feat(ics26): implemented AckPacket

src/ICS26Router.sol

@@ -129,8 +129,42 @@ contract ICS26Router is IICS26Router, IBCStore, Ownable, IICS26RouterErrors, Ree
     /// @notice Acknowledges a packet
     /// @param msg_ The message for acknowledging packets
     function ackPacket(MsgAckPacket calldata msg_) external nonReentrant {
-        // TODO: implement
-        // IIBCApp app = IIBCApp(apps[msg.packet.sourcePort]);
+        IIBCApp app = IIBCApp(apps[msg_.packet.sourcePort]);
+
+        string memory counterpartyId = ics02Client.getCounterparty(msg_.packet.sourceChannel).clientId;
+        if (keccak256(bytes(counterpartyId)) != keccak256(bytes(msg_.packet.destChannel))) {
+            revert IBCInvalidCounterparty(counterpartyId, msg_.packet.destChannel);
+        }
+
+        // this will revert if the packet commitment does not exist
+        bytes32 storedCommitment = IBCStore.deletePacketCommitment(msg_.packet);
+        if (storedCommitment != ICS24Host.packetCommitmentBytes32(msg_.packet)) {
+            revert IBCPacketCommitmentMismatch(storedCommitment, ICS24Host.packetCommitmentBytes32(msg_.packet));
+        }
+
+        bytes memory commitmentPath = ICS24Host.packetAcknowledgementCommitmentPathCalldata(
+            msg_.packet.sourcePort, msg_.packet.sourceChannel, msg_.packet.sequence
+        );
+        bytes32 commitmentBz = ICS24Host.packetAcknowledgementCommitmentBytes32(msg_.acknowledgement);
+
+        // verify the packet acknowledgement
+        ILightClientMsgs.MsgMembership memory membershipMsg = ILightClientMsgs.MsgMembership({
+            proof: msg_.proofAcked,
+            proofHeight: msg_.proofHeight,
+            kvPair: ILightClientMsgs.KVPair({ path: commitmentPath, value: abi.encodePacked(commitmentBz) })
+        });
+
+        ics02Client.getClient(msg_.packet.sourceChannel).verifyMembership(membershipMsg);
+
+        app.onAcknowledgementPacket(
+            IIBCAppCallbacks.OnAcknowledgementPacketCallback({
+                packet: msg_.packet,
+                acknowledgement: msg_.acknowledgement,
+                relayer: msg.sender
+            })
+        );
+
+        emit AckPacket(msg_.packet, msg_.acknowledgement);
     }
 
     /// @notice Timeouts a packet

src/errors/IICS26RouterErrors.sol

@@ -16,4 +16,6 @@ interface IICS26RouterErrors {
     error IBCInvalidCounterparty(string expected, string actual);
 
     error IBCAsyncAcknowledgementNotSupported();
+
+    error IBCPacketCommitmentMismatch(bytes32 expected, bytes32 actual);
 }

src/interfaces/IICS26Router.sol

@@ -42,8 +42,10 @@ interface IICS26Router is IICS26RouterMsgs {
     event SendPacket(Packet packet);
     /// @notice Emitted when a packet is received
     event RecvPacket(Packet packet);
-    /// @notice Emitted when a packet is acknowledged
+    /// @notice Emitted when a packet acknowledgement is written
     event WriteAcknowledgement(Packet packet, bytes acknowledgement);
     /// @notice Emitted when a packet is timed out
     event TimeoutPacket(Packet packet);
+    /// @notice Emitted when a packet is acknowledged
+    event AckPacket(Packet packet, bytes acknowledgement);
 }

src/utils/IBCIdentifiers.sol

@@ -1,9 +1,6 @@
 // SPDX-License-Identifier: UNLICENSED
 pragma solidity >=0.8.25;
 
-import { Strings } from "@openzeppelin/contracts/utils/Strings.sol";
-import { IICS26RouterMsgs } from "../msgs/IICS26RouterMsgs.sol";
-
 /// @title IBC Identifiers
 /// @notice Utilities for validating IBC identifiers
 library IBCIdentifiers {

src/utils/IBCStore.sol

@@ -49,17 +49,19 @@ abstract contract IBCStore is IIBCStore, IICS24HostErrors {
         commitments[path] = commitment;
     }
 
-    /// @notice Deletes a packet commitment
+    /// @notice Deletes a packet commitment and reverts if it does not exist
     /// @param packet The packet whose commitment to delete
-    function deletePacketCommitment(IICS26RouterMsgs.Packet memory packet) internal {
+    function deletePacketCommitment(IICS26RouterMsgs.Packet memory packet) internal returns (bytes32) {
         bytes32 path = ICS24Host.packetCommitmentKeyCalldata(packet.sourcePort, packet.sourceChannel, packet.sequence);
-        if (commitments[path] == 0) {
+        bytes32 commitment = commitments[path];
+        if (commitment == 0) {
             revert IBCPacketCommitmentNotFound(
                 ICS24Host.packetCommitmentPathCalldata(packet.sourcePort, packet.sourceChannel, packet.sequence)
             );
         }
 
         delete commitments[path];
+        return commitment;
     }
 
     /// @notice Sets a packet receipt

test/IbcIdentifiers.t.sol

@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: UNLICENSED
 pragma solidity >=0.8.25 <0.9.0;
 
+// solhint-disable custom-errors,max-line-length
+
 import { Test } from "forge-std/src/Test.sol";
 import { IBCIdentifiers } from "../src/utils/IBCIdentifiers.sol";