/**
 *Submitted for verification at Etherscan.io on 2021-09-14
*/

// Sources flattened with hardhat v2.6.4 https://hardhat.org

// File @openzeppelin/contracts/utils/introspection/IERC165.sol@v4.3.1

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}


// File @openzeppelin/contracts/token/ERC721/IERC721.sol@v4.3.1


pragma solidity ^0.8.0;

/**
 * @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/ERC721/IERC721Receiver.sol@v4.3.1


pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}


// File @openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol@v4.3.1


pragma solidity ^0.8.0;

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {
    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the token collection symbol.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}


// File @openzeppelin/contracts/utils/Address.sol@v4.3.1


pragma solidity ^0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        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");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}


// File @openzeppelin/contracts/utils/Context.sol@v4.3.1


pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}


// File @openzeppelin/contracts/utils/Strings.sol@v4.3.1


pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }
}


// File @openzeppelin/contracts/utils/introspection/ERC165.sol@v4.3.1


pragma solidity ^0.8.0;

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}


// File @openzeppelin/contracts/token/ERC721/ERC721.sol@v4.3.1


pragma solidity ^0.8.0;







/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    using Address for address;
    using Strings for uint256;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Mapping from token ID to owner address
    mapping(uint256 => address) private _owners;

    // Mapping owner address to token count
    mapping(address => uint256) private _balances;

    // Mapping from token ID to approved address
    mapping(uint256 => address) private _tokenApprovals;

    // Mapping from owner to operator approvals
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return
            interfaceId == type(IERC721).interfaceId ||
            interfaceId == type(IERC721Metadata).interfaceId ||
            super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");
        return _balances[owner];
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _owners[tokenId];
        require(owner != address(0), "ERC721: owner query for nonexistent token");
        return owner;
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");

        string memory baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
    }

    /**
     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
     * by default, can be overriden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not owner nor approved for all"
        );

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

    /**
     * @dev See {IERC721-setApprovalForAll}.
     */
    function setApprovalForAll(address operator, bool approved) public virtual override {
        require(operator != _msgSender(), "ERC721: approve to caller");

        _operatorApprovals[_msgSender()][operator] = approved;
        emit ApprovalForAll(_msgSender(), operator, approved);
    }

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _transfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) public virtual override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");
        _safeTransfer(from, to, tokenId, _data);
    }

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * `_data` is additional data, it has no specified format and it is sent in call to `to`.
     *
     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
     * implement alternative mechanisms to perform token transfer, such as signature-based.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeTransfer(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns whether `tokenId` exists.
     *
     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
     *
     * Tokens start existing when they are minted (`_mint`),
     * and stop existing when they are burned (`_burn`).
     */
    function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _owners[tokenId] != address(0);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        require(_exists(tokenId), "ERC721: operator query for nonexistent token");
        address owner = ERC721.ownerOf(tokenId);
        return (spender == owner || getApproved(tokenId) == spender || isApprovedForAll(owner, spender));
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
     */
    function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory _data
    ) internal virtual {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, _data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Transfer} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _beforeTokenTransfer(address(0), to, tokenId);

        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(address(0), to, tokenId);
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId);

        _beforeTokenTransfer(owner, address(0), tokenId);

        // Clear approvals
        _approve(address(0), tokenId);

        _balances[owner] -= 1;
        delete _owners[tokenId];

        emit Transfer(owner, address(0), tokenId);
    }

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer of token that is not own");
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId);

        // Clear approvals from the previous owner
        _approve(address(0), tokenId);

        _balances[from] -= 1;
        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(from, to, tokenId);
    }

    /**
     * @dev Approve `to` to operate on `tokenId`
     *
     * Emits a {Approval} event.
     */
    function _approve(address to, uint256 tokenId) internal virtual {
        _tokenApprovals[tokenId] = to;
        emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param _data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory _data
    ) private returns (bool) {
        if (to.isContract()) {
            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data) returns (bytes4 retval) {
                return retval == IERC721Receiver.onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert("ERC721: transfer to non ERC721Receiver implementer");
                } else {
                    assembly {
                        revert(add(32, reason), mload(reason))
                    }
                }
            }
        } else {
            return true;
        }
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}
}


// File @openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol@v4.3.1


pragma solidity ^0.8.0;

/**
 * @dev ERC721 token with storage based token URI management.
 */
abstract contract ERC721URIStorage is ERC721 {
    using Strings for uint256;

    // Optional mapping for token URIs
    mapping(uint256 => string) private _tokenURIs;

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721URIStorage: URI query for nonexistent token");

        string memory _tokenURI = _tokenURIs[tokenId];
        string memory base = _baseURI();

        // If there is no base URI, return the token URI.
        if (bytes(base).length == 0) {
            return _tokenURI;
        }
        // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
        if (bytes(_tokenURI).length > 0) {
            return string(abi.encodePacked(base, _tokenURI));
        }

        return super.tokenURI(tokenId);
    }

    /**
     * @dev Sets `_tokenURI` as the tokenURI of `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
        require(_exists(tokenId), "ERC721URIStorage: URI set of nonexistent token");
        _tokenURIs[tokenId] = _tokenURI;
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual override {
        super._burn(tokenId);

        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }
    }
}


// File contracts/Libraries.sol

pragma solidity ^0.8.0;

/// @title Base64
/// @notice Provides a function for encoding some bytes in base64
/// @author Brecht Devos <brecht@loopring.org>
library Base64 {
    bytes internal constant TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    /// @notice Encodes some bytes to the base64 representation
    function encode(bytes memory data) internal pure returns (string memory) {
        uint256 len = data.length;
        if (len == 0) return "";

        // multiply by 4/3 rounded up
        uint256 encodedLen = 4 * ((len + 2) / 3);

        // Add some extra buffer at the end
        bytes memory result = new bytes(encodedLen + 32);

        bytes memory table = TABLE;

        assembly {
            let tablePtr := add(table, 1)
            let resultPtr := add(result, 32)

            for {
                let i := 0
            } lt(i, len) {

            } {
                i := add(i, 3)
                let input := and(mload(add(data, i)), 0xffffff)

                let out := mload(add(tablePtr, and(shr(18, input), 0x3F)))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(shr(12, input), 0x3F))), 0xFF))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(shr(6, input), 0x3F))), 0xFF))
                out := shl(8, out)
                out := add(out, and(mload(add(tablePtr, and(input, 0x3F))), 0xFF))
                out := shl(224, out)

                mstore(resultPtr, out)

                resultPtr := add(resultPtr, 4)
            }

            switch mod(len, 3)
            case 1 {
                mstore(sub(resultPtr, 2), shl(240, 0x3d3d))
            }
            case 2 {
                mstore(sub(resultPtr, 1), shl(248, 0x3d))
            }

            mstore(result, encodedLen)
        }

        return string(result);
    }
}

library Stringify {
  function toString(uint256 value) internal pure returns (string memory) {
    // Inspired by OraclizeAPI's implementation - MIT license
    // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol
    if (value == 0) {
        return "0";
    }
    uint256 temp = value;
    uint256 digits;
    while (temp != 0) {
        digits++;
        temp /= 10;
    }
    bytes memory buffer = new bytes(digits);
    while (value != 0) {
        digits -= 1;
        buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
        value /= 10;
    }
    return string(buffer);
  }

  function toString(address x) internal pure returns (string memory) {
    bytes memory s = new bytes(40);
    for (uint i = 0; i < 20; i++) {
        bytes1 b = bytes1(uint8(uint(uint160(x)) / (2**(8*(19 - i)))));
        bytes1 hi = bytes1(uint8(b) / 16);
        bytes1 lo = bytes1(uint8(b) - 16 * uint8(hi));
        s[2*i] = char(hi);
        s[2*i+1] = char(lo);
    }
    return string(abi.encodePacked('0x', string(s)));
 }

  function char(bytes1 b) internal pure returns (bytes1 c) {
      if (uint8(b) < 10) return bytes1(uint8(b) + 0x30);
      else return bytes1(uint8(b) + 0x57);
  }
}


// File contracts/PatronTokens.sol

pragma solidity ^0.8.0;



struct CollectionInfo {
  address addr;
  string name;
  string symbol;
  address patron;
}

struct Token {
  address collection;
  uint256 id;
}
contract PatronTokens is ERC721URIStorage {
  // Enumerable set of known tokens
  Token[] _registeredTokens;
  mapping(address => mapping (uint256 => bool)) _registeredTokensSet;

  // Enumerable set of known collections
  address[] _registeredCollections;
  mapping(address =>  bool) _registeredCollectionsSet;

  // Reference to the dt contract that controls this PatronTokens contract
  address public _dt;

  constructor(address dtAddr) ERC721("DoubleTrouble Patron Tokens", "PTRN") {
    _dt = dtAddr;
  }

  function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
    return interfaceId == 0xdeadbeef || super.supportsInterface(interfaceId);
  }

  function registeredTokens() external view returns (Token[] memory) {
    return _registeredTokens;
  }

  function totalSupply() external view returns (uint256) {
    return _registeredCollections.length;
  }

  function registerToken(address collection, uint256 tokenId) public {
    require(msg.sender == _dt, "Only the DoubleTrouble contract can call this");
    if (!_registeredTokensSet[collection][tokenId]) {
      _registeredTokensSet[collection][tokenId] = true;
      _registeredTokens.push(Token(collection, tokenId));
    }
  }

  function tryToClaimPatronToken(address collection, address receiverOfNft) public {
    require(msg.sender == _dt, "Only the DoubleTrouble contract can call this");

    if (!_registeredCollectionsSet[collection]) {
      _registeredCollectionsSet[collection] = true;
      _registeredCollections.push(collection);

      // We mint a brand new NFT if this is the first call for this collection
      _safeMint(receiverOfNft, _registeredCollections.length - 1);
    }
  }

  function patronTokenIdForCollection(address collection) public view returns (bool, uint256) {
    for (uint i = 0; i < _registeredCollections.length; i++) {
      if (collection == address(_registeredCollections[i])) {
        return (true, i);
      }
    }
    // Collection not found
    return (false, 0);
  }

  function patronOf(address collection) public view returns (address) {
    (bool found, uint256 tokenId) = patronTokenIdForCollection(collection);
    if (!found) {
      return address(0);
    }
    return ownerOf(tokenId);
  }

  function patronedCollection(uint256 tokenId) public view returns (address) {
    return _registeredCollections[tokenId];
  }

  function patronedCollectionInfo(uint256 tokenId) public view returns (CollectionInfo memory) {
    IERC721Metadata c = IERC721Metadata(_registeredCollections[tokenId]);
    return CollectionInfo(_registeredCollections[tokenId], c.name(), c.symbol(), ownerOf(tokenId));
  }

  function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
    require(tokenId < _registeredCollections.length, "tokenId not present");
    string memory collectionAddr = Stringify.toString(_registeredCollections[tokenId]);
    string memory strTokenId = Stringify.toString(tokenId);

    string[20] memory parts;
    uint256 lastPart = 0;
    parts[lastPart++] = '<svg xmlns="http://www.w3.org/2000/svg" preserveAspectRatio="xMinYMin meet" viewBox="0 0 400 400"><style>.base { fill: white; font-family: serif; font-size: 14px; }</style><rect width="100%" height="100%" fill="black" /><text x="10" y="20" class="base">';

    parts[lastPart++] = string(abi.encodePacked('PTRN #', strTokenId));
    parts[lastPart++] = '</text>';

    try IERC721Metadata(_registeredCollections[tokenId]).name() returns (string memory name) {
      parts[lastPart++] = '<text x="10" y="40" class="base">';
      parts[lastPart++] = name;
      parts[lastPart++] = '</text>';
    } catch (bytes memory /*lowLevelData*/) {
      // NOOP
    }

    try IERC721Metadata(_registeredCollections[tokenId]).symbol() returns (string memory symbol) {
      parts[lastPart++] = '<text x="10" y="60" class="base">';
      parts[lastPart++] = symbol;
      parts[lastPart++] = '</text>';
    } catch (bytes memory /*lowLevelData*/) {
      // NOOP
    }

    parts[lastPart++] = '<text x="10" y="80" class="base">';
    parts[lastPart++] = string(abi.encodePacked('Collection: ', collectionAddr));

    parts[lastPart++] = '</text></svg>';

    string memory output;
    for (uint256 i = 0; i < lastPart; i++) {
      output = string(abi.encodePacked(output, parts[i]));
    }

    string memory json = Base64.encode(bytes(string(abi.encodePacked('{"name": "PTRN #', strTokenId, '", "collection": "',
                                                                      collectionAddr, '", "description": "Whoever owns this PTRN token is the Patron for this collection. Patrons automatically get a % fee for any NFT from this collection sold within Double Trouble.", "image": "data:image/svg+xml;base64,',
                                                                      Base64.encode(bytes(output)), '"}'))));
    output = string(abi.encodePacked('data:application/json;base64,', json));

    return output;
  }
}


// File contracts/DoubleTrouble.sol

pragma solidity ^0.8.0;




struct TokenInfo {
   address collection;
   uint256 tokenId;
   uint256 lastPurchasePrice;
   uint256 forSalePrice;
   uint256 availableToWithdraw;
}

contract DoubleTrouble {
  // nested mapping that keeps track of who owns the NFTs
  mapping(address => mapping (uint256 => uint256)) _forSalePrices;
  mapping(address => mapping (uint256 => uint256)) _lastPurchasePrices;
  mapping(address => mapping (uint256 => uint256)) _lastPurchaseTimes;
  mapping(address => mapping (uint256 => address)) _owners;
  address _feeWallet;
  uint256 public _feeRate;
  uint256 public _daysForWithdraw;
  uint256 public _dtNumerator;
  uint256 public _dtDenominator;
  PatronTokens public _pt;

  event Buy(address oldOwner, address newOwner, address collection, uint256 tokenId, uint256 valueSent, uint256 amountPaid);
  event ForceBuy(address oldOwner, address newOwner, address collection, uint256 tokenId, uint256 valueSent, uint256 lastPurchasePrice, uint256 amountPaid);
  event SetPrice(address msgSender, address collection, uint256 tokenId, uint256 price);
  event Withdraw(address owner, address collection, uint256 tokenId, uint256 lastPurchasePrice);

  constructor(address ptdAddr, uint256 daysForWithdraw, uint256 dtNumerator, uint256 dtDenominator, uint256 feeRate,
              address feeWallet) {
    _feeWallet = feeWallet;
    _daysForWithdraw = daysForWithdraw;
    _dtNumerator = dtNumerator;
    _dtDenominator = dtDenominator;
    _feeRate = feeRate;
    _pt = PatronTokensDeployer(ptdAddr).deployIdempotently(address(this));
  }

  function patronTokensCollection() external view returns (address) {
    return address(_pt);
  }

  function forSalePrice(address collection, uint256 tokenId) external view returns (uint256) {
    return _forSalePrices[collection][tokenId];
  }

  function lastPurchasePrice(address collection, uint256 tokenId) external view returns (uint256) {
    return _lastPurchasePrices[collection][tokenId];
  }

  function lastPurchaseTime(address collection, uint256 tokenId) external view returns (uint256) {
    return _lastPurchaseTimes[collection][tokenId];
  }

  function availableToWithdraw(address collection, uint256 tokenId) external view returns (uint256) {
    return _lastPurchaseTimes[collection][tokenId] + (_daysForWithdraw * 1 days);
  }

  function secondsToWithdraw(address collection, uint256 tokenId) external view returns (int256) {
    // Allow uints to underflow per https://ethereum-blockchain-developer.com/010-solidity-basics/03-integer-overflow-underflow/
    unchecked {
      return int256(this.availableToWithdraw(collection, tokenId) - block.timestamp);
    }
  }

  function originalTokenURI(address collection, uint256 tokenId) external view returns (string memory) {
    return IERC721Metadata(collection).tokenURI(tokenId);
  }

  function ownerOf(address collection, uint256 tokenId) public view returns (address) {
    return _owners[collection][tokenId];
  }

  function setPrice(address collection, uint256 tokenId, uint256 price) external {
    _pt.registerToken(collection, tokenId);

    // Putting up for sale for the first time
    if (_lastPurchasePrices[collection][tokenId] == 0) {
      require(IERC721Metadata(collection).getApproved(tokenId) == msg.sender ||
              IERC721Metadata(collection).ownerOf(tokenId) == msg.sender, "msg.sender should be approved or owner of original NFT");
    // All times after
    } else {
      require(ownerOf(collection, tokenId) == msg.sender, "msg.sender should be owner of NFT");
    }
    _forSalePrices[collection][tokenId] = price;

    emit SetPrice(msg.sender, collection, tokenId, price);
  }

  function buy(address collection, uint256 tokenId) payable external {
    require(_forSalePrices[collection][tokenId] > 0, "NFT is not for sale");
    require(msg.value >= _forSalePrices[collection][tokenId], "Value sent must be at least the for sale price");
    _pt.registerToken(collection, tokenId);

    // Make NFT troublesome if this is the first time it's being purchased
    if (_owners[collection][tokenId] == address(0)) {
      require(IERC721Metadata(collection).getApproved(tokenId) == address(this), "DoubleTrouble contract must be approved to operate this token");

      // In the original collection, the owner becomes the DoubleTrouble contract
      address owner = IERC721Metadata(collection).ownerOf(tokenId);
      IERC721Metadata(collection).transferFrom(owner, address(this), tokenId);
      _owners[collection][tokenId] = owner;
    }

    emit Buy(_owners[collection][tokenId], msg.sender, collection, tokenId, msg.value, _forSalePrices[collection][tokenId]);
    _completeBuy(_owners[collection][tokenId], msg.sender, collection, tokenId, _forSalePrices[collection][tokenId]);
  }

  function forceBuy(address collection, uint256 tokenId) payable external {
    require(_lastPurchasePrices[collection][tokenId] > 0, "NFT was not yet purchased within DoubleTrouble");
    uint256 amountToPay = _dtNumerator * _lastPurchasePrices[collection][tokenId] / _dtDenominator;
    require(msg.value >= amountToPay, "Value sent must be at least twice the last purchase price");
    _pt.registerToken(collection, tokenId);

    emit ForceBuy(_owners[collection][tokenId], msg.sender, collection, tokenId, msg.value,
                  _lastPurchasePrices[collection][tokenId], amountToPay);
    _completeBuy(_owners[collection][tokenId], msg.sender, collection, tokenId, amountToPay);
  }

  function _completeBuy(address oldOwner, address newOwner, address collection, uint256 tokenId, uint256 amountToPay) internal virtual {
    require(_owners[collection][tokenId] == oldOwner, "old owner must match");

    // If this is the first time someone is buying an item from this collection, seller claims the patron token
    _pt.tryToClaimPatronToken(collection, oldOwner);

    // Change owner, set last purchase price, and remove from sale
    _owners[collection][tokenId] = newOwner;
    _lastPurchasePrices[collection][tokenId] = amountToPay;
    _lastPurchaseTimes[collection][tokenId] = block.timestamp;
    _forSalePrices[collection][tokenId] = 0;
    uint256 patronFee = amountToPay / _feeRate;

    // Send ether to the old owner. Must be at the very end of the buy function to prevent reentrancy attacks
    // https://consensys.net/diligence/blog/2019/09/stop-using-soliditys-transfer-now/
    uint256 amountSent = amountToPay - 2 * patronFee;
    (bool oldOwnersuccess, ) = oldOwner.call{value: amountSent}("");
    require(oldOwnersuccess, "Transfer to owner failed.");

    _sendFees(collection, patronFee, msg.value - amountSent);
  }

  function _sendFees(address collection, uint256 patronFee, uint256 valueLeft) internal virtual {
    // Send fee to patron of this troublesome Collection
    address patron = _pt.patronOf(collection);
    (bool patronSuccess, ) = patron.call{value: patronFee}("");

    // Send rest of the fee to the DT wallet
    uint256 rest = patronSuccess ? valueLeft - patronFee : valueLeft;
    (bool feeWalletSuccess, ) = _feeWallet.call{value: rest}("");
    require(feeWalletSuccess, "Transfer to DT wallet failed.");
  }

  function withdraw(address collection, uint256 tokenId) payable external {
    require(_owners[collection][tokenId] == msg.sender, "msg.sender should be owner of NFT");
    require(block.timestamp > this.availableToWithdraw(collection, tokenId), "NFT not yet available to withdraw from Double Trouble");
    require(msg.value >= _lastPurchasePrices[collection][tokenId] / _feeRate * 2, "Must pay fee to withdraw");

    uint256 pricePaid = _lastPurchasePrices[collection][tokenId];
    emit Withdraw(_owners[collection][tokenId], collection, tokenId, pricePaid);

    // Transfer original NFT back to owner, and burn troublesome NFT
    IERC721Metadata(collection).transferFrom(address(this), _owners[collection][tokenId], tokenId);

    // Reset DT state for token
    _owners[collection][tokenId] = address(0);
    _lastPurchasePrices[collection][tokenId] = 0;
    _forSalePrices[collection][tokenId] = 0;
    _lastPurchaseTimes[collection][tokenId] = 0;

    _sendFees(collection, pricePaid / _feeRate, msg.value);
  }

  function allKnownTokens() external view returns (TokenInfo[] memory) {
    Token[] memory knownTokens = _pt.registeredTokens();
    TokenInfo[] memory ret = new TokenInfo[](knownTokens.length);
    for (uint256 i = 0; i < knownTokens.length; i++) {
      Token memory t = knownTokens[i];
      ret[i] = TokenInfo(t.collection, t.id, _lastPurchasePrices[t.collection][t.id], _forSalePrices[t.collection][t.id],
                         _lastPurchaseTimes[t.collection][t.id] + (_daysForWithdraw * 1 days));
    }
    return ret;
  }
}

contract PatronTokensDeployer {
  mapping(address =>  PatronTokens) _deployed;

  function deployIdempotently(address dt) public returns (PatronTokens) {
    if (address(_deployed[dt]) == address(0)) {
      _deployed[dt] = new PatronTokens(dt);
    }
    return _deployed[dt];
  }
}