Minuscule.sol

/// SPDX-License-Identifier: MIT

/// @title Minuscule Key-Value Store
/// @notice A contract that allows users to store and retrieve key-value pairs on-chain
/// @dev Uses EIP-712 signatures to ensure that only authorized relayers can execute key-value changes
/// @dev Users sign a message that authorizes a specific relayer address to execute the change
/// @dev The signature acts as an API key, and is only valid for a certain period of time
contract Minuscule {
    using ECDSA for bytes32;

    mapping(address => mapping(bytes32 => bytes32)) private store;

    /// @notice Sets a key-value pair for the calling user
    /// @dev Requires a valid EIP-712 signature from an authorized relayer
    /// @param dataKey The key for the data to be stored
    /// @param value The value of the data to be stored
    /// @param deadline The timestamp by which the signature must be executed
    /// @param relayer The address of the authorized relayer that can execute the signature
    /// @param signature The EIP-712 signature that authorizes the relayer to execute the change
    function set(bytes32 dataKey, bytes32 value, uint256 deadline, address relayer, bytes memory signature) public {
        require(block.timestamp <= deadline, "Expired signature");
        require(relayer != address(0), "Invalid relayer address");

        bytes32 message = getMessage(dataKey, value, deadline, relayer);
        address signer = message.recover(signature);
        require(signer == relayer, "Invalid signature");

        store[msg.sender][dataKey] = value;
    }

    /// @notice Gets the value of a key for the calling user
    /// @param dataKey The key for the data to retrieve
    /// @return The value of the data stored at the specified key
    function get(bytes32 dataKey) public view returns (bytes32) {
        return store[msg.sender][dataKey];
    }

    /// @notice Returns the EIP-712 hash of a message
    /// @param dataKey The key for the data to be stored
    /// @param value The value of the data to be stored
    /// @param deadline The timestamp by which the signature must be executed
    /// @param relayer The address of the authorized relayer that can execute the signature
    /// @return The EIP-712 hash of the message
    function getMessage(bytes32 dataKey, bytes32 value, uint256 deadline, address relayer) private view returns (bytes32) {
        return keccak256(abi.encodePacked(dataKey, value, deadline, relayer, address(this)));
    }
}