// SPDX-License-Identifier: GPL-3.0
// File: @openzeppelin/contracts/utils/Strings.sol

pragma solidity ^0.8.4;

/**
 * @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);
    }
}

// File: @openzeppelin/contracts/utils/Context.sol

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/Ownable.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);
    }
}

// File: @openzeppelin/contracts/utils/Address.sol


/**
 * @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);
            }
        }
    }
}

// File: @openzeppelin/contracts/token/ERC721/IERC721Receiver.sol


/**
 * @title ERC721 token receiver interface
 * @dev Interface for any contract that wants to support safeTransfers
 * from ERC721 asset contracts.
 */
interface IERC721Receiver {
    /**
     * @dev Whenever an {IERC721} `tokenId` token is transferred to this contract via {IERC721-safeTransferFrom}
     * by `operator` from `from`, this function is called.
     *
     * It must return its Solidity selector to confirm the token transfer.
     * If any other value is returned or the interface is not implemented by the recipient, the transfer will be reverted.
     *
     * The selector can be obtained in Solidity with `IERC721.onERC721Received.selector`.
     */
    function onERC721Received(
        address operator,
        address from,
        uint256 tokenId,
        bytes calldata data
    ) external returns (bytes4);
}

// File: @openzeppelin/contracts/utils/introspection/IERC165.sol


/**
 * @dev Interface of the ERC165 standard, as defined in the
 * https://eips.ethereum.org/EIPS/eip-165[EIP].
 *
 * Implementers can declare support of contract interfaces, which can then be
 * queried by others ({ERC165Checker}).
 *
 * For an implementation, see {ERC165}.
 */
interface IERC165 {
    /**
     * @dev Returns true if this contract implements the interface defined by
     * `interfaceId`. See the corresponding
     * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
     * to learn more about how these ids are created.
     *
     * This function call must use less than 30 000 gas.
     */
    function supportsInterface(bytes4 interfaceId) external view returns (bool);
}

// File: @openzeppelin/contracts/utils/introspection/ERC165.sol



/**
 * @dev Implementation of the {IERC165} interface.
 *
 * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
 * for the additional interface id that will be supported. For example:
 *
 * ```solidity
 * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
 *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
 * }
 * ```
 *
 * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
 */
abstract contract ERC165 is IERC165 {
    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
        return interfaceId == type(IERC165).interfaceId;
    }
}

// File: @openzeppelin/contracts/token/ERC721/IERC721.sol



/**
 * @dev Required interface of an ERC721 compliant contract.
 */
interface IERC721 is IERC165 {
    /**
     * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
     */
    event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
     */
    event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);

    /**
     * @dev Emitted when `owner` enables or disables (`approved`) `operator` to manage all of its assets.
     */
    event ApprovalForAll(address indexed owner, address indexed operator, bool approved);

    /**
     * @dev Returns the number of tokens in ``owner``'s account.
     */
    function balanceOf(address owner) external view returns (uint256 balance);

    /**
     * @dev Returns the owner of the `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function ownerOf(uint256 tokenId) external view returns (address owner);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`, checking first that contract recipients
     * are aware of the ERC721 protocol to prevent tokens from being forever locked.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be have been allowed to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Transfers `tokenId` token from `from` to `to`.
     *
     * WARNING: Usage of this method is discouraged, use {safeTransferFrom} whenever possible.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) external;

    /**
     * @dev Gives permission to `to` to transfer `tokenId` token to another account.
     * The approval is cleared when the token is transferred.
     *
     * Only a single account can be approved at a time, so approving the zero address clears previous approvals.
     *
     * Requirements:
     *
     * - The caller must own the token or be an approved operator.
     * - `tokenId` must exist.
     *
     * Emits an {Approval} event.
     */
    function approve(address to, uint256 tokenId) external;

    /**
     * @dev Returns the account approved for `tokenId` token.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function getApproved(uint256 tokenId) external view returns (address operator);

    /**
     * @dev Approve or remove `operator` as an operator for the caller.
     * Operators can call {transferFrom} or {safeTransferFrom} for any token owned by the caller.
     *
     * Requirements:
     *
     * - The `operator` cannot be the caller.
     *
     * Emits an {ApprovalForAll} event.
     */
    function setApprovalForAll(address operator, bool _approved) external;

    /**
     * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
     *
     * See {setApprovalForAll}
     */
    function isApprovedForAll(address owner, address operator) external view returns (bool);

    /**
     * @dev Safely transfers `tokenId` token from `from` to `to`.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `tokenId` token must exist and be owned by `from`.
     * - If the caller is not `from`, it must be approved to move this token by either {approve} or {setApprovalForAll}.
     * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
     *
     * Emits a {Transfer} event.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 tokenId,
        bytes calldata data
    ) external;
}

// File: @openzeppelin/contracts/token/ERC721/extensions/IERC721Metadata.sol



/**
 * @title ERC-721 Non-Fungible Token Standard, optional metadata extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Metadata is IERC721 {
    /**
     * @dev Returns the token collection name.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the token collection symbol.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
     */
    function tokenURI(uint256 tokenId) external view returns (string memory);
}

// File: @openzeppelin/contracts/token/ERC721/ERC721.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 {}
}

// File: @openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol

/**
 * @dev ERC721 token with storage based token URI management.
 */
abstract contract ERC721URIStorage is ERC721 {
    using Strings for uint256;

    // Optional mapping for token URIs
    mapping(uint256 => string) private _tokenURIs;

    /**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721URIStorage: URI query for nonexistent token");

        string memory _tokenURI = _tokenURIs[tokenId];
        string memory base = _baseURI();

        // If there is no base URI, return the token URI.
        if (bytes(base).length == 0) {
            return _tokenURI;
        }
        // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
        if (bytes(_tokenURI).length > 0) {
            return string(abi.encodePacked(base, _tokenURI));
        }

        return super.tokenURI(tokenId);
    }

    /**
     * @dev Sets `_tokenURI` as the tokenURI of `tokenId`.
     *
     * Requirements:
     *
     * - `tokenId` must exist.
     */
    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
        require(_exists(tokenId), "ERC721URIStorage: URI set of nonexistent token");
        _tokenURIs[tokenId] = _tokenURI;
    }

    /**
     * @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 override {
        super._burn(tokenId);

        if (bytes(_tokenURIs[tokenId]).length != 0) {
            delete _tokenURIs[tokenId];
        }
    }
}

// File: @openzeppelin/contracts/utils/Counters.sol

/**
 * @title Counters
 * @author Matt Condon (@shrugs)
 * @dev Provides counters that can only be incremented, decremented or reset. This can be used e.g. to track the number
 * of elements in a mapping, issuing ERC721 ids, or counting request ids.
 *
 * Include with `using Counters for Counters.Counter;`
 */
library Counters {
    struct Counter {
        // This variable should never be directly accessed by users of the library: interactions must be restricted to
        // the library's function. As of Solidity v0.5.2, this cannot be enforced, though there is a proposal to add
        // this feature: see https://github.com/ethereum/solidity/issues/4637
        uint256 _value; // default: 0
    }

    function current(Counter storage counter) internal view returns (uint256) {
        return counter._value;
    }

    function increment(Counter storage counter) internal {
        unchecked {
        counter._value += 1;
    }
}

function decrement(Counter storage counter) internal {
uint256 value = counter._value;
require(value > 0, "Counter: decrement overflow");
unchecked {
counter._value = value - 1;
}
}

function reset(Counter storage counter) internal {
counter._value = 0;
}
}

// File: contracts/Homospacien.sol



// File: @openzeppelin/contracts/utils/math/SafeMath.sol

// 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;
}
}


function mod(
uint256 a,
uint256 b,
string memory errorMessage
) internal pure returns (uint256) {
unchecked {
require(b > 0, errorMessage);
return a % b;
}
}

function ceil(uint256 a, uint256 m) internal pure returns (uint256) {
uint256 c = add(a,m);
uint256 d = sub(c,1);
return mul(div(d,m),m);
}
}

contract Homospacien is  ERC721URIStorage, Ownable {
using Counters for Counters.Counter;
Counters.Counter private _tokenIds;
Counters.Counter private _earlyBirds; // early
Counters.Counter private _preSales;
Counters.Counter private _freeTokenIds;
Counters.Counter private _mainSales;
using SafeMath for uint256;
using Strings for uint256;
mapping(string => bool) _homospacienExists;
string public _baseHomospacienArtURL;
uint256 private _totalFreeTokenSupply;
uint256 private _totalEarlyBirdSupply;
uint256 private _totalPreSaleSupply;
uint256 private _totalMainSaleSupply;
uint commissionDenominator = 10000;
uint256 public basePercent = 100;

uint256 private _earlyBirdPrice = 450;
uint256 private _preSalePrice = 450;
uint256 private _mainSalePrice = 450;
uint256 private defaultRoyalityPercent = 1000;
bool private EarlyBirdOngoing;
bool private PreSaleOngoing;
bool private MainSaleOngoing;

bool private EarlyBirdUpgraded;
bool private PreSaleUpgraded;
uint32 private TOKEN_TYPE_FREE =1;
uint32 private TOKEN_TYPE_EARLY_BIRD =2;
uint32 private TOKEN_TYPE_PRE_SALE =3;
uint32 private TOKEN_TYPE_MAIN_SALE =4;
uint32 public maxiumum_Early_Bird_TPT;
uint32 public maximum_token_per_transactions;
uint32 private default_token_per_transactions=10;
mapping(address=>bool) freeTokenWhiteList;
mapping(address=>uint256) freeTokenRecivers;
mapping(address=>uint256) freeTokensOwned;
address[] internal whitelist;
address[] internal whitelistEarlyBird;
address[] internal whitelistPreSale;
address[] internal team;

// Data of each NFT
struct TokenData {
uint256 price;       // price of the token
//uint32 type;
}
mapping(uint256 => TokenData) tokens;
constructor() ERC721("Homospacien NFT", "Homospacien") {
    EarlyBirdOngoing= false;
    PreSaleOngoing = false;
    MainSaleOngoing =false;
    EarlyBirdUpgraded =false;
    PreSaleUpgraded = false;
    maxiumum_Early_Bird_TPT=1;
    maximum_token_per_transactions=default_token_per_transactions;
    _baseHomospacienArtURL= "https://ipfs.io/ipfs/QmSszmPiMeX6ZqvM4YNzy5GtfHQTGjaHJBef4ZHJNBnpNY/";
    _totalFreeTokenSupply = 500;
    _totalEarlyBirdSupply = 500;
    _totalPreSaleSupply   = 1000;
    _totalMainSaleSupply  = 8000;
}

event TotalSupplyChnaged(uint32 tokenType,  uint256 _prevSupply,  uint256 _newSupply, uint now);

function chnageTotalSupply(uint32 tokenType, uint256 _supply)
public
onlyOwner
{   uint256 _prevSupply =0;
    if (tokenType == TOKEN_TYPE_FREE){
    _prevSupply = _totalFreeTokenSupply;
    _totalFreeTokenSupply = _supply;
    } else if(tokenType == TOKEN_TYPE_EARLY_BIRD){
    _prevSupply = _totalEarlyBirdSupply;
    _totalEarlyBirdSupply = _supply;
    } else if(tokenType == TOKEN_TYPE_PRE_SALE){
    _prevSupply = _totalPreSaleSupply;
    _totalPreSaleSupply = _supply;
    } else if(tokenType == TOKEN_TYPE_MAIN_SALE){
    _prevSupply = _totalMainSaleSupply;
    _totalMainSaleSupply = _supply;
}
emit TotalSupplyChnaged( tokenType,   _prevSupply,   _supply, block.timestamp);
}



function change_baseURL( string memory _url) public
onlyOwner
returns (string memory) {
    _baseHomospacienArtURL = _url;
    return _baseHomospacienArtURL;
}

function change_TPT_EarlyBird( uint32 tpt) public
onlyOwner
returns (uint32) {
    maxiumum_Early_Bird_TPT = tpt;
    return maxiumum_Early_Bird_TPT;
}


function change_TPT( uint32 tpt) public
onlyOwner
returns (uint32) {
    maximum_token_per_transactions = tpt;
    return maximum_token_per_transactions;
}

event SaleStarted(uint32 tokenType,  uint now);

function setupEarlyBird( bool isOpen) public
onlyOwner
returns (bool) {
    EarlyBirdOngoing = isOpen;
    if(isOpen){
    setupPreSale(false);
    setupMainSale(false);
    emit SaleStarted( TOKEN_TYPE_EARLY_BIRD,  block.timestamp);
    }
    return EarlyBirdOngoing;
}

function setupPreSale( bool isOpen) public
onlyOwner
returns (bool) {
    PreSaleOngoing = isOpen;
    if(isOpen){
    setupEarlyBird(false);
    setupMainSale(false);
    emit SaleStarted( TOKEN_TYPE_PRE_SALE,  block.timestamp);
    }
    return PreSaleOngoing;
}


function setupMainSale( bool isOpen) public
onlyOwner
returns (bool) {
    MainSaleOngoing = isOpen;
    if(isOpen){
    setupEarlyBird(false);
    setupPreSale(false);
    emit SaleStarted( TOKEN_TYPE_MAIN_SALE,  block.timestamp);
    }
    return MainSaleOngoing;
}


function upgradeEarlyBird()public
onlyOwner
returns (bool) {

    EarlyBirdUpgraded = true;
    _totalPreSaleSupply = _totalPreSaleSupply.add(_totalEarlyBirdSupply.sub(_earlyBirds.current()));
    setupEarlyBird(false);
    setupPreSale(true);
    return EarlyBirdUpgraded;
}


function upgradePreSale()public
onlyOwner
returns (bool) {
    PreSaleUpgraded = true;
    _totalMainSaleSupply = _totalMainSaleSupply.add(_totalPreSaleSupply.sub(_preSales.current()));
    setupPreSale(false);
    return PreSaleUpgraded;
}

function payPrice(address sender, uint256 _price)
internal
{
    //_price = (_price.mul(1e18).div(commissionDenominator) ); // convert to wei
    require( address(sender).balance>_price, "Insufficient Balance.");
    address payable _platform= payable(owner());
    _platform.transfer(_price);
}
event HomoSpacienCreated(uint32 tokenType,  uint256 num,  uint now);
function mintEarlyBird(uint256 num) public
payable
returns(uint256)
{
    require(EarlyBirdOngoing, "Currently Early Bird session is not enabled.");
    require(num<=maxiumum_Early_Bird_TPT, "Only fixed number of tokens can be minted per transactions.");
    uint256 supply = _earlyBirds.current();
    require( supply + num < _totalEarlyBirdSupply, "Exceeds maximum supply for early bird" );
    (bool _isListed, ) = isWhiteListed(msg.sender, TOKEN_TYPE_EARLY_BIRD);
    require(_isListed, "Only whiteListed User can mint early bird token.");
    uint256 price = msg.value;
    uint256 tokenPrice = (_earlyBirdPrice.mul(1e18).div(commissionDenominator) ); 
    require(price == tokenPrice, "Price is more." );
    for(uint256 i; i < num; i++){
        mintToken(  _earlyBirdPrice );
        payPrice( msg.sender,  price);
        _earlyBirds.increment();
    }
    emit HomoSpacienCreated(TOKEN_TYPE_EARLY_BIRD,   num,  block.timestamp);
    return _earlyBirds.current();
}


function mintFreeTokens(uint256 num) public
onlyOwner
returns(uint256)
{

    uint256 supply = _freeTokenIds.current();
    require( supply + num < _totalFreeTokenSupply, "Exceeds maximum supply for free tokens." );
    
    for(uint256 i; i < num; i++){
        mintToken(  0.0 );
        _freeTokenIds.increment();
    }
    emit HomoSpacienCreated(TOKEN_TYPE_FREE,   num,  block.timestamp);
    return _freeTokenIds.current();
}

function transferFromOwner(address to, uint256  _tokenId) public{
    require(super._isApprovedOrOwner(super._msgSender(), _tokenId), "ERC721: transfer caller is not owner nor approved");
    transferFrom(super._msgSender(),  to, _tokenId);

}


function mintPreSaleTokens(uint256 num) public
payable
returns(uint256)
{
    require(PreSaleOngoing, "Currently Pre-Sale session is not enabled.");
    require(num<=maxiumum_Early_Bird_TPT, "Only fixed number of tokens can be minted per transactions.");
    uint256 supply = _preSales.current();
    require( supply + num < _totalPreSaleSupply, "Exceeds maximum supply for free tokens." );
    (bool _isListed, ) = isWhiteListed(msg.sender, TOKEN_TYPE_PRE_SALE);
    require(_isListed, "Only whiteListed User can mint pre-sale token.");
    uint256 price = msg.value;
    uint256 tokenPrice = (_preSalePrice.mul(1e18).div(commissionDenominator) ); 
    require(price == tokenPrice, "Insufficient Balance." );

    for(uint256 i; i < num; i++){
        mintToken( _preSalePrice );
        payPrice( msg.sender,  price);
        _preSales.increment();
    }
    emit HomoSpacienCreated(TOKEN_TYPE_PRE_SALE,   num,  block.timestamp);
    return _preSales.current();
}



function mintMainSaleTokens(uint256 num) public
payable
returns(uint256){

    require(MainSaleOngoing, "Currently Main Sale session is not enabled.");
    require(num<=maximum_token_per_transactions, "Only 10 tokens can be minted per transactions.");
    uint256 supply = _mainSales.current();

    require( supply + num < _totalMainSaleSupply, "Exceeds maximum supply for free tokens." );

    uint256 price = msg.value;
    uint256 tokenPrice = (_mainSalePrice.mul(1e18).div(commissionDenominator) ); 
    require(price == tokenPrice, "Insufficient Balance." );

    for(uint256 i; i < num; i++){
        mintToken(  _mainSalePrice );
        payPrice( msg.sender,  price);
        _mainSales.increment();
    }
    emit HomoSpacienCreated(TOKEN_TYPE_MAIN_SALE, num,  block.timestamp);
    return _mainSales.current();
}

function getBaseUrl() public view returns (string memory)
{
    return _baseHomospacienArtURL;
}

function getTokenUrl(uint256 tokenId) internal returns (string memory)
{
    string memory currentUrl = string(abi.encodePacked(_baseHomospacienArtURL, tokenId.toString()));
    return currentUrl;
}


// mints the NFT and save the data in the "tokens" map
function mintToken(uint256 _price) internal returns (uint256)
{

    _price = (_price.mul(1e18).div(commissionDenominator) ); // convert to wei
    _tokenIds.increment();
    uint256 newItemId = _tokenIds.current();
    string memory tokenURI = getTokenUrl(newItemId);
    require(_homospacienExists[tokenURI]  != true, "Token Already Exists");

    _safeMint(msg.sender, newItemId);
    _setTokenURI(newItemId, tokenURI);
    tokens[newItemId] = TokenData({price: _price});
    _homospacienExists[tokenURI] = true;

    return newItemId;
}


function mintFreeHomospacien(uint256 num)
public
{
    address minter = msg.sender;
    require(freeTokenWhiteList[minter], "Free token can be minted only by team member and whitelisted users.");   
    require(freeTokenRecivers[minter] > freeTokensOwned[minter], "The maximum number of token for this user is reached.");
    
    for(uint256 i; i < num; i++){
        mintToken(0.0);
    }
    freeTokensOwned[minter]= freeTokensOwned[minter].add(1);
    emit HomoSpacienCreated(TOKEN_TYPE_FREE,   1,  block.timestamp);
}
event PaymentToOwner( uint _amount, address from, address to, uint now);
event SentRoyalty(uint256 _tokenId, address customer, address platform, uint256 amount, uint now);

function BuyHomoSpacien( uint256  _tokenId)  payable external{
    address  customer = msg.sender;
    address payable _platform= payable(owner());
    uint256 productPriceinWei = tokens[_tokenId].price;
    uint256 price = msg.value;
    address payable  tokenOwner = payable(ownerOf(_tokenId));
    // send ether is same as price
    verifyTransaction(_tokenId, customer , tokenOwner,  _platform, price, productPriceinWei);
    _safeTransfer(tokenOwner, customer, _tokenId, "");

    //10% will go to platform

    uint256  platformCut = productPriceinWei.mul(defaultRoyalityPercent).div(commissionDenominator);
    platformCut = platformCut.ceil(basePercent);
    //market place commission
    _platform.transfer(platformCut);

    emit SentRoyalty(_tokenId, customer, _platform, platformCut, block.timestamp);

    uint256 ownerCut1 = productPriceinWei.sub(platformCut);
    ownerCut1 = ownerCut1.ceil(basePercent);
    tokenOwner.transfer(ownerCut1);
    emit PaymentToOwner(ownerCut1, tokenOwner, customer, block.timestamp);
}


function verifyTransaction(uint256  _tokenId, address customer, address tokenOwner, address _platform,
uint256 price, uint256 priceInWei)
view internal {
    require(_exists(_tokenId), "This is not a valid TokenId");
    require(tokenOwner != address(0) , "Invalid owner address.");
    require(customer != address(0) , "Invalid customer address as zero.");
    require(tokenOwner != customer && tokenOwner != _platform, "Invalid customer address.");
    require(price == priceInWei, "Invalid amount.");

    uint256 customerBalance = address(customer).balance;
    require(customerBalance >=priceInWei, 'Insufficient Balance. Balance should be more than or equal to price.');
}


function recievdHomoSpecien(uint256 _tokenId, address to)
payable
public
{
    address reciever = msg.sender;
    require(_exists(_tokenId), "This is not a valid TokenId");
    address _platform= payable(owner());
    require(msg.sender != _platform, "Invalid MarketPlace address.");
    require(to != _platform, "Invalid MarketPlace address.");
    require(to != address(0) && _platform != address(0) && to !=_platform, "Invalid address.");
    safeTransferFrom(_platform,to,_tokenId);
}

function changePrice(uint256 _tokenId, uint256 _newPrice) external {
    require(_exists(_tokenId), "This is not a valid TokenId");
    require(ownerOf(_tokenId) == msg.sender, "Only owner can change the price.");
    require(_newPrice != uint256(0));
    uint256 _oldPrice = tokens[_tokenId].price;
    _newPrice = (_newPrice.mul(1e18).div(commissionDenominator) ); // convert to wei

    require(_newPrice != _oldPrice, "New price can not be same as old price.");
    tokens[_tokenId].price = _newPrice;
}

function isWhiteListed(address _address, uint32 tokenType)
public
view
returns(bool, uint256)
{
    address _platform= payable(owner());
    require(tokenType == TOKEN_TYPE_FREE||tokenType == TOKEN_TYPE_EARLY_BIRD||tokenType == TOKEN_TYPE_PRE_SALE, "Invalid Token Type");
    require(_address != address(0) && _platform != _address, "Invalid address.");
    if (tokenType == TOKEN_TYPE_FREE){
    for (uint256 s = 0; s < whitelist.length; s += 1){
    if (_address == whitelist[s]) return (true, s);
    }
    return (false, 0);
    } else if(tokenType == TOKEN_TYPE_EARLY_BIRD){
    for (uint256 s = 0; s < whitelistEarlyBird.length; s += 1){
    if (_address == whitelistEarlyBird[s]) return (true, s);
    }
    return (false, 0);
    } else if(tokenType == TOKEN_TYPE_PRE_SALE){
    for (uint256 s = 0; s < whitelistPreSale.length; s += 1){
    if (_address == whitelistPreSale[s]) return (true, s);
    }
    return (false, 0);
    }

    return (false, 0);

}

/**
 * @notice A method to add a address to whitelist.
 * @param _address The address to add.
 */
function addToWhitelist(address _address, uint32 tokenType)
public
onlyOwner
{   bool _isWhitelisted = false;
    address _platform= payable(owner());
    require(tokenType == TOKEN_TYPE_FREE||tokenType == TOKEN_TYPE_EARLY_BIRD||tokenType == TOKEN_TYPE_PRE_SALE, "Invalid Token Type");
    require(_address != address(0) && _platform != _address, "Invalid address.");
    if (tokenType == TOKEN_TYPE_FREE){
    (_isWhitelisted, ) = isWhiteListed(_address, tokenType);
    if(!_isWhitelisted) whitelist.push(_address);
    } else if(tokenType == TOKEN_TYPE_EARLY_BIRD){
    (_isWhitelisted, ) = isWhiteListed(_address, tokenType);
    if(!_isWhitelisted) whitelistEarlyBird.push(_address);
    } else if(tokenType == TOKEN_TYPE_PRE_SALE){
    (_isWhitelisted, ) = isWhiteListed(_address, tokenType);
    if(!_isWhitelisted) whitelistPreSale.push(_address);
    }
}


function getTotalSupply()external view returns (uint256){
    return _tokenIds.current();
}

function removefromWhiteList(address _address, uint32 tokenType)
public
onlyOwner
    {  
        address _platform= payable(owner());
        require(tokenType == TOKEN_TYPE_FREE||tokenType == TOKEN_TYPE_EARLY_BIRD||tokenType == TOKEN_TYPE_PRE_SALE, "Invalid Token Type");
        require(_address != address(0) && _platform != _address, "Invalid address.");
        if (tokenType == TOKEN_TYPE_FREE){
        (bool _isWhitelisted, uint256 s) = isWhiteListed(_address, tokenType);
            if(_isWhitelisted){
            whitelist[s] = whitelist[whitelist.length - 1];
            whitelist.pop();
            } 
        } else if(tokenType == TOKEN_TYPE_EARLY_BIRD){
        (bool _isWhitelisted1, uint256 s1) = isWhiteListed(_address, tokenType);
            if(_isWhitelisted1){
            whitelistEarlyBird[s1] = whitelistEarlyBird[whitelistEarlyBird.length - 1];
            whitelistEarlyBird.pop();
            } 
        } else if(tokenType == TOKEN_TYPE_PRE_SALE){
        (bool _isWhitelisted2, uint256 s2) = isWhiteListed(_address, tokenType);
            if(_isWhitelisted2){
            whitelistPreSale[s2] = whitelistPreSale[whitelistPreSale.length - 1];
            whitelistPreSale.pop();
            } 
     
        }

    }

    function addToFreeWhitelist(address _address, uint256 num ) public onlyOwner{
        require(freeTokenWhiteList[_address]==false, "Address is already added for free token ");
        freeTokenRecivers[_address]=num;
        freeTokenWhiteList[_address]=true;
    }
    
    function addAddressListToFreeWhitelist(address[] calldata _addressList, uint256[] calldata num, uint32 tokenType ) public onlyOwner{
        
        for (uint i=0; i<_addressList.length; i++){
            bool _isWhitelisted = false;
            if (tokenType == TOKEN_TYPE_FREE){
                (_isWhitelisted, ) = isWhiteListed(_addressList[i], tokenType);
                if(!_isWhitelisted) {
                    whitelist.push(_addressList[i]);
                    freeTokenRecivers[_addressList[i]]=num[i];
                    freeTokenWhiteList[_addressList[i]]=true;
                }

            } else if(tokenType == TOKEN_TYPE_EARLY_BIRD){
            (_isWhitelisted, ) = isWhiteListed(_addressList[i], tokenType);
            if(!_isWhitelisted) whitelistEarlyBird.push(_addressList[i]);
            } else if(tokenType == TOKEN_TYPE_PRE_SALE){
            (_isWhitelisted, ) = isWhiteListed(_addressList[i], tokenType);
            if(!_isWhitelisted) whitelistPreSale.push(_addressList[i]);
            }
        }
    }

    function removeFromFreeWhitelist(address _address) public onlyOwner{
        require(freeTokenWhiteList[_address], "Address is not added for free token.");
        freeTokenRecivers[_address]=0;
        freeTokenWhiteList[_address]=false;
    }

    function getFreeToken() public view returns(uint256){
         require(freeTokenWhiteList[msg.sender], "Address is not added for free token.");
         return freeTokensOwned[msg.sender];
    }

    function getFreeTokenSupply() public view returns(uint256){
         require(freeTokenWhiteList[msg.sender], "Address is not added for free token.");
         return freeTokenRecivers[msg.sender];
    }
    
    function removeListFromFreeWhitelist(address[] calldata _addresses) public onlyOwner{
        for (uint i=0; i<_addresses.length; i++){
            require(freeTokenWhiteList[_addresses[i]], "Address is not added for free token.");
            freeTokenRecivers[_addresses[i]]=0;
            freeTokenWhiteList[_addresses[i]]=false;
        }
        
    }
}