// File: contracts/MoxieMarketplace.sol



// SPDX-License-Identifier: MIT

pragma solidity 0.6.12;

import "@openzeppelin/contracts/introspection/IERC165.sol";
import "@openzeppelin/contracts/token/ERC1155/IERC1155.sol";
import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
// import "@openzeppelin/contracts-upgradeable/utils/AddressUpgradeable.sol";
// import "@openzeppelin/contracts-upgradeable/utils/ReentrancyGuardUpgradeable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";

interface IMoxieAddressRegistry {
    function moxie() external view returns (address);

    function bundleMarketplace() external view returns (address);

    function auction() external view returns (address);

    function factory() external view returns (address);

    function privateFactory() external view returns (address);

    function artFactory() external view returns (address);

    function privateArtFactory() external view returns (address);

    function tokenRegistry() external view returns (address);

    function priceFeed() external view returns (address);
}

interface IMoxieAuction {
    function auctions(address, uint256)
        external
        view
        returns (
            address,
            address,
            uint256,
            uint256,
            uint256,
            bool
        );
}

interface IMoxieBundleMarketplace {
    function validateItemSold(
        address,
        uint256,
        uint256
    ) external;
}

interface IMoxieNFTFactory {
    function exists(address) external view returns (bool);
}

interface IMoxieTokenRegistry {
    function enabled(address) external view returns (bool);
}

interface IMoxiePriceFeed {
    function wETH() external view returns (address);

    function getPrice(address) external view returns (int256, uint8);
}

contract MoxieMarketplace is Ownable, ReentrancyGuard {
    using SafeMath for uint256;
    // using AddressUpgradeable for address payable;
    using SafeERC20 for IERC20;

    /// @notice Events for the contract
    event ItemListed(
        address indexed owner,
        address indexed nft,
        uint256 tokenId,
        uint256 quantity,
        address payToken,
        uint256 pricePerItem,
        uint256 startingTime
    );
    event ItemSold(
        address indexed seller,
        address indexed buyer,
        address indexed nft,
        uint256 tokenId,
        uint256 quantity,
        address payToken,
        int256 unitPrice,
        uint256 pricePerItem
    );
    event ItemUpdated(
        address indexed owner,
        address indexed nft,
        uint256 tokenId,
        address payToken,
        uint256 newPrice
    );
    event ItemCanceled(
        address indexed owner,
        address indexed nft,
        uint256 tokenId
    );
    event OfferCreated(
        address indexed creator,
        address indexed nft,
        uint256 tokenId,
        uint256 quantity,
        address payToken,
        uint256 pricePerItem,
        uint256 deadline
    );
    event OfferCanceled(
        address indexed creator,
        address indexed nft,
        uint256 tokenId
    );
    event UpdatePlatformFee(uint16 platformFee);
    event UpdatePlatformFeeRecipient(address payable platformFeeRecipient);

    /// @notice Structure for listed items
    struct Listing {
        uint256 quantity;
        address payToken;
        uint256 pricePerItem;
        uint256 startingTime;
    }

    /// @notice Structure for offer
    struct Offer {
        IERC20 payToken;
        uint256 quantity;
        uint256 pricePerItem;
        uint256 deadline;
    }

    struct CollectionRoyalty {
        uint16 royalty;
        address creator;
        address feeRecipient;
    }

    bytes4 private constant INTERFACE_ID_ERC721 = 0x80ac58cd;
    bytes4 private constant INTERFACE_ID_ERC1155 = 0xd9b67a26;

    /// @notice NftAddress -> Token ID -> Minter
    mapping(address => mapping(uint256 => address)) public minters;

    /// @notice NftAddress -> Token ID -> Royalty
    mapping(address => mapping(uint256 => uint16)) public royalties;

    /// @notice NftAddress -> Token ID -> Owner -> Listing item
    mapping(address => mapping(uint256 => mapping(address => Listing)))
        public listings;

    /// @notice NftAddress -> Token ID -> Offerer -> Offer
    mapping(address => mapping(uint256 => mapping(address => Offer)))
        public offers;

    /// @notice Platform fee
    uint16 public platformFee;

    /// @notice Platform fee receipient
    address payable public feeReceipient;

    /// @notice NftAddress -> Royalty
    mapping(address => CollectionRoyalty) public collectionRoyalties;

    /// @notice Address registry
    IMoxieAddressRegistry public addressRegistry;

    modifier onlyMarketplace() {
        require(
            address(addressRegistry.bundleMarketplace()) == _msgSender(),
            "sender must be bundle marketplace"
        );
        _;
    }

    modifier isListed(
        address _nftAddress,
        uint256 _tokenId,
        address _owner
    ) {
        Listing memory listing = listings[_nftAddress][_tokenId][_owner];
        require(listing.quantity > 0, "not listed item");
        _;
    }

    modifier notListed(
        address _nftAddress,
        uint256 _tokenId,
        address _owner
    ) {
        Listing memory listing = listings[_nftAddress][_tokenId][_owner];
        require(listing.quantity == 0, "already listed");
        _;
    }

    modifier validListing(
        address _nftAddress,
        uint256 _tokenId,
        address _owner
    ) {
        Listing memory listedItem = listings[_nftAddress][_tokenId][_owner];

        _validOwner(_nftAddress, _tokenId, _owner, listedItem.quantity);

        require(_getNow() >= listedItem.startingTime, "item not buyable");
        _;
    }

    modifier offerExists(
        address _nftAddress,
        uint256 _tokenId,
        address _creator
    ) {
        Offer memory offer = offers[_nftAddress][_tokenId][_creator];
        require(
            offer.quantity > 0 && offer.deadline > _getNow(),
            "offer not exists or expired"
        );
        _;
    }

    modifier offerNotExists(
        address _nftAddress,
        uint256 _tokenId,
        address _creator
    ) {
        Offer memory offer = offers[_nftAddress][_tokenId][_creator];
        require(
            offer.quantity == 0 || offer.deadline <= _getNow(),
            "offer already created"
        );
        _;
    }

    /// @notice Contract initializer
    function initialize(address payable _feeRecipient, uint16 _platformFee)
        public
    // initializer
    {
        platformFee = _platformFee;
        feeReceipient = _feeRecipient;

        // __Ownable_init();
        // __ReentrancyGuard_init();
    }

    /// @notice Method for listing NFT
    /// @param _nftAddress Address of NFT contract
    /// @param _tokenId Token ID of NFT
    /// @param _quantity token amount to list (needed for ERC-1155 NFTs, set as 1 for ERC-721)
    /// @param _payToken Paying token
    /// @param _pricePerItem sale price for each iteam
    /// @param _startingTime scheduling for a future sale
    function listItem(
        address _nftAddress,
        uint256 _tokenId,
        uint256 _quantity,
        address _payToken,
        uint256 _pricePerItem,
        uint256 _startingTime
    ) external notListed(_nftAddress, _tokenId, _msgSender()) {
        if (IERC165(_nftAddress).supportsInterface(INTERFACE_ID_ERC721)) {
            IERC721 nft = IERC721(_nftAddress);
            require(nft.ownerOf(_tokenId) == _msgSender(), "not owning item");
            require(
                nft.isApprovedForAll(_msgSender(), address(this)),
                "item not approved"
            );
        } else if (
            IERC165(_nftAddress).supportsInterface(INTERFACE_ID_ERC1155)
        ) {
            IERC1155 nft = IERC1155(_nftAddress);
            require(
                nft.balanceOf(_msgSender(), _tokenId) >= _quantity,
                "must hold enough nfts"
            );
            require(
                nft.isApprovedForAll(_msgSender(), address(this)),
                "item not approved"
            );
        } else {
            revert("invalid nft address");
        }

        _validPayToken(_payToken);

        listings[_nftAddress][_tokenId][_msgSender()] = Listing(
            _quantity,
            _payToken,
            _pricePerItem,
            _startingTime
        );
        emit ItemListed(
            _msgSender(),
            _nftAddress,
            _tokenId,
            _quantity,
            _payToken,
            _pricePerItem,
            _startingTime
        );
    }

    /// @notice Method for canceling listed NFT
    function cancelListing(address _nftAddress, uint256 _tokenId)
        external
        nonReentrant
        isListed(_nftAddress, _tokenId, _msgSender())
    {
        _cancelListing(_nftAddress, _tokenId, _msgSender());
    }

    /// @notice Method for updating listed NFT
    /// @param _nftAddress Address of NFT contract
    /// @param _tokenId Token ID of NFT
    /// @param _payToken payment token
    /// @param _newPrice New sale price for each iteam
    function updateListing(
        address _nftAddress,
        uint256 _tokenId,
        address _payToken,
        uint256 _newPrice
    ) external nonReentrant isListed(_nftAddress, _tokenId, _msgSender()) {
        Listing storage listedItem = listings[_nftAddress][_tokenId][
            _msgSender()
        ];

        _validOwner(_nftAddress, _tokenId, _msgSender(), listedItem.quantity);

        _validPayToken(_payToken);

        listedItem.payToken = _payToken;
        listedItem.pricePerItem = _newPrice;
        emit ItemUpdated(
            _msgSender(),
            _nftAddress,
            _tokenId,
            _payToken,
            _newPrice
        );
    }

    /// @notice Method for buying listed NFT
    /// @param _nftAddress NFT contract address
    /// @param _tokenId TokenId
    function buyItem(
        address _nftAddress,
        uint256 _tokenId,
        address _payToken,
        address _owner
    )
        external
        nonReentrant
        isListed(_nftAddress, _tokenId, _owner)
        validListing(_nftAddress, _tokenId, _owner)
    {
        Listing memory listedItem = listings[_nftAddress][_tokenId][_owner];
        require(listedItem.payToken == _payToken, "invalid pay token");

        _buyItem(_nftAddress, _tokenId, _payToken, _owner);
    }

    function _buyItem(
        address _nftAddress,
        uint256 _tokenId,
        address _payToken,
        address _owner
    ) private {
        Listing memory listedItem = listings[_nftAddress][_tokenId][_owner];

        uint256 price = listedItem.pricePerItem.mul(listedItem.quantity);
        uint256 feeAmount = price.mul(platformFee).div(1e3);

        IERC20(_payToken).safeTransferFrom(
            _msgSender(),
            feeReceipient,
            feeAmount
        );

        address minter = minters[_nftAddress][_tokenId];
        uint16 royalty = royalties[_nftAddress][_tokenId];
        if (minter != address(0) && royalty != 0) {
            uint256 royaltyFee = price.sub(feeAmount).mul(royalty).div(10000);

            IERC20(_payToken).safeTransferFrom(
                _msgSender(),
                minter,
                royaltyFee
            );

            feeAmount = feeAmount.add(royaltyFee);
        } else {
            minter = collectionRoyalties[_nftAddress].feeRecipient;
            royalty = collectionRoyalties[_nftAddress].royalty;
            if (minter != address(0) && royalty != 0) {
                uint256 royaltyFee = price.sub(feeAmount).mul(royalty).div(
                    10000
                );

                IERC20(_payToken).safeTransferFrom(
                    _msgSender(),
                    minter,
                    royaltyFee
                );

                feeAmount = feeAmount.add(royaltyFee);
            }
        }

        IERC20(_payToken).safeTransferFrom(
            _msgSender(),
            _owner,
            price.sub(feeAmount)
        );

        // Transfer NFT to buyer
        if (IERC165(_nftAddress).supportsInterface(INTERFACE_ID_ERC721)) {
            IERC721(_nftAddress).safeTransferFrom(
                _owner,
                _msgSender(),
                _tokenId
            );
        } else {
            IERC1155(_nftAddress).safeTransferFrom(
                _owner,
                _msgSender(),
                _tokenId,
                listedItem.quantity,
                bytes("")
            );
        }
        IMoxieBundleMarketplace(addressRegistry.bundleMarketplace())
            .validateItemSold(_nftAddress, _tokenId, listedItem.quantity);

        emit ItemSold(
            _owner,
            _msgSender(),
            _nftAddress,
            _tokenId,
            listedItem.quantity,
            _payToken,
            getPrice(_payToken),
            price.div(listedItem.quantity)
        );
        delete (listings[_nftAddress][_tokenId][_owner]);
    }

    /// @notice Method for offering item
    /// @param _nftAddress NFT contract address
    /// @param _tokenId TokenId
    /// @param _payToken Paying token
    /// @param _quantity Quantity of items
    /// @param _pricePerItem Price per item
    /// @param _deadline Offer expiration
    function createOffer(
        address _nftAddress,
        uint256 _tokenId,
        IERC20 _payToken,
        uint256 _quantity,
        uint256 _pricePerItem,
        uint256 _deadline
    ) external offerNotExists(_nftAddress, _tokenId, _msgSender()) {
        require(
            IERC165(_nftAddress).supportsInterface(INTERFACE_ID_ERC721) ||
                IERC165(_nftAddress).supportsInterface(INTERFACE_ID_ERC1155),
            "invalid nft address"
        );

        IMoxieAuction auction = IMoxieAuction(addressRegistry.auction());

        (, , , uint256 startTime, , bool resulted) = auction.auctions(
            _nftAddress,
            _tokenId
        );

        require(
            startTime == 0 || resulted == true,
            "cannot place an offer if auction is going on"
        );

        require(_deadline > _getNow(), "invalid expiration");

        _validPayToken(address(_payToken));

        offers[_nftAddress][_tokenId][_msgSender()] = Offer(
            _payToken,
            _quantity,
            _pricePerItem,
            _deadline
        );

        emit OfferCreated(
            _msgSender(),
            _nftAddress,
            _tokenId,
            _quantity,
            address(_payToken),
            _pricePerItem,
            _deadline
        );
    }

    /// @notice Method for canceling the offer
    /// @param _nftAddress NFT contract address
    /// @param _tokenId TokenId
    function cancelOffer(address _nftAddress, uint256 _tokenId)
        external
        offerExists(_nftAddress, _tokenId, _msgSender())
    {
        delete (offers[_nftAddress][_tokenId][_msgSender()]);
        emit OfferCanceled(_msgSender(), _nftAddress, _tokenId);
    }

    /// @notice Method for accepting the offer
    /// @param _nftAddress NFT contract address
    /// @param _tokenId TokenId
    /// @param _creator Offer creator address
    function acceptOffer(
        address _nftAddress,
        uint256 _tokenId,
        address _creator
    ) external nonReentrant offerExists(_nftAddress, _tokenId, _creator) {
        Offer memory offer = offers[_nftAddress][_tokenId][_creator];

        _validOwner(_nftAddress, _tokenId, _msgSender(), offer.quantity);

        uint256 price = offer.pricePerItem.mul(offer.quantity);
        uint256 feeAmount = price.mul(platformFee).div(1e3);
        uint256 royaltyFee;

        offer.payToken.safeTransferFrom(_creator, feeReceipient, feeAmount);

        address minter = minters[_nftAddress][_tokenId];
        uint16 royalty = royalties[_nftAddress][_tokenId];

        if (minter != address(0) && royalty != 0) {
            royaltyFee = price.sub(feeAmount).mul(royalty).div(10000);
            offer.payToken.safeTransferFrom(_creator, minter, royaltyFee);
            feeAmount = feeAmount.add(royaltyFee);
        } else {
            minter = collectionRoyalties[_nftAddress].feeRecipient;
            royalty = collectionRoyalties[_nftAddress].royalty;
            if (minter != address(0) && royalty != 0) {
                royaltyFee = price.sub(feeAmount).mul(royalty).div(10000);
                offer.payToken.safeTransferFrom(_creator, minter, royaltyFee);
                feeAmount = feeAmount.add(royaltyFee);
            }
        }

        offer.payToken.safeTransferFrom(
            _creator,
            _msgSender(),
            price.sub(feeAmount)
        );

        // Transfer NFT to buyer
        if (IERC165(_nftAddress).supportsInterface(INTERFACE_ID_ERC721)) {
            IERC721(_nftAddress).safeTransferFrom(
                _msgSender(),
                _creator,
                _tokenId
            );
        } else {
            IERC1155(_nftAddress).safeTransferFrom(
                _msgSender(),
                _creator,
                _tokenId,
                offer.quantity,
                bytes("")
            );
        }
        IMoxieBundleMarketplace(addressRegistry.bundleMarketplace())
            .validateItemSold(_nftAddress, _tokenId, offer.quantity);

        emit ItemSold(
            _msgSender(),
            _creator,
            _nftAddress,
            _tokenId,
            offer.quantity,
            address(offer.payToken),
            getPrice(address(offer.payToken)),
            offer.pricePerItem
        );

        emit OfferCanceled(_creator, _nftAddress, _tokenId);

        delete (listings[_nftAddress][_tokenId][_msgSender()]);
        delete (offers[_nftAddress][_tokenId][_creator]);
    }

    /// @notice Method for setting royalty
    /// @param _nftAddress NFT contract address
    /// @param _tokenId TokenId
    /// @param _royalty Royalty
    function registerRoyalty(
        address _nftAddress,
        uint256 _tokenId,
        uint16 _royalty
    ) external {
        require(_royalty <= 10000, "invalid royalty");
        require(_isMoxieNFT(_nftAddress), "invalid nft address");

        _validOwner(_nftAddress, _tokenId, _msgSender(), 1);

        require(
            minters[_nftAddress][_tokenId] == address(0),
            "royalty already set"
        );
        minters[_nftAddress][_tokenId] = _msgSender();
        royalties[_nftAddress][_tokenId] = _royalty;
    }

    /// @notice Method for setting royalty
    /// @param _nftAddress NFT contract address
    /// @param _royalty Royalty
    function registerCollectionRoyalty(
        address _nftAddress,
        address _creator,
        uint16 _royalty,
        address _feeRecipient
    ) external onlyOwner {
        require(_creator != address(0), "invalid creator address");
        require(_royalty <= 10000, "invalid royalty");
        require(
            _royalty == 0 || _feeRecipient != address(0),
            "invalid fee recipient address"
        );
        require(!_isMoxieNFT(_nftAddress), "invalid nft address");

        if (collectionRoyalties[_nftAddress].creator == address(0)) {
            collectionRoyalties[_nftAddress] = CollectionRoyalty(
                _royalty,
                _creator,
                _feeRecipient
            );
        } else {
            CollectionRoyalty storage collectionRoyalty = collectionRoyalties[
                _nftAddress
            ];

            collectionRoyalty.royalty = _royalty;
            collectionRoyalty.feeRecipient = _feeRecipient;
            collectionRoyalty.creator = _creator;
        }
    }

    function _isMoxieNFT(address _nftAddress) internal view returns (bool) {
        return
            addressRegistry.moxie() == _nftAddress ||
            IMoxieNFTFactory(addressRegistry.factory()).exists(_nftAddress) ||
            IMoxieNFTFactory(addressRegistry.privateFactory()).exists(
                _nftAddress
            ) ||
            IMoxieNFTFactory(addressRegistry.artFactory()).exists(
                _nftAddress
            ) ||
            IMoxieNFTFactory(addressRegistry.privateArtFactory()).exists(
                _nftAddress
            );
    }

    /**
     @notice Method for getting price for pay token
     @param _payToken Paying token
     */
    function getPrice(address _payToken) public view returns (int256) {
        int256 unitPrice;
        uint8 decimals;
        IMoxiePriceFeed priceFeed = IMoxiePriceFeed(
            addressRegistry.priceFeed()
        );

        if (_payToken == address(0)) {
            (unitPrice, decimals) = priceFeed.getPrice(priceFeed.wETH());
        } else {
            (unitPrice, decimals) = priceFeed.getPrice(_payToken);
        }
        if (decimals < 18) {
            unitPrice = unitPrice * (int256(10)**(18 - decimals));
        } else {
            unitPrice = unitPrice / (int256(10)**(decimals - 18));
        }

        return unitPrice;
    }

    /**
     @notice Method for updating platform fee
     @dev Only admin
     @param _platformFee uint16 the platform fee to set
     */
    function updatePlatformFee(uint16 _platformFee) external onlyOwner {
        platformFee = _platformFee;
        emit UpdatePlatformFee(_platformFee);
    }

    /**
     @notice Method for updating platform fee address
     @dev Only admin
     @param _platformFeeRecipient payable address the address to sends the funds to
     */
    function updatePlatformFeeRecipient(address payable _platformFeeRecipient)
        external
        onlyOwner
    {
        feeReceipient = _platformFeeRecipient;
        emit UpdatePlatformFeeRecipient(_platformFeeRecipient);
    }

    /**
     @notice Update MoxieAddressRegistry contract
     @dev Only admin
     */
    function updateAddressRegistry(address _registry) external onlyOwner {
        addressRegistry = IMoxieAddressRegistry(_registry);
    }

    /**
     * @notice Validate and cancel listing
     * @dev Only bundle marketplace can access
     */
    function validateItemSold(
        address _nftAddress,
        uint256 _tokenId,
        address _seller,
        address _buyer
    ) external onlyMarketplace {
        Listing memory item = listings[_nftAddress][_tokenId][_seller];
        if (item.quantity > 0) {
            _cancelListing(_nftAddress, _tokenId, _seller);
        }
        delete (offers[_nftAddress][_tokenId][_buyer]);
        emit OfferCanceled(_buyer, _nftAddress, _tokenId);
    }

    ////////////////////////////
    /// Internal and Private ///
    ////////////////////////////

    function _getNow() internal view virtual returns (uint256) {
        return block.timestamp;
    }

    function _validPayToken(address _payToken) internal {
        require(
            _payToken == address(0) ||
                (addressRegistry.tokenRegistry() != address(0) &&
                    IMoxieTokenRegistry(addressRegistry.tokenRegistry())
                        .enabled(_payToken)),
            "invalid pay token"
        );
    }

    function _validOwner(
        address _nftAddress,
        uint256 _tokenId,
        address _owner,
        uint256 quantity
    ) internal {
        if (IERC165(_nftAddress).supportsInterface(INTERFACE_ID_ERC721)) {
            IERC721 nft = IERC721(_nftAddress);
            require(nft.ownerOf(_tokenId) == _owner, "not owning item");
        } else if (
            IERC165(_nftAddress).supportsInterface(INTERFACE_ID_ERC1155)
        ) {
            IERC1155 nft = IERC1155(_nftAddress);
            require(
                nft.balanceOf(_owner, _tokenId) >= quantity,
                "not owning item"
            );
        } else {
            revert("invalid nft address");
        }
    }

    function _cancelListing(
        address _nftAddress,
        uint256 _tokenId,
        address _owner
    ) private {
        Listing memory listedItem = listings[_nftAddress][_tokenId][_owner];

        _validOwner(_nftAddress, _tokenId, _owner, listedItem.quantity);

        delete (listings[_nftAddress][_tokenId][_owner]);
        emit ItemCanceled(_owner, _nftAddress, _tokenId);
    }
}

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



// 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);
}

// File: @openzeppelin/contracts/token/ERC1155/IERC1155.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

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

/**
 * @dev Required interface of an ERC1155 compliant contract, as defined in the
 * https://eips.ethereum.org/EIPS/eip-1155[EIP].
 *
 * _Available since v3.1._
 */
interface IERC1155 is IERC165 {
    /**
     * @dev Emitted when `value` tokens of token type `id` are transferred from `from` to `to` by `operator`.
     */
    event TransferSingle(address indexed operator, address indexed from, address indexed to, uint256 id, uint256 value);

    /**
     * @dev Equivalent to multiple {TransferSingle} events, where `operator`, `from` and `to` are the same for all
     * transfers.
     */
    event TransferBatch(address indexed operator, address indexed from, address indexed to, uint256[] ids, uint256[] values);

    /**
     * @dev Emitted when `account` grants or revokes permission to `operator` to transfer their tokens, according to
     * `approved`.
     */
    event ApprovalForAll(address indexed account, address indexed operator, bool approved);

    /**
     * @dev Emitted when the URI for token type `id` changes to `value`, if it is a non-programmatic URI.
     *
     * If an {URI} event was emitted for `id`, the standard
     * https://eips.ethereum.org/EIPS/eip-1155#metadata-extensions[guarantees] that `value` will equal the value
     * returned by {IERC1155MetadataURI-uri}.
     */
    event URI(string value, uint256 indexed id);

    /**
     * @dev Returns the amount of tokens of token type `id` owned by `account`.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function balanceOf(address account, uint256 id) external view returns (uint256);

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {balanceOf}.
     *
     * Requirements:
     *
     * - `accounts` and `ids` must have the same length.
     */
    function balanceOfBatch(address[] calldata accounts, uint256[] calldata ids) external view returns (uint256[] memory);

    /**
     * @dev Grants or revokes permission to `operator` to transfer the caller's tokens, according to `approved`,
     *
     * Emits an {ApprovalForAll} event.
     *
     * Requirements:
     *
     * - `operator` cannot be the caller.
     */
    function setApprovalForAll(address operator, bool approved) external;

    /**
     * @dev Returns true if `operator` is approved to transfer ``account``'s tokens.
     *
     * See {setApprovalForAll}.
     */
    function isApprovedForAll(address account, address operator) external view returns (bool);

    /**
     * @dev Transfers `amount` tokens of token type `id` from `from` to `to`.
     *
     * Emits a {TransferSingle} event.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - If the caller is not `from`, it must be have been approved to spend ``from``'s tokens via {setApprovalForAll}.
     * - `from` must have a balance of tokens of type `id` of at least `amount`.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155Received} and return the
     * acceptance magic value.
     */
    function safeTransferFrom(address from, address to, uint256 id, uint256 amount, bytes calldata data) external;

    /**
     * @dev xref:ROOT:erc1155.adoc#batch-operations[Batched] version of {safeTransferFrom}.
     *
     * Emits a {TransferBatch} event.
     *
     * Requirements:
     *
     * - `ids` and `amounts` must have the same length.
     * - If `to` refers to a smart contract, it must implement {IERC1155Receiver-onERC1155BatchReceived} and return the
     * acceptance magic value.
     */
    function safeBatchTransferFrom(address from, address to, uint256[] calldata ids, uint256[] calldata amounts, bytes calldata data) external;
}

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



// 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;
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `recipient`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `sender` to `recipient` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

// File: @openzeppelin/contracts/token/ERC20/SafeERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "./IERC20.sol";
import "../../math/SafeMath.sol";
import "../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// File: @openzeppelin/contracts/math/SafeMath.sol



// 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;
    }
}

// File: @openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../utils/ContextUpgradeable.sol";
import "../proxy/Initializable.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 OwnableUpgradeable is Initializable, ContextUpgradeable {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    function __Ownable_init() internal initializer {
        __Context_init_unchained();
        __Ownable_init_unchained();
    }

    function __Ownable_init_unchained() internal initializer {
        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;
    }
    uint256[49] private __gap;
}

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



// 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;
    }
}

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



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

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

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

    uint256 private _status;

    constructor () internal {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

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

        _;

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

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



// 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);
            }
        }
    }
}

// File: @openzeppelin/contracts-upgradeable/utils/ContextUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;
import "../proxy/Initializable.sol";

/*
 * @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 ContextUpgradeable is Initializable {
    function __Context_init() internal initializer {
        __Context_init_unchained();
    }

    function __Context_init_unchained() internal initializer {
    }
    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;
    }
    uint256[50] private __gap;
}

// File: @openzeppelin/contracts-upgradeable/proxy/Initializable.sol



// SPDX-License-Identifier: MIT

// solhint-disable-next-line compiler-version
pragma solidity >=0.4.24 <0.8.0;

import "../utils/AddressUpgradeable.sol";

/**
 * @dev This is a base contract to aid in writing upgradeable contracts, or any kind of contract that will be deployed
 * behind a proxy. Since a proxied contract can't have a constructor, it's common to move constructor logic to an
 * external initializer function, usually called `initialize`. It then becomes necessary to protect this initializer
 * function so it can only be called once. The {initializer} modifier provided by this contract will have this effect.
 *
 * TIP: To avoid leaving the proxy in an uninitialized state, the initializer function should be called as early as
 * possible by providing the encoded function call as the `_data` argument to {UpgradeableProxy-constructor}.
 *
 * CAUTION: When used with inheritance, manual care must be taken to not invoke a parent initializer twice, or to ensure
 * that all initializers are idempotent. This is not verified automatically as constructors are by Solidity.
 */
abstract contract Initializable {

    /**
     * @dev Indicates that the contract has been initialized.
     */
    bool private _initialized;

    /**
     * @dev Indicates that the contract is in the process of being initialized.
     */
    bool private _initializing;

    /**
     * @dev Modifier to protect an initializer function from being invoked twice.
     */
    modifier initializer() {
        require(_initializing || _isConstructor() || !_initialized, "Initializable: contract is already initialized");

        bool isTopLevelCall = !_initializing;
        if (isTopLevelCall) {
            _initializing = true;
            _initialized = true;
        }

        _;

        if (isTopLevelCall) {
            _initializing = false;
        }
    }

    /// @dev Returns true if and only if the function is running in the constructor
    function _isConstructor() private view returns (bool) {
        return !AddressUpgradeable.isContract(address(this));
    }
}

// File: @openzeppelin/contracts-upgradeable/utils/AddressUpgradeable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library AddressUpgradeable {
    /**
     * @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);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

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

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



// 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;
    }
}