pragma solidity ^0.8.0;

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);
    }
}

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);
            }
        }
    }
}

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);
}

abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

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);
}

abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

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;
}

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);
}

interface IERC721Enumerable is IERC721 {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

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 {}
}

abstract contract ERC721Enumerable is ERC721, IERC721Enumerable {
    // Mapping from owner to list of owned token IDs
    mapping(address => mapping(uint256 => uint256)) private _ownedTokens;

    // Mapping from token ID to index of the owner tokens list
    mapping(uint256 => uint256) private _ownedTokensIndex;

    // Array with all token ids, used for enumeration
    uint256[] private _allTokens;

    // Mapping from token id to position in the allTokens array
    mapping(uint256 => uint256) private _allTokensIndex;

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC721) returns (bool) {
        return interfaceId == type(IERC721Enumerable).interfaceId || super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {
        require(index < ERC721.balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
        return _ownedTokens[owner][index];
    }

    /**
     * @dev See {IERC721Enumerable-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _allTokens.length;
    }

    /**
     * @dev See {IERC721Enumerable-tokenByIndex}.
     */
    function tokenByIndex(uint256 index) public view virtual override returns (uint256) {
        require(index < ERC721Enumerable.totalSupply(), "ERC721Enumerable: global index out of bounds");
        return _allTokens[index];
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting
     * and burning.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual override {
        super._beforeTokenTransfer(from, to, tokenId);

        if (from == address(0)) {
            _addTokenToAllTokensEnumeration(tokenId);
        } else if (from != to) {
            _removeTokenFromOwnerEnumeration(from, tokenId);
        }
        if (to == address(0)) {
            _removeTokenFromAllTokensEnumeration(tokenId);
        } else if (to != from) {
            _addTokenToOwnerEnumeration(to, tokenId);
        }
    }

    /**
     * @dev Private function to add a token to this extension's ownership-tracking data structures.
     * @param to address representing the new owner of the given token ID
     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
     */
    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
        uint256 length = ERC721.balanceOf(to);
        _ownedTokens[to][length] = tokenId;
        _ownedTokensIndex[tokenId] = length;
    }

    /**
     * @dev Private function to add a token to this extension's token tracking data structures.
     * @param tokenId uint256 ID of the token to be added to the tokens list
     */
    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
        _allTokensIndex[tokenId] = _allTokens.length;
        _allTokens.push(tokenId);
    }

    /**
     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
     * @param from address representing the previous owner of the given token ID
     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
     */
    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = ERC721.balanceOf(from) - 1;
        uint256 tokenIndex = _ownedTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary
        if (tokenIndex != lastTokenIndex) {
            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];

            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
        }

        // This also deletes the contents at the last position of the array
        delete _ownedTokensIndex[tokenId];
        delete _ownedTokens[from][lastTokenIndex];
    }

    /**
     * @dev Private function to remove a token from this extension's token tracking data structures.
     * This has O(1) time complexity, but alters the order of the _allTokens array.
     * @param tokenId uint256 ID of the token to be removed from the tokens list
     */
    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
        // then delete the last slot (swap and pop).

        uint256 lastTokenIndex = _allTokens.length - 1;
        uint256 tokenIndex = _allTokensIndex[tokenId];

        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
        uint256 lastTokenId = _allTokens[lastTokenIndex];

        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

        // This also deletes the contents at the last position of the array
        delete _allTokensIndex[tokenId];
        _allTokens.pop();
    }
}

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() {
        _setOwner(_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 {
        _setOwner(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");
        _setOwner(newOwner);
    }

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

interface IVersion {
    /**
     * @dev Returns version based on semantic versioning format.
     */
    function version() external pure returns (string memory);
}

contract FlexPaymentDivider is Ownable, IVersion {
    using Address for address payable;

    uint256 private _recipientCount;
    mapping(uint256 => address payable) private _recipientsById;
    mapping(address => uint256) private _percentagesByRecipient;
    mapping(address => uint256) private _balancesByRecipient;
    mapping(address => uint256) private _changeByRecipient;
    // 0 = false, 1 = true
    mapping(address => uint8) private _isWithdrawingByAccount;

    /**
     * @notice Sets recipients and the percentage of each deposit sent to them.
     * @dev {_setupRecipients} is only used once--here, upon deployment.
     * @param recipients_ Accounts to receive percentage of deposits.
     * @param percentages_ Percentage of deposit each account should receive.
     * Order matters.
     */
    constructor(
        address payable[] memory recipients_,
        uint256[] memory percentages_
    ) {
        _setupRecipients(recipients_, percentages_);
    }

    function version() external pure override returns (string memory) {
        return "1.0.0";
    }

    /**
     * @notice Returns the number of recipients each deposit is divided by.
     * @return Number of recipients.
     */
    function recipientCount() public view returns (uint256) {
        return _recipientCount;
    }

    /**
     * @notice Returns recipient with the given id.
     * @param id Integer.
     * @return Ethereum account address.
     */
    function recipientById(uint256 id) public view returns (address) {
        return _recipientsById[id];
    }

    /**
     * @notice Returns the percentage of each deposit the recipient receives.
     * @param recipient Ethereum account address.
     * @return Amount of 100.
     */
    function percentage(address recipient) public view returns (uint256) {
        return _percentagesByRecipient[recipient];
    }

    /**
     * @notice Returns the balance the recipient has accumulated.
     * @param recipient Ethereum account address.
     * @return Amount of wei.
     */
    function accumulatedBalance(address recipient) public view returns (uint256) {
        return _balancesByRecipient[recipient];
    }

    /**
     * @notice Returns the amount of change the recipient has accumulated.
     * @param recipient Ethereum account address.
     * @return Fraction of wei as an amount out of 100.
     */
    function accumulatedChange(address recipient) public view returns (uint256) {
        return _changeByRecipient[recipient];
    }

    /**
     * @notice Increases balance for each recipient by their designated
     * percenatage of the Ether sent with this call.
     * @custom:require Caller must be owner.
     * @custom:require Message value must be greater than 0.
     * @dev Solidity rounds towards zero so we accumulate change here that is
     * transferred once it exceeds a fractional amount of wei.
     *
     * @custom:warning
     * ===============
     * Forwarding all gas opens the door to reentrancy vulnerabilities. Make
     * sure you trust the recipient, or are either following the
     * checks-effects-interactions pattern or using {ReentrancyGuard}.
     */
    function deposit() public payable onlyOwner {
        require(
            msg.value > 0,
            "FlexPaymentDivider: Insufficient message value"
        );
        for (uint256 i = 0; i < _recipientCount; i++) {
            address payable recipient = _recipientsById[i];
            uint256 change = (msg.value * _percentagesByRecipient[recipient]) % 100;
            uint256 amount = (msg.value * _percentagesByRecipient[recipient]) / 100;
            uint256 totalChange = _changeByRecipient[recipient] + change;
            _changeByRecipient[recipient] = totalChange;
            if (totalChange >= 100) {
                _changeByRecipient[recipient] = totalChange % 100;
                amount += (totalChange / 100);
            }
            _balancesByRecipient[recipient] += amount;
        }
    }

    /**
     * @notice Transfers to each recipient their designated percenatage of the
     * Ether held by this contract.
     * @custom:require Caller must be owner.
     *
     * @custom:warning
     * ===============
     * A denial of service attack is possible if any of the recipients revert.
     * The {withdraw} method can be used in the event of this attack.
     *
     * @custom:warning
     * ===============
     * Forwarding all gas opens the door to reentrancy vulnerabilities. Make
     * sure you trust the recipient, or are either following the
     * checks-effects-interactions pattern or using {ReentrancyGuard}.
     */
    function disperse() public onlyOwner {
        for (uint256 i = 0; i < _recipientCount; i++) {
            address payable recipient = _recipientsById[i];
            withdraw(recipient);
        }
    }

    /**
     * @notice Transfers to recipient their designated percentage of the Ether
     * held in this contract.
     * @custom:require Caller must not already be withdrawing.
     * @custom:require Balance to withdraw must be above 0.
     *
     * @custom:warning
     * ===============
     * Forwarding all gas opens the door to reentrancy vulnerabilities. Make
     * sure you trust the recipient, or are either following the
     * checks-effects-interactions pattern or using {ReentrancyGuard}.
     */
    function withdraw(address payable recipient) public {
        require(
            !isWithdrawing(_msgSender()),
            "FlexPaymentDivider: Can not reenter"
        );
        _isWithdrawingByAccount[_msgSender()] = 1;

        uint256 amount = _balancesByRecipient[recipient];
        // IMPORTANT: Do not revert here so `disperse` can not have DoS when a
        // recipient does not yet have a balance to withdraw.
        if (amount > 0) {
            _balancesByRecipient[recipient] = 0;
            recipient.sendValue(amount);
        }

        _isWithdrawingByAccount[_msgSender()] = 0;
    }

    /* INTERNAL */

    /**
     * @dev Sets mappings for recipients and respective percentages.
     * This method is only used once in the constructor. Recipients and
     * percentages can not be modified after deployment.
     * @custom:require Input lengths must be equal. Order matters.
     * @custom:require Each percentage must be above 0 and below 100.
     * @custom:require The sum of all percentages must be 100.
     * @param recipients_ Account addresses receiving a percentage of deposited
     * funds.
     * @param percentages_ Amounts for accounts at the same index in the
     * {recipients} parameter to allocate from deposited funds.
     *
     * @custom:warning
     * ===============
     * Recipient accounts should be trusted.
     */
    function _setupRecipients(
        address payable[] memory recipients_,
        uint256[] memory percentages_
    ) internal {
        require(
            recipients_.length == percentages_.length,
            "FlexPaymentDivider: Unequal input lengths"
        );
        uint256 sum = 0;
        for (uint256 i = 0; i < recipients_.length; i++) {
            require(
                percentages_[i] > 0,
                "FlexPaymentDivider: Percentage must exceed 0"
            );
            require(
                percentages_[i] <= 100,
                "FlexPaymentDivider: Percentage must not exceed 100"
            );
            sum += percentages_[i];
            _recipientCount += 1;
            _recipientsById[i] = recipients_[i];
            _percentagesByRecipient[_recipientsById[i]] = percentages_[i];
        }
        require(sum == 100, "FlexPaymentDivider: Percentages must sum to 100");
    }

    function isWithdrawing(address account) internal view returns (bool) {
        return _isWithdrawingByAccount[account] == 1;
    }
}

/**
 * @notice Token IDs are positive integers starting at 1.
 */
contract BLOCKRUNRS_NFT is ERC721Enumerable, Ownable {
    using Address for address;
    using Strings for uint256;

    uint256 public constant MAX_TOTAL_SUPPLY = 9_999;
    uint256 public constant MAX_ROLLING_SUPPLY = 9_899; // Includes max presale supply
    uint256 public constant MAX_PRESALE_SUPPLY = 6_250;
    uint256 public constant MAX_PRIVATE_SUPPLY = 100;

    uint256 public constant ROLLING_PURCHASE_LIMIT = 20;
    uint256 public constant PRESALE_PURCHASE_LIMIT = 5;

    bool public rollingPurchasesEnabled = false;
    bool public presale1PurchasesEnabled = false;
    bool public presale2PurchasesEnabled = false;

    address private _manager;

    uint256 private _rollingSupply;
    uint256 private _presaleSupply;
    uint256 private _privateSupply;

    string private _tokenBaseURI;

    mapping(address => uint256) private _presalePurchasesByAccount;
    mapping(address => uint256) private _rollingPurchasesByAccount;

    // 0 = false, 1 = true
    mapping(address => uint8) private _isPresale1Account;
    mapping(address => uint8) private _isPresale2Account;
    mapping(address => uint8) private _isPurchasing;

    FlexPaymentDivider private immutable _paymentHandler;

    constructor(
        string memory name,
        string memory symbol,
        string memory tokenBaseURI_,
        address payable[] memory payoutAccounts_,
        uint256[] memory payoutPercentages_
    ) ERC721(name, symbol) {
        _tokenBaseURI = tokenBaseURI_;
        _paymentHandler = new FlexPaymentDivider(payoutAccounts_, payoutPercentages_);
    }

    /* MODIFIERS */

    /**
     * @dev Throws if called by any account that is not the owner or manager.
     */
    modifier onlyAuthorized() {
        require(isAuthorized(_msgSender()));
        _;
    }

    /* GETTERS */

    function manager() external view returns (address) {
        return _manager;
    }

    function paymentHandler() external view returns (address) {
        return address(_paymentHandler);
    }

    function rollingSupplyAvailable() public view returns (uint256) {
        uint256 available = MAX_ROLLING_SUPPLY - _presaleSupply - _rollingSupply;
        if (available < 0) {
            return 0;
        }
        return available;
    }

    function presaleSupplyAvailable() public view returns (uint256) {
        if (_presaleSupply > MAX_PRESALE_SUPPLY) {
            return 0;
        }
        return MAX_PRESALE_SUPPLY - _presaleSupply;
    }

    function privateSupplyAvailable() public view returns (uint256) {
        if (_privateSupply > MAX_PRIVATE_SUPPLY) {
            return 0;
        }
        return MAX_PRIVATE_SUPPLY - _privateSupply;
    }

    function isPresale1Account(address account) public view returns (bool) {
        return _isPresale1Account[account] == 1;
    }

    function isPresale2Account(address account) public view returns (bool) {
        return _isPresale2Account[account] == 1;
    }

    function isAuthorized(address account) public view returns (bool) {
        return account == owner() || account == _manager;
    }

    /* PAYABLE */

    function purchasePresale(
        uint256 amount,
        uint8 safeMode,
        uint8 presaleType
    ) external payable {
        require(amount > 0);
        require(
            !isPurchasing(_msgSender())
        );
        require(
            totalSupply() < MAX_TOTAL_SUPPLY
        );
        require(
            amount <= presaleSupplyAvailable()
        );
        require(
            _presalePurchasesByAccount[_msgSender()] + amount <= PRESALE_PURCHASE_LIMIT
        );

        if (presaleType == 2) {
            require(
                presale2PurchasesEnabled
            );
            require(
                isPresale2Account(_msgSender())
            );
            require(
                msg.value >= 0.04 ether * amount
            );
        } else {
            require(
                presale1PurchasesEnabled
            );
            require(
                isPresale1Account(_msgSender())
            );
            require(
                msg.value >= 0.05 ether * amount
            );
        }

        _isPurchasing[_msgSender()] = 1;

        _handleDeposit(msg.value, safeMode);

        for (uint256 i = 0; i < amount; i++) {
            uint256 tokenId = 1 + totalSupply();
            _presaleSupply += 1;
            _presalePurchasesByAccount[_msgSender()] += 1;
            _safeMint(_msgSender(), tokenId);
        }

        _isPurchasing[_msgSender()] = 0;
    }

    function purchase(uint256 amount, uint8 safeMode) external payable {
        require(amount > 0);
        require(
            !isPurchasing(_msgSender())
        );
        require(
            totalSupply() < MAX_TOTAL_SUPPLY
        );
        require(
            amount <= rollingSupplyAvailable()
        );
        require(
            _rollingPurchasesByAccount[_msgSender()] + amount <= ROLLING_PURCHASE_LIMIT
        );
        require(rollingPurchasesEnabled);
        require(
            msg.value >= 0.05 ether * amount,
            "BLOCKRUNRS: Not enough Ether provided"
        );

        _isPurchasing[_msgSender()] = 1;

        _handleDeposit(msg.value, safeMode);

        for (uint256 i = 0; i < amount; i++) {
            uint256 tokenId = 1 + totalSupply();
            _rollingSupply += 1;
            _rollingPurchasesByAccount[_msgSender()] += 1;
            _safeMint(_msgSender(), tokenId);
        }

        _isPurchasing[_msgSender()] = 0;
    }

    /* PRIVILEGED */

    function gift(
        address[] calldata recipients,
        uint256[] calldata amounts
    ) external onlyAuthorized {
        require(
            recipients.length == amounts.length,
            "BLOCKRUNRS: Input lengths must match"
        );
        require(
            totalSupply() < MAX_TOTAL_SUPPLY,
            "BLOCKRUNRS: Maximum supply reached"
        );

        uint256 _privateSupplyAvailable = privateSupplyAvailable();
        uint256 totalAmount;

        for (uint256 i = 0; i < recipients.length; i++) {
            address recipient = recipients[i];
            uint256 amount = amounts[i];
            for (uint256 j = 0; j < amount; j++) {
                uint256 tokenId = 1 + totalSupply();
                _privateSupply += 1;
                _safeMint(recipient, tokenId);
            }
        }

        require(
            totalAmount <= _privateSupplyAvailable,
            "BLOCKRUNRS: Amounts exceed supply available"
        );
    }

    function startPresale1() external onlyAuthorized {
        presale1PurchasesEnabled = true;
    }

    function stopPresale1() external onlyAuthorized {
        presale1PurchasesEnabled = false;
    }

    function startPresale2() external onlyAuthorized {
        presale2PurchasesEnabled = true;
    }

    function stopPresale2() external onlyAuthorized {
        presale2PurchasesEnabled = false;
    }

    function startRollingSale() external onlyAuthorized {
        rollingPurchasesEnabled = true;
    }

    function stopRollingSale() external onlyAuthorized {
        rollingPurchasesEnabled = false;
    }

    function addPresaleAccounts(
        address[] calldata accounts,
        uint8 presaleType
    ) external onlyAuthorized {
        if (presaleType == 2) {
            for (uint256 i = 0; i < accounts.length; i++) {
                require(
                    accounts[i] != address(0),
                    "BLOCKRUNRS: Address 0 not allowed"
                );
                _isPresale2Account[accounts[i]] = 1;
            }
        } else {
            for (uint256 i = 0; i < accounts.length; i++) {
                require(
                    accounts[i] != address(0),
                    "BLOCKRUNRS: Address 0 not allowed"
                );
                _isPresale1Account[accounts[i]] = 1;
            }
        }
    }

    function removePresaleAccounts(
        address[] calldata accounts,
        uint8 presaleType
    ) external onlyAuthorized {
        if (presaleType == 2) {
            for (uint256 i = 0; i < accounts.length; i++) {
                require(
                    isPresale2Account(accounts[i]),
                    "BLOCKRUNRS: One of the accounts is not a presale 2 account"
                );
                _isPresale2Account[accounts[i]] = 0;
            }
        } else {
            for (uint256 i = 0; i < accounts.length; i++) {
                require(
                    isPresale1Account(accounts[i]),
                    "BLOCKRUNRS: One of the accounts is not a presale 1 account"
                );
                _isPresale1Account[accounts[i]] = 0;
            }
        }
    }

    function setTokenBaseURI(string calldata URI) external onlyAuthorized {
        _tokenBaseURI = URI;
    }

    /**
     * @dev Set to the 0 address to revoke the current manager's authorization.
     */
    function setManager(address manager_) external onlyOwner {
        _manager = manager_;
    }

    /* INTERNAL */

    /**
     * @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 override returns (string memory) {
        return _tokenBaseURI;
    }

    /* PRIVATE */

    function _handleDeposit(uint256 value, uint8 safeMode) private {
        if (safeMode > 0) { // >0 == true, 0 == false
            _depositAsPull(value);
        } else {
            _depositAsPush(value);
        }
    }

    function _depositAsPush(uint256 value) private {
        _paymentHandler.deposit{value: value}();
        _paymentHandler.disperse();
    }

    function _depositAsPull(uint256 value) private {
        _paymentHandler.deposit{value: value}();
    }

    function isPurchasing(address account) private view returns (bool) {
        return _isPurchasing[account] == 1;
    }
}