Introduce Mock app and fix commitment of nextSequenceRecv

contracts/apps/mock/IBCMockApp.sol

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.9;
+
+import "../commons/IBCAppBase.sol";
+import "../../core/05-port/IIBCModule.sol";
+import "../../core/25-handler/IBCHandler.sol";
+import "./IBCMockLib.sol";
+
+contract IBCMockApp is IBCAppBase {
+    IBCHandler ibcHandler;
+
+    constructor(IBCHandler ibcHandler_) {
+        ibcHandler = ibcHandler_;
+    }
+
+    function ibcAddress() public view virtual override returns (address) {
+        return address(ibcHandler);
+    }
+
+    function sendPacket(
+        string calldata message,
+        string calldata sourcePort,
+        string calldata sourceChannel,
+        Height.Data calldata timeoutHeight,
+        uint64 timeoutTimestamp
+    ) external {
+        ibcHandler.sendPacket(sourcePort, sourceChannel, timeoutHeight, timeoutTimestamp, bytes(message));
+    }
+
+    function onRecvPacket(Packet.Data calldata packet, address)
+        external
+        override
+        onlyIBC
+        returns (bytes memory acknowledgement)
+    {
+        if (keccak256(packet.data) == keccak256(IBCMockLib.MOCK_PACKET_DATA)) {
+            return IBCMockLib.SUCCESSFUL_ACKNOWLEDGEMENT_JSON;
+        } else if (keccak256(packet.data) == keccak256(IBCMockLib.MOCK_ASYNC_PACKET_DATA)) {
+            return bytes("");
+        } else {
+            return IBCMockLib.FAILED_ACKNOWLEDGEMENT_JSON;
+        }
+    }
+
+    function onAcknowledgementPacket(Packet.Data calldata packet, bytes calldata acknowledgement, address)
+        external
+        virtual
+        override
+        onlyIBC
+    {
+        if (keccak256(packet.data) == keccak256(IBCMockLib.MOCK_PACKET_DATA)) {
+            require(keccak256(acknowledgement) == keccak256(IBCMockLib.SUCCESSFUL_ACKNOWLEDGEMENT_JSON));
+        } else if (keccak256(packet.data) == keccak256(IBCMockLib.MOCK_ASYNC_PACKET_DATA)) {
+            require(acknowledgement.length == 0);
+        } else {
+            require(keccak256(acknowledgement) == keccak256(IBCMockLib.FAILED_ACKNOWLEDGEMENT_JSON));
+        }
+    }
+}

contracts/apps/mock/IBCMockLib.sol

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity ^0.8.9;
+
+library IBCMockLib {
+    bytes public constant MOCK_PACKET_DATA = bytes("mock packet data");
+    bytes public constant MOCK_FAIL_PACKET_DATA = bytes("mock failed packet data");
+    bytes public constant MOCK_ASYNC_PACKET_DATA = bytes("mock async packet data");
+
+    bytes public constant SUCCESSFUL_ACKNOWLEDGEMENT_JSON = bytes('{"result":"bW9jayBhY2tub3dsZWRnZW1lbnQ="}');
+    bytes public constant FAILED_ACKNOWLEDGEMENT_JSON = bytes('{"error":"mock failed acknowledgement"}');
+}

contracts/core/04-channel/IBCChannelHandshake.sol

@@ -36,6 +36,8 @@ contract IBCChannelHandshake is IBCStore, IIBCChannelHandshake {
         nextSequenceRecvs[msg_.portId][channelId] = 1;
         nextSequenceAcks[msg_.portId][channelId] = 1;
         updateChannelCommitment(msg_.portId, channelId);
+        commitments[IBCCommitment.nextSequenceRecvCommitmentKey(msg_.portId, channelId)] =
+            keccak256(abi.encodePacked((bytes8(uint64(1)))));
         return channelId;
     }
 
@@ -80,6 +82,8 @@ contract IBCChannelHandshake is IBCStore, IIBCChannelHandshake {
         nextSequenceRecvs[msg_.portId][channelId] = 1;
         nextSequenceAcks[msg_.portId][channelId] = 1;
         updateChannelCommitment(msg_.portId, channelId);
+        commitments[IBCCommitment.nextSequenceRecvCommitmentKey(msg_.portId, channelId)] =
+            keccak256(abi.encodePacked((bytes8(uint64(1)))));
         return channelId;
     }
 

contracts/core/25-handler/IBCQuerier.sol

@@ -67,6 +67,10 @@ abstract contract IBCQuerier is IBCStore {
         return nextSequenceSends[portId][channelId];
     }
 
+    function getNextSequenceRecv(string calldata portId, string calldata channelId) external view returns (uint64) {
+        return nextSequenceRecvs[portId][channelId];
+    }
+
     function getExpectedTimePerBlock() external view returns (uint64) {
         return expectedTimePerBlock;
     }

pkg/ibc/core/commitment/commitment.go

@@ -39,6 +39,10 @@ func PacketReceiptCommitmentSlot(portID, channelID string, sequence uint64) stri
 	return CalculateCommitmentSlot(host.PacketReceiptKey(portID, channelID, sequence))
 }
 
+func NextSequenceRecvCommitmentSlot(portID, channelID string) string {
+	return CalculateCommitmentSlot(host.NextSequenceRecvKey(portID, channelID))
+}
+
 func CalculateCommitmentSlot(path []byte) string {
 	return crypto.Keccak256Hash(crypto.Keccak256Hash(path).Bytes(), ibcHostCommitmentSlot[:]).Hex()
 }