// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (utils/cryptography/EIP712.sol)

pragma solidity ^0.8.20;

import {MessageHashUtils} from "@openzeppelin/contracts/utils/cryptography/MessageHashUtils.sol";
import {IERC5267} from "@openzeppelin/contracts/interfaces/IERC5267.sol";
import {Initializable} from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";

/**
 * @dev This is an extension of the OpenZeppelin EIP712Upgradeable implementation, adding two variables in storage:
 * _verifyingContractSource and _chainIDSource. This allows a contract on a target chain to verify EIP712 signatures
 * which were targeting another source verifyingContract potentially deployed on another source chain.
 *
 * @dev https://eips.ethereum.org/EIPS/eip-712[EIP-712] is a standard for hashing and signing of typed structured data.
 *
 * The encoding scheme specified in the EIP requires a domain separator and a hash of the typed structured data, whose
 * encoding is very generic and therefore its implementation in Solidity is not feasible, thus this contract
 * does not implement the encoding itself. Protocols need to implement the type-specific encoding they need in order to
 * produce the hash of their typed data using a combination of `abi.encode` and `keccak256`.
 *
 * This contract implements the EIP-712 domain separator ({_domainSeparatorV4}) that is used as part of the encoding
 * scheme, and the final step of the encoding to obtain the message digest that is then signed via ECDSA
 * ({_hashTypedDataV4}).
 *
 * The implementation of the domain separator was designed to be as efficient as possible while still properly updating
 * the chain id to protect against replay attacks on an eventual fork of the chain.
 *
 * NOTE: This contract implements the version of the encoding known as "v4", as implemented by the JSON RPC method
 * https://docs.metamask.io/guide/signing-data.html[`eth_signTypedDataV4` in MetaMask].
 *
 * NOTE: In the upgradeable version of this contract, the cached values will correspond to the address, and the domain
 * separator of the implementation contract. This will cause the {_domainSeparatorV4} function to always rebuild the
 * separator from the immutable values, which is cheaper than accessing a cached version in cold storage.
 */
abstract contract EIP712UpgradeableCrossChain is Initializable, IERC5267 {
    bytes32 private constant TYPE_HASH =
        keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)");

    /// @custom:storage-location fhevm.storage.EIP712UpgradeableCrossChain
    struct EIP712Storage {
        /// @custom:oz-renamed-from _HASHED_NAME
        bytes32 _hashedName;
        /// @custom:oz-renamed-from _HASHED_VERSION
        bytes32 _hashedVersion;
        string _name;
        string _version;
        address _verifyingContractSource;
        uint64 _chainIDSource;
    }

    /// keccak256(abi.encode(uint256(keccak256("fhevm.storage.EIP712UpgradeableCrossChain")) - 1)) & ~bytes32(uint256(0xff))
    bytes32 private constant EIP712UpgradeableCrossChainLocation =
        0xe910845fd818f61127c84f3586776436a37dead33625056c65162537e3373600;

    function _getEIP712Storage() private pure returns (EIP712Storage storage $) {
        assembly {
            $.slot := EIP712UpgradeableCrossChainLocation
        }
    }

    /**
     * @dev Initializes the domain separator and parameter caches.
     *
     * The meaning of `name` and `version` is specified in
     * https://eips.ethereum.org/EIPS/eip-712#definition-of-domainseparator[EIP-712]:
     *
     * - `name`: the user readable name of the signing domain, i.e. the name of the DApp or the protocol.
     * - `version`: the current major version of the signing domain.
     *
     * NOTE: These parameters cannot be changed except through a xref:learn::upgrading-smart-contracts.adoc[smart
     * contract upgrade].
     */
    function __EIP712_init(
        string memory name,
        string memory version,
        address verifyingContractSource,
        uint64 chainIDSource
    ) internal onlyInitializing {
        __EIP712_init_unchained(name, version, verifyingContractSource, chainIDSource);
    }

    function __EIP712_init_unchained(
        string memory name,
        string memory version,
        address verifyingContractSource,
        uint64 chainIDSource
    ) internal onlyInitializing {
        EIP712Storage storage $ = _getEIP712Storage();
        $._verifyingContractSource = verifyingContractSource;
        $._chainIDSource = chainIDSource;
        $._name = name;
        $._version = version;

        // Reset prior values in storage if upgrading
        $._hashedName = 0;
        $._hashedVersion = 0;
    }

    /**
     * @dev Returns the domain separator for the current chain.
     */
    function _domainSeparatorV4() internal view returns (bytes32) {
        return _buildDomainSeparator();
    }

    function _buildDomainSeparator() private view returns (bytes32) {
        EIP712Storage storage $ = _getEIP712Storage();
        return
            keccak256(
                abi.encode(
                    TYPE_HASH,
                    _EIP712NameHash(),
                    _EIP712VersionHash(),
                    $._chainIDSource,
                    $._verifyingContractSource
                )
            );
    }

    /**
     * @dev Given an already https://eips.ethereum.org/EIPS/eip-712#definition-of-hashstruct[hashed struct], this
     * function returns the hash of the fully encoded EIP712 message for this domain.
     *
     * This hash can be used together with {ECDSA-recover} to obtain the signer of a message. For example:
     *
     * ```solidity
     * bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
     *     keccak256("Mail(address to,string contents)"),
     *     mailTo,
     *     keccak256(bytes(mailContents))
     * )));
     * address signer = ECDSA.recover(digest, signature);
     * ```
     */
    function _hashTypedDataV4(bytes32 structHash) internal view virtual returns (bytes32) {
        return MessageHashUtils.toTypedDataHash(_domainSeparatorV4(), structHash);
    }

    /**
     * @dev See {IERC-5267}.
     */
    function eip712Domain()
        public
        view
        virtual
        returns (
            bytes1 fields,
            string memory name,
            string memory version,
            uint256 chainId,
            address verifyingContract,
            bytes32 salt,
            uint256[] memory extensions
        )
    {
        EIP712Storage storage $ = _getEIP712Storage();
        // If the hashed name and version in storage are non-zero, the contract hasn't been properly initialized
        // and the EIP712 domain is not reliable, as it will be missing name and version.
        require($._hashedName == 0 && $._hashedVersion == 0, "EIP712: Uninitialized");

        return (
            hex"0f", // 01111
            _EIP712Name(),
            _EIP712Version(),
            $._chainIDSource,
            $._verifyingContractSource,
            bytes32(0),
            new uint256[](0)
        );
    }

    /**
     * @dev The name parameter for the EIP712 domain.
     *
     * NOTE: This function reads from storage by default, but can be redefined to return a constant value if gas costs
     * are a concern.
     */
    function _EIP712Name() internal view virtual returns (string memory) {
        EIP712Storage storage $ = _getEIP712Storage();
        return $._name;
    }

    /**
     * @dev The version parameter for the EIP712 domain.
     *
     * NOTE: This function reads from storage by default, but can be redefined to return a constant value if gas costs
     * are a concern.
     */
    function _EIP712Version() internal view virtual returns (string memory) {
        EIP712Storage storage $ = _getEIP712Storage();
        return $._version;
    }

    /**
     * @dev The hash of the name parameter for the EIP712 domain.
     *
     * NOTE: In previous versions this function was virtual. In this version you should override `_EIP712Name` instead.
     */
    function _EIP712NameHash() internal view returns (bytes32) {
        EIP712Storage storage $ = _getEIP712Storage();
        string memory name = _EIP712Name();
        if (bytes(name).length > 0) {
            return keccak256(bytes(name));
        } else {
            // If the name is empty, the contract may have been upgraded without initializing the new storage.
            // We return the name hash in storage if non-zero, otherwise we assume the name is empty by design.
            bytes32 hashedName = $._hashedName;
            if (hashedName != 0) {
                return hashedName;
            } else {
                return keccak256("");
            }
        }
    }

    /**
     * @dev The hash of the version parameter for the EIP712 domain.
     *
     * NOTE: In previous versions this function was virtual. In this version you should override `_EIP712Version` instead.
     */
    function _EIP712VersionHash() internal view returns (bytes32) {
        EIP712Storage storage $ = _getEIP712Storage();
        string memory version = _EIP712Version();
        if (bytes(version).length > 0) {
            return keccak256(bytes(version));
        } else {
            // If the version is empty, the contract may have been upgraded without initializing the new storage.
            // We return the version hash in storage if non-zero, otherwise we assume the version is empty by design.
            bytes32 hashedVersion = $._hashedVersion;
            if (hashedVersion != 0) {
                return hashedVersion;
            } else {
                return keccak256("");
            }
        }
    }
}