// Contract: Gunx
// Target function: function transferFrom(
 (e.g. 0, 1, 2, 3, ...)
* starting from `_startTokenId()`.
*
* Assumptions:
*
* - An owner cannot have more than 2**64 - 1 (max value of uint64) of supply.
* - The maximum token ID cannot exceed 2**256 - 1 (max value of uint256).
*/

contract ERC721A is IERC721A {
// Bypass for a `--via-ir` bug (https://github.com/chiru-labs/ERC721A/pull/364).
struct TokenApprovalRef {
	address value;
}

// =============================================================
//                           CONSTANTS
// =============================================================

// Mask of an entry in packed address data.
uint256 private constant _BITMASK_ADDRESS_DATA_ENTRY = (1 << 64) - 1;

// The bit position of `numberMinted` in packed address data.
uint256 private constant _BITPOS_NUMBER_MINTED = 64;

// The bit position of `numberBurned` in packed address data.
uint256 private constant _BITPOS_NUMBER_BURNED = 128;

// The bit position of `aux` in packed address data.
uint256 private constant _BITPOS_AUX = 192;

// Mask of all 256 bits in packed address data except the 64 bits for `aux`.
uint256 private constant _BITMASK_AUX_COMPLEMENT = (1 << 192) - 1;

// The bit position of `startTimestamp` in packed ownership.
uint256 private constant _BITPOS_START_TIMESTAMP = 160;

// The bit mask of the `burned` bit in packed ownership.
uint256 private constant _BITMASK_BURNED = 1 << 224;

// The bit position of the `nextInitialized` bit in packed ownership.
uint256 private constant _BITPOS_NEXT_INITIALIZED = 225;

// The bit mask of the `nextInitialized` bit in packed ownership.
uint256 private constant _BITMASK_NEXT_INITIALIZED = 1 << 225;

// The bit position of `extraData` in packed ownership.
uint256 private constant _BITPOS_EXTRA_DATA = 232;

// Mask of all 256 bits in a packed ownership except the 24 bits for `extraData`.
uint256 private constant _BITMASK_EXTRA_DATA_COMPLEMENT = (1 << 232) - 1;

// The mask of the lower 160 bits for addresses.
uint256 private constant _BITMASK_ADDRESS = (1 << 160) - 1;

// The maximum `quantity` that can be minted with {_mintERC2309}.
// This limit is to prevent overflows on the address data entries.
// For a limit of 5000, a total of 3.689e15 calls to {_mintERC2309}
// is required to cause an overflow, which is unrealistic.
uint256 private constant _MAX_MINT_ERC2309_QUANTITY_LIMIT = 5000;

// The `Transfer` event signature is given by:
// `keccak256(bytes("Transfer(address,address,uint256)"))`.
bytes32 private constant _TRANSFER_EVENT_SIGNATURE =
	0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef;

// =============================================================
//                            STORAGE
// =============================================================

// The next token ID to be minted.
uint256 private _currentIndex;

// The number of tokens burned.
uint256 private _burnCounter;

// Token name
//    string private _name;

// Token symbol
//    string private _symbol;

// Mapping from token ID to ownership details
// An empty struct value does not necessarily mean the token is unowned.
// See {_packedOwnershipOf} implementation for details.
//
// Bits Layout:
// - [0..159]   `addr`
// - [160..223] `startTimestamp`
// - [224]      `burned`
// - [225]      `nextInitialized`
// - [232..255] `extraData`
mapping(uint256 => uint256) private _packedOwnerships;

// Mapping owner address to address data.
//
// Bits Layout:
// - [0..63]    `balance`
// - [64..127]  `numberMinted`
// - [128..191] `numberBurned`
// - [192..255] `aux`
mapping(address => uint256) private _packedAddressData;

// Mapping from token ID to approved address.
mapping(uint256 => TokenApprovalRef) private _tokenApprovals;

// Mapping from owner to operator approvals
mapping(address => mapping(address => bool)) private _operatorApprovals;

// =============================================================
//                          CONSTRUCTOR
// =============================================================


constructor() {
	_currentIndex = _startTokenId();
}

// =============================================================
//                   TOKEN COUNTING OPERATIONS
// =============================================================

/**
 * @dev Returns the starting token ID.
 * To change the starting token ID, please override this function.
 */
function _startTokenId() internal view virtual returns (uint256) {
	return 1;
}

/**
 * @dev Returns the next token ID to be minted.
 */
function _nextTokenId() internal view virtual returns (uint256) {
	return _currentIndex;
}

/**
 * @dev Returns the total number of tokens in existence.
 * Burned tokens will reduce the count.
 * To get the total number of tokens minted, please see {_totalMinted}.
 */
function totalSupply() public view virtual override returns (uint256) {
	// Counter underflow is impossible as _burnCounter cannot be incremented
	// more than `_currentIndex - _startTokenId()` times.
	unchecked {
		return _currentIndex - _burnCounter - _startTokenId();
	}
}

/**
 * @dev Returns the total amount of tokens minted in the contract.
 */
function _totalMinted() internal view virtual returns (uint256) {
	// Counter underflow is impossible as `_currentIndex` does not decrement,
	// and it is initialized to `_startTokenId()`.
	unchecked {
		return _currentIndex - _startTokenId();
	}
}

/**
 * @dev Returns the total number of tokens burned.
 */
function _totalBurned() internal view virtual returns (uint256) {
	return _burnCounter;
}

// =============================================================
//                    ADDRESS DATA OPERATIONS
// =============================================================

/**
 * @dev Returns the number of tokens in `owner`'s account.
 */
function balanceOf(address owner) public view virtual override returns (uint256) {
	if (owner == address(0)) revert BalanceQueryForZeroAddress();
	return _packedAddressData[owner] & _BITMASK_ADDRESS_DATA_ENTRY;
}

/**
 * Returns the number of tokens minted by `owner`.
 */
function _numberMinted(address owner) internal view returns (uint256) {
	return (_packedAddressData[owner] >> _BITPOS_NUMBER_MINTED) & _BITMASK_ADDRESS_DATA_ENTRY;
}

/**
 * Returns the number of tokens burned by or on behalf of `owner`.
 */
function _numberBurned(address owner) internal view returns (uint256) {
	return (_packedAddressData[owner] >> _BITPOS_NUMBER_BURNED) & _BITMASK_ADDRESS_DATA_ENTRY;
}

/**
 * Returns the auxiliary data for `owner`. (e.g. number of whitelist mint slots used).
 */
function _getAux(address owner) internal view returns (uint64) {
	return uint64(_packedAddressData[owner] >> _BITPOS_AUX);
}

/**
 * Sets the auxiliary data for `owner`. (e.g. number of whitelist mint slots used).
 * If there are multiple variables, please pack them into a uint64.
 */
function _setAux(address owner, uint64 aux) internal virtual {
	uint256 packed = _packedAddressData[owner];
	uint256 auxCasted;
	// Cast `aux` with assembly to avoid redundant masking.
	assembly {
		auxCasted := aux
	}
	packed = (packed & _BITMASK_AUX_COMPLEMENT) | (auxCasted << _BITPOS_AUX);
	_packedAddressData[owner] = packed;
}

// =============================================================
//                            IERC165
// =============================================================

/**
 * @dev Returns true if this contract implements the interface defined by
 * `interfaceId`. See the corresponding
 * [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)
 * to learn more about how these ids are created.
 *
 * This function call must use less than 30000 gas.
 */
function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
	// The interface IDs are constants representing the first 4 bytes
	// of the XOR of all function selectors in the interface.
	// See: [ERC165](https://eips.ethereum.org/EIPS/eip-165)
	// (e.g. `bytes4(i.functionA.selector ^ i.functionB.selector ^ ...)`)
	return
		interfaceId == 0x01ffc9a7 || // ERC165 interface ID for ERC165.
		interfaceId == 0x80ac58cd || // ERC165 interface ID for ERC721.
		interfaceId == 0x5b5e139f; // ERC165 interface ID for ERC721Metadata.
}

// =============================================================
//                        IERC721Metadata
// =============================================================

/**
 * @dev Returns the token collection name.
 */
 
function name() public view virtual override returns (string memory) {
	return '';
}


function symbol() public view virtual override returns (string memory) {
	return '';
}



/**
 * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
 */
function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
	if (!_exists(tokenId)) revert URIQueryForNonexistentToken();

	string memory baseURI = _baseURI();
	return bytes(baseURI).length != 0 ? string(abi.encodePacked('ipfs://', baseURI, '/', _toString(tokenId), '.json')) : '';
}

/**
 * @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, it can be overridden in child contracts.
 */
function _baseURI() internal view virtual returns (string memory) {
	return '';
}

// =============================================================
//                     OWNERSHIPS OPERATIONS
// =============================================================

/**
 * @dev Returns the owner of the `tokenId` token.
 *
 * Requirements:
 *
 * - `tokenId` must exist.
 */
function ownerOf(uint256 tokenId) public view virtual override returns (address) {
	return address(uint160(_packedOwnershipOf(tokenId)));
}

/**
 * @dev Gas spent here starts off proportional to the maximum mint batch size.
 * It gradually moves to O(1) as tokens get transferred around over time.
 */
function _ownershipOf(uint256 tokenId) internal view virtual returns (TokenOwnership memory) {
	return _unpackedOwnership(_packedOwnershipOf(tokenId));
}

/**
 * @dev Returns the unpacked `TokenOwnership` struct at `index`.
 */
function _ownershipAt(uint256 index) internal view virtual returns (TokenOwnership memory) {
	return _unpackedOwnership(_packedOwnerships[index]);
}

/**
 * @dev Initializes the ownership slot minted at `index` for efficiency purposes.
 */
function _initializeOwnershipAt(uint256 index) internal virtual {
	if (_packedOwnerships[index] == 0) {
		_packedOwnerships[index] = _packedOwnershipOf(index);
	}
}

/**
 * Returns the packed ownership data of `tokenId`.
 */
function _packedOwnershipOf(uint256 tokenId) private view returns (uint256) {
	uint256 curr = tokenId;

	unchecked {
		if (_startTokenId() <= curr)
			if (curr < _currentIndex) {
				uint256 packed = _packedOwnerships[curr];
				// If not burned.
				if (packed & _BITMASK_BURNED == 0) {
					// Invariant:
					// There will always be an initialized ownership slot
					// (i.e. `ownership.addr != address(0) && ownership.burned == false`)
					// before an unintialized ownership slot
					// (i.e. `ownership.addr == address(0) && ownership.burned == false`)
					// Hence, `curr` will not underflow.
					//
					// We can directly compare the packed value.
					// If the address is zero, packed will be zero.
					while (packed == 0) {
						packed = _packedOwnerships[--curr];
					}
					return packed;
				}
			}
	}
	revert OwnerQueryForNonexistentToken();
}

/**
 * @dev Returns the unpacked `TokenOwnership` struct from `packed`.
 */
function _unpackedOwnership(uint256 packed) private pure returns (TokenOwnership memory ownership) {
	ownership.addr = address(uint160(packed));
	ownership.startTimestamp = uint64(packed >> _BITPOS_START_TIMESTAMP);
	ownership.burned = packed & _BITMASK_BURNED != 0;
	ownership.extraData = uint24(packed >> _BITPOS_EXTRA_DATA);
}

/**
 * @dev Packs ownership data into a single uint256.
 */
function _packOwnershipData(address owner, uint256 flags) private view returns (uint256 result) {
	assembly {
		// Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.
		owner := and(owner, _BITMASK_ADDRESS)
		// `owner | (block.timestamp << _BITPOS_START_TIMESTAMP) | flags`.
		result := or(owner, or(shl(_BITPOS_START_TIMESTAMP, timestamp()), flags))
	}
}

/**
 * @dev Returns the `nextInitialized` flag set if `quantity` equals 1.
 */
function _nextInitializedFlag(uint256 quantity) private pure returns (uint256 result) {
	// For branchless setting of the `nextInitialized` flag.
	assembly {
		// `(quantity == 1) << _BITPOS_NEXT_INITIALIZED`.
		result := shl(_BITPOS_NEXT_INITIALIZED, eq(quantity, 1))
	}
}

// =============================================================
//                      APPROVAL OPERATIONS
// =============================================================

/**
 * @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) public payable virtual override {
	address owner = ownerOf(tokenId);

	if (_msgSenderERC721A() != owner)
		if (!isApprovedForAll(owner, _msgSenderERC721A())) {
			revert ApprovalCallerNotOwnerNorApproved();
		}

	_tokenApprovals[tokenId].value = to;
	emit Approval(owner, to, tokenId);
}

/**
 * @dev Returns the account approved for `tokenId` token.
 *
 * Requirements:
 *
 * - `tokenId` must exist.
 */
function getApproved(uint256 tokenId) public view virtual override returns (address) {
	if (!_exists(tokenId)) revert ApprovalQueryForNonexistentToken();

	return _tokenApprovals[tokenId].value;
}

/**
 * @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) public virtual override {
	_operatorApprovals[_msgSenderERC721A()][operator] = approved;
	emit ApprovalForAll(_msgSenderERC721A(), operator, approved);
}

/**
 * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
 *
 * See {setApprovalForAll}.
 */
function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
	return _operatorApprovals[owner][operator];
}

/**
 * @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. See {_mint}.
 */
function _exists(uint256 tokenId) internal view virtual returns (bool) {
	return
		_startTokenId() <= tokenId &&
		tokenId < _currentIndex && // If within bounds,
		_packedOwnerships[tokenId] & _BITMASK_BURNED == 0; // and not burned.
}

/**
 * @dev Returns whether `msgSender` is equal to `approvedAddress` or `owner`.
 */
function _isSenderApprovedOrOwner(
	address approvedAddress,
	address owner,
	address msgSender
) private pure returns (bool result) {
	assembly {
		// Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.
		owner := and(owner, _BITMASK_ADDRESS)
		// Mask `msgSender` to the lower 160 bits, in case the upper bits somehow aren't clean.
		msgSender := and(msgSender, _BITMASK_ADDRESS)
		// `msgSender == owner || msgSender == approvedAddress`.
		result := or(eq(msgSender, owner), eq(msgSender, approvedAddress))
	}
}

/**
 * @dev Returns the storage slot and value for the approved address of `tokenId`.
 */
function _getApprovedSlotAndAddress(uint256 tokenId)
	private
	view
	returns (uint256 approvedAddressSlot, address approvedAddress)
{
	TokenApprovalRef storage tokenApproval = _tokenApprovals[tokenId];
	// The following is equivalent to `approvedAddress = _tokenApprovals[tokenId].value`.
	assembly {
		approvedAddressSlot := tokenApproval.slot
		approvedAddress := sload(approvedAddressSlot)
	}
}

// =============================================================
//                      TRANSFER OPERATIONS
// =============================================================