-time, and flatten transformations, context-menu actions, undoable command execution, UI updates, and round-trip tests.
Selection-bounded tempo suggestions src/input.js, src/tempo-suggest.js, tests/tempo_range_ops.test.mjs, tests/tempo_suggest.test.mjs	Passes the selected downbeat range as toIdx, stops fitting at the bound, preserves options during regeneration, and validates fresh-compute option reset behavior.

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

Sequence Diagram(s)

sequenceDiagram
  participant Editor
  participant TempoSelection
  participant SuggestionEngine
  participant TempoGrid
  Editor->>TempoSelection: obtain selected downbeat range
  Editor->>SuggestionEngine: compute suggestions with range bound
  SuggestionEngine->>SuggestionEngine: stop proposals at toIdx
  SuggestionEngine-->>Editor: return bounded suggestions
  Editor->>TempoGrid: apply selected-range tempo operation
  TempoGrid-->>Editor: refresh tempo map and status

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Possibly related PRs

• got-feedBack/feedBack-plugin-editor#215: Extends the assisted tempo-mapping suggestion engine with the bounded suggestion behavior updated here.
• got-feedBack/feedBack-plugin-editor#226: Adds the Tempo Map multi-selection infrastructure used by these range operations and selection-bounded computations.

🚥 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: new tempo range operations and bounded re-fit behavior in the editor.
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/editor-tempo-range-ops

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[coderabbitai]

🧹 Nitpick comments (1)

tests/tempo_range_ops.test.mjs (1)

138-146: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Test title promises redo coverage the body doesn't exercise.

Title says "exec → undo → redo" but the test never calls S.history.doRedo() or asserts anything about it, unlike the half-time test above (125-136) which fully round-trips. Since the PR objective specifically claims "command undo/redo coverage," this gap should be closed to actually verify redo for TempoGridCmd via double-time.

✅ Proposed fix

     _tempoDoubleRange();
     assert.deepStrictEqual(dbTimes(S.beats), [0, 2, 4, 6, 8], 'split at midpoints');
     assert.strictEqual(S.history.undo.length, 1);
     S.history.doUndo();
     assert.deepStrictEqual(dbTimes(S.beats), [0, 4, 8], 'undo restores the barlines');
+    S.history.doRedo();
+    assert.deepStrictEqual(dbTimes(S.beats), [0, 2, 4, 6, 8], 'redo re-applies');
 });

🤖 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 `@tests/tempo_range_ops.test.mjs` around lines 138 - 146, Extend the test
titled “double-time round-trips exec → undo → redo” to call S.history.doRedo()
after verifying undo, then assert that S.beats returns to the doubled grid [0,
2, 4, 6, 8]. Keep the existing execution and undo assertions unchanged.

🤖 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 `@tests/tempo_range_ops.test.mjs`:
- Around line 138-146: Extend the test titled “double-time round-trips exec →
undo → redo” to call S.history.doRedo() after verifying undo, then assert that
S.beats returns to the doubled grid [0, 2, 4, 6, 8]. Keep the existing execution
and undo assertions unchanged.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 573799fc-b5cd-4f07-9a7a-02d11728df73

📥 Commits

Reviewing files that changed from the base of the PR and between 2716f97 and 2c05177.

📒 Files selected for processing (5)

• src/input.js
• src/tempo-suggest.js
• src/tempo.js
• tests/tempo_range_ops.test.mjs
• tests/tempo_suggest.test.mjs