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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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 Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        _checkOwner();
        _;
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if the sender is not the owner.
     */
    function _checkOwner() internal view virtual {
        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: @openzeppelin/contracts/token/ERC721/ERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.2) (token/ERC721/ERC721.sol)

pragma solidity ^0.8.0;

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

/**
 * @dev Implementation of https://eips.ethereum.org/EIPS/eip-721[ERC721] Non-Fungible Token Standard, including
 * the Metadata extension, but not including the Enumerable extension, which is available separately as
 * {ERC721Enumerable}.
 */
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    using Address for address;
    using Strings for uint256;

    // Token name
    string private _name;

    // Token symbol
    string private _symbol;

    // Mapping from token ID to owner address
    mapping(uint256 => address) private _owners;

    // Mapping owner address to token count
    mapping(address => uint256) private _balances;

    // Mapping from token ID to approved address
    mapping(uint256 => address) private _tokenApprovals;

    // Mapping from owner to operator approvals
    mapping(address => mapping(address => bool)) private _operatorApprovals;

    /**
     * @dev Initializes the contract by setting a `name` and a `symbol` to the token collection.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
        return
            interfaceId == type(IERC721).interfaceId ||
            interfaceId == type(IERC721Metadata).interfaceId ||
            super.supportsInterface(interfaceId);
    }

    /**
     * @dev See {IERC721-balanceOf}.
     */
    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: address zero is not a valid owner");
        return _balances[owner];
    }

    /**
     * @dev See {IERC721-ownerOf}.
     */
    function ownerOf(uint256 tokenId) public view virtual override returns (address) {
        address owner = _ownerOf(tokenId);
        require(owner != address(0), "ERC721: invalid token ID");
        return owner;
    }

    /**
     * @dev See {IERC721Metadata-name}.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev See {IERC721Metadata-symbol}.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        _requireMinted(tokenId);

        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 overridden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public virtual override {
        address owner = ERC721.ownerOf(tokenId);
        require(to != owner, "ERC721: approval to current owner");

        require(
            _msgSender() == owner || isApprovedForAll(owner, _msgSender()),
            "ERC721: approve caller is not token owner or approved for all"
        );

        _approve(to, tokenId);
    }

    /**
     * @dev See {IERC721-getApproved}.
     */
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        _requireMinted(tokenId);

        return _tokenApprovals[tokenId];
    }

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

    /**
     * @dev See {IERC721-isApprovedForAll}.
     */
    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: caller is not token owner or 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: caller is not token owner or 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 the owner of the `tokenId`. Does NOT revert if token doesn't exist
     */
    function _ownerOf(uint256 tokenId) internal view virtual returns (address) {
        return _owners[tokenId];
    }

    /**
     * @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 _ownerOf(tokenId) != address(0);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        address owner = ERC721.ownerOf(tokenId);
        return (spender == owner || isApprovedForAll(owner, spender) || getApproved(tokenId) == spender);
    }

    /**
     * @dev Safely mints `tokenId` and transfers it to `to`.
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

    /**
     * @dev Same as {xref-ERC721-_safeMint-address-uint256-}[`_safeMint`], with an additional `data` parameter which is
     * forwarded in {IERC721Receiver-onERC721Received} to contract recipients.
     */
    function _safeMint(
        address to,
        uint256 tokenId,
        bytes memory data
    ) internal virtual {
        _mint(to, tokenId);
        require(
            _checkOnERC721Received(address(0), to, tokenId, data),
            "ERC721: transfer to non ERC721Receiver implementer"
        );
    }

    /**
     * @dev Mints `tokenId` and transfers it to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {_safeMint} whenever possible
     *
     * Requirements:
     *
     * - `tokenId` must not exist.
     * - `to` cannot be the zero address.
     *
     * Emits a {Transfer} event.
     */
    function _mint(address to, uint256 tokenId) internal virtual {
        require(to != address(0), "ERC721: mint to the zero address");
        require(!_exists(tokenId), "ERC721: token already minted");

        _beforeTokenTransfer(address(0), to, tokenId, 1);

        // Check that tokenId was not minted by `_beforeTokenTransfer` hook
        require(!_exists(tokenId), "ERC721: token already minted");

        unchecked {
            // Will not overflow unless all 2**256 token ids are minted to the same owner.
            // Given that tokens are minted one by one, it is impossible in practice that
            // this ever happens. Might change if we allow batch minting.
            // The ERC fails to describe this case.
            _balances[to] += 1;
        }

        _owners[tokenId] = to;

        emit Transfer(address(0), to, tokenId);

        _afterTokenTransfer(address(0), to, tokenId, 1);
    }

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     * This is an internal function that does not check if the sender is authorized to operate on the token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId);

        _beforeTokenTransfer(owner, address(0), tokenId, 1);

        // Update ownership in case tokenId was transferred by `_beforeTokenTransfer` hook
        owner = ERC721.ownerOf(tokenId);

        // Clear approvals
        delete _tokenApprovals[tokenId];

        unchecked {
            // Cannot overflow, as that would require more tokens to be burned/transferred
            // out than the owner initially received through minting and transferring in.
            _balances[owner] -= 1;
        }
        delete _owners[tokenId];

        emit Transfer(owner, address(0), tokenId);

        _afterTokenTransfer(owner, address(0), tokenId, 1);
    }

    /**
     * @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 from incorrect owner");
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId, 1);

        // Check that tokenId was not transferred by `_beforeTokenTransfer` hook
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer from incorrect owner");

        // Clear approvals from the previous owner
        delete _tokenApprovals[tokenId];

        unchecked {
            // `_balances[from]` cannot overflow for the same reason as described in `_burn`:
            // `from`'s balance is the number of token held, which is at least one before the current
            // transfer.
            // `_balances[to]` could overflow in the conditions described in `_mint`. That would require
            // all 2**256 token ids to be minted, which in practice is impossible.
            _balances[from] -= 1;
            _balances[to] += 1;
        }
        _owners[tokenId] = to;

        emit Transfer(from, to, tokenId);

        _afterTokenTransfer(from, to, tokenId, 1);
    }

    /**
     * @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);
    }

    /**
     * @dev Approve `operator` to operate on all of `owner` tokens
     *
     * Emits an {ApprovalForAll} event.
     */
    function _setApprovalForAll(
        address owner,
        address operator,
        bool approved
    ) internal virtual {
        require(owner != operator, "ERC721: approve to caller");
        _operatorApprovals[owner][operator] = approved;
        emit ApprovalForAll(owner, operator, approved);
    }

    /**
     * @dev Reverts if the `tokenId` has not been minted yet.
     */
    function _requireMinted(uint256 tokenId) internal view virtual {
        require(_exists(tokenId), "ERC721: invalid token ID");
    }

    /**
     * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
     * The call is not executed if the target address is not a contract.
     *
     * @param from address representing the previous owner of the given token ID
     * @param to target address that will receive the tokens
     * @param tokenId uint256 ID of the token to be transferred
     * @param data bytes optional data to send along with the call
     * @return bool whether the call correctly returned the expected magic value
     */
    function _checkOnERC721Received(
        address from,
        address to,
        uint256 tokenId,
        bytes memory data
    ) private returns (bool) {
        if (to.isContract()) {
            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, data) returns (bytes4 retval) {
                return retval == IERC721Receiver.onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert("ERC721: transfer to non ERC721Receiver implementer");
                } else {
                    /// @solidity memory-safe-assembly
                    assembly {
                        revert(add(32, reason), mload(reason))
                    }
                }
            }
        } else {
            return true;
        }
    }

    /**
     * @dev Hook that is called before any token transfer. This includes minting and burning. If {ERC721Consecutive} is
     * used, the hook may be called as part of a consecutive (batch) mint, as indicated by `batchSize` greater than 1.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s tokens will be transferred to `to`.
     * - When `from` is zero, the tokens will be minted for `to`.
     * - When `to` is zero, ``from``'s tokens will be burned.
     * - `from` and `to` are never both zero.
     * - `batchSize` is non-zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 firstTokenId,
        uint256 batchSize
    ) internal virtual {}

    /**
     * @dev Hook that is called after any token transfer. This includes minting and burning. If {ERC721Consecutive} is
     * used, the hook may be called as part of a consecutive (batch) mint, as indicated by `batchSize` greater than 1.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s tokens were transferred to `to`.
     * - When `from` is zero, the tokens were minted for `to`.
     * - When `to` is zero, ``from``'s tokens were burned.
     * - `from` and `to` are never both zero.
     * - `batchSize` is non-zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 firstTokenId,
        uint256 batchSize
    ) internal virtual {}

    /**
     * @dev Unsafe write access to the balances, used by extensions that "mint" tokens using an {ownerOf} override.
     *
     * WARNING: Anyone calling this MUST ensure that the balances remain consistent with the ownership. The invariant
     * being that for any address `a` the value returned by `balanceOf(a)` must be equal to the number of tokens such
     * that `ownerOf(tokenId)` is `a`.
     */
    // solhint-disable-next-line func-name-mixedcase
    function __unsafe_increaseBalance(address account, uint256 amount) internal {
        _balances[account] += amount;
    }
}

// File: @openzeppelin/contracts/token/ERC721/extensions/ERC721Burnable.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC721/extensions/ERC721Burnable.sol)

pragma solidity ^0.8.0;

import "../ERC721.sol";
import "../../../utils/Context.sol";

/**
 * @title ERC721 Burnable Token
 * @dev ERC721 Token that can be burned (destroyed).
 */
abstract contract ERC721Burnable is Context, ERC721 {
    /**
     * @dev Burns `tokenId`. See {ERC721-_burn}.
     *
     * Requirements:
     *
     * - The caller must own `tokenId` or be an approved operator.
     */
    function burn(uint256 tokenId) public virtual {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: caller is not token owner or approved");
        _burn(tokenId);
    }
}

// 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/token/ERC721/IERC721.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (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`.
     *
     * 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;

    /**
     * @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 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: Note that the caller is responsible to confirm that the recipient is capable of receiving ERC721
     * or else they may be permanently lost. Usage of {safeTransferFrom} prevents loss, though the caller must
     * understand this adds an external call which potentially creates a reentrancy vulnerability.
     *
     * 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 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 the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @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);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (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 `IERC721Receiver.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (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 functionCallWithValue(target, data, 0, "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");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or 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 {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // 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
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

// File: @openzeppelin/contracts/utils/Base64.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (utils/Base64.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides a set of functions to operate with Base64 strings.
 *
 * _Available since v4.5._
 */
library Base64 {
    /**
     * @dev Base64 Encoding/Decoding Table
     */
    string internal constant _TABLE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    /**
     * @dev Converts a `bytes` to its Bytes64 `string` representation.
     */
    function encode(bytes memory data) internal pure returns (string memory) {
        /**
         * Inspired by Brecht Devos (Brechtpd) implementation - MIT licence
         * https://github.com/Brechtpd/base64/blob/e78d9fd951e7b0977ddca77d92dc85183770daf4/base64.sol
         */
        if (data.length == 0) return "";

        // Loads the table into memory
        string memory table = _TABLE;

        // Encoding takes 3 bytes chunks of binary data from `bytes` data parameter
        // and split into 4 numbers of 6 bits.
        // The final Base64 length should be `bytes` data length multiplied by 4/3 rounded up
        // - `data.length + 2`  -> Round up
        // - `/ 3`              -> Number of 3-bytes chunks
        // - `4 *`              -> 4 characters for each chunk
        string memory result = new string(4 * ((data.length + 2) / 3));

        /// @solidity memory-safe-assembly
        assembly {
            // Prepare the lookup table (skip the first "length" byte)
            let tablePtr := add(table, 1)

            // Prepare result pointer, jump over length
            let resultPtr := add(result, 32)

            // Run over the input, 3 bytes at a time
            for {
                let dataPtr := data
                let endPtr := add(data, mload(data))
            } lt(dataPtr, endPtr) {

            } {
                // Advance 3 bytes
                dataPtr := add(dataPtr, 3)
                let input := mload(dataPtr)

                // To write each character, shift the 3 bytes (18 bits) chunk
                // 4 times in blocks of 6 bits for each character (18, 12, 6, 0)
                // and apply logical AND with 0x3F which is the number of
                // the previous character in the ASCII table prior to the Base64 Table
                // The result is then added to the table to get the character to write,
                // and finally write it in the result pointer but with a left shift
                // of 256 (1 byte) - 8 (1 ASCII char) = 248 bits

                mstore8(resultPtr, mload(add(tablePtr, and(shr(18, input), 0x3F))))
                resultPtr := add(resultPtr, 1) // Advance

                mstore8(resultPtr, mload(add(tablePtr, and(shr(12, input), 0x3F))))
                resultPtr := add(resultPtr, 1) // Advance

                mstore8(resultPtr, mload(add(tablePtr, and(shr(6, input), 0x3F))))
                resultPtr := add(resultPtr, 1) // Advance

                mstore8(resultPtr, mload(add(tablePtr, and(input, 0x3F))))
                resultPtr := add(resultPtr, 1) // Advance
            }

            // When data `bytes` is not exactly 3 bytes long
            // it is padded with `=` characters at the end
            switch mod(mload(data), 3)
            case 1 {
                mstore8(sub(resultPtr, 1), 0x3d)
                mstore8(sub(resultPtr, 2), 0x3d)
            }
            case 2 {
                mstore8(sub(resultPtr, 1), 0x3d)
            }
        }

        return result;
    }
}

// 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/utils/Counters.sol



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

pragma solidity ^0.8.0;

/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented, decremented or reset. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 */
library Counters {
    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        unchecked {
            counter._value += 1;
        }
    }

    function decrement(Counter storage counter) internal {
        uint256 value = counter._value;
        require(value > 0, "Counter: decrement overflow");
        unchecked {
            counter._value = value - 1;
        }
    }

    function reset(Counter storage counter) internal {
        counter._value = 0;
    }
}

// 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);
}

// File: @openzeppelin/contracts/utils/math/Math.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/math/Math.sol)

pragma solidity ^0.8.0;

/**
 * @dev Standard math utilities missing in the Solidity language.
 */
library Math {
    enum Rounding {
        Down, // Toward negative infinity
        Up, // Toward infinity
        Zero // Toward zero
    }

    /**
     * @dev Returns the largest of two numbers.
     */
    function max(uint256 a, uint256 b) internal pure returns (uint256) {
        return a > b ? a : b;
    }

    /**
     * @dev Returns the smallest of two numbers.
     */
    function min(uint256 a, uint256 b) internal pure returns (uint256) {
        return a < b ? a : b;
    }

    /**
     * @dev Returns the average of two numbers. The result is rounded towards
     * zero.
     */
    function average(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b) / 2 can overflow.
        return (a & b) + (a ^ b) / 2;
    }

    /**
     * @dev Returns the ceiling of the division of two numbers.
     *
     * This differs from standard division with `/` in that it rounds up instead
     * of rounding down.
     */
    function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
        // (a + b - 1) / b can overflow on addition, so we distribute.
        return a == 0 ? 0 : (a - 1) / b + 1;
    }

    /**
     * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0
     * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv)
     * with further edits by Uniswap Labs also under MIT license.
     */
    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 denominator
    ) internal pure returns (uint256 result) {
        unchecked {
            // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
            // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
            // variables such that product = prod1 * 2^256 + prod0.
            uint256 prod0; // Least significant 256 bits of the product
            uint256 prod1; // Most significant 256 bits of the product
            assembly {
                let mm := mulmod(x, y, not(0))
                prod0 := mul(x, y)
                prod1 := sub(sub(mm, prod0), lt(mm, prod0))
            }

            // Handle non-overflow cases, 256 by 256 division.
            if (prod1 == 0) {
                return prod0 / denominator;
            }

            // Make sure the result is less than 2^256. Also prevents denominator == 0.
            require(denominator > prod1);

            ///////////////////////////////////////////////
            // 512 by 256 division.
            ///////////////////////////////////////////////

            // Make division exact by subtracting the remainder from [prod1 prod0].
            uint256 remainder;
            assembly {
                // Compute remainder using mulmod.
                remainder := mulmod(x, y, denominator)

                // Subtract 256 bit number from 512 bit number.
                prod1 := sub(prod1, gt(remainder, prod0))
                prod0 := sub(prod0, remainder)
            }

            // Factor powers of two out of denominator and compute largest power of two divisor of denominator. Always >= 1.
            // See https://cs.stackexchange.com/q/138556/92363.

            // Does not overflow because the denominator cannot be zero at this stage in the function.
            uint256 twos = denominator & (~denominator + 1);
            assembly {
                // Divide denominator by twos.
                denominator := div(denominator, twos)

                // Divide [prod1 prod0] by twos.
                prod0 := div(prod0, twos)

                // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
                twos := add(div(sub(0, twos), twos), 1)
            }

            // Shift in bits from prod1 into prod0.
            prod0 |= prod1 * twos;

            // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
            // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
            // four bits. That is, denominator * inv = 1 mod 2^4.
            uint256 inverse = (3 * denominator) ^ 2;

            // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also works
            // in modular arithmetic, doubling the correct bits in each step.
            inverse *= 2 - denominator * inverse; // inverse mod 2^8
            inverse *= 2 - denominator * inverse; // inverse mod 2^16
            inverse *= 2 - denominator * inverse; // inverse mod 2^32
            inverse *= 2 - denominator * inverse; // inverse mod 2^64
            inverse *= 2 - denominator * inverse; // inverse mod 2^128
            inverse *= 2 - denominator * inverse; // inverse mod 2^256

            // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
            // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
            // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
            // is no longer required.
            result = prod0 * inverse;
            return result;
        }
    }

    /**
     * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
     */
    function mulDiv(
        uint256 x,
        uint256 y,
        uint256 denominator,
        Rounding rounding
    ) internal pure returns (uint256) {
        uint256 result = mulDiv(x, y, denominator);
        if (rounding == Rounding.Up && mulmod(x, y, denominator) > 0) {
            result += 1;
        }
        return result;
    }

    /**
     * @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded down.
     *
     * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
     */
    function sqrt(uint256 a) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }

        // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
        //
        // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
        // `msb(a) <= a < 2*msb(a)`. This value can be written `msb(a)=2**k` with `k=log2(a)`.
        //
        // This can be rewritten `2**log2(a) <= a < 2**(log2(a) + 1)`
        // → `sqrt(2**k) <= sqrt(a) < sqrt(2**(k+1))`
        // → `2**(k/2) <= sqrt(a) < 2**((k+1)/2) <= 2**(k/2 + 1)`
        //
        // Consequently, `2**(log2(a) / 2)` is a good first approximation of `sqrt(a)` with at least 1 correct bit.
        uint256 result = 1 << (log2(a) >> 1);

        // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
        // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
        // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
        // into the expected uint128 result.
        unchecked {
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            result = (result + a / result) >> 1;
            return min(result, a / result);
        }
    }

    /**
     * @notice Calculates sqrt(a), following the selected rounding direction.
     */
    function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = sqrt(a);
            return result + (rounding == Rounding.Up && result * result < a ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 2, rounded down, of a positive value.
     * Returns 0 if given 0.
     */
    function log2(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >> 128 > 0) {
                value >>= 128;
                result += 128;
            }
            if (value >> 64 > 0) {
                value >>= 64;
                result += 64;
            }
            if (value >> 32 > 0) {
                value >>= 32;
                result += 32;
            }
            if (value >> 16 > 0) {
                value >>= 16;
                result += 16;
            }
            if (value >> 8 > 0) {
                value >>= 8;
                result += 8;
            }
            if (value >> 4 > 0) {
                value >>= 4;
                result += 4;
            }
            if (value >> 2 > 0) {
                value >>= 2;
                result += 2;
            }
            if (value >> 1 > 0) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 2, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log2(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log2(value);
            return result + (rounding == Rounding.Up && 1 << result < value ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 10, rounded down, of a positive value.
     * Returns 0 if given 0.
     */
    function log10(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >= 10**64) {
                value /= 10**64;
                result += 64;
            }
            if (value >= 10**32) {
                value /= 10**32;
                result += 32;
            }
            if (value >= 10**16) {
                value /= 10**16;
                result += 16;
            }
            if (value >= 10**8) {
                value /= 10**8;
                result += 8;
            }
            if (value >= 10**4) {
                value /= 10**4;
                result += 4;
            }
            if (value >= 10**2) {
                value /= 10**2;
                result += 2;
            }
            if (value >= 10**1) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log10(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log10(value);
            return result + (rounding == Rounding.Up && 10**result < value ? 1 : 0);
        }
    }

    /**
     * @dev Return the log in base 256, rounded down, of a positive value.
     * Returns 0 if given 0.
     *
     * Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
     */
    function log256(uint256 value) internal pure returns (uint256) {
        uint256 result = 0;
        unchecked {
            if (value >> 128 > 0) {
                value >>= 128;
                result += 16;
            }
            if (value >> 64 > 0) {
                value >>= 64;
                result += 8;
            }
            if (value >> 32 > 0) {
                value >>= 32;
                result += 4;
            }
            if (value >> 16 > 0) {
                value >>= 16;
                result += 2;
            }
            if (value >> 8 > 0) {
                result += 1;
            }
        }
        return result;
    }

    /**
     * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
     * Returns 0 if given 0.
     */
    function log256(uint256 value, Rounding rounding) internal pure returns (uint256) {
        unchecked {
            uint256 result = log256(value);
            return result + (rounding == Rounding.Up && 1 << (result * 8) < value ? 1 : 0);
        }
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/Strings.sol)

pragma solidity ^0.8.0;

import "./math/Math.sol";

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _SYMBOLS = "0123456789abcdef";
    uint8 private constant _ADDRESS_LENGTH = 20;

    /**
     * @dev Converts a `uint256` to its ASCII `string` decimal representation.
     */
    function toString(uint256 value) internal pure returns (string memory) {
        unchecked {
            uint256 length = Math.log10(value) + 1;
            string memory buffer = new string(length);
            uint256 ptr;
            /// @solidity memory-safe-assembly
            assembly {
                ptr := add(buffer, add(32, length))
            }
            while (true) {
                ptr--;
                /// @solidity memory-safe-assembly
                assembly {
                    mstore8(ptr, byte(mod(value, 10), _SYMBOLS))
                }
                value /= 10;
                if (value == 0) break;
            }
            return buffer;
        }
    }

    /**
     * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
     */
    function toHexString(uint256 value) internal pure returns (string memory) {
        unchecked {
            return toHexString(value, Math.log256(value) + 1);
        }
    }

    /**
     * @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] = _SYMBOLS[value & 0xf];
            value >>= 4;
        }
        require(value == 0, "Strings: hex length insufficient");
        return string(buffer);
    }

    /**
     * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal representation.
     */
    function toHexString(address addr) internal pure returns (string memory) {
        return toHexString(uint256(uint160(addr)), _ADDRESS_LENGTH);
    }
}

// File: contracts/CodexLight.sol



// SPDX-License-Identifier: MIT
pragma solidity ^0.8.18;

///  ##     ###### ######        ###### ##  ## ###### #####  ######        #####  ######        ##     ######  ####  ##  ## ######
///  ##     ##       ##            ##   ##  ## ##     ##  ## ##            ##  ## ##            ##       ##   ##     ##  ##   ##
///  ##     ####     ##            ##   ###### ####   #####  ####          #####  ####          ##       ##   ## ### ######   ##
///  ##     ##       ##            ##   ##  ## ##     ##  ## ##            ##  ## ##            ##       ##   ##  ## ##  ##   ##
///  ###### ######   ##            ##   ##  ## ###### ##  ## ######        #####  ######        ###### ######  ####  ##  ##   ##

import { Base64 } from "@openzeppelin/contracts/utils/Base64.sol";
import { ERC721, IERC721, IERC165 } from "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import { ERC721Burnable } from "@openzeppelin/contracts/token/ERC721/extensions/ERC721Burnable.sol";
import { Ownable } from "@openzeppelin/contracts/access/Ownable.sol";
import { Strings } from "@openzeppelin/contracts/utils/Strings.sol";
import { IERC721Receiver } from "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
import { Counters } from "@openzeppelin/contracts/utils/Counters.sol";

import { strings } from "./strings.sol";
import { IERC4906 } from "./IERC4906.sol";

/// @title CodexLight
/// @author akuti.eth
/// @notice Lights by Codex Library (https://codexlibrary.org). CodexLight is minted by burning a matchbook.
contract CodexLight is IERC4906, ERC721, ERC721Burnable, IERC721Receiver, Ownable {
    using Counters for Counters.Counter;
    using Strings for uint256;
    using strings for *;

    struct AttributeCategory {
        // trait names within category
        string[] names;
        // commulative thresholds per trait within this category
        uint16[] thresholds;
    }

    struct UserData {
        uint8 reservedTokenId;
        bool hasMinted;
    }

    // constants
    address public constant MATCHBOOKS = 0xd1466d7A2e13A47677608F68093c5eA9fE910611;
    uint256 internal constant MAX_SUPPLY = 3001;
    uint256 internal constant NR_ATTRIBUTES = 6;
    uint256 internal constant NR_RESERVED = 10;

    // token and minting related data
    Counters.Counter internal _tokenIdCounter;
    Counters.Counter internal _reservedTokenIdCounter;
    Counters.Counter internal _burnCounter;
    mapping(address user => UserData data) internal _userData;

    // metadata
    string internal _imageBaseURI;
    string internal _externalBaseURI = "https://codexlibrary.org/light/";
    string internal _description = "May light show us the way.";
    string[NR_ATTRIBUTES] internal _attributeNames;
    uint64[MAX_SUPPLY] internal _seeds;
    mapping(string name => AttributeCategory traits) internal _attributes;

    // errors
    error InvalidToken();
    error AlreadyMinted();
    error OutOfStock();

    constructor(
        string[] memory categoryNames,
        AttributeCategory[] memory categories,
        address[] memory reserved_
    ) ERC721("CodexLight", "LIGHT") {
        require(categoryNames.length == categories.length);
        require(reserved_.length == NR_RESERVED);
        _setAttributes(categoryNames, categories);
        _setReserved(reserved_);
    }

    // external admin functions

    /**
     * @dev Sets the external token URI description to `externalBaseURI_`. The URI should end in a `/`.
     *
     * Emits a {BatchMetadataUpdate} event.
     */
    function setBaseURI(string calldata baseURI_) external onlyOwner {
        _imageBaseURI = baseURI_;
        emit BatchMetadataUpdate(1, MAX_SUPPLY);
    }

    /**
     * @dev Sets the external token URI description to `externalBaseURI_`.
     *
     * Emits a {BatchMetadataUpdate} event.
     */
    function setExternalBaseURI(string calldata externalBaseURI_) external onlyOwner {
        _externalBaseURI = externalBaseURI_;
        emit BatchMetadataUpdate(1, MAX_SUPPLY);
    }

    /**
     * @dev Sets the token description to `description_`.
     *
     * Emits a {BatchMetadataUpdate} event.
     */
    function setDescription(string calldata description_) external onlyOwner {
        _description = description_;
        emit BatchMetadataUpdate(1, MAX_SUPPLY);
    }

    // external/public functions

    /**
     * @dev See {ERC721Burnable-burn}.
     */
    function burn(uint256 tokenId) public override {
        super.burn(tokenId);
        _burnCounter.increment();
    }

    // external/public functions

    /**
     * @notice Mint a Candle when receiving a Matchbook. Limited to one per address.
     * @dev Hook for `saveTransferFrom` of ERC721 tokens to this contract
     * @param from The address which previously owned the token
     * @param tokenId The ID of the token being transferred
     */
    function onERC721Received(
        address,
        address from,
        uint256 tokenId,
        bytes calldata
    ) external override returns (bytes4) {
        if (msg.sender != MATCHBOOKS) revert InvalidToken();
        UserData memory user = _userData[from];
        if (user.hasMinted) revert AlreadyMinted();

        uint256 newTokenId;
        if (user.reservedTokenId > 0) {
            _reservedTokenIdCounter.increment();
            newTokenId = user.reservedTokenId;
        } else if (_tokenIdCounter.current() + NR_RESERVED == MAX_SUPPLY) {
            revert OutOfStock();
        } else {
            _tokenIdCounter.increment();
            newTokenId = _tokenIdCounter.current() + NR_RESERVED;
        }

        // light up
        user.hasMinted = true;
        _userData[from] = user;
        ERC721Burnable(MATCHBOOKS).burn(tokenId);

        // get pseudo-random seed
        // -1 since tokens are 1 based
        _seeds[newTokenId - 1] = uint64(
            uint256(keccak256(abi.encodePacked(newTokenId, block.coinbase, block.prevrandao, block.basefee)))
        );
        _mint(from, newTokenId);

        return IERC721Receiver.onERC721Received.selector;
    }

    // external/public view functions

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        _requireMinted(tokenId);

        string memory tokenIdStr = tokenId.toString();
        string memory tokenURI_ = string.concat(
            '{"name":"Light #',
            tokenIdStr,
            '","description":"',
            _description,
            '","image":"',
            _imageBaseURI,
            uint256(_seeds[tokenId - 1]).toString(),
            '.png","external_url":"',
            _externalBaseURI,
            tokenIdStr,
            '","attributes":',
            _attributeJson(tokenId),
            "}"
        );
        return string.concat("data:application/json;base64,", Base64.encode(bytes(tokenURI_)));
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override(ERC721, IERC165) returns (bool) {
        // adds interface for IERC4906
        return interfaceId == bytes4(0x49064906) || super.supportsInterface(interfaceId);
    }

    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256) {
        return _tokenIdCounter.current() + _reservedTokenIdCounter.current() - _burnCounter.current();
    }

    // internal functions

    function _setAttributes(string[] memory categoryNames, AttributeCategory[] memory categories) internal {
        uint256 length = categoryNames.length;
        for (uint256 i = 0; i < length; ) {
            _attributeNames[i] = categoryNames[i];
            _attributes[categoryNames[i]] = categories[i];
            unchecked {
                i++;
            }
        }
    }

    function _setReserved(address[] memory reserved_) internal {
        uint256 length = reserved_.length;
        for (uint256 i = 0; i < length; ) {
            _userData[reserved_[i]].reservedTokenId = uint8(i + 1);
            unchecked {
                i++;
            }
        }
    }

    // internal view functions

    function _getLight(uint256 tokenId) internal view returns (string[NR_ATTRIBUTES] memory attributes) {
        uint256 seed = _seeds[tokenId - 1]; // -1 since tokens are 1 based
        for (uint256 i = 0; i < NR_ATTRIBUTES; i++) {
            uint256 current = seed % 256;
            AttributeCategory memory category = _attributes[_attributeNames[i]];
            for (uint256 j = 0; j < category.names.length; j++) {
                if (current > category.thresholds[j]) {
                    continue;
                }
                attributes[i] = category.names[j];
                break;
            }
            seed >>= 8;
        }
    }

    function _attributeJson(uint256 tokenId) internal view returns (string memory out) {
        string[NR_ATTRIBUTES] memory attributes = _getLight(tokenId);
        out = "[";
        strings.slice memory delim = "_".toSlice();
        for (uint256 traitIdx = 0; traitIdx < NR_ATTRIBUTES; traitIdx++) {
            strings.slice memory name_ = attributes[traitIdx].toSlice();
            strings.slice[] memory parts = new strings.slice[](name_.count(delim) + 1);
            for (uint i = 0; i < parts.length; i++) {
                parts[i] = name_.split(delim);
            }
            out = string.concat(
                out,
                '{"trait_type":"',
                _attributeNames[traitIdx],
                '","value":"',
                " ".toSlice().join(parts),
                '"}'
            );
            if (traitIdx < NR_ATTRIBUTES - 1) out = string.concat(out, ",");
        }
        out = string.concat(out, "]");
    }
}

// File: contracts/IERC4906.sol



// SPDX-License-Identifier: CC0-1.0
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
import "@openzeppelin/contracts/utils/introspection/IERC165.sol";

/// @title EIP-721 Metadata Update Extension
interface IERC4906 is IERC165, IERC721 {
    /// @dev This event emits when the metadata of a token is changed.
    /// So that the third-party platforms such as NFT market could
    /// timely update the images and related attributes of the NFT.
    event MetadataUpdate(uint256 _tokenId);

    /// @dev This event emits when the metadata of a range of tokens is changed.
    /// So that the third-party platforms such as NFT market could
    /// timely update the images and related attributes of the NFTs.
    event BatchMetadataUpdate(uint256 _fromTokenId, uint256 _toTokenId);
}

// File: contracts/strings.sol



// SPDX-License-Identifier:	Apache-2.0
/*
 * @title String & slice utility library for Solidity contracts.
 * @author Nick Johnson <arachnid@notdot.net>
 *
 * @dev Functionality in this library is largely implemented using an
 *      abstraction called a 'slice'. A slice represents a part of a string -
 *      anything from the entire string to a single character, or even no
 *      characters at all (a 0-length slice). Since a slice only has to specify
 *      an offset and a length, copying and manipulating slices is a lot less
 *      expensive than copying and manipulating the strings they reference.
 *
 *      To further reduce gas costs, most functions on slice that need to return
 *      a slice modify the original one instead of allocating a new one; for
 *      instance, `s.split(".")` will return the text up to the first '.',
 *      modifying s to only contain the remainder of the string after the '.'.
 *      In situations where you do not want to modify the original slice, you
 *      can make a copy first with `.copy()`, for example:
 *      `s.copy().split(".")`. Try and avoid using this idiom in loops; since
 *      Solidity has no memory management, it will result in allocating many
 *      short-lived slices that are later discarded.
 *
 *      Functions that return two slices come in two versions: a non-allocating
 *      version that takes the second slice as an argument, modifying it in
 *      place, and an allocating version that allocates and returns the second
 *      slice; see `nextRune` for example.
 *
 *      Functions that have to copy string data will return strings rather than
 *      slices; these can be cast back to slices for further processing if
 *      required.
 *
 *      For convenience, some functions are provided with non-modifying
 *      variants that create a new slice and return both; for instance,
 *      `s.splitNew('.')` leaves s unmodified, and returns two values
 *      corresponding to the left and right parts of the string.
 *
 *      Changes:
 *      - Add SPDX-License-Identifier
 *      - Rename len in memcpy to _len to fix shadowed declaration warning
 */

pragma solidity ^0.8.0;

library strings {
    struct slice {
        uint256 _len;
        uint256 _ptr;
    }

    function memcpy(uint256 dest, uint256 src, uint256 _len) private pure {
        // Copy word-length chunks while possible
        for (; _len >= 32; _len -= 32) {
            assembly {
                mstore(dest, mload(src))
            }
            dest += 32;
            src += 32;
        }

        // Copy remaining bytes
        uint256 mask = type(uint256).max;
        if (_len > 0) {
            mask = 256 ** (32 - _len) - 1;
        }
        assembly {
            let srcpart := and(mload(src), not(mask))
            let destpart := and(mload(dest), mask)
            mstore(dest, or(destpart, srcpart))
        }
    }

    /*
     * @dev Returns a slice containing the entire string.
     * @param self The string to make a slice from.
     * @return A newly allocated slice containing the entire string.
     */
    function toSlice(string memory self) internal pure returns (slice memory) {
        uint256 ptr;
        assembly {
            ptr := add(self, 0x20)
        }
        return slice(bytes(self).length, ptr);
    }

    /*
     * @dev Returns the length of a null-terminated bytes32 string.
     * @param self The value to find the length of.
     * @return The length of the string, from 0 to 32.
     */
    function len(bytes32 self) internal pure returns (uint256) {
        uint256 ret;
        if (self == 0) return 0;
        if (uint256(self) & type(uint128).max == 0) {
            ret += 16;
            self = bytes32(uint256(self) / 0x100000000000000000000000000000000);
        }
        if (uint256(self) & type(uint64).max == 0) {
            ret += 8;
            self = bytes32(uint256(self) / 0x10000000000000000);
        }
        if (uint256(self) & type(uint32).max == 0) {
            ret += 4;
            self = bytes32(uint256(self) / 0x100000000);
        }
        if (uint256(self) & type(uint16).max == 0) {
            ret += 2;
            self = bytes32(uint256(self) / 0x10000);
        }
        if (uint256(self) & type(uint8).max == 0) {
            ret += 1;
        }
        return 32 - ret;
    }

    /*
     * @dev Returns a slice containing the entire bytes32, interpreted as a
     *      null-terminated utf-8 string.
     * @param self The bytes32 value to convert to a slice.
     * @return A new slice containing the value of the input argument up to the
     *         first null.
     */
    function toSliceB32(bytes32 self) internal pure returns (slice memory ret) {
        // Allocate space for `self` in memory, copy it there, and point ret at it
        assembly {
            let ptr := mload(0x40)
            mstore(0x40, add(ptr, 0x20))
            mstore(ptr, self)
            mstore(add(ret, 0x20), ptr)
        }
        ret._len = len(self);
    }

    /*
     * @dev Returns a new slice containing the same data as the current slice.
     * @param self The slice to copy.
     * @return A new slice containing the same data as `self`.
     */
    function copy(slice memory self) internal pure returns (slice memory) {
        return slice(self._len, self._ptr);
    }

    /*
     * @dev Copies a slice to a new string.
     * @param self The slice to copy.
     * @return A newly allocated string containing the slice's text.
     */
    function toString(slice memory self) internal pure returns (string memory) {
        string memory ret = new string(self._len);
        uint256 retptr;
        assembly {
            retptr := add(ret, 32)
        }

        memcpy(retptr, self._ptr, self._len);
        return ret;
    }

    /*
     * @dev Returns the length in runes of the slice. Note that this operation
     *      takes time proportional to the length of the slice; avoid using it
     *      in loops, and call `slice.empty()` if you only need to know whether
     *      the slice is empty or not.
     * @param self The slice to operate on.
     * @return The length of the slice in runes.
     */
    function len(slice memory self) internal pure returns (uint256 l) {
        // Starting at ptr-31 means the LSB will be the byte we care about
        uint256 ptr = self._ptr - 31;
        uint256 end = ptr + self._len;
        for (l = 0; ptr < end; l++) {
            uint8 b;
            assembly {
                b := and(mload(ptr), 0xFF)
            }
            if (b < 0x80) {
                ptr += 1;
            } else if (b < 0xE0) {
                ptr += 2;
            } else if (b < 0xF0) {
                ptr += 3;
            } else if (b < 0xF8) {
                ptr += 4;
            } else if (b < 0xFC) {
                ptr += 5;
            } else {
                ptr += 6;
            }
        }
    }

    /*
     * @dev Returns true if the slice is empty (has a length of 0).
     * @param self The slice to operate on.
     * @return True if the slice is empty, False otherwise.
     */
    function empty(slice memory self) internal pure returns (bool) {
        return self._len == 0;
    }

    /*
     * @dev Returns a positive number if `other` comes lexicographically after
     *      `self`, a negative number if it comes before, or zero if the
     *      contents of the two slices are equal. Comparison is done per-rune,
     *      on unicode codepoints.
     * @param self The first slice to compare.
     * @param other The second slice to compare.
     * @return The result of the comparison.
     */
    function compare(slice memory self, slice memory other) internal pure returns (int256) {
        uint256 shortest = self._len;
        if (other._len < self._len) shortest = other._len;

        uint256 selfptr = self._ptr;
        uint256 otherptr = other._ptr;
        for (uint256 idx = 0; idx < shortest; idx += 32) {
            uint256 a;
            uint256 b;
            assembly {
                a := mload(selfptr)
                b := mload(otherptr)
            }
            if (a != b) {
                // Mask out irrelevant bytes and check again
                uint256 mask = type(uint256).max; // 0xffff...
                if (shortest < 32) {
                    mask = ~(2 ** (8 * (32 - shortest + idx)) - 1);
                }
                unchecked {
                    uint256 diff = (a & mask) - (b & mask);
                    if (diff != 0) return int256(diff);
                }
            }
            selfptr += 32;
            otherptr += 32;
        }
        return int256(self._len) - int256(other._len);
    }

    /*
     * @dev Returns true if the two slices contain the same text.
     * @param self The first slice to compare.
     * @param self The second slice to compare.
     * @return True if the slices are equal, false otherwise.
     */
    function equals(slice memory self, slice memory other) internal pure returns (bool) {
        return compare(self, other) == 0;
    }

    /*
     * @dev Extracts the first rune in the slice into `rune`, advancing the
     *      slice to point to the next rune and returning `self`.
     * @param self The slice to operate on.
     * @param rune The slice that will contain the first rune.
     * @return `rune`.
     */
    function nextRune(slice memory self, slice memory rune) internal pure returns (slice memory) {
        rune._ptr = self._ptr;

        if (self._len == 0) {
            rune._len = 0;
            return rune;
        }

        uint256 l;
        uint256 b;
        // Load the first byte of the rune into the LSBs of b
        assembly {
            b := and(mload(sub(mload(add(self, 32)), 31)), 0xFF)
        }
        if (b < 0x80) {
            l = 1;
        } else if (b < 0xE0) {
            l = 2;
        } else if (b < 0xF0) {
            l = 3;
        } else {
            l = 4;
        }

        // Check for truncated codepoints
        if (l > self._len) {
            rune._len = self._len;
            self._ptr += self._len;
            self._len = 0;
            return rune;
        }

        self._ptr += l;
        self._len -= l;
        rune._len = l;
        return rune;
    }

    /*
     * @dev Returns the first rune in the slice, advancing the slice to point
     *      to the next rune.
     * @param self The slice to operate on.
     * @return A slice containing only the first rune from `self`.
     */
    function nextRune(slice memory self) internal pure returns (slice memory ret) {
        nextRune(self, ret);
    }

    /*
     * @dev Returns the number of the first codepoint in the slice.
     * @param self The slice to operate on.
     * @return The number of the first codepoint in the slice.
     */
    function ord(slice memory self) internal pure returns (uint256 ret) {
        if (self._len == 0) {
            return 0;
        }

        uint256 word;
        uint256 length;
        uint256 divisor = 2 ** 248;

        // Load the rune into the MSBs of b
        assembly {
            word := mload(mload(add(self, 32)))
        }
        uint256 b = word / divisor;
        if (b < 0x80) {
            ret = b;
            length = 1;
        } else if (b < 0xE0) {
            ret = b & 0x1F;
            length = 2;
        } else if (b < 0xF0) {
            ret = b & 0x0F;
            length = 3;
        } else {
            ret = b & 0x07;
            length = 4;
        }

        // Check for truncated codepoints
        if (length > self._len) {
            return 0;
        }

        for (uint256 i = 1; i < length; i++) {
            divisor = divisor / 256;
            b = (word / divisor) & 0xFF;
            if (b & 0xC0 != 0x80) {
                // Invalid UTF-8 sequence
                return 0;
            }
            ret = (ret * 64) | (b & 0x3F);
        }

        return ret;
    }

    /*
     * @dev Returns the keccak-256 hash of the slice.
     * @param self The slice to hash.
     * @return The hash of the slice.
     */
    function keccak(slice memory self) internal pure returns (bytes32 ret) {
        assembly {
            ret := keccak256(mload(add(self, 32)), mload(self))
        }
    }

    /*
     * @dev Returns true if `self` starts with `needle`.
     * @param self The slice to operate on.
     * @param needle The slice to search for.
     * @return True if the slice starts with the provided text, false otherwise.
     */
    function startsWith(slice memory self, slice memory needle) internal pure returns (bool) {
        if (self._len < needle._len) {
            return false;
        }

        if (self._ptr == needle._ptr) {
            return true;
        }

        bool equal;
        assembly {
            let length := mload(needle)
            let selfptr := mload(add(self, 0x20))
            let needleptr := mload(add(needle, 0x20))
            equal := eq(keccak256(selfptr, length), keccak256(needleptr, length))
        }
        return equal;
    }

    /*
     * @dev If `self` starts with `needle`, `needle` is removed from the
     *      beginning of `self`. Otherwise, `self` is unmodified.
     * @param self The slice to operate on.
     * @param needle The slice to search for.
     * @return `self`
     */
    function beyond(slice memory self, slice memory needle) internal pure returns (slice memory) {
        if (self._len < needle._len) {
            return self;
        }

        bool equal = true;
        if (self._ptr != needle._ptr) {
            assembly {
                let length := mload(needle)
                let selfptr := mload(add(self, 0x20))
                let needleptr := mload(add(needle, 0x20))
                equal := eq(keccak256(selfptr, length), keccak256(needleptr, length))
            }
        }

        if (equal) {
            self._len -= needle._len;
            self._ptr += needle._len;
        }

        return self;
    }

    /*
     * @dev Returns true if the slice ends with `needle`.
     * @param self The slice to operate on.
     * @param needle The slice to search for.
     * @return True if the slice starts with the provided text, false otherwise.
     */
    function endsWith(slice memory self, slice memory needle) internal pure returns (bool) {
        if (self._len < needle._len) {
            return false;
        }

        uint256 selfptr = self._ptr + self._len - needle._len;

        if (selfptr == needle._ptr) {
            return true;
        }

        bool equal;
        assembly {
            let length := mload(needle)
            let needleptr := mload(add(needle, 0x20))
            equal := eq(keccak256(selfptr, length), keccak256(needleptr, length))
        }

        return equal;
    }

    /*
     * @dev If `self` ends with `needle`, `needle` is removed from the
     *      end of `self`. Otherwise, `self` is unmodified.
     * @param self The slice to operate on.
     * @param needle The slice to search for.
     * @return `self`
     */
    function until(slice memory self, slice memory needle) internal pure returns (slice memory) {
        if (self._len < needle._len) {
            return self;
        }

        uint256 selfptr = self._ptr + self._len - needle._len;
        bool equal = true;
        if (selfptr != needle._ptr) {
            assembly {
                let length := mload(needle)
                let needleptr := mload(add(needle, 0x20))
                equal := eq(keccak256(selfptr, length), keccak256(needleptr, length))
            }
        }

        if (equal) {
            self._len -= needle._len;
        }

        return self;
    }

    // Returns the memory address of the first byte of the first occurrence of
    // `needle` in `self`, or the first byte after `self` if not found.
    function findPtr(
        uint256 selflen,
        uint256 selfptr,
        uint256 needlelen,
        uint256 needleptr
    ) private pure returns (uint256) {
        uint256 ptr = selfptr;
        uint256 idx;

        if (needlelen <= selflen) {
            if (needlelen <= 32) {
                bytes32 mask;
                if (needlelen > 0) {
                    mask = bytes32(~(2 ** (8 * (32 - needlelen)) - 1));
                }

                bytes32 needledata;
                assembly {
                    needledata := and(mload(needleptr), mask)
                }

                uint256 end = selfptr + selflen - needlelen;
                bytes32 ptrdata;
                assembly {
                    ptrdata := and(mload(ptr), mask)
                }

                while (ptrdata != needledata) {
                    if (ptr >= end) return selfptr + selflen;
                    ptr++;
                    assembly {
                        ptrdata := and(mload(ptr), mask)
                    }
                }
                return ptr;
            } else {
                // For long needles, use hashing
                bytes32 hash;
                assembly {
                    hash := keccak256(needleptr, needlelen)
                }

                for (idx = 0; idx <= selflen - needlelen; idx++) {
                    bytes32 testHash;
                    assembly {
                        testHash := keccak256(ptr, needlelen)
                    }
                    if (hash == testHash) return ptr;
                    ptr += 1;
                }
            }
        }
        return selfptr + selflen;
    }

    // Returns the memory address of the first byte after the last occurrence of
    // `needle` in `self`, or the address of `self` if not found.
    function rfindPtr(
        uint256 selflen,
        uint256 selfptr,
        uint256 needlelen,
        uint256 needleptr
    ) private pure returns (uint256) {
        uint256 ptr;

        if (needlelen <= selflen) {
            if (needlelen <= 32) {
                bytes32 mask;
                if (needlelen > 0) {
                    mask = bytes32(~(2 ** (8 * (32 - needlelen)) - 1));
                }

                bytes32 needledata;
                assembly {
                    needledata := and(mload(needleptr), mask)
                }

                ptr = selfptr + selflen - needlelen;
                bytes32 ptrdata;
                assembly {
                    ptrdata := and(mload(ptr), mask)
                }

                while (ptrdata != needledata) {
                    if (ptr <= selfptr) return selfptr;
                    ptr--;
                    assembly {
                        ptrdata := and(mload(ptr), mask)
                    }
                }
                return ptr + needlelen;
            } else {
                // For long needles, use hashing
                bytes32 hash;
                assembly {
                    hash := keccak256(needleptr, needlelen)
                }
                ptr = selfptr + (selflen - needlelen);
                while (ptr >= selfptr) {
                    bytes32 testHash;
                    assembly {
                        testHash := keccak256(ptr, needlelen)
                    }
                    if (hash == testHash) return ptr + needlelen;
                    ptr -= 1;
                }
            }
        }
        return selfptr;
    }

    /*
     * @dev Modifies `self` to contain everything from the first occurrence of
     *      `needle` to the end of the slice. `self` is set to the empty slice
     *      if `needle` is not found.
     * @param self The slice to search and modify.
     * @param needle The text to search for.
     * @return `self`.
     */
    function find(slice memory self, slice memory needle) internal pure returns (slice memory) {
        uint256 ptr = findPtr(self._len, self._ptr, needle._len, needle._ptr);
        self._len -= ptr - self._ptr;
        self._ptr = ptr;
        return self;
    }

    /*
     * @dev Modifies `self` to contain the part of the string from the start of
     *      `self` to the end of the first occurrence of `needle`. If `needle`
     *      is not found, `self` is set to the empty slice.
     * @param self The slice to search and modify.
     * @param needle The text to search for.
     * @return `self`.
     */
    function rfind(slice memory self, slice memory needle) internal pure returns (slice memory) {
        uint256 ptr = rfindPtr(self._len, self._ptr, needle._len, needle._ptr);
        self._len = ptr - self._ptr;
        return self;
    }

    /*
     * @dev Splits the slice, setting `self` to everything after the first
     *      occurrence of `needle`, and `token` to everything before it. If
     *      `needle` does not occur in `self`, `self` is set to the empty slice,
     *      and `token` is set to the entirety of `self`.
     * @param self The slice to split.
     * @param needle The text to search for in `self`.
     * @param token An output parameter to which the first token is written.
     * @return `token`.
     */
    function split(slice memory self, slice memory needle, slice memory token) internal pure returns (slice memory) {
        uint256 ptr = findPtr(self._len, self._ptr, needle._len, needle._ptr);
        token._ptr = self._ptr;
        token._len = ptr - self._ptr;
        if (ptr == self._ptr + self._len) {
            // Not found
            self._len = 0;
        } else {
            self._len -= token._len + needle._len;
            self._ptr = ptr + needle._len;
        }
        return token;
    }

    /*
     * @dev Splits the slice, setting `self` to everything after the first
     *      occurrence of `needle`, and returning everything before it. If
     *      `needle` does not occur in `self`, `self` is set to the empty slice,
     *      and the entirety of `self` is returned.
     * @param self The slice to split.
     * @param needle The text to search for in `self`.
     * @return The part of `self` up to the first occurrence of `delim`.
     */
    function split(slice memory self, slice memory needle) internal pure returns (slice memory token) {
        split(self, needle, token);
    }

    /*
     * @dev Splits the slice, setting `self` to everything before the last
     *      occurrence of `needle`, and `token` to everything after it. If
     *      `needle` does not occur in `self`, `self` is set to the empty slice,
     *      and `token` is set to the entirety of `self`.
     * @param self The slice to split.
     * @param needle The text to search for in `self`.
     * @param token An output parameter to which the first token is written.
     * @return `token`.
     */
    function rsplit(slice memory self, slice memory needle, slice memory token) internal pure returns (slice memory) {
        uint256 ptr = rfindPtr(self._len, self._ptr, needle._len, needle._ptr);
        token._ptr = ptr;
        token._len = self._len - (ptr - self._ptr);
        if (ptr == self._ptr) {
            // Not found
            self._len = 0;
        } else {
            self._len -= token._len + needle._len;
        }
        return token;
    }

    /*
     * @dev Splits the slice, setting `self` to everything before the last
     *      occurrence of `needle`, and returning everything after it. If
     *      `needle` does not occur in `self`, `self` is set to the empty slice,
     *      and the entirety of `self` is returned.
     * @param self The slice to split.
     * @param needle The text to search for in `self`.
     * @return The part of `self` after the last occurrence of `delim`.
     */
    function rsplit(slice memory self, slice memory needle) internal pure returns (slice memory token) {
        rsplit(self, needle, token);
    }

    /*
     * @dev Counts the number of nonoverlapping occurrences of `needle` in `self`.
     * @param self The slice to search.
     * @param needle The text to search for in `self`.
     * @return The number of occurrences of `needle` found in `self`.
     */
    function count(slice memory self, slice memory needle) internal pure returns (uint256 cnt) {
        uint256 ptr = findPtr(self._len, self._ptr, needle._len, needle._ptr) + needle._len;
        while (ptr <= self._ptr + self._len) {
            cnt++;
            ptr = findPtr(self._len - (ptr - self._ptr), ptr, needle._len, needle._ptr) + needle._len;
        }
    }

    /*
     * @dev Returns True if `self` contains `needle`.
     * @param self The slice to search.
     * @param needle The text to search for in `self`.
     * @return True if `needle` is found in `self`, false otherwise.
     */
    function contains(slice memory self, slice memory needle) internal pure returns (bool) {
        return rfindPtr(self._len, self._ptr, needle._len, needle._ptr) != self._ptr;
    }

    /*
     * @dev Returns a newly allocated string containing the concatenation of
     *      `self` and `other`.
     * @param self The first slice to concatenate.
     * @param other The second slice to concatenate.
     * @return The concatenation of the two strings.
     */
    function concat(slice memory self, slice memory other) internal pure returns (string memory) {
        string memory ret = new string(self._len + other._len);
        uint256 retptr;
        assembly {
            retptr := add(ret, 32)
        }
        memcpy(retptr, self._ptr, self._len);
        memcpy(retptr + self._len, other._ptr, other._len);
        return ret;
    }

    /*
     * @dev Joins an array of slices, using `self` as a delimiter, returning a
     *      newly allocated string.
     * @param self The delimiter to use.
     * @param parts A list of slices to join.
     * @return A newly allocated string containing all the slices in `parts`,
     *         joined with `self`.
     */
    function join(slice memory self, slice[] memory parts) internal pure returns (string memory) {
        if (parts.length == 0) return "";

        uint256 length = self._len * (parts.length - 1);
        for (uint256 i = 0; i < parts.length; i++) length += parts[i]._len;

        string memory ret = new string(length);
        uint256 retptr;
        assembly {
            retptr := add(ret, 32)
        }

        for (uint256 i = 0; i < parts.length; i++) {
            memcpy(retptr, parts[i]._ptr, parts[i]._len);
            retptr += parts[i]._len;
            if (i < parts.length - 1) {
                memcpy(retptr, self._ptr, self._len);
                retptr += self._len;
            }
        }

        return ret;
    }
}