Fix APR math in nextRevenuePoolSettleApr

[latent-9]

nextRevenuePoolSettleApr in sdk/src/math/insurance.ts has two bugs:

1. revenuePoolBN.muln(settlesPerYear).muln(payoutRatio) with payoutRatio = 0.1. BN.muln does not multiply by a fraction; it multiplies each limb and masks, so a fractional argument yields garbage rather than value * 0.1. For example new BN(1_000_000_000).muln(0.1) returns 73156454, not 100000000 (about 27 percent off). Since payoutRatio is the constant 0.1, this is integer divn(10).

2. amount is declared optional (amount?: BN), but vaultBalance.add(amount) is called unconditionally, so add(undefined) throws when a caller omits it. Defaulting a missing delta to ZERO preserves the intended behavior.

The function is exported from the SDK (export * from './math/insurance'), so both reach downstream consumers.

Summary by CodeRabbit

• Bug Fixes
  • Improved revenue pool settlement APR calculations for more accurate payout projections.
  • Prevented missing optional amounts from causing invalid APR results.
  • Updated APR calculations to use integer-based payout handling for greater consistency.
  • Improved the reliability of projected revenue and vault balance calculations when no additional amount is provided.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between ecacdf0 and 1cb9f78.

📒 Files selected for processing (1)

• sdk/src/math/insurance.ts

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

• sdk/src/math/insurance.ts

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Walkthrough

The insurance APR calculation now divides projected revenue by an integer payout denominator. The optional amount parameter defaults to zero before balance checks and APR calculation.

Changes

Insurance APR calculation

Layer / File(s)	Summary
APR calculation and amount handling sdk/src/math/insurance.ts	The calculation uses an integer payout denominator. The optional amount parameter defaults to ZERO before balance checks and APR calculation.

Estimated code review effort: 2 (Simple) | ~5 minutes

Poem

A rabbit checks the payout line,
With integer steps, the sums align.
No undefined hops astray,
Zero starts the APR day.
Thump, thump—clean math leads the way!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	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 clearly and concisely identifies the primary change to APR calculations in nextRevenuePoolSettleApr.
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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[coderabbitai]

🧹 Nitpick comments (1)

sdk/src/math/insurance.ts (1)

20-20: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Add regression tests for both APR fixes.

Cover the non-zero payout path and the omitted amount path. Assert that payout is divided by 10 and that amount === undefined uses vaultBalance without throwing. Also cover the zero-total-balance case.

Also applies to: 37-43

🤖 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 `@sdk/src/math/insurance.ts` at line 20, Add regression tests for the APR logic
near payoutRatioDenominator and the related amount-handling path: verify
non-zero payouts are divided by 10, omitted amount defaults to vaultBalance
without throwing, and zero total balance is handled correctly.

🤖 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 `@sdk/src/math/insurance.ts`:
- Line 20: Add regression tests for the APR logic near payoutRatioDenominator
and the related amount-handling path: verify non-zero payouts are divided by 10,
omitted amount defaults to vaultBalance without throwing, and zero total balance
is handled correctly.

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

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Run ID: e57f5d33-37ed-435c-8586-3f1bc84a88a5

📥 Commits

Reviewing files that changed from the base of the PR and between 13e8e9b and ecacdf0.

📒 Files selected for processing (1)

• sdk/src/math/insurance.ts