ERC20 Bridging pre-tests

script/DeployChildContracts.s.sol

@@ -17,7 +17,6 @@ contract DeployChildContracts is Script {
     function run() public {
         uint256 deployerPrivateKey = vm.envUint("CHILD_PRIVATE_KEY");
         address childGateway = vm.envAddress("CHILD_GATEWAY_ADDRESS");
-        address childGasService = vm.envAddress("CHILD_GAS_SERVICE_ADDRESS"); // Not yet used.
         string memory childRpcUrl = vm.envString("CHILD_RPC_URL");
 
         vm.createSelectFork(childRpcUrl);

script/InitializeChildContracts.s.sol

@@ -20,6 +20,7 @@ contract InitializeChildContracts is Script {
         string memory childRpcUrl = vm.envString("CHILD_RPC_URL");
         string memory rootChainName = vm.envString("ROOT_CHAIN_NAME");
         address rootIMXToken = vm.envAddress("ROOT_IMX_ADDRESS");
+        address childGasService = vm.envAddress("CHILD_GAS_SERVICE_ADDRESS"); // Not yet used.
 
         /**
          * INITIALIZE CHILD CONTRACTS
@@ -35,7 +36,7 @@ contract InitializeChildContracts is Script {
             address(childAxelarBridgeAdaptor), rootBridgeAdaptorString, childTokenTemplate, rootChainName, rootIMXToken
         );
 
-        childAxelarBridgeAdaptor.initialize(address(childERC20Bridge));
+        childAxelarBridgeAdaptor.initialize(rootChainName, address(childERC20Bridge), childGasService);
 
         vm.stopBroadcast();
     }

src/child/ChildAxelarBridgeAdaptor.sol

@@ -2,14 +2,20 @@
 pragma solidity ^0.8.21;
 
 import {AxelarExecutable} from "@axelar-gmp-sdk-solidity/contracts/executable/AxelarExecutable.sol";
+import {IAxelarGasService} from "@axelar-cgp-solidity/contracts/interfaces/IAxelarGasService.sol";
+import {IAxelarGateway} from "@axelar-cgp-solidity/contracts/interfaces/IAxelarGateway.sol";
 import {Initializable} from "@openzeppelin/contracts/proxy/utils/Initializable.sol";
 import {IChildERC20Bridge} from "../interfaces/child/IChildERC20Bridge.sol";
-import {IChildAxelarBridgeAdaptorErrors} from "../interfaces/child/IChildAxelarBridgeAdaptor.sol";
+import {IChildAxelarBridgeAdaptorErrors, IChildAxelarBridgeAdaptorEvents} from "../interfaces/child/IChildAxelarBridgeAdaptor.sol";
+import {IChildERC20BridgeAdaptor} from "../interfaces/child/IChildERC20BridgeAdaptor.sol";
 
-contract ChildAxelarBridgeAdaptor is AxelarExecutable, Initializable, IChildAxelarBridgeAdaptorErrors {
+contract ChildAxelarBridgeAdaptor is AxelarExecutable, IChildERC20BridgeAdaptor, Initializable, IChildAxelarBridgeAdaptorErrors, 
+ IChildAxelarBridgeAdaptorEvents {
     /// @notice Address of bridge to relay messages to.
     IChildERC20Bridge public childBridge;
+    IAxelarGasService public gasService;
     string public rootBridgeAdaptor;
+    string public rootChain;
 
     constructor(address _gateway) AxelarExecutable(_gateway) {}
 
@@ -18,12 +24,14 @@ contract ChildAxelarBridgeAdaptor is AxelarExecutable, Initializable, IChildAxel
      * @param _childBridge Address of the child bridge contract.
      * @dev Always sets the rootBridgeAdaptor to whatever the rootERC20BridgeAdaptor of the bridge contract is.
      */
-    function initialize(address _childBridge) external initializer {
+    function initialize(string memory _rootChain, address _childBridge, address _gasService) external initializer {
         if (_childBridge == address(0)) {
             revert ZeroAddress();
         }
 
         childBridge = IChildERC20Bridge(_childBridge);
+        rootChain = _rootChain;
+        gasService = IAxelarGasService(_gasService);
         rootBridgeAdaptor = childBridge.rootERC20BridgeAdaptor();
     }
 
@@ -37,6 +45,30 @@ contract ChildAxelarBridgeAdaptor is AxelarExecutable, Initializable, IChildAxel
         rootBridgeAdaptor = childBridge.rootERC20BridgeAdaptor();
     }
 
+    /**
+     * TODO
+     */
+    function sendMessage(bytes calldata payload, address refundRecipient) external payable override {
+        if (msg.value == 0) {
+            revert NoGas();
+        }
+        if (msg.sender != address(childBridge)) {
+            revert CallerNotBridge();
+        }
+
+        // Load from storage.
+        string memory _rootBridgeAdaptor = rootBridgeAdaptor;
+        string memory _rootChain = rootChain;
+
+        // TODO For `sender` (first param), should likely be refundRecipient (and in which case refundRecipient should be renamed to sender and used as refund recipient)
+        gasService.payNativeGasForContractCall{value: msg.value}(
+            address(this), _rootChain, _rootBridgeAdaptor, payload, refundRecipient
+        );
+
+        gateway.callContract(_rootChain, _rootBridgeAdaptor, payload);
+        emit MapTokenAxelarMessage(_rootChain, _rootBridgeAdaptor, payload);
+    }
+
     /**
      * @dev This function is called by the parent `AxelarExecutable` contract to execute the payload.
      * @custom:assumes `sourceAddress_` is a 20 byte address.

src/child/ChildERC20Bridge.sol

@@ -132,9 +132,7 @@ contract ChildERC20Bridge is
     }
 
     function withdrawTo(IChildERC20 childToken, address receiver, uint256 amount) external {
-        _beforeTokenWithdraw();
         _withdraw(childToken, receiver, amount);
-        _afterTokenWithdraw();
     }
 
     function _withdraw(IChildERC20 childToken, address receiver, uint256 amount) private {
@@ -166,16 +164,9 @@ contract ChildERC20Bridge is
         bytes memory payload = abi.encode(WITHDRAW_SIG, rootToken, msg.sender, receiver, amount);
 
         // Send the message to the bridge adaptor and up to root chain
-        bridgeAdaptor.sendMessage(rootChain, rootERC20BridgeAdaptor, payload);
-
-        if (address(childToken) == childETHToken) {
-            childToken.burn(msg.sender, amount);
-            Address.sendValue(payable(receiver), amount);
-        } else {
-            childToken.burn(msg.sender, amount);
-            IERC20Metadata rootToken = IERC20Metadata(childToken.rootToken());
-            rootToken.safeTransfer(receiver, amount);
-        }
+        bridgeAdaptor.sendMessage{value: msg.value}(payload, msg.sender);
+
+        // TODO emit event
     }
 
     function _mapToken(bytes calldata data) private {

src/interfaces/child/IChildAxelarBridgeAdaptor.sol

@@ -4,4 +4,13 @@ pragma solidity ^0.8.21;
 interface IChildAxelarBridgeAdaptorErrors {
     /// @notice Error when a zero address is given when not valid.
     error ZeroAddress();
+    /// @notice Error when a message is sent with no gas payment.
+    error NoGas();
+    /// @notice Error when the caller is not the bridge.
+    error CallerNotBridge();
 }
+
+interface IChildAxelarBridgeAdaptorEvents {
+    /// @notice Emitted when an Axelar message is sent to the root chain.
+    event MapTokenAxelarMessage(string indexed rootChain, string indexed rootBridgeAdaptor, bytes indexed payload);
+}

src/interfaces/child/IChildERC20BridgeAdaptor.sol

@@ -1,5 +1,12 @@
 // SPDX-License-Identifier: Apache 2.0
 pragma solidity ^0.8.21;
 
-// TODO to be used when sending messages L2 -> L1
-interface IChildERC20BridgeAdaptor {}
+interface IChildERC20BridgeAdaptor {
+    /**
+     * @notice Send an arbitrary message to the root chain via the message passing protocol.
+     * @param payload The message to send, encoded in a `bytes` array.
+     * @param refundRecipient Used if the message passing protocol requires fees & pays back excess to a refund recipient.
+     * @dev `payable` because the message passing protocol may require a fee to be paid.
+     */
+    function sendMessage(bytes calldata payload, address refundRecipient) external payable;
+}

src/root/RootAxelarBridgeAdaptor.sol

@@ -30,8 +30,6 @@ contract RootAxelarBridgeAdaptor is
 
     address public rootBridge;
     string public childBridgeAdaptor;
-    /// @dev childChain could be immutable, but as of writing this Solidity does not support immutable strings.
-    ///      see: https://ethereum.stackexchange.com/questions/127622/typeerror-immutable-variables-cannot-have-a-non-value-type
     string public childChain;
     IAxelarGateway public axelarGateway;
     IAxelarGasService public gasService;

test/integration/child/ChildAxelarBridge.t.sol

@@ -13,6 +13,7 @@ import {
 } from "../../../src/child/ChildERC20Bridge.sol";
 import {IChildERC20, ChildERC20} from "../../../src/child/ChildERC20.sol";
 import {MockChildAxelarGateway} from "../../../src/test/child/MockChildAxelarGateway.sol";
+import {MockChildAxelarGasService} from "../../../src/test/child/MockChildAxelarGasService.sol";
 import {Utils} from "../../utils.t.sol";
 
 contract ChildERC20BridgeIntegrationTest is Test, IChildERC20BridgeEvents, IChildERC20BridgeErrors, Utils {
@@ -25,13 +26,15 @@ contract ChildERC20BridgeIntegrationTest is Test, IChildERC20BridgeEvents, IChil
     ChildERC20 public childERC20;
     ChildAxelarBridgeAdaptor public childAxelarBridgeAdaptor;
     MockChildAxelarGateway public mockChildAxelarGateway;
+    MockChildAxelarGasService public mockChildAxelarGasService;
 
     function setUp() public {
         childERC20 = new ChildERC20();
         childERC20.initialize(address(123), "Test", "TST", 18);
 
         childERC20Bridge = new ChildERC20Bridge();
         mockChildAxelarGateway = new MockChildAxelarGateway();
+        mockChildAxelarGasService = new MockChildAxelarGasService();
         childAxelarBridgeAdaptor = new ChildAxelarBridgeAdaptor(address(mockChildAxelarGateway));
 
         childERC20Bridge.initialize(
@@ -42,7 +45,7 @@ contract ChildERC20BridgeIntegrationTest is Test, IChildERC20BridgeEvents, IChil
             IMX_TOKEN_ADDRESS
         );
 
-        childAxelarBridgeAdaptor.initialize(address(childERC20Bridge));
+        childAxelarBridgeAdaptor.initialize(ROOT_CHAIN_NAME, address(childERC20Bridge), address(mockChildAxelarGasService));
     }
 
     function test_ChildTokenMap() public {

test/unit/child/ChildAxelarBridgeAdaptor.t.sol

@@ -7,6 +7,7 @@ import {Strings} from "@openzeppelin/contracts/utils/Strings.sol";
 import {ChildAxelarBridgeAdaptor} from "../../../src/child/ChildAxelarBridgeAdaptor.sol";
 import {MockChildERC20Bridge} from "../../../src/test/child/MockChildERC20Bridge.sol";
 import {MockChildAxelarGateway} from "../../../src/test/child/MockChildAxelarGateway.sol";
+import {MockChildAxelarGasService} from "../../../src/test/child/MockChildAxelarGasService.sol";
 import {IChildAxelarBridgeAdaptorErrors} from "../../../src/interfaces/child/IChildAxelarBridgeAdaptor.sol";
 
 contract ChildAxelarBridgeAdaptorUnitTest is Test, IChildAxelarBridgeAdaptorErrors {
@@ -15,23 +16,26 @@ contract ChildAxelarBridgeAdaptorUnitTest is Test, IChildAxelarBridgeAdaptorErro
     ChildAxelarBridgeAdaptor public childAxelarBridgeAdaptor;
     MockChildERC20Bridge public mockChildERC20Bridge;
     MockChildAxelarGateway public mockChildAxelarGateway;
+    MockChildAxelarGasService public mockChildAxelarGasService;
 
     function setUp() public {
         mockChildERC20Bridge = new MockChildERC20Bridge();
         mockChildAxelarGateway = new MockChildAxelarGateway();
+        mockChildAxelarGasService = new MockChildAxelarGasService();
         childAxelarBridgeAdaptor = new ChildAxelarBridgeAdaptor(address(mockChildAxelarGateway));
-        childAxelarBridgeAdaptor.initialize(address(mockChildERC20Bridge));
+        childAxelarBridgeAdaptor.initialize("root", address(mockChildERC20Bridge), address(mockChildAxelarGasService));
     }
 
     function test_Constructor_SetsValues() public {
         assertEq(address(childAxelarBridgeAdaptor.childBridge()), address(mockChildERC20Bridge), "childBridge not set");
         assertEq(address(childAxelarBridgeAdaptor.gateway()), address(mockChildAxelarGateway), "gateway not set");
     }
 
-    function test_RevertIf_ConstructorGivenZeroAddress() public {
+    // TODO add more initialize tests
+    function test_RevertIf_InitializeGivenZeroAddress() public {
         ChildAxelarBridgeAdaptor newAdaptor = new ChildAxelarBridgeAdaptor(GATEWAY_ADDRESS);
         vm.expectRevert(ZeroAddress.selector);
-        newAdaptor.initialize(address(0));
+        newAdaptor.initialize("root", address(0), address(mockChildAxelarGasService));
     }
 
     function test_Execute() public {