refactor(gateway): add {Home,Foreign}Gateway interfaces

Author: shalzz

contracts/src/gateway/IForeignGateway.sol

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../arbitration/IArbitrator.sol";
+
+interface IForeignGateway is IArbitrator {
+    /**
+     * Relay the rule call from the home gateway to the arbitrable.
+     *
+     * @param _data The calldata to relay
+     */
+    function relayRule(bytes memory _data) external;
+}

contracts/src/gateway/IHomeGateway.sol

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../arbitration/IArbitrable.sol";
+
+interface IHomeGateway is IArbitrable {
+    /**
+     * Relay the createDispute call from the foreign gateway to the arbitrator.
+     *
+     * @param _data The calldata to relay
+     */
+    function relayCreateDispute(bytes memory _data) external;
+}

contracts/src/gateway/arbitrum/HomeGateway.sol renamed to contracts/src/gateway/arbitrum/ArbitrumGateway.sol

@@ -2,13 +2,13 @@
 
 pragma solidity ^0.8.0;
 
-import "../../arbitration/IArbitrable.sol";
 import "../../arbitration/IArbitrator.sol";
 import "../../bridge/arbitrum/L2Bridge.sol";
 
-import "./ForeignGateway.sol";
+import "../IHomeGateway.sol";
+import "../IForeignGateway.sol";
 
-contract HomeGateway is IArbitrable {
+contract ArbitrumGateway is IHomeGateway {
     // L2 bridge with the ForeignGateway as the l1target
     L2Bridge internal l2bridge;
     address public arbitrator;
@@ -21,7 +21,7 @@ contract HomeGateway is IArbitrable {
     function rule(uint256, uint256) external {
         require(msg.sender == arbitrator, "Only Arbitrator");
 
-        bytes4 methodSelector = ForeignGateway.relayRule.selector;
+        bytes4 methodSelector = IForeignGateway.relayRule.selector;
         bytes memory data = abi.encodeWithSelector(methodSelector, msg.data);
 
         l2bridge.sendCrossDomainMessage(data);

contracts/src/gateway/arbitrum/ForeignGateway.sol renamed to contracts/src/gateway/arbitrum/EthereumGateway.sol

@@ -3,12 +3,12 @@
 pragma solidity ^0.8.0;
 
 import "../../arbitration/IArbitrable.sol";
-import "../../arbitration/IArbitrator.sol";
 import "../../bridge/arbitrum/L1Bridge.sol";
 
-import "./HomeGateway.sol";
+import "../IHomeGateway.sol";
+import "../IForeignGateway.sol";
 
-contract ForeignGateway is IArbitrator {
+contract EthereumGateway is IForeignGateway {
     // L1 bridge with the HomeGateway as the l2target
     L1Bridge internal l1bridge;
 
@@ -25,7 +25,7 @@ contract ForeignGateway is IArbitrator {
     function createDispute(uint256 _choices, bytes calldata _extraData) external payable returns (uint256 disputeID) {
         require(msg.value >= arbitrationCost(_extraData), "Not paid enough for arbitration");
 
-        bytes4 methodSelector = HomeGateway.relayCreateDispute.selector;
+        bytes4 methodSelector = IHomeGateway.relayCreateDispute.selector;
         bytes memory data = abi.encodeWithSelector(methodSelector, msg.data);
 
         uint256 bridgeCost = l1bridge.getSubmissionPrice(data.length);
@@ -43,9 +43,9 @@ contract ForeignGateway is IArbitrator {
         // only the calldata.
         l1bridge.sendCrossDomainMessage{value: bridgeCost}(data, 0, 0);
 
-        disputeId = 0; // TODO: map to the actual disputeID we get from the V2 court
-        emit DisputeCreation(disputeId, IArbitrable(msg.sender));
-        return disputeId;
+        disputeID = 0; // TODO: map to the actual disputeID we get from the V2 court
+        emit DisputeCreation(disputeID, IArbitrable(msg.sender));
+        return disputeID;
     }
 
     function arbitrationCost(bytes calldata _extraData) public view returns (uint256 cost) {