Log topic on ethereum side

contracts/src/Gateway.sol

@@ -460,7 +460,7 @@ contract Gateway is IGatewayBase, IGatewayV1, IGatewayV2, IInitializable, IUpgra
 
         bool success = v2_dispatch(message);
 
-        emit IGatewayV2.InboundMessageDispatched(message.nonce, success, rewardAddress);
+        emit IGatewayV2.InboundMessageDispatched(message.nonce, message.topic, success, rewardAddress);
     }
 
     function v2_dispatch(InboundMessageV2 calldata message) internal returns (bool) {

contracts/src/v2/IGateway.sol

@@ -25,7 +25,7 @@ interface IGatewayV2 {
      */
 
     // V2: Emitted when inbound message has been dispatched
-    event InboundMessageDispatched(uint64 indexed nonce, bool success, bytes32 rewardAddress);
+    event InboundMessageDispatched(uint64 indexed nonce, bytes32 topic, bool success, bytes32 rewardAddress);
 
     // v2 Emitted when an outbound message has been accepted for delivery to a Polkadot parachain
     event OutboundMessageAccepted(uint64 nonce, Payload payload);

contracts/src/v2/Types.sol

@@ -10,6 +10,8 @@ struct InboundMessage {
     bytes32 origin;
     // Message nonce
     uint64 nonce;
+    // XCM Topic
+    bytes32 topic;
     // Commands
     Command[] commands;
 }

contracts/test/GatewayV2.t.sol

@@ -206,22 +206,26 @@ contract GatewayV2Test is Test {
      * Message Verification
      */
     function testSubmitHappyPath() public {
+        bytes32 topic = keccak256("topic");
+
         // Expect the gateway to emit `InboundMessageDispatched`
         vm.expectEmit(true, false, false, true);
-        emit IGatewayV2.InboundMessageDispatched(1, true, relayerRewardAddress);
+        emit IGatewayV2.InboundMessageDispatched(1, topic, true, relayerRewardAddress);
 
         hoax(relayer, 1 ether);
         IGatewayV2(address(gateway)).v2_submit(
-            InboundMessageV2({origin: keccak256("666"), nonce: 1, commands: makeMockCommand()}),
+            InboundMessageV2({origin: keccak256("666"), nonce: 1, topic: topic, commands: makeMockCommand()}),
             proof,
             makeMockProof(),
             relayerRewardAddress
         );
     }
 
     function testSubmitFailInvalidNonce() public {
+        bytes32 topic = keccak256("topic");
+
         InboundMessageV2 memory message =
-            InboundMessageV2({origin: keccak256("666"), nonce: 1, commands: makeMockCommand()});
+            InboundMessageV2({origin: keccak256("666"), nonce: 1, topic: topic, commands: makeMockCommand()});
 
         hoax(relayer, 1 ether);
         IGatewayV2(address(gateway)).v2_submit(
@@ -236,8 +240,10 @@ contract GatewayV2Test is Test {
     }
 
     function testSubmitFailInvalidProof() public {
+        bytes32 topic = keccak256("topic");
+
         InboundMessageV2 memory message =
-            InboundMessageV2({origin: keccak256("666"), nonce: 1, commands: makeMockCommand()});
+            InboundMessageV2({origin: keccak256("666"), nonce: 1, topic: topic, commands: makeMockCommand()});
 
         MockGateway(address(gateway)).setCommitmentsAreVerified(false);
         vm.expectRevert(IGatewayBase.InvalidProof.selector);
@@ -345,18 +351,21 @@ contract GatewayV2Test is Test {
     }
 
     function testUnlockWethSuccess() public {
+        bytes32 topic = keccak256("topic");
+
         hoax(assetHubAgent);
         weth.deposit{value: 1 ether}();
 
         vm.expectEmit(true, false, false, true);
-        emit IGatewayV2.InboundMessageDispatched(1, true, relayerRewardAddress);
+        emit IGatewayV2.InboundMessageDispatched(1, topic, true, relayerRewardAddress);
 
         vm.deal(assetHubAgent, 1 ether);
         hoax(relayer, 1 ether);
         IGatewayV2(address(gateway)).v2_submit(
             InboundMessageV2({
                 origin: Constants.ASSET_HUB_AGENT_ID,
                 nonce: 1,
+                topic: topic,
                 commands: makeUnlockWethCommand(0.1 ether)
             }),
             proof,
@@ -366,6 +375,8 @@ contract GatewayV2Test is Test {
     }
 
     function testEncodeDecodeMessageV2() public {
+        bytes32 topic = keccak256("topic");
+
         UnlockNativeTokenParams memory params = UnlockNativeTokenParams({
             token: 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2,
             recipient: 0xEDa338E4dC46038493b885327842fD3E301CaB39,
@@ -376,7 +387,7 @@ contract GatewayV2Test is Test {
         commands[0] =
             CommandV2({kind: CommandKind.UnlockNativeToken, gas: 100_000, payload: encoded});
         InboundMessageV2 memory message =
-            InboundMessageV2({origin: bytes32(uint256(1000)), nonce: 1, commands: commands});
+            InboundMessageV2({origin: bytes32(uint256(1000)), nonce: 1, topic: topic, commands: commands});
         bytes memory rawBytes = abi.encode(message);
 
         //From OutboundQueueV2
@@ -409,15 +420,18 @@ contract GatewayV2Test is Test {
     }
 
     function testAgentCallContractSuccess() public {
+        bytes32 topic = keccak256("topic");
+
         vm.expectEmit(true, false, false, true);
-        emit IGatewayV2.InboundMessageDispatched(1, true, relayerRewardAddress);
+        emit IGatewayV2.InboundMessageDispatched(1, topic, true, relayerRewardAddress);
 
         vm.deal(assetHubAgent, 1 ether);
         hoax(relayer, 1 ether);
         IGatewayV2(address(gateway)).v2_submit(
             InboundMessageV2({
                 origin: Constants.ASSET_HUB_AGENT_ID,
                 nonce: 1,
+                topic: topic,
                 commands: makeCallContractCommand(0.1 ether)
             }),
             proof,