以太坊如何发布NFT到opensea

/***Submitted for verification at Etherscan.io on 2021-08-18
*/pragma solidity >=0.6.0 <0.8.0;/** @dev Provides information about the current execution context, including the* sender of the transaction and its data. While these are generally available* via msg.sender and msg.data, they should not be accessed in such a direct* manner, since when dealing with GSN meta-transactions the account sending and* paying for execution may not be the actual sender (as far as an application* is concerned).** This contract is only required for intermediate, library-like contracts.*/
abstract contract Context {function _msgSender() internal view virtual returns (address payable) {return msg.sender;}function _msgData() internal view virtual returns (bytes memory) {this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691return msg.data;}
}/*** @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);
}/*** @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;
}/*** @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);
}/*** @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);
}/*** @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);
}/*** @dev Implementation of the {IERC165} interface.** Contracts may inherit from this and call {_registerInterface} to declare* their support of an interface.*/
abstract contract ERC165 is IERC165 {/** bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7*/bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;/*** @dev Mapping of interface ids to whether or not it's supported.*/mapping(bytes4 => bool) private _supportedInterfaces;constructor () internal {// Derived contracts need only register support for their own interfaces,// we register support for ERC165 itself here_registerInterface(_INTERFACE_ID_ERC165);}/*** @dev See {IERC165-supportsInterface}.** Time complexity O(1), guaranteed to always use less than 30 000 gas.*/function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {return _supportedInterfaces[interfaceId];}/*** @dev Registers the contract as an implementer of the interface defined by* `interfaceId`. Support of the actual ERC165 interface is automatic and* registering its interface id is not required.** See {IERC165-supportsInterface}.** Requirements:** - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).*/function _registerInterface(bytes4 interfaceId) internal virtual {require(interfaceId != 0xffffffff, "ERC165: invalid interface id");_supportedInterfaces[interfaceId] = true;}
}/*** @dev Wrappers over Solidity's arithmetic operations with added overflow* checks.** Arithmetic operations in Solidity wrap on overflow. This can easily result* in bugs, because programmers usually assume that an overflow raises an* error, which is the standard behavior in high level programming languages.* `SafeMath` restores this intuition by reverting the transaction when an* operation overflows.** Using this library instead of the unchecked operations eliminates an entire* class of bugs, so it's recommended to use it always.*/
library SafeMath {/*** @dev Returns the addition of two unsigned integers, with an overflow flag.** _Available since v3.4._*/function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {uint256 c = a + b;if (c < a) return (false, 0);return (true, c);}/*** @dev Returns the substraction of two unsigned integers, with an overflow flag.** _Available since v3.4._*/function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {if (b > a) return (false, 0);return (true, a - b);}/*** @dev Returns the multiplication of two unsigned integers, with an overflow flag.** _Available since v3.4._*/function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {// Gas optimization: this is cheaper than requiring 'a' not being zero, but the// benefit is lost if 'b' is also tested.// See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522if (a == 0) return (true, 0);uint256 c = a * b;if (c / a != b) return (false, 0);return (true, c);}/*** @dev Returns the division of two unsigned integers, with a division by zero flag.** _Available since v3.4._*/function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {if (b == 0) return (false, 0);return (true, a / b);}/*** @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.** _Available since v3.4._*/function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {if (b == 0) return (false, 0);return (true, a % b);}/*** @dev Returns the addition of two unsigned integers, reverting on* overflow.** Counterpart to Solidity's `+` operator.** Requirements:** - Addition cannot overflow.*/function add(uint256 a, uint256 b) internal pure returns (uint256) {uint256 c = a + b;require(c >= a, "SafeMath: addition overflow");return c;}/*** @dev Returns the subtraction of two unsigned integers, reverting on* overflow (when the result is negative).** Counterpart to Solidity's `-` operator.** Requirements:** - Subtraction cannot overflow.*/function sub(uint256 a, uint256 b) internal pure returns (uint256) {require(b <= a, "SafeMath: subtraction overflow");return a - b;}/*** @dev Returns the multiplication of two unsigned integers, reverting on* overflow.** Counterpart to Solidity's `*` operator.** Requirements:** - Multiplication cannot overflow.*/function mul(uint256 a, uint256 b) internal pure returns (uint256) {if (a == 0) return 0;uint256 c = a * b;require(c / a == b, "SafeMath: multiplication overflow");return c;}/*** @dev Returns the integer division of two unsigned integers, reverting on* division by zero. The result is rounded towards zero.** Counterpart to Solidity's `/` operator. Note: this function uses a* `revert` opcode (which leaves remaining gas untouched) while Solidity* uses an invalid opcode to revert (consuming all remaining gas).** Requirements:** - The divisor cannot be zero.*/function div(uint256 a, uint256 b) internal pure returns (uint256) {require(b > 0, "SafeMath: division by zero");return a / b;}/*** @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),* reverting when dividing by zero.** Counterpart to Solidity's `%` operator. This function uses a `revert`* opcode (which leaves remaining gas untouched) while Solidity uses an* invalid opcode to revert (consuming all remaining gas).** Requirements:** - The divisor cannot be zero.*/function mod(uint256 a, uint256 b) internal pure returns (uint256) {require(b > 0, "SafeMath: modulo by zero");return a % b;}/*** @dev Returns the subtraction of two unsigned integers, reverting with custom message on* overflow (when the result is negative).** CAUTION: This function is deprecated because it requires allocating memory for the error* message unnecessarily. For custom revert reasons use {trySub}.** Counterpart to Solidity's `-` operator.** Requirements:** - Subtraction cannot overflow.*/function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {require(b <= a, errorMessage);return a - b;}/*** @dev Returns the integer division of two unsigned integers, reverting with custom message on* division by zero. The result is rounded towards zero.** CAUTION: This function is deprecated because it requires allocating memory for the error* message unnecessarily. For custom revert reasons use {tryDiv}.** Counterpart to Solidity's `/` operator. Note: this function uses a* `revert` opcode (which leaves remaining gas untouched) while Solidity* uses an invalid opcode to revert (consuming all remaining gas).** Requirements:** - The divisor cannot be zero.*/function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {require(b > 0, errorMessage);return a / b;}/*** @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),* reverting with custom message when dividing by zero.** CAUTION: This function is deprecated because it requires allocating memory for the error* message unnecessarily. For custom revert reasons use {tryMod}.** Counterpart to Solidity's `%` operator. This function uses a `revert`* opcode (which leaves remaining gas untouched) while Solidity uses an* invalid opcode to revert (consuming all remaining gas).** Requirements:** - The divisor cannot be zero.*/function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {require(b > 0, errorMessage);return a % b;}
}/*** @dev Collection of functions related to the address type*/
library Address {/*** @dev Returns true if `account` is a contract.** [IMPORTANT]* ====* It is unsafe to assume that an address for which this function returns* false is an externally-owned account (EOA) and not a contract.** Among others, `isContract` will return false for the following* types of addresses:**  - an externally-owned account*  - a contract in construction*  - an address where a contract will be created*  - an address where a contract lived, but was destroyed* ====*/function isContract(address account) internal view returns (bool) {// This method relies on extcodesize, which returns 0 for contracts in// construction, since the code is only stored at the end of the// constructor execution.uint256 size;// solhint-disable-next-line no-inline-assemblyassembly { size := extcodesize(account) }return size > 0;}/*** @dev Replacement for Solidity's `transfer`: sends `amount` wei to* `recipient`, forwarding all available gas and reverting on errors.** https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost* of certain opcodes, possibly making contracts go over the 2300 gas limit* imposed by `transfer`, making them unable to receive funds via* `transfer`. {sendValue} removes this limitation.** https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].** IMPORTANT: because control is transferred to `recipient`, care must be* taken to not create reentrancy vulnerabilities. Consider using* {ReentrancyGuard} or the* https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].*/function sendValue(address payable recipient, uint256 amount) internal {require(address(this).balance >= amount, "Address: insufficient balance");// solhint-disable-next-line avoid-low-level-calls, avoid-call-value(bool success, ) = recipient.call{ value: amount }("");require(success, "Address: unable to send value, recipient may have reverted");}/*** @dev Performs a Solidity function call using a low level `call`. A* plain`call` is an unsafe replacement for a function call: use this* function instead.** If `target` reverts with a revert reason, it is bubbled up by this* function (like regular Solidity function calls).** Returns the raw returned data. To convert to the expected return value,* use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].** Requirements:** - `target` must be a contract.* - calling `target` with `data` must not revert.** _Available since v3.1._*/function functionCall(address target, bytes memory data) internal returns (bytes memory) {return functionCall(target, data, "Address: low-level call failed");}/*** @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with* `errorMessage` as a fallback revert reason when `target` reverts.** _Available since v3.1._*/function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {return functionCallWithValue(target, data, 0, errorMessage);}/*** @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],* but also transferring `value` wei to `target`.** Requirements:** - the calling contract must have an ETH balance of at least `value`.* - the called Solidity function must be `payable`.** _Available since v3.1._*/function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory) {return functionCallWithValue(target, data, value, "Address: low-level call with value failed");}/*** @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but* with `errorMessage` as a fallback revert reason when `target` reverts.** _Available since v3.1._*/function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage) internal returns (bytes memory) {require(address(this).balance >= value, "Address: insufficient balance for call");require(isContract(target), "Address: call to non-contract");// solhint-disable-next-line avoid-low-level-calls(bool success, bytes memory returndata) = target.call{ value: value }(data);return _verifyCallResult(success, returndata, errorMessage);}/*** @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],* but performing a static call.** _Available since v3.3._*/function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {return functionStaticCall(target, data, "Address: low-level static call failed");}/*** @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],* but performing a static call.** _Available since v3.3._*/function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {require(isContract(target), "Address: static call to non-contract");// solhint-disable-next-line avoid-low-level-calls(bool success, bytes memory returndata) = target.staticcall(data);return _verifyCallResult(success, returndata, errorMessage);}/*** @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],* but performing a delegate call.** _Available since v3.4._*/function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {return functionDelegateCall(target, data, "Address: low-level delegate call failed");}/*** @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],* but performing a delegate call.** _Available since v3.4._*/function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {require(isContract(target), "Address: delegate call to non-contract");// solhint-disable-next-line avoid-low-level-calls(bool success, bytes memory returndata) = target.delegatecall(data);return _verifyCallResult(success, returndata, errorMessage);}function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {if (success) {return returndata;} else {// Look for revert reason and bubble it up if presentif (returndata.length > 0) {// The easiest way to bubble the revert reason is using memory via assembly// solhint-disable-next-line no-inline-assemblyassembly {let returndata_size := mload(returndata)revert(add(32, returndata), returndata_size)}} else {revert(errorMessage);}}}
}/*** @dev Library for managing* https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive* types.** Sets have the following properties:** - Elements are added, removed, and checked for existence in constant time* (O(1)).* - Elements are enumerated in O(n). No guarantees are made on the ordering.** ```* contract Example {*     // Add the library methods*     using EnumerableSet for EnumerableSet.AddressSet;**     // Declare a set state variable*     EnumerableSet.AddressSet private mySet;* }* ```** As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)* and `uint256` (`UintSet`) are supported.*/
library EnumerableSet {// To implement this library for multiple types with as little code// repetition as possible, we write it in terms of a generic Set type with// bytes32 values.// The Set implementation uses private functions, and user-facing// implementations (such as AddressSet) are just wrappers around the// underlying Set.// This means that we can only create new EnumerableSets for types that fit// in bytes32.struct Set {// Storage of set valuesbytes32[] _values;// Position of the value in the `values` array, plus 1 because index 0// means a value is not in the set.mapping (bytes32 => uint256) _indexes;}/*** @dev Add a value to a set. O(1).** Returns true if the value was added to the set, that is if it was not* already present.*/function _add(Set storage set, bytes32 value) private returns (bool) {if (!_contains(set, value)) {set._values.push(value);// The value is stored at length-1, but we add 1 to all indexes// and use 0 as a sentinel valueset._indexes[value] = set._values.length;return true;} else {return false;}}/*** @dev Removes a value from a set. O(1).** Returns true if the value was removed from the set, that is if it was* present.*/function _remove(Set storage set, bytes32 value) private returns (bool) {// We read and store the value's index to prevent multiple reads from the same storage slotuint256 valueIndex = set._indexes[value];if (valueIndex != 0) { // Equivalent to contains(set, value)// To delete an element from the _values array in O(1), we swap the element to delete with the last one in// the array, and then remove the last element (sometimes called as 'swap and pop').// This modifies the order of the array, as noted in {at}.uint256 toDeleteIndex = valueIndex - 1;uint256 lastIndex = set._values.length - 1;// When the value to delete is the last one, the swap operation is unnecessary. However, since this occurs// so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.bytes32 lastvalue = set._values[lastIndex];// Move the last value to the index where the value to delete isset._values[toDeleteIndex] = lastvalue;// Update the index for the moved valueset._indexes[lastvalue] = toDeleteIndex + 1; // All indexes are 1-based// Delete the slot where the moved value was storedset._values.pop();// Delete the index for the deleted slotdelete set._indexes[value];return true;} else {return false;}}/*** @dev Returns true if the value is in the set. O(1).*/function _contains(Set storage set, bytes32 value) private view returns (bool) {return set._indexes[value] != 0;}/*** @dev Returns the number of values on the set. O(1).*/function _length(Set storage set) private view returns (uint256) {return set._values.length;}/*** @dev Returns the value stored at position `index` in the set. O(1).** Note that there are no guarantees on the ordering of values inside the* array, and it may change when more values are added or removed.** Requirements:** - `index` must be strictly less than {length}.*/function _at(Set storage set, uint256 index) private view returns (bytes32) {require(set._values.length > index, "EnumerableSet: index out of bounds");return set._values[index];}// Bytes32Setstruct Bytes32Set {Set _inner;}/*** @dev Add a value to a set. O(1).** Returns true if the value was added to the set, that is if it was not* already present.*/function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {return _add(set._inner, value);}/*** @dev Removes a value from a set. O(1).** Returns true if the value was removed from the set, that is if it was* present.*/function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {return _remove(set._inner, value);}/*** @dev Returns true if the value is in the set. O(1).*/function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {return _contains(set._inner, value);}/*** @dev Returns the number of values in the set. O(1).*/function length(Bytes32Set storage set) internal view returns (uint256) {return _length(set._inner);}/*** @dev Returns the value stored at position `index` in the set. O(1).** Note that there are no guarantees on the ordering of values inside the* array, and it may change when more values are added or removed.** Requirements:** - `index` must be strictly less than {length}.*/function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {return _at(set._inner, index);}// AddressSetstruct AddressSet {Set _inner;}/*** @dev Add a value to a set. O(1).** Returns true if the value was added to the set, that is if it was not* already present.*/function add(AddressSet storage set, address value) internal returns (bool) {return _add(set._inner, bytes32(uint256(uint160(value))));}/*** @dev Removes a value from a set. O(1).** Returns true if the value was removed from the set, that is if it was* present.*/function remove(AddressSet storage set, address value) internal returns (bool) {return _remove(set._inner, bytes32(uint256(uint160(value))));}/*** @dev Returns true if the value is in the set. O(1).*/function contains(AddressSet storage set, address value) internal view returns (bool) {return _contains(set._inner, bytes32(uint256(uint160(value))));}/*** @dev Returns the number of values in the set. O(1).*/function length(AddressSet storage set) internal view returns (uint256) {return _length(set._inner);}/*** @dev Returns the value stored at position `index` in the set. O(1).** Note that there are no guarantees on the ordering of values inside the* array, and it may change when more values are added or removed.** Requirements:** - `index` must be strictly less than {length}.*/function at(AddressSet storage set, uint256 index) internal view returns (address) {return address(uint160(uint256(_at(set._inner, index))));}// UintSetstruct UintSet {Set _inner;}/*** @dev Add a value to a set. O(1).** Returns true if the value was added to the set, that is if it was not* already present.*/function add(UintSet storage set, uint256 value) internal returns (bool) {return _add(set._inner, bytes32(value));}/*** @dev Removes a value from a set. O(1).** Returns true if the value was removed from the set, that is if it was* present.*/function remove(UintSet storage set, uint256 value) internal returns (bool) {return _remove(set._inner, bytes32(value));}/*** @dev Returns true if the value is in the set. O(1).*/function contains(UintSet storage set, uint256 value) internal view returns (bool) {return _contains(set._inner, bytes32(value));}/*** @dev Returns the number of values on the set. O(1).*/function length(UintSet storage set) internal view returns (uint256) {return _length(set._inner);}/*** @dev Returns the value stored at position `index` in the set. O(1).** Note that there are no guarantees on the ordering of values inside the* array, and it may change when more values are added or removed.** Requirements:** - `index` must be strictly less than {length}.*/function at(UintSet storage set, uint256 index) internal view returns (uint256) {return uint256(_at(set._inner, index));}
}/*** @dev Library for managing an enumerable variant of Solidity's* https://solidity.readthedocs.io/en/latest/types.html#mapping-types[`mapping`]* type.** Maps have the following properties:** - Entries are added, removed, and checked for existence in constant time* (O(1)).* - Entries are enumerated in O(n). No guarantees are made on the ordering.** ```* contract Example {*     // Add the library methods*     using EnumerableMap for EnumerableMap.UintToAddressMap;**     // Declare a set state variable*     EnumerableMap.UintToAddressMap private myMap;* }* ```** As of v3.0.0, only maps of type `uint256 -> address` (`UintToAddressMap`) are* supported.*/
library EnumerableMap {// To implement this library for multiple types with as little code// repetition as possible, we write it in terms of a generic Map type with// bytes32 keys and values.// The Map implementation uses private functions, and user-facing// implementations (such as Uint256ToAddressMap) are just wrappers around// the underlying Map.// This means that we can only create new EnumerableMaps for types that fit// in bytes32.struct MapEntry {bytes32 _key;bytes32 _value;}struct Map {// Storage of map keys and valuesMapEntry[] _entries;// Position of the entry defined by a key in the `entries` array, plus 1// because index 0 means a key is not in the map.mapping (bytes32 => uint256) _indexes;}/*** @dev Adds a key-value pair to a map, or updates the value for an existing* key. O(1).** Returns true if the key was added to the map, that is if it was not* already present.*/function _set(Map storage map, bytes32 key, bytes32 value) private returns (bool) {// We read and store the key's index to prevent multiple reads from the same storage slotuint256 keyIndex = map._indexes[key];if (keyIndex == 0) { // Equivalent to !contains(map, key)map._entries.push(MapEntry({ _key: key, _value: value }));// The entry is stored at length-1, but we add 1 to all indexes// and use 0 as a sentinel valuemap._indexes[key] = map._entries.length;return true;} else {map._entries[keyIndex - 1]._value = value;return false;}}/*** @dev Removes a key-value pair from a map. O(1).** Returns true if the key was removed from the map, that is if it was present.*/function _remove(Map storage map, bytes32 key) private returns (bool) {// We read and store the key's index to prevent multiple reads from the same storage slotuint256 keyIndex = map._indexes[key];if (keyIndex != 0) { // Equivalent to contains(map, key)// To delete a key-value pair from the _entries array in O(1), we swap the entry to delete with the last one// in the array, and then remove the last entry (sometimes called as 'swap and pop').// This modifies the order of the array, as noted in {at}.uint256 toDeleteIndex = keyIndex - 1;uint256 lastIndex = map._entries.length - 1;// When the entry to delete is the last one, the swap operation is unnecessary. However, since this occurs// so rarely, we still do the swap anyway to avoid the gas cost of adding an 'if' statement.MapEntry storage lastEntry = map._entries[lastIndex];// Move the last entry to the index where the entry to delete ismap._entries[toDeleteIndex] = lastEntry;// Update the index for the moved entrymap._indexes[lastEntry._key] = toDeleteIndex + 1; // All indexes are 1-based// Delete the slot where the moved entry was storedmap._entries.pop();// Delete the index for the deleted slotdelete map._indexes[key];return true;} else {return false;}}/*** @dev Returns true if the key is in the map. O(1).*/function _contains(Map storage map, bytes32 key) private view returns (bool) {return map._indexes[key] != 0;}/*** @dev Returns the number of key-value pairs in the map. O(1).*/function _length(Map storage map) private view returns (uint256) {return map._entries.length;}/*** @dev Returns the key-value pair stored at position `index` in the map. O(1).** Note that there are no guarantees on the ordering of entries inside the* array, and it may change when more entries are added or removed.** Requirements:** - `index` must be strictly less than {length}.*/function _at(Map storage map, uint256 index) private view returns (bytes32, bytes32) {require(map._entries.length > index, "EnumerableMap: index out of bounds");MapEntry storage entry = map._entries[index];return (entry._key, entry._value);}/*** @dev Tries to returns the value associated with `key`.  O(1).* Does not revert if `key` is not in the map.*/function _tryGet(Map storage map, bytes32 key) private view returns (bool, bytes32) {uint256 keyIndex = map._indexes[key];if (keyIndex == 0) return (false, 0); // Equivalent to contains(map, key)return (true, map._entries[keyIndex - 1]._value); // All indexes are 1-based}/*** @dev Returns the value associated with `key`.  O(1).** Requirements:** - `key` must be in the map.*/function _get(Map storage map, bytes32 key) private view returns (bytes32) {uint256 keyIndex = map._indexes[key];require(keyIndex != 0, "EnumerableMap: nonexistent key"); // Equivalent to contains(map, key)return map._entries[keyIndex - 1]._value; // All indexes are 1-based}/*** @dev Same as {_get}, with a custom error message when `key` is not in the map.** CAUTION: This function is deprecated because it requires allocating memory for the error* message unnecessarily. For custom revert reasons use {_tryGet}.*/function _get(Map storage map, bytes32 key, string memory errorMessage) private view returns (bytes32) {uint256 keyIndex = map._indexes[key];require(keyIndex != 0, errorMessage); // Equivalent to contains(map, key)return map._entries[keyIndex - 1]._value; // All indexes are 1-based}// UintToAddressMapstruct UintToAddressMap {Map _inner;}/*** @dev Adds a key-value pair to a map, or updates the value for an existing* key. O(1).** Returns true if the key was added to the map, that is if it was not* already present.*/function set(UintToAddressMap storage map, uint256 key, address value) internal returns (bool) {return _set(map._inner, bytes32(key), bytes32(uint256(uint160(value))));}/*** @dev Removes a value from a set. O(1).** Returns true if the key was removed from the map, that is if it was present.*/function remove(UintToAddressMap storage map, uint256 key) internal returns (bool) {return _remove(map._inner, bytes32(key));}/*** @dev Returns true if the key is in the map. O(1).*/function contains(UintToAddressMap storage map, uint256 key) internal view returns (bool) {return _contains(map._inner, bytes32(key));}/*** @dev Returns the number of elements in the map. O(1).*/function length(UintToAddressMap storage map) internal view returns (uint256) {return _length(map._inner);}/*** @dev Returns the element stored at position `index` in the set. O(1).* Note that there are no guarantees on the ordering of values inside the* array, and it may change when more values are added or removed.** Requirements:** - `index` must be strictly less than {length}.*/function at(UintToAddressMap storage map, uint256 index) internal view returns (uint256, address) {(bytes32 key, bytes32 value) = _at(map._inner, index);return (uint256(key), address(uint160(uint256(value))));}/*** @dev Tries to returns the value associated with `key`.  O(1).* Does not revert if `key` is not in the map.** _Available since v3.4._*/function tryGet(UintToAddressMap storage map, uint256 key) internal view returns (bool, address) {(bool success, bytes32 value) = _tryGet(map._inner, bytes32(key));return (success, address(uint160(uint256(value))));}/*** @dev Returns the value associated with `key`.  O(1).** Requirements:** - `key` must be in the map.*/function get(UintToAddressMap storage map, uint256 key) internal view returns (address) {return address(uint160(uint256(_get(map._inner, bytes32(key)))));}/*** @dev Same as {get}, with a custom error message when `key` is not in the map.** CAUTION: This function is deprecated because it requires allocating memory for the error* message unnecessarily. For custom revert reasons use {tryGet}.*/function get(UintToAddressMap storage map, uint256 key, string memory errorMessage) internal view returns (address) {return address(uint160(uint256(_get(map._inner, bytes32(key), errorMessage))));}
}/*** @dev String operations.*/
library Strings {/*** @dev Converts a `uint256` to its ASCII `string` representation.*/function toString(uint256 value) internal pure returns (string memory) {// Inspired by OraclizeAPI's implementation - MIT licence// https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.solif (value == 0) {return "0";}uint256 temp = value;uint256 digits;while (temp != 0) {digits++;temp /= 10;}bytes memory buffer = new bytes(digits);uint256 index = digits - 1;temp = value;while (temp != 0) {buffer[index--] = bytes1(uint8(48 + temp % 10));temp /= 10;}return string(buffer);}
}/*** @title ERC721 Non-Fungible Token Standard basic implementation* @dev see https://eips.ethereum.org/EIPS/eip-721*/
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Enumerable {using SafeMath for uint256;using Address for address;using EnumerableSet for EnumerableSet.UintSet;using EnumerableMap for EnumerableMap.UintToAddressMap;using Strings for uint256;// Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`// which can be also obtained as `IERC721Receiver(0).onERC721Received.selector`bytes4 private constant _ERC721_RECEIVED = 0x150b7a02;// Mapping from holder address to their (enumerable) set of owned tokensmapping (address => EnumerableSet.UintSet) private _holderTokens;// Enumerable mapping from token ids to their ownersEnumerableMap.UintToAddressMap private _tokenOwners;// Mapping from token ID to approved addressmapping (uint256 => address) private _tokenApprovals;// Mapping from owner to operator approvalsmapping (address => mapping (address => bool)) private _operatorApprovals;// Token namestring private _name;// Token symbolstring private _symbol;// Optional mapping for token URIsmapping (uint256 => string) private _tokenURIs;// Base URIstring private _baseURI;/**     bytes4(keccak256('balanceOf(address)')) == 0x70a08231*     bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e*     bytes4(keccak256('approve(address,uint256)')) == 0x095ea7b3*     bytes4(keccak256('getApproved(uint256)')) == 0x081812fc*     bytes4(keccak256('setApprovalForAll(address,bool)')) == 0xa22cb465*     bytes4(keccak256('isApprovedForAll(address,address)')) == 0xe985e9c5*     bytes4(keccak256('transferFrom(address,address,uint256)')) == 0x23b872dd*     bytes4(keccak256('safeTransferFrom(address,address,uint256)')) == 0x42842e0e*     bytes4(keccak256('safeTransferFrom(address,address,uint256,bytes)')) == 0xb88d4fde**     => 0x70a08231 ^ 0x6352211e ^ 0x095ea7b3 ^ 0x081812fc ^*        0xa22cb465 ^ 0xe985e9c5 ^ 0x23b872dd ^ 0x42842e0e ^ 0xb88d4fde == 0x80ac58cd*/bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;/**     bytes4(keccak256('name()')) == 0x06fdde03*     bytes4(keccak256('symbol()')) == 0x95d89b41*     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd**     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f*/bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;/**     bytes4(keccak256('totalSupply()')) == 0x18160ddd*     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59*     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7**     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63*/bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;/*** @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.*/constructor (string memory name_, string memory symbol_) public {_name = name_;_symbol = symbol_;// register the supported interfaces to conform to ERC721 via ERC165_registerInterface(_INTERFACE_ID_ERC721);_registerInterface(_INTERFACE_ID_ERC721_METADATA);_registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);}/*** @dev See {IERC721-balanceOf}.*/function balanceOf(address owner) public view virtual override returns (uint256) {require(owner != address(0), "ERC721: balance query for the zero address");return _holderTokens[owner].length();}/*** @dev See {IERC721-ownerOf}.*/function ownerOf(uint256 tokenId) public view virtual override returns (address) {return _tokenOwners.get(tokenId, "ERC721: owner query for nonexistent token");}/*** @dev See {IERC721Metadata-name}.*/function name() public view virtual override returns (string memory) {return _name;}/*** @dev See {IERC721Metadata-symbol}.*/function symbol() public view virtual override returns (string memory) {return _symbol;}/*** @dev See {IERC721Metadata-tokenURI}.*/function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");string memory _tokenURI = _tokenURIs[tokenId];string memory base = baseURI();// If there is no base URI, return the token URI.if (bytes(base).length == 0) {return _tokenURI;}// If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).if (bytes(_tokenURI).length > 0) {return string(abi.encodePacked(base, _tokenURI, '.json'));}// If there is a baseURI but no tokenURI, concatenate the tokenID to the baseURI.return string(abi.encodePacked(base, (tokenId.toString()),".txt"));}/*** @dev Returns the base URI set via {_setBaseURI}. This will be* automatically added as a prefix in {tokenURI} to each token's URI, or* to the token ID if no specific URI is set for that token ID.*/function baseURI() public view virtual returns (string memory) {return _baseURI;}/*** @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.*/function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns (uint256) {return _holderTokens[owner].at(index);}/*** @dev See {IERC721Enumerable-totalSupply}.*/function totalSupply() public view virtual override returns (uint256) {// _tokenOwners are indexed by tokenIds, so .length() returns the number of tokenIdsreturn _tokenOwners.length();}/*** @dev See {IERC721Enumerable-tokenByIndex}.*/function tokenByIndex(uint256 index) public view virtual override returns (uint256) {(uint256 tokenId, ) = _tokenOwners.at(index);return tokenId;}/*** @dev See {IERC721-approve}.*/function approve(address to, uint256 tokenId) public virtual override {address owner = ERC721.ownerOf(tokenId);require(to != owner, "ERC721: approval to current owner");require(_msgSender() == owner || ERC721.isApprovedForAll(owner, _msgSender()),"ERC721: approve caller is not owner nor approved for all");_approve(to, tokenId);}/*** @dev See {IERC721-getApproved}.*/function getApproved(uint256 tokenId) public view virtual override returns (address) {require(_exists(tokenId), "ERC721: approved query for nonexistent token");return _tokenApprovals[tokenId];}/*** @dev See {IERC721-setApprovalForAll}.*/function setApprovalForAll(address operator, bool approved) public virtual override {require(operator != _msgSender(), "ERC721: approve to caller");_operatorApprovals[_msgSender()][operator] = approved;emit ApprovalForAll(_msgSender(), operator, approved);}/*** @dev See {IERC721-isApprovedForAll}.*/function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {return _operatorApprovals[owner][operator];}/*** @dev See {IERC721-transferFrom}.*/function transferFrom(address from, address to, uint256 tokenId) public virtual override {//solhint-disable-next-line max-line-lengthrequire(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");_transfer(from, to, tokenId);}/*** @dev See {IERC721-safeTransferFrom}.*/function safeTransferFrom(address from, address to, uint256 tokenId) public virtual override {safeTransferFrom(from, to, tokenId, "");}/*** @dev See {IERC721-safeTransferFrom}.*/function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory _data) public virtual override {require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");_safeTransfer(from, to, tokenId, _data);}/*** @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients* are aware of the ERC721 protocol to prevent tokens from being forever locked.** `_data` is additional data, it has no specified format and it is sent in call to `to`.** This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.* implement alternative mechanisms to perform token transfer, such as signature-based.** Requirements:** - `from` cannot be the zero address.* - `to` cannot be the zero address.* - `tokenId` token must exist and be owned by `from`.* - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.** Emits a {Transfer} event.*/function _safeTransfer(address from, address to, uint256 tokenId, bytes memory _data) internal virtual {_transfer(from, to, tokenId);require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");}/*** @dev Returns whether `tokenId` exists.** Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.** Tokens start existing when they are minted (`_mint`),* and stop existing when they are burned (`_burn`).*/function _exists(uint256 tokenId) internal view virtual returns (bool) {return _tokenOwners.contains(tokenId);}/*** @dev Returns whether `spender` is allowed to manage `tokenId`.** Requirements:** - `tokenId` must exist.*/function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {require(_exists(tokenId), "ERC721: operator query for nonexistent token");address owner = ERC721.ownerOf(tokenId);return (spender == owner || getApproved(tokenId) == spender || ERC721.isApprovedForAll(owner, spender));}/*** @dev Safely mints `tokenId` and transfers it to `to`.** Requirements:d** - `tokenId` must not exist.* - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.** Emits a {Transfer} event.*/function _safeMint(address to, uint256 tokenId) internal virtual {_safeMint(to, tokenId, "");}/*** @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is* forwarded in {IERC721Receiver-onERC721Received} to contract recipients.*/function _safeMint(address to, uint256 tokenId, bytes memory _data) internal virtual {_mint(to, tokenId);require(_checkOnERC721Received(address(0), to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");}/*** @dev Mints `tokenId` and transfers it to `to`.** WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible** Requirements:** - `tokenId` must not exist.* - `to` cannot be the zero address.** Emits a {Transfer} event.*/function _mint(address to, uint256 tokenId) internal virtual {require(to != address(0), "ERC721: mint to the zero address");require(!_exists(tokenId), "ERC721: token already minted");_beforeTokenTransfer(address(0), to, tokenId);_holderTokens[to].add(tokenId);_tokenOwners.set(tokenId, to);emit Transfer(address(0), to, tokenId);}/*** @dev Destroys `tokenId`.* The approval is cleared when the token is burned.** Requirements:** - `tokenId` must exist.** Emits a {Transfer} event.*/function _burn(uint256 tokenId) internal virtual {address owner = ERC721.ownerOf(tokenId); // internal owner_beforeTokenTransfer(owner, address(0), tokenId);// Clear approvals_approve(address(0), tokenId);// Clear metadata (if any)if (bytes(_tokenURIs[tokenId]).length != 0) {delete _tokenURIs[tokenId];}_holderTokens[owner].remove(tokenId);_tokenOwners.remove(tokenId);emit Transfer(owner, address(0), tokenId);}/*** @dev Transfers `tokenId` from `from` to `to`.*  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.** Requirements:** - `to` cannot be the zero address.* - `tokenId` token must be owned by `from`.** Emits a {Transfer} event.*/function _transfer(address from, address to, uint256 tokenId) internal virtual {require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer of token that is not own"); // internal ownerrequire(to != address(0), "ERC721: transfer to the zero address");_beforeTokenTransfer(from, to, tokenId);// Clear approvals from the previous owner_approve(address(0), tokenId);_holderTokens[from].remove(tokenId);_holderTokens[to].add(tokenId);_tokenOwners.set(tokenId, to);emit Transfer(from, to, tokenId);}/*** @dev Sets `_tokenURI` as the tokenURI of `tokenId`.** Requirements:** - `tokenId` must exist.*/function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {require(_exists(tokenId), "ERC721Metadata: URI set of nonexistent token");_tokenURIs[tokenId] = _tokenURI;}/*** @dev Internal function to set the base URI for all token IDs. It is* automatically added as a prefix to the value returned in {tokenURI},* or to the token ID if {tokenURI} is empty.*/function _setBaseURI(string memory baseURI_) internal virtual {_baseURI = baseURI_;}/*** @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.* The call is not executed if the target address is not a contract.** @param from address representing the previous owner of the given token ID* @param to target address that will receive the tokens* @param tokenId uint256 ID of the token to be transferred* @param _data bytes optional data to send along with the call* @return bool whether the call correctly returned the expected magic value*/function _checkOnERC721Received(address from, address to, uint256 tokenId, bytes memory _data)private returns (bool){if (!to.isContract()) {return true;}bytes memory returndata = to.functionCall(abi.encodeWithSelector(IERC721Receiver(to).onERC721Received.selector,_msgSender(),from,tokenId,_data), "ERC721: transfer to non ERC721Receiver implementer");bytes4 retval = abi.decode(returndata, (bytes4));return (retval == _ERC721_RECEIVED);}/*** @dev Approve `to` to operate on `tokenId`** Emits an {Approval} event.*/function _approve(address to, uint256 tokenId) internal virtual {_tokenApprovals[tokenId] = to;emit Approval(ERC721.ownerOf(tokenId), to, tokenId); // internal owner}/*** @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 { }
}/*** @dev Contract module which provides a basic access control mechanism, where* there is an account (an owner) that can be granted exclusive access to* specific functions.** By default, the owner account will be the one that deploys the contract. This* can later be changed with {transferOwnership}.** This module is used through inheritance. It will make available the modifier* `onlyOwner`, which can be applied to your functions to restrict their use to* the owner.*/
abstract contract Ownable is Context {address private _owner;event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);/*** @dev Initializes the contract setting the deployer as the initial owner.*/constructor () internal {address msgSender = _msgSender();_owner = msgSender;emit OwnershipTransferred(address(0), msgSender);}/*** @dev Returns the address of the current owner.*/function owner() public view virtual returns (address) {return _owner;}/*** @dev Throws if called by any account other than the owner.*/modifier onlyOwner() {require(owner() == _msgSender(), "Ownable: caller is not the owner");_;}/*** @dev Leaves the contract without owner. It will not be possible to call* `onlyOwner` functions anymore. Can only be called by the current owner.** NOTE: Renouncing ownership will leave the contract without an owner,* thereby removing any functionality that is only available to the owner.*/function renounceOwnership() public virtual onlyOwner {emit OwnershipTransferred(_owner, address(0));_owner = address(0);}/*** @dev Transfers ownership of the contract to a new account (`newOwner`).* Can only be called by the current owner.*/function transferOwnership(address newOwner) public virtual onlyOwner {require(newOwner != address(0), "Ownable: new owner is the zero address");emit OwnershipTransferred(_owner, newOwner);_owner = newOwner;}
}contract KILLAz is ERC721, Ownable {using SafeMath for uint256;uint256 public immutable pricePerKILLA;uint256 public immutable maxPerTx;uint256 public immutable maxKILLAz;bool public isSaleActive;address private immutable reserveAddress;constructor(address _reserveAddress)publicERC721("KILLAz", "Kz"){pricePerKILLA = 0.029 * 10 ** 18;maxPerTx = 20;maxKILLAz = 9971;reserveAddress = _reserveAddress;}function flipSaleState() public onlyOwner {isSaleActive = !isSaleActive;}function setBaseURI(string memory baseURI) public onlyOwner {_setBaseURI(baseURI);}function reserveKILLAz() public onlyOwner {   require(totalSupply() < 100);for (uint256 i = 0; i < 50; i++) {uint256 mintIndex = totalSupply();_safeMint(reserveAddress, mintIndex);}}function mintKILLAz(uint256 numberOfTokens) public payable {require(isSaleActive, "Sale is not active");require(numberOfTokens <= maxPerTx, "No more than 20 tokens per transaction");require(totalSupply().add(numberOfTokens) <= maxKILLAz, "Purchase would exceed max supply of KILLAz");require(pricePerKILLA.mul(numberOfTokens) == msg.value, "Ether value is not correct");payable(owner()).transfer(msg.value);for (uint256 i = 0; i < numberOfTokens; i++) {uint256 mintIndex = totalSupply();if (totalSupply() < maxKILLAz) {_safeMint(msg.sender, mintIndex);}}}
}