// 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/security/ReentrancyGuard.sol



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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 = _owners[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 nor 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 nor approved");

        _transfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }

    /**
     * @dev See {IERC721-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes memory data
    ) public virtual override {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: caller is not token owner nor approved");
        _safeTransfer(from, to, tokenId, data);
    }

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * `data` is additional data, it has no specified format and it is sent in call to `to`.
     *
     * This internal function is equivalent to {safeTransferFrom}, and can be used to e.g.
     * implement alternative mechanisms to perform token transfer, such as signature-based.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function _safeTransfer(
        address from,
        address to,
        uint256 tokenId,
        bytes memory data
    ) internal virtual {
        _transfer(from, to, tokenId);
        require(_checkOnERC721Received(from, to, tokenId, data), "ERC721: transfer to non ERC721Receiver implementer");
    }

    /**
     * @dev Returns whether `tokenId` exists.
     *
     * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
     *
     * Tokens start existing when they are minted (`_mint`),
     * and stop existing when they are burned (`_burn`).
     */
    function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _owners[tokenId] != address(0);
    }

    /**
     * @dev Returns whether `spender` is allowed to manage `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _isApprovedOrOwner(address spender, uint256 tokenId) internal view virtual returns (bool) {
        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);

        _balances[to] += 1;
        _owners[tokenId] = to;

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

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

    /**
     * @dev Destroys `tokenId`.
     * The approval is cleared when the token is burned.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     *
     * Emits a {Transfer} event.
     */
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId);

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

        // Clear approvals
        _approve(address(0), tokenId);

        _balances[owner] -= 1;
        delete _owners[tokenId];

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

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

    /**
     * @dev Transfers `tokenId` from `from` to `to`.
     *  As opposed to {transferFrom}, this imposes no restrictions on msg.sender.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     *
     * Emits a {Transfer} event.
     */
    function _transfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {
        require(ERC721.ownerOf(tokenId) == from, "ERC721: transfer from incorrect owner");
        require(to != address(0), "ERC721: transfer to the zero address");

        _beforeTokenTransfer(from, to, tokenId);

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

        _balances[from] -= 1;
        _balances[to] += 1;
        _owners[tokenId] = to;

        emit Transfer(from, to, tokenId);

        _afterTokenTransfer(from, to, tokenId);
    }

    /**
     * @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.
     *
     * Calling conditions:
     *
     * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
     * transferred to `to`.
     * - When `from` is zero, `tokenId` will be minted for `to`.
     * - When `to` is zero, ``from``'s `tokenId` will be burned.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero.
     * - `from` and `to` are never both zero.
     *
     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
     */
    function _afterTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}
}

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



// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (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: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

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

    /**
     * @dev 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/token/ERC721/extensions/IERC721Metadata.sol



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

pragma solidity ^0.8.0;

import "../IERC721.sol";

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

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

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

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



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

pragma solidity ^0.8.1;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 0;
    }

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

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

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

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

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

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

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

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

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

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

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

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

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

    /**
     * @dev Tool to verifies that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason using the provided one.
     *
     * _Available since v4.3._
     */
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly
                /// @solidity memory-safe-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// 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/Strings.sol



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

pragma solidity ^0.8.0;

/**
 * @dev String operations.
 */
library Strings {
    bytes16 private constant _HEX_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) {
        // Inspired by OraclizeAPI's implementation - MIT licence
        // https://github.com/oraclize/ethereum-api/blob/b42146b063c7d6ee1358846c198246239e9360e8/oraclizeAPI_0.4.25.sol

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

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

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

    /**
     * @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: @openzeppelin/contracts/utils/cryptography/ECDSA.sol



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

pragma solidity ^0.8.0;

import "../Strings.sol";

/**
 * @dev Elliptic Curve Digital Signature Algorithm (ECDSA) operations.
 *
 * These functions can be used to verify that a message was signed by the holder
 * of the private keys of a given address.
 */
library ECDSA {
    enum RecoverError {
        NoError,
        InvalidSignature,
        InvalidSignatureLength,
        InvalidSignatureS,
        InvalidSignatureV
    }

    function _throwError(RecoverError error) private pure {
        if (error == RecoverError.NoError) {
            return; // no error: do nothing
        } else if (error == RecoverError.InvalidSignature) {
            revert("ECDSA: invalid signature");
        } else if (error == RecoverError.InvalidSignatureLength) {
            revert("ECDSA: invalid signature length");
        } else if (error == RecoverError.InvalidSignatureS) {
            revert("ECDSA: invalid signature 's' value");
        } else if (error == RecoverError.InvalidSignatureV) {
            revert("ECDSA: invalid signature 'v' value");
        }
    }

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature` or error string. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     *
     * Documentation for signature generation:
     * - with https://web3js.readthedocs.io/en/v1.3.4/web3-eth-accounts.html#sign[Web3.js]
     * - with https://docs.ethers.io/v5/api/signer/#Signer-signMessage[ethers]
     *
     * _Available since v4.3._
     */
    function tryRecover(bytes32 hash, bytes memory signature) internal pure returns (address, RecoverError) {
        // Check the signature length
        // - case 65: r,s,v signature (standard)
        // - case 64: r,vs signature (cf https://eips.ethereum.org/EIPS/eip-2098) _Available since v4.1._
        if (signature.length == 65) {
            bytes32 r;
            bytes32 s;
            uint8 v;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            /// @solidity memory-safe-assembly
            assembly {
                r := mload(add(signature, 0x20))
                s := mload(add(signature, 0x40))
                v := byte(0, mload(add(signature, 0x60)))
            }
            return tryRecover(hash, v, r, s);
        } else if (signature.length == 64) {
            bytes32 r;
            bytes32 vs;
            // ecrecover takes the signature parameters, and the only way to get them
            // currently is to use assembly.
            /// @solidity memory-safe-assembly
            assembly {
                r := mload(add(signature, 0x20))
                vs := mload(add(signature, 0x40))
            }
            return tryRecover(hash, r, vs);
        } else {
            return (address(0), RecoverError.InvalidSignatureLength);
        }
    }

    /**
     * @dev Returns the address that signed a hashed message (`hash`) with
     * `signature`. This address can then be used for verification purposes.
     *
     * The `ecrecover` EVM opcode allows for malleable (non-unique) signatures:
     * this function rejects them by requiring the `s` value to be in the lower
     * half order, and the `v` value to be either 27 or 28.
     *
     * IMPORTANT: `hash` _must_ be the result of a hash operation for the
     * verification to be secure: it is possible to craft signatures that
     * recover to arbitrary addresses for non-hashed data. A safe way to ensure
     * this is by receiving a hash of the original message (which may otherwise
     * be too long), and then calling {toEthSignedMessageHash} on it.
     */
    function recover(bytes32 hash, bytes memory signature) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, signature);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `r` and `vs` short-signature fields separately.
     *
     * See https://eips.ethereum.org/EIPS/eip-2098[EIP-2098 short signatures]
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        bytes32 r,
        bytes32 vs
    ) internal pure returns (address, RecoverError) {
        bytes32 s = vs & bytes32(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
        uint8 v = uint8((uint256(vs) >> 255) + 27);
        return tryRecover(hash, v, r, s);
    }

    /**
     * @dev Overload of {ECDSA-recover} that receives the `r and `vs` short-signature fields separately.
     *
     * _Available since v4.2._
     */
    function recover(
        bytes32 hash,
        bytes32 r,
        bytes32 vs
    ) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, r, vs);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Overload of {ECDSA-tryRecover} that receives the `v`,
     * `r` and `s` signature fields separately.
     *
     * _Available since v4.3._
     */
    function tryRecover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address, RecoverError) {
        // EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature
        // unique. Appendix F in the Ethereum Yellow paper (https://ethereum.github.io/yellowpaper/paper.pdf), defines
        // the valid range for s in (301): 0 < s < secp256k1n ÷ 2 + 1, and for v in (302): v ∈ {27, 28}. Most
        // signatures from current libraries generate a unique signature with an s-value in the lower half order.
        //
        // If your library generates malleable signatures, such as s-values in the upper range, calculate a new s-value
        // with 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 - s1 and flip v from 27 to 28 or
        // vice versa. If your library also generates signatures with 0/1 for v instead 27/28, add 27 to v to accept
        // these malleable signatures as well.
        if (uint256(s) > 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0) {
            return (address(0), RecoverError.InvalidSignatureS);
        }
        if (v != 27 && v != 28) {
            return (address(0), RecoverError.InvalidSignatureV);
        }

        // If the signature is valid (and not malleable), return the signer address
        address signer = ecrecover(hash, v, r, s);
        if (signer == address(0)) {
            return (address(0), RecoverError.InvalidSignature);
        }

        return (signer, RecoverError.NoError);
    }

    /**
     * @dev Overload of {ECDSA-recover} that receives the `v`,
     * `r` and `s` signature fields separately.
     */
    function recover(
        bytes32 hash,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal pure returns (address) {
        (address recovered, RecoverError error) = tryRecover(hash, v, r, s);
        _throwError(error);
        return recovered;
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from a `hash`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
        // 32 is the length in bytes of hash,
        // enforced by the type signature above
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
    }

    /**
     * @dev Returns an Ethereum Signed Message, created from `s`. This
     * produces hash corresponding to the one signed with the
     * https://eth.wiki/json-rpc/API#eth_sign[`eth_sign`]
     * JSON-RPC method as part of EIP-191.
     *
     * See {recover}.
     */
    function toEthSignedMessageHash(bytes memory s) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n", Strings.toString(s.length), s));
    }

    /**
     * @dev Returns an Ethereum Signed Typed Data, created from a
     * `domainSeparator` and a `structHash`. This produces hash corresponding
     * to the one signed with the
     * https://eips.ethereum.org/EIPS/eip-712[`eth_signTypedData`]
     * JSON-RPC method as part of EIP-712.
     *
     * See {recover}.
     */
    function toTypedDataHash(bytes32 domainSeparator, bytes32 structHash) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("\x19\x01", domainSeparator, structHash));
    }
}

// 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: contracts/Loretests.sol



// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.0;


import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
// import "hardhat/console.sol";

interface IOracle{
    function request() external returns (uint64 key);
    function getRandom(uint64 id) external view returns(uint256 rand);
}

contract Loretests is Ownable, ReentrancyGuard, ERC721 {

    using Strings for uint;
    using Counters for Counters.Counter;
    using ECDSA for bytes32;

    Counters.Counter private _tokenId;
    address private signer; // signer to make signature
    string public notRevealedUri;

    // SALES
    bool public presaleActive = false;
    bool public publicSaleActive = false;
    bool public paused = false;

    uint256 public cost = 0.0001 ether;
    uint256 public maxSupply = 50;
    uint256 public maxMintAmount = 2;
    bool public revealed = false;

    mapping(address => uint256) public whitelistMinted; // address => amount

    // list of probabilities for each trait type
    // 0-5: [Wizard, Rainbow, Plant (bark colors), Water, Fire, Ice]
    //      0-3: [clothes, expression, head, background]
    mapping(uint8 => uint8[][4]) public rarities;
    mapping(uint8 => uint8[][4]) public aliases;
    uint8[] public raritiesFaction;
    uint8[] public aliasesFaction;
    // mapping from hashed(tokenTrait) to the tokenId it's associated with
    // used to ensure there are no duplicates
    mapping(uint256 => uint256) public existingCombinations;

    IOracle public oracle;
    bytes32 internal entropySauce;

    mapping(uint256 => uint256) public mintBlocks;
    mapping(uint256 => Loretest) internal loretests;

    // Flag for allowing or not allowing locking
    bool public lockingOpen = false;
    // tokenId to locking start time (0 = not locking).
    mapping(uint256 => uint256) private lockingStarted;
    // Cumulative per-token locking, excluding the current period.
    mapping(uint256 => uint256) private lockingTotal;
    uint256 public totalLockedCount;

    /** DATA STRUCTURE */
    struct Loretest {
        uint8 base;
        uint8 clothes;
        uint8 expression;
        uint8 head;
        uint8 background;
    }

    /** EVENTS */
    event BaseURISet(string baseURI);
    event OracleChanged(IOracle oracle);
    event SignerChanged(address signer);
    event PublicSaleStatusChanged(bool isActive);
    event PresaleStatusChanged(bool isActive);
    event NotRevealedUriChanged(string uri);
    event MaxMintAmountChanged(uint256 amount);
    event CostChanged(uint256 cost);
    event Paused(bool isPaused);
    event Revealed();

    // Emitted when a token begins locking.
    event Locked(uint256 indexed tokenId);
    // Emitted when a token stops locking; either through standard means or
    event UnLocked(uint256 indexed tokenId);
    // Emitted when a token is expelled from the locking.
    event Expelled(uint256 indexed tokenId);


    constructor(string memory _initNotRevealedUri) ERC721("Loretests", "LTS") {
        setNotRevealedURI(_initNotRevealedUri);
        signer = msg.sender;

        // We'll use the last caller hash to add entropy to next caller
        entropySauce = keccak256(abi.encodePacked(msg.sender, block.timestamp, block.coinbase));

        raritySetup();
    }

    function raritySetup() internal {
        // I know this looks weird but it saves users gas by making lookup O(1)
        // A.J. Walker's Alias Algorithm
        // Faction: [0.18, 0.1, 0.18, 0.18, 0.18, 0.18]
        raritiesFaction = [173, 153, 193, 214, 234, 254];
        aliasesFaction = [2, 0, 3, 4, 5, 5];
        // Wizard
        //      clothes: [0.18, 0.2, 0.14, 0.15, 0.08, 0.25]
        rarities[0][0] =[234, 147, 214, 229, 122, 255];
        aliases[0][0] = [5, 5, 0, 1, 1, 5];
        //      expression: [0.25, 0.09, 0.21, 0.19, 0.08, 0.18]
        rarities[0][1] = [132, 137, 198, 234, 122, 255];
        aliases[0][1] = [2, 0, 3, 5, 0, 5];
        //      head: [0.15, 0.17, 0.13, 0.16, 0.19, 0.2]
        rarities[0][2] = [229, 234, 198, 244, 234, 255];
        aliases[0][2] = [1, 5, 4, 5, 5, 5];
        //      background: [0.15, 0.2, 0.18, 0.25, 0.08, 0.14]
        rarities[0][3] = [229, 147, 234, 255, 122, 214];
        aliases[0][3] = [1, 3, 3, 5, 1, 2];

        // Rainbow
        //      clothes: [0.25, 0.18, 0.2, 0.14, 0.15, 0.08]
        rarities[1][0] =[183, 204, 255, 214, 229, 122];
        aliases[1][0] = [1, 2, 5, 0, 0, 0];
        //      expression: [0.2, 0.2, 0.18, 0.16, 0.12, 0.14]
        rarities[1][1] = [224, 249, 244, 244, 183, 198];
        aliases[1][1] = [2, 5, 5, 0, 0, 1];
        //      head: [0.15, 0.17, 0.13, 0.16, 0.19, 0.20]
        rarities[1][2] = [229, 234, 198, 244, 234, 255];
        aliases[1][2] = [1, 5, 4, 5, 5, 5];
        //      background: [0.15, 0.16, 0.14, 0.16, 0.14, 0.25]
        rarities[1][3] = [229, 244, 214, 244, 214, 255];
        aliases[1][3] = [5, 5, 5, 5, 5, 5];

        // Plant (bark colors)
        //      clothes: [0.05, 0.19, 0.19, 0.19, 0.19, 0.19]
        rarities[2][0] = [76, 112, 147, 183, 219, 255];
        aliases[2][0] = [1, 2, 3, 4, 5, 5];
        //      expression: [0.2, 0.2, 0.18, 0.16, 0.12, 0.14]
        rarities[2][1] = [224, 249, 244, 244, 183, 198];
        aliases[2][1] = [2, 5, 5, 0, 0, 1];
        //      head: [0.15, 0.17, 0.13, 0.16, 0.19, 0.2]
        rarities[2][2] = [229, 234, 198, 244, 234, 255];
        aliases[2][2] = [1, 5, 4, 5, 5, 5];
        //      background: [0.15, 0.2, 0.16, 0.25, 0.14, 0.1]
        rarities[2][3] = [229, 229, 244, 255, 214, 153];
        aliases[2][3] = [1, 3, 1, 5, 1, 3];

        // Water
        //      clothes: [0.25, 0.2, 0.14, 0.12, 0.19, 0.1]
        rarities[3][0] = [168, 219, 214, 183, 239, 153];
        aliases[3][0] = [1, 4, 0, 0, 5, 0];
        //      expression: [0.2, 0.2, 0.18, 0.16, 0.12, 0.14]
        rarities[3][1] = [224, 249, 244, 244, 183, 198];
        aliases[3][1] = [2, 5, 5, 0, 0, 1];
        //      head: [0.15, 0.17, 0.13, 0.16, 0.19, 0.2]
        rarities[3][2] = [229, 234, 198, 244, 234, 255];
        aliases[3][2] = [1, 5, 4, 5, 5, 5];
        //      background: [0.15, 0.2, 0.25, 0.18, 0.1, 0.12]
        rarities[3][3] = [229, 178, 234, 255, 153, 183];
        aliases[3][3] = [1, 2, 3, 5, 1, 2];

        // Fire
        //      clothes: [0.25, 0.18, 0.15, 0.14, 0.2, 0.08]
        rarities[4][0] = [183, 204, 229, 214, 255, 122];
        aliases[4][0] = [1, 4, 0, 0, 5, 0];
        //      expression: [0.2, 0.2, 0.18, 0.16, 0.12, 0.14]
        rarities[4][1] = [224, 249, 244, 244, 183, 198];
        aliases[4][1] = [2, 5, 5, 0, 0, 1];
        //      head: [0.15, 0.17, 0.13, 0.16, 0.19, 0.2]
        rarities[4][2] = [229, 234, 198, 244, 234, 255];
        aliases[4][2] = [1, 5, 4, 5, 5, 5];
        //      background: [0.15, 0.25, 0.2, 0.15, 0.09, 0.16]
        rarities[4][3] = [229, 214, 254, 229, 137, 244];
        aliases[4][3] = [1, 2, 5, 1, 1, 2];

        // Ice
        //      clothes: [0.25, 0.18, 0.2, 0.14, 0.15, 0.08]
        rarities[5][0] = [183, 204, 255, 214, 229, 122];
        aliases[5][0] = [1, 2, 5, 0, 0, 0];
        //      expression: [0.2, 0.2, 0.18, 0.16, 0.12, 0.14]
        rarities[5][1] = [224, 249, 244, 244, 183, 198];
        aliases[5][1] = [2, 5, 5, 0, 0, 1];
        //      head: [0.15, 0.17, 0.13, 0.16, 0.19, 0.2]
        rarities[5][2] = [229, 234, 198, 244, 234, 255];
        aliases[5][2] = [1, 5, 4, 5, 5, 5];
        //      background: [0.15, 0.2, 0.25, 0.18, 0.1, 0.12]
        rarities[5][3] = [229, 178, 234, 255, 153, 183];
        aliases[5][3] = [1, 2, 3, 5, 1, 2];
    }

    // MODIFIERS
    modifier notPaused {
         require(!paused, "Contract paused");
         _;
    }

    modifier noCheaters() {
        uint256 size = 0;
        address acc = msg.sender;
        assembly {
            size := extcodesize(acc)
        }

        require(
            // (owner() == msg.sender) || (msg.sender == tx.origin && size == 0),
            (owner() == msg.sender) || (size == 0),
            "you're trying to cheat!"
        );
        _;

        // We'll use the last caller hash to add entropy to next caller
        entropySauce = keccak256(abi.encodePacked(acc, block.coinbase, entropySauce));
    }

    modifier validateCostMintAmount(uint256 _mintAmount) {
        require(msg.value >= cost * _mintAmount, "Insufficient funds");
        require(_mintAmount > 0, "Need to mint at least 1 NFT");
        require(_mintAmount + _tokenId.current() <= maxSupply, "Max supply exceeded");
        _;
    }

    // Public Methods

    function mint1(uint256 _mintAmount, bytes memory _signature) public payable notPaused nonReentrant noCheaters validateCostMintAmount(_mintAmount) {
        require(presaleActive == true, "Presale has not started yet");
        require(_isValidSignature(msg.sender, _signature) == true, "Not whitelisted");
        require(_mintAmount + whitelistMinted[msg.sender] <= maxMintAmount, "Max mint amount exceeded");

        whitelistMinted[msg.sender] += _mintAmount;
        for (uint256 i = 1; i <= _mintAmount; i++) {
            _mintLoretest(msg.sender);
        }
    }

    function mintPublic(uint256 _mintAmount) public payable notPaused nonReentrant noCheaters validateCostMintAmount(_mintAmount) {
        require(publicSaleActive == true, "Public sale has not started yet");
        require(_mintAmount <= maxMintAmount, "Max mint amount exceeded");

        for (uint256 i = 1; i <= _mintAmount; i++) {
            _mintLoretest(msg.sender);
        }
    }

    function mintReserve(uint _mintAmount, address _to) external notPaused onlyOwner noCheaters {
        require(_mintAmount + _tokenId.current() <= maxSupply, "Max supply exceeded");
        for (uint i =0; i < _mintAmount; i++) {
            _mintLoretest(_to);
        }
    }

    // PUBLIC VIEWS

    function currentTokenID() external view returns(uint){
        return _tokenId.current();
    }

    function totalSupply() public view virtual returns (uint256) {
        return _tokenId.current();
    }

    function getSigner() public view returns (address) {
        return signer;
    }

    /**
    @dev Don't use this method in other calls and contracts.
     */
    function walletOfOwner(address _owner) public view returns (uint256[] memory) {
        uint256 ownerTokenCount = balanceOf(_owner);
        uint256[] memory tokenIds = new uint256[](ownerTokenCount);
        uint256 id_ = 0;
        for (uint256 i = 1; i <= _tokenId.current(); i++) {
            if(ownerOf(i) == _owner) tokenIds[id_++] = i;
        }
        return tokenIds;
    }

    // Returns the length of time, in seconds, that the token has locked.
    function lockingPeriod(uint256 tokenId) external view returns (bool locking, uint256 current, uint256 total){
        uint256 start = lockingStarted[tokenId];
        if (start != 0) {
            locking = true;
            current = block.timestamp - start;
        }
        total = current + lockingTotal[tokenId];
    }

    // Changes the tokens' locking status (what's the plural of status?
    function toggleLocking(uint256[] calldata tokenIds) external {
        uint256 n = tokenIds.length;
        for (uint256 i = 0; i < n; ++i) {
            toggleLocking(tokenIds[i]);
        }
    }

    function toggleLocking(uint256 tokenId) internal {
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: caller is not token owner nor approved");
        uint256 start = lockingStarted[tokenId];
        if (start == 0) {
            require(lockingOpen, "locking closed");
            lockingStarted[tokenId] = block.timestamp;
            totalLockedCount ++;
            emit Locked(tokenId);
        } else {
            lockingTotal[tokenId] += block.timestamp - start;
            lockingStarted[tokenId] = 0;
            totalLockedCount --;
            emit UnLocked(tokenId);
        }
    }

    // @notice Admin-only ability to expel a token from the locking.
    function expelFromLocking(uint256 tokenId) external onlyOwner() {
        require(lockingStarted[tokenId] != 0, "Not locked");
        lockingTotal[tokenId] += block.timestamp - lockingStarted[tokenId];
        lockingStarted[tokenId] = 0;
        totalLockedCount --;
        emit UnLocked(tokenId);
        emit Expelled(tokenId);
    }

    /**
    @dev MUST only be modified by safeTransferWhileLocking(); if set to 2 then
    the _beforeTokenTransfer() block while locking is disabled.
     */
    uint256 private lockingTransfer = 1;

    /**
    @notice Transfer a token between addresses while the loretest is minting,
    thus not resetting the locking period.
     */
    function safeTransferWhileLocking(
        address from,
        address to,
        uint256 tokenId
    ) external {
        require(ownerOf(tokenId) == _msgSender(), "Only owner");
        lockingTransfer = 2;
        safeTransferFrom(from, to, tokenId);
        lockingTransfer = 1;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint tokenId) public view override(ERC721) returns (string memory) {
        require(_exists(tokenId), "Cannot query non-existent token");

        if (!revealed) {
            return notRevealedUri;
        }

        return super.tokenURI(tokenId);
    }

    function getAttributes(uint256 tokenId) public view returns (Loretest memory) {
        require(_exists(tokenId), "Cannot query non-existent token");
        require(mintBlocks[tokenId] != block.number, "Cannot query traits");
        return loretests[tokenId];
    }
    
    /**
    * initiate random factor
    */
    uint64 key;
    uint256 randomResult;
    function requestRandomFactor() external onlyOwner {
        key = oracle.request();
    }

    function finalizeRandomFactor() external onlyOwner {
        require(key != 0, "not requested");
        randomResult = oracle.getRandom(key);
        require(randomResult != 0, "too soon");
        entropySauce = keccak256(abi.encodePacked(msg.sender, block.coinbase, randomResult, entropySauce));
        randomResult = 0;
        key = 0;
    }

    // ONLY OWNER SETTERS
    function setBaseURI(string calldata baseURI) external onlyOwner {
        _baseTokenURI = baseURI;
        emit BaseURISet(baseURI);
    }

    // Toggles the `lockingOpen` flag.
    function setLockingOpen(bool open) external onlyOwner {
        lockingOpen = open;
    }

    function setOracle(IOracle _oracle) external onlyOwner {
        oracle = _oracle;
        emit OracleChanged(_oracle);
    }

    function reveal() public onlyOwner {
        revealed = true;
        emit Revealed();
    }

    function pause(bool _state) public onlyOwner {
        paused = _state;
        emit Paused(_state);
    }

    function setCost(uint256 _newCost) public onlyOwner {
        cost = _newCost;
        emit CostChanged(_newCost);
    }

    function setmaxMintAmount(uint256 _newmaxMintAmount) public onlyOwner {
        maxMintAmount = _newmaxMintAmount;
        emit MaxMintAmountChanged(_newmaxMintAmount);
    }

    function setNotRevealedURI(string memory _notRevealedURI) public onlyOwner {
        notRevealedUri = _notRevealedURI;
        emit NotRevealedUriChanged(_notRevealedURI);
    }

    function setPresaleStatus(bool _saleActive) public onlyOwner {
        presaleActive = _saleActive;
        emit PresaleStatusChanged(_saleActive);
    }

    function setPublicSaleStatus(bool _saleActive) public onlyOwner {
        publicSaleActive = _saleActive;
        emit PublicSaleStatusChanged(_saleActive);
    }

    function setSigner(address signer_) public onlyOwner {
        signer = signer_;
        emit SignerChanged(signer_);
    }

    function withdraw(address receiver_) public payable onlyOwner {
        (bool success, ) = payable(receiver_).call{value: address(this).balance}("");
        require(success, "Transfer failed");
    }

    // metadata URI
    string private _baseTokenURI;

    function _baseURI() internal view virtual override returns (string memory) {
        return _baseTokenURI;
    }
    
    /**
    @dev Block transfers while locking.
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual override {
        require(
            lockingStarted[tokenId] == 0 || lockingTransfer == 2,
            "locking"
        );
    }

    // Internal Helper Methods

    function _mintLoretest(address to) internal {
        _tokenId.increment();
        uint256 id = _tokenId.current();
        mintBlocks[id] = block.number;
        uint256 seed = _random(id);
        generate(id, seed);
        _mint(to, id);
    }
    
    /**
    * generates traits for a specific token, checking to make sure it's unique
    * @param tokenId the id of the token to generate traits for
    * @param seed a pseudorandom 256 bit number to derive traits from
    * @return t - a struct of traits for the given token ID
    */
    function generate(uint256 tokenId, uint256 seed) internal returns (Loretest memory t) {
        t = selectTraits(seed);
        loretests[tokenId] = t;
        return t;

        // keep the following code for future use, current version using different seed, so no need for now
        // if (existingCombinations[structToHash(t)] == 0) {
        //     loretests[tokenId] = t;
        //     existingCombinations[structToHash(t)] = tokenId;
        //     return t;
        // }
        // return generate(tokenId, random(seed));
    }

    /**
    * uses A.J. Walker's Alias algorithm for O(1) rarity table lookup
    * ensuring O(1) instead of O(n) reduces mint cost by more than 50%
    * probability & alias tables are generated off-chain beforehand
    * @param seed portion of the 256 bit seed to remove trait correlation
    * @param traitType the trait type to select a trait for 
    * @return the ID of the randomly selected trait
    */
    function selectTrait(uint16 seed, uint8 traitType, uint8 base) internal view returns (uint8) {
        if(traitType == 0) { // base
            uint8 trait = uint8(seed) % uint8(raritiesFaction.length);
            if (seed >> 8 < raritiesFaction[trait]) return trait;
            return aliasesFaction[trait];
        } else { // clothes, expression, head, background
            uint8 rid = traitType - 1;
            uint8 trait = uint8(seed) % uint8(rarities[base][rid].length);
            if (seed >> 8 < rarities[base][rid][trait]) return trait;
            return aliases[base][rid][trait];
        }
    }

    /**
    * selects the species and all of its traits based on the seed value
    * @param seed a pseudorandom 256 bit number to derive traits from
    * @return t -  a struct of randomly selected traits
    */
    function selectTraits(uint256 seed) internal view returns (Loretest memory t) {    
        t.base = selectTrait(uint16(seed & 0xFFFF), 0, 0);
        seed >>= 16;
        t.clothes = selectTrait(uint16(seed & 0xFFFF), 1, t.base);
        seed >>= 16;
        t.expression = selectTrait(uint16(seed & 0xFFFF), 2, t.base);
        seed >>= 16;
        t.head = selectTrait(uint16(seed & 0xFFFF), 3, t.base);
        seed >>= 16;
        t.background = selectTrait(uint16(seed & 0xFFFF), 4, t.base);
        seed >>= 16;
    }

    /**
    * converts a struct to a 256 bit hash to check for uniqueness
    * @param s the struct to pack into a hash
    * @return the 256 bit hash of the struct
    */
    function structToHash(Loretest memory s) internal pure returns (uint256) {
        return uint256(bytes32(
        abi.encodePacked(
            s.base,
            s.clothes,
            s.expression,
            s.head,
            s.background
        )
        ));
    }

    /// @dev Create a bit more of randomness
    // function _randomize(
    //     uint256 rand,
    //     string memory val,
    //     uint256 spicy
    // ) internal pure returns (uint256) {
    //     return uint256(keccak256(abi.encode(rand, val, spicy)));
    // }

    // function _rand() internal view returns (uint256) {
    //     return
    //         uint256(
    //             keccak256(
    //                 abi.encodePacked(
    //                     tx.origin,
    //                     blockhash(block.number - 1),
    //                     block.timestamp,
    //                     entropySauce
    //                 )
    //             )
    //         );
    // }

    /**
    * generates a pseudorandom number
    * @param seed a value ensure different outcomes for different sources in the same block
    * @return a pseudorandom value
    */
    function _random(uint256 seed) internal view returns (uint256) {
        return uint256(keccak256(abi.encodePacked(
            // tx.origin,
            blockhash(block.number - 1),
            block.timestamp,
            seed,
            entropySauce
        )));
    }

    function _isValidSignature(address user, bytes memory signature) internal view returns (bool) {
        bytes32 hash = keccak256(abi.encodePacked("whitelist", user));
        address signer_ = hash.toEthSignedMessageHash().recover(signature);
        return signer_ == signer;
    }

}