// SPDX-License-Identifier: Apache-2.0
pragma solidity ^0.8.19;

// interfaces

// libraries
import {EIP712Lib, EIP712Storage} from "../../primitive/EIP712.sol";

// contracts

/**
 * @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 EIP712Base {
    using EIP712Lib for EIP712Storage;

    bytes32 private constant TYPE_HASH = keccak256(
        "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
    );

    // keccak256(abi.encode(uint256(keccak256("diamond.utils.cryptography.eip712.storage")) - 1)) & ~bytes32(uint256(0xff))
    bytes32 internal constant STORAGE_SLOT =
        0x219639d1c7dec7d049ffb8dc11e39f070f052764b142bd61682a7811a502a600;

    function _getEIP712Storage() internal pure virtual returns (EIP712Storage storage $) {
        assembly {
            $.slot := STORAGE_SLOT
        }
    }

    function __EIP712_init_unchained(string memory name, string memory version) internal virtual {
        EIP712Storage storage $ = _getEIP712Storage();
        $.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 virtual returns (bytes32) {
        // Build domain separator using the virtual functions
        // This allows overrides to work correctly
        return keccak256(
            abi.encode(
                TYPE_HASH, _EIP712NameHash(), _EIP712VersionHash(), block.chainid, address(this)
            )
        );
    }

    /**
     * @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 EIP712Lib.toTypedDataHash(_domainSeparatorV4(), structHash);
    }

    /**
     * @dev Returns the domain name and version.
     * This function should be overridden by facets that want to use constant values
     * instead of reading from storage for gas optimization.
     */
    function _domainNameAndVersion()
        internal
        view
        virtual
        returns (string memory name, string memory version)
    {
        // Default implementation reads from storage
        EIP712Storage storage $ = _getEIP712Storage();
        name = $._EIP712Name();
        version = $._EIP712Version();
    }

    /**
     * @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) {
        (string memory name,) = _domainNameAndVersion();
        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) {
        (, string memory version) = _domainNameAndVersion();
        return version;
    }

    /**
     * @dev The hash of 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 _EIP712NameHash() internal view virtual returns (bytes32) {
        string memory name = _EIP712Name();
        return bytes(name).length > 0 ? keccak256(bytes(name)) : keccak256("");
    }

    /**
     * @dev The hash of 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 _EIP712VersionHash() internal view virtual returns (bytes32) {
        string memory version = _EIP712Version();
        return bytes(version).length > 0 ? keccak256(bytes(version)) : keccak256("");
    }
}