Make capability storage type address instead of address[]

.gas-snapshot

@@ -1,21 +1,21 @@
 IBCTest:testBenchmarkCreateMockClient() (gas: 211733)
-IBCTest:testBenchmarkRecvPacket() (gas: 139993)
-IBCTest:testBenchmarkSendPacket() (gas: 86019)
+IBCTest:testBenchmarkRecvPacket() (gas: 137422)
+IBCTest:testBenchmarkSendPacket() (gas: 85195)
 IBCTest:testBenchmarkUpdateMockClient() (gas: 126635)
 IBCTest:testToUint128((uint64,uint64)) (runs: 256, μ: 917, ~: 917)
-TestICS02:testCreateClient() (gas: 23295732)
-TestICS02:testInvalidCreateClient() (gas: 23143327)
-TestICS02:testInvalidUpdateClient() (gas: 23147156)
-TestICS02:testRegisterClient() (gas: 22767378)
-TestICS02:testRegisterClientDuplicatedClientType() (gas: 22749428)
-TestICS02:testRegisterClientInvalidClientType() (gas: 22734298)
-TestICS02:testUpdateClient() (gas: 23290442)
-TestICS03Handshake:testConnOpenAck() (gas: 1589222)
-TestICS03Handshake:testConnOpenConfirm() (gas: 1722517)
-TestICS03Handshake:testConnOpenInit() (gas: 1285075)
+TestICS02:testCreateClient() (gas: 23194177)
+TestICS02:testInvalidCreateClient() (gas: 23041922)
+TestICS02:testInvalidUpdateClient() (gas: 23045689)
+TestICS02:testRegisterClient() (gas: 22665889)
+TestICS02:testRegisterClientDuplicatedClientType() (gas: 22647939)
+TestICS02:testRegisterClientInvalidClientType() (gas: 22632765)
+TestICS02:testUpdateClient() (gas: 23188909)
+TestICS03Handshake:testConnOpenAck() (gas: 1589200)
+TestICS03Handshake:testConnOpenConfirm() (gas: 1722518)
+TestICS03Handshake:testConnOpenInit() (gas: 1285031)
 TestICS03Handshake:testConnOpenTry() (gas: 2082502)
-TestICS03Handshake:testInvalidConnOpenAck() (gas: 1945699)
-TestICS03Handshake:testInvalidConnOpenConfirm() (gas: 1965710)
+TestICS03Handshake:testInvalidConnOpenAck() (gas: 1945633)
+TestICS03Handshake:testInvalidConnOpenConfirm() (gas: 1965802)
 TestICS03Handshake:testInvalidConnOpenInit() (gas: 671931)
 TestICS03Handshake:testInvalidConnOpenTry() (gas: 2087487)
 TestICS03Version:testCopyVersions() (gas: 558658)
@@ -24,16 +24,17 @@ TestICS03Version:testIsSupportedVersion() (gas: 7864)
 TestICS03Version:testPickVersion() (gas: 25399)
 TestICS03Version:testVerifyProposedVersion() (gas: 11777)
 TestICS03Version:testVerifySupportedFeature() (gas: 4153)
-TestICS04Handshake:testChanOpenAck() (gas: 2985837)
-TestICS04Handshake:testChanOpenConfirm() (gas: 3168093)
-TestICS04Handshake:testChanOpenInit() (gas: 2274367)
-TestICS04Handshake:testChanOpenTry() (gas: 2757417)
-TestICS04Handshake:testInvalidChanOpenAck() (gas: 2115048)
-TestICS04Handshake:testInvalidChanOpenConfirm() (gas: 2174082)
-TestICS04Handshake:testInvalidChanOpenInit() (gas: 1279457)
-TestICS04Handshake:testInvalidChanOpenTry() (gas: 1353660)
-TestICS04Packet:testInvalidSendPacket() (gas: 2315761)
-TestICS04Packet:testSendPacket() (gas: 2373812)
+TestICS04Handshake:testBindPort() (gas: 40421)
+TestICS04Handshake:testChanOpenAck() (gas: 2887537)
+TestICS04Handshake:testChanOpenConfirm() (gas: 3067861)
+TestICS04Handshake:testChanOpenInit() (gas: 2203120)
+TestICS04Handshake:testChanOpenTry() (gas: 2661049)
+TestICS04Handshake:testInvalidChanOpenAck() (gas: 2064863)
+TestICS04Handshake:testInvalidChanOpenConfirm() (gas: 2122953)
+TestICS04Handshake:testInvalidChanOpenInit() (gas: 1279180)
+TestICS04Handshake:testInvalidChanOpenTry() (gas: 1353271)
+TestICS04Packet:testInvalidSendPacket() (gas: 2210343)
+TestICS04Packet:testSendPacket() (gas: 2269694)
 TestICS20:testAddressToHex(address) (runs: 256, μ: 22675, ~: 22824)
 TestICS20:testHexToAddress(string) (runs: 256, μ: 4776, ~: 4734)
 TestICS20:testIsEscapedString() (gas: 48979)

contracts/core/24-host/IBCStore.sol

@@ -18,7 +18,7 @@ abstract contract IBCStore {
     mapping(string => mapping(string => uint64)) internal nextSequenceSends;
     mapping(string => mapping(string => uint64)) internal nextSequenceRecvs;
     mapping(string => mapping(string => uint64)) internal nextSequenceAcks;
-    mapping(bytes => address[]) internal capabilities;
+    mapping(string => address) internal capabilities;
 
     // Host parameters
     uint64 internal expectedTimePerBlock;

contracts/core/26-router/IBCModuleManager.sol

@@ -13,9 +13,9 @@ contract IBCModuleManager is IBCHost, Context {
      * @dev lookupModuleByPort will return the IBCModule along with the capability associated with a given portID
      */
     function lookupModuleByPort(string memory portId) internal view virtual returns (IIBCModule) {
-        (address[] storage modules, bool found) = lookupModules(portCapabilityPath(portId));
-        require(found);
-        return IIBCModule(modules[0]);
+        address module = lookupModule(portCapabilityPath(portId));
+        require(module != address(0), "module not found");
+        return IIBCModule(module);
     }
 
     /**
@@ -27,47 +27,39 @@ contract IBCModuleManager is IBCHost, Context {
         virtual
         returns (IIBCModule)
     {
-        (address[] storage modules, bool found) = lookupModules(channelCapabilityPath(portId, channelId));
-        require(found);
-        return IIBCModule(modules[0]);
+        address module = lookupModule(channelCapabilityPath(portId, channelId));
+        require(module != address(0), "module not found");
+        return IIBCModule(module);
     }
 
     /**
      * @dev claimCapability allows the IBC app module to claim a capability that core IBC passes to it
      */
-    function claimCapability(bytes memory name, address addr) internal {
-        for (uint32 i = 0; i < capabilities[name].length; i++) {
-            require(capabilities[name][i] != addr);
-        }
-        capabilities[name].push(addr);
+    function claimCapability(string memory name, address addr) internal {
+        require(capabilities[name] == address(0), "capability already claimed");
+        capabilities[name] = addr;
     }
 
     /**
      * @dev authenticateCapability attempts to authenticate a given name from a caller.
      * It allows for a caller to check that a capability does in fact correspond to a particular name.
      */
-    function authenticateCapability(bytes memory name) internal view returns (bool) {
-        address caller = _msgSender();
-        for (uint32 i = 0; i < capabilities[name].length; i++) {
-            if (capabilities[name][i] == caller) {
-                return true;
-            }
-        }
-        return false;
+    function authenticateCapability(string memory name) internal view returns (bool) {
+        return _msgSender() == capabilities[name];
     }
 
     /**
-     * @dev lookupModules will return the IBCModule addresses bound to a given name.
+     * @dev lookupModule will return the IBCModule addresses bound to a given name.
      */
-    function lookupModules(bytes memory name) internal view returns (address[] storage, bool) {
-        return (capabilities[name], capabilities[name].length > 0);
+    function lookupModule(string memory name) internal view returns (address) {
+        return capabilities[name];
     }
 
     /**
      * @dev portCapabilityPath returns the path under which owner module address associated with a port should be stored.
      */
-    function portCapabilityPath(string memory portId) internal pure returns (bytes memory) {
-        return abi.encodePacked(portId);
+    function portCapabilityPath(string memory portId) internal pure returns (string memory) {
+        return portId;
     }
 
     /**
@@ -76,9 +68,9 @@ contract IBCModuleManager is IBCHost, Context {
     function channelCapabilityPath(string memory portId, string memory channelId)
         internal
         pure
-        returns (bytes memory)
+        returns (string memory)
     {
-        return abi.encodePacked(portId, "/", channelId);
+        return string.concat(portId, "/", channelId);
     }
 
     /**