fix: account for msgSender for metaTxn is used with multicall

Author: hzhu

src/index.ts

@@ -127,12 +127,16 @@ export async function parseSwap({
     const takerForGaslessApprovalSwap =
       settlerArgs[0].recipient.toLowerCase() as Address;
 
+    const msgSender = settlerArgs[3];
+
     const nativeAmountToTaker = calculateNativeTransfer(trace, {
       recipient: takerForGaslessApprovalSwap,
     });
 
     if (nativeAmountToTaker === "0") {
-      output = output = logs[logs.length - 1];
+      [output] = logs.filter(
+        (log) => log.to.toLowerCase() === msgSender.toLowerCase()
+      );
     } else {
       output = {
         symbol: NATIVE_SYMBOL_BY_CHAIN_ID[chainId],

src/tests/index.test.ts

@@ -329,6 +329,37 @@ test("parse a gasless swap on Base (DAI for USDC)", async () => {
   });
 });
 
+// https://basescan.org/tx/0xb1ac9977d28e750add3b1a1ebdc95e56a51a9af7fc3d66fa7c011686eac455e6
+test("parse a gasless swap on Base (USDC for BRETT) via metaTxn multicall", async () => {
+  const publicClient = createPublicClient({
+    chain: base,
+    transport: http(
+      `https://base-mainnet.g.alchemy.com/v2/${process.env.ALCHEMY_API_KEY}`
+    ),
+  }) as PublicClient<Transport, Chain>;
+
+  const transactionHash =
+    "0xb1ac9977d28e750add3b1a1ebdc95e56a51a9af7fc3d66fa7c011686eac455e6";
+
+  const result = await parseSwap({
+    publicClient,
+    transactionHash,
+  });
+
+  expect(result).toEqual({
+    tokenIn: {
+      symbol: "USDC",
+      amount: "1000",
+      address: "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
+    },
+    tokenOut: {
+      symbol: "BRETT",
+      amount: "18260.873189681406728218",
+      address: "0x532f27101965dd16442E59d40670FaF5eBB142E4",
+    },
+  });
+});
+
 // https://basescan.org/tx/0xa09cb1606e30c3aed8a842723fd6c23cecd838a59f750ab3dbc5ef2c7486e696
 test("parse a swap on Base (USDC for DAI)", async () => {
   const publicClient = createPublicClient({