// Sources flattened with hardhat v2.7.0 https://hardhat.org

// File @openzeppelin/contracts/token/ERC20/IERC20.sol@v4.5.0

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}


/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}


pragma solidity ^0.8.0;

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}


pragma solidity ^0.8.4;


contract Claim is Ownable {

    mapping(uint => bool) used_nonces;
    address token;

    struct ClaimRequest {
        uint256 nonce;
        uint256 amount;
        address to;
        bytes signature;
    }

    event ClaimSuccessful(uint256 indexed nonce, uint256 amount, address to);
    event ClaimCancelled(uint256 indexed nonce);

    constructor(address _token, address owner) {
        token = _token;
        Ownable._transferOwnership(owner);
    }

    function verify_signatures(bytes memory signature, bytes memory message) pure public returns(address) {
        require(signature.length == 65, "invalid signature length");

        bytes32 message_hash = keccak256(message);

        bytes32 r;
        bytes32 s;
        uint8 v;
        assembly {
            r := mload(add(signature, 32))
            s := mload(add(signature, 64))
            v := byte(0, mload(add(signature, 96)))
        }
        
        if (v < 27) v += 27;

        if (v != 27 && v != 28) {
            return (address(0));
        } else {
            // solium-disable-next-line arg-overflow
            return ecrecover(message_hash, v, r, s);
        }
    }

    function claim(uint256 nonce, uint256 amount, address to, bytes memory signature) public {
        require(!used_nonces[nonce], "nonce already used");
        IERC20(token).transfer(to, amount);
        address signedBy = verify_signatures(signature, abi.encode(nonce, amount, to));
        require(signedBy == Ownable.owner(), "Invalid signature");
        used_nonces[nonce] = true;
        emit ClaimSuccessful(nonce, amount, to);
    }

    function claims(ClaimRequest[] memory _claims) public {
        for (uint i = 0; i < _claims.length; i++) {
            ClaimRequest memory _claim = _claims[i];
            claim(_claim.nonce, _claim.amount, _claim.to, _claim.signature);
        }
    }

    function isClaimed(uint256[] memory nonces) view public returns (bool[] memory) {
        bool[] memory response = new bool[](nonces.length);
        for (uint i = 0; i < nonces.length; i++) {
            response[i] = used_nonces[nonces[i]];
        }
        return response;
    }

    function cancelClaims(uint256[] memory nonces) public {
        for (uint i = 0; i < nonces.length; i++) {
            used_nonces[nonces[i]] = true;
            emit ClaimCancelled(nonces[i]);
        }
    }
}