// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        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);
            }
        }
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC721.sol";
import "./IERC721Receiver.sol";
import "./extensions/IERC721Metadata.sol";
import "../../utils/Address.sol";
import "../../utils/Context.sol";
import "../../utils/Strings.sol";
import "../../utils/introspection/ERC165.sol";

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    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 {}
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../ERC721.sol";
import "./IERC721Enumerable.sol";

/**
 * @dev This implements an optional extension of {ERC721} defined in the EIP that adds
 * enumerability of all the token ids in the contract as well as all token ids owned by each
 * account.
 */
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();
    }
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.7;

    /**

       ____                 _    ____                 
      / ___| ___   ___   __| |  / ___|_   _ _   _ ___ 
     | |  _ / _ \ / _ \ / _` | | |  _| | | | | | / __|
     | |_| | (_) | (_) | (_| | | |_| | |_| | |_| \__ \
      \____|\___/ \___/ \__,_|  \____|\__,_|\__, |___/
                                            |___/    
    
                                        goodguysnft.com
    */

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
import "./IMillionDollarRat.sol";

contract GoodGuys is ERC721Enumerable, Ownable {
    using Strings for uint256;

    /// @dev Emitted when {startSale} is executed and the sale isn't on.
    event SaleStarted();
    /// @dev Emitted when {pauseSale} is executed and the sale is on.
    event SalePaused();
    /// @dev Emitted when {startSale} is executed for the first time.
    event ClaimsReserveUpdated(uint256 indexed reserve);
    /// @dev Emitted when a GG token is claimed based on a Rat held
    event GoodGuyClaimed(uint256 indexed ratId, uint256 indexed goodGuyId);
    /// @dev Emitted when {reveal} is executed (once-only).
    event Reveal(uint256 indexed startingIndex);
    /// @dev Emitted when {setTokenURI} is executed.
    event TokenURISet(string indexed tokenUri);
    /// @dev Emitted when {lockTokenURI} is executed (once-only).
    event TokenURILocked(string indexed tokenUri);

    string public constant GG_PROVENANCE = "79d0a3bd67ca56a46d31ab9ec9cf73be4ea11f259caf82fe301c2aa847a1cb87";
    uint256 public constant MAX_RAT_SUPPLY = 3311;
    uint256 public constant MAX_GG_SUPPLY = 10000;
    uint256 public constant GG_PACK_LIMIT = 10;
    uint256 public constant GG_PRICE = 6 ether / 100;
    uint256 private constant CLAIM_PERIOD_DURATION = 1 weeks;
    uint256 private constant RECLAIM_RESERVE = 150;
    string private constant PLACEHOLDER_SUFFIX = "placeholder.json";
    string private constant METADATA_INFIX = "/metadata/";
    IMillionDollarRat private MDR =
        IMillionDollarRat(0x99B9791D1580BF504a1709d310923A46237c8f2C);

    uint256 public startingIndexBlock;
    uint256 public startingIndex;
    uint256 public ratClaimsReserve;
    uint256 public ratClaimsCounter;
    mapping(uint256 => bool) public ratClaims;
    bool public saleStarted;
    uint256 public saleStartedAt;
    bool public tokenURILocked;

    // current metadata base prefix
    string private _baseTokenUri;

    // prevent callers from sending ETH directly
    receive() external payable {
        revert();
    }

    // prevent callers from sending ETH directly
    fallback() external payable {
        revert();
    }

    constructor() ERC721("Good Guys", "GG") {
    }

    // ----- PUBLIC -----
    // ------------------
    /*
     * @dev Start or restart distribution. Only callable by the owner.
     * On the first call,
     * - set claim reserve value (once-only)
     * - set sale start timestamp and emit {ClaimsReserveUpdated} (once-only)
     * - emit {SaleStarted}
     *
     * On subsequent calls,
     * - restart sale and emit {SaleStarted} if paused;
     *   otherwise, do nothing
     */
    function startSale() public onlyOwner {
        // will also restart when on pause
        if (!saleStarted) {
            saleStarted = true;
            emit SaleStarted();
        }
        // once-only: set timestamp and update reserve
        if (saleStartedAt == 0) {
            _setRatClaimsReserve();
            saleStartedAt = block.timestamp;
        }
    }

    /*
     * @dev If sale is on, pause it and emit {SalePaused}; otherwise, do nothing.
     *   Only callable by the owner.
     */
    function pauseSale() public onlyOwner {
        if (saleStarted) {
            saleStarted = false;
            emit SalePaused();
        }
    }

    /**
     * @dev Claim GGs based on Rats owned. Implements 6 ways to claim; which one is used
     * depends on the values of the arguments `claimedRatIds`, `from`, and `count`.
     *
     * I. Claim All. Claims as many GGs as there are unclaimed Rats held by the caller.
     * Set `claimedRatIds` to [] (empty array), `from` to 0, and `count` to 0 as well.
     *
     * II. Claim Based On A Specific Rat. Claims a single GG.
     * Set `claimedRatIds` to [`ratId`] (where `ratId` is the identity of a Rat you hold,
     * which hasn't been used to claim a GG), `from` to 0, and `count` to 0 as well.
     *
     * III. Claim Multiple GGs Based On Specific Rats. Same as II, for multiple GGs.
     * Set `claimedRatIds` to [`ratId1`, `ratId2`, ...] (only using identities of the Rats
     * you hold, which haven't been used to claim GGs), `from` to 0, and `count` to 0 as well.
     *
     * IV. Claim Based On The Next Unclaimed. Claims a single GG using the first available
     * Rat held by the caller, which hasn't been used in a claim before.
     * Set `claimedRatIds` to [0] (a single element, 0), `from` to 0, and `count` to 0 as well.
     *
     * V. Claim N. Same as IV, but will claim multiple GGs. Set `claimedRatIds` to [] (empty array),
     * `from` to 0, and `count` to the number of GGs to claim. Make sure you have enough unused Rats.
     *
     * VI. Claim Sequentially. Starting with a specific Rat identity, claim multiple GGs based on
     * the assumption that the Rats are allocated sequentially in the specified range and are all
     * held by the caller. I.e. `claim([], 362, 5)` will attemp to claim GGs based on held Rats
     * #362, #363, #364, #365, #366.
     */
    function claim(
        uint256[] memory claimedRatIds,
        uint256 from,
        uint256 count
    ) public {
        _enforceSaleStarted();
        _enforceClaimPeriod(true);
        if (claimedRatIds.length == 0) {
            if (from == 0 && count == 0) {
                // I. Claim All
                uint256[] memory unclaimed = _listUnclaimed();
                _enforceClaimConditions(unclaimed.length);
                for (uint256 i = 0; i < unclaimed.length; i++) {
                    _straightMintGG(msg.sender, unclaimed[i]);
                }
            } else {
                if (from == 0) {
                    // claim count GGs
                    _enforceClaimConditions(count);
                    for (uint256 i = 0; i < count; i++) {
                        _straightMintGG(msg.sender, _nextUnclaimedRatId());
                    }
                } else {
                    // claim count GGs starting with from
                    _enforceClaimConditions(count);
                    uint256[] memory tokenIds = _enforceSequentialAvailability(
                        from,
                        count
                    );
                    for (uint256 i = 0; i < tokenIds.length; i++) {
                        _straightMintGG(msg.sender, tokenIds[i]);
                    }
                }
            }
        } else {
            if (claimedRatIds.length == 1) {
                if (claimedRatIds[0] == 0) {
                    // claim single GG based on the next unclaimed Rat
                    _enforceClaimConditions(1);
                    _straightMintGG(msg.sender, _nextUnclaimedRatId());
                } else {
                    // claim single GG based on a specific unclaimed Rat
                    _enforceClaimConditions(1);
                    _straightMintGG(msg.sender, claimedRatIds[0]);
                }
            } else {
                // claim multiple GGs based on specific unclaimed Rats
                _enforceClaimConditions(claimedRatIds.length);
                for (uint256 i = 0; i < claimedRatIds.length; i++) {
                    _straightMintGG(msg.sender, claimedRatIds[i]);
                }
            }
        }
        _contemplateStartingIndex();
    }

    /**
     * @dev After the claim period has elapsed, mint unclaimed GGs to the owner.
     */
    function reclaim(uint256 count) public onlyOwner {
        _enforceClaimPeriod(false);
        _enforceClaimConditions(count);
        for (uint256 i = 0; i < count; i++) {
            _straightMintGG(msg.sender, MAX_RAT_SUPPLY);
        }
        _contemplateStartingIndex();
    }

    /**
     * @dev Count Rats owned by the caller, for which GoodGuys NFTs
     * have not yet been claimed.
     */
    function countUnclaimed() public view returns (uint256 result) {
        return _countUnclaimed();
    }

    /**
     * @dev List identities of the Rats owned by the caller, for which
     * GoodGuys NFTs have not yet been claimed.
     */
    function listUnclaimed() public view returns (uint256[] memory result) {
        return _listUnclaimed();
    }

    /**
     * @dev Mint `numberOfGGs` GoodGuys.
     * - Will only mint up to (`MAX_GG_SUPPLY` - `ratClaimsReserve`) GoodGuys.
     * - Will mint up to `GG_PACK_LIMIT` items at once.
     * - Will only mint after the sale is started.
     * - ETH sent must equal (`numberOfGGs` * `GG_PRICE`)
     *
     * @param numberOfGGs The number of GoodGuys NFTs to mint.
     */
    function mintGGs(uint256 numberOfGGs) public payable {
        _enforceSaleStarted();
        require(totalSupply() < MAX_GG_SUPPLY, "SoldOut");
        require(numberOfGGs > 0, "ZeroNFTsRequested");
        require(numberOfGGs <= GG_PACK_LIMIT, "BuyLimitExceeded");
        require(GG_PRICE * numberOfGGs == msg.value, "InvalidETHAmount");
        require((MAX_GG_SUPPLY - ratClaimsReserve) -
                (totalSupply() - ratClaimsCounter) >= numberOfGGs, "MintableSupplyExceeded");

        for (uint256 i = 0; i < numberOfGGs; i++) {
            // TODO: test
            _safeMint(msg.sender, totalSupply() + 1);
        }
        _contemplateStartingIndex();
    }

    /**
     * @dev Set `startingIndex` and allow {tokenURI} to return actual
     * token URIs instead of the placeholder. Emit {Reveal} with
     * `startingIndex` as the argument. Only callable by the owner, and
     * only once.
     */
    function reveal() public onlyOwner {
        require(startingIndex == 0, "StartingIndexAlreadySet");

        // account for pre-sellout reveal
        if (startingIndexBlock == 0) {
            startingIndexBlock = block.number;
        }

        uint256 _start = uint256(blockhash(startingIndexBlock)) % MAX_GG_SUPPLY;

        if (
            (_start > block.number)
                ? ((_start - block.number) > 255)
                : ((block.number - _start) > 255)
        ) {
            _start = uint256(blockhash(block.number - 1)) % MAX_GG_SUPPLY;
        }

        if (_start == 0) {
            _start = _start + 1;
        }

        startingIndex = _start;

        emit Reveal(startingIndex);
    }

    /**
     * @dev Set base token URI. Only callable by the owner and only
     * if token URI hasn't been locked through {lockTokenURI}. Emit
     * TokenURISet with the new value on every successful execution.
     *
     * @param newUri The new base URI to use from this point on.
     */
    function setTokenURI(string memory newUri)
        public
        onlyOwner
        whenUriNotLocked
    {
        _baseTokenUri = newUri;
        emit TokenURISet(_baseTokenUri);
    }

    /**
     * @dev Prevent further modification of the currently set base token URI.
     *  Do nothing if already locked. Emit {TokenURILocked} with the current
     *  base token URI on initial execution. Only callable by the owner.
     */
    function lockTokenURI() public onlyOwner {
        if (!tokenURILocked) {
            tokenURILocked = true;
            emit TokenURILocked(_baseTokenUri);
        }
    }

    /**
     * @dev Withdraw `amount` WEI out of the current balance. Only callable
     * by the owner.
     *
     * @param amount The amount to withdraw, in WEI. Must be greater than 0 and
     * must not exceed the contract balance.
     */
    function withdraw(uint256 amount) public onlyOwner {
        require(amount > 0, "ZeroWEIRequested");
        require(amount <= address(this).balance, "AmountExceedsBalance");
        
        (bool success, ) = payable(msg.sender).call{value: amount}("");

        require(success, "ETHTransferFailed");
    }

    /**
     * @dev Prior to execution of {reveal}, return the placeholder URI for
     * any token minted or claimed; after the execution of {reveal}, return
     * adjusted URIs based on `startingIndex` cyclic shift.
     *
     * @param tokenId Identity of an existing (minted) GG NFT.
     */
    function tokenURI(uint256 tokenId)
        public
        view
        virtual
        override
        returns (string memory)
    {
        require(_exists(tokenId), "UnknownTokenId");

        string memory result;

        if (startingIndex > 0) {
            result = indexedTokenURI((tokenId + startingIndex) % MAX_GG_SUPPLY);
        } else {
            result = placeholderURI();
        }

        return result;
    }

    // ---- INTERNAL ----
    // ------------------
    function _setRatClaimsReserve() internal {
        ratClaimsReserve = 3310 + RECLAIM_RESERVE;
        emit ClaimsReserveUpdated(ratClaimsReserve);
    }

    function claimPeriodInProgress() internal view returns (bool) {
        return (block.timestamp <= (saleStartedAt + CLAIM_PERIOD_DURATION));
    }

    function _enforceSaleStarted() internal view {
        require(saleStarted, "SaleNotOn");
    }

    function _enforceClaimPeriod(bool on) internal view {
        if (on) {
            require(claimPeriodInProgress(), "ClaimPeriodHasEnded");
        } else {
            require(!claimPeriodInProgress(), "ClaimPeriodHasntEnded");
        }
    }

    function _straightMintGG(address to, uint256 claimedRatId) internal {
        // TODO: test
        _safeMint(to, totalSupply() + 1);
        if (claimedRatId < MAX_RAT_SUPPLY) {
            // enforce rat not claimed
            require(!ratClaims[claimedRatId], "DuplicateClaim");
            // enforce ownership
            require(to == MDR.ownerOf(claimedRatId), "RatNotOwned");

            ratClaims[claimedRatId] = true;
        } // else is being reclaimed by the owner
        ratClaimsCounter++;

        uint256 emitRatId = (claimedRatId < MAX_RAT_SUPPLY) ? 0 : claimedRatId;
        uint256 emitGGId = totalSupply();

        emit GoodGuyClaimed(emitRatId, emitGGId);
    }

    function _contemplateStartingIndex() internal {
        /*
         * If not all GGs have been minted and no one is minting past that point, the
         * code below is not executed, and thus startingIndexBlock is not set. We fix
         * that in {reveal}.
         */
        if (startingIndexBlock == 0 && (totalSupply() == MAX_GG_SUPPLY)) {
            startingIndexBlock = block.number;
        }
    }

    function _countUnclaimed() internal view returns (uint256 result) {
        uint256 count = MDR.balanceOf(msg.sender);

        for (uint256 t = 0; t < count; t++) {
            if (!ratClaims[MDR.tokenOfOwnerByIndex(msg.sender, t)]) {
                result++;
            }
        }
    }

    function _listUnclaimed() internal view returns (uint256[] memory) {
        uint256 tokens = MDR.balanceOf(msg.sender);
        uint256 count = _countUnclaimed();
        uint256[] memory tokensToClaim = new uint256[](count);
        uint256 unclaimedIndex;

        for (uint256 t = 0; t < tokens; t++) {
            uint256 ratId = MDR.tokenOfOwnerByIndex(msg.sender, t);
            if (!ratClaims[ratId]) {
                tokensToClaim[unclaimedIndex] = ratId;
                unclaimedIndex++;
            }
        }

        return tokensToClaim;
    }

    function _nextUnclaimedRatId() internal view returns (uint256 result) {
        uint256 count = MDR.balanceOf(msg.sender);

        for (uint256 t = 0; t < count; t++) {
            uint256 tokenId = MDR.tokenOfOwnerByIndex(msg.sender, t);
            if (!ratClaims[tokenId]) {
                result = tokenId;
                break;
            }
        }

        require(result > 0, "OutOfClaims");
    }

    function _enforceClaimConditions(uint256 count) internal view {
        require(count > 0, "ZeroClaimCount");
        require(ratClaimsReserve >= (ratClaimsCounter + count), "ClaimReserveExceeded");
    }

    function _enforceSequentialAvailability(uint256 from, uint256 count)
        internal
        view
        returns (uint256[] memory)
    {
        uint256 tokens = MDR.balanceOf(msg.sender);
        uint256[] memory tokensToClaim = new uint256[](count);

        for (uint256 t = 0; t < tokens; t++) {
            if (MDR.tokenOfOwnerByIndex(msg.sender, t) == from) {
                for (uint256 f = t; f < (t + count); f++) {
                    uint256 tokenId = MDR.tokenOfOwnerByIndex(msg.sender, f);
                    require(!ratClaims[tokenId], "ImpossibleClaim");
                    tokensToClaim[f - t] = tokenId;
                }
            }
        }

        return tokensToClaim;
    }

    modifier whenUriNotLocked() {
        require(!tokenURILocked, "TokenURILockedErr");
        _;
    }

    function placeholderURI() internal view returns (string memory) {
        return
            string(
                abi.encodePacked(
                    _baseTokenUri,
                    METADATA_INFIX,
                    PLACEHOLDER_SUFFIX
                )
            );
    }

    function indexedTokenURI(uint256 tokenId)
        internal
        view
        returns (string memory)
    {
        return
            string(
                abi.encodePacked(
                    _baseTokenUri,
                    METADATA_INFIX,
                    tokenId.toString(),
                    ".json"
                )
            );
    }
}

// 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);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {
    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the token collection symbol.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// SPDX-License-Identifier: MIT

pragma solidity 0.8.7;

interface IMillionDollarRat {
    function ownerOf(uint256 tokenId) external view returns (address);
    function balanceOf(address owner) external view returns (uint256);
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);
}

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "../utils/Context.sol";

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

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

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _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);
    }
}

// SPDX-License-Identifier: MIT

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);
    }
}

{
  "compilationTarget": {
    "GoodGuys.sol": "GoodGuys"
  },
  "evmVersion": "london",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}