fix(nexchange): normalize swap native amounts to integers

[samholmes]

N.exchange can return decimal amounts with more precision than the target asset supports, which leaks fractional values into native amount fields.

Rounding to integer atomic units in this plugin keeps spend targets and saved swap metadata valid for Edge amount expectations.

CHANGELOG

Does this branch warrant an entry to the CHANGELOG?

• Yes
• No

Dependencies

none

Description

none

---

Note

Medium Risk
Touches swap amount calculation used to build spendTargets and saved swap metadata; incorrect rounding could cause under/over-payment or mismatched expectations. Change is small and uses conservative floor-to-integer behavior to avoid fractional native amounts.

Overview
Normalizes N.exchange order deposit_amount/withdraw_amount conversions to integer native (atomic) units by applying floor(..., 0) after denominationToNative.

This prevents fractional native amounts (from provider over-precision) from leaking into spendTargets and persisted swap fromAsset/toAsset amounts.

^{Reviewed by Cursor Bugbot for commit 6acb8fd. Bugbot is set up for automated code reviews on this repo. Configure here.}

---

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Using round instead of floor can overstate amounts
  • Replaced round with floor for native amount conversion to prevent overstating amounts, aligning with the established convention in godex.ts and swapuz.ts.

Or push these changes by commenting:

@cursor push 5f71b513f5

Preview (5f71b513f5)

diff --git a/src/swap/central/nexchange.ts b/src/swap/central/nexchange.ts
--- a/src/swap/central/nexchange.ts
+++ b/src/swap/central/nexchange.ts
@@ -1,4 +1,4 @@
-import { gt, lt, round } from 'biggystring'
+import { floor, gt, lt } from 'biggystring'
 import {
   asArray,
   asDate,
@@ -416,8 +416,8 @@
     )
     // This provider may return more decimal places than the token supports.
     // Native amounts must be integer atomic units.
-    const amountExpectedFromNative = round(amountExpectedFromNativeRaw, 0)
-    const amountExpectedToNative = round(amountExpectedToNativeRaw, 0)
+    const amountExpectedFromNative = floor(amountExpectedFromNativeRaw, 0)
+    const amountExpectedToNative = floor(amountExpectedToNativeRaw, 0)
 
     const memos: EdgeMemo[] =
       order.deposit_address_extra_id == null ||

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^{Reviewed by Cursor Bugbot for commit 0c99910. Configure here.}