fix(transfer-intrabank): correct floating-point truncation in amount display

[bhuvan-somisetty]

The recent payee card shows the last amount you sent to a beneficiary — and for a lot of common amounts, it was showing the wrong value. ₹5.99 appears as ₹5.98. ₹99.99 appears as ₹99.98. ₹10.30 appears as ₹10.29. In a payments app, seeing a different amount than what you actually sent is genuinely alarming.

The root cause is a classic floating-point pitfall. The old code computed the decimal part like this:

val wholePart = amount.toLong()
val decimalPart = ((amount - wholePart) * 100).toInt()

The problem: 5.99 - 5 in floating-point is not 0.99 — it's 0.9899999999999999. Multiply that by 100 and you get 98.99.... Calling .toInt() truncates toward zero, so you get 98 instead of 99. The display shows 5.98.

This affects any amount where the decimal part has a negative epsilon in its binary representation, which includes most .x9 endings and many others. It's unpredictable from the user's perspective, which makes it feel like data corruption.

The fix avoids floating-point subtraction entirely. Instead of splitting the number and computing the decimal part through subtraction, we multiply the whole amount by 100, round to the nearest integer, and then use integer division and modulo:

val cents = (amount * 100).roundToInt()
val wholePart = cents / 100
val decimalPart = cents % 100

Multiplying first keeps the rounding error small enough that roundToInt() always lands on the correct cent value.

Amount	Before	After
5.99	5.98	5.99
99.99	99.98	99.99
10.30	10.29	10.30
63,823.00	63,823.00	63,823.00

Verified by tracing through the arithmetic manually for the failing cases and confirming the fixed output matches the expected display.

Summary by CodeRabbit

• Bug Fixes
  • Improved how transfer amounts are rounded and displayed in the recent payee card.
  • Amounts now show more consistent two-decimal formatting, reducing edge cases where values could appear slightly off due to rounding.

[coderabbitai]

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: f318d00c-0fb9-488d-8714-71e92a5a61e2

📥 Commits

Reviewing files that changed from the base of the PR and between 8540194 and 1d3e1db.

📒 Files selected for processing (1)

• feature/transfer-intrabank/src/commonMain/kotlin/org/mifospay/feature/transfer/intrabank/hub/components/RecentPayeeCard.kt

📝 Walkthrough

Walkthrough

The formatAmount function in RecentPayeeCard.kt is updated to compute cents by rounding the amount multiplied by 100, then deriving the whole and decimal parts from that rounded value, replacing the prior truncation-based derivation.

Changes

Amount Formatting Precision

Layer / File(s)	Summary
Cent-based amount formatting feature/transfer-intrabank/.../RecentPayeeCard.kt	Imports kotlin.math.roundToInt and refactors formatAmount to round the amount to cents before deriving whole and decimal parts, replacing the previous truncation-based logic.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Suggested reviewers: therajanmaurya

🚥 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 fix: correcting amount display truncation in intrabank transfer payees.
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 unit tests (beta)

• Create PR with unit tests

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🧹 Nitpick comments (1)

feature/transfer-intrabank/src/commonMain/kotlin/org/mifospay/feature/transfer/intrabank/hub/components/RecentPayeeCard.kt (1)

128-139: 🎯 Functional Correctness | 🔵 Trivial | 💤 Low value

Rounding fix correctly addresses the truncation bug.

The cent-based rounding via roundToInt() correctly resolves the ₹5.99/₹99.99/₹10.30 display issue described in the PR objective, since it rounds before splitting rather than truncating a raw double subtraction.

One minor note: cents is derived from amount * 100 as an Int, which overflows above ~21.4 million currency units. Given this is a recent-payee transfer amount, this is unlikely in practice, but using roundToLong() would remove the ceiling entirely at negligible cost.

♻️ Optional hardening

-    val cents = (amount * 100).roundToInt()
-    val wholePart = cents / 100
-    val decimalPart = cents % 100
+    val cents = (amount * 100).roundToLong()
+    val wholePart = cents / 100
+    val decimalPart = cents % 100

🤖 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
`@feature/transfer-intrabank/src/commonMain/kotlin/org/mifospay/feature/transfer/intrabank/hub/components/RecentPayeeCard.kt`
around lines 128 - 139, The amount formatting in formatAmount currently uses
roundToInt() into an Int, which can overflow for very large transfer values.
Update the cents calculation to use a wider integer type in
RecentPayeeCard.formatAmount so the rounding fix remains safe for large amounts,
while keeping the same whole-part/decimal-part formatting behavior.

🤖 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
`@feature/transfer-intrabank/src/commonMain/kotlin/org/mifospay/feature/transfer/intrabank/hub/components/RecentPayeeCard.kt`:
- Around line 128-139: The amount formatting in formatAmount currently uses
roundToInt() into an Int, which can overflow for very large transfer values.
Update the cents calculation to use a wider integer type in
RecentPayeeCard.formatAmount so the rounding fix remains safe for large amounts,
while keeping the same whole-part/decimal-part formatting behavior.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 3229857e-c9ca-4827-bd28-bf87a04d16eb

📥 Commits

Reviewing files that changed from the base of the PR and between 78d468b and 8540194.

📒 Files selected for processing (1)

• feature/transfer-intrabank/src/commonMain/kotlin/org/mifospay/feature/transfer/intrabank/hub/components/RecentPayeeCard.kt