Cryo Explorer Ethereum Mainnet

pragma solidity ^0.7.3;

/**
 * @title ERC998ERC721 Top-Down Composable Non-Fungible Token
 * @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-998.md
 * Note: the ERC-165 identifier for this interface is 0x1efdf36a
 */
interface IERC998ERC721TopDown {
    /**
     * @dev This emits when a token receives a child token.
     * @param _from The prior owner of the token.
     * @param _toTokenId The token that receives the child token.
     */
    event ReceivedChild(
        address indexed _from,
        uint256 indexed _toTokenId,
        address indexed _childContract,
        uint256 _childTokenId
    );

    /**
     * @dev This emits when a child token is transferred from a token to an address.
     * @param _fromTokenId The parent token that the child token is being transferred from.
     * @param _to The new owner address of the child token.
     */
    event TransferChild(
        uint256 indexed _fromTokenId,
        address indexed _to,
        address indexed _childContract,
        uint256 _childTokenId
    );

    /**
     * @notice Get the root owner of tokenId.
     * @param _tokenId The token to query for a root owner address
     * @return rootOwner The root owner at the top of tree of tokens and ERC998 magic value.
     */
    function rootOwnerOf(uint256 _tokenId)
        external
        view
        returns (bytes32 rootOwner);

    /**
     * @notice Get the root owner of a child token.
     * @param _childContract The contract address of the child token.
     * @param _childTokenId The tokenId of the child.
     * @return rootOwner The root owner at the top of tree of tokens and ERC998 magic value.
     */
    function rootOwnerOfChild(address _childContract, uint256 _childTokenId)
        external
        view
        returns (bytes32 rootOwner);

    /**
     * @notice Get the parent tokenId of a child token.
     * @param _childContract The contract address of the child token.
     * @param _childTokenId The tokenId of the child.
     * @return parentTokenOwner The parent address of the parent token and ERC998 magic value
     * @return parentTokenId The parent tokenId of _tokenId
     */
    function ownerOfChild(address _childContract, uint256 _childTokenId)
        external
        view
        returns (bytes32 parentTokenOwner, uint256 parentTokenId);

    /**
     * @notice A token receives a child token
     * @param _operator The address that caused the transfer.
     * @param _from The owner of the child token.
     * @param _childTokenId The token that is being transferred to the parent.
     * @param _data Up to the first 32 bytes contains an integer which is the receiving parent tokenId.
     */
    function onERC721Received(
        address _operator,
        address _from,
        uint256 _childTokenId,
        bytes calldata _data
    ) external returns (bytes4);

    /**
     * @notice Transfer child token from top-down composable to address.
     * @param _fromTokenId The owning token to transfer from.
     * @param _to The address that receives the child token
     * @param _childContract The ERC721 contract of the child token.
     * @param _childTokenId The tokenId of the token that is being transferred.
     */
    function transferChild(
        uint256 _fromTokenId,
        address _to,
        address _childContract,
        uint256 _childTokenId
    ) external;

    /**
     * @notice Transfer child token from top-down composable to address.
     * @param _fromTokenId The owning token to transfer from.
     * @param _to The address that receives the child token
     * @param _childContract The ERC721 contract of the child token.
     * @param _childTokenId The tokenId of the token that is being transferred.
     */
    function safeTransferChild(
        uint256 _fromTokenId,
        address _to,
        address _childContract,
        uint256 _childTokenId
    ) external;

    /**
     * @notice Transfer child token from top-down composable to address.
     * @param _fromTokenId The owning token to transfer from.
     * @param _to The address that receives the child token
     * @param _childContract The ERC721 contract of the child token.
     * @param _childTokenId The tokenId of the token that is being transferred.
     * @param _data Additional data with no specified format
     */
    function safeTransferChild(
        uint256 _fromTokenId,
        address _to,
        address _childContract,
        uint256 _childTokenId,
        bytes calldata _data
    ) external;

    /**
     * @notice Transfer bottom-up composable child token from top-down composable to other ERC721 token.
     * @param _fromTokenId The owning token to transfer from.
     * @param _toContract The ERC721 contract of the receiving token
     * @param _toTokenId The receiving token
     * @param _childContract The bottom-up composable contract of the child token.
     * @param _childTokenId The token that is being transferred.
     * @param _data Additional data with no specified format
     */
    function transferChildToParent(
        uint256 _fromTokenId,
        address _toContract,
        uint256 _toTokenId,
        address _childContract,
        uint256 _childTokenId,
        bytes calldata _data
    ) external;

    /**
     * @notice Get a child token from an ERC721 contract.
     * @param _from The address that owns the child token.
     * @param _tokenId The token that becomes the parent owner
     * @param _childContract The ERC721 contract of the child token
     * @param _childTokenId The tokenId of the child token
     */
    function getChild(
        address _from,
        uint256 _tokenId,
        address _childContract,
        uint256 _childTokenId
    ) external;
}

/**
 * @dev The ERC-165 identifier for this interface is 0xa344afe4
 */
interface IERC998ERC721TopDownEnumerable {
    /**
     * @notice Get the total number of child contracts with tokens that are owned by tokenId.
     * @param _tokenId The parent token of child tokens in child contracts
     * @return uint256 The total number of child contracts with tokens owned by tokenId.
     */
    function totalChildContracts(uint256 _tokenId)
        external
        view
        returns (uint256);

    /**
     * @notice Get child contract by tokenId and index
     * @param _tokenId The parent token of child tokens in child contract
     * @param _index The index position of the child contract
     * @return childContract The contract found at the tokenId and index.
     */
    function childContractByIndex(uint256 _tokenId, uint256 _index)
        external
        view
        returns (address childContract);

    /**
     * @notice Get the total number of child tokens owned by tokenId that exist in a child contract.
     * @param _tokenId The parent token of child tokens
     * @param _childContract The child contract containing the child tokens
     * @return uint256 The total number of child tokens found in child contract that are owned by tokenId.
     */
    function totalChildTokens(uint256 _tokenId, address _childContract)
        external
        view
        returns (uint256);

    /**
     * @notice Get child token owned by tokenId, in child contract, at index position
     * @param _tokenId The parent token of the child token
     * @param _childContract The child contract of the child token
     * @param _index The index position of the child token.
     * @return childTokenId The child tokenId for the parent token, child token and index
     */
    function childTokenByIndex(
        uint256 _tokenId,
        address _childContract,
        uint256 _index
    ) external view returns (uint256 childTokenId);
}

interface IERC998ERC721BottomUp {
    /**
     * @notice Transfer token from owner address to a token
     * @param _from The owner address
     * @param _toContract The ERC721 contract of the receiving token
     * @param _toTokenId The receiving token
     * @param _data Additional data with no specified format
     */
    function transferToParent(
        address _from,
        address _toContract,
        uint256 _toTokenId,
        uint256 _tokenId,
        bytes calldata _data
    ) external;
}

pragma solidity ^0.7.3;
interface MoonCatRescue {
    function getCatDetails(bytes5 catId)
        external
        view
        returns (
            bytes5 id,
            address owner,
            bytes32 name,
            address onlyOfferTo,
            uint256 offerPrice,
            address requester,
            uint256 requestPrice
        );

    function rescueOrder(uint256 _rescueOrder)
        external
        view
        returns (bytes5 catId);

    function acceptAdoptionOffer(bytes5 catId) external payable;

    function acceptAdoptionRequest(bytes5 catId) external;

    function adoptionRequests(bytes5 _catId)
        external
        view
        returns (
            bool exists,
            bytes5 catId,
            address requester,
            uint256 price
        );

    function adoptionOffers(bytes5 _catId)
        external
        view
        returns (
            bool exists,
            bytes5 catId,
            address seller,
            uint256 price,
            address offerOnlyTo
        );

    function giveCat(bytes5 catId, address to) external;

    function catOwners(bytes5) external view returns (address);

    function makeAdoptionOfferToAddress(bytes5 catId, uint256 price, address to) external;

    function makeAdoptionOffer(bytes5 catId, uint256 price) external;

    function withdraw() external;
}

pragma solidity ^0.7.3;
interface MoonCatsWrapped {

    /**
     * @dev in the original contract, this is a public map property, so is
     * using the default getter action, which does NOT check for "exists";
     * if this returns a zero, it might be referencing token ID #0, or it might
     * be meaning "that MoonCat ID is not wrapped in this contract".
     */
    function _catIDToTokenID(bytes5 catId) external pure
        returns (uint256);

    /**
     * @dev in the original contract, this is a public map property, so is
     * using the default getter action, which does NOT check for "exists".
     * However, no MoonCat has an ID of `0x0000000000`, so if this returns
     * all zeroes, it means "that token ID does not exist in this contract".
     */
    function _tokenIDToCatID(uint256 _tokenID) external pure
        returns (bytes5 catId);

    function safeTransferFrom(address from, address to, uint256 tokenId) external;
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) external;
    function balanceOf(address owner) external view returns (uint256 balance);
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);
    function wrap(bytes5 catId) external;
    function unwrap(uint256 tokenID) external;
    function ownerOf(uint256 tokenID) external view returns(address);
    function setApprovalForAll(address operator, bool _approved) external;
    function isApprovedForAll(address owner, address operator) external view returns (bool);
    function approve(address to, uint256 tokenId) external;
}

// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.7.3;

import "./openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721Holder.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Pausable.sol";
import "./IERC998.sol";
import "./MoonCatOrderLookup.sol";

//        ##          ##
//      ##  ##      ##  ##
//      ##..  ######  ..##
//    ####              ####
//    ##                  ##
//    ##    ()      ()    ##
//    ##                  ##
//    ##     \  ##  /     ##
//    ##      \/  \/      ##
//      ##              ##
//        ##############
//
//    #AcclimatedMoonCatsGlow
//  https://mooncat.community/


/**
 * @title MoonCat​Acclimator
 * @notice Accepts an original MoonCat and wraps it to present an ERC721- and ERC998-compliant asset
 * @notice Accepts a MoonCat wrapped with the older wrapping contract (at 0x7C40c3...) and re-wraps them
 * @notice Ownable by an admin address. Rights of the Owner are to pause and unpause the contract, and update metadata URL
 */
contract MoonCatAcclimator is
    ERC721,
    ERC721Holder,
    Ownable,
    Pausable,
    IERC998ERC721TopDown,
    IERC998ERC721TopDownEnumerable
{
    bytes32 private constant ERC998_MAGIC_VALUE = 0x00000000000000000000000000000000000000000000000000000000cd740db5;
    bytes4 private constant _INTERFACE_ID_ERC998ERC721TopDown = 0x1efdf36a;

    MoonCatOrderLookup public rescueOrderLookup;

    MoonCatRescue MCR = MoonCatRescue(0x60cd862c9C687A9dE49aecdC3A99b74A4fc54aB6);
    MoonCatsWrapped OLD_MCRW = MoonCatsWrapped(0x7C40c393DC0f283F318791d746d894DdD3693572);

    constructor(string memory baseURI)
        ERC721(unicode"Acclimated​MoonCats", unicode"😺")
        Ownable()
    {
        _registerInterface(_INTERFACE_ID_ERC998ERC721TopDown);
        rescueOrderLookup = new MoonCatOrderLookup();
        setBaseURI(baseURI);
        _pause(); // Start in a paused state
    }

    function pause() public whenNotPaused onlyOwner {
        _pause();
    }
    function unpause() public whenPaused onlyOwner {
        _unpause();
    }

    /**
     * @dev Emitted when `catId` token is wrapped into `tokenId`, owned by `owner`.
     */
    event MoonCatAcclimated(
        uint256 tokenId,
        address indexed owner
    );

    /**
     * @dev Emitted when `catId` token is unwrapped from `tokenId`, owned by `owner`.
     */
    event MoonCatDeacclimated(
        uint256 tokenId,
        address indexed owner
    );

    /**
     * @dev returns tokenId of newly minted wrapped MoonCat
     *
     * Requirements:
     *
     * - Do not need to check if _msgSender() is MoonCat owner as the wrapped token is assigned to owner (even if that's not _msgSender())
     * - Owner needs to call makeAdoptionOfferToAddress() in moonCatRescue first.
     * Emits a {Transfer} ERC721 event.
     * @param _rescueOrder the minting order of the MoonCat to wrap
     * @return the ID (rescue order) of the minted token
     */
    function wrap(uint256 _rescueOrder) public returns (uint256) {
        bytes5 catId = MCR.rescueOrder(_rescueOrder);
        address _owner = MCR.catOwners(catId);
        MCR.acceptAdoptionOffer(catId);
        return _wrap(_owner, _rescueOrder);
    }

    /**
     * @dev returns tokenId of newly minted wrapped MoonCat
     *
     * This method must not allow an adoption offer specifically to the new Wrapper address to be buy-able by anyone,
     * because that is how the real owner sets up a manual wrapping of the MoonCat (where they don't really intend to sell).
     *
     * Requirements:
     *
     * - MoonCat at `_rescueOrder` must be offered for sale to any address.
     * - Must have active makeAdoptionOffer() in moonCatRescue contract.
     * Emits a {Transfer} and {MoonCatAcclimated} event.
     * @param _rescueOrder the minting order of the MoonCat to wrap
     * @return the ID (rescue order) of the minted token
     */
    function buyAndWrap(uint256 _rescueOrder) public payable returns (uint256) {
        bytes5 catId = MCR.rescueOrder(_rescueOrder);
        (bool exists, , , , address onlyOfferTo) = MCR.adoptionOffers(catId);
        require(
            onlyOfferTo == address(0) && exists,
            "That MoonCat is not for sale"
        );
        MCR.acceptAdoptionOffer{value: msg.value}(catId);
        return _wrap(_msgSender(), _rescueOrder);
    }

    /**
     * @dev returns tokenId of burned unwrapped MoonCat
     *
     * Requirements:
     *
     * - msgSender() must be owner.
     * Emits a {Transfer} and {MoonCatDeacclimated} event.
     * @param _tokenId the minting order of the MoonCat to unwrap
     * @return the ID (rescue order) of the burned token
     */
    function unwrap(uint256 _tokenId) public returns (uint256) {
        require(ownerOf(_tokenId) == _msgSender(), "Not your MoonCat!");
        require(
            super._exists(_tokenId),
            "That MoonCat is not wrapped in this contract"
        );
        bytes5 catId = MCR.rescueOrder(_tokenId);
        MCR.giveCat(catId, ownerOf(_tokenId));
        _burn(_tokenId);
        emit MoonCatDeacclimated(_tokenId, _msgSender());
        return _tokenId;
    }

    /**
     * @dev wraps MoonCat that was safeTransferFrom() the old MoonCat wrapper directly in one transaction
     *
     * Requirements:
     * - Owner of old wrapped MoonCat must include the rescueOrder in the calldata as a bytes32
     * Emits a {Transfer} and {MoonCatAcclimated} event.
     * @param _to the address that is to be the owner of the newly-wrapped token
     * @param _oldTokenID the ID of the token in the other wrapping contract
     * @param _rescueOrder the minting order of the MoonCat being wrapped
     * @return the ID (rescue order) of the minted token
     */
    function _wrapOnSafeTransferFromReceipt(
        address _to,
        uint256 _oldTokenID,
        uint256 _rescueOrder
    ) internal returns (uint256) {
        if (
            MCR.rescueOrder(_rescueOrder) !=
            OLD_MCRW._tokenIDToCatID(_oldTokenID)
        ) {
            // Look up rescue order in Lookup contract
            require(
                rescueOrderLookup.oldTokenIdExists(_oldTokenID),
                "Unable to determine proper rescueOrder for this old token ID"
            );
            _rescueOrder = rescueOrderLookup.oldTokenIdToRescueOrder(
                _oldTokenID
            );
            require(
                MCR.rescueOrder(_rescueOrder) ==
                    OLD_MCRW._tokenIDToCatID(_oldTokenID),
                "_oldTokenID and _rescueOrder do not match same catID"
            );
        }
        OLD_MCRW.unwrap(_oldTokenID);
        return _wrap(_to, _rescueOrder);
    }

    /**
     * @dev wraps an unwrapped MoonCat
     *
     * notes:
     * Emits a {Transfer} and {MoonCatAcclimated} event.
     * @param _owner the address that should be the new owner of the newly-created token
     * @param _tokenId the ID of the token to create (rescue order of the MoonCat)
     * @return the ID (rescue order) of the minted token
     */
    function _wrap(address _owner, uint256 _tokenId)
        internal
        returns (uint256)
    {
        require(!paused(), "Attempted wrap while paused");
        _mint(_owner, _tokenId);
        emit MoonCatAcclimated(_tokenId, _msgSender());
        return _tokenId;
    }

    /**
     * @dev Always returns `IERC721Receiver.onERC721Received.selector`
     *
     * This function handles both automatic rewrapping of old-wrapped MoonCats, and assigning ERC721 tokens as "child assets"
     * of MoonCats already wrapped with this contract.
     *
     * If the incoming token is an old-wrapped Mooncat, the `_data` variable is structured as
     * the first 32 bytes are the rescue order of the transferred MoonCat, subsequent 20 bytes
     * are the new owner's address. If the rescue order is not supplied, the `_oldTokenId` is
     * looked up in the {MoonCatOrderLookup} contract. If a new owner's address is not
     * supplied, the new owner will be assigned as the `_from` sender.
     * Emits a {Transfer} and {MoonCatAcclimated} event.
     *
     * If the incoming token is any other type of ERC721, the `_data` variable is structured as
     * the first 32 bytes are the token ID (rescue order) of the MoonCat that is to receive that assest.
     * Emits a {ReceivedChild} event.
     *
     * @param _operator the _msgSender of the transaction
     * @param _from the address of the former owner of the incoming token
     * @param _oldTokenId the ID of the incoming token
     * @param _data additional metdata
     */
    function onERC721Received(
        address _operator,
        address _from,
        uint256 _oldTokenId,
        bytes calldata _data
    ) public override(ERC721Holder, IERC998ERC721TopDown) returns (bytes4) {
        // Using msg.sender here instead of _operator because we want to know the most recent transaction source,
        // not the start of the chain
        if (msg.sender == address(0x7C40c393DC0f283F318791d746d894DdD3693572)) {
            // This is a Wrapped MoonCat incoming. Don't make it a child, instead unwrap and re-wrap it

            // Who should own this MoonCat after wrapping?
            address _to =
                (_data.length >= 32 + 20 && bytesToAddress(_data, 32) != address(0))
                    ? bytesToAddress(_data, 32)
                    : _from;
            require(
                _to != address(0) && _to != address(this),
                "Invalid destination owner specified"
            );

            _wrapOnSafeTransferFromReceipt(
                _to,
                _oldTokenId,
                (_data.length >= 32) ? toUint256(_data, 0) : 0
            );
            return ERC721Holder.onERC721Received(_operator, _from, _oldTokenId, _data);
        }

        // Otherwise, handle as ERC998 Child incoming
        require(_data.length > 0, "_data must contain the uint256 tokenId to transfer the child token to");
        // convert up to 32 bytes of_data to uint256, owner NFT tokenId passed as uint in bytes
        uint256 tokenId;
        assembly {tokenId := calldataload(164)}
        if (_data.length < 32) {
            tokenId = tokenId >> 256 - _data.length * 8;
        }
        _receiveChild(_from, tokenId, msg.sender, _oldTokenId);
        require(ERC721(msg.sender).ownerOf(_oldTokenId) != address(0), "Child token not owned");
        return ERC721Holder.onERC721Received(_operator, _from, _oldTokenId, _data);
    }

    /**
     * @dev sets the base URI
     *
     * notes:
     * - only callable by the contract owner
     */
    function setBaseURI(string memory _newBaseURI) public onlyOwner {
        _setBaseURI(_newBaseURI);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     * This contract returns the locally-wrapped token count as well as old-wrapped MoonCats
     * that are mapped in the {MoonCatOrderLookup} contract.
     */
    function balanceOf(address _owner) public view override returns (uint256) {
        return
            super.balanceOf(_owner) +
            rescueOrderLookup.entriesPerAddress(_owner);
    }

    /**
    * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     * This contract enumerates the locally-wrapped token count as well as old-wrapped MoonCats
     * that are mapped in the {MoonCatOrderLookup} contract.
    */
    function tokenOfOwnerByIndex(address _owner, uint256 _index)
        public
        view
        override
        returns (uint256)
    {
        uint256 localBalance = super.balanceOf(_owner);
        if (_index < localBalance) {
            // This index is in the range of tokens owned by that address here in this contract
            return super.tokenOfOwnerByIndex(_owner, _index);
        }

        // Looking to enumerate a token that's mapped to the old wrapping contract
        uint16 countFound = 0;
        for (uint256 i = 0; i < OLD_MCRW.balanceOf(_owner); i++) {
            uint256 oldTokenId = OLD_MCRW.tokenOfOwnerByIndex(_owner, i);
            if (rescueOrderLookup.oldTokenIdExists(oldTokenId)) {
                countFound++;
                if (countFound == _index - localBalance + 1) {
                    return
                        rescueOrderLookup.oldTokenIdToRescueOrder(oldTokenId);
                }
            }
        }
        revert("Cannot find token ID for that index");
    }

    /**
    * @dev See {IERC721-ownerOf}.
    */
    function ownerOf(uint256 _tokenId) public view override returns (address) {
        if (super._exists(_tokenId)) {
            return super.ownerOf(_tokenId);
        }

        // Check other wrapper

        // First see if we're dealing with the MoonCat that was the zeroth-wrapped MoonCat in other wrapper
        bytes5 thisMoonCatID = MCR.rescueOrder(_tokenId);
        if (thisMoonCatID == OLD_MCRW._tokenIDToCatID(0)) {
            return OLD_MCRW.ownerOf(0);
        }
        uint256 otherID = OLD_MCRW._catIDToTokenID(thisMoonCatID);
        // We're not dealing with the zeroth-wrapped MoonCat, so a zero here is an indication they don't exist
        require(otherID > 0, "That MoonCat is not wrapped");
        return OLD_MCRW.ownerOf(otherID);
    }

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address _owner, address _operator)
        public
        view
        virtual
        override
        returns (bool)
    {
        return
            rescueOrderLookup.entriesPerAddress(_owner) == 0
                ? super.isApprovedForAll(_owner, _operator)
                : super.isApprovedForAll(_owner, _operator) &&
                    OLD_MCRW.isApprovedForAll(_owner, address(this));
    }

    /**
     * @dev See {ERC721-_isApprovedOrOwner}.
     */
    function _isApprovedOrOwner(address _spender, uint256 _tokenId)
        internal
        view
        override
        returns (bool)
    {
        require(
            _exists(_tokenId),
            "ERC721: operator query for nonexistent token"
        );
        // Differs here from OpenZeppelin standard:
        // Calls `ownerOf` instead of `ERC721.ownerOf`
        address _owner = ownerOf(_tokenId);
        return (_spender == _owner ||
            getApproved(_tokenId) == _spender ||
            ERC721.isApprovedForAll(_owner, _spender));
    }

    /**
     * @dev See {ERC721-approve}.
     */
    function approve(address _to, uint256 _tokenId) public override {
        address _owner = ownerOf(_tokenId);
        require(_to != _owner, "ERC721: approval to current owner");
        // Differs here from OpenZeppelin standard:
        // Calls `isApprovedForAll` instead of `ERC721.isApprovedForAll`
        require(
            _msgSender() == _owner || isApprovedForAll(_owner, _msgSender()),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _approve(_to, _tokenId);
    }

    /**
     * @dev rewrap several MoonCats from the old wrapper at once
     * Owner needs to call setApprovalForAll in old wrapper first.
     * @param _rescueOrders an array of MoonCats, identified by rescue order, to rewrap
     * @param _oldTokenIds an array holding the corresponding token ID
     *        in the old wrapper for each MoonCat to be rewrapped
     */
    function batchReWrap(
        uint256[] memory _rescueOrders,
        uint256[] memory _oldTokenIds
    ) public {
        for (uint16 i = 0; i < _rescueOrders.length; i++) {
            address _owner = OLD_MCRW.ownerOf(_oldTokenIds[i]);
            OLD_MCRW.safeTransferFrom(
                _owner,
                address(this),
                _oldTokenIds[i],
                abi.encodePacked(
                    uintToBytes(_rescueOrders[i]),
                    addressToBytes(_owner)
                )
            );
        }
    }

    /**
     * @dev Take a list of unwrapped MoonCat rescue orders and wrap them.
     * @param _rescueOrders an array of MoonCats, identified by rescue order, to rewrap
     */
    function batchWrap(uint256[] memory _rescueOrders) public {
        for (uint16 i = 0; i < _rescueOrders.length; i++) {
            wrap(_rescueOrders[i]);
        }
    }

    /**
     * @dev Take a list of MoonCats wrapped in this contract and unwrap them.
     * @param _rescueOrders an array of MoonCats, identified by rescue order, to unwrap
     */
    function batchUnwrap(uint256[] memory _rescueOrders) public {
        for (uint16 i = 0; i < _rescueOrders.length; i++) {
            unwrap(_rescueOrders[i]);
        }
    }

    /**
     * @dev See {ERC721-_transfer}.
     * If the token being transferred exists in this contract, the standard ERC721 logic is used.
     * If the token does not exist in this contract, look it up in the old wrapping contract,
     * and attempt to wrap-then-transfer it.
     */
    function _transfer(
        address _from,
        address _to,
        uint256 _tokenId
    ) internal override {
        if (super._exists(_tokenId)) {
            return super._transfer(_from, _to, _tokenId);
        }

        require(_to != address(0), "ERC721: transfer to the zero address");

        if (_to == address(this)) {
            // Sending the token to be owned by this contract? That's not what they meant; make it owned by the original owner after re-wrapping
            _to = _from;
        }
        uint256 oldTokenId =
            OLD_MCRW._catIDToTokenID(MCR.rescueOrder(_tokenId));
        OLD_MCRW.safeTransferFrom(
            _from,
            address(this),
            oldTokenId,
            abi.encodePacked(uintToBytes(_tokenId), addressToBytes(_to))
        );
        rescueOrderLookup.removeEntry(oldTokenId);
    }

    /**
     * @dev See {ERC721-_exists}.
     * If the token being queried exists in this contract, the standard ERC721 logic is used.
     * If the token does not exist in this contract, look it up in the old wrapping contract,
     * and see if it exists there.
     */
    function _exists(uint256 _tokenId) internal view override returns (bool) {
        if (super._exists(_tokenId)) {
            return true;
        }

        // Check if exists in old wrapping contract
        bytes5 realMoonCatZero = OLD_MCRW._tokenIDToCatID(0);
        bytes5 thisMoonCatID = MCR.rescueOrder(_tokenId);
        if (thisMoonCatID == realMoonCatZero) {
            return true;
        }

        return OLD_MCRW._catIDToTokenID(thisMoonCatID) != 0;
    }

    ///// ERC998 /////
    using EnumerableSet for EnumerableSet.UintSet;
    using EnumerableSet for EnumerableSet.AddressSet;

    /// @dev mapping of local token IDs, and which addresses they own children at.
    /// tokenId => child contract
    mapping(uint256 => EnumerableSet.AddressSet) private childContracts;

    /// @dev mapping of local token IDs, addresses they own children at, and IDs of the specific child tokens
    /// tokenId => (child address => array of child tokens)
    mapping(uint256 => mapping(address => EnumerableSet.UintSet)) private childTokens;

    /// @dev mapping of addresses of child tokens, the specific child token IDs, and which local token owns them
    /// child address => childId => tokenId
    mapping(address => mapping(uint256 => uint256)) internal childTokenOwner;
    uint8 constant TOKEN_OWNER_OFFSET = 10;

    /**
     * @dev a token has been transferred to this contract mark which local token is to now own it
     * Emits a {ReceivedChild} event.
     *
     * @param _from the address who sent the token to this contract
     * @param _tokenId the local token ID that is to be the parent
     * @param _childContract the address of the child token's contract
     * @param _childTokenId the ID value of teh incoming child token
     */
    function _receiveChild(address _from, uint256 _tokenId, address _childContract, uint256 _childTokenId) private {
        require(!paused(), "Child received while paused");
        require(super._exists(_tokenId), "That MoonCat is not wrapped in this contract");
        require(childTokens[_tokenId][_childContract].contains(_childTokenId) == false, "Cannot receive child token because it has already been received");
        childContracts[_tokenId].add(_childContract);
        childTokens[_tokenId][_childContract].add(_childTokenId);
        childTokenOwner[_childContract][_childTokenId] = _tokenId + TOKEN_OWNER_OFFSET;
        emit ReceivedChild(_from, _tokenId, _childContract, _childTokenId);
    }

    /**
     * @dev See {IERC998ERC721TopDown-getChild}.
     */
    function getChild(
        address _from,
        uint256 _tokenId,
        address _childContract,
        uint256 _childTokenId
    ) public override {
        _receiveChild(_from, _tokenId, _childContract, _childTokenId);
        IERC721(_childContract).transferFrom(_from, address(this), _childTokenId);
    }

    /**
     * @dev Given a child address/ID that is owned by some token in this contract, return that owning token's owner
     * @param _childContract the address of the child asset being queried
     * @param _childTokenId the specific ID of the child asset being queried
     * @return parentTokenOwner the address of the owner of that child's parent asset
     * @return parentTokenId the local token ID that is the parent of that child asset
     */
    function _ownerOfChild(address _childContract, uint256 _childTokenId) internal view returns (address parentTokenOwner, uint256 parentTokenId) {
        parentTokenId = childTokenOwner[_childContract][_childTokenId];
        require(parentTokenId > 0, "That child is not owned by a token in this contract");
        return (ownerOf(parentTokenId - TOKEN_OWNER_OFFSET), parentTokenId - TOKEN_OWNER_OFFSET);
    }

    /**
     * @dev See {IERC998ERC721TopDown-ownerOfChild}.
     */
    function ownerOfChild(address _childContract, uint256 _childTokenId)
        public
        override
        view
        returns (bytes32 parentTokenOwner, uint256 parentTokenId)
    {
        parentTokenId = childTokenOwner[_childContract][_childTokenId];
        require(parentTokenId > 0, "That child is not owned by a token in this contract");
        return (ERC998_MAGIC_VALUE << 224 | bytes32(uint256(ownerOf(parentTokenId - TOKEN_OWNER_OFFSET))), parentTokenId - TOKEN_OWNER_OFFSET);
    }

    /**
     * @dev See {IERC998ERC721TopDown-rootOwnerOf}.
     */
    function rootOwnerOf(uint256 _tokenId)
        public
        override
        view
        returns (bytes32 rootOwner)
    {
        return rootOwnerOfChild(address(0), _tokenId);
    }

    /**
     * @dev See {IERC998ERC721TopDown-rootOwnerOfChild}.
     */
    function rootOwnerOfChild(address _childContract, uint256 _childTokenId)
        public
        override
        view
        returns (bytes32 rootOwner)
    {
        address rootOwnerAddress;
        if (_childContract != address(0)) {
            (rootOwnerAddress, _childTokenId) = _ownerOfChild(_childContract, _childTokenId);
        } else {
            rootOwnerAddress = ownerOf(_childTokenId);
        }
        // Case 1: Token owner is this contract and token.
        while (rootOwnerAddress == address(this)) {
            (rootOwnerAddress, _childTokenId) = _ownerOfChild(rootOwnerAddress, _childTokenId);
        }

        (bool callSuccess, bytes memory data) = rootOwnerAddress.staticcall(abi.encodeWithSelector(0xed81cdda, address(this), _childTokenId));
        if (data.length != 0) {
            rootOwner = abi.decode(data, (bytes32));
        }

        if(callSuccess == true && rootOwner >> 224 == ERC998_MAGIC_VALUE) {
            // Case 2: Token owner is other top-down composable
            return rootOwner;
        }
        else {
            // Case 3: Token owner is other contract
            // Or
            // Case 4: Token owner is user
            return ERC998_MAGIC_VALUE << 224 | bytes32(uint256(rootOwnerAddress));
        }
    }

    /**
     * @dev remove internal records linking a given child to a given parent
     * @param _tokenId the local token ID that is the parent of the child asset
     * @param _childContract the address of the child asset to remove
     * @param _childTokenId the specific ID representing the child asset to be removed
     */
    function _removeChild(uint256 _tokenId, address _childContract, uint256 _childTokenId) private {
        require(
            childTokens[_tokenId][_childContract].contains(_childTokenId),
            "Child token not owned by token"
        );

        // remove child token
        childTokens[_tokenId][_childContract].remove(_childTokenId);
        delete childTokenOwner[_childContract][_childTokenId];

        // remove contract
        if (childTokens[_tokenId][_childContract].length() == 0) {
            childContracts[_tokenId].remove(_childContract);
        }
    }

    /**
     * @dev check permissions are correct for a transfer of a child asset
     * @param _fromTokenId the local ID of the token that is the parent
     * @param _to the address this child token is being transferred to
     * @param _childContract the address of the child asset's contract
     * @param _childTokenId the specific ID for the child asset being transferred
     */
    function _checkTransferChild(
        uint256 _fromTokenId,
        address _to,
        address _childContract,
        uint256 _childTokenId
    ) private view {
        require(!paused(), "Child transfer while paused");
        uint256 tokenId = childTokenOwner[_childContract][_childTokenId];
        require(tokenId > 0, "Child asset is not owned by a token in this contract");
        tokenId -= TOKEN_OWNER_OFFSET;
        require(tokenId == _fromTokenId, "That MoonCat does not own that asset");
        require(_to != address(0), "Transfer to zero address");
        address rootOwner = address(uint160(uint256(rootOwnerOf(_fromTokenId))));
        require(
            _msgSender() == rootOwner || getApproved(_fromTokenId) == _msgSender() || ERC721.isApprovedForAll(rootOwner, _msgSender()),
            "Not allowed to transfer child assets of that MoonCat"
        );
    }

    /**
     * @dev See {IERC998ERC721TopDown-safeTransferChild}.
     */
    function safeTransferChild(
        uint256 _fromTokenId,
        address _to,
        address _childContract,
        uint256 _childTokenId
    ) public override {
        _checkTransferChild(_fromTokenId, _to, _childContract, _childTokenId);
        _removeChild(_fromTokenId, _childContract, _childTokenId);
        ERC721(_childContract).safeTransferFrom(address(this), _to, _childTokenId);
        emit TransferChild(_fromTokenId, _to, _childContract, _childTokenId);
    }

    /**
     * @dev See {IERC998ERC721TopDown-safeTransferChild}.
     */
    function safeTransferChild(
        uint256 _fromTokenId,
        address _to,
        address _childContract,
        uint256 _childTokenId,
        bytes calldata _data
    ) public override {
        _checkTransferChild(_fromTokenId, _to, _childContract, _childTokenId);
        _removeChild(_fromTokenId, _childContract, _childTokenId);
        ERC721(_childContract).safeTransferFrom(address(this), _to, _childTokenId, _data);
        emit TransferChild(_fromTokenId, _to, _childContract, _childTokenId);
    }

    /**
     * @dev See {IERC998ERC721TopDown-transferChild}.
     */
    function transferChild(
        uint256 _fromTokenId,
        address _to,
        address _childContract,
        uint256 _childTokenId
    ) public override {
        _checkTransferChild(_fromTokenId, _to, _childContract, _childTokenId);
        _removeChild(_fromTokenId, _childContract, _childTokenId);
        //this is here to be compatible with cryptokitties and other old contracts that require being owner and approved
        // before transferring.
        //does not work with current standard which does not allow approving self, so we must let it fail in that case.
        //0x095ea7b3 == "approve(address,uint256)"
        (bool success, bytes memory data) = _childContract.call(abi.encodeWithSelector(0x095ea7b3, this, _childTokenId));
        require(
            success && (data.length == 0 || abi.decode(data, (bool))),
            'Failed to Approve'
        );
        ERC721(_childContract).transferFrom(address(this), _to, _childTokenId);
        emit TransferChild(_fromTokenId, _to, _childContract, _childTokenId);
    }

    /**
     * @dev See {IERC998ERC721TopDown-transferChildToParent}.
     */
    function transferChildToParent(
        uint256 _fromTokenId,
        address _toContract,
        uint256 _toTokenId,
        address _childContract,
        uint256 _childTokenId,
        bytes calldata _data
    ) public override {
        _checkTransferChild(_fromTokenId, _toContract, _childContract, _childTokenId);
        _removeChild(_fromTokenId, _childContract, _childTokenId);
        IERC998ERC721BottomUp(_childContract).transferToParent(address(this), _toContract, _toTokenId, _childTokenId, _data);
        emit TransferChild(_fromTokenId, _toContract, _childContract, _childTokenId);
    }

    ///// ERC998 Enumerable

    /**
     * @dev See {IERC998ERC721TopDownEnumerable-totalChildContracts}.
     */
    function totalChildContracts(uint256 _tokenId)
        external
        override
        view
        returns (uint256)
    {
        return childContracts[_tokenId].length();
    }

    /**
     * @dev See {IERC998ERC721TopDownEnumerable-childContractByIndex}.
     */
    function childContractByIndex(uint256 _tokenId, uint256 _index)
        external
        override
        view
        returns (address childContract)
    {
        return childContracts[_tokenId].at(_index);
    }

    /**
     * @dev See {IERC998ERC721TopDownEnumerable-totalChildTokens}.
     */
    function totalChildTokens(uint256 _tokenId, address _childContract) external override view returns (uint256) {
        return childTokens[_tokenId][_childContract].length();
    }

    /**
     * @dev See {IERC998ERC721TopDownEnumerable-childTokenByIndex}.
     */
    function childTokenByIndex(uint256 _tokenId, address _childContract, uint256 _index) external override view returns (uint256 childTokenId) {
        return childTokens[_tokenId][_childContract].at(_index);
    }
}

// UTILITIES

/**
 * @dev converts bytes (which is at least 32 bytes long) to uint256
 */
function toUint256(bytes memory _bytes, uint256 _start) pure returns (uint256) {
    require(_start + 32 >= _start, "toUint256_overflow");
    require(_bytes.length >= _start + 32, "toUint256_outOfBounds");
    uint256 tempUint;

    assembly {
        tempUint := mload(add(add(_bytes, 0x20), _start))
    }

    return tempUint;
}

/**
 * @dev converts uint256 to a bytes(32) object
 */
function uintToBytes(uint256 x) pure returns (bytes memory b) {
    b = new bytes(32);
    assembly {
        mstore(add(b, 32), x)
    }
}

/**
 * @dev converts bytes (which is at least 20 bytes long) to address
 */
function bytesToAddress(bytes memory bys, uint256 _start)
    pure
    returns (address addr)
{
    assembly {
        addr := mload(add(add(bys, 20), _start))
    }
}

/**
 * @dev converts address to a bytes(32) object
 */
function addressToBytes(address a) pure returns (bytes memory) {
    return abi.encodePacked(a);
}

// SPDX-License-Identifier: GPL-3.0-only
pragma solidity ^0.7.3;

import "@openzeppelin/contracts/access/Ownable.sol";
import "./IMoonCatRescue.sol";
import "./IMoonCatsWrapped.sol";

/**
 * @title MoonCat Order Lookup
 * @notice A space to have an on-chain record mapping token IDs for OLD_MCRW to their original "rescue order" IDs
 * @dev This contract exists because there is no MoonCat ID => Rescue ID function
 * on the original MoonCatRescue contract. The only way to tell a given MoonCat's
 * rescue order if you don't know it is to iterate through the whole `rescueOrder`
 * array. Looping through that whole array in a smart contract would be
 * prohibitively high gas-usage, and so this alternative is needed.
 */
contract MoonCatOrderLookup is Ownable {

    MoonCatRescue MCR = MoonCatRescue(0x60cd862c9C687A9dE49aecdC3A99b74A4fc54aB6);
    MoonCatsWrapped OLD_MCRW = MoonCatsWrapped(0x7C40c393DC0f283F318791d746d894DdD3693572);

    uint256[25600] private _oldTokenIdToRescueOrder;
    uint8 constant VALUE_OFFSET = 10;

    constructor() Ownable() {}

    /**
      * @dev Submit a batch of token IDs, and their associated rescue orders
      * This is the primary method for the utility of the contract. Anyone
      * can submit this pairing information (not just the owners of the token)
      * and the information can be submitted in batches.
      *
      * Submitting pairs of token IDs with their rescue orders is verified with
      * the original MoonCatRescue contract before recording.
      *
      * Within the private array holding this information, a VALUE_OFFSET is used
      * to differentiate between "not set" and "set to zero" (because Solidity
      * has no concept of "null" or "undefined"). Because the maximum value of the
      * rescue ordering can only be 25,600, we can safely shift the stored values
      * up, and not hit the uint256 limit.
      */
    function submitRescueOrder(
        uint256[] memory oldTokenIds,
        uint16[] memory rescueOrders
    ) public {
        for (uint256 i = 0; i < oldTokenIds.length; i++) {
            require(
                MCR.rescueOrder(rescueOrders[i]) == OLD_MCRW._tokenIDToCatID(oldTokenIds[i]),
                "Pair does not match!"
            );
            _oldTokenIdToRescueOrder[oldTokenIds[i]] = rescueOrders[i] + VALUE_OFFSET;
        }
    }

    /**
      * @dev verify a given old token ID is mapped yet or not
      *
      * This function can use just a zero-check because internally all values are
      * stored with a VALUE_OFFSET added onto them (e.g. storing an actual zero
      * is saved as 0 + VALUE_OFFSET = 10, internally), so anything set to an
      * actual zero means "unset".
      */
    function _exists(uint256 oldTokenId) internal view returns (bool) {
        return _oldTokenIdToRescueOrder[oldTokenId] != 0;
    }

    /**
     * @dev public function to verify whether a given old token ID is mapped or not
     */
    function oldTokenIdExists(uint256 oldTokenId) public view returns(bool) {
        return _exists(oldTokenId);
    }

    /**
     * @dev given an old token ID, return the rescue order of that MoonCat
     *
     * Throws an error if that particular token ID does not have a recorded
     * mapping to a rescue order.
     */
    function oldTokenIdToRescueOrder(uint256 oldTokenId) public view returns(uint256) {
        require(_exists(oldTokenId), "That token ID is not mapped yet");
        return _oldTokenIdToRescueOrder[oldTokenId] - VALUE_OFFSET;
    }

    /**
     * @dev remove a mapping from the data structure
     *
     * This allows reclaiming some gas, so as part of the re-wrapping process,
     * this gets called by the Acclimator contract, to recoup some gas for the
     * MoonCat owner.
     */
    function removeEntry(uint256 _oldTokenId) public onlyOwner {
        delete _oldTokenIdToRescueOrder[_oldTokenId];
    }

    /**
     * @dev for a given address, iterate through all the tokens they own in the
     * old wrapping contract, and for each of them, determine how many are mapped
     * in this lookup contract.
     *
     * This method is used by the Acclimator `balanceOf` and `tokenOfOwnerByIndex`
     * to be able to enumerate old-wrapped MoonCats as if they were already
     * re-wrapped in the Acclimator contract.
     */
    function entriesPerAddress(address _owner) public view returns (uint256) {
        uint256 countMapped = 0;
        for (uint256 i = 0; i < OLD_MCRW.balanceOf(_owner); i++) {
            uint256 oldTokenId = OLD_MCRW.tokenOfOwnerByIndex(_owner, i);
            if (_exists(oldTokenId)) {
                countMapped++;
            }
        }
        return countMapped;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        uint256 c = a + b;
        if (c < a) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b > a) return (false, 0);
        return (true, a - b);
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
        if (a == 0) return (true, 0);
        uint256 c = a * b;
        if (c / a != b) return (false, 0);
        return (true, c);
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a / b);
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        if (b == 0) return (false, 0);
        return (true, a % b);
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");
        return c;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a, "SafeMath: subtraction overflow");
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) return 0;
        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");
        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: division by zero");
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b > 0, "SafeMath: modulo by zero");
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        return a - b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryDiv}.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        return a % b;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <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);
            }
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <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 GSN 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 payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    /**
     * @dev Converts a `uint256` to its ASCII `string` 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);
        uint256 index = digits - 1;
        temp = value;
        while (temp != 0) {
            buffer[index--] = bytes1(uint8(48 + temp % 10));
            temp /= 10;
        }
        return string(buffer);
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <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 () internal {
        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;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./Context.sol";

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor () internal {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721Metadata.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721Enumerable.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
import "@openzeppelin/contracts/introspection/ERC165.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/EnumerableSet.sol";
import "@openzeppelin/contracts/utils/EnumerableMap.sol";
import "@openzeppelin/contracts/utils/Strings.sol";

/**
 * @title ERC721 Non-Fungible Token Standard basic implementation
 * @dev see https://eips.ethereum.org/EIPS/eip-721
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Enumerable {
    using SafeMath for uint256;
    using Address for address;
    using EnumerableSet for EnumerableSet.UintSet;
    using EnumerableMap for EnumerableMap.UintToAddressMap;
    using Strings for uint256;

    // Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
    // which can be also obtained as `IERC721Receiver(0).onERC721Received.selector`
    bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;

    // Mapping from holder address to their (enumerable) set of owned tokens
    mapping (address => EnumerableSet.UintSet) private _holderTokens;

    // Enumerable mapping from token ids to their owners
    EnumerableMap.UintToAddressMap private _tokenOwners;

    // 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;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

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

    // Base URI
    string private _baseURI;

    /*
     *     bytes4(keccak256('balanceOf(address)')) == 0x70a08231
     *     bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e
     *     bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3
     *     bytes4(keccak256('getApproved(uint256)')) == 0x081812fc
     *     bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465
     *     bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c5
     *     bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e
     *     bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde
     *
     *     => 0x70a08231 ^ 0x6352211e ^ 0x095ea7b3 ^ 0x081812fc ^
     *        0xa22cb465 ^ 0xe985e9c5 ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd
     */
    bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;

    /*
     *     bytes4(keccak256('name()')) == 0x06fdde03
     *     bytes4(keccak256('symbol()')) == 0x95d89b41
     *     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd
     *
     *     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f
     */
    bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;

    /*
     *     bytes4(keccak256('totalSupply()')) == 0x18160ddd
     *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59
     *     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7
     *
     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63
     */
    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;

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

        // register the supported interfaces to conform to ERC721 via ERC165
        _registerInterface(_INTERFACE_ID_ERC721);
        _registerInterface(_INTERFACE_ID_ERC721_METADATA);
        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
    }

    /**
     * @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 _holderTokens[owner].length();
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        return _tokenOwners.get(tokenId, "ERC721: owner query for nonexistent token");
    }

    /**
     * @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 _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));
        }
        // If there is a baseURI but no tokenURI, concatenate the tokenID to the baseURI.
        return string(abi.encodePacked(base, tokenId.toString()));
    }

    /**
    * @dev Returns the base URI set via {_setBaseURI}. This will be
    * automatically added as a prefix in {tokenURI} to each token's URI, or
    * to the token ID if no specific URI is set for that token ID.
    */
    function baseURI() public view virtual returns (string memory) {
        return _baseURI;
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {
        return _holderTokens[owner].at(index);
    }

    /**
    * @dev Return an array of all tokens this
    * CUSTOM FUNCTION, NOT IN OPENZEPPELIN TEMPLATE
    */
    function tokensIdsByOwner(address owner) public view returns (uint256[] memory) {
        uint256[] memory tokens = new uint256[](_holderTokens[owner].length());
        for (uint i = 0; i < _holderTokens[owner].length(); i++) {
            tokens[i] = _holderTokens[owner].at(i);
        }
        return tokens;
    }

    /**
     * @dev See {IERC721Enumerable-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        // _tokenOwners are indexed by tokenIds, so .length() returns the number of tokenIds
        return _tokenOwners.length();
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index) public view virtual override returns (uint256) {
        (uint256 tokenId, ) = _tokenOwners.at(index);
        return tokenId;
    }

    /**
     * @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 _tokenOwners.contains(tokenId);
    }

    /**
     * @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:
     d*
     * - `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");
        // DIFFERENT FROM OPENZEPPELIN STANDARD
        // Calls `ERC721._exists` rather than `_exists`
        require(!ERC721._exists(tokenId), "ERC721: token already minted");

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

        _holderTokens[to].add(tokenId);

        _tokenOwners.set(tokenId, to);

        emit Transfer(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); // internal owner

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

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

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

        _holderTokens[owner].remove(tokenId);

        _tokenOwners.remove(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"); // internal 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);

        _holderTokens[from].remove(tokenId);
        _holderTokens[to].add(tokenId);

        _tokenOwners.set(tokenId, to);

        emit Transfer(from, to, 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), "ERC721Metadata: URI set of nonexistent token");
        _tokenURIs[tokenId] = _tokenURI;
    }

    /**
     * @dev Internal function to set the base URI for all token IDs. It is
     * automatically added as a prefix to the value returned in {tokenURI},
     * or to the token ID if {tokenURI} is empty.
     */
    function _setBaseURI(string memory baseURI_) internal virtual {
        _baseURI = baseURI_;
    }

    /**
     * @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()) {
            return true;
        }
        bytes memory returndata = to.functionCall(abi.encodeWithSelector(
            IERC721Receiver(to).onERC721Received.selector,
            _msgSender(),
            from,
            tokenId,
            _data
        ), "ERC721: transfer to non ERC721Receiver implementer");
        bytes4 retval = abi.decode(returndata, (bytes4));
        return (retval == _ERC721_RECEIVED);
    }

    /**
     * @dev Approve `to` to operate on `tokenId`
     *
     * Emits an {Approval} event.
     */
    function _approve(address to, uint256 tokenId) internal virtual {
        _tokenApprovals[tokenId] = to;
        // DIFFERENT FROM OPENZEPPELIN STANDARD
        // Calls `ownerOf` rather than `ERC721.ownerOf`
        emit Approval(ownerOf(tokenId), to, tokenId);
    }

    /**
     * @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 { }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Library for managing an enumerable variant of Solidity's
 * https://solidity.readthedocs.io/en/latest/types.html#mapping-types[`mapping`]
 * type.
 *
 * Maps have the following properties:
 *
 * - Entries are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Entries are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableMap for EnumerableMap.UintToAddressMap;
 *
 *     // Declare a set state variable
 *     EnumerableMap.UintToAddressMap private myMap;
 * }
 * ```
 *
 * As of v3.0.0, only maps of type `uint256 -> address` (`UintToAddressMap`) are
 * supported.
 */
library EnumerableMap {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Map type with
    // bytes32 keys and values.
    // The Map implementation uses private functions, and user-facing
    // implementations (such as Uint256ToAddressMap) are just wrappers around
    // the underlying Map.
    // This means that we can only create new EnumerableMaps for types that fit
    // in bytes32.

    struct MapEntry {
        bytes32 _key;
        bytes32 _value;
    }

    struct Map {
        // Storage of map keys and values
        MapEntry[] _entries;

        // Position of the entry defined by a key in the `entries` array, plus 1
        // because index 0 means a key is not in the map.
        mapping (bytes32 => uint256) _indexes;
    }

    /**
     * @dev Adds a key-value pair to a map, or updates the value for an existing
     * key. O(1).
     *
     * Returns true if the key was added to the map, that is if it was not
     * already present.
     */
    function _set(Map storage map, bytes32 key, bytes32 value) private returns (bool) {
        // We read and store the key's index to prevent multiple reads from the same storage slot
        uint256 keyIndex = map._indexes[key];

        if (keyIndex == 0) { // Equivalent to !contains(map, key)
            map._entries.push(MapEntry({ _key: key, _value: value }));
            // The entry is stored at length-1, but we add 1 to all indexes
            // and use 0 as a sentinel value
            map._indexes[key] = map._entries.length;
            return true;
        } else {
            map._entries[keyIndex - 1]._value = value;
            return false;
        }
    }

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

        if (keyIndex != 0) { // Equivalent to contains(map, key)
            // To delete a key-value pair from the _entries array in O(1), we swap the entry to delete with the last one
            // in the array, and then remove the last entry (sometimes called as 'swap and pop').
            // This modifies the order of the array, as noted in {at}.

            uint256 toDeleteIndex = keyIndex - 1;
            uint256 lastIndex = map._entries.length - 1;

            // When the entry to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            MapEntry storage lastEntry = map._entries[lastIndex];

            // Move the last entry to the index where the entry to delete is
            map._entries[toDeleteIndex] = lastEntry;
            // Update the index for the moved entry
            map._indexes[lastEntry._key] = toDeleteIndex + 1; // All indexes are 1-based

            // Delete the slot where the moved entry was stored
            map._entries.pop();

            // Delete the index for the deleted slot
            delete map._indexes[key];

            return true;
        } else {
            return false;
        }
    }

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

    /**
     * @dev Returns the number of key-value pairs in the map. O(1).
     */
    function _length(Map storage map) private view returns (uint256) {
        return map._entries.length;
    }

   /**
    * @dev Returns the key-value pair stored at position `index` in the map. O(1).
    *
    * Note that there are no guarantees on the ordering of entries inside the
    * array, and it may change when more entries are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function _at(Map storage map, uint256 index) private view returns (bytes32, bytes32) {
        require(map._entries.length > index, "EnumerableMap: index out of bounds");

        MapEntry storage entry = map._entries[index];
        return (entry._key, entry._value);
    }

    /**
     * @dev Tries to returns the value associated with `key`.  O(1).
     * Does not revert if `key` is not in the map.
     */
    function _tryGet(Map storage map, bytes32 key) private view returns (bool, bytes32) {
        uint256 keyIndex = map._indexes[key];
        if (keyIndex == 0) return (false, 0); // Equivalent to contains(map, key)
        return (true, map._entries[keyIndex - 1]._value); // All indexes are 1-based
    }

    /**
     * @dev Returns the value associated with `key`.  O(1).
     *
     * Requirements:
     *
     * - `key` must be in the map.
     */
    function _get(Map storage map, bytes32 key) private view returns (bytes32) {
        uint256 keyIndex = map._indexes[key];
        require(keyIndex != 0, "EnumerableMap: nonexistent key"); // Equivalent to contains(map, key)
        return map._entries[keyIndex - 1]._value; // All indexes are 1-based
    }

    /**
     * @dev Same as {_get}, with a custom error message when `key` is not in the map.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {_tryGet}.
     */
    function _get(Map storage map, bytes32 key, string memory errorMessage) private view returns (bytes32) {
        uint256 keyIndex = map._indexes[key];
        require(keyIndex != 0, errorMessage); // Equivalent to contains(map, key)
        return map._entries[keyIndex - 1]._value; // All indexes are 1-based
    }

    // UintToAddressMap

    struct UintToAddressMap {
        Map _inner;
    }

    /**
     * @dev Adds a key-value pair to a map, or updates the value for an existing
     * key. O(1).
     *
     * Returns true if the key was added to the map, that is if it was not
     * already present.
     */
    function set(UintToAddressMap storage map, uint256 key, address value) internal returns (bool) {
        return _set(map._inner, bytes32(key), bytes32(uint256(uint160(value))));
    }

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

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

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

   /**
    * @dev Returns the element stored at position `index` in the set. O(1).
    * Note that there are no guarantees on the ordering of values inside the
    * array, and it may change when more values are added or removed.
    *
    * Requirements:
    *
    * - `index` must be strictly less than {length}.
    */
    function at(UintToAddressMap storage map, uint256 index) internal view returns (uint256, address) {
        (bytes32 key, bytes32 value) = _at(map._inner, index);
        return (uint256(key), address(uint160(uint256(value))));
    }

    /**
     * @dev Tries to returns the value associated with `key`.  O(1).
     * Does not revert if `key` is not in the map.
     *
     * _Available since v3.4._
     */
    function tryGet(UintToAddressMap storage map, uint256 key) internal view returns (bool, address) {
        (bool success, bytes32 value) = _tryGet(map._inner, bytes32(key));
        return (success, address(uint160(uint256(value))));
    }

    /**
     * @dev Returns the value associated with `key`.  O(1).
     *
     * Requirements:
     *
     * - `key` must be in the map.
     */
    function get(UintToAddressMap storage map, uint256 key) internal view returns (address) {
        return address(uint160(uint256(_get(map._inner, bytes32(key)))));
    }

    /**
     * @dev Same as {get}, with a custom error message when `key` is not in the map.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryGet}.
     */
    function get(UintToAddressMap storage map, uint256 key, string memory errorMessage) internal view returns (address) {
        return address(uint160(uint256(_get(map._inner, bytes32(key), errorMessage))));
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Library for managing
 * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
 * types.
 *
 * Sets have the following properties:
 *
 * - Elements are added, removed, and checked for existence in constant time
 * (O(1)).
 * - Elements are enumerated in O(n). No guarantees are made on the ordering.
 *
 * ```
 * contract Example {
 *     // Add the library methods
 *     using EnumerableSet for EnumerableSet.AddressSet;
 *
 *     // Declare a set state variable
 *     EnumerableSet.AddressSet private mySet;
 * }
 * ```
 *
 * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
 * and `uint256` (`UintSet`) are supported.
 */
library EnumerableSet {
    // To implement this library for multiple types with as little code
    // repetition as possible, we write it in terms of a generic Set type with
    // bytes32 values.
    // The Set implementation uses private functions, and user-facing
    // implementations (such as AddressSet) are just wrappers around the
    // underlying Set.
    // This means that we can only create new EnumerableSets for types that fit
    // in bytes32.

    struct Set {
        // Storage of set values
        bytes32[] _values;

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

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

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

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

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

            // When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs
            // so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.

            bytes32 lastvalue = set._values[lastIndex];

            // Move the last value to the index where the value to delete is
            set._values[toDeleteIndex] = lastvalue;
            // Update the index for the moved value
            set._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based

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

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

            return true;
        } else {
            return false;
        }
    }

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

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

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

    // Bytes32Set

    struct Bytes32Set {
        Set _inner;
    }

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

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

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

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

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

    // AddressSet

    struct AddressSet {
        Set _inner;
    }

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

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

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

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

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


    // UintSet

    struct UintSet {
        Set _inner;
    }

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

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

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

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

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

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts may inherit from this and call {_registerInterface} to declare
 * their support of an interface.
 */
abstract contract ERC165 is IERC165 {
    /*
     * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
     */
    bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;

    /**
     * @dev Mapping of interface ids to whether or not it's supported.
     */
    mapping(bytes4 => bool) private _supportedInterfaces;

    constructor () internal {
        // Derived contracts need only register support for their own interfaces,
        // we register support for ERC165 itself here
        _registerInterface(_INTERFACE_ID_ERC165);
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     *
     * Time complexity O(1), guaranteed to always use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return _supportedInterfaces[interfaceId];
    }

    /**
     * @dev Registers the contract as an implementer of the interface defined by
     * `interfaceId`. Support of the actual ERC165 interface is automatic and
     * registering its interface id is not required.
     *
     * See {IERC165-supportsInterface}.
     *
     * Requirements:
     *
     * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
     */
    function _registerInterface(bytes4 interfaceId) internal virtual {
        require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
        _supportedInterfaces[interfaceId] = true;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

import "../../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

pragma solidity >=0.6.0 <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

pragma solidity >=0.6.0 <0.8.0;

import "./IERC721Receiver.sol";

  /**
   * @dev Implementation of the {IERC721Receiver} interface.
   *
   * Accepts all token transfers. 
   * Make sure the contract is able to use its token with {IERC721-safeTransferFrom}, {IERC721-approve} or {IERC721-setApprovalForAll}.
   */
contract ERC721Holder is IERC721Receiver {

    /**
     * @dev See {IERC721Receiver-onERC721Received}.
     *
     * Always returns `IERC721Receiver.onERC721Received.selector`.
     */
    function onERC721Received(address, address, uint256, bytes memory) public virtual override returns (bytes4) {
        return this.onERC721Received.selector;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <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

pragma solidity >=0.6.0 <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

pragma solidity >=0.6.2 <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);
}