[Subsidy] - Show fee breakdown adjusted for subsidy!

[W3stside]

Summary

Adjusts fee breakdown tooltip to show optimistically the fees discounted

Explanation of maths:

• we get fee amount from backend, we have to be optimistic and assume the fee was/is adjusted and returned properly factoring in discount.
• we take the returned feeAmount and multiply that amount by 1 + discount to get the preSubsidyFeeAmount and show that as the crossed out "previous fee" even tho that amount is never officially returned from the backend
• e.g user has 35% discount
• trading GNO <> WETH
• fee is shown as 0.0046 WETH (backend returned amount)
• to calculate preSubsidyFeeAmount we simply do: 0.0046 * 1.35 // 0.00621 (in atomic maths using bigint)

NO DISCOUNT

35% DISCOUNT

To Test

1. use an acct with no discount
2. check fee breakdown
3. switch to an account with discount
4. check fee breakdown
5. should match screenshots

[github-actions]

• 🔭 GP Swap: CoW Protocol v2 Swap UI

[W3stside]

Let's post merge review I'd like this in the Kaffeekränzchen

[elena-zh]

Changes LGTM.
However, I find some inconsistency in the tooltip values displaying. In this tooltip we have one label and one value in green. Maybe we should have Label+value in green if we want to highlight something?

[elena-zh]

Calculation seems to be a bit incorrect. In order to see an amount without a discount, it is better to divide an amount with a discount by amount (1-%discount/100). So in the case when discount is 25%, we need to divide an amount with discount by 0.75:

So in order to get fee with 25% discount of 2427.7727, original fee should be 3237,0303 (= 2427.7727/0.75)

[anxolin]

@W3stside I think your math is wrong.

Is not 1+fee, it's 1/(1-fee)

explanation:

[anxolin]

Also, verified with Anna, and she thinks is better to not show the older price at all. So at the end not even the calculation is needed.

Just showing the discounted amount (basically not show the original fee)