fix: never round percentage

[C4illin]

Summary by CodeRabbit

• Split Editing
  • Split percentages now retain precision during redistribution while displaying up to two decimal places.
  • Existing split percentages determine which shares are locked when the editor opens.
  • Click a sole remaining share to lock it and open editing.
  • Member names and avatars fall back to email-based labels when needed.
  • Split amounts use consistent-width displays.

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
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• Plan: Advanced
• Run ID: 3f7bdaa3-ef95-495e-8355-0b9003e21d63

📥 Commits

Reviewing files that changed from the base of the PR and between fe82484 and c717be2.

📒 Files selected for processing (2)

• src/components/RecurringExpenseForm.tsx
• src/components/SplitEditor.tsx

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📝 Walkthrough

Walkthrough

SplitEditor now uses generated user records, initializes locks from existing splits, and updates percentage redistribution, editing, and display. RecurringExpenseForm uses the generated user type for its members prop.

Changes

Split Editor Updates

Layer / File(s)	Summary
Member types and initial locks src/components/SplitEditor.tsx, src/components/RecurringExpenseForm.tsx	Both components use UsersResponse for members. SplitEditor initializes locks from included members and their existing percentages.
Share editing and display src/components/SplitEditor.tsx	Redistribution retains full precision. Percentages and totals display two decimal places. The sole remainder becomes a control that locks the member and opens editing. Member labels, fallbacks, and control sizing are updated.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to c717b

Split editing now keeps exact percentages internally and shows them to two decimals. It also restores locks from existing splits and adds email-based member labels. The member type change is compatible with every caller, and saving still accepts totals that are close to 100%. No merge-blocking issue was found.

Security Architecture Review

Security architecture risk: 🔵 Low · up to c717b

The changes remain within group expense editing, with no demonstrated increase in access or privileges. Share calculations retain unrounded remainders, while email-based display fallbacks change which identity information appears. Backend privacy enforcement and behavior during concurrent membership changes remain unverified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The examined change affects selected-group member presentation and expense-allocation inputs. Existing callers and explicit persistence payloads do not demonstrate additional service or credential authority. Enforcement against cross-group access remains outside the verified source coverage.

Trust Boundaries and Controls

• observed — Normal save buttons reject share totals differing from 100 by more than 0.1 percentage points. These are client-side usability and integrity checks, not evidence of backend authorization or authoritative allocation validation.

Resilience and Maintainability Implications

• observed — Exclusion removes the member’s lock, zeros its percentage, and redistributes the remainder; unlocking also redistributes. Editing the sole remainder can leave every included member locked, with unlocking providing a recovery path. Locks are initialized once and keyed by index; reconciliation during membership changes is not established.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title describes the main percentage change: calculations retain full precision instead of rounding internally.
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.

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Actionable comments posted: 2

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Inline comments:
Review comments at @src/lib/balances.ts:
- Around line 43-45: Update the divisor used in the expense-split calculation so
non-zero splits always divide by totalPct, including totals close to 100.
Preserve the existing owed calculation in the expenseSplits loop.
- Around line 64-68: Remove the eight-decimal rounding from `exactOre` in the
`members.map` allocation logic so distinct fractional öre remainders remain
distinct for largest-remainder ordering; preserve the existing floor and
remainder calculations.

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: 7d382e9f-5582-4d4b-a26e-8f7abcd86d98

📥 Commits

Reviewing files that changed from the base of the PR and between 825a12e and fe82484.

📒 Files selected for processing (2)

• src/components/SplitEditor.tsx
• src/lib/balances.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.