refactor!: implement AxelarExecutable and AxelarExecutableWithToken in ITS

contracts/InterchainTokenService.sol

@@ -44,7 +44,14 @@ contract InterchainTokenService is
     using AddressBytes for bytes;
     using AddressBytes for address;
 
-    IAxelarGMPGatewayWithToken public immutable gatewayAddress;
+    /**
+     * @dev Axelar GMP Gateway for cross-chain messaging.
+     * Two available approaches:
+     * 1. Pure GMP: Uses IAxelarGMPGateway to handle messaging without token transfers, compatible across Amplifier chains.
+     * 2. GMP with Token: Legacy functionality. Explicitly cast to IAxelarGMPGatewayWithToken when needed.
+     *    This approach only functions on chains that rely on Axelar consensus Connection.
+     */
+    IAxelarGMPGateway public immutable gateway;
     IAxelarGasService public immutable gasService;
     address public immutable interchainTokenFactory;
     bytes32 public immutable chainNameHash;
@@ -136,7 +143,7 @@ contract InterchainTokenService is
             gatewayCaller_ == address(0)
         ) revert ZeroAddress();
 
-        gatewayAddress = IAxelarGMPGatewayWithToken(gateway_);
+        gateway = IAxelarGMPGateway(gateway_);
         gasService = IAxelarGasService(gasService_);
         tokenManagerDeployer = tokenManagerDeployer_;
         interchainTokenDeployer = interchainTokenDeployer_;
@@ -383,7 +390,7 @@ contract InterchainTokenService is
             revert InvalidExpressMessageType(messageType);
         }
 
-        if (gatewayAddress.isCommandExecuted(commandId)) revert AlreadyExecuted();
+        if (gateway.isCommandExecuted(commandId)) revert AlreadyExecuted();
 
         address expressExecutor = msg.sender;
         bytes32 payloadHash = keccak256(payload);
@@ -637,7 +644,7 @@ contract InterchainTokenService is
     ) external onlyRemoteService(sourceChain, sourceAddress) whenNotPaused {
         bytes32 payloadHash = keccak256(payload);
 
-        if (!gatewayAddress.validateContractCall(commandId, sourceChain, sourceAddress, payloadHash)) revert NotApprovedByGateway();
+        if (!gateway.validateContractCall(commandId, sourceChain, sourceAddress, payloadHash)) revert NotApprovedByGateway();
 
         _execute(commandId, sourceChain, sourceAddress, payload, payloadHash);
     }
@@ -707,8 +714,10 @@ contract InterchainTokenService is
     function _checkPayloadAgainstGatewayData(bytes memory payload, string calldata tokenSymbol, uint256 amount) internal view {
         (, bytes32 tokenId, , , uint256 amountInPayload) = abi.decode(payload, (uint256, bytes32, uint256, uint256, uint256));
 
-        if (validTokenAddress(tokenId) != gatewayAddress.tokenAddresses(tokenSymbol) || amount != amountInPayload)
-            revert InvalidGatewayTokenTransfer(tokenId, payload, tokenSymbol, amount);
+        if (
+            validTokenAddress(tokenId) != IAxelarGMPGatewayWithToken(address(gateway)).tokenAddresses(tokenSymbol) ||
+            amount != amountInPayload
+        ) revert InvalidGatewayTokenTransfer(tokenId, payload, tokenSymbol, amount);
     }
 
     /**
@@ -930,8 +939,16 @@ contract InterchainTokenService is
     ) internal {
         bytes32 payloadHash = keccak256(payload);
 
-        if (!gatewayAddress.validateContractCallAndMint(commandId, sourceChain, sourceAddress, payloadHash, tokenSymbol, amount))
-            revert NotApprovedByGateway();
+        if (
+            !IAxelarGMPGatewayWithToken(address(gateway)).validateContractCallAndMint(
+                commandId,
+                sourceChain,
+                sourceAddress,
+                payloadHash,
+                tokenSymbol,
+                amount
+            )
+        ) revert NotApprovedByGateway();
 
         uint256 messageType;
         string memory originalSourceChain;
@@ -1237,8 +1254,4 @@ contract InterchainTokenService is
             emit ExpressExecutionFulfilled(commandId, sourceChain, sourceAddress, payloadHash, expressExecutor);
         }
     }
-
-    function gateway() external view override returns (IAxelarGMPGateway) {
-        return IAxelarGMPGateway(gatewayAddress);
-    }
 }

contracts/utils/GatewayCaller.sol

@@ -3,6 +3,7 @@
 pragma solidity ^0.8.0;
 
 import { IAxelarGasService } from '@axelar-network/axelar-gmp-sdk-solidity/contracts/interfaces/IAxelarGasService.sol';
+import { IAxelarGMPGateway } from '@axelar-network/axelar-gmp-sdk-solidity/contracts/interfaces/IAxelarGMPGateway.sol';
 import { IAxelarGMPGatewayWithToken } from '@axelar-network/axelar-gmp-sdk-solidity/contracts/interfaces/IAxelarGMPGatewayWithToken.sol';
 import { IGatewayCaller } from '../interfaces/IGatewayCaller.sol';
 
@@ -11,7 +12,7 @@ import { IGatewayCaller } from '../interfaces/IGatewayCaller.sol';
  * @dev This contract is used to handle cross-chain ITS calls via the Axelar gateway.
  */
 contract GatewayCaller is IGatewayCaller {
-    IAxelarGMPGatewayWithToken public immutable gateway;
+    IAxelarGMPGateway public immutable gateway;
     IAxelarGasService public immutable gasService;
 
     /**
@@ -20,7 +21,7 @@ contract GatewayCaller is IGatewayCaller {
      * @param gasService_ The address of the AxelarGasService contract
      */
     constructor(address gateway_, address gasService_) {
-        gateway = IAxelarGMPGatewayWithToken(gateway_);
+        gateway = IAxelarGMPGateway(gateway_);
         gasService = IAxelarGasService(gasService_);
     }
 
@@ -117,6 +118,6 @@ contract GatewayCaller is IGatewayCaller {
             }
         }
 
-        gateway.callContractWithToken(destinationChain, destinationAddress, payload, symbol, amount);
+        IAxelarGMPGatewayWithToken(address(gateway)).callContractWithToken(destinationChain, destinationAddress, payload, symbol, amount);
     }
 }

test/InterchainTokenServiceUpgradeFlow.js

@@ -19,7 +19,7 @@ const Create3Deployer = getContractJSON('Create3Deployer');
 const MINT_BURN = 4;
 
 describe('Interchain Token Service Upgrade Flow', () => {
-    let wallet, otherWallet, multisig;
+    let wallet, otherWallet, operator;
     let service, gateway, gasService;
     let tokenManagerDeployer, interchainTokenDeployer, tokenManager, tokenHandler, gatewayCaller;
     let interchainTokenFactoryAddress;
@@ -59,7 +59,7 @@ describe('Interchain Token Service Upgrade Flow', () => {
     }
 
     before(async () => {
-        [wallet, otherWallet, multisig] = await ethers.getSigners();
+        [wallet, otherWallet, operator] = await ethers.getSigners();
         governanceAddress = otherWallet.address;
 
         buffer = isHardhat ? 10 * 60 * 60 : 10;
@@ -85,7 +85,7 @@ describe('Interchain Token Service Upgrade Flow', () => {
         );
 
         axelarServiceGovernance = await axelarServiceGovernanceFactory
-            .deploy(gateway.address, governanceChain, governanceAddress, minimumTimeDelay, multisig.address)
+            .deploy(gateway.address, governanceChain, governanceAddress, minimumTimeDelay, operator.address)
             .then((d) => d.deployed());
 
         service = await deployInterchainTokenService(
@@ -220,7 +220,7 @@ describe('Interchain Token Service Upgrade Flow', () => {
             .to.emit(axelarServiceGovernance, 'MultisigApproved')
             .withArgs(proposalHash, target, calldata, nativeValue);
 
-        await expect(axelarServiceGovernance.connect(multisig).executeMultisigProposal(target, calldata, nativeValue))
+        await expect(axelarServiceGovernance.connect(operator).executeMultisigProposal(target, calldata, nativeValue))
             .to.emit(axelarServiceGovernance, 'MultisigExecuted')
             .withArgs(proposalHash, target, calldata, nativeValue)
             .and.to.emit(service, 'Upgraded')