feat: permit method

src/facets/NaymsTokenFacet.sol

@@ -88,4 +88,61 @@ contract NaymsTokenFacet is Modifiers {
         AppStorage storage s = LibAppStorage.diamondStorage();
         return s.minter;
     }
+
+    /// @dev The EIP-712 typehash for the permit struct used by the contract
+    bytes32 public constant PERMIT_TYPEHASH =
+        keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
+
+    /**
+     * @dev See {IERC20Permit-permit}.
+     */
+    function permit(
+        address _owner,
+        address _spender,
+        uint256 _value,
+        uint256 _deadline,
+        uint8 _v,
+        bytes32 _r,
+        bytes32 _s
+    )
+        external
+    {
+        AppStorage storage s = LibAppStorage.diamondStorage();
+
+        if (block.timestamp > _deadline) {
+            revert("ERC20Permit: expired deadline");
+        }
+
+        bytes32 structHash =
+            keccak256(abi.encode(PERMIT_TYPEHASH, _owner, _spender, _value, s.nonces[_owner]++, _deadline));
+
+        bytes32 hash = keccak256(abi.encodePacked("\x19\x01", s.DOMAIN_SEPARATOR, structHash));
+
+        address signer = ecrecover(hash, _v, _r, _s);
+        if (signer == address(0) || signer != _owner) {
+            revert("ERC20Permit: invalid signature");
+        }
+
+        LibERC20Token._approve(_owner, _spender, _value, true);
+    }
+
+    /**
+     * @dev Returns the current nonce for `owner`. This value must be included whenever a signature is generated for
+     * {permit}.
+     *
+     * Every successful call to {permit} increases ``owner``'s nonce by one. This
+     * prevents a signature from being used multiple times.
+     */
+    function nonces(address owner) external view returns (uint256) {
+        AppStorage storage s = LibAppStorage.diamondStorage();
+        return s.nonces[owner];
+    }
+
+    /**
+     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
+     */
+    function DOMAIN_SEPARATOR() external view returns (bytes32) {
+        AppStorage storage s = LibAppStorage.diamondStorage();
+        return s.DOMAIN_SEPARATOR;
+    }
 }

src/init/InitPermit.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.24;
+
+import { AppStorage, LibAppStorage } from "../shared/AppStorage.sol";
+
+contract InitPermit {
+    function init() external {
+        uint256 initId = 2; // Using ID 2 since InitializationTest1 used ID 1
+
+        AppStorage storage s = LibAppStorage.diamondStorage();
+        require(!s.initComplete[initId], "Initialization already complete");
+
+        // Initialize the domain separator and chain id
+        s.initialChainId = block.chainid;
+        s.initialDomainSeparator = _computeDomainSeparator();
+
+        s.initComplete[initId] = true;
+    }
+
+    function _computeDomainSeparator() internal view returns (bytes32) {
+        return keccak256(
+            abi.encode(
+                keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),
+                keccak256(bytes("Naym")), // name
+                keccak256(bytes("1")), // version
+                block.chainid,
+                address(this)
+            )
+        );
+    }
+}

src/shared/AppStorage.sol

@@ -30,6 +30,8 @@ struct AppStorage {
     address minter;
     // upgrade initializations
     mapping(uint256 => bool) initComplete;
+    bytes32 DOMAIN_SEPARATOR;
+    mapping(address permitCaller => uint256 nonce) nonces;
 }
 
 library LibAppStorage {