// File: Address.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @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
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 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");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (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");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private 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

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}
// File: Context.sol



// SPDX-License-Identifier: MIT

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) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}
// File: EnigmaV4.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./ERC721.sol";

contract EnigmaV4 is ERC721 {
    event Mint(address indexed from, uint256 indexed tokenId);

    modifier callerIsUser() {
        require(tx.origin == msg.sender, "The caller is another contract");
        _;
    }

    modifier onlyCollaborator() {
        bool isCollaborator = false;
        for (uint256 i; i < collaborators.length; i++) {
            if (collaborators[i].addr == msg.sender) {
                isCollaborator = true;

                break;
            }
        }

        require(
            owner() == _msgSender() || isCollaborator,
            "Ownable: caller is not the owner nor a collaborator"
        );

        _;
    }

    modifier claimStarted() {
        require(
            startPublicClaimDate != 0 && startPublicClaimDate <= block.timestamp,
            "Public sale is not open"
        );

        _;
    }

    modifier holderPresaleStarted() {
        require(
            startHolderPresaleDate != 0 && startHolderPresaleDate <= block.timestamp,
            "Holder presale is not open"
        );

        _;
    }

    modifier partnerPresaleStarted() {
        require(
            startPartnerPresaleDate != 0 && startPartnerPresaleDate <= block.timestamp,
            "Partner presale is not open"
        );

        _;
    }

    modifier onlyHolderWhitelisted() {
        require(holderPresaleWhitelistedAddresses[msg.sender] > 0, "You are either not whitelisted for holder presale or have claimed all tokens");

        _;
    }

    modifier onlyPartnerWhitelisted() {
        require(partnerPresaleWhitelistedAddresses[msg.sender] > 0, "You are either not whitelisted for partner presale or have claimed all tokens");

        _;
    }

    struct Collaborators {
        address addr;
        uint256 cut;
    }

    struct Whitelist {
        address addr;
        uint256 count;
    }

    uint256 private startPartnerPresaleDate = 1649077140;
    uint256 private startPublicClaimDate = 1649206740;
    uint256 private startHolderPresaleDate = 1648990740;

    uint256 private tier1Price = 150000000000000000;
    uint256 private tier2Price = 145000000000000000;
    uint256 private tier3Price = 140000000000000000;
    uint256 private tier4Price = 135000000000000000;
    uint256 private tier5Price = 130000000000000000;

    uint256 private tier1Count = 1;
    uint256 private tier2Count = 3;
    uint256 private tier3Count = 5;
    uint256 private tier4Count = 10;
    uint256 private tier5Count = 20;

    uint256 public partnerPresaleMintedTokens = 0;
    uint256 public holderPresaleMintedTokens = 0;
    uint256 public totalMintedTokens = 0;

    uint128 private basisPoints = 10000;

    uint256 private maxTokensPerTransaction = 50;
    
    string private baseURI = "";
    
    uint256 public giveawayCount = 0;

    mapping(address => uint256) private claimedEnigmaV4TokenPerWallet;

    uint16[] availableEnigmaV4Tokens;
    Collaborators[] private collaborators;

    mapping (address => uint256) holderPresaleWhitelistedAddresses;
    mapping (address => uint256) partnerPresaleWhitelistedAddresses;

    constructor() ERC721("TheEnigmaEconomyV4", "ENGv4") {}

    // ONLY OWNER

    /**
     * Sets the collaborators of the project with their cuts
     */
    function addCollaborators(Collaborators[] memory _collaborators)
        external
        onlyOwner
    {
        require(collaborators.length == 0, "Collaborators were already set");

        uint128 totalCut;
        for (uint256 i; i < _collaborators.length; i++) {
            collaborators.push(_collaborators[i]);
            totalCut += uint128(_collaborators[i].cut);
        }

        require(totalCut == basisPoints, "Total cut does not add to 100%");
    }

    function getMintPricePerToken(uint256 quantity) internal view returns (uint256) {
        uint256 mintPricePerToken = tier1Price;
        if (quantity >= tier2Count) {
            mintPricePerToken = tier2Price;
        }
        if (quantity >= tier3Count) {
            mintPricePerToken = tier3Price;
        }
        if (quantity >= tier4Count) {
            mintPricePerToken = tier4Price;
        }
        if (quantity >= tier5Count) {
            mintPricePerToken = tier5Price;
        }
        return mintPricePerToken;
    }

    // ONLY COLLABORATORS

    /**
     * @dev Allows to withdraw the Ether in the contract and split it among the collaborators
     */
    function withdraw() external onlyCollaborator {
        uint256 totalBalance = address(this).balance;

        for (uint256 i; i < collaborators.length; i++) {
            payable(collaborators[i].addr).transfer(
                mulScale(totalBalance, collaborators[i].cut, basisPoints)
            );
        }
    }

    /**
     * @dev Sets the base URI for the API that provides the NFT data.
     */
    function setBaseTokenURI(string memory _uri) external onlyCollaborator {
        baseURI = _uri;
    }

     /**
     * @dev Sets the date that users can start claiming enigmaV4 tokens
     */
    function setStartPublicClaimDate(uint256 _startPublicClaimDate)
        external
        onlyCollaborator
    {
        startPublicClaimDate = _startPublicClaimDate;
    }

    /**
     * @dev Sets the date that users can start claiming enigmaV4 tokens for holder presale
     */
    function setHolderPresaleStartDate(uint256 _startHolderPresaleDate)
        external
        onlyCollaborator
    {
        startHolderPresaleDate = _startHolderPresaleDate;
    }

    /**
     * @dev Sets the date that users can start claiming enigmaV4 tokens for partner sale
     */
    function setPartnerPresaleStartDate(uint256 _startPartnerPresaleDate)
        external
        onlyCollaborator
    {
        startPartnerPresaleDate = _startPartnerPresaleDate;
    }

    /**
     * @dev Sets the giveaway count 
     */
    function setGiveawayCount(uint256 _giveawayCount)
        external
        onlyCollaborator
    {
        giveawayCount = _giveawayCount;
    }


    /**
     * @dev Populates the available enigmaV4 tokens
     */
    function addAvailableEnigmaV4Tokens(uint16 from, uint16 to)
        external
        onlyCollaborator
    {
        for (uint16 i = from; i <= to; i++) {
            availableEnigmaV4Tokens.push(i);
        }
    }

    /**
     * @dev Removes a chosen enigmaV4 token from the available list, only a utility function
     */
    function removeEnigmaV4TokenFromAvailableEnigmaV4Tokens(uint16 tokenId)
        external
        onlyCollaborator
    {
        for (uint16 i; i <= availableEnigmaV4Tokens.length; i++) {
            if (availableEnigmaV4Tokens[i] != tokenId) {
                continue;
            }

            availableEnigmaV4Tokens[i] = availableEnigmaV4Tokens[availableEnigmaV4Tokens.length - 1];
            availableEnigmaV4Tokens.pop();

            break;
        }
    }

    /**
     * @dev Checks if a enigmaV4 token is in the available list
     */
    function isEnigmaV4TokenAvailable(uint16 tokenId)
        external
        view
        onlyCollaborator
        returns (bool)
    {
        for (uint16 i; i < availableEnigmaV4Tokens.length; i++) {
            if (availableEnigmaV4Tokens[i] == tokenId) {
                return true;
            }
        }

        return false;
    }


    /**
     * @dev Give random giveaway enigmaV4 tokens to the provided address
     */
    function reserveGiveawayEnigmaV4Tokens(address _address)
        external
        onlyCollaborator
    {
        require(availableEnigmaV4Tokens.length >= giveawayCount, "No enigmaV4 tokens left to be claimed");
        
        totalMintedTokens += giveawayCount;

        uint256[] memory tokenIds = new uint256[](giveawayCount);

        for (uint256 i; i < giveawayCount; i++) {
            tokenIds[i] = getEnigmaV4TokenToBeClaimed();
        }

        _batchMint(_address, tokenIds);
        giveawayCount = 0;
    }

    /**
    * @dev Whitelist addresses for holder presale
     */
    function whitelistAddressForHolderPresale (Whitelist[] memory users) external onlyCollaborator {
        for (uint i = 0; i < users.length; i++) {
            holderPresaleWhitelistedAddresses[users[i].addr] = users[i].count;
        }
    }

    /**
    * @dev Whitelist addresses for partner sale
     */
    function whitelistAddressForPartnerPresale (Whitelist[] memory users) external onlyCollaborator {
        for (uint i = 0; i < users.length; i++) {
            partnerPresaleWhitelistedAddresses[users[i].addr] = users[i].count;
        }
    }

    /**
    * @dev Sets max tokens per transaction
     */
    function setMaxTokensPerTransaction(uint256 _maxTokensPerTransaction)
        external
        onlyCollaborator
    {
        maxTokensPerTransaction = _maxTokensPerTransaction;
    }

    function setTier1Price(uint256 newPrice) external onlyCollaborator {
        tier1Price = newPrice;
    }

    function setTier2Price(uint256 newPrice) external onlyCollaborator {
        tier2Price = newPrice;
    }

    function setTier3Price(uint256 newPrice) external onlyCollaborator {
        tier3Price = newPrice;
    }

    function setTier4Price(uint256 newPrice) external onlyCollaborator {
        tier4Price = newPrice;
    }

    function setTier5Price(uint256 newPrice) external onlyCollaborator {
        tier5Price = newPrice;
    }

    function setTier1Count(uint256 newCount) external onlyCollaborator {
        tier1Count = newCount;
    }

    function setTier2Count(uint256 newCount) external onlyCollaborator {
        tier2Count = newCount;
    }

    function setTier3Count(uint256 newCount) external onlyCollaborator {
        tier3Count = newCount;
    }

    function setTier4Count(uint256 newCount) external onlyCollaborator {
        tier4Count = newCount;
    }

    function setTier5Count(uint256 newCount) external onlyCollaborator {
        tier5Count = newCount;
    }

    // END ONLY COLLABORATORS

    /**
     * @dev Claim upto 50 enigmaV4 tokens in public sale
     */
    function claimEnigmaV4Tokens(uint256 quantity)
        external
        payable
        callerIsUser
        claimStarted
        returns (uint256[] memory)
    {
        require(
            msg.value >= getMintPricePerToken(quantity) * quantity,
            "Not enough Ether to claim the EnigmaV4Tokens"
        );
        require(quantity <= maxTokensPerTransaction, "Max tokens per transaction can be 50");
        require(availableEnigmaV4Tokens.length >= quantity, "Not enough enigmaV4 tokens left");

        uint256[] memory tokenIds = new uint256[](quantity);

        claimedEnigmaV4TokenPerWallet[msg.sender] += quantity;
        totalMintedTokens += quantity;

        for (uint256 i; i < quantity; i++) {
            tokenIds[i] = getEnigmaV4TokenToBeClaimed();
        }

        _batchMint(msg.sender, tokenIds);
        return tokenIds;
    }

    /**
     * @dev Claim up to 50 enigmaV4 tokens at once in holder presale
     */
    function holderPresaleMintEnigmaV4Tokens(uint256 quantity)
        external
        payable
        callerIsUser
        holderPresaleStarted
        onlyHolderWhitelisted
        returns (uint256[] memory)
    {
        require(
            msg.value >= getMintPricePerToken(quantity) * quantity,
            "Not enough Ether to claim the EnigmaV4Tokens"
        );
        
        require(availableEnigmaV4Tokens.length >= quantity, "Not enough enigmaV4 tokens left");

        require(quantity <= maxTokensPerTransaction, "Max tokens per transaction can be 50");
        
        require(quantity <= holderPresaleWhitelistedAddresses[msg.sender], "Token count exceeds remaining whitelisted count for you");

        uint256[] memory tokenIds = new uint256[](quantity);

        claimedEnigmaV4TokenPerWallet[msg.sender] += quantity;
        totalMintedTokens += quantity;
        holderPresaleMintedTokens += quantity;

        for (uint256 i; i < quantity; i++) {
            tokenIds[i] = getEnigmaV4TokenToBeClaimed();
        }

        _batchMint(msg.sender, tokenIds);
        holderPresaleWhitelistedAddresses[msg.sender] = holderPresaleWhitelistedAddresses[msg.sender] - quantity;
        return tokenIds;
    }

    /**
     * @dev Claim up to 50 enigmaV4 tokens at once in partner sale
     */
    function partnerPresaleMintEnigmaV4Tokens(uint256 quantity)
        external
        payable
        callerIsUser
        partnerPresaleStarted
        onlyPartnerWhitelisted
        returns (uint256[] memory)
    {
        require(
            msg.value >= getMintPricePerToken(quantity) * quantity,
            "Not enough Ether to claim the EnigmaV4Tokens"
        );
        
        require(availableEnigmaV4Tokens.length >= quantity, "Not enough enigmaV4 tokens left");

        require(quantity <= maxTokensPerTransaction, "Max tokens per transaction can be 50");

        require(quantity <= partnerPresaleWhitelistedAddresses[msg.sender], "Token count exceeds remaining whitelisted count for you");

        uint256[] memory tokenIds = new uint256[](quantity);

        claimedEnigmaV4TokenPerWallet[msg.sender] += quantity;
        totalMintedTokens += quantity;
        partnerPresaleMintedTokens += quantity;

        for (uint256 i; i < quantity; i++) {
            tokenIds[i] = getEnigmaV4TokenToBeClaimed();
        }

        _batchMint(msg.sender, tokenIds);
        partnerPresaleWhitelistedAddresses[msg.sender] = partnerPresaleWhitelistedAddresses[msg.sender] - quantity;
        return tokenIds;
    }

    /**
     * @dev Returns the tokenId by index
     */
    function tokenByIndex(uint256 tokenId) external view returns (uint256) {
        require(
            _exists(tokenId),
            "ERC721: operator query for nonexistent token"
        );

        return tokenId;
    }

    /**
     * @dev Returns the base URI for the tokens API.
     */
    function baseTokenURI() external view returns (string memory) {
        return baseURI;
    }

    /**
     * @dev Returns how many EnigmaV4Tokens are still available to be claimed
     */
    function getAvailableEnigmaV4Tokens() external view returns (uint256) {
        return availableEnigmaV4Tokens.length;
    }

    /**
     * @dev Returns the whitelisted token count for an address in holder presale
     */
    function getHolderWhitelistedTokenCountForAddress(address _address) external view returns (uint256) {
        return holderPresaleWhitelistedAddresses[_address];
    }

    /**
     * @dev Returns the whitelisted token count for an address in partner presale
     */
    function getPartnerWhitelistedTokenCountForAddress(address _address) external view returns (uint256) {
        return partnerPresaleWhitelistedAddresses[_address];
    }

    /**
     * @dev Returns the total supply
     */
    function totalSupply() external view virtual returns (uint256) {
        return totalMintedTokens;
    }

    /**
     * @dev Returns the total minted tokens in presale
     */
    function totalHolderPresaleMintCount() external view virtual returns (uint256) {
        return holderPresaleMintedTokens;
    }

    function totalPartnerPresaleMintCount() external view virtual returns (uint256) {
        return partnerPresaleMintedTokens;
    }
    
    function getMintPriceForTokens(uint256 quantity) external view virtual returns (uint256) {
        return getMintPricePerToken(quantity)*quantity;
    } 
    
    function viewTier1Details() external view virtual returns (uint256, uint256) {
        return (tier1Price, tier1Count);
    }

    function viewTier2Details() external view virtual returns (uint256, uint256) {
        return (tier2Price, tier2Count);
    }

    function viewTier3Details() external view virtual returns (uint256, uint256) {
        return (tier3Price, tier3Count);
    }

    function viewTier4Details() external view virtual returns (uint256, uint256) {
        return (tier4Price, tier4Count);
    }

    function viewTier5Details() external view virtual returns (uint256, uint256) {
        return (tier5Price, tier5Count);
    }

    // Private and Internal functions

    /**
     * @dev Returns a random available EnigmaV4Token to be claimed
     */
    function getEnigmaV4TokenToBeClaimed() private returns (uint256) {
        uint256 random = _getRandomNumber(availableEnigmaV4Tokens.length);
        uint256 tokenId = uint256(availableEnigmaV4Tokens[random]);

        availableEnigmaV4Tokens[random] = availableEnigmaV4Tokens[availableEnigmaV4Tokens.length - 1];
        availableEnigmaV4Tokens.pop();

        return tokenId;
    }

    /**
     * @dev Generates a pseudo-random number.
     */
    function _getRandomNumber(uint256 _upper) private view returns (uint256) {
        uint256 random = uint256(
            keccak256(
                abi.encodePacked(
                    availableEnigmaV4Tokens.length,
                    blockhash(block.number - 1),
                    block.coinbase,
                    block.difficulty,
                    msg.sender
                )
            )
        );

        return random % _upper;
    }

    /**
     * @dev See {ERC721}.
     */
    function _baseURI() internal view virtual override returns (string memory) {
        return baseURI;
    }

    function mulScale(
        uint256 x,
        uint256 y,
        uint128 scale
    ) internal pure returns (uint256) {
        uint256 a = x / scale;
        uint256 b = x % scale;
        uint256 c = y / scale;
        uint256 d = y % scale;

        return a * c * scale + a * d + b * c + (b * d) / scale;
    }
}
// File: ERC165.sol



// SPDX-License-Identifier: MIT

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;
    }
}
// File: ERC721.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC721.sol";
import "./IERC721Receiver.sol";
import "./IERC721Metadata.sol";
import "./IERC721Enumerable.sol";
import "./Address.sol";
import "./Context.sol";
import "./Strings.sol";
import "./ERC165.sol";
import "./Ownable.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, Ownable {
    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) internal _owners;

    // Mapping owner address to token count
    mapping(address => uint256) internal _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}. 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 ||
                ERC721.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
    {
        require(operator != _msgSender(), "ERC721: approve to caller");

        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_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 ||
            ERC721.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);
    }

    function _batchMint(address to, uint256[] memory tokenIds)
        internal
        virtual
    {
        require(to != address(0), "ERC721: mint to the zero address");
        _balances[to] += tokenIds.length;

        for (uint256 i; i < tokenIds.length; i++) {
            require(!_exists(tokenIds[i]), "ERC721: token already minted");

            _beforeTokenTransfer(address(0), to, tokenIds[i]);

            _owners[tokenIds[i]] = to;

            emit Transfer(address(0), to, tokenIds[i]);
        }
    }

    /**
     * @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);
    }

    /**
     * @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 of token that is not own"
        );
        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);
    }

    /**
     * @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 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(to).onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert(
                        "ERC721: transfer to non ERC721Receiver implementer"
                    );
                } else {
                    // solhint-disable-next-line no-inline-assembly
                    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` 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 {}
}
// File: IERC165.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}
// File: IERC20.sol



// SPDX-License-Identifier: MIT

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 `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, 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 `sender` to `recipient` 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 sender,
        address recipient,
        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);
}
// File: IERC721.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./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;
}
// File: IERC721Enumerable.sol



// SPDX-License-Identifier: MIT

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 tokenId);

    /**
     * @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);
}
// File: IERC721Metadata.sol



// SPDX-License-Identifier: MIT

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);
}
// File: IERC721Receiver.sol



// SPDX-License-Identifier: MIT

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);
}
// File: Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./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 () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), 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 {
        emit OwnershipTransferred(_owner, address(0));
        _owner = 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");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}
// File: Strings.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant alphabet = "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] = alphabet[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }

}