Add balanceDiff on simulate bundle endpoint

apps/api/src/app/routes/__chainId/simulation/simulateBundle.ts

@@ -20,7 +20,7 @@ const successSchema = {
   type: 'array',
   items: {
     type: 'object',
-    required: ['status', 'id', 'link'],
+    required: ['status', 'id', 'link', 'cumulativeBalancesDiff'],
     additionalProperties: false,
     properties: {
       status: {
@@ -38,6 +38,17 @@ const successSchema = {
         description: 'Link to the transaction on Tenderly.',
         type: 'string',
       },
+      cumulativeBalancesDiff: {
+        title: 'Balances Diff',
+        description: 'Changes in balances of the token holders.',
+        type: 'object',
+        additionalProperties: {
+          type: 'object',
+          additionalProperties: {
+            type: 'string',
+          },
+        },
+      },
     },
   },
 } as const satisfies JSONSchema;

apps/api/src/main.ts

@@ -17,7 +17,7 @@ const logger = pino({
 });
 
 const host = process.env.HOST ?? 'localhost';
-const port = process.env.PORT ? Number(process.env.PORT) : 3000;
+const port = process.env.PORT ? Number(process.env.PORT) : 3001;
 
 // Instantiate Fastify with some config
 export const server = Fastify({

libs/repositories/src/SimulationRepository/SimulationRepository.ts

@@ -13,6 +13,9 @@ export interface SimulationData {
   link: string;
   status: boolean;
   id: string;
+  // { [address: string]: { [token: string]: balanceDiff: string } }
+  // example: { '0x123': { '0x456': '100', '0xabc': '-100' } }
+  cumulativeBalancesDiff: Record<string, Record<string, string>>;
 }
 
 export const simulationRepositorySymbol = Symbol.for('SimulationRepository');

libs/repositories/src/SimulationRepository/SimulationRepositoryTenderly.ts

@@ -1,5 +1,6 @@
 import { SupportedChainId } from '@cowprotocol/shared';
 import {
+  AssetChange,
   SimulationError,
   TenderlyBundleSimulationResponse,
   TenderlySimulatePayload,
@@ -15,6 +16,7 @@ import {
   SimulationInput,
   SimulationRepository,
 } from './SimulationRepository';
+import { BigNumber } from 'ethers';
 
 export const tenderlyRepositorySymbol = Symbol.for('TenderlyRepository');
 
@@ -48,17 +50,70 @@ export class SimulationRepositoryTenderly implements SimulationRepository {
       return null;
     }
 
-    // TODO: Add ERC20 state diffs
-    return response.simulation_results.map(({ simulation }) => ({
-      status: simulation.status,
-      id: simulation.id,
-      link: getTenderlySimulationLink(simulation.id),
-    }));
+    const balancesDiff = this.buildBalancesDiff(
+      response.simulation_results.map(
+        (result) => result.transaction.transaction_info.asset_changes || []
+      )
+    );
+
+    return response.simulation_results.map((simulation_result, i) => {
+      return {
+        status: simulation_result.simulation.status,
+        id: simulation_result.simulation.id,
+        link: getTenderlySimulationLink(simulation_result.simulation.id),
+        cumulativeBalancesDiff: balancesDiff[i],
+      };
+    });
   }
 
   checkBundleSimulationError(
     response: TenderlyBundleSimulationResponse | SimulationError
   ): response is SimulationError {
     return (response as SimulationError).error !== undefined;
   }
+
+  buildBalancesDiff(
+    assetChangesList: AssetChange[][]
+  ): Record<string, Record<string, string>>[] {
+    const cumulativeBalancesDiff: Record<string, Record<string, string>> = {};
+
+    return assetChangesList.map((assetChanges) => {
+      assetChanges.forEach((change) => {
+        const { token_info, from, to, raw_amount } = change;
+        const { contract_address } = token_info;
+
+        // Helper function to update balance
+        const updateBalance = (
+          address: string,
+          tokenSymbol: string,
+          changeAmount: string
+        ) => {
+          if (!cumulativeBalancesDiff[address]) {
+            cumulativeBalancesDiff[address] = {};
+          }
+          if (!cumulativeBalancesDiff[address][tokenSymbol]) {
+            cumulativeBalancesDiff[address][tokenSymbol] = '0';
+          }
+
+          const currentBalance = BigNumber.from(
+            cumulativeBalancesDiff[address][tokenSymbol]
+          );
+          const changeValue = BigNumber.from(changeAmount);
+          const newBalance = currentBalance.add(changeValue);
+
+          cumulativeBalancesDiff[address][tokenSymbol] = newBalance.toString();
+        };
+
+        if (from) {
+          updateBalance(from, contract_address, `-${raw_amount}`);
+        }
+
+        if (to) {
+          updateBalance(to, contract_address, raw_amount);
+        }
+      });
+
+      return { ...cumulativeBalancesDiff };
+    });
+  }
 }

libs/repositories/src/SimulationRepository/SimulationrepositoryTenderly.test.ts

@@ -7,6 +7,7 @@ import {
   TENDERLY_ORG_NAME,
   TENDERLY_PROJECT_NAME,
 } from '../datasources/tenderlyApi';
+import { AssetChange } from './tenderlyTypes';
 
 // Transfering ETH from WETH to NULL ADDRESS
 const TENDERLY_SIMULATION = {
@@ -45,7 +46,7 @@ describe('SimulationRepositoryTenderly', () => {
     expect(TENDERLY_PROJECT_NAME).toBeDefined();
   });
 
-  describe('getTopTokenHolders', () => {
+  describe('postBundleSimulation', () => {
     it('should return simulation data for success simulation', async () => {
       const tenderlySimulationResult =
         await tenderlyRepository.postBundleSimulation(
@@ -80,4 +81,184 @@ describe('SimulationRepositoryTenderly', () => {
       expect(tenderlySimulationResult?.[0].status).toBeFalsy();
     }, 100000);
   });
+  describe('buildBalancesDiff', () => {
+    it('should correctly process a single asset change', () => {
+      const input: AssetChange[][] = [
+        [
+          {
+            token_info: {
+              standard: 'ERC20',
+              type: 'TOKEN',
+              contract_address: '0x123',
+              symbol: 'TEST',
+              name: 'Test Token',
+              logo: 'test.png',
+              decimals: 18,
+              dollar_value: '1.00',
+            },
+            type: 'TRANSFER',
+            from: 'address1',
+            to: 'address2',
+            amount: '100',
+            raw_amount: '100000000000000000000',
+          },
+        ],
+      ];
+
+      const expected = [
+        {
+          address1: {
+            '0x123': '-100000000000000000000',
+          },
+          address2: {
+            '0x123': '100000000000000000000',
+          },
+        },
+      ];
+
+      expect(tenderlyRepository.buildBalancesDiff(input)).toEqual(expected);
+    });
+
+    it('should correctly process multiple asset changes', () => {
+      const input: AssetChange[][] = [
+        [
+          {
+            token_info: {
+              standard: 'ERC20',
+              type: 'TOKEN',
+              contract_address: '0x123',
+              symbol: 'TEST',
+              name: 'Test Token',
+              logo: 'test.png',
+              decimals: 18,
+              dollar_value: '1.00',
+            },
+            type: 'TRANSFER',
+            from: 'address1',
+            to: 'address2',
+            amount: '100',
+            raw_amount: '100000000000000000000',
+          },
+        ],
+        [
+          {
+            token_info: {
+              standard: 'ERC20',
+              type: 'TOKEN',
+              contract_address: '0x456',
+              symbol: 'TEST2',
+              name: 'Test Token 2',
+              logo: 'test2.png',
+              decimals: 18,
+              dollar_value: '2.00',
+            },
+            type: 'TRANSFER',
+            from: 'address2',
+            to: 'address3',
+            amount: '50',
+            raw_amount: '50000000000000000000',
+          },
+        ],
+      ];
+
+      const expected = [
+        {
+          address1: {
+            '0x123': '-100000000000000000000',
+          },
+          address2: {
+            '0x123': '100000000000000000000',
+          },
+        },
+        {
+          address1: {
+            '0x123': '-100000000000000000000',
+          },
+          address2: {
+            '0x123': '100000000000000000000',
+            '0x456': '-50000000000000000000',
+          },
+          address3: {
+            '0x456': '50000000000000000000',
+          },
+        },
+      ];
+
+      expect(tenderlyRepository.buildBalancesDiff(input)).toEqual(expected);
+    });
+
+    it('should handle empty input', () => {
+      const input: AssetChange[][] = [];
+      expect(tenderlyRepository.buildBalancesDiff(input)).toEqual([]);
+    });
+
+    it('should handle input with empty asset changes', () => {
+      const input: AssetChange[][] = [[], []];
+      expect(tenderlyRepository.buildBalancesDiff(input)).toEqual([{}, {}]);
+    });
+
+    it('should correctly handle cumulative changes', () => {
+      const input: AssetChange[][] = [
+        [
+          {
+            token_info: {
+              standard: 'ERC20',
+              type: 'TOKEN',
+              contract_address: '0x123',
+              symbol: 'TEST',
+              name: 'Test Token',
+              logo: 'test.png',
+              decimals: 18,
+              dollar_value: '1.00',
+            },
+            type: 'TRANSFER',
+            from: 'address1',
+            to: 'address2',
+            amount: '100',
+            raw_amount: '100000000000000000000',
+          },
+        ],
+        [
+          {
+            token_info: {
+              standard: 'ERC20',
+              type: 'TOKEN',
+              contract_address: '0x123',
+              symbol: 'TEST',
+              name: 'Test Token',
+              logo: 'test.png',
+              decimals: 18,
+              dollar_value: '1.00',
+            },
+            type: 'TRANSFER',
+            from: 'address2',
+            to: 'address1',
+            amount: '50',
+            raw_amount: '50000000000000000000',
+          },
+        ],
+      ];
+
+      const expected = [
+        {
+          address1: {
+            '0x123': '-100000000000000000000',
+          },
+          address2: {
+            '0x123': '100000000000000000000',
+          },
+        },
+        {
+          address1: {
+            '0x123': '-50000000000000000000',
+          },
+          address2: {
+            '0x123': '50000000000000000000',
+          },
+        },
+      ];
+
+      expect(tenderlyRepository.buildBalancesDiff(input)).toEqual(expected);
+    });
+  });
 });

libs/repositories/src/SimulationRepository/tenderlyTypes.ts

@@ -284,6 +284,27 @@ interface TransactionInfo {
   raw_state_diff: null;
   console_logs: null;
   created_at: Date;
+  // Note: manually added
+  asset_changes?: AssetChange[];
+}
+
+// Note: manually added
+export interface AssetChange {
+  token_info: {
+    standard: string;
+    type: string;
+    contract_address: string;
+    symbol: string;
+    name: string;
+    logo: string;
+    decimals: number;
+    dollar_value: string;
+  };
+  type: string;
+  from?: string;
+  to?: string;
+  amount: string;
+  raw_amount: string;
 }
 
 interface StackTrace {