Contract Source Code:

// SPDX-License-Identifier: MIT

//  https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/introspection/IERC165.sol
pragma solidity ^0.8.0;

interface IERC165 {
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/IERC721.sol
pragma solidity ^0.8.0;

interface IERC721 is IERC165 {
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    function balanceOf(address owner) external view returns (uint256 balance);

    function ownerOf(uint256 tokenId) external view returns (address owner);

    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    function approve(address to, uint256 tokenId) external;

    function getApproved(uint256 tokenId) external view returns (address operator);

    function setApprovalForAll(address operator, bool _approved) external;

    function isApprovedForAll(address owner, address operator) external view returns (bool);

    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;
}


// File: @openzeppelin/contracts/utils/introspection/ERC165.sol
pragma solidity ^0.8.0;

abstract contract ERC165 is IERC165 {
 
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}


pragma solidity ^0.8.0;
// conerts to ASCII
library Strings {
    bytes16 private constant _HEX_SYMBOLS = "0123456789abcdef";


    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);
    }

  
    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);
    }

   
    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);
    }
}

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Address.sol

pragma solidity ^0.8.0;
//address functions
library Address {
  
    function isContract(address account) internal view returns (bool) {

        uint256 size;
        assembly {
            size := extcodesize(account)
        }
        return size > 0;
    }

 
    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");
    }


    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionCall(target, data, "Address: low-level call failed");
    }

  
    function functionCall(
        address target,
        bytes memory data,
        string memory errorMessage
    ) internal returns (bytes memory) {
        return functionCallWithValue(target, data, 0, errorMessage);
    }

  
    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");
    }

   
    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);
    }

   
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

   
    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);
    }

  
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }


    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);
    }

  
    function verifyCallResult(
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal pure returns (bytes memory) {
        if (success) {
            return returndata;
        } else {
            
            if (returndata.length > 0) {
                

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

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/extensions/IERC721Metadata.sol

pragma solidity ^0.8.0;


//ERC-721 Token Standard
 
interface IERC721Metadata is IERC721 {
   
    function name() external view returns (string memory);

   
    function symbol() external view returns (string memory);

  
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/IERC721Receiver.sol

pragma solidity ^0.8.0;



interface IERC721Receiver {

    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Context.sol
pragma solidity ^0.8.0;

abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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


// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/ERC721.sol
pragma solidity ^0.8.0;

contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
    using Address for address;
    using Strings for uint256;

    string private _name;

    string private _symbol;

    mapping(uint256 => address) private _owners;

    mapping(address => uint256) private _balances;

    mapping(uint256 => address) private _tokenApprovals;

    mapping(address => mapping(address => bool)) private _operatorApprovals;
//coolection constructor
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

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


    function balanceOf(address owner) public view virtual override returns (uint256) {
        require(owner != address(0), "ERC721: balance query for the zero address");
        return _balances[owner];
    }


    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;
    }

   
    function name() public view virtual override returns (string memory) {
        return _name;
    }

 
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

  
    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())) : "";
    }

 
    function _baseURI() internal view virtual returns (string memory) {
        return "";
    }

    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);
    }

   
    function getApproved(uint256 tokenId) public view virtual override returns (address) {
        require(_exists(tokenId), "ERC721: approved query for nonexistent token");

        return _tokenApprovals[tokenId];
    }

   
    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);
    }

  
    function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
        return _operatorApprovals[owner][operator];
    }

    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: transfer caller is not owner nor approved");

        _transfer(from, to, tokenId);
    }
 
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        safeTransferFrom(from, to, tokenId, "");
    }
  
    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);
    }

    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");
    }


    function _exists(uint256 tokenId) internal view virtual returns (bool) {
        return _owners[tokenId] != address(0);
    }
  
    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));
    }
   
    function _safeMint(address to, uint256 tokenId) internal virtual {
        _safeMint(to, tokenId, "");
    }

  
    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"
        );
    }

 
    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);
    }

   
    function _burn(uint256 tokenId) internal virtual {
        address owner = ERC721.ownerOf(tokenId);

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

        _approve(address(0), tokenId);

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

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

    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);

        _approve(address(0), tokenId);

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

        emit Transfer(from, to, tokenId);
    }

  
    function _approve(address to, uint256 tokenId) internal virtual {
        _tokenApprovals[tokenId] = to;
        emit Approval(ERC721.ownerOf(tokenId), to, tokenId);
    }

    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;
        }
    }

    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    ) internal virtual {}
}


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;
    }
}


// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol

pragma solidity ^0.8.0;
// owner only commands
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

 //owner constructor
    constructor() {
        _setOwner(_msgSender());
    }

  
    function owner() public view virtual returns (address) {
        return _owner;
    }

   
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }


    function renounceOwnership() public virtual onlyOwner {
        _setOwner(address(0));
    }

 
    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);
    }
}

// OpenZeppelin Contracts (last updated v4.7.0) (utils/cryptography/MerkleProof.sol)

pragma solidity ^0.8.0;

/**
 * @dev These functions deal with verification of Merkle Tree proofs.
 *
 * The proofs can be generated using the JavaScript library
 * https://github.com/miguelmota/merkletreejs[merkletreejs].
 * Note: the hashing algorithm should be keccak256 and pair sorting should be enabled.
 *
 * See `test/utils/cryptography/MerkleProof.test.js` for some examples.
 *
 * WARNING: You should avoid using leaf values that are 64 bytes long prior to
 * hashing, or use a hash function other than keccak256 for hashing leaves.
 * This is because the concatenation of a sorted pair of internal nodes in
 * the merkle tree could be reinterpreted as a leaf value.
 */
library MerkleProof {
    /**
     * @dev Returns true if a `leaf` can be proved to be a part of a Merkle tree
     * defined by `root`. For this, a `proof` must be provided, containing
     * sibling hashes on the branch from the leaf to the root of the tree. Each
     * pair of leaves and each pair of pre-images are assumed to be sorted.
     */
    function verify(
        bytes32[] memory proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProof(proof, leaf) == root;
    }

    /**
     * @dev Calldata version of {verify}
     *
     * _Available since v4.7._
     */
    function verifyCalldata(
        bytes32[] calldata proof,
        bytes32 root,
        bytes32 leaf
    ) internal pure returns (bool) {
        return processProofCalldata(proof, leaf) == root;
    }

    /**
     * @dev Returns the rebuilt hash obtained by traversing a Merkle tree up
     * from `leaf` using `proof`. A `proof` is valid if and only if the rebuilt
     * hash matches the root of the tree. When processing the proof, the pairs
     * of leafs & pre-images are assumed to be sorted.
     *
     * _Available since v4.4._
     */
    function processProof(bytes32[] memory proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = _hashPair(computedHash, proof[i]);
        }
        return computedHash;
    }

    /**
     * @dev Calldata version of {processProof}
     *
     * _Available since v4.7._
     */
    function processProofCalldata(bytes32[] calldata proof, bytes32 leaf) internal pure returns (bytes32) {
        bytes32 computedHash = leaf;
        for (uint256 i = 0; i < proof.length; i++) {
            computedHash = _hashPair(computedHash, proof[i]);
        }
        return computedHash;
    }

    /**
     * @dev Returns true if the `leaves` can be simultaneously proven to be a part of a merkle tree defined by
     * `root`, according to `proof` and `proofFlags` as described in {processMultiProof}.
     *
     * CAUTION: Not all merkle trees admit multiproofs. See {processMultiProof} for details.
     *
     * _Available since v4.7._
     */
    function multiProofVerify(
        bytes32[] memory proof,
        bool[] memory proofFlags,
        bytes32 root,
        bytes32[] memory leaves
    ) internal pure returns (bool) {
        return processMultiProof(proof, proofFlags, leaves) == root;
    }

    /**
     * @dev Calldata version of {multiProofVerify}
     *
     * CAUTION: Not all merkle trees admit multiproofs. See {processMultiProof} for details.
     *
     * _Available since v4.7._
     */
    function multiProofVerifyCalldata(
        bytes32[] calldata proof,
        bool[] calldata proofFlags,
        bytes32 root,
        bytes32[] memory leaves
    ) internal pure returns (bool) {
        return processMultiProofCalldata(proof, proofFlags, leaves) == root;
    }

    /**
     * @dev Returns the root of a tree reconstructed from `leaves` and sibling nodes in `proof`. The reconstruction
     * proceeds by incrementally reconstructing all inner nodes by combining a leaf/inner node with either another
     * leaf/inner node or a proof sibling node, depending on whether each `proofFlags` item is true or false
     * respectively.
     *
     * CAUTION: Not all merkle trees admit multiproofs. To use multiproofs, it is sufficient to ensure that: 1) the tree
     * is complete (but not necessarily perfect), 2) the leaves to be proven are in the opposite order they are in the
     * tree (i.e., as seen from right to left starting at the deepest layer and continuing at the next layer).
     *
     * _Available since v4.7._
     */
    function processMultiProof(
        bytes32[] memory proof,
        bool[] memory proofFlags,
        bytes32[] memory leaves
    ) internal pure returns (bytes32 merkleRoot) {
        // This function rebuild the root hash by traversing the tree up from the leaves. The root is rebuilt by
        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
        // the merkle tree.
        uint256 leavesLen = leaves.length;
        uint256 totalHashes = proofFlags.length;

        // Check proof validity.
        require(leavesLen + proof.length - 1 == totalHashes, "MerkleProof: invalid multiproof");

        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
        bytes32[] memory hashes = new bytes32[](totalHashes);
        uint256 leafPos = 0;
        uint256 hashPos = 0;
        uint256 proofPos = 0;
        // At each step, we compute the next hash using two values:
        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
        //   get the next hash.
        // - depending on the flag, either another value for the "main queue" (merging branches) or an element from the
        //   `proof` array.
        for (uint256 i = 0; i < totalHashes; i++) {
            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
            bytes32 b = proofFlags[i] ? leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++] : proof[proofPos++];
            hashes[i] = _hashPair(a, b);
        }

        if (totalHashes > 0) {
            return hashes[totalHashes - 1];
        } else if (leavesLen > 0) {
            return leaves[0];
        } else {
            return proof[0];
        }
    }

    /**
     * @dev Calldata version of {processMultiProof}.
     *
     * CAUTION: Not all merkle trees admit multiproofs. See {processMultiProof} for details.
     *
     * _Available since v4.7._
     */
    function processMultiProofCalldata(
        bytes32[] calldata proof,
        bool[] calldata proofFlags,
        bytes32[] memory leaves
    ) internal pure returns (bytes32 merkleRoot) {
        // This function rebuild the root hash by traversing the tree up from the leaves. The root is rebuilt by
        // consuming and producing values on a queue. The queue starts with the `leaves` array, then goes onto the
        // `hashes` array. At the end of the process, the last hash in the `hashes` array should contain the root of
        // the merkle tree.
        uint256 leavesLen = leaves.length;
        uint256 totalHashes = proofFlags.length;

        // Check proof validity.
        require(leavesLen + proof.length - 1 == totalHashes, "MerkleProof: invalid multiproof");

        // The xxxPos values are "pointers" to the next value to consume in each array. All accesses are done using
        // `xxx[xxxPos++]`, which return the current value and increment the pointer, thus mimicking a queue's "pop".
        bytes32[] memory hashes = new bytes32[](totalHashes);
        uint256 leafPos = 0;
        uint256 hashPos = 0;
        uint256 proofPos = 0;
        // At each step, we compute the next hash using two values:
        // - a value from the "main queue". If not all leaves have been consumed, we get the next leaf, otherwise we
        //   get the next hash.
        // - depending on the flag, either another value for the "main queue" (merging branches) or an element from the
        //   `proof` array.
        for (uint256 i = 0; i < totalHashes; i++) {
            bytes32 a = leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++];
            bytes32 b = proofFlags[i] ? leafPos < leavesLen ? leaves[leafPos++] : hashes[hashPos++] : proof[proofPos++];
            hashes[i] = _hashPair(a, b);
        }

        if (totalHashes > 0) {
            return hashes[totalHashes - 1];
        } else if (leavesLen > 0) {
            return leaves[0];
        } else {
            return proof[0];
        }
    }

    function _hashPair(bytes32 a, bytes32 b) private pure returns (bytes32) {
        return a < b ? _efficientHash(a, b) : _efficientHash(b, a);
    }

    function _efficientHash(bytes32 a, bytes32 b) private pure returns (bytes32 value) {
        /// @solidity memory-safe-assembly
        assembly {
            mstore(0x00, a)
            mstore(0x20, b)
            value := keccak256(0x00, 0x40)
        }
    }
}


/*  

                                                                                               
   @@@@@@   @@@@@@@    @@@@@@    @@@@@@   @@@  @@@  @@@ @@@         @@@@@@   @@@@@@@@  @@@  @@@  
  @@@@@@@   @@@@@@@@  @@@@@@@@  @@@@@@@@  @@@  @@@  @@@ @@@        @@@@@@@   @@@@@@@@  @@@@ @@@  
  !@@       @@!  @@@  @@!  @@@  @@!  @@@  @@!  !@@  @@! !@@        !@@            @@!  @@!@!@@@  
  !@!       !@!  @!@  !@!  @!@  !@!  @!@  !@!  @!!  !@! @!!        !@!           !@!   !@!!@!@!  
  !!@@!!    @!@@!@!   @!@  !@!  @!@  !@!  @!@@!@!    !@!@!         !!@@!!       @!!    @!@ !!@!  
   !!@!!!   !!@!!!    !@!  !!!  !@!  !!!  !!@!!!      @!!!          !!@!!!     !!!     !@!  !!!  
       !:!  !!:       !!:  !!!  !!:  !!!  !!: :!!     !!:               !:!   !!:      !!:  !!!  
      !:!   :!:       :!:  !:!  :!:  !:!  :!:  !:!    :!:              !:!   :!:       :!:  !:!  
  :::: ::    ::       ::::: ::  ::::: ::   ::  :::     ::          :::: ::    :: ::::   ::   ::  
  :: : :     :         : :  :    : :  :    :   :::     :           :: : :    : :: : :  ::    :   
                                                                                               
                                                                                               

	
                            Contract provided By B.A.S.S Studios 
                            (Blockchain and Software Solutions)
                                    f i r e b u g 5 0 9                     
*/
pragma solidity >=0.7.0 <0.9.0;

abstract contract IParent {
    
    function ownerOf(uint256 tokenId) external view virtual returns (address);
    function walletOfOwner(address _owner) external view virtual returns (uint256[] memory);
    function totalSupply() external view virtual returns (uint256);
    function balanceOf(address owner) external view virtual returns (uint256);

}

contract SpookySZN is ERC721, Ownable, ReentrancyGuard {
  using Strings for uint256;

  bytes32 public merkleRoot;
  mapping(address => uint256) public whitelistClaimed;
  //collection details
  string public _collectionName= "Spooky SZN";
  string public _collectionSymbol="SPKYSZN";

  //metadata details
  string baseURI="ipfs://CID/";
  string public baseExtension = ".json";

  //mint details
  uint256 public cost = 0 ether;
  uint256 public whiteListCost = 0 ether;
  uint256 public maxSupply = 6666;
  uint256 public maxMintAmountPerTx = 5;
  uint256 public whiteListMintAmount=3;
  string public notRevealedUri;

  //track mints
  uint256 public amountMinted;
  uint256 public WLClaimed;


  //manage states
  //public sale toggle
  bool public publicPaused = true;
  //white list toggle
  bool public whitelistMintEnabled = false;
  //reveal toggle
  bool public revealed = false;
  //Mint pass claim toggle
  bool public parentClaimActive=false;

    //MintPass interface management
    mapping(address=>uint256) public _parentsClaimedPerAddress;
    // tracking Used partent claims / used mint passes
    uint256 public parentClaims;
    //v2 address change this to nft adress needed to hold for claim
    address public v2Address =0x3b8e3C1a29C5cA73Dd47Dc57781d3E7551c0A2aB;


    //initialize v2 as the parent interface
    IParent public v2;

  constructor() ERC721(_collectionName, _collectionSymbol)
   {
    setNotRevealedURI("ipfs://QmdC8LcRr5Xxzqdx3YCgs5uCEQBCApaCFXGRK7tdTwAp9P/HiddenMetadata.json");
    //assign v2 a contract address to act as the (parent/mint pass)
    v2= IParent(v2Address);
  }

  function _baseURI() internal view virtual override returns (string memory) {
    return baseURI;
  }

  // public minting fuction + WL check
  function mint(uint256 _mintAmount) public payable {

    uint256 mintSupply = totalSupply();

//manage public mint
    require(!publicPaused, "Contract is paused");
    require(_mintAmount > 0, "mint amount cant be 0");
    require(_mintAmount <= maxMintAmountPerTx, "Cant mint over the max mint amount");
    require(mintSupply + _mintAmount <= maxSupply, "Mint amount is too high there may not be enough left to mint that many");

    if (msg.sender != owner()) {
      require(msg.value >= cost * _mintAmount);
    }

    for (uint256 i = 1; i <= _mintAmount; i++) {
      _safeMint(msg.sender, mintSupply + i);
    }
    amountMinted+=_mintAmount;
  }
  
function whitelistMint(uint256 _mintAmount, bytes32[] calldata _merkleProof) public payable{

      uint256 mintSupply = totalSupply();
//manage whitelist request

    require(whitelistMintEnabled, "whitelist not active");
    require((whitelistClaimed[msg.sender] +_mintAmount) <= whiteListMintAmount, "Address already claimed! or you have requested more than allowed");
    require(_mintAmount > 0, "mint amount cant be 0");
    require(mintSupply + _mintAmount <= maxSupply, "Purchase would exceed max supply");
    require(msg.value>= whiteListCost*_mintAmount,"Eth value sent is not correct");
    bytes32 leaf = keccak256(abi.encodePacked(msg.sender)); 
    require(MerkleProof.verify(_merkleProof, merkleRoot, leaf), "Invalid proof!");

    whitelistClaimed[msg.sender] += _mintAmount;
    amountMinted+=_mintAmount;
    WLClaimed+=_mintAmount;

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

}

  //claimable list mint funtion
//claim from parent (mint pass implementation)
function claimForParentNFT(uint256 numberOfTokens) external payable {

    uint256 balance= v2.balanceOf(msg.sender);
    uint256 currentSupplyGlobal = totalSupply();
    uint256 currentClaimed =_parentsClaimedPerAddress[msg.sender];
    require(parentClaimActive, "Claim is not active");
    require(numberOfTokens+currentClaimed <=balance, "Exceeded max available to purchase");
    require(currentSupplyGlobal + numberOfTokens <= maxSupply, "Purchase would exceed max supply");

    for (uint256 i = 1; i <= (numberOfTokens); i++) {
                _safeMint(msg.sender, currentSupplyGlobal + i);
    }
                    parentClaims+=numberOfTokens;
                    _parentsClaimedPerAddress[msg.sender]+=numberOfTokens;
                    amountMinted+=numberOfTokens;
 }

//return total supply minted
 function totalSupply() public view returns (uint256) {
    return amountMinted;
  }

//gas efficient function to find token ids owned by address
   function walletOfOwner(address _owner)
    public
    view
    returns (uint256[] memory)
  {
    uint256 ownerTokenCount = balanceOf(_owner);
    uint256[] memory ownedTokenIds = new uint256[](ownerTokenCount);
    uint256 currentTokenId = 1;
    uint256 ownedTokenIndex = 0;

    while (ownedTokenIndex < ownerTokenCount && currentTokenId <= maxSupply) {
      address currentTokenOwner = ownerOf(currentTokenId);

      if (currentTokenOwner == _owner) {
        ownedTokenIds[ownedTokenIndex] = currentTokenId;
        ownedTokenIndex++;
      }
      currentTokenId++;
    }
    return ownedTokenIds;
  }

  function tokenURI(uint256 tokenId)
    public
    view
    virtual
    override
    returns (string memory)
  {
    require(_exists(tokenId),"ERC721Metadata: URI query for nonexistent token");
    
    if(revealed == false) {
        return notRevealedUri;
    }
    string memory currentBaseURI = _baseURI();
    return bytes(currentBaseURI).length > 0
        ? string(abi.encodePacked(currentBaseURI, tokenId.toString(), baseExtension))
        : "";
  }

  //Access Functions
  //actions for the owner to interact with contract
  function setRevealed(bool _newBool) public onlyOwner() {
      revealed = _newBool;
  }
// update mint cost
  function setCost(uint256 _newCost) public onlyOwner() {
    cost = _newCost;
  }
  // update WL mint cost
  function setWhiteListCost(uint256 _newCost) public onlyOwner() {
    whiteListCost = _newCost;
  }
// max mint amount
  function setmaxMintAmount(uint256 _newmaxMintAmount) public onlyOwner() {
    maxMintAmountPerTx = _newmaxMintAmount;
  }
// max WL amount
  function setMaxWlAmount(uint256 _newMaxWlAmount) public onlyOwner() {
    whiteListMintAmount= _newMaxWlAmount;
  }
//revealed bool  
  function setNotRevealedURI(string memory _notRevealedURI) public onlyOwner {
    notRevealedUri = _notRevealedURI;
  }
//base URI extension
  function setBaseURI(string memory _newBaseURI) public onlyOwner {
    baseURI = _newBaseURI;
  }
//set extension (.json)
  function setBaseExtension(string memory _newBaseExtension) public onlyOwner {
    baseExtension = _newBaseExtension;
  }
//contract paused state
  function setPaused(bool _state) public onlyOwner {
    publicPaused = _state;
  }

 
  //set white list to true or false for active
    function setWhitelistMintEnabled(bool _whiteListActive) external onlyOwner {
        whitelistMintEnabled = _whiteListActive;
    }

//mint pass access functions
function setV2Contract(address _newV2Contract) external onlyOwner {
    v2Address = _newV2Contract;
    v2=IParent(v2Address);
  }


function setParentClaim(bool choice) public onlyOwner{
    parentClaimActive=choice;
}
//distrubute
  function distribute(address walletAddress, uint256 amount) public onlyOwner{
      uint256 mintSupply=totalSupply();
          require(mintSupply + amount <= maxSupply, "Mint amount is too high there may not be enough left to mint that many");
          for(uint256 i=1; i<= amount;i++){
       _safeMint(walletAddress, mintSupply + i);
          }
          amountMinted+=amount;
  }

 function setMerkleRoot(bytes32 _merkleRoot) public onlyOwner {
    merkleRoot = _merkleRoot;
  }

//backup witdraw to retrieve all funds to deployment account 
  function backupWithdraw() public payable onlyOwner nonReentrant{
 
    (bool success, ) = payable(msg.sender).call{value: address(this).balance}("");
    require(success);
  }
}