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contracts...ShibaBlastarDistributor.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
import "@openzeppelin/contracts/utils/cryptography/MessageHashUtils.sol";

/**
 * ShibaBlastarDistributor
 *
 * Allows users to claim ShibaBlastar tokens using a server-signed voucher.
 * The server (Symfony) signs the claim off-chain; the user broadcasts the
 * transaction and pays gas fees themselves.
 */
contract ShibaBlastarDistributor is Ownable {

    IERC20 public immutable token;

    // Address that holds the ShibaBlastar tokens and has approved this contract
    address public tokenHolder;

    // Nonces used to prevent replay attacks
    mapping(uint256 => bool) private _usedNonces;

    event TokensClaimed(address indexed recipient, uint256 amount, uint256 nonce);
    event TokenHolderUpdated(address indexed previousHolder, address indexed newHolder);

    constructor(address tokenAddress, address _tokenHolder) Ownable(msg.sender) {
        token = IERC20(tokenAddress);
        tokenHolder = _tokenHolder;
    }

    /**
     * Claim tokens using a server-signed voucher.
     *
     * The server signs off-chain:
     *   keccak256(abi.encodePacked(recipientAddress, amount, nonce))
     *
     * @param amount    Amount of tokens to claim (in wei, 18 decimals)
     * @param nonce     Unique identifier for this claim (from server)
     * @param signature ECDSA signature produced by the server (owner)
     */
    function claimTokens(uint256 amount, uint256 nonce, bytes memory signature) external {
        require(!_usedNonces[nonce], "Nonce already used");
        require(amount > 0, "Amount must be greater than zero");

        bytes32 message = keccak256(abi.encodePacked(msg.sender, amount, nonce));
        bytes32 ethSignedMessage = MessageHashUtils.toEthSignedMessageHash(message);

        address signer = ECDSA.recover(ethSignedMessage, signature);
        require(signer == owner(), "Invalid signature");

        _usedNonces[nonce] = true;

        require(
            token.transferFrom(tokenHolder, msg.sender, amount),
            "Token transfer failed"
        );

        emit TokensClaimed(msg.sender, amount, nonce);
    }

    /**
     * Check if a nonce has already been used.
     */
    function isNonceUsed(uint256 nonce) external view returns (bool) {
        return _usedNonces[nonce];
    }

    /**
     * Update the token holder address (onlyOwner).
     */
    function setTokenHolder(address _tokenHolder) external onlyOwner {
        emit TokenHolderUpdated(tokenHolder, _tokenHolder);
        tokenHolder = _tokenHolder;
    }
}