feat:EIP712 module

src/libraries/EIP712Mod.sol

@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: MIT
+pragma solidity >=0.8.30;
+
+bytes32 constant STORAGE_POSITION = keccak256("eip712.typed.structured.data.hashing.and.signing");
+
+/**
+ * @custom:storage-location erc8042:eip712.typed.structured.data.hashing.and.signing
+ */
+struct EIP712Storage {
+    bytes32 domainSeparator;
+    string name;
+    string version;
+    bytes32 TYPE_HASH;
+    bytes32 NAME_HASH;
+    bytes32 VERSION_HASH;
+    uint256 chainId;
+    address verifyingContract;
+}
+
+/**
+ * @notice Returns a pointer to the ERC-712 storage struct.
+ * @dev Uses inline assembly to access the storage slot defined by STORAGE_POSITION.
+ * @return s The EIP712Storage struct in storage.
+ */
+function getStorage() pure returns (EIP712Storage storage s) {
+    bytes32 position = STORAGE_POSITION;
+    assembly {
+        s.slot := position
+    }
+}
+
+/**
+ * @notice Retures a domain separator from storage if calling contract and chain id is same as verifyingContract and chainId stored in storage.
+ * @notice otherwise it builds the deomain separator
+ * @return the domain separator
+ */
+function domainSeparator() view returns (bytes32) {
+    EIP712Storage memory s = getStorage();
+
+    address thisAddress;
+    uint256 chain;
+    assembly {
+        thisAddress := address()
+        chain := chainid()
+    }
+
+    if (thisAddress == s.verifyingContract && chain == s.chainId) {
+        return s.domainSeparator;
+    } else {
+        return buildDomainSeparator(s, thisAddress, chain);
+    }
+}
+
+/**
+ * @param s EIP712 storage in smart contract
+ * @param verifyingContract  verifying smart contract address from storage or current calling contract
+ * @param chainid chainid of current using chain
+ * @return returns the domain separator
+ */
+function buildDomainSeparator(EIP712Storage memory s, address verifyingContract, uint256 chainid)
+    pure
+    returns (bytes32)
+{
+    return keccak256(abi.encode(s.TYPE_HASH, s.NAME_HASH, s.VERSION_HASH, chainid, verifyingContract));
+}
+
+function hashTypedData(bytes32 structHash) view returns (bytes32) {
+    return typedDataHash(domainSeparator(), structHash);
+}
+
+function typedDataHash(bytes32 domainSeparator, bytes32 structHash) pure returns (bytes32) {
+    return keccak256(abi.encode("\x19\x01", domainSeparator, structHash));
+}
+
+/**
+ * @return name of the EIP712 contract
+ */
+function EIP712Name() view returns (string memory) {
+    return getStorage().name;
+}
+
+/**
+ * @return version of the EIP712 contract
+ */
+function EIP712Version() view returns (string memory) {
+    return getStorage().version;
+}