// File: ./Strings.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

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

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

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

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

}

// File: ./SafeMath.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is no longer needed starting with Solidity 0.8. The compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// File: ./Context.sol



// SPDX-License-Identifier: MIT

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) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: ./Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./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 () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), msgSender);
    }

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

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

// File: ./Address.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

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

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (bool success, ) = recipient.call{ value: amount }("");
        require(success, "Address: unable to send value, recipient may have reverted");
    }

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

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

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

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

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

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

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

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

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

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

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: ./IERC165.sol



// SPDX-License-Identifier: MIT

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: ./ERC165.sol



// SPDX-License-Identifier: MIT

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: ./IERC721.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC165.sol";

/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(address from, address to, uint256 tokenId) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(address from, address to, uint256 tokenId) external;

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

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
      * @dev Safely transfers `tokenId` token from `from` to `to`.
      *
      * Requirements:
      *
      * - `from` cannot be the zero address.
      * - `to` cannot be the zero address.
      * - `tokenId` token must exist and be owned by `from`.
      * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
      * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
      *
      * Emits a {Transfer} event.
      */
    function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
}

// File: ./IERC721Enumerable.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

import "./IERC721.sol";

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {

    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns a token ID owned by `owner` at a given `index` of its token list.
     * Use along with {balanceOf} to enumerate all of ``owner``'s tokens.
     */
    function tokenOfOwnerByIndex(address owner, uint256 index) external view returns (uint256 tokenId);

    /**
     * @dev Returns a token ID at a given `index` of all the tokens stored by the contract.
     * Use along with {totalSupply} to enumerate all tokens.
     */
    function tokenByIndex(uint256 index) external view returns (uint256);
}

// File: ./IERC721Metadata.sol



// SPDX-License-Identifier: MIT

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: ./IERC721Receiver.sol



// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

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

// File: ./DoomCats.sol



// SPDX-License-Identifier: MIT

pragma solidity ^ 0.8.0;

import "./SafeMath.sol";
import "./Context.sol";
import "./Ownable.sol";
import "./Strings.sol";
import "./Address.sol";
import "./IERC165.sol";
import "./ERC165.sol";
import "./IERC721.sol";
import "./IERC721Enumerable.sol";
import "./IERC721Metadata.sol";
import "./IERC721Receiver.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;

	// Optional mapping for token URIs
	mapping(uint256 => string) private _tokenURIs;

	// Base URI
	string private _baseURI;

	/**
	 * @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: balance query for the zero address");
		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: owner query for nonexistent token");
		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) {
		require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");

		string memory _tokenURI = _tokenURIs[tokenId];
		string memory base = baseURI();

		// If there is no base URI, return the token URI.
		if (bytes(base).length == 0) {
			return _tokenURI;
		}
		// If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
		if (bytes(_tokenURI).length > 0) {
			return string(abi.encodePacked(base, _tokenURI));
		}
		// If there is a baseURI but no tokenURI, concatenate the tokenID to the baseURI.
		return string(abi.encodePacked(base, tokenId.toString()));
	}

	/**
	 * @dev Base URI for computing {tokenURI}. Empty by default, can be overriden
	 * in child contracts.
	 */
	function baseURI() internal view virtual returns(string memory) {
		return _baseURI;
	}

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

		require(_msgSender() == owner || ERC721.isApprovedForAll(owner, _msgSender()),
			"ERC721: approve caller is not owner nor approved for all"
		);

		_approve(to, tokenId);
	}

	/**
	 * @dev See {IERC721-getApproved}.
	 */
	function getApproved(uint256 tokenId) public view virtual override returns(address) {
		require(_exists(tokenId), "ERC721: approved query for nonexistent token");

		return _tokenApprovals[tokenId];
	}

	/**
	 * @dev See {IERC721-setApprovalForAll}.
	 */
	function setApprovalForAll(address operator, bool approved) public virtual override {
		require(operator != _msgSender(), "ERC721: approve to caller");

		_operatorApprovals[_msgSender()][operator] = approved;
		emit ApprovalForAll(_msgSender(), operator, approved);
	}

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

	/**
	 * @dev See {IERC721-transferFrom}.
	 */
	function transferFrom(address from, address to, uint256 tokenId) public virtual override {
		//solhint-disable-next-line max-line-length
		require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

		_transfer(from, to, tokenId);
	}

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

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

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

	/**
	 * @dev Returns whether `tokenId` exists.
	 *
	 * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
	 *
	 * Tokens start existing when they are minted (`_mint`),
	 * and stop existing when they are burned (`_burn`).
	 */
	function _exists(uint256 tokenId) internal view virtual returns(bool) {
		return _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) {
		require(_exists(tokenId), "ERC721: operator query for nonexistent token");
		address owner = ERC721.ownerOf(tokenId);
		return (spender == owner || getApproved(tokenId) == spender || ERC721.isApprovedForAll(owner, spender));
	}

	/**
	 * @dev Safely mints `tokenId` and transfers it to `to`.
	 *
	 * Requirements:
	 *
	 * - `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);
	}

	/**
	 * @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);
	}

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

	/**
	 * @dev Sets `_tokenURI` as the tokenURI of `tokenId`.
	 *
	 * Requirements:
	 *
	 * - `tokenId` must exist.
	 */
	function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
		require(_exists(tokenId), "ERC721Metadata: URI set of nonexistent token");
		_tokenURIs[tokenId] = _tokenURI;
	}

	/**
	 * @dev Internal function to set the base URI for all token IDs. It is
	 * automatically added as a prefix to the value returned in {tokenURI},
	 * or to the token ID if {tokenURI} is empty.
	 */
	function _setBaseURI(string memory baseURI_) internal virtual {
		_baseURI = baseURI_;
	}

	/**
	 * @dev Approve `to` to operate on `tokenId`
	 *
	 * Emits a {Approval} event.
	 */
	function _approve(address to, uint256 tokenId) internal virtual {
		_tokenApprovals[tokenId] = to;
		emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
	}

	/**
	 * @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(to).onERC721Received.selector;
			} catch (bytes memory reason) {
				if (reason.length == 0) {
					revert("ERC721: transfer to non ERC721Receiver implementer");
				} else {
					// solhint-disable-next-line no-inline-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` cannot be the zero address.
	 * - `to` cannot be the zero address.
	 *
	 * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
	 */
	function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual { }
}

/**
 * @dev This implements an optional extension of {ERC721} defined in the EIP that adds
 * enumerability of all the token ids in the contract as well as all token ids owned by each
 * account.
 */
abstract contract ERC721Enumerable is ERC721, IERC721Enumerable {
	// Mapping from owner to list of owned token IDs
	mapping(address => mapping(uint256 => uint256)) private _ownedTokens;

	// Mapping from token ID to index of the owner tokens list
	mapping(uint256 => uint256) private _ownedTokensIndex;

	// Array with all token ids, used for enumeration
	uint256[] private _allTokens;

	// Mapping from token id to position in the allTokens array
	mapping(uint256 => uint256) private _allTokensIndex;

	/**
	 * @dev See {IERC165-supportsInterface}.
	 */
	function supportsInterface(bytes4 interfaceId) public view virtual override(IERC165, ERC721) returns(bool) {
		return interfaceId == type(IERC721Enumerable).interfaceId
			|| super.supportsInterface(interfaceId);
	}

	/**
	 * @dev See {IERC721Enumerable-tokenOfOwnerByIndex}.
	 */
	function tokenOfOwnerByIndex(address owner, uint256 index) public view virtual override returns(uint256) {
		require(index < ERC721.balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
		return _ownedTokens[owner][index];
	}

	/**
	 * @dev See {IERC721Enumerable-totalSupply}.
	 */
	function totalSupply() public view virtual override returns(uint256) {
		return _allTokens.length;
	}

	/**
	 * @dev See {IERC721Enumerable-tokenByIndex}.
	 */
	function tokenByIndex(uint256 index) public view virtual override returns(uint256) {
		require(index < ERC721Enumerable.totalSupply(), "ERC721Enumerable: global index out of bounds");
		return _allTokens[index];
	}

	/**
	 * @dev Hook that is called before any token transfer. This includes minting
	 * and burning.
	 *
	 * Calling conditions:
	 *
	 * - When `from` and `to` are both non-zero, ``from``'s `tokenId` will be
	 * transferred to `to`.
	 * - When `from` is zero, `tokenId` will be minted for `to`.
	 * - When `to` is zero, ``from``'s `tokenId` will be burned.
	 * - `from` cannot be the zero address.
	 * - `to` cannot be the zero address.
	 *
	 * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
	 */
	function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual override {
		super._beforeTokenTransfer(from, to, tokenId);

		if (from == address(0)) {
			_addTokenToAllTokensEnumeration(tokenId);
		} else if (from != to) {
			_removeTokenFromOwnerEnumeration(from, tokenId);
		}
		if (to == address(0)) {
			_removeTokenFromAllTokensEnumeration(tokenId);
		} else if (to != from) {
			_addTokenToOwnerEnumeration(to, tokenId);
		}
	}

	/**
	 * @dev Private function to add a token to this extension's ownership-tracking data structures.
	 * @param to address representing the new owner of the given token ID
	 * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
	 */
	function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
		uint256 length = ERC721.balanceOf(to);
		_ownedTokens[to][length] = tokenId;
		_ownedTokensIndex[tokenId] = length;
	}

	/**
	 * @dev Private function to add a token to this extension's token tracking data structures.
	 * @param tokenId uint256 ID of the token to be added to the tokens list
	 */
	function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
		_allTokensIndex[tokenId] = _allTokens.length;
		_allTokens.push(tokenId);
	}

	/**
	 * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
	 * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
	 * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
	 * This has O(1) time complexity, but alters the order of the _ownedTokens array.
	 * @param from address representing the previous owner of the given token ID
	 * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
	 */
	function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
		// To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
		// then delete the last slot (swap and pop).

		uint256 lastTokenIndex = ERC721.balanceOf(from) - 1;
		uint256 tokenIndex = _ownedTokensIndex[tokenId];

		// When the token to delete is the last token, the swap operation is unnecessary
		if (tokenIndex != lastTokenIndex) {
			uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];

			_ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
			_ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
		}

		// This also deletes the contents at the last position of the array
		delete _ownedTokensIndex[tokenId];
		delete _ownedTokens[from][lastTokenIndex];
	}

	/**
	 * @dev Private function to remove a token from this extension's token tracking data structures.
	 * This has O(1) time complexity, but alters the order of the _allTokens array.
	 * @param tokenId uint256 ID of the token to be removed from the tokens list
	 */
	function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
		// To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
		// then delete the last slot (swap and pop).

		uint256 lastTokenIndex = _allTokens.length - 1;
		uint256 tokenIndex = _allTokensIndex[tokenId];

		// When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
		// rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
		// an 'if' statement (like in _removeTokenFromOwnerEnumeration)
		uint256 lastTokenId = _allTokens[lastTokenIndex];

		_allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
		_allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index

		// This also deletes the contents at the last position of the array
		delete _allTokensIndex[tokenId];
		_allTokens.pop();
	}
}

contract DoomCats is ERC721Enumerable, Ownable {
	using SafeMath for uint256;
		uint256 public constant maxTokenSupply = 25440;
	uint256 private capThreshold = 25440;
	uint256 private startPrice = 1;
	uint256 private capPrice = 1;
	uint256 private maxQty = 1;
	bool public mintingAllowed = false;

	constructor() ERC721("DoomCats", "DoomCats") { }

	function getTokensOfOwner(address _owner) external view returns(uint256[] memory) {
		uint256 tokenCount = balanceOf(_owner);
		if (tokenCount == 0) {
			return new uint256[](0);
		} else {
			uint256[] memory result = new uint256[](tokenCount);
			uint256 index;
			for (index = 0; index < tokenCount; index++) {
				result[index] = tokenOfOwnerByIndex(_owner, index);
			}
			return result;
		}
	}

	function getPresaleQty() public view returns(uint256) {
		require(mintingAllowed == true, "Minting not allowed yet.");
		require(totalSupply() < maxTokenSupply, "All tokens have been minted.");

		return maxQty;
	}

	function getPresalePrice() public view returns(uint256) {
		require(mintingAllowed == true, "Minting not allowed yet.");
		require(totalSupply() < maxTokenSupply, "All tokens have been minted.");

		if (totalSupply() >= capThreshold)
			return capPrice * (10 ** 16);
		else if (totalSupply() / 1000 >= startPrice - 1)
			return (2 + (totalSupply() / 1000)) * (10 ** 16);
		else
			return startPrice * (10 ** 16);
	}

	function mintToken(uint256 qty) public payable {
		require(totalSupply() < maxTokenSupply, "All tokens have been minted.");
		require(qty > 0 && qty <= getPresaleQty(), "Quantity exceeds allowed.");
		require(totalSupply().add(qty) <= maxTokenSupply, "Quantity exceeds max supply.");
		require(msg.value >= getPresalePrice().mul(qty), "Ether value to send is insufficient.");

		for (uint256 i = 0; i < qty; i++) {
			uint mintIndex = totalSupply();
			_safeMint(msg.sender, mintIndex);
		}
	}

	function mintPromoToken(uint256 qty) public payable onlyOwner {
		// reserves 0-99 for giveaways
		require(totalSupply() < 100, "All promo tokens have been minted.");
		require(totalSupply().add(qty) < 100, "Quantity exceeds max promo supply.");

		for (uint256 i = 0; i < qty; i++) {
			uint mintIndex = totalSupply();
			_safeMint(msg.sender, mintIndex);
		}
	}

	function setPresaleAmounts(uint256 start, uint256 cap, uint256 qty, uint256 threshold) public onlyOwner {
		startPrice = start;
		capPrice = cap;
		capThreshold = threshold;
		maxQty = qty;
	}

	function setBaseURI(string memory baseURI) public onlyOwner {
		_setBaseURI(baseURI);
	}

	function beginPresale() public onlyOwner {
		mintingAllowed = true;
	}

	function pausePresale() public onlyOwner {
		mintingAllowed = false;
	}

	function withdraw() public payable onlyOwner {
		require(payable(msg.sender).send(address(this).balance));
	}
}