DCB World x BRITTO

/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: 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) {
        return msg.data;
    }
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: 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);
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

pragma solidity ^0.8.0;

////import "../utils/introspection/IERC165.sol";




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

pragma solidity ^0.8.0;

////import "../../utils/introspection/IERC165.sol";

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

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

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

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

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

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

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

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

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

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

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

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




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: 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;
    }
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

pragma solidity ^0.8.0;

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

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

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

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

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




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: 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;
        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");

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

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

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

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

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

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

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

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

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

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

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

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

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

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




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: 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);
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: 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);
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

pragma solidity ^0.8.0;

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

/**
 * @dev Contract module which allows children to implement an emergency stop
 * mechanism that can be triggered by an authorized account.
 *
 * This module is used through inheritance. It will make available the
 * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
 * the functions of your contract. Note that they will not be pausable by
 * simply including this module, only once the modifiers are put in place.
 */
abstract contract Pausable is Context {
    /**
     * @dev Emitted when the pause is triggered by `account`.
     */
    event Paused(address account);

    /**
     * @dev Emitted when the pause is lifted by `account`.
     */
    event Unpaused(address account);

    bool private _paused;

    /**
     * @dev Initializes the contract in unpaused state.
     */
    constructor() {
        _paused = false;
    }

    /**
     * @dev Returns true if the contract is paused, and false otherwise.
     */
    function paused() public view virtual returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    modifier whenNotPaused() {
        require(!paused(), "Pausable: paused");
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    modifier whenPaused() {
        require(paused(), "Pausable: not paused");
        _;
    }

    /**
     * @dev Triggers stopped state.
     *
     * Requirements:
     *
     * - The contract must not be paused.
     */
    function _pause() internal virtual whenNotPaused {
        _paused = true;
        emit Paused(_msgSender());
    }

    /**
     * @dev Returns to normal state.
     *
     * Requirements:
     *
     * - The contract must be paused.
     */
    function _unpause() internal virtual whenPaused {
        _paused = false;
        emit Unpaused(_msgSender());
    }
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

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: 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 baseURI = _baseURI();
        return bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : "";
    }

    /**
     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
     * by default, can be overriden in child contracts.
     */
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    /**
     * @dev See {IERC721-approve}.
     */
    function approve(address to, uint256 tokenId) public 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 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 || 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 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.onERC721Received.selector;
            } catch (bytes memory reason) {
                if (reason.length == 0) {
                    revert("ERC721: transfer to non ERC721Receiver implementer");
                } else {
                    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 {}
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: 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);
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

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 make 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;
    }
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: 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. 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;
        }
    }
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

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

    function _setOwner(address newOwner) private {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

pragma solidity ^0.8.0;

////import "./IERC165.sol";

/**
 * @dev Interface for the NFT Royalty Standard
 */
interface IERC2981 is IERC165 {
    /**
     * @dev Called with the sale price to determine how much royalty is owed and to whom.
     * @param tokenId - the NFT asset queried for royalty information
     * @param salePrice - the sale price of the NFT asset specified by `tokenId`
     * @return receiver - address of who should be sent the royalty payment
     * @return royaltyAmount - the royalty payment amount for `salePrice`
     */
    function royaltyInfo(uint256 tokenId, uint256 salePrice)
        external
        view
        returns (address receiver, uint256 royaltyAmount);
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

pragma solidity ^0.8.0;

////import "../ERC721.sol";
////import "../../../security/Pausable.sol";

/**
 * @dev ERC721 token with pausable token transfers, minting and burning.
 *
 * Useful for scenarios such as preventing trades until the end of an evaluation
 * period, or having an emergency switch for freezing all token transfers in the
 * event of a large bug.
 */
abstract contract ERC721Pausable is ERC721, Pausable {
    /**
     * @dev See {ERC721-_beforeTokenTransfer}.
     *
     * Requirements:
     *
     * - the contract must not be paused.
     */
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual override {
        super._beforeTokenTransfer(from, to, tokenId);

        require(!paused(), "ERC721Pausable: token transfer while paused");
    }
}




/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/
            
////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT

pragma solidity ^0.8.0;

////import "../ERC721.sol";
////import "./IERC721Enumerable.sol";

/**
 * @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();
    }
}


/** 
 *  SourceUnit: c:\Users\Jad\Documents\code\Cryptoware\dcb-lottery\blockend\contracts\DCBW721.sol
*/

////// SPDX-License-Identifier-FLATTEN-SUPPRESS-WARNING: MIT
pragma solidity ^0.8.0;

/// @notice ERC721
////import "../node_modules/@openzeppelin/contracts/token/ERC721/ERC721.sol";
////import "../node_modules/@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
////import "../node_modules/@openzeppelin/contracts/token/ERC721/extensions/ERC721Pausable.sol";
////import "../node_modules/@openzeppelin/contracts/interfaces/IERC2981.sol";

/// @notice peripheral
////import "../node_modules/@openzeppelin/contracts/access/Ownable.sol";

/// @notice libraries
////import "../node_modules/@openzeppelin/contracts/utils/math/SafeMath.sol";

/// @notice 
////import "../node_modules/@openzeppelin/contracts/security/ReentrancyGuard.sol";

/// @notice RNG middleware contract interface
interface IRNG {
    function request() external returns(bytes32 requestId);
}

/**
 * @title DCBW721
 * @notice ERC721-ready VRF DCBW721 contract
 * @author cryptoware.eth | DCB.world
 **/
contract DCBW721 is IERC2981, Ownable, ERC721, ERC721Enumerable, ERC721Pausable, ReentrancyGuard {
    /// @notice using safe math for uints
    using SafeMath for uint256;

    /// @notice using safe math for uints
    using SafeMath for uint32;

    /// @notice using safe math for uints
    using SafeMath for uint64;

    /// @notice using safe math for uints
    using SafeMath for uint96;

    /// @notice using Strings for uints conversion (tokenId)
    using Strings for uint256;

    /// @notice using Address for addresses extended functionality
    using Address for address;

    /// @notice sate of the draw process
    enum DrawState {
        Open,
        Closed
    }

    /// @notice struct used to store each draw's data
    struct DrawData {
        uint64 drawId;
        uint64 start_time;
        uint64 winningEdition;
        uint64 isGrandPrize;
        address winner;
        uint96 prizePoolWon;
        DrawState state;
        bytes32 randomNumberRequestId;
    }

    /// @notice EIP2981-compliant struct
    struct RoyaltyReceiver {
        address account;
        uint96 shares; // per thousands
    }

    /// @notice EIP721-required Base URI
    string private _baseTokenURI;

    /// @notice Base extension for metadata
    string private _baseExtension;

    /// @notice minting, draws, reserve(public), grandPrize(public) and royalties-traking parameters
    uint256 public _reserves;
    uint256 public _grandPrizePool;
    uint256 public _mintPrice;
    uint32 public _drawsToDate;

    uint256 private _reservesRate;
    uint256 private _maxTokenId;

    /// @notice the lottery draw state
    DrawState private _state;

    /// @notice beneficiary wallet that will collect mint fees
    address payable private _mintingBeneficiary;

    /// @notice VRF-compliant contract to request randomness from
    address private _rngContract;

    /// @notice Chainlink Keeper-compliant contract to trigger draw
    address private _alarmContract;

    /// @notice minter address
    address private _minter;

    /// @notice public metadata locked flag
    bool public locked;

    /// @notice Mapping draws id => details of the draw
    mapping(uint => DrawData) public draws;

    /// @notice Mapping token id => royalty details
    mapping(uint => RoyaltyReceiver) public royalties;

    /// @notice Minting events definition
    event AdminMinted(address indexed to, uint indexed tokenId);
    event Minted(address indexed to, uint indexed tokenId);

    /// @notice Draw events definition
    event DrawInitiated(bytes32 requestId);
    event DrawFinished(address winner, uint winningEdition);

    /// @notice metadata not locked modifier
    modifier notLocked() {
        require(!locked, "DCBW721: Metadata URIs are locked");
        _;
    }

    /// @notice allows only closed lottery state
    modifier requireState(DrawState state) {
        require(_state == state, "DCBW721: Invalid state for this action");
        _;
    }

    /// @notice allows only address to perform action
    modifier requireAccount(address account) {
        require(
            _msgSender() == account,
            "DCBW721: Invalid account for this action"
        );
        _;
    }

    /// @notice owner or minter
    modifier ownerOrMinter() {
        require(
            _msgSender() == _minter || _msgSender() == owner(),
            "DCBW721: Invalid account for this action"
        );
        _;
    }

    /**
     * @notice constructor
     * @param name the name of the EIP721 Contract
     * @param symbol the token symbol
     * @param baseTokenURI EIP721-required Base URI
     * @param mbeneficiary the contract Splitter that will receive minting funds
     * @param rbeneficiary the royalties beneficiary
     * @param alarmContract the alarm contract address to trigger DrawNumber on interval (TO BE SET POST-DEPLOYMENT)
     * @param rngContract the RNG contract address to get randomness (TO BE SET POST-DEPLOYMENT)
     **/
    constructor(
        string memory name,
        string memory symbol,
        string memory baseTokenURI,
        address mbeneficiary,
        address rbeneficiary,
        address alarmContract,
        address rngContract
    ) ERC721(name, symbol) Ownable() {
        locked = false;

        _mintPrice = 1 ether;
        _reservesRate = 200;
        _maxTokenId = 1000000;

        _baseExtension = ".json";
        _baseTokenURI = baseTokenURI;

        _mintingBeneficiary = payable(mbeneficiary);
        _rngContract = rngContract;
        _alarmContract = alarmContract;
        _minter = _msgSender();

        _state = DrawState.Closed;

        royalties[0] = RoyaltyReceiver(rbeneficiary, 100);
    }

    /// @notice feed eth into the contract
    function feed(uint256 intoReserves, uint256 intoGrandPrize)
        external
        payable
        onlyOwner
    {
        require(
            msg.value > 0 && intoReserves.add(intoGrandPrize) == msg.value,
            "DCBW721: Balance-Value Mismatch"
        );
        _updateGrandPrizePool(_grandPrizePool.add(intoGrandPrize));
        _updateReserves(_reserves.add(intoReserves));
    }

    /// @notice receive fallback should revert
    receive() external payable {
        revert("DCBW721: Please use Mint or Admin calls");
    }

    /// @notice default fallback should revert
    fallback() external payable {
        revert("DCBW721: Please use Mint or Admin calls");
    }

    /// @notice returns the base URI for the contract
    function _baseURI() internal view virtual override returns (string memory) {
        return _baseTokenURI;
    }

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId)
        public
        view
        virtual
        override
        returns (string memory)
    {
        return
            string(abi.encodePacked(super.tokenURI(tokenId), _baseExtension));
    }

    /**
     * @notice updates the all 4 addresses invovled in the contract flow
     * @param mintingBeneficiary the contract Splitter that will receive minting funds
     * @param alarmContract the alarm contract address to trigger DrawNumber on interval
     * @param rngContract the RNG contract address to trigger drawnNumber and pick winner
     * @param minter minter address
     * @param _owner the new admin address
     **/
    function updateAddressesAndTransferOwnership(
        address mintingBeneficiary,
        address alarmContract,
        address rngContract,
        address minter,
        address _owner
    ) external onlyOwner {
        changeMintBeneficiary(mintingBeneficiary);
        changeMinter(minter);

        setAlarmAccount(alarmContract);
        setVRFAccount(rngContract);

        transferOwnership(_owner);
    }

    /**
     * @dev Called with the sale price to determine how much royalty is owed and to whom.
     * @param tokenId - the NFT asset queried for royalty information
     * @param salePrice - the sale price of the NFT asset specified by `tokenId`
     * @return receiver - address of who should be sent the royalty payment
     * @return royaltyAmount - the royalty payment amount for `salePrice`
     */
    function royaltyInfo(uint tokenId, uint salePrice)
        external
        view
        returns (address, uint) {
        /// @notice all tokens have same royalty receiver
        tokenId = 0; // silence unused var warning
        return (royalties[tokenId].account, royalties[tokenId].shares.mul(salePrice).div(1000));
    }

    /**
     * @notice a function for admins to mint cost-free
     * @param to the address to send the minted token to
     * @param _tokenId to token ID to be minted
     **/
    function adminMint(address to, uint256 _tokenId)
        external
        whenNotPaused
        ownerOrMinter
        requireState(DrawState.Closed)
    {
        require(to != address(0), "DCBW721: Address cannot be 0");

        validateTokenId(_tokenId);

        _safeMint(to, _tokenId);

        emit AdminMinted(to, _tokenId);
    }

    /**
     * @notice the public minting function -- requires 1 ether sent
     * @param to the address to send the minted token to
     * @param _tokenId to token ID to be minted
     **/
    function mint(address to, uint256 _tokenId)
        external
        payable
        whenNotPaused
        requireState(DrawState.Closed)
    {
        uint256 received = msg.value;

        require(to != address(0), "DCBW721: Address cannot be 0");
        require(
            received == _mintPrice,
            "DCBW721: Ether sent mismatch with mint price"
        );

        validateTokenId(_tokenId);

        _safeMint(to, _tokenId);

        _forwardFunds(received);
        _updateReserves(_reserves.add(received.mul(_reservesRate).div(1000)));

        emit Minted(to, _tokenId);
    }

    /// @notice a function called by Alarm on each _interval and requests VRF to get randomness
    function drawNumber()
        external
        whenNotPaused
        requireAccount(_alarmContract)
        requireState(DrawState.Closed)
        nonReentrant
        returns (bool)
    {
        require(_reserves > 0, "DCBW721: Not enough reserves for draw");
        require(totalSupply() >= 500, "DCBW721: Supply of 500 not reached yet");

        require(
            _reserves != 0 && address(this).balance.sub(_grandPrizePool) >= _reserves,
            "DCBW721: Not enough balance for draw prize"
        );

        bytes32 reqId = IRNG(_rngContract).request();

        _state = DrawState.Open;
        draws[_drawsToDate] = DrawData(
            _drawsToDate,
            uint32(block.timestamp), /* solium-disable-line */
            0,
            0,
            address(0),
            0,
            _state,
            reqId
        );

        emit DrawInitiated(reqId);

        return true;
    }

    /// @notice a function called by Owner to request GrandPrize random number
    function drawNumberGrandPrize()
        external
        payable
        whenNotPaused
        onlyOwner
        requireState(DrawState.Closed)
        nonReentrant
        returns (bool)
    {
        if(msg.value > 0){
            _updateGrandPrizePool(_grandPrizePool.add(msg.value));
        }

        require(
            _grandPrizePool != 0 && address(this).balance.sub(_reserves) >= _grandPrizePool,
            "DCBW721: Not enough balance for grand prize"
        );

        bytes32 reqId = IRNG(_rngContract).request();

        _state = DrawState.Open;
        draws[_drawsToDate] = DrawData(
            _drawsToDate,
            uint32(block.timestamp), /* solium-disable-line */
            0,
            1,
            address(0),
            0,
            _state,
            reqId
        );

        emit DrawInitiated(reqId);

        return true;
    }

    /**
     * @notice a function called by DCBW721RNG fulfillRandomness Callback function to pick winner if it exists
     * @param _requestId The Id initially returned by DCBW721RNG requestRandomness
     * @param _randomness Random number generated by Chainlink VRF
     **/
    function numberDrawn(bytes32 _requestId, uint256 _randomness)
        external
        whenNotPaused
        requireAccount(_rngContract)
        nonReentrant
    {
        DrawData storage current = draws[_drawsToDate];
        require(
            current.randomNumberRequestId == _requestId,
            "DCBW721: Request ID mismatch"
        );

        current.winningEdition = uint64(uint256(_randomness % _maxTokenId).add(1));

        if (_exists(current.winningEdition)) {
            current.winner = ownerOf(current.winningEdition);
            current.prizePoolWon = current.isGrandPrize == uint96(1)
                ? uint96(_grandPrizePool)
                : uint96(_reserves);
            _payout(current);
        }

        emit DrawFinished(current.winner, current.winningEdition);

        /// @notice update state
        _drawsToDate++;
        _state = DrawState.Closed;

        /// @notice update draw record
        current.state = _state;
    }

    /**
     * @notice prize payout function
     * @param current DrawData object having a draw data
     **/
    function _payout(DrawData memory current) private {
        require(current.winner != address(0), "DCBW721: Address cannot be 0");
        require(current.prizePoolWon > 0, "DCBW721: Prize pool is empty");

        /// @notice updating reserve pool & grand prize pool
        if (current.isGrandPrize == 1) {
            _updateGrandPrizePool(0);
        } else {
            _updateReserves(0);
        }

        /// @notice forward prize to winner wallet using CALL to avoid 2300 stipend limit
        (bool success, ) = payable(current.winner).call{value: current.prizePoolWon}("");
        require(success, "DCBW721: Failed to forward prize");
    }

    /// @notice pausing the contract minting and token transfer
    function pause() public virtual onlyOwner {
        _pause();
    }

    /// @notice unpausing the contract minting and token transfer
    function unpause() public virtual onlyOwner {
        _unpause();
    }

    /**
     * @notice sets the state of the draw to closed
     * @dev for if the numberDrawn reverted
     */
    function resetDrawState() public onlyOwner {
        _state = DrawState.Closed;
    }

    /**
     * @notice changes the minter address
     * @param minter the new minter address
     **/
    function changeMinter(address minter) public onlyOwner {
        require(
            minter != address(0),
            "DCBW721: Minter cannot be address 0"
        );
        require(
            minter != _minter,
            "DCBW721: Minter cannot be same as previous"
        );
        _minter = minter;
    }

    /**
     * @notice changes the minting beneficiary payable address
     * @param beneficiary the contract Splitter that will receive minting funds
     **/
    function changeMintBeneficiary(address beneficiary) public onlyOwner {
        require(
            beneficiary != address(0),
            "DCBW721: Minting beneficiary cannot be address 0"
        );
        require(
            beneficiary != _mintingBeneficiary,
            "DCBW721: beneficiary cannot be same as previous"
        );
        _mintingBeneficiary = payable(beneficiary);
    }

    /**
     * @notice changes the royalties beneficiary EIP2981
     * @param beneficiary the address that will receive royalties
     * @param shares the shares as royalties
     **/
    function changeRoyaltiesBeneficiary(address beneficiary, uint32 shares) public onlyOwner {
        require(
            beneficiary != address(0),
            "DCBW721: Royalties beneficiary cannot be address 0"
        );
        require(shares > 0, 'DCBW721: Royalty shares cannot be 0');

        RoyaltyReceiver storage rr = royalties[0];
        rr.account = beneficiary;
        rr.shares = shares;
    }

    /**
     * @notice changes the minting cost
     * @param mintCost new minting cost
     **/
    function changeMintCost(uint256 mintCost) public onlyOwner {
        require(
            mintCost != _mintPrice,
            "DCBW721: mint Cost cannot be same as previous"
        );
        _mintPrice = mintCost;
    }

    /**
     * @notice changes the minting cost
     * @param newBaseURI the new Base URI
     **/
    function changeBaseURI(string memory newBaseURI)
        public
        onlyOwner
        notLocked
    {
        require((keccak256(abi.encodePacked((_baseTokenURI))) != keccak256(abi.encodePacked((newBaseURI)))), "DCBW721: Base URI cannot be same as previous");
        _baseTokenURI = newBaseURI;
    }

    /**
     * @notice changes the reserve rate
     * @param reservesRate new reserve rate
     **/
    function changeReserveRate(uint256 reservesRate) public onlyOwner {
        require(
            _reservesRate != reservesRate,
            "DCBW721: reservesRate cannot be same as previous"
        );
        _reservesRate = reservesRate;
    }

    /**
     * @notice grants alarm role to supplied address
     * @param account the address to receive the ALARM role
     */
    function setAlarmAccount(address account) public virtual onlyOwner {
        require(account != address(0), "DCBW721: Alarm cannot be address 0");
        require(
            account != _alarmContract,
            "DCBW721: Alarm Contract cannot be same as previous"
        );
        _alarmContract = account;
    }

    /**
     * @notice grants vrf role to supplied address
     * @param account the address to receive the VRF role
     */
    function setVRFAccount(address account) public virtual onlyOwner {
        require(account != address(0), "DCBW721: VRF/RNG cannot be address 0");
        require(
            account != _rngContract,
            "DCBW721: RNG cannot be same as previous"
        );
        _rngContract = account;
    }

    /// @notice lock metadata forever
    function lockMetadata() public onlyOwner notLocked {
        locked = true;
    }

    /**
     * @notice the public function for checking if a token ID has been minted
     * @param _tokenId to token ID to be checked
     **/
    function isTokenMinted(uint256 _tokenId) public view returns (bool) {
        return validateTokenId(_tokenId) && _exists(_tokenId);
    }

    /**
     * @notice the public function for validation of specific token ID
     * @param _tokenId to token ID to be validated
     **/
    function validateTokenId(uint256 _tokenId) public view returns (bool) {
        require(_tokenId >= 1, "DCBW721: Invalid token ID");
        require(_tokenId <= _maxTokenId, "DCBW721: Invalid token ID");
        return true;
    }

    /**
     * @notice updates the store reserves tracker
     * @param reserves current reserves after new minting
     **/
    function _updateReserves(uint256 reserves) internal {
        require(
            reserves <= address(this).balance.sub(_grandPrizePool),
            "DCBW721: Reserve-Balance Mismatch"
        );
        _reserves = reserves;
    }

    /**
     * @notice updates the store grandPrizePool tracker
     * @param grandPrize current grandPrize pool after receiving royalties
     **/
    function _updateGrandPrizePool(uint256 grandPrize) internal {
        require(
            grandPrize <= address(this).balance.sub(_reserves),
            "DCBW721: GrandPrize-Balance Mismatch"
        );
        _grandPrizePool = grandPrize;
    }

    /**
     * @notice Determines how ETH is stored/forwarded on purchases.
     * @param received amount to forward
     **/
    function _forwardFunds(uint256 received) internal {
        /// @notice forward fund to receiver wallet using CALL to avoid 2300 stipend limit
        (bool success, ) = _mintingBeneficiary.call{value: received.mul(uint256(1000).sub(_reservesRate)).div(1000)}("");
        require(success, "DCBW721: Failed to forward funds");
    }

    /**
     * @notice before transfer hook function
     * @param from the address to send the token from
     * @param to the address to send the token to
     * @param tokenId to token ID to be sent
     **/
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual override(ERC721, ERC721Enumerable, ERC721Pausable) {
        super._beforeTokenTransfer(from, to, tokenId);
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId)
        public
        view
        virtual
        override(IERC165, ERC721, ERC721Enumerable)
        returns (bool)
    {
        return super.supportsInterface(interfaceId);
    }
}

{
  "compilationTarget": {
    "DCBW721.sol": "DCBW721"
  },
  "evmVersion": "london",
  "libraries": {},
  "metadata": {
    "bytecodeHash": "ipfs"
  },
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}