chore: calc slippage percentage

packages/bridge-controller/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Add and export `calcSlippagePercentage`, a utility that calculates the absolute slippage percentage based on the adjusted return and the sent amount ([#5723](https://github.com/MetaMask/core/pull/5723)).
 - Error logs for invalid getQuote responses ([#5816](https://github.com/MetaMask/core/pull/5816))
 
 ### Changed

packages/bridge-controller/src/index.ts

@@ -103,7 +103,11 @@ export {
   isCrossChain,
 } from './utils/bridge';
 
-export { isValidQuoteRequest, formatEtaInMinutes } from './utils/quote';
+export {
+  isValidQuoteRequest,
+  formatEtaInMinutes,
+  calcSlippagePercentage,
+} from './utils/quote';
 
 export { calcLatestSrcBalance } from './utils/balance';
 

packages/bridge-controller/src/utils/quote.test.ts

@@ -14,6 +14,7 @@ import {
   calcSwapRate,
   calcCost,
   formatEtaInMinutes,
+  calcSlippagePercentage,
 } from './quote';
 import type {
   GenericQuoteRequest,
@@ -534,4 +535,37 @@ describe('Quote Metadata Utils', () => {
       expect(result.usd).toBeNull();
     });
   });
+
+  describe('calcSlippagePercentage', () => {
+    it.each([
+      ['100', null, '100', null, '0'],
+      ['95', '95', '100', '100', '5'],
+      ['98.3', '98.3', '100', '100', '1.7'],
+      [null, '100', null, '100', '0'],
+      [null, null, null, '100', null],
+      ['105', '105', '100', '100', '5'],
+    ])(
+      'calcSlippagePercentage: calculate slippage absolute value for received amount %p, usd %p, sent amount %p, usd %p to expected slippage %p',
+      (
+        returnValueInCurrency: string | null,
+        returnUsd: string | null,
+        sentValueInCurrency: string | null,
+        sentUsd: string | null,
+        expectedSlippage: string | null,
+      ) => {
+        const result = calcSlippagePercentage(
+          {
+            valueInCurrency: returnValueInCurrency,
+            usd: returnUsd,
+          },
+          {
+            amount: '1000',
+            valueInCurrency: sentValueInCurrency,
+            usd: sentUsd,
+          },
+        );
+        expect(result).toBe(expectedSlippage);
+      },
+    );
+  });
 });

packages/bridge-controller/src/utils/quote.ts

@@ -304,6 +304,38 @@ export const calcCost = (
       : null,
 });
 
+/**
+ * Calculates the slippage absolute value percentage based on the adjusted return and sent amount.
+ *
+ * @param adjustedReturn - Adjusted return value
+ * @param sentAmount - Sent amount value
+ * @returns the slippage in percentage
+ */
+export const calcSlippagePercentage = (
+  adjustedReturn: ReturnType<typeof calcAdjustedReturn>,
+  sentAmount: ReturnType<typeof calcSentAmount>,
+): string | null => {
+  const cost = calcCost(adjustedReturn, sentAmount);
+
+  if (cost.valueInCurrency && sentAmount.valueInCurrency) {
+    return new BigNumber(cost.valueInCurrency)
+      .div(sentAmount.valueInCurrency)
+      .times(100)
+      .abs()
+      .toString();
+  }
+
+  if (cost.usd && sentAmount.usd) {
+    return new BigNumber(cost.usd)
+      .div(sentAmount.usd)
+      .times(100)
+      .abs()
+      .toString();
+  }
+
+  return null;
+};
+
 export const formatEtaInMinutes = (
   estimatedProcessingTimeInSeconds: number,
 ) => {