Contract 0xd6536f9cc2fe9c5bf153ef8e294be3d2a739216a

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "./StanToken.sol";
import "./StanNFT.sol";
import "./CollectionNFT.sol";

contract Aution is Ownable {
    using Counters for Counters.Counter;
    Counters.Counter private _tokenIds;

    mapping(address => uint256) public balanceOfFan;
    mapping(string => autionStruct) public autionIdToAution;
    mapping(string => address[]) public autionIdToParticipants;
    address public tokenStanAddress;
    address public stanWalletAddress;

    StanToken public tokenStan;
    StanNFT public stanNFT;
    CollectionNFT private collectionNFT;

    struct autionStruct {
        string autionId;
        uint160 nftId;
        StateOfAution state;
        address owner;
        address winner;
        mapping(address => uint256) userToBidnumber;
    }

    enum Method {
        BUY,
        AUTION
    }

    enum StateOfAution {
        ACTIVE,
        DONE,
        CANCEL,
        EXPIRED
    }

    event Winner(
        address _winner,
        uint256 _tokenId,
        address _artist,
        uint256 _bidNumber
    );

    event Purchase(
        address _buyer,
        address _seller,
        uint160 _tokenId,
        uint256 _price
    );

    event CreateAution(
        string _autionId,
        uint160 _nftId,
        StateOfAution _state,
        address _owner
    );

    event MakeOffer(
        address _sender,
        uint256 _bidnumerInAution,
        uint256 _balanceFundOfUser,
        string _autionId,
        uint160 _tokenId
    );

    event CancelOffer(
        string _autionId,
        uint256 _feeCharged,
        uint256 _balanceOfuser
    );

    event TransferNFT(
        address _from,
        address _to,
        string _idCollection,
        uint160 _tokenIDs
    );

    event Buy(address _buyer, uint160 _tokenId, uint256 _tokenIdToPrice);
    event SetStateAution(string _autionId, StateOfAution _state);
    event CancelListing(string _autionId, StateOfAution _state);
    event BackFeeToFund(bool _cancelListing, string _autionId);
    event Withdraw(uint256 _amount, address _user, uint256 _balanceOfuser);
    event Deposit(uint256 _balanceOfUser, address _user);

    constructor(
        address _tokenStan,
        address _stanNFT,
        address _collectionNFT,
        address _stanWalletAddress
    ) {
        tokenStan = StanToken(_tokenStan);
        stanNFT = StanNFT(_stanNFT);
        collectionNFT = CollectionNFT(_collectionNFT);
        stanWalletAddress = _stanWalletAddress;
    }

    modifier checkNFTOwnerShip(uint160 _tokenId) {
        stanNFT.isApprovedOrOwner(_tokenId);
        _;
    }

    modifier checkValidAmout(uint256 _amount) {
        require(_amount > 0, "Invalid amount");
        _;
    }

    modifier checkStateOfAution(string memory _autionId) {
        require(
            autionIdToAution[_autionId].state == StateOfAution.ACTIVE,
            "Invalid aution state"
        );
        _;
    }

    function Decimals() public pure returns (uint256) {
        return uint256(10**18);
    }

    function setTokenStan(address _tokenStan) external onlyOwner {
        tokenStan = StanToken(_tokenStan);
    }

    function setStateAution(string memory _autionId, StateOfAution _state)
        external
        onlyOwner
    {
        require(
            autionIdToAution[_autionId].state != StateOfAution.DONE,
            "Cannot change the aution in the past"
        );
        autionIdToAution[_autionId].state = _state;

        emit SetStateAution(_autionId, _state);
    }

    function setStanNFT(address _stanNFT) external onlyOwner {
        stanNFT = StanNFT(_stanNFT);
    }

    function setStanAddress(address _stanAddress) external onlyOwner {
        stanWalletAddress = _stanAddress;
    }

    function setCollectionNFTAddress(address _collectionNFTAddress)
        external
        onlyOwner
    {
        collectionNFT = CollectionNFT(_collectionNFTAddress);
    }

    // Stan transfer fee to receivers
    function purchaseProcessing(
        string memory _idCollection,
        address _from,
        uint256 _amount,
        uint160 _tokenId
    ) internal {
        (
            ,
            uint256 ratioCreator,
            uint256 ratioStan,
            address creator,
            ,

        ) = collectionNFT.getInfoCollection(_idCollection, _tokenId, _from);

        uint256 creatorAmount = (_amount * ratioCreator) / 100;
        uint256 creatorStan = (_amount * ratioStan) / 100;
        require(
            _amount - creatorAmount - creatorStan > 0,
            "The amount is not enough for the fee being charged"
        );
        uint256 remainAmount = _amount - creatorAmount - creatorStan;

        tokenStan.purchase(address(this), creator, creatorAmount);
        tokenStan.purchase(address(this), stanWalletAddress, creatorStan);
        tokenStan.purchase(address(this), _from, remainAmount);
    }

    function purchase(
        address _buyer,
        address _seller,
        uint256 _amount,
        uint160 _tokenId,
        uint256 _feePurchase,
        string memory _idCollection
    ) external onlyOwner checkNFTOwnerShip(_tokenId) checkValidAmout(_amount) {
        require(
            tokenStan.transferFrom(_buyer, address(this), _amount),
            "Not enough money to proceed"
        );

        uint256 feePurchase = (_amount * _feePurchase) / 100;
        uint256 amountAfterCharged = _amount - feePurchase;
        stanNFT.transfer(_idCollection, address(stanNFT), _buyer, _tokenId);
        purchaseProcessing(
            _idCollection,
            _seller,
            amountAfterCharged,
            _tokenId
        );

        emit Purchase(
            _buyer,
            _seller,
            _tokenId,
            stanNFT.TokenIdToPrice(_tokenId)
        );
    }

    function createAution(
        address _owner,
        string memory _autionId,
        uint160 _nftId
    ) external onlyOwner {
        autionIdToAution[_autionId].autionId = _autionId;
        autionIdToAution[_autionId].nftId = _nftId;
        autionIdToAution[_autionId].state = StateOfAution.ACTIVE;
        autionIdToAution[_autionId].owner = _owner;

        emit CreateAution(_autionId, _nftId, StateOfAution.ACTIVE, _owner);
    }

    function makeOffer(
        address _user,
        string memory _autionId,
        uint256 _bidNumber
    ) external onlyOwner checkStateOfAution(_autionId) {
        require(_bidNumber > 0, "Invalid bid number");
        require(
            balanceOfFan[_user] >=
                _bidNumber - autionIdToAution[_autionId].userToBidnumber[_user],
            "Not enough balance to aution, please deposit more"
        );

        uint256 _balanceUserAution = autionIdToAution[_autionId]
            .userToBidnumber[_user];
        uint256 finalBidNumber = _bidNumber - _balanceUserAution;
        autionIdToParticipants[_autionId].push(_user);
        balanceOfFan[_user] -= finalBidNumber;
        autionIdToAution[_autionId].userToBidnumber[_user] += finalBidNumber;

        emit MakeOffer(
            _user,
            autionIdToAution[_autionId].userToBidnumber[_user],
            balanceOfFan[_user],
            _autionId,
            autionIdToAution[_autionId].nftId
        );
    }

    function getWinner(
        address _winner,
        address _artist,
        uint256 _bidNumber,
        string memory _autionId,
        string memory _idCollection
    )
        external
        onlyOwner
        checkNFTOwnerShip(autionIdToAution[_autionId].nftId)
        checkStateOfAution(_autionId)
    {
        require(
            autionIdToAution[_autionId].userToBidnumber[_winner] > 0 &&
                autionIdToAution[_autionId].userToBidnumber[_winner] >=
                _bidNumber,
            "Invalid winner"
        );

        autionIdToAution[_autionId].state = StateOfAution.DONE;
        backFeeToFund(false, _autionId);
        uint160 tokenId = autionIdToAution[_autionId].nftId;
        stanNFT.transfer(_idCollection, address(stanNFT), _winner, tokenId);
        purchaseProcessing(_idCollection, _artist, _bidNumber, tokenId);

        emit Winner(_winner, tokenId, _artist, _bidNumber);
    }

    function backFeeToFund(bool _cancelListing, string memory _autionId)
        internal
    {
        uint256 length = autionIdToParticipants[_autionId].length;
        if (_cancelListing) {
            for (uint256 i = 0; i < length; ) {
                address addressUser = autionIdToParticipants[_autionId][i];
                balanceOfFan[addressUser] += autionIdToAution[_autionId]
                    .userToBidnumber[addressUser];
                unchecked {
                    ++i;
                }
            }
        } else {
            for (uint256 i = 0; i < length; ) {
                address addressUser = autionIdToParticipants[_autionId][i];
                if (addressUser != autionIdToAution[_autionId].winner) {
                    balanceOfFan[addressUser] += autionIdToAution[_autionId]
                        .userToBidnumber[addressUser];
                }
                unchecked {
                    ++i;
                }
            }
        }
        emit BackFeeToFund(_cancelListing, _autionId);
    }

    function withdraw(uint256 _amount) external {
        require(
            balanceOfFan[msg.sender] > 0 && balanceOfFan[msg.sender] >= _amount,
            "The amount exceed the balance of user"
        );

        balanceOfFan[msg.sender] -= _amount;
        payable(msg.sender).transfer(_amount);

        emit Withdraw(_amount, msg.sender, balanceOfFan[msg.sender]);
    }

    function deposit(uint256 _amount) external checkValidAmout(_amount) {
        balanceOfFan[msg.sender] += _amount;
        tokenStan.purchase(msg.sender, address(this), _amount);

        emit Deposit(balanceOfFan[msg.sender], msg.sender);
    }

    function cancelOffer(
        string memory _autionId,
        uint256 _feeCharged,
        address _from
    ) external onlyOwner {
        require(
            autionIdToAution[_autionId].userToBidnumber[_from] > 0,
            "You don't take partcipate in this aution"
        );

        uint256 balanceOfUserAution = autionIdToAution[_autionId]
            .userToBidnumber[_from];
        autionIdToAution[_autionId].userToBidnumber[_from] = 0;
        uint256 feeCharged = (balanceOfUserAution * _feeCharged) / 100;
        uint256 amountAfterCharged = balanceOfUserAution - feeCharged;
        balanceOfFan[_from] += amountAfterCharged;
        tokenStan.purchase(address(this), stanWalletAddress, feeCharged);

        emit CancelOffer(_autionId, _feeCharged, balanceOfFan[_from]);
    }

    function transferPvPNFT(
        address _from,
        address _to,
        uint256 _fee,
        string memory _idCollection,
        uint160 _tokenIDs
    ) external onlyOwner {
        require(
            _from != address(0) && _to != address(0),
            "The address is invalid"
        );
        require(
            balanceOfFan[_from] >= _fee,
            "Your balance is not enough to pay the fee"
        );

        balanceOfFan[_from] -= _fee;
        stanNFT.transfer(_idCollection, _from, _to, _tokenIDs);
        tokenStan.purchase(_from, stanWalletAddress, _fee);

        emit TransferNFT(_from, _to, _idCollection, _tokenIDs);
    }

    function cancelListing(string memory _autionId, uint256 _fee)
        external
        onlyOwner
        checkStateOfAution(_autionId)
    {
        address ownerAddress = autionIdToAution[_autionId].owner;
        require(
            ownerAddress != address(0) && balanceOfFan[ownerAddress] >= _fee,
            "Owner balance is not enough to pay the fee"
        );

        autionIdToAution[_autionId].state = StateOfAution.CANCEL;
        backFeeToFund(true, _autionId);
        balanceOfFan[ownerAddress] -= _fee;
        tokenStan.purchase(ownerAddress, stanWalletAddress, _fee);

        emit CancelListing(_autionId, StateOfAution.CANCEL);
    }

    function getAutionInformation(string memory _autionId, address _user)
        public
        view
        returns (
            string memory autionId,
            uint160 nftId,
            StateOfAution state,
            address owner,
            address winner,
            uint256 autionBalance
        )
    {
        return (
            _autionId,
            autionIdToAution[_autionId].nftId,
            autionIdToAution[_autionId].state,
            autionIdToAution[_autionId].owner,
            autionIdToAution[_autionId].winner,
            autionIdToAution[_autionId].userToBidnumber[_user]
        );
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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 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);
    }
}

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

pragma solidity ^0.8.0;

/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented, decremented or reset. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 */
library Counters {
    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        unchecked {
            counter._value += 1;
        }
    }

    function decrement(Counter storage counter) internal {
        uint256 value = counter._value;
        require(value > 0, "Counter: decrement overflow");
        unchecked {
            counter._value = value - 1;
        }
    }

    function reset(Counter storage counter) internal {
        counter._value = 0;
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";

contract StanToken is ERC20, Ownable {
    constructor() ERC20("Stan", "STC") {
        _mint(msg.sender, 100000 * Decimals());
    }

    function Decimals() public pure returns (uint256) {
        return 10**18;
    }

    function purchase(
        address _from,
        address _to,
        uint256 _amount
    ) external returns (bool) {
        _transfer(_from, _to, _amount);
        return true;
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "./CollectionNFT.sol";

contract StanNFT is ERC721Enumerable, ERC721URIStorage, Ownable {
    using Counters for Counters.Counter;
    Counters.Counter private _tokenIds;
    CollectionNFT private collectionNFT;

    enum StateOfNFT {
        ACTIVE,
        DONE,
        CANCEL
    }

    mapping(uint256 => uint256) public TokenIdToPrice;
    mapping(uint256 => StateOfNFT) public TokenIdToState;

    constructor() ERC721("Stan", "STAN") {}

    function Decimals() public pure returns (uint256) {
        return uint256(10**18);
    }

    function setCollectionNFT(address _collectionNFTAdrress)
        external
        onlyOwner
    {
        collectionNFT = CollectionNFT(_collectionNFTAdrress);
    }

    function createNFT(
        string memory _idCollection,
        string memory _tokenURI,
        uint256 _price
    ) external returns (uint256) {
        uint256 newTokenId = _tokenIds.current();
        _safeMint(msg.sender, newTokenId);
        _setTokenURI(newTokenId, _tokenURI);
        TokenIdToPrice[newTokenId] = _price;
        TokenIdToState[newTokenId] = StateOfNFT.ACTIVE;
        collectionNFT.addNFTtoCollection(_idCollection, newTokenId, msg.sender);
        collectionNFT.updateOwnerNFT(_idCollection, address(0), msg.sender);
        _tokenIds.increment();
        return newTokenId;
    }

    function isApprovedOrOwner(uint160 _tokenId) external view {
        require(
            _isApprovedOrOwner(address(this), _tokenId),
            "The caller didn't transfer the NFT to StanNFT smart contract"
        );
    }

    function transfer(
        string memory _idCollection,
        address _from,
        address _to,
        uint160 _tokenId
    ) external {
        _transfer(_from, _to, _tokenId);
        collectionNFT.updateOwnerNFT(_idCollection, _from, _to);
    }

    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal override(ERC721, ERC721Enumerable) {
        super._beforeTokenTransfer(from, to, tokenId);
    }

    function _burn(uint256 tokenId)
        internal
        override(ERC721, ERC721URIStorage)
    {
        super._burn(tokenId);
    }

    function tokenURI(uint256 tokenId)
        public
        view
        override(ERC721, ERC721URIStorage)
        returns (string memory)
    {
        return super.tokenURI(tokenId);
    }

    function supportsInterface(bytes4 interfaceId)
        public
        view
        override(ERC721, ERC721Enumerable)
        returns (bool)
    {
        return super.supportsInterface(interfaceId);
    }
}

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "./StanNFT.sol";

contract CollectionNFT is Ownable {
    using Counters for Counters.Counter;
    StanNFT public stanNFT;
    Counters.Counter private _collectionIds;
    mapping(string => bool) public collectionId;

    struct stateCollection {
        string id;
        Counters.Counter currentNumber;
        uint256 maxNumber;
        uint256 ratioCreator;
        uint256 ratioStan;
        mapping(uint256 => uint256) NFT;
        mapping(address => address) currentOwnerNFT;
        mapping(uint256 => address) creator;
    }

    mapping(string => stateCollection) internal _collectionNFT;

    event SetCollection(string _collectionId, uint256 _maxColletionNumber);
    event SetRatioCollection(
        string _collectionId,
        uint256 _ratioCreator,
        uint256 _ratioStan
    );

    event AddNFTtoCollection(
        string _collectionId,
        uint256 _nftId,
        address _creator
    );

    modifier OnlyStanOrOwner() {
        require(
            owner() == _msgSender() || _msgSender() == address(stanNFT),
            "Only Owner or Stan can call this function"
        );
        _;
    }

    constructor(address _stanNFT) {
        stanNFT = StanNFT(_stanNFT);
    }

    function setStanNFT(address _stanNFT) external onlyOwner {
        stanNFT = StanNFT(_stanNFT);
    }

    function createCollection(
        string memory _collectionId,
        uint160 _maxColletionNumber,
        uint256 _ratioCreator,
        uint256 _ratioStan
    ) external {
        require(
            collectionId[_collectionId] == false,
            "This collection id has already been used"
        );
        collectionId[_collectionId] = true;
        _collectionNFT[_collectionId].id = _collectionId;
        _collectionNFT[_collectionId].maxNumber = _maxColletionNumber;
        _collectionNFT[_collectionId].currentNumber.current();
        _collectionNFT[_collectionId].ratioCreator = _ratioCreator;
        _collectionNFT[_collectionId].ratioStan = _ratioStan;
        _collectionIds.increment();

        emit SetCollection(_collectionId, _maxColletionNumber);
    }

    function setRatioCollection(
        string memory _idCollection,
        uint256 _ratioCreator,
        uint256 _ratioStan
    ) external {
        _collectionNFT[_idCollection].ratioCreator = _ratioCreator;
        _collectionNFT[_idCollection].ratioStan = _ratioStan;

        emit SetRatioCollection(_idCollection, _ratioCreator, _ratioStan);
    }

    function addNFTtoCollection(
        string memory _idCollection,
        uint256 _nftId,
        address _creator
    ) external OnlyStanOrOwner {
        require(
            _collectionNFT[_idCollection].currentNumber.current() <=
                _collectionNFT[_idCollection].maxNumber,
            "This collection has already full of NFTs"
        );

        _collectionNFT[_idCollection].NFT[_nftId] = _nftId;
        _collectionNFT[_idCollection].creator[_nftId] = _creator;
        _collectionNFT[_idCollection].currentNumber.increment();

        emit AddNFTtoCollection(_idCollection, _nftId, _creator);
    }

    function updateOwnerNFT(
        string memory _idCollection,
        address _from,
        address _to
    ) external OnlyStanOrOwner {
        delete _collectionNFT[_idCollection].currentOwnerNFT[_from];
        _collectionNFT[_idCollection].currentOwnerNFT[_to] = _to;
    }

    function getInfoCollection(
        string memory _idCollection,
        uint256 _nft,
        address _currentOwnerNFT
    )
        external
        view
        returns (
            uint256 maxNumber,
            uint256 ratioCreator,
            uint256 ratioStan,
            address creator,
            uint256 nft,
            address currentOwnerNFT
        )
    {
        return (
            _collectionNFT[_idCollection].maxNumber,
            _collectionNFT[_idCollection].ratioCreator,
            _collectionNFT[_idCollection].ratioStan,
            _collectionNFT[_idCollection].creator[_nft],
            _collectionNFT[_idCollection].NFT[_nft],
            _collectionNFT[_idCollection].currentOwnerNFT[_currentOwnerNFT]
        );
    }
}

// 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;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, _allowances[owner][spender] + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = _allowances[owner][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
        }
        _balances[to] += amount;

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        _balances[account] += amount;
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
        }
        _totalSupply -= amount;

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Spend `amount` form the allowance of `owner` toward `spender`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// 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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC721/ERC721.sol)

pragma solidity ^0.8.0;

import "./IERC721.sol";
import "./IERC721Receiver.sol";
import "./extensions/IERC721Metadata.sol";
import "../../utils/Address.sol";
import "../../utils/Context.sol";
import "../../utils/Strings.sol";
import "../../utils/introspection/ERC165.sol";

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    using Address for address;
    using Strings for uint256;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Mapping from token ID to owner address
    mapping(uint256 => address) private _owners;

    // Mapping owner address to token count
    mapping(address => uint256) private _balances;

    // Mapping from token ID to approved address
    mapping(uint256 => address) private _tokenApprovals;

    // Mapping from owner to operator approvals
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return
            interfaceId == type(IERC721).interfaceId ||
            interfaceId == type(IERC721Metadata).interfaceId ||
            super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");
        return _balances[owner];
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _owners[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");
        return owner;
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");

        string memory baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
    }

    /**
     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
     * by default, can be overriden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        _setApprovalForAll(_msgSender(), operator, approved);
    }

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _transfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) public virtual override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
        _safeTransfer(from, to, tokenId, _data);
    }

    /**
     * @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.
     *
     * `_data` is additional data, it has no specified format and it is sent in call to `to`.
     *
     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
     * implement alternative mechanisms to perform token transfer, such as signature-based.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeTransfer(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns whether `tokenId` exists.
     *
     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
     *
     * Tokens start existing when they are minted (`_mint`),
     * and stop existing when they are burned (`_burn`).
     */
    function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _owners[tokenId] != address(0);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        require(_exists(tokenId), "ERC721: operator query for nonexistent token");
        address owner = ERC721.ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
     */
    function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Transfer} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _beforeTokenTransfer(address(0), to, tokenId);

        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(address(0), to, tokenId);

        _afterTokenTransfer(address(0), to, tokenId);
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId);

        _beforeTokenTransfer(owner, address(0), tokenId);

        // Clear approvals
        _approve(address(0), tokenId);

        _balances[owner] -= 1;
        delete _owners[tokenId];

        emit Transfer(owner, address(0), tokenId);

        _afterTokenTransfer(owner, address(0), tokenId);
    }

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer from incorrect owner");
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId);

        // Clear approvals from the previous owner
        _approve(address(0), tokenId);

        _balances[from] -= 1;
        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(from, to, tokenId);

        _afterTokenTransfer(from, to, tokenId);
    }

    /**
     * @dev Approve `to` to operate on `tokenId`
     *
     * Emits a {Approval} event.
     */
    function _approve(address to, uint256 tokenId) internal virtual {
        _tokenApprovals[tokenId] = to;
        emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
    }

    /**
     * @dev Approve `operator` to operate on all of `owner` tokens
     *
     * Emits a {ApprovalForAll} event.
     */
    function _setApprovalForAll(
        address owner,
        address operator,
        bool approved
    ) internal virtual {
        require(owner != operator, "ERC721: approve to caller");
        _operatorApprovals[owner][operator] = approved;
        emit ApprovalForAll(owner, operator, approved);
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) private returns (bool) {
        if (to.isContract()) {
            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data) returns (bytes4 retval) {
                return retval == IERC721Receiver.onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert("ERC721: transfer to non ERC721Receiver implementer");
                } else {
                    assembly {
                        revert(add(32, reason), mload(reason))
                    }
                }
            }
        } else {
            return true;
        }
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/ERC721URIStorage.sol)

pragma solidity ^0.8.0;

import "../ERC721.sol";

/**
 * @dev ERC721 token with storage based token URI management.
 */
abstract contract ERC721URIStorage is ERC721 {
    using Strings for uint256;

    // Optional mapping for token URIs
    mapping(uint256 => string) private _tokenURIs;

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721URIStorage: URI query for nonexistent token");

        string memory _tokenURI = _tokenURIs[tokenId];
        string memory base = _baseURI();

        // If there is no base URI, return the token URI.
        if (bytes(base).length == 0) {
            return _tokenURI;
        }
        // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
        if (bytes(_tokenURI).length > 0) {
            return string(abi.encodePacked(base, _tokenURI));
        }

        return super.tokenURI(tokenId);
    }

    /**
     * @dev Sets `_tokenURI` as the tokenURI of `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
        require(_exists(tokenId), "ERC721URIStorage: URI set of nonexistent token");
        _tokenURIs[tokenId] = _tokenURI;
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual override {
        super._burn(tokenId);

        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/ERC721Enumerable.sol)

pragma solidity ^0.8.0;

import "../ERC721.sol";
import "./IERC721Enumerable.sol";

/**
 * @dev This implements an optional extension of {ERC721} defined in the EIP that adds
 * enumerability of all the token ids in the contract as well as all token ids owned by each
 * account.
 */
abstract contract ERC721Enumerable is ERC721, IERC721Enumerable {
    // Mapping from owner to list of owned token IDs
    mapping(address => mapping(uint256 => uint256)) private _ownedTokens;

    // Mapping from token ID to index of the owner tokens list
    mapping(uint256 => uint256) private _ownedTokensIndex;

    // Array with all token ids, used for enumeration
    uint256[] private _allTokens;

    // Mapping from token id to position in the allTokens array
    mapping(uint256 => uint256) private _allTokensIndex;

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC721) returns (bool) {
        return interfaceId == type(IERC721Enumerable).interfaceId || super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {
        require(index < ERC721.balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
        return _ownedTokens[owner][index];
    }

    /**
     * @dev See {IERC721Enumerable-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _allTokens.length;
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index) public view virtual override returns (uint256) {
        require(index < ERC721Enumerable.totalSupply(), "ERC721Enumerable: global index out of bounds");
        return _allTokens[index];
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual override {
        super._beforeTokenTransfer(from, to, tokenId);

        if (from == address(0)) {
            _addTokenToAllTokensEnumeration(tokenId);
        } else if (from != to) {
            _removeTokenFromOwnerEnumeration(from, tokenId);
        }
        if (to == address(0)) {
            _removeTokenFromAllTokensEnumeration(tokenId);
        } else if (to != from) {
            _addTokenToOwnerEnumeration(to, tokenId);
        }
    }

    /**
     * @dev Private function to add a token to this extension's ownership-tracking data structures.
     * @param to address representing the new owner of the given token ID
     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
     */
    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
        uint256 length = ERC721.balanceOf(to);
        _ownedTokens[to][length] = tokenId;
        _ownedTokensIndex[tokenId] = length;
    }

    /**
     * @dev Private function to add a token to this extension's token tracking data structures.
     * @param tokenId uint256 ID of the token to be added to the tokens list
     */
    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
        _allTokensIndex[tokenId] = _allTokens.length;
        _allTokens.push(tokenId);
    }

    /**
     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
     * @param from address representing the previous owner of the given token ID
     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
     */
    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = ERC721.balanceOf(from) - 1;
        uint256 tokenIndex = _ownedTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary
        if (tokenIndex != lastTokenIndex) {
            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];

            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
        }

        // This also deletes the contents at the last position of the array
        delete _ownedTokensIndex[tokenId];
        delete _ownedTokens[from][lastTokenIndex];
    }

    /**
     * @dev Private function to remove a token from this extension's token tracking data structures.
     * This has O(1) time complexity, but alters the order of the _allTokens array.
     * @param tokenId uint256 ID of the token to be removed from the tokens list
     */
    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _allTokens.length - 1;
        uint256 tokenIndex = _allTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
        uint256 lastTokenId = _allTokens[lastTokenIndex];

        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

        // This also deletes the contents at the last position of the array
        delete _allTokensIndex[tokenId];
        _allTokens.pop();
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (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`, 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 be 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: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * 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 Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @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 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);

    /**
     * @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;
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721Receiver.sol)

pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {
    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the token collection symbol.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @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://diligence.consensys.net/posts/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/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @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, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * 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.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @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`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // 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 {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

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

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

// 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);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC721/extensions/IERC721Enumerable.sol)

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

{
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "outputSelection": {
    "*": {
      "*": [
        "evm.bytecode",
        "evm.deployedBytecode",
        "devdoc",
        "userdoc",
        "metadata",
        "abi"
      ]
    }
  },
  "libraries": {}
}

[{"inputs":[{"internalType":"address","name":"_tokenStan","type":"address"},{"internalType":"address","name":"_stanNFT","type":"address"},{"internalType":"address","name":"_collectionNFT","type":"address"},{"internalType":"address","name":"_stanWalletAddress","type":"address"}],"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"bool","name":"_cancelListing","type":"bool"},{"indexed":false,"internalType":"string","name":"_autionId","type":"string"}],"name":"BackFeeToFund","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"_buyer","type":"address"},{"indexed":false,"internalType":"uint160","name":"_tokenId","type":"uint160"},{"indexed":false,"internalType":"uint256","name":"_tokenIdToPrice","type":"uint256"}],"name":"Buy","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"string","name":"_autionId","type":"string"},{"indexed":false,"internalType":"enum Aution.StateOfAution","name":"_state","type":"uint8"}],"name":"CancelListing","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"string","name":"_autionId","type":"string"},{"indexed":false,"internalType":"uint256","name":"_feeCharged","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"_balanceOfuser","type":"uint256"}],"name":"CancelOffer","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"string","name":"_autionId","type":"string"},{"indexed":false,"internalType":"uint160","name":"_nftId","type":"uint160"},{"indexed":false,"internalType":"enum Aution.StateOfAution","name":"_state","type":"uint8"},{"indexed":false,"internalType":"address","name":"_owner","type":"address"}],"name":"CreateAution","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"uint256","name":"_balanceOfUser","type":"uint256"},{"indexed":false,"internalType":"address","name":"_user","type":"address"}],"name":"Deposit","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"_sender","type":"address"},{"indexed":false,"internalType":"uint256","name":"_bidnumerInAution","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"_balanceFundOfUser","type":"uint256"},{"indexed":false,"internalType":"string","name":"_autionId","type":"string"},{"indexed":false,"internalType":"uint160","name":"_tokenId","type":"uint160"}],"name":"MakeOffer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"previousOwner","type":"address"},{"indexed":true,"internalType":"address","name":"newOwner","type":"address"}],"name":"OwnershipTransferred","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"_buyer","type":"address"},{"indexed":false,"internalType":"address","name":"_seller","type":"address"},{"indexed":false,"internalType":"uint160","name":"_tokenId","type":"uint160"},{"indexed":false,"internalType":"uint256","name":"_price","type":"uint256"}],"name":"Purchase","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"string","name":"_autionId","type":"string"},{"indexed":false,"internalType":"enum Aution.StateOfAution","name":"_state","type":"uint8"}],"name":"SetStateAution","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"_from","type":"address"},{"indexed":false,"internalType":"address","name":"_to","type":"address"},{"indexed":false,"internalType":"string","name":"_idCollection","type":"string"},{"indexed":false,"internalType":"uint160","name":"_tokenIDs","type":"uint160"}],"name":"TransferNFT","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"_winner","type":"address"},{"indexed":false,"internalType":"uint256","name":"_tokenId","type":"uint256"},{"indexed":false,"internalType":"address","name":"_artist","type":"address"},{"indexed":false,"internalType":"uint256","name":"_bidNumber","type":"uint256"}],"name":"Winner","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"uint256","name":"_amount","type":"uint256"},{"indexed":false,"internalType":"address","name":"_user","type":"address"},{"indexed":false,"internalType":"uint256","name":"_balanceOfuser","type":"uint256"}],"name":"Withdraw","type":"event"},{"inputs":[],"name":"Decimals","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"pure","type":"function"},{"inputs":[{"internalType":"string","name":"","type":"string"}],"name":"autionIdToAution","outputs":[{"internalType":"string","name":"autionId","type":"string"},{"internalType":"uint160","name":"nftId","type":"uint160"},{"internalType":"enum Aution.StateOfAution","name":"state","type":"uint8"},{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"winner","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"string","name":"","type":"string"},{"internalType":"uint256","name":"","type":"uint256"}],"name":"autionIdToParticipants","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"","type":"address"}],"name":"balanceOfFan","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"string","name":"_autionId","type":"string"},{"internalType":"uint256","name":"_fee","type":"uint256"}],"name":"cancelListing","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"string","name":"_autionId","type":"string"},{"internalType":"uint256","name":"_feeCharged","type":"uint256"},{"internalType":"address","name":"_from","type":"address"}],"name":"cancelOffer","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"_owner","type":"address"},{"internalType":"string","name":"_autionId","type":"string"},{"internalType":"uint160","name":"_nftId","type":"uint160"}],"name":"createAution","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"_amount","type":"uint256"}],"name":"deposit","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"string","name":"_autionId","type":"string"},{"internalType":"address","name":"_user","type":"address"}],"name":"getAutionInformation","outputs":[{"internalType":"string","name":"autionId","type":"string"},{"internalType":"uint160","name":"nftId","type":"uint160"},{"internalType":"enum Aution.StateOfAution","name":"state","type":"uint8"},{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"winner","type":"address"},{"internalType":"uint256","name":"autionBalance","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"_winner","type":"address"},{"internalType":"address","name":"_artist","type":"address"},{"internalType":"uint256","name":"_bidNumber","type":"uint256"},{"internalType":"string","name":"_autionId","type":"string"},{"internalType":"string","name":"_idCollection","type":"string"}],"name":"getWinner","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"_user","type":"address"},{"internalType":"string","name":"_autionId","type":"string"},{"internalType":"uint256","name":"_bidNumber","type":"uint256"}],"name":"makeOffer","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"owner","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"_buyer","type":"address"},{"internalType":"address","name":"_seller","type":"address"},{"internalType":"uint256","name":"_amount","type":"uint256"},{"internalType":"uint160","name":"_tokenId","type":"uint160"},{"internalType":"uint256","name":"_feePurchase","type":"uint256"},{"internalType":"string","name":"_idCollection","type":"string"}],"name":"purchase","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"renounceOwnership","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"_collectionNFTAddress","type":"address"}],"name":"setCollectionNFTAddress","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"_stanAddress","type":"address"}],"name":"setStanAddress","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"_stanNFT","type":"address"}],"name":"setStanNFT","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"string","name":"_autionId","type":"string"},{"internalType":"enum Aution.StateOfAution","name":"_state","type":"uint8"}],"name":"setStateAution","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"_tokenStan","type":"address"}],"name":"setTokenStan","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"stanNFT","outputs":[{"internalType":"contract StanNFT","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"stanWalletAddress","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"tokenStan","outputs":[{"internalType":"contract StanToken","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"tokenStanAddress","outputs":[{"internalType":"address","name":"","type":"address"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"_from","type":"address"},{"internalType":"address","name":"_to","type":"address"},{"internalType":"uint256","name":"_fee","type":"uint256"},{"internalType":"string","name":"_idCollection","type":"string"},{"internalType":"uint160","name":"_tokenIDs","type":"uint160"}],"name":"transferPvPNFT","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"uint256","name":"_amount","type":"uint256"}],"name":"withdraw","outputs":[],"stateMutability":"nonpayable","type":"function"}]

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00000000000000000000000009056a9dd7f50e544701015822e24fd27597247d000000000000000000000000988b2c1a5495c18aedd86c0f98a0699c666803b1000000000000000000000000d1e283f88bc1c2511463c85017c481f574bf8848000000000000000000000000d3f48a6f420904829bb82815a0d78ace694265b5

-----Decoded View---------------
Arg [0] : _tokenStan (address): 0x09056a9dd7f50e544701015822e24fd27597247d
Arg [1] : _stanNFT (address): 0x988b2c1a5495c18aedd86c0f98a0699c666803b1
Arg [2] : _collectionNFT (address): 0xd1e283f88bc1c2511463c85017c481f574bf8848
Arg [3] : _stanWalletAddress (address): 0xd3f48a6f420904829bb82815a0d78ace694265b5

-----Encoded View---------------
4 Constructor Arguments found :
Arg [0] : 00000000000000000000000009056a9dd7f50e544701015822e24fd27597247d
Arg [1] : 000000000000000000000000988b2c1a5495c18aedd86c0f98a0699c666803b1
Arg [2] : 000000000000000000000000d1e283f88bc1c2511463c85017c481f574bf8848
Arg [3] : 000000000000000000000000d3f48a6f420904829bb82815a0d78ace694265b5