// File: contracts/BurnKing.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.7;

import '@openzeppelin/contracts/utils/Strings.sol';
import '@openzeppelin/contracts/access/Ownable.sol';
import './ERC721AOptimized.sol';
import './IERC20Burnable.sol';

contract BurnKing is ERC721AOptimized, Ownable {
	address public publicKey;

	uint256 maxSupply = 10000;

	// Mapping from owner to list of owned token IDs
	mapping(address => mapping(uint256 => uint256)) private _ownedTokens;

	event BurnedEther(address indexed user, uint256 indexed amount, uint256 indexed totalMinted);

	event tokenMintedFor(address mintedFor, uint256 tokenId);

	constructor(address _publicKey) ERC721AOptimized('Burn King', 'BK') {
		publicKey = _publicKey;
	}

	function burnEther(
		bytes calldata _signature,
		uint256 _tokenCount,
		uint256 _expiredDateInSeconds,
		uint256 _usdCost
	) external payable {
		// Burn delay is now calculated on backend
		require(_expiredDateInSeconds >= block.timestamp, 'Transaction expired');
		require(msg.value >= _tokenCount, 'You do not have enough ethers');

		checkParamsVerification(_signature, concatParamsEth(_tokenCount, _expiredDateInSeconds, _usdCost));

		(bool sent, ) = address(0).call{value: _tokenCount}('');
		require(sent, 'Failed to burn Tokens');

		if (_usdCost >= 10) {
			mint();
		}

		emit BurnedEther(msg.sender, _usdCost, _totalMinted());
	}

	function burnERC20(
		bytes calldata _signature,
		uint256 _tokenCount,
		uint256 _expiredDateInSeconds,
		uint256 _usdCost,
		address _tokenContractAddress
	) external {
		require(_expiredDateInSeconds >= block.timestamp, 'Transaction expired');

		checkParamsVerification(
			_signature,
			concatParamsERC(_tokenCount, _expiredDateInSeconds, _usdCost, _tokenContractAddress)
		);

		IERC20Burnable(_tokenContractAddress).transferFrom(msg.sender, address(this), _tokenCount);
		IERC20Burnable(_tokenContractAddress).burn(_tokenCount);

		if (_usdCost >= 10) {
			mint();
		}

		emit BurnedEther(msg.sender, _usdCost, _totalMinted());
	}

	function mint() internal {
		require(_totalMinted() + 1 <= maxSupply, 'No more available NFTs');

		_ownedTokens[msg.sender][balanceOf(msg.sender)] = _currentIndex;
		_mint(msg.sender, 1, '', true);

		emit tokenMintedFor(msg.sender, _currentIndex - 1);
	}

	function tokenOfOwnerByIndex(address owner, uint256 index) public view returns (uint256) {
		require(index < balanceOf(owner), 'Owner index out of bounds');
		return _ownedTokens[owner][index];
	}

	function _baseURI() internal pure override returns (string memory) {
		return 'https://burnking.io/api/meta/';
	}

	function checkParamsVerification(bytes memory _signature, string memory _concatenatedParams) public view {
		(bytes32 r, bytes32 s, uint8 v) = splitSignature(_signature);
		require(verifyMessage(_concatenatedParams, v, r, s) == publicKey, 'Your signature is not valid');
	}

	function splitSignature(bytes memory _signature)
		public
		pure
		returns (
			bytes32 r,
			bytes32 s,
			uint8 v
		)
	{
		require(_signature.length == 65, 'invalid signature length');
		assembly {
			r := mload(add(_signature, 32))
			s := mload(add(_signature, 64))
			v := byte(0, mload(add(_signature, 96)))
		}
	}

	function verifyMessage(
		string memory _concatenatedParams,
		uint8 _v,
		bytes32 _r,
		bytes32 _s
	) public pure returns (address) {
		return
			ecrecover(
				keccak256(
					abi.encodePacked(
						'\x19Ethereum Signed Message:\n',
						Strings.toString(bytes(_concatenatedParams).length),
						_concatenatedParams
					)
				),
				_v,
				_r,
				_s
			);
	}

	function concatParamsEth(
		uint256 _tokenCount,
		uint256 _timestamp,
		uint256 _usdCost
	) public pure returns (string memory) {
		return
			string(
				abi.encodePacked(
					Strings.toString(_tokenCount),
					Strings.toString(_timestamp),
					Strings.toString(_usdCost)
				)
			);
	}

	function concatParamsERC(
		uint256 _tokenCount,
		uint256 _timestamp,
		uint256 _usdCost,
		address _contractAddress
	) public pure returns (string memory) {
		return
			string(
				abi.encodePacked(
					Strings.toString(_tokenCount),
					Strings.toString(_timestamp),
					Strings.toString(_usdCost),
					_addressToString(_contractAddress)
				)
			);
	}

	function _addressToString(address _addr) internal pure returns (string memory) {
		bytes memory addressBytes = abi.encodePacked(_addr);

		bytes memory stringBytes = new bytes(42);

		stringBytes[0] = '0';
		stringBytes[1] = 'x';

		for (uint256 i = 0; i < 20; i++) {
			uint8 leftValue = uint8(addressBytes[i]) / 16;
			uint8 rightValue = uint8(addressBytes[i]) - 16 * leftValue;

			bytes1 leftChar = leftValue < 10 ? bytes1(leftValue + 48) : bytes1(leftValue + 87);
			bytes1 rightChar = rightValue < 10 ? bytes1(rightValue + 48) : bytes1(rightValue + 87);

			stringBytes[2 * i + 3] = rightChar;
			stringBytes[2 * i + 2] = leftChar;
		}

		return string(stringBytes);
	}
}

// File: @openzeppelin/contracts/utils/Strings.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Strings.sol)

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

        if (value == 0) {
            return "0";
        }
        uint256 temp = value;
        uint256 digits;
        while (temp != 0) {
            digits++;
            temp /= 10;
        }
        bytes memory buffer = new bytes(digits);
        while (value != 0) {
            digits -= 1;
            buffer[digits] = bytes1(uint8(48 + uint256(value % 10)));
            value /= 10;
        }
        return string(buffer);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        if (value == 0) {
            return "0x00";
        }
        uint256 temp = value;
        uint256 length = 0;
        while (temp != 0) {
            length++;
            temp >>= 8;
        }
        return toHexString(value, length);
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
     */
    function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
        bytes memory buffer = new bytes(2 * length + 2);
        buffer[0] = "0";
        buffer[1] = "x";
        for (uint256 i = 2 * length + 1; i > 1; --i) {
            buffer[i] = _HEX_SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

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() {
        _transferOwnership(_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 {
        _transferOwnership(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");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: contracts/ERC721AOptimized.sol



// SPDX-License-Identifier: MIT
// Creator: Chiru Labs

pragma solidity ^0.8.7;

import '@openzeppelin/contracts/token/ERC721/IERC721.sol';
import '@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol';
import '@openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol';
import '@openzeppelin/contracts/utils/Address.sol';
import '@openzeppelin/contracts/utils/Context.sol';
import '@openzeppelin/contracts/utils/Strings.sol';
import '@openzeppelin/contracts/utils/introspection/ERC165.sol';

error ApprovalCallerNotOwnerNorApproved();
error ApprovalQueryForNonexistentToken();
error ApproveToCaller();
error ApprovalToCurrentOwner();
error BalanceQueryForZeroAddress();
error MintToZeroAddress();
error MintZeroQuantity();
error OwnerQueryForNonexistentToken();
error TransferCallerNotOwnerNorApproved();
error TransferFromIncorrectOwner();
error TransferToNonERC721ReceiverImplementer();
error TransferToZeroAddress();
error URIQueryForNonexistentToken();

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension. Built to optimize for lower gas during batch mints.
 *
 * Assumes serials are sequentially minted starting at _startTokenId() (defaults to 0, e.g. 0, 1, 2, 3..).
 *
 * Assumes that an owner cannot have more than 2**64 - 1 (max value of uint64) of supply.
 *
 * Assumes that the maximum token id cannot exceed 2**256 - 1 (max value of uint256).
 */
contract ERC721AOptimized is Context, ERC165, IERC721, IERC721Metadata {
	using Address for address;
	using Strings for uint256;

	// Compiler will pack this into a single 256bit word.
	struct TokenOwnership {
		// The address of the owner.
		address addr;
		// Keeps track of the start time of ownership with minimal overhead for tokenomics.
		uint64 startTimestamp;
		// Whether the token has been burned.
		// bool burned;
	}

	// Compiler will pack this into a single 256bit word.
	struct AddressData {
		// Realistically, 2**64-1 is more than enough.
		uint64 balance;
		// Keeps track of mint count with minimal overhead for tokenomics.
		uint64 numberMinted;
		// Keeps track of burn count with minimal overhead for tokenomics.
		// uint64 numberBurned;
		// For miscellaneous variable(s) pertaining to the address
		// (e.g. number of whitelist mint slots used).
		// If there are multiple variables, please pack them into a uint64.
		uint64 aux;
	}

	// The tokenId of the next token to be minted.
	uint256 internal _currentIndex;

	// The number of tokens burned.
	// uint256 internal _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 _ownershipOf implementation for details.
	mapping(uint256 => TokenOwnership) internal _ownerships;

	// Mapping owner address to address data
	mapping(address => AddressData) private _addressData;

	// 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;

	constructor(string memory name_, string memory symbol_) {
		_name = name_;
		_symbol = symbol_;
		_currentIndex = _startTokenId();
	}

	/**
	 * To change the starting tokenId, please override this function.
	 */
	function _startTokenId() internal view virtual returns (uint256) {
		return 0;
	}

	/**
	 * @dev Burned tokens are calculated here, use _totalMinted() if you want to count just minted tokens.
	 */
	function totalSupply() public view returns (uint256) {
		// Counter underflow is impossible as _burnCounter cannot be incremented
		// more than _currentIndex - _startTokenId() times
		unchecked {
			return
				_currentIndex -
				//  - _burnCounter
				_startTokenId();
		}
	}

	/**
	 * Returns the total amount of tokens minted in the contract.
	 */
	function _totalMinted() internal view returns (uint256) {
		// Counter underflow is impossible as _currentIndex does not decrement,
		// and it is initialized to _startTokenId()
		unchecked {
			return _currentIndex - _startTokenId();
		}
	}

	/**
	 * @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 override returns (uint256) {
		if (owner == address(0)) revert BalanceQueryForZeroAddress();
		return uint256(_addressData[owner].balance);
	}

	/**
	 * Returns the number of tokens minted by `owner`.
	 */
	function _numberMinted(address owner) internal view returns (uint256) {
		return uint256(_addressData[owner].numberMinted);
	}

	/**
	 * Returns the number of tokens burned by or on behalf of `owner`.
	 */
	// function _numberBurned(address owner) internal view returns (uint256) {
	// 	return uint256(_addressData[owner].numberBurned);
	// }

	/**
	 * Returns the auxillary data for `owner`. (e.g. number of whitelist mint slots used).
	 */
	function _getAux(address owner) internal view returns (uint64) {
		return _addressData[owner].aux;
	}

	/**
	 * Sets the auxillary 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 {
		_addressData[owner].aux = aux;
	}

	/**
	 * Gas spent here starts off proportional to the maximum mint batch size.
	 * It gradually moves to O(1) as tokens get transferred around in the collection over time.
	 */
	function _ownershipOf(uint256 tokenId) internal view returns (TokenOwnership memory) {
		uint256 curr = tokenId;

		unchecked {
			if (_startTokenId() <= curr && curr < _currentIndex) {
				TokenOwnership memory ownership = _ownerships[curr];

				if (ownership.addr != address(0)) {
					return ownership;
				}
				// Invariant:
				// There will always be an ownership that has an address and is not burned
				// before an ownership that does not have an address and is not burned.
				// Hence, curr will not underflow.
				while (true) {
					curr--;
					ownership = _ownerships[curr];
					if (ownership.addr != address(0)) {
						return ownership;
					}
				}
			}
		}
		revert OwnerQueryForNonexistentToken();
	}

	/**
	 * @dev See {IERC721-ownerOf}.
	 */
	function ownerOf(uint256 tokenId) public view override returns (address) {
		return _ownershipOf(tokenId).addr;
	}

	/**
	 * @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) {
		if (!_exists(tokenId)) revert URIQueryForNonexistentToken();

		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 override {
		address owner = ERC721AOptimized.ownerOf(tokenId);
		if (to == owner) revert ApprovalToCurrentOwner();

		if (_msgSender() != owner && !isApprovedForAll(owner, _msgSender())) {
			revert ApprovalCallerNotOwnerNorApproved();
		}

		_approve(to, tokenId, owner);
	}

	/**
	 * @dev See {IERC721-getApproved}.
	 */
	function getApproved(uint256 tokenId) public view override returns (address) {
		if (!_exists(tokenId)) revert ApprovalQueryForNonexistentToken();

		return _tokenApprovals[tokenId];
	}

	/**
	 * @dev See {IERC721-setApprovalForAll}.
	 */
	function setApprovalForAll(address operator, bool approved) public virtual override {
		if (operator == _msgSender()) revert ApproveToCaller();

		_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 {
		_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 {
		_transfer(from, to, tokenId);
		if (to.isContract() && !_checkContractOnERC721Received(from, to, tokenId, _data)) {
			revert TransferToNonERC721ReceiverImplementer();
		}
	}

	/**
	 * @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`),
	 */
	function _exists(uint256 tokenId) internal view returns (bool) {
		return _startTokenId() <= tokenId && tokenId < _currentIndex;
		// && !_ownerships[tokenId].burned;
	}

	function _safeMint(address to, uint256 quantity) internal {
		_safeMint(to, quantity, '');
	}

	/**
	 * @dev Safely mints `quantity` tokens and transfers them to `to`.
	 *
	 * Requirements:
	 *
	 * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called for each safe transfer.
	 * - `quantity` must be greater than 0.
	 *
	 * Emits a {Transfer} event.
	 */
	function _safeMint(
		address to,
		uint256 quantity,
		bytes memory _data
	) internal {
		_mint(to, quantity, _data, true);
	}

	/**
	 * @dev Mints `quantity` tokens and transfers them to `to`.
	 *
	 * Requirements:
	 *
	 * - `to` cannot be the zero address.
	 * - `quantity` must be greater than 0.
	 *
	 * Emits a {Transfer} event.
	 */
	function _mint(
		address to,
		uint256 quantity,
		bytes memory _data,
		bool safe
	) internal {
		uint256 startTokenId = _currentIndex;
		if (to == address(0)) revert MintToZeroAddress();
		if (quantity == 0) revert MintZeroQuantity();

		_beforeTokenTransfers(address(0), to, startTokenId, quantity);

		// Overflows are incredibly unrealistic.
		// balance or numberMinted overflow if current value of either + quantity > 1.8e19 (2**64) - 1
		// updatedIndex overflows if _currentIndex + quantity > 1.2e77 (2**256) - 1
		unchecked {
			_addressData[to].balance += uint64(quantity);
			_addressData[to].numberMinted += uint64(quantity);

			_ownerships[startTokenId].addr = to;
			_ownerships[startTokenId].startTimestamp = uint64(block.timestamp);

			uint256 updatedIndex = startTokenId;
			uint256 end = updatedIndex + quantity;

			if (safe && to.isContract()) {
				do {
					emit Transfer(address(0), to, updatedIndex);
					if (!_checkContractOnERC721Received(address(0), to, updatedIndex++, _data)) {
						revert TransferToNonERC721ReceiverImplementer();
					}
				} while (updatedIndex != end);
				// Reentrancy protection
				if (_currentIndex != startTokenId) revert();
			} else {
				do {
					emit Transfer(address(0), to, updatedIndex++);
				} while (updatedIndex != end);
			}
			_currentIndex = updatedIndex;
		}
		_afterTokenTransfers(address(0), to, startTokenId, quantity);
	}

	/**
	 * @dev Transfers `tokenId` from `from` to `to`.
	 *
	 * 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
	) private {
		TokenOwnership memory prevOwnership = _ownershipOf(tokenId);

		if (prevOwnership.addr != from) revert TransferFromIncorrectOwner();

		bool isApprovedOrOwner = (_msgSender() == from ||
			isApprovedForAll(from, _msgSender()) ||
			getApproved(tokenId) == _msgSender());

		if (!isApprovedOrOwner) revert TransferCallerNotOwnerNorApproved();
		if (to == address(0)) revert TransferToZeroAddress();

		_beforeTokenTransfers(from, to, tokenId, 1);

		// Clear approvals from the previous owner
		_approve(address(0), tokenId, from);

		// Underflow of the sender's balance is impossible because we check for
		// ownership above and the recipient's balance can't realistically overflow.
		// Counter overflow is incredibly unrealistic as tokenId would have to be 2**256.
		unchecked {
			_addressData[from].balance -= 1;
			_addressData[to].balance += 1;

			TokenOwnership storage currSlot = _ownerships[tokenId];
			currSlot.addr = to;
			currSlot.startTimestamp = uint64(block.timestamp);

			// If the ownership slot of tokenId+1 is not explicitly set, that means the transfer initiator owns it.
			// Set the slot of tokenId+1 explicitly in storage to maintain correctness for ownerOf(tokenId+1) calls.
			uint256 nextTokenId = tokenId + 1;
			TokenOwnership storage nextSlot = _ownerships[nextTokenId];
			if (nextSlot.addr == address(0)) {
				// This will suffice for checking _exists(nextTokenId),
				// as a burned slot cannot contain the zero address.
				if (nextTokenId != _currentIndex) {
					nextSlot.addr = from;
					nextSlot.startTimestamp = prevOwnership.startTimestamp;
				}
			}
		}

		emit Transfer(from, to, tokenId);
		_afterTokenTransfers(from, to, tokenId, 1);
	}

	/**
	 * @dev This is equivalent to _burn(tokenId, false)
	 */
	// function _burn(uint256 tokenId) internal virtual {
	// 	_burn(tokenId, false);
	// }

	/**
	 * @dev Destroys `tokenId`.
	 * The approval is cleared when the token is burned.
	 *
	 * Requirements:
	 *
	 * - `tokenId` must exist.
	 *
	 * Emits a {Transfer} event.
	 */
	// function _burn(uint256 tokenId, bool approvalCheck) internal virtual {
	// 	TokenOwnership memory prevOwnership = _ownershipOf(tokenId);

	// 	address from = prevOwnership.addr;

	// 	if (approvalCheck) {
	// 		bool isApprovedOrOwner = (_msgSender() == from ||
	// 			isApprovedForAll(from, _msgSender()) ||
	// 			getApproved(tokenId) == _msgSender());

	// 		if (!isApprovedOrOwner) revert TransferCallerNotOwnerNorApproved();
	// 	}

	// 	_beforeTokenTransfers(from, address(0), tokenId, 1);

	// 	// Clear approvals from the previous owner
	// 	_approve(address(0), tokenId, from);

	// 	// Underflow of the sender's balance is impossible because we check for
	// 	// ownership above and the recipient's balance can't realistically overflow.
	// 	// Counter overflow is incredibly unrealistic as tokenId would have to be 2**256.
	// 	unchecked {
	// 		AddressData storage addressData = _addressData[from];
	// 		addressData.balance -= 1;
	// 		addressData.numberBurned += 1;

	// 		// Keep track of who burned the token, and the timestamp of burning.
	// 		TokenOwnership storage currSlot = _ownerships[tokenId];
	// 		currSlot.addr = from;
	// 		currSlot.startTimestamp = uint64(block.timestamp);
	// 		currSlot.burned = true;

	// 		// If the ownership slot of tokenId+1 is not explicitly set, that means the burn initiator owns it.
	// 		// Set the slot of tokenId+1 explicitly in storage to maintain correctness for ownerOf(tokenId+1) calls.
	// 		uint256 nextTokenId = tokenId + 1;
	// 		TokenOwnership storage nextSlot = _ownerships[nextTokenId];
	// 		if (nextSlot.addr == address(0)) {
	// 			// This will suffice for checking _exists(nextTokenId),
	// 			// as a burned slot cannot contain the zero address.
	// 			if (nextTokenId != _currentIndex) {
	// 				nextSlot.addr = from;
	// 				nextSlot.startTimestamp = prevOwnership.startTimestamp;
	// 			}
	// 		}
	// 	}

	// 	emit Transfer(from, address(0), tokenId);
	// 	_afterTokenTransfers(from, address(0), tokenId, 1);

	// 	// Overflow not possible, as _burnCounter cannot be exceed _currentIndex times.
	// 	unchecked {
	// 		_burnCounter++;
	// 	}
	// }

	/**
	 * @dev Approve `to` to operate on `tokenId`
	 *
	 * Emits a {Approval} event.
	 */
	function _approve(
		address to,
		uint256 tokenId,
		address owner
	) private {
		_tokenApprovals[tokenId] = to;
		emit Approval(owner, to, tokenId);
	}

	/**
	 * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target 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 _checkContractOnERC721Received(
		address from,
		address to,
		uint256 tokenId,
		bytes memory _data
	) private returns (bool) {
		try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, _data) returns (bytes4 retval) {
			return retval == IERC721Receiver(to).onERC721Received.selector;
		} catch (bytes memory reason) {
			if (reason.length == 0) {
				revert TransferToNonERC721ReceiverImplementer();
			} else {
				assembly {
					revert(add(32, reason), mload(reason))
				}
			}
		}
	}

	/**
	 * @dev Hook that is called before a set of serially-ordered token ids are about to be transferred. This includes minting.
	 * And also called before burning one token.
	 *
	 * startTokenId - the first token id to be transferred
	 * quantity - the amount to be transferred
	 *
	 * 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, `tokenId` will be burned by `from`.
	 * - `from` and `to` are never both zero.
	 */
	function _beforeTokenTransfers(
		address from,
		address to,
		uint256 startTokenId,
		uint256 quantity
	) internal virtual {}

	/**
	 * @dev Hook that is called after a set of serially-ordered token ids have been transferred. This includes
	 * minting.
	 * And also called after one token has been burned.
	 *
	 * startTokenId - the first token id to be transferred
	 * quantity - the amount to be transferred
	 *
	 * Calling conditions:
	 *
	 * - When `from` and `to` are both non-zero, `from`'s `tokenId` has been
	 * transferred to `to`.
	 * - When `from` is zero, `tokenId` has been minted for `to`.
	 * - When `to` is zero, `tokenId` has been burned by `from`.
	 * - `from` and `to` are never both zero.
	 */
	function _afterTokenTransfers(
		address from,
		address to,
		uint256 startTokenId,
		uint256 quantity
	) internal virtual {}
}

// File: contracts/IERC20Burnable.sol



interface IERC20Burnable {
	function burn(uint256 _amount) external;

	function transferFrom(
		address from,
		address to,
		uint256 amount
	) external returns (bool);
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

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

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

// File: @openzeppelin/contracts/token/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721.sol)

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;
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/IERC721Receiver.sol)

pragma solidity ^0.8.0;

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

// File: @openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Metadata.sol)

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);
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        (bool success, ) = recipient.call{value: amount}("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

    /**
     * @dev Performs a Solidity function call using a low level `call`. A
     * plain `call` is an unsafe replacement for a function call: use this
     * function instead.
     *
     * If `target` reverts with a revert reason, it is bubbled up by this
     * function (like regular Solidity function calls).
     *
     * Returns the raw returned data. To convert to the expected return value,
     * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
     *
     * Requirements:
     *
     * - `target` must be a contract.
     * - calling `target` with `data` must not revert.
     *
     * _Available since v3.1._
     */
    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
     * `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but also transferring `value` wei to `target`.
     *
     * Requirements:
     *
     * - the calling contract must have an ETH balance of at least `value`.
     * - the called Solidity function must be `payable`.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
    }

    /**
     * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
     * with `errorMessage` as a fallback revert reason when `target` reverts.
     *
     * _Available since v3.1._
     */
    function functionCallWithValue(
        address target,
        bytes memory data,
        uint256 value,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(address(this).balance >= value, "Address: insufficient balance for call");
        require(isContract(target), "Address: call to non-contract");

        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/utils/introspection/ERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)

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;
    }
}

// File: @openzeppelin/contracts/utils/introspection/IERC165.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)

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);
}