From 782a94caa82d3e1493bb9af900fb52d8933993a1 Mon Sep 17 00:00:00 2001
From: Vasilis Xouris <vasileios.xouris@uniswap.org>
Date: Tue, 3 Dec 2024 12:54:50 -0800
Subject: [PATCH] fix: Keep fixed execution price for stable swaps in gas
 estimation

---
 .../tick-based-heuristic-gas-model.ts         | 34 ++++++++++++++++---
 src/util/chains.ts                            |  8 +++++
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/src/routers/alpha-router/gas-models/tick-based-heuristic-gas-model.ts b/src/routers/alpha-router/gas-models/tick-based-heuristic-gas-model.ts
index 992f43310..6db64310b 100644
--- a/src/routers/alpha-router/gas-models/tick-based-heuristic-gas-model.ts
+++ b/src/routers/alpha-router/gas-models/tick-based-heuristic-gas-model.ts
@@ -2,7 +2,12 @@ import { BigNumber } from '@ethersproject/bignumber';
 import { BaseProvider } from '@ethersproject/providers';
 import { ChainId, Price } from '@uniswap/sdk-core';
 import { Pool } from '@uniswap/v3-sdk';
-import { CurrencyAmount, log, WRAPPED_NATIVE_CURRENCY } from '../../../util';
+import {
+  CurrencyAmount,
+  log,
+  STABLE_COINS_BY_CHAIN_ID,
+  WRAPPED_NATIVE_CURRENCY
+} from '../../../util';
 import { calculateL1GasFeesHelper } from '../../../util/gas-factory-helpers';
 import { V3RouteWithValidQuote, V4RouteWithValidQuote } from '../entities';
 import {
@@ -165,13 +170,24 @@ export abstract class TickBasedHeuristicGasModelFactory<
       // A pool with the non quote token / ETH should not be required and errors should be handled separately
       if (nativeAmountPool) {
         // get current execution price (amountToken / quoteToken)
-        const executionPrice = new Price(
+        let executionPrice = new Price(
           routeWithValidQuote.amount.currency,
           routeWithValidQuote.quote.currency,
           routeWithValidQuote.amount.quotient,
           routeWithValidQuote.quote.quotient
         );
 
+        // If this is a stable pair, always use execution price of 1 for now.
+        // TODO: ROUTE-356 Use direct swap pool for swap execution price calculation.
+        if (this.routeIsStableCoinPair(chainId, routeWithValidQuote)) {
+          executionPrice = new Price(
+            routeWithValidQuote.amount.currency,
+            routeWithValidQuote.quote.currency,
+            routeWithValidQuote.amount.quotient,
+            routeWithValidQuote.amount.quotient,
+          );
+        }
+
         const inputIsToken0 =
           nativeAmountPool.token0.address == nativeCurrency.address;
         // ratio of input / native
@@ -179,14 +195,16 @@ export abstract class TickBasedHeuristicGasModelFactory<
           ? nativeAmountPool.token0Price
           : nativeAmountPool.token1Price;
 
-        const gasCostInTermsOfAmountToken = nativeAndAmountTokenPrice.quote(
+        // gasCostInTermsOfAmountToken = 29.487425 | 11.0
+        const gasCostInTermsOfAmountToken = nativeAndAmountTokenPrice.quote( // nativeAndAmountTokenPrice = 3554.58
           totalGasCostNativeCurrency
         ) as CurrencyAmount;
 
         // Convert gasCostInTermsOfAmountToken to quote token using execution price
         let syntheticGasCostInTermsOfQuoteToken: CurrencyAmount | null;
         try {
-          syntheticGasCostInTermsOfQuoteToken = executionPrice.quote(
+          // syntheticGasCostInTermsOfQuoteToken = 29 | 19 | 11
+          syntheticGasCostInTermsOfQuoteToken = executionPrice.quote( // executionPrice = 0.99
             gasCostInTermsOfAmountToken
           );
         } catch (err) {
@@ -258,6 +276,14 @@ export abstract class TickBasedHeuristicGasModelFactory<
     };
   }
 
+  protected routeIsStableCoinPair(chainId: ChainId, routeWithValidQuote: TRouteWithValidQuote): boolean {
+    const stableCoins = STABLE_COINS_BY_CHAIN_ID[chainId] || [];
+    return (
+      stableCoins.includes(routeWithValidQuote.amount.currency.wrapped.address.toLowerCase()) &&
+      stableCoins.includes(routeWithValidQuote.quote.currency.wrapped.address.toLowerCase())
+    );
+  }
+
   protected estimateGas(
     routeWithValidQuote: TRouteWithValidQuote,
     gasPriceWei: BigNumber,
diff --git a/src/util/chains.ts b/src/util/chains.ts
index dd0e1badf..91dd8dcc1 100644
--- a/src/util/chains.ts
+++ b/src/util/chains.ts
@@ -167,6 +167,14 @@ export enum NativeCurrencyName {
   AVALANCHE = 'AVAX',
 }
 
+export const STABLE_COINS_BY_CHAIN_ID: { [chainId: number]: string[] } = {
+  [ChainId.MAINNET]: [
+    '0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48', // USDC
+    '0x6b175474e89094c44da98b954eedeac495271d0f', // DAI
+    '0xdac17f958d2ee523a2206206994597c13d831ec7', // USDT
+  ],
+}
+
 export const NATIVE_NAMES_BY_ID: { [chainId: number]: string[] } = {
   [ChainId.MAINNET]: [
     'ETH',