[#47] Create FunctionHandlerManager.sol and inherit in SafeProtocolMa…

…nager

contracts/SafeProtocolManager.sol

@@ -8,14 +8,15 @@ import {SafeProtocolAction, SafeTransaction, SafeRootAccess} from "./DataTypes.s
 import {ISafeProtocolRegistry} from "./interfaces/Registry.sol";
 import {RegistryManager} from "./base/RegistryManager.sol";
 import {HooksManager} from "./base/HooksManager.sol";
+import {FunctionHandlerManager} from "./base/FunctionHandlerManager.sol";
 import {BaseGuard} from "@safe-global/safe-contracts/contracts/base/GuardManager.sol";
 import {Enum} from "@safe-global/safe-contracts/contracts/common/Enum.sol";
 
 /**
  * @title SafeProtocolManager contract allows Safe users to set plugin through a Manager rather than directly enabling a plugin on Safe.
  *        Users have to first enable SafeProtocolManager as a plugin on a Safe and then enable other plugins through the mediator.
  */
-contract SafeProtocolManager is ISafeProtocolManager, RegistryManager, HooksManager, BaseGuard {
+contract SafeProtocolManager is ISafeProtocolManager, RegistryManager, HooksManager, FunctionHandlerManager, BaseGuard {
     address internal constant SENTINEL_MODULES = address(0x1);
 
     /**

contracts/base/FunctionHandlerManager.sol

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: LGPL-3.0-only
+pragma solidity ^0.8.18;
+import {IERC165} from "@openzeppelin/contracts/utils/introspection/IERC165.sol";
+
+/**
+ * @title This contract manages the function handlers for the Safe Account. The contract stores the
+ *        information about Safe account, Function selectr and the function handler contract address.
+ */
+contract FunctionHandlerManager {
+    // Storage
+    /** @dev Mapping that stores information about Safe account, function selector, and address of the account.
+     */
+    mapping(address => mapping(bytes4 => address)) public functionHandlers;
+
+    // Events
+    event FunctionHandlerChanged(address indexed safe, bytes4 indexed selector, address indexed functionHandler);
+
+    // Errors
+    error AddressDoesNotImplementFunctionHandlerInterface(address functionHandler);
+
+    /**
+     * @notice Returns the function handler for a Safe account and function selector.
+     * @param safe Address of the Safe account
+     * @param selector bytes4 function selector
+     * @return functionHandler Address of the contract to be set as a function handler
+     */
+    function getFunctionHandler(address safe, bytes4 selector) external view returns (address functionHandler) {
+        functionHandler = functionHandlers[safe][selector];
+    }
+
+    /**
+     * @notice Sets the function handler for a Safe account and function selector. The msg.sender must be the account.
+     * @param selector bytes4 function selector
+     * @param functionHandler Address of the contract to be set as a function handler
+     */
+    function setFunctionHandler(bytes4 selector, address functionHandler) external {
+        if (functionHandler != address(0) && !IERC165(functionHandler).supportsInterface(0x00000000)) {
+            revert AddressDoesNotImplementFunctionHandlerInterface(functionHandler);
+        }
+
+        functionHandlers[msg.sender][selector] = functionHandler;
+        emit FunctionHandlerChanged(msg.sender, selector, functionHandler);
+    }
+}