Fix: Remove redundant division in FEE_UI scaling logic

[Rav1Chauhan]

Addressed Issues:

Fixes #66

Fix: Correct UI fee scaling logic
Problem

FEE_UI_UNSCALED divided FEE_UI by 100 before applying decimalUnscaling.
If FEE_UI already represents a decimal percentage (e.g., 0.01 for 1%), this resulted in a 100× smaller fee being sent to the contract.

Solution

Removed the redundant / 100 and passed FEE_UI directly to decimalUnscaling.

Result

The UI fee is now correctly scaled according to SCALING_DECIMALS.

Screenshots/Recordings:

Not applicable.

This change affects internal fee scaling logic in:

djed-sdk/src/djed/tradeUtils.js

No UI components were modified.

Additional Notes:

Problem

FEE_UI_UNSCALED was calculated as:

decimalUnscaling((FEE_UI / 100).toString(), SCALING_DECIMALS)

If FEE_UI already represents a decimal percentage (e.g., 0.01 for 1%), dividing by 100 again reduces the effective fee by 100×.

Example:

FEE_UI = 0.01 (intended 1%)

(FEE_UI / 100) = 0.0001

Resulting contract-side fee = 0.01% instead of 1%

This leads to incorrect fee scaling at the protocol level.

Removed the redundant / 100 and passed FEE_UI directly into decimalUnscaling:

export const FEE_UI_UNSCALED = decimalUnscaling(
FEE_UI.toString(),
SCALING_DECIMALS
);
Result

UI fee is now correctly scaled according to SCALING_DECIMALS

Prevents undercharging by 100×

Aligns SDK behavior with protocol expectations

No breaking API changes

Checklist

• [x ] My PR addresses a single issue, fixes a single bug or makes a single improvement.
• [ x] My code follows the project's code style and conventions.
• If applicable, I have made corresponding changes or additions to the documentation.
• If applicable, I have made corresponding changes or additions to tests.
• [ x] My changes generate no new warnings or errors.
• [ x] I have joined the Stability Nexus's Discord server and I will share a link to this PR with the project maintainers there.
• [ x] I have read the Contribution Guidelines.
• [ x] Once I submit my PR, CodeRabbit AI will automatically review it and I will address CodeRabbit's comments.

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Summary by CodeRabbit

• Bug Fixes
  • Corrected a fee calculation issue in trading that was applying incorrect scaling to transaction fees. Users will now see accurate fee amounts reflected in their trades.

[coderabbitai]

📝 Walkthrough

Walkthrough

Modified the FEE_UI_UNSCALED constant initialization in tradeUtils.js by removing the explicit division by 100, allowing the decimalUnscaling function to handle the proper scaling based on the protocol's decimal configuration.

Changes

Cohort / File(s)	Summary
Fee Calculation Fix djed-sdk/src/djed/tradeUtils.js	Removed the redundant division by 100 from FEE_UI_UNSCALED initialization. The constant now directly passes FEE_UI to decimalUnscaling() instead of (FEE_UI / 100), correcting the double-division bug that caused a 100x fee discrepancy.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

🐰 A fee that was fractured by a hundred too much,
Now scales with precision—a delicate touch!
No more double-dividing what shouldn't divide,
The math hops along on the correct side! 🌟

🚥 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 accurately describes the main change: removing a redundant division operation in the FEE_UI scaling logic that was causing a 100× discrepancy.
Linked Issues check	✅ Passed	The PR directly addresses issue #66 by removing the redundant division by 100 in FEE_UI_UNSCALED calculation, matching the requirement to fix the fee-scaling logic so FEE_UI is passed directly to decimalUnscaling.
Out of Scope Changes check	✅ Passed	The change is narrowly scoped to the single line identified in issue #66 (line 17 of tradeUtils.js) with no additional or unrelated modifications to other files or functionality.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

🧹 Nitpick comments (1)

djed-sdk/src/djed/tradeUtils.js (1)

16-19: Add a regression test for the 1% UI-fee path.

Given this bug was subtle and high impact, please add a unit test that asserts Line 17 unscales FEE_UI = 0.01 correctly for SCALING_DECIMALS and that calculateTxFees(...).f_ui reflects 1% (not 0.01%).

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@djed-sdk/src/djed/tradeUtils.js` around lines 16 - 19, Add a regression unit
test that verifies FEE_UI_UNSCALED is computed correctly from FEE_UI = 0.01
using decimalUnscaling with SCALING_DECIMALS and that calculateTxFees(...).f_ui
returns 1% (0.01 as a fraction) not 0.0001; specifically, import FEE_UI,
SCALING_DECIMALS, FEE_UI_UNSCALED and decimalUnscaling, assert
decimalUnscaling(FEE_UI.toString(), SCALING_DECIMALS) equals FEE_UI_UNSCALED,
then call calculateTxFees with a representative amount and assert the returned
.f_ui equals the expected 0.01 (or equivalent fraction) to prevent the 0.01%
regression.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@djed-sdk/src/djed/tradeUtils.js`:
- Around line 16-19: Add a regression unit test that verifies FEE_UI_UNSCALED is
computed correctly from FEE_UI = 0.01 using decimalUnscaling with
SCALING_DECIMALS and that calculateTxFees(...).f_ui returns 1% (0.01 as a
fraction) not 0.0001; specifically, import FEE_UI, SCALING_DECIMALS,
FEE_UI_UNSCALED and decimalUnscaling, assert decimalUnscaling(FEE_UI.toString(),
SCALING_DECIMALS) equals FEE_UI_UNSCALED, then call calculateTxFees with a
representative amount and assert the returned .f_ui equals the expected 0.01 (or
equivalent fraction) to prevent the 0.01% regression.

---

ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 509e7d3 and 194e394.

📒 Files selected for processing (1)

• djed-sdk/src/djed/tradeUtils.js