// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (access/Ownable.sol)

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @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 Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        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);
    }
}

// File: @openzeppelin/contracts/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// File: @openzeppelin/contracts/token/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC721/IERC721.sol)

pragma solidity ^0.8.0;

import "../../utils/introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Note that the caller is responsible to confirm that the recipient is capable of receiving ERC721
     * or else they may be permanently lost. Usage of {safeTransferFrom} prevents loss, though the caller must
     * understand this adds an external call which potentially creates a reentrancy vulnerability.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @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;
    }
}

// File: @openzeppelin/contracts/utils/introspection/IERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// File: @openzeppelin/contracts/utils/structs/EnumerableSet.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/structs/EnumerableSet.sol)
// This file was procedurally generated from scripts/generate/templates/EnumerableSet.js.

pragma solidity ^0.8.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 *
 * [WARNING]
 * ====
 * Trying to delete such a structure from storage will likely result in data corruption, rendering the structure
 * unusable.
 * See https://github.com/ethereum/solidity/pull/11843[ethereum/solidity#11843] for more info.
 *
 * In order to clean an EnumerableSet, you can either remove all elements one by one or create a fresh instance using an
 * array of EnumerableSet.
 * ====
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;
        // Position of the value in the `values` array, plus 1 because index 0
        // means a value is not in the set.
        mapping(bytes32 => uint256) _indexes;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function _add(Set storage set, bytes32 value) private returns (bool) {
        if (!_contains(set, value)) {
            set._values.push(value);
            // The value is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            set._indexes[value] = set._values.length;
            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function _remove(Set storage set, bytes32 value) private returns (bool) {
        // We read and store the value's index to prevent multiple reads from the same storage slot
        uint256 valueIndex = set._indexes[value];

        if (valueIndex != 0) {
            // Equivalent to contains(set, value)
            // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
            // the array, and then remove the last element (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = valueIndex - 1;
            uint256 lastIndex = set._values.length - 1;

            if (lastIndex != toDeleteIndex) {
                bytes32 lastValue = set._values[lastIndex];

                // Move the last value to the index where the value to delete is
                set._values[toDeleteIndex] = lastValue;
                // Update the index for the moved value
                set._indexes[lastValue] = valueIndex; // Replace lastValue's index to valueIndex
            }

            // Delete the slot where the moved value was stored
            set._values.pop();

            // Delete the index for the deleted slot
            delete set._indexes[value];

            return true;
        } else {
            return false;
        }
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function _contains(Set storage set, bytes32 value) private view returns (bool) {
        return set._indexes[value] != 0;
    }

    /**
     * @dev Returns the number of values on the set. O(1).
     */
    function _length(Set storage set) private view returns (uint256) {
        return set._values.length;
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function _at(Set storage set, uint256 index) private view returns (bytes32) {
        return set._values[index];
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function _values(Set storage set) private view returns (bytes32[] memory) {
        return set._values;
    }

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _add(set._inner, value);
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
        return _remove(set._inner, value);
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
        return _contains(set._inner, value);
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(Bytes32Set storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
        return _at(set._inner, index);
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(Bytes32Set storage set) internal view returns (bytes32[] memory) {
        bytes32[] memory store = _values(set._inner);
        bytes32[] memory result;

        /// @solidity memory-safe-assembly
        assembly {
            result := store
        }

        return result;
    }

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(AddressSet storage set, address value) internal returns (bool) {
        return _add(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(AddressSet storage set, address value) internal returns (bool) {
        return _remove(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(AddressSet storage set, address value) internal view returns (bool) {
        return _contains(set._inner, bytes32(uint256(uint160(value))));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(AddressSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(AddressSet storage set, uint256 index) internal view returns (address) {
        return address(uint160(uint256(_at(set._inner, index))));
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(AddressSet storage set) internal view returns (address[] memory) {
        bytes32[] memory store = _values(set._inner);
        address[] memory result;

        /// @solidity memory-safe-assembly
        assembly {
            result := store
        }

        return result;
    }

    // UintSet

    struct UintSet {
        Set _inner;
    }

    /**
     * @dev Add a value to a set. O(1).
     *
     * Returns true if the value was added to the set, that is if it was not
     * already present.
     */
    function add(UintSet storage set, uint256 value) internal returns (bool) {
        return _add(set._inner, bytes32(value));
    }

    /**
     * @dev Removes a value from a set. O(1).
     *
     * Returns true if the value was removed from the set, that is if it was
     * present.
     */
    function remove(UintSet storage set, uint256 value) internal returns (bool) {
        return _remove(set._inner, bytes32(value));
    }

    /**
     * @dev Returns true if the value is in the set. O(1).
     */
    function contains(UintSet storage set, uint256 value) internal view returns (bool) {
        return _contains(set._inner, bytes32(value));
    }

    /**
     * @dev Returns the number of values in the set. O(1).
     */
    function length(UintSet storage set) internal view returns (uint256) {
        return _length(set._inner);
    }

    /**
     * @dev Returns the value stored at position `index` in the set. O(1).
     *
     * Note that there are no guarantees on the ordering of values inside the
     * array, and it may change when more values are added or removed.
     *
     * Requirements:
     *
     * - `index` must be strictly less than {length}.
     */
    function at(UintSet storage set, uint256 index) internal view returns (uint256) {
        return uint256(_at(set._inner, index));
    }

    /**
     * @dev Return the entire set in an array
     *
     * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
     * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
     * this function has an unbounded cost, and using it as part of a state-changing function may render the function
     * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
     */
    function values(UintSet storage set) internal view returns (uint256[] memory) {
        bytes32[] memory store = _values(set._inner);
        uint256[] memory result;

        /// @solidity memory-safe-assembly
        assembly {
            result := store
        }

        return result;
    }
}

// File: contracts/Auction.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.17;

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import '@openzeppelin/contracts/utils/structs/EnumerableSet.sol';

/// ~~~ +++ LOVE TO DOODLES +++ ~~~

/// @author FlowCarbon LLC
/// @title A bucket auction for flow3rs
contract Auction is ReentrancyGuard, Ownable  {

    using EnumerableSet for EnumerableSet.AddressSet;

    uint256 public minimumIncrement = 0.001 ether;
    uint256 public minimumContribution = 0.1 ether;
    bytes32 public distributionOrderHash;

    IERC721 public nft;
    uint256 public numNFTs;
    uint256[] public nftIds;

    struct User {
        uint256 firstBidAt; // number of the last bid
        uint256 contribution; // cumulative sum of ETH bids
        uint32 tokensClaimed; // tracker for claimed tokens
        bool refundClaimed; // has user been refunded yet
    }
    mapping(address => User) public userData;
    EnumerableSet.AddressSet private bidders;

    uint256 public price;

    address public auctioneer;
    address payable public immutable withdrawAddress;
    bool public auctionActive;

    event Bid(address bidder, uint256 bidAmount, uint256 bidderTotal, uint256 bucketTotal);

    constructor(IERC721 nft_, address payable withdrawAddress_, address auctioneer_, address owner_) {
        require(withdrawAddress_ != address(0), "!withdrawAddress_");
        require(auctioneer_ != address(0), "!auctioneer_");
        require(owner_ != address(0), "!owner_");

        withdrawAddress = withdrawAddress_;
        auctioneer = auctioneer_;
        nft = nft_;
        _transferOwnership(owner_);
    }

    modifier isAuctionActive() {
        require(auctionActive, "Auction is not active");
        _;
    }

    /**
     * @notice Sets the distribution order hash.
     * @param distributionOrderHash_ - the distribution hash
     */
    function setDistributionOrderHash(bytes32 distributionOrderHash_) external onlyOwner {
        require(price == 0, "Price has been set");
        require(!auctionActive, "Auction already active");
        distributionOrderHash = distributionOrderHash_;
    }

    /**
     * @notice Adds a token to the auction - the token has to be approved by the auctioneer
     * @param tokenId_ - the the token id
     */
    function addTokenToAuction(uint256 tokenId_) public onlyOwner {
        require(price == 0, "Price has been set");
        require(!auctionActive, "Auction already active");

        nft.transferFrom(auctioneer, address(this), tokenId_);
        numNFTs++;
    }

    /**
     * @notice Batch adds tokens to the auction - the tokens have to be approved by the auctioneer
     * @param tokenIds_ - the the token ids to transfer in
     */
    function batchAddTokenToAuction(uint256[] memory tokenIds_) external onlyOwner {
        for (uint256 i=0; i < tokenIds_.length; ++i) {
            addTokenToAuction(tokenIds_[i]);
        }
    }

   /**
    * @notice begin the auction.
    * @dev cannot be reactivated after price has been set.
    * @param isActive_ set 'true' to start auction, set 'false' to stop auction.
    */
    function setAuctionActive(bool isActive_) external onlyOwner {
        require(distributionOrderHash != bytes32(0), "Distribution order hash not set");
        require(price == 0, "Price has been set");
        auctionActive = isActive_;
    }

   /**
    * @notice place a bid in ETH or add to your existing bid. Calling this
    *   multiple times will increase your bid amount. All bids placed are final
    *   and cannot be reversed.
    */
    function bid() external payable isAuctionActive {
        require(msg.value >= minimumIncrement, "Lower than min increment");
        User storage bidder = userData[msg.sender]; // get user's current bid total
        uint256 contribution_ = bidder.contribution; // bidder.contribution is uint216
        unchecked { // does not overflow
            contribution_ += msg.value;
        }
        require(contribution_ >= minimumContribution, "Lower than min bid amount");
        bidder.contribution = uint216(contribution_);

        if (bidder.firstBidAt == 0) {
            bidder.firstBidAt = block.number;
        }

        bidders.add(msg.sender);
        emit Bid(msg.sender, msg.value, contribution_, address(this).balance);
    }

   /**
    * @notice set the minimum contribution required to place a bid
    * @dev set this price in wei, not eth!
    * @param minimumContributionInWei_ new price, set in wei
    */
    function setMinimumContribution(uint256 minimumContributionInWei_) external onlyOwner {
        minimumContribution = minimumContributionInWei_;
    }

    /**
    * @notice set the clearing price after all bids have been placed.
    * @dev set this price in wei, not eth!
    * @param priceInWei_ new price, set in wei
    */
    function setPrice(uint256 priceInWei_) external onlyOwner {
        require(!auctionActive, "Users can still add bids");
        price = priceInWei_;
    }

    /**
     * @notice Adds a tokenId to the final distribution order
     * @param tokenId_ - the the token id
     */
    function addIdToDistributionOrder(uint256 tokenId_) public onlyOwner {
        nftIds.push(tokenId_);
    }

    /**
     * @notice Emergency recover in case of an error
     */
    function popDistributionOrder() public onlyOwner {
        nftIds.pop();
    }

    /**
     * @notice Batch adds a tokenId to the final distribution order
     * @param tokenIds_ - the the token ids to transfer in
     */
    function batchAddIdToDistributionOrder(uint256[] memory tokenIds_) external onlyOwner {
        for (uint256 i=0; i < tokenIds_.length; ++i) {
            addIdToDistributionOrder(tokenIds_[i]);
        }
    }

    /**
    * @dev handles multiple send tokens methods.
    * @param to address to send tokens to.
    * @param n number of tokens to send.
    */
    function _sendTokens(address to, uint256 n) internal {
        uint256 price_ = price; // storage to memory
        require(price_ != 0, "Price has not been set");

        User storage user = userData[to]; // get user data
        uint256 claimed_ = user.tokensClaimed; // user.tokensClaimed is uint32
        claimed_ += n;

        require(
            claimed_ <= _amountPurchased(user.contribution, price_),
            "Trying to send more than they purchased."
        );
        user.tokensClaimed = uint32(claimed_);
        _internalSend(to, n);
    }

    /**
     * @dev sends out the tokens from treasury, last added first out
     * @param to_ - the receiver
     * @param n_ - amount of tokens purchased
     */
    function _internalSend(address to_, uint256 n_) internal {
        require(nftIds.length == numNFTs, "distribution order not set");
        require(nftIds.length > 0, "no tokens remaining");
        for (uint256 i=0; i < n_; ++i) {
            nft.transferFrom(address(this), to_, nftIds[nftIds.length - (i + 1)]);
        }

        numNFTs -= n_;
        for (uint256 i=0; i < n_; ++i){
            nftIds.pop();
        }
    }

    /**
    * @notice get the number of tokens purchased by an address, after the
    *   clearing price has been set.
    * @param a address to query.
    */
    function amountPurchased(address a) public view returns (uint256) {
        return userData[a].contribution / price;
    }

    /**
    * @dev use to get amountPurchased() for arbitrary contribution and price
    * @param _contribution theoretical bid contribution
    * @param _price theoretical clearing price
    */
    function _amountPurchased(uint256 _contribution, uint256 _price)
        internal
        pure
        returns (uint256)
    {
        return _contribution / _price;
    }

    /**
    * @notice get the refund amount for an account, after the clearing price
    *   has been set.
    * @param a address to query.
    */
    function refundAmount(address a) public view returns (uint256) {
        return userData[a].contribution % price;
    }

    /**
    * @dev helper to get refundAmount() for arbitrary contribution and price
    * @param _contribution theoretical bid contribution
    * @param _price theoretical clearing price
    */
    function _refundAmount(uint256 _contribution, uint256 _price)
        internal
        pure
        returns (uint256)
    {
        return _contribution % _price;
    }

    // functions for project owner to pay to send tokens/refund

    /**
    * @notice sends tokens to an address.
    * @dev purchased amount for an address can be sent in multiple calls.
    *   Can only be called after clearing price has been set.
    * @param to address to send tokens to.
    * @param n number of tokens to send.
    */
    function sendTokens(address to, uint256 n) public onlyOwner {
        _sendTokens(to, n);
    }

    /**
    * @notice send all of an address's purchased tokens.
    * @dev if some tokens have already been sent, the remainder must be sent
    *   using sendTokens().
    * @param to address to send tokens to.
    */
    function sendAllTokens(address to) public onlyOwner {
        _sendTokens(to, amountPurchased(to));
    }

    /**
    * @notice send refund to an address. Refunds are unsuccessful bids or
    *   an address's remaining eth after all their tokens have been paid for.
    * @dev can only be called after the clearing price has been set.
    * @param to the address to refund.
    */
    function sendRefund(address to) public onlyOwner nonReentrant {
        uint256 price_ = price; // storage to memory
        require(price_ != 0, "Price has not been set");

        User storage user = userData[to]; // get user data
        require(!user.refundClaimed, "Address has already claimed their refund.");
        user.refundClaimed = true;

        uint256 refundValue = _refundAmount(user.contribution, price_);
        (bool success, ) = to.call{value: refundValue}("");
        require(success, "Refund failed.");
    }

    /**
    * @notice send refunds to a batch of addresses.
    * @param addresses array of addresses to refund.
    */
    function sendRefundBatch(address[] calldata addresses) external onlyOwner {
        for (uint256 i; i < addresses.length; i++) {
            sendRefund(addresses[i]);
        }
    }

    /**
    * @notice send tokens to a batch of addresses.
    * @param addresses array of addresses to send tokens to.
    */
    function sendTokensBatch(address[] calldata addresses) external onlyOwner{
        for (uint256 i; i < addresses.length; i++) {
            _sendTokens(addresses[i], amountPurchased(addresses[i]));
        }
    }

    /**
    * @notice send refunds and tokens to an address.
    * @dev can only be called after the clearing price has been set.
    * @param to the address to refund.
    */
    function sendTokensAndRefund(address to) public onlyOwner nonReentrant {
        uint256 price_ = price;
        require(price_ != 0, "Price has not been set");

        User storage user = userData[to]; // get user data
        uint256 userContribution = user.contribution;

        // send refund
        require(!user.refundClaimed, "Already sent refunds to this address.");
        user.refundClaimed = true;
        uint256 refundValue = _refundAmount(userContribution, price_);

        if (refundValue > 0) {
            (bool success, ) = to.call{value: refundValue}("");
            require(success, "Refund failed.");
        }

        // send tokens
        uint256 n = _amountPurchased(userContribution, price_);
        if (n > 0) {
            require(user.tokensClaimed == 0, "Already sent tokens to this address.");
            user.tokensClaimed = uint32(n);
            _internalSend(to, n);
        }
    }

    /**
    * @notice send refunds and tokens to a batch of addresses.
    * @param addresses array of addresses to send tokens to.
    */
    function sendTokensAndRefundBatch(address[] calldata addresses) external onlyOwner {
        for (uint256 i; i < addresses.length; i++) {
            sendTokensAndRefund(addresses[i]);
        }
    }

    /**
    * @return the number of bids
    */
    function numBidders() external view returns (uint256) {
        return bidders.length();
    }

    /**
     * @param ix_ the index of the bidder
     * @return bidder address
     */
    function bidderAtIndex(uint256 ix_) external view returns (address) {
        return bidders.at(ix_);
    }

    function deposit() external payable onlyOwner {
        return;
    }

    /**
     * @dev withdraw function for owner.
     */
    function withdraw() external onlyOwner {
        (bool success, ) = withdrawAddress.call{value: address(this).balance}("");
        require(success, "Transfer failed.");
    }

     /**
     * @dev withdraw nft function for owner.
     */
    function withdrawNFT(uint256 tokenId_) external onlyOwner {
        nft.transferFrom(address(this), withdrawAddress, tokenId_);
        numNFTs--;
    }
}