Contract Address Details

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

/**
 * @title Simple NFT Marketplace
 * @notice Fixed-price marketplace with ERC-2981 support
 * @dev Uses pull-over-push payments. Platform fee capped at 3.69%.
 */

import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";
import "@openzeppelin/contracts/utils/Address.sol";

interface IERC2981 {
    function royaltyInfo(uint256 tokenId, uint256 salePrice)
        external
        view
        returns (address receiver, uint256 royaltyAmount);
}

contract NFTMarketplace is ReentrancyGuard, Ownable {
    using Address for address payable;
    
    bytes4 private constant _INTERFACE_ID_ERC2981 = 0x2a55205a;
    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;
    uint256 private constant MAX_BATCH_SIZE = 20;
    
    bool private _paused;

    struct Listing {
        address seller;
        uint256 price;
        bool active;
    }

    // nftContract => tokenId => Listing
    mapping(address => mapping(uint256 => Listing)) public listings;
    mapping(address => uint256) private _pendingPayments;
    mapping(address => uint256) public failedRoyalties;
    
    uint256 public platformFee = 69; // 0.69% in basis points
    uint256 public constant MAX_FEE = 369; // 3.69% max
    uint256 public totalPlatformFees;

    // Events
    event NFTListed(address indexed nftContract, uint256 indexed tokenId, address seller, uint256 price);
    event NFTPriceUpdated(address indexed nftContract, uint256 indexed tokenId, uint256 oldPrice, uint256 newPrice);
    event NFTSold(address indexed nftContract, uint256 indexed tokenId, address buyer, uint256 price, uint256 royaltyAmount, address royaltyRecipient, bool royaltyPaid);
    event NFTDelisted(address indexed nftContract, uint256 indexed tokenId, address indexed seller);
    event PlatformFeeUpdated(uint256 newFee);
    event PaymentReleased(address indexed to, uint256 amount);
    event RoyaltyPaymentFailed(address indexed recipient, uint256 amount);
    event RoyaltyClaimed(address indexed recipient, uint256 amount);
    event BatchPurchased(uint256 itemCount, uint256 successfulCount, uint256 totalSpent);
    event BatchPurchaseRefund(address indexed buyer, uint256 refundAmount, uint256 failedItems);
    event Paused(address account);
    event Unpaused(address account);

    modifier whenNotPaused() {
        require(!_paused, "Contract paused");
        _;
    }

    constructor() Ownable(msg.sender) {}

    // ============ LISTING FUNCTIONS ============

    function listNFT(address nftContract, uint256 tokenId, uint256 price) 
        external 
        nonReentrant 
        whenNotPaused 
    {
        _validateAndList(nftContract, tokenId, price, msg.sender);
    }

    function updatePrice(address nftContract, uint256 tokenId, uint256 newPrice) 
        external 
        nonReentrant 
        whenNotPaused 
    {
        require(newPrice > 0, "Price must be > 0");
        Listing storage listing = listings[nftContract][tokenId];
        require(listing.active && listing.seller == msg.sender, "Not seller or not active");
        
        // Verify caller still owns the NFT
        IERC721 nft = IERC721(nftContract);
        require(nft.ownerOf(tokenId) == msg.sender, "Not owner");
        
        _validateNFTApproval(nftContract, tokenId, listing.seller);
        
        emit NFTPriceUpdated(nftContract, tokenId, listing.price, newPrice);
        listing.price = newPrice;
    }

    /// @notice Delist a single NFT (seller only)
    function delistNFT(address nftContract, uint256 tokenId) 
        external 
        nonReentrant 
        whenNotPaused 
    {
        Listing storage listing = listings[nftContract][tokenId];
        require(listing.active && listing.seller == msg.sender, "Not seller or not active");

        listing.active = false;
        emit NFTDelisted(nftContract, tokenId, msg.sender);

        // Optional: fully delete to refund storage (saves gas on future ops)
        delete listings[nftContract][tokenId];
    }

    /// @notice Batch list NFTs (max 20)
    function batchListNFTs(
        address[] calldata nftContracts,
        uint256[] calldata tokenIds,
        uint256[] calldata prices
    ) external nonReentrant whenNotPaused {
        require(nftContracts.length == tokenIds.length && nftContracts.length == prices.length, "Length mismatch");
        require(nftContracts.length <= MAX_BATCH_SIZE, "Batch too large");
        
        for (uint256 i = 0; i < nftContracts.length; i++) {
            _validateAndList(nftContracts[i], tokenIds[i], prices[i], msg.sender);
        }
    }

    /// @notice Batch delist NFTs
    function batchDelistNFTs(address[] calldata nftContracts, uint256[] calldata tokenIds) 
        external 
        nonReentrant 
        whenNotPaused 
    {
        require(nftContracts.length == tokenIds.length, "Length mismatch");
        require(nftContracts.length <= MAX_BATCH_SIZE, "Batch too large");

        for (uint256 i = 0; i < nftContracts.length; i++) {
            Listing storage listing = listings[nftContracts[i]][tokenIds[i]];
            require(listing.active && listing.seller == msg.sender, "Not seller or not active");

            listing.active = false;
            emit NFTDelisted(nftContracts[i], tokenIds[i], msg.sender);
        }
    }

    // ============ BUYING FUNCTIONS ============

    function buyNFT(address nftContract, uint256 tokenId) 
        external 
        payable 
        nonReentrant 
        whenNotPaused 
    {
        Listing memory listing = listings[nftContract][tokenId];
        require(listing.active, "Not listed");
        require(msg.value == listing.price, "Exact payment required");
        
        (uint256 royaltyAmount, address royaltyRecipient, bool royaltyPaid) = _executePurchase(nftContract, tokenId);
        
        emit NFTSold(nftContract, tokenId, msg.sender, listing.price, royaltyAmount, royaltyRecipient, royaltyPaid);
    }

    /// @notice Fixed batch buy with accurate refunds and events
    function batchBuyNFTs(address[] calldata nftContracts, uint256[] calldata tokenIds) 
        external 
        payable 
        nonReentrant 
        whenNotPaused 
    {
        require(nftContracts.length == tokenIds.length, "Length mismatch");
        require(nftContracts.length <= MAX_BATCH_SIZE, "Batch too large");
        uint256 itemCount = nftContracts.length;
        require(itemCount > 0, "Empty batch");

        // Validate all listings and compute total required
        (uint256 totalRequired, uint256[] memory prices, address[] memory sellers) = 
            _validateBatchListings(nftContracts, tokenIds);

        require(msg.value >= totalRequired, "Insufficient payment");

        // Execute purchases
        (uint256 totalSpent, uint256 successfulPurchases) = 
            _executeBatchPurchases(nftContracts, tokenIds, prices, sellers, itemCount);

        // Refund any overpayment or failed items
        if (msg.value > totalSpent) {
            uint256 refundAmount = msg.value - totalSpent;
            _pendingPayments[msg.sender] += refundAmount;
            emit BatchPurchaseRefund(msg.sender, refundAmount, itemCount - successfulPurchases);
        }

        emit BatchPurchased(itemCount, successfulPurchases, totalSpent);
    }

    // ============ WITHDRAWAL FUNCTIONS ============

    function withdrawPayments() external nonReentrant {
        uint256 amount = _pendingPayments[msg.sender];
        require(amount > 0, "No balance");
        
        _pendingPayments[msg.sender] = 0;
        
        (bool success, ) = payable(msg.sender).call{value: amount}("");
        require(success, "Transfer failed");
        emit PaymentReleased(msg.sender, amount);
    }

    function claimFailedRoyalty() external nonReentrant {
        uint256 amount = failedRoyalties[msg.sender];
        require(amount > 0, "No royalties");
        
        failedRoyalties[msg.sender] = 0;
        
        (bool success, ) = payable(msg.sender).call{value: amount}("");
        require(success, "Transfer failed");
        emit RoyaltyClaimed(msg.sender, amount);
    }

    // ============ ADMIN FUNCTIONS ============

    function updatePlatformFee(uint256 newFee) external onlyOwner {
        require(newFee <= MAX_FEE, "Fee too high");
        platformFee = newFee;
        emit PlatformFeeUpdated(newFee);
    }

    function withdrawPlatformFees() external onlyOwner {
        uint256 amount = totalPlatformFees;
        require(amount > 0, "No fees");
        
        totalPlatformFees = 0;
        
        (bool success, ) = payable(owner()).call{value: amount}("");
        require(success, "Transfer failed");
        emit PaymentReleased(owner(), amount);
    }

    function pause() external onlyOwner {
        _paused = true;
        emit Paused(msg.sender);
    }

    function unpause() external onlyOwner {
        _paused = false;
        emit Unpaused(msg.sender);
    }

    // ============ VIEW FUNCTIONS ============

    function getListing(address nftContract, uint256 tokenId) 
        external 
        view 
        returns (address seller, uint256 price, bool active) 
    {
        Listing memory listing = listings[nftContract][tokenId];
        return (listing.seller, listing.price, listing.active);
    }

    function pendingPayment(address payee) external view returns (uint256) {
        return _pendingPayments[payee];
    }

    function paused() external view returns (bool) {
        return _paused;
    }

    // ============ INTERNAL FUNCTIONS ============

    /// @notice Validate batch listings and compute total required payment
    function _validateBatchListings(
        address[] calldata nftContracts,
        uint256[] calldata tokenIds
    ) internal view returns (uint256 totalRequired, uint256[] memory prices, address[] memory sellers) {
        uint256 itemCount = nftContracts.length;
        prices = new uint256[](itemCount);
        sellers = new address[](itemCount);
        
        for (uint256 i = 0; i < itemCount; i++) {
            Listing memory listing = listings[nftContracts[i]][tokenIds[i]];
            require(listing.active, "One or more not listed");
            prices[i] = listing.price;
            sellers[i] = listing.seller;
            totalRequired += listing.price;
        }
    }

    /// @notice Execute batch purchases with validation before each purchase
    function _executeBatchPurchases(
        address[] calldata nftContracts,
        uint256[] calldata tokenIds,
        uint256[] memory prices,
        address[] memory sellers,
        uint256 itemCount
    ) internal returns (uint256 totalSpent, uint256 successfulPurchases) {
        for (uint256 i = 0; i < itemCount; i++) {
            // Re-validate listing status and price before purchase to prevent race conditions
            Listing memory currentListing = listings[nftContracts[i]][tokenIds[i]];
            
            // Check if listing is still active and price hasn't changed
            if (currentListing.active && 
                currentListing.price == prices[i] && 
                currentListing.seller == sellers[i]) {
                
                // Attempt purchase - if it fails (e.g. transfer revert), skip and refund
                // Use address(this) to call the external helper function
                try this._tryExecutePurchase(nftContracts[i], tokenIds[i], prices[i]) 
                    returns (bool purchaseSuccess, uint256 royaltyAmount, address royaltyRecipient, bool royaltyPaid) 
                {
                    if (purchaseSuccess) {
                        totalSpent += prices[i];
                        successfulPurchases++;
                        
                        emit NFTSold(
                            nftContracts[i], 
                            tokenIds[i], 
                            msg.sender, 
                            prices[i], 
                            royaltyAmount, 
                            royaltyRecipient, 
                            royaltyPaid
                        );
                    } else {
                        // Purchase validation failed, refund
                        _pendingPayments[msg.sender] += prices[i];
                    }
                } catch {
                    // Purchase execution failed (e.g. NFT transfer reverted), refund
                    _pendingPayments[msg.sender] += prices[i];
                }
            } else {
                // Listing changed or delisted during execution, refund
                _pendingPayments[msg.sender] += prices[i];
            }
        }
    }

    function _validateAndList(address nftContract, uint256 tokenId, uint256 price, address seller) private {
        require(nftContract != address(0), "Invalid contract address");
        require(price > 0, "Price must be > 0");
        _validateNFTContract(nftContract);
        
        IERC721 nft = IERC721(nftContract);
        require(nft.ownerOf(tokenId) == seller, "Not owner");
        require(
            nft.isApprovedForAll(seller, address(this)) || nft.getApproved(tokenId) == address(this),
            "Not approved"
        );
        
        Listing storage listing = listings[nftContract][tokenId];
        if (listing.active) {
            // When updating existing listing, seller must match
            require(listing.seller == seller, "Seller mismatch on update");
            emit NFTPriceUpdated(nftContract, tokenId, listing.price, price);
        } else {
            emit NFTListed(nftContract, tokenId, seller, price);
        }
        
        listing.seller = seller;
        listing.price = price;
        listing.active = true;
    }

    function _executePurchase(address nftContract, uint256 tokenId) 
        internal 
        returns (uint256 royaltyAmount, address royaltyRecipient, bool royaltyPaid) 
    {
        Listing memory listing = listings[nftContract][tokenId];
        require(listing.active, "Not listed");
        
        listings[nftContract][tokenId].active = false;

        uint256 platformFeeAmount = (listing.price * platformFee) / 10000;
        (royaltyRecipient, royaltyAmount) = _getRoyaltyInfo(nftContract, tokenId, listing.price);
        
        uint256 sellerAmount = listing.price - platformFeeAmount;
        if (royaltyAmount > 0) {
            require(royaltyAmount < sellerAmount, "Royalty too high");
            sellerAmount -= royaltyAmount;
        }
        
        require(sellerAmount > 0, "Seller amount too low");
        
        // Transfer NFT first (Checks-Effects-Interactions)
        IERC721(nftContract).safeTransferFrom(listing.seller, msg.sender, tokenId);
        
        // Payments via pull pattern
        _pendingPayments[listing.seller] += sellerAmount;
        totalPlatformFees += platformFeeAmount;
        
        // Attempt royalty payment with gas limit to prevent griefing
        royaltyPaid = false;
        if (royaltyAmount > 0 && royaltyRecipient != address(0)) {
            (bool success, ) = royaltyRecipient.call{value: royaltyAmount, gas: 30000}("");
            if (success) {
                royaltyPaid = true;
            } else {
                failedRoyalties[royaltyRecipient] += royaltyAmount;
                emit RoyaltyPaymentFailed(royaltyRecipient, royaltyAmount);
            }
        }
        
        delete listings[nftContract][tokenId];
        
        return (royaltyAmount, royaltyRecipient, royaltyPaid);
    }

    function _getRoyaltyInfo(address nftContract, uint256 tokenId, uint256 price) 
        private
        view 
        returns (address recipient, uint256 amount) 
    {
        if (ERC165Checker.supportsInterface(nftContract, _INTERFACE_ID_ERC2981)) {
            try IERC2981(nftContract).royaltyInfo(tokenId, price) returns (address r, uint256 a) {
                if (r != address(0) && a > 0 && a < price) {
                    return (r, a);
                }
            } catch {}
        }
        return (address(0), 0);
    }

    function _validateNFTContract(address nftContract) private view {
        require(
            ERC165Checker.supportsInterface(nftContract, _INTERFACE_ID_ERC721),
            "Not ERC721"
        );
    }

    function _validateNFTApproval(address nftContract, uint256 tokenId, address seller) private view {
        IERC721 nft = IERC721(nftContract);
        require(
            nft.isApprovedForAll(seller, address(this)) || nft.getApproved(tokenId) == address(this),
            "Approval revoked"
        );
    }

    /// @notice Helper function for batch purchases that can be called externally with try-catch
    /// @dev This function is external to allow try-catch, but protected by checking msg.sender
    function _tryExecutePurchase(address nftContract, uint256 tokenId, uint256 expectedPrice) 
        external 
        returns (bool success, uint256 royaltyAmount, address royaltyRecipient, bool royaltyPaid) 
    {
        // Only allow calls from this contract (for batch purchases)
        require(msg.sender == address(this), "Internal only");
        
        // Verify price matches expected (prevents price changes during batch)
        Listing memory listing = listings[nftContract][tokenId];
        if (!listing.active || listing.price != expectedPrice) {
            return (false, 0, address(0), false);
        }
        
        // Execute purchase - if this reverts, the try-catch will catch it
        (royaltyAmount, royaltyRecipient, royaltyPaid) = _executePurchase(nftContract, tokenId);
        return (true, royaltyAmount, royaltyRecipient, royaltyPaid);
    }

    receive() external payable {}
}
        

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (utils/introspection/IERC165.sol)

pragma solidity >=0.4.16;

/**
 * @dev Interface of the ERC-165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[ERC].
 *
 * 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[ERC 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);
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.1) (utils/Context.sol)

pragma solidity ^0.8.20;

/**
 * @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;
    }

    function _contextSuffixLength() internal view virtual returns (uint256) {
        return 0;
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (utils/Errors.sol)

pragma solidity ^0.8.20;

/**
 * @dev Collection of common custom errors used in multiple contracts
 *
 * IMPORTANT: Backwards compatibility is not guaranteed in future versions of the library.
 * It is recommended to avoid relying on the error API for critical functionality.
 *
 * _Available since v5.1._
 */
library Errors {
    /**
     * @dev The ETH balance of the account is not enough to perform the operation.
     */
    error InsufficientBalance(uint256 balance, uint256 needed);

    /**
     * @dev A call to an address target failed. The target may have reverted.
     */
    error FailedCall();

    /**
     * @dev The deployment failed.
     */
    error FailedDeployment();

    /**
     * @dev A necessary precompile is missing.
     */
    error MissingPrecompile(address);
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (token/ERC721/IERC721.sol)

pragma solidity >=0.6.2;

import {IERC165} from "../../utils/introspection/IERC165.sol";

/**
 * @dev Required interface of an ERC-721 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 ERC-721 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 ERC-721
     * 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 address zero.
     *
     * 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);
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.9.0) (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;
    }

    /**
     * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
     * `nonReentrant` function in the call stack.
     */
    function _reentrancyGuardEntered() internal view returns (bool) {
        return _status == _ENTERED;
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.0.0) (access/Ownable.sol)

pragma solidity ^0.8.20;

import {Context} from "../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.
 *
 * The initial owner is set to the address provided by the deployer. 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;

    /**
     * @dev The caller account is not authorized to perform an operation.
     */
    error OwnableUnauthorizedAccount(address account);

    /**
     * @dev The owner is not a valid owner account. (eg. `address(0)`)
     */
    error OwnableInvalidOwner(address owner);

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the address provided by the deployer as the initial owner.
     */
    constructor(address initialOwner) {
        if (initialOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _transferOwnership(initialOwner);
    }

    /**
     * @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 {
        if (owner() != _msgSender()) {
            revert OwnableUnauthorizedAccount(_msgSender());
        }
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby disabling 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 {
        if (newOwner == address(0)) {
            revert OwnableInvalidOwner(address(0));
        }
        _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);
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.1.0) (utils/introspection/ERC165Checker.sol)

pragma solidity ^0.8.20;

import {IERC165} from "./IERC165.sol";

/**
 * @dev Library used to query support of an interface declared via {IERC165}.
 *
 * Note that these functions return the actual result of the query: they do not
 * `revert` if an interface is not supported. It is up to the caller to decide
 * what to do in these cases.
 */
library ERC165Checker {
    // As per the ERC-165 spec, no interface should ever match 0xffffffff
    bytes4 private constant INTERFACE_ID_INVALID = 0xffffffff;

    /**
     * @dev Returns true if `account` supports the {IERC165} interface.
     */
    function supportsERC165(address account) internal view returns (bool) {
        // Any contract that implements ERC-165 must explicitly indicate support of
        // InterfaceId_ERC165 and explicitly indicate non-support of InterfaceId_Invalid
        return
            supportsERC165InterfaceUnchecked(account, type(IERC165).interfaceId) &&
            !supportsERC165InterfaceUnchecked(account, INTERFACE_ID_INVALID);
    }

    /**
     * @dev Returns true if `account` supports the interface defined by
     * `interfaceId`. Support for {IERC165} itself is queried automatically.
     *
     * See {IERC165-supportsInterface}.
     */
    function supportsInterface(address account, bytes4 interfaceId) internal view returns (bool) {
        // query support of both ERC-165 as per the spec and support of _interfaceId
        return supportsERC165(account) && supportsERC165InterfaceUnchecked(account, interfaceId);
    }

    /**
     * @dev Returns a boolean array where each value corresponds to the
     * interfaces passed in and whether they're supported or not. This allows
     * you to batch check interfaces for a contract where your expectation
     * is that some interfaces may not be supported.
     *
     * See {IERC165-supportsInterface}.
     */
    function getSupportedInterfaces(
        address account,
        bytes4[] memory interfaceIds
    ) internal view returns (bool[] memory) {
        // an array of booleans corresponding to interfaceIds and whether they're supported or not
        bool[] memory interfaceIdsSupported = new bool[](interfaceIds.length);

        // query support of ERC-165 itself
        if (supportsERC165(account)) {
            // query support of each interface in interfaceIds
            for (uint256 i = 0; i < interfaceIds.length; i++) {
                interfaceIdsSupported[i] = supportsERC165InterfaceUnchecked(account, interfaceIds[i]);
            }
        }

        return interfaceIdsSupported;
    }

    /**
     * @dev Returns true if `account` supports all the interfaces defined in
     * `interfaceIds`. Support for {IERC165} itself is queried automatically.
     *
     * Batch-querying can lead to gas savings by skipping repeated checks for
     * {IERC165} support.
     *
     * See {IERC165-supportsInterface}.
     */
    function supportsAllInterfaces(address account, bytes4[] memory interfaceIds) internal view returns (bool) {
        // query support of ERC-165 itself
        if (!supportsERC165(account)) {
            return false;
        }

        // query support of each interface in interfaceIds
        for (uint256 i = 0; i < interfaceIds.length; i++) {
            if (!supportsERC165InterfaceUnchecked(account, interfaceIds[i])) {
                return false;
            }
        }

        // all interfaces supported
        return true;
    }

    /**
     * @notice Query if a contract implements an interface, does not check ERC-165 support
     * @param account The address of the contract to query for support of an interface
     * @param interfaceId The interface identifier, as specified in ERC-165
     * @return true if the contract at account indicates support of the interface with
     * identifier interfaceId, false otherwise
     * @dev Assumes that account contains a contract that supports ERC-165, otherwise
     * the behavior of this method is undefined. This precondition can be checked
     * with {supportsERC165}.
     *
     * Some precompiled contracts will falsely indicate support for a given interface, so caution
     * should be exercised when using this function.
     *
     * Interface identification is specified in ERC-165.
     */
    function supportsERC165InterfaceUnchecked(address account, bytes4 interfaceId) internal view returns (bool) {
        // prepare call
        bytes memory encodedParams = abi.encodeCall(IERC165.supportsInterface, (interfaceId));

        // perform static call
        bool success;
        uint256 returnSize;
        uint256 returnValue;
        assembly ("memory-safe") {
            success := staticcall(30000, account, add(encodedParams, 0x20), mload(encodedParams), 0x00, 0x20)
            returnSize := returndatasize()
            returnValue := mload(0x00)
        }

        return success && returnSize >= 0x20 && returnValue > 0;
    }
}
          

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v5.4.0) (utils/Address.sol)

pragma solidity ^0.8.20;

import {Errors} from "./Errors.sol";

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev There's no code at `target` (it is not a contract).
     */
    error AddressEmptyCode(address target);

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.8.20/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        if (address(this).balance < amount) {
            revert Errors.InsufficientBalance(address(this).balance, amount);
        }

        (bool success, bytes memory returndata) = recipient.call{value: amount}("");
        if (!success) {
            _revert(returndata);
        }
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason or custom error, it is bubbled
     * up by this function (like regular Solidity function calls). However, if
     * the call reverted with no returned reason, this function reverts with a
     * {Errors.FailedCall} error.
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     */
    function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {
        if (address(this).balance < value) {
            revert Errors.InsufficientBalance(address(this).balance, value);
        }
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, success, returndata);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, success, returndata);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and reverts if the target
     * was not a contract or bubbling up the revert reason (falling back to {Errors.FailedCall}) in case
     * of an unsuccessful call.
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata
    ) internal view returns (bytes memory) {
        if (!success) {
            _revert(returndata);
        } else {
            // only check if target is a contract if the call was successful and the return data is empty
            // otherwise we already know that it was a contract
            if (returndata.length == 0 && target.code.length == 0) {
                revert AddressEmptyCode(target);
            }
            return returndata;
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and reverts if it wasn't, either by bubbling the
     * revert reason or with a default {Errors.FailedCall} error.
     */
    function verifyCallResult(bool success, bytes memory returndata) internal pure returns (bytes memory) {
        if (!success) {
            _revert(returndata);
        } else {
            return returndata;
        }
    }

    /**
     * @dev Reverts with returndata if present. Otherwise reverts with {Errors.FailedCall}.
     */
    function _revert(bytes memory returndata) private pure {
        // Look for revert reason and bubble it up if present
        if (returndata.length > 0) {
            // The easiest way to bubble the revert reason is using memory via assembly
            assembly ("memory-safe") {
                revert(add(returndata, 0x20), mload(returndata))
            }
        } else {
            revert Errors.FailedCall();
        }
    }
}