Contract Address Details

/**
 *Submitted for verification at Etherscan.io on 2022-02-20
*/

// SPDX-License-Identifier: UNLICENSED

pragma solidity 0.8.9;

/* This contract is a subsidiary of the Hedron contract. The Hedron      *
 *  contract can be found at 0x3819f64f282bf135d62168C1e513280dAF905e06. */

/* Hedron is a collection of Ethereum / PulseChain smart contracts that  *
 * build upon the HEX smart contract to provide additional functionality */

/**
 * @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);
}

/**
 * @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;
}

/**
 * @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);
}

/**
 * @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);
}

/**
 * @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);
            }
        }
    }
}

/**
 * @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;
    }
}

/**
 * @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);
    }
}

/**
 * @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;
    }
}

/**
 * @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 {
        _setApprovalForAll(_msgSender(), operator, approved);
    }

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

    /**
     * @dev See {IERC721-transferFrom}.
     */
    function transferFrom(
        address from,
        address to,
        uint256 tokenId
    ) public virtual override {
        //solhint-disable-next-line max-line-length
        require(_isApprovedOrOwner(_msgSender(), tokenId), "ERC721: 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 Approve `operator` to operate on all of `owner` tokens
     *
     * Emits a {ApprovalForAll} event.
     */
    function _setApprovalForAll(
        address owner,
        address operator,
        bool approved
    ) internal virtual {
        require(owner != operator, "ERC721: approve to caller");
        _operatorApprovals[owner][operator] = approved;
        emit ApprovalForAll(owner, operator, approved);
    }

    /**
     * @dev 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 {}
}

/**
 * @title ERC-721 Non-Fungible Token Standard, optional enumeration extension
 * @dev See https://eips.ethereum.org/EIPS/eip-721
 */
interface IERC721Enumerable is IERC721 {
    /**
     * @dev Returns the total amount of tokens stored by the contract.
     */
    function totalSupply() external view returns (uint256);

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

/**
 * @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;
    }
}

/**
 * @dev https://eips.ethereum.org/EIPS/eip-1167[EIP 1167] is a standard for
 * deploying minimal proxy contracts, also known as "clones".
 *
 * > To simply and cheaply clone contract functionality in an immutable way, this standard specifies
 * > a minimal bytecode implementation that delegates all calls to a known, fixed address.
 *
 * The library includes functions to deploy a proxy using either `create` (traditional deployment) or `create2`
 * (salted deterministic deployment). It also includes functions to predict the addresses of clones deployed using the
 * deterministic method.
 *
 * _Available since v3.4._
 */
library Clones {
    /**
     * @dev Deploys and returns the address of a clone that mimics the behaviour of `implementation`.
     *
     * This function uses the create opcode, which should never revert.
     */
    function clone(address implementation) internal returns (address instance) {
        assembly {
            let ptr := mload(0x40)
            mstore(ptr, 0x3d602d80600a3d3981f3363d3d373d3d3d363d73000000000000000000000000)
            mstore(add(ptr, 0x14), shl(0x60, implementation))
            mstore(add(ptr, 0x28), 0x5af43d82803e903d91602b57fd5bf30000000000000000000000000000000000)
            instance := create(0, ptr, 0x37)
        }
        require(instance != address(0), "ERC1167: create failed");
    }

    /**
     * @dev Deploys and returns the address of a clone that mimics the behaviour of `implementation`.
     *
     * This function uses the create2 opcode and a `salt` to deterministically deploy
     * the clone. Using the same `implementation` and `salt` multiple time will revert, since
     * the clones cannot be deployed twice at the same address.
     */
    function cloneDeterministic(address implementation, bytes32 salt) internal returns (address instance) {
        assembly {
            let ptr := mload(0x40)
            mstore(ptr, 0x3d602d80600a3d3981f3363d3d373d3d3d363d73000000000000000000000000)
            mstore(add(ptr, 0x14), shl(0x60, implementation))
            mstore(add(ptr, 0x28), 0x5af43d82803e903d91602b57fd5bf30000000000000000000000000000000000)
            instance := create2(0, ptr, 0x37, salt)
        }
        require(instance != address(0), "ERC1167: create2 failed");
    }

    /**
     * @dev Computes the address of a clone deployed using {Clones-cloneDeterministic}.
     */
    function predictDeterministicAddress(
        address implementation,
        bytes32 salt,
        address deployer
    ) internal pure returns (address predicted) {
        assembly {
            let ptr := mload(0x40)
            mstore(ptr, 0x3d602d80600a3d3981f3363d3d373d3d3d363d73000000000000000000000000)
            mstore(add(ptr, 0x14), shl(0x60, implementation))
            mstore(add(ptr, 0x28), 0x5af43d82803e903d91602b57fd5bf3ff00000000000000000000000000000000)
            mstore(add(ptr, 0x38), shl(0x60, deployer))
            mstore(add(ptr, 0x4c), salt)
            mstore(add(ptr, 0x6c), keccak256(ptr, 0x37))
            predicted := keccak256(add(ptr, 0x37), 0x55)
        }
    }

    /**
     * @dev Computes the address of a clone deployed using {Clones-cloneDeterministic}.
     */
    function predictDeterministicAddress(address implementation, bytes32 salt)
        internal
        view
        returns (address predicted)
    {
        return predictDeterministicAddress(implementation, salt, address(this));
    }
}

interface IHEX {
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    event Claim(
        uint256 data0,
        uint256 data1,
        bytes20 indexed btcAddr,
        address indexed claimToAddr,
        address indexed referrerAddr
    );
    event ClaimAssist(
        uint256 data0,
        uint256 data1,
        uint256 data2,
        address indexed senderAddr
    );
    event DailyDataUpdate(uint256 data0, address indexed updaterAddr);
    event ShareRateChange(uint256 data0, uint40 indexed stakeId);
    event StakeEnd(
        uint256 data0,
        uint256 data1,
        address indexed stakerAddr,
        uint40 indexed stakeId
    );
    event StakeGoodAccounting(
        uint256 data0,
        uint256 data1,
        address indexed stakerAddr,
        uint40 indexed stakeId,
        address indexed senderAddr
    );
    event StakeStart(
        uint256 data0,
        address indexed stakerAddr,
        uint40 indexed stakeId
    );
    event Transfer(address indexed from, address indexed to, uint256 value);
    event XfLobbyEnter(
        uint256 data0,
        address indexed memberAddr,
        uint256 indexed entryId,
        address indexed referrerAddr
    );
    event XfLobbyExit(
        uint256 data0,
        address indexed memberAddr,
        uint256 indexed entryId,
        address indexed referrerAddr
    );

    fallback() external payable;

    function allocatedSupply() external view returns (uint256);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function balanceOf(address account) external view returns (uint256);

    function btcAddressClaim(
        uint256 rawSatoshis,
        bytes32[] memory proof,
        address claimToAddr,
        bytes32 pubKeyX,
        bytes32 pubKeyY,
        uint8 claimFlags,
        uint8 v,
        bytes32 r,
        bytes32 s,
        uint256 autoStakeDays,
        address referrerAddr
    ) external returns (uint256);

    function btcAddressClaims(bytes20) external view returns (bool);

    function btcAddressIsClaimable(
        bytes20 btcAddr,
        uint256 rawSatoshis,
        bytes32[] memory proof
    ) external view returns (bool);

    function btcAddressIsValid(
        bytes20 btcAddr,
        uint256 rawSatoshis,
        bytes32[] memory proof
    ) external pure returns (bool);

    function claimMessageMatchesSignature(
        address claimToAddr,
        bytes32 claimParamHash,
        bytes32 pubKeyX,
        bytes32 pubKeyY,
        uint8 claimFlags,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external pure returns (bool);

    function currentDay() external view returns (uint256);

    function dailyData(uint256)
        external
        view
        returns (
            uint72 dayPayoutTotal,
            uint72 dayStakeSharesTotal,
            uint56 dayUnclaimedSatoshisTotal
        );

    function dailyDataRange(uint256 beginDay, uint256 endDay)
        external
        view
        returns (uint256[] memory list);

    function dailyDataUpdate(uint256 beforeDay) external;

    function decimals() external view returns (uint8);

    function decreaseAllowance(address spender, uint256 subtractedValue)
        external
        returns (bool);

    function globalInfo() external view returns (uint256[13] memory);

    function globals()
        external
        view
        returns (
            uint72 lockedHeartsTotal,
            uint72 nextStakeSharesTotal,
            uint40 shareRate,
            uint72 stakePenaltyTotal,
            uint16 dailyDataCount,
            uint72 stakeSharesTotal,
            uint40 latestStakeId,
            uint128 claimStats
        );

    function increaseAllowance(address spender, uint256 addedValue)
        external
        returns (bool);

    function merkleProofIsValid(bytes32 merkleLeaf, bytes32[] memory proof)
        external
        pure
        returns (bool);

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

    function pubKeyToBtcAddress(
        bytes32 pubKeyX,
        bytes32 pubKeyY,
        uint8 claimFlags
    ) external pure returns (bytes20);

    function pubKeyToEthAddress(bytes32 pubKeyX, bytes32 pubKeyY)
        external
        pure
        returns (address);

    function stakeCount(address stakerAddr) external view returns (uint256);

    function stakeEnd(uint256 stakeIndex, uint40 stakeIdParam) external;

    function stakeGoodAccounting(
        address stakerAddr,
        uint256 stakeIndex,
        uint40 stakeIdParam
    ) external;

    function stakeLists(address, uint256)
        external
        view
        returns (
            uint40 stakeId,
            uint72 stakedHearts,
            uint72 stakeShares,
            uint16 lockedDay,
            uint16 stakedDays,
            uint16 unlockedDay,
            bool isAutoStake
        );

    function stakeStart(uint256 newStakedHearts, uint256 newStakedDays)
        external;

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

    function totalSupply() external view returns (uint256);

    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    function xfLobby(uint256) external view returns (uint256);

    function xfLobbyEnter(address referrerAddr) external payable;

    function xfLobbyEntry(address memberAddr, uint256 entryId)
        external
        view
        returns (uint256 rawAmount, address referrerAddr);

    function xfLobbyExit(uint256 enterDay, uint256 count) external;

    function xfLobbyFlush() external;

    function xfLobbyMembers(uint256, address)
        external
        view
        returns (uint40 headIndex, uint40 tailIndex);

    function xfLobbyPendingDays(address memberAddr)
        external
        view
        returns (uint256[2] memory words);

    function xfLobbyRange(uint256 beginDay, uint256 endDay)
        external
        view
        returns (uint256[] memory list);
}

struct HEXDailyData {
    uint72 dayPayoutTotal;
    uint72 dayStakeSharesTotal;
    uint56 dayUnclaimedSatoshisTotal;
}

struct HEXGlobals {
    uint72 lockedHeartsTotal;
    uint72 nextStakeSharesTotal;
    uint40 shareRate;
    uint72 stakePenaltyTotal;
    uint16 dailyDataCount;
    uint72 stakeSharesTotal;
    uint40 latestStakeId;
    uint128 claimStats;
}

struct HEXStake {
    uint40 stakeId;
    uint72 stakedHearts;
    uint72 stakeShares;
    uint16 lockedDay;
    uint16 stakedDays;
    uint16 unlockedDay;
    bool   isAutoStake;
}

struct HEXStakeMinimal {
    uint40 stakeId;
    uint72 stakeShares;
    uint16 lockedDay;
    uint16 stakedDays;
}

struct ShareStore {
    HEXStakeMinimal stake;
    uint16          mintedDays;
    uint8           launchBonus;
    uint16          loanStart;
    uint16          loanedDays;
    uint32          interestRate;
    uint8           paymentsMade;
    bool            isLoaned;
}

struct ShareCache {
    HEXStakeMinimal _stake;
    uint256         _mintedDays;
    uint256         _launchBonus;
    uint256         _loanStart;
    uint256         _loanedDays;
    uint256         _interestRate;
    uint256         _paymentsMade;
    bool            _isLoaned;
}

address constant _hdrnSourceAddress = address(0x9d73Ced2e36C89E5d167151809eeE218a189f801);
address constant _hdrnFlowAddress   = address(0xF447BE386164dADfB5d1e7622613f289F17024D8);
uint256 constant _hdrnLaunch        = 1645833600;

contract HEXStakeInstance {
    
    IHEX       private _hx;
    address    private _creator;
    ShareStore public  share;

    /**
     * @dev Updates the HSI's internal HEX stake data.
     */
    function _stakeDataUpdate(
    )
        internal
    {
        uint40 stakeId;
        uint72 stakedHearts;
        uint72 stakeShares;
        uint16 lockedDay;
        uint16 stakedDays;
        uint16 unlockedDay;
        bool   isAutoStake;
        
        (stakeId,
         stakedHearts,
         stakeShares,
         lockedDay,
         stakedDays,
         unlockedDay,
         isAutoStake
        ) = _hx.stakeLists(address(this), 0);

        share.stake.stakeId = stakeId;
        share.stake.stakeShares = stakeShares;
        share.stake.lockedDay = lockedDay;
        share.stake.stakedDays = stakedDays;
    }

    function initialize(
        address hexAddress
    ) 
        external 
    {
        require(_creator == address(0),
            "HSI: Initialization already performed");

        /* _creator is not an admin key. It is set at contsruction to be a link
           to the parent contract. In this case HSIM */
        _creator = msg.sender;

        // set HEX contract address
        _hx = IHEX(payable(hexAddress));
    }

    /**
     * @dev Creates a new HEX stake using all HEX ERC20 tokens assigned
     *      to the HSI's contract address. This is a privileged operation only
     *      HEXStakeInstanceManager.sol can call.
     * @param stakeLength Number of days the HEX ERC20 tokens will be staked.
     */
    function create(
        uint256 stakeLength
    )
        external
    {
        uint256 hexBalance = _hx.balanceOf(address(this));

        require(msg.sender == _creator,
            "HSI: Caller must be contract creator");
        require(share.stake.stakedDays == 0,
            "HSI: Creation already performed");
        require(hexBalance > 0,
            "HSI: Creation requires a non-zero HEX balance");

        _hx.stakeStart(
            hexBalance,
            stakeLength
        );

        _stakeDataUpdate();
    }

    /**
     * @dev Calls the HEX function "stakeGoodAccounting" against the
     *      HEX stake held within the HSI.
     */
    function goodAccounting(
    )
        external
    {
        require(share.stake.stakedDays > 0,
            "HSI: Creation not yet performed");

        _hx.stakeGoodAccounting(address(this), 0, share.stake.stakeId);

        _stakeDataUpdate();
    }

    /**
     * @dev Ends the HEX stake, approves the "_creator" address to transfer
     *      all HEX ERC20 tokens, and self-destructs the HSI. This is a 
     *      privileged operation only HEXStakeInstanceManager.sol can call.
     */
    function destroy(
    )
        external
    {
        require(msg.sender == _creator,
            "HSI: Caller must be contract creator");
        require(share.stake.stakedDays > 0,
            "HSI: Creation not yet performed");

        _hx.stakeEnd(0, share.stake.stakeId);
        
        uint256 hexBalance = _hx.balanceOf(address(this));

        if (_hx.approve(_creator, hexBalance)) {
            selfdestruct(payable(_creator));
        }
        else {
            revert();
        }
    }

    /**
     * @dev Updates the HSI's internal share data. This is a privileged 
     *      operation only HEXStakeInstanceManager.sol can call.
     * @param _share "ShareCache" object containing updated share data.
     */
    function update(
        ShareCache memory _share
    )
        external 
    {
        require(msg.sender == _creator,
            "HSI: Caller must be contract creator");

        share.mintedDays   = uint16(_share._mintedDays);
        share.launchBonus  = uint8 (_share._launchBonus);
        share.loanStart    = uint16(_share._loanStart);
        share.loanedDays   = uint16(_share._loanedDays);
        share.interestRate = uint32(_share._interestRate);
        share.paymentsMade = uint8 (_share._paymentsMade);
        share.isLoaned     = _share._isLoaned;
    }

    /**
     * @dev Fetches stake data from the HEX contract.
     * @return A "HEXStake" object containg the HEX stake data. 
     */
    function stakeDataFetch(
    ) 
        external
        view
        returns(HEXStake memory)
    {
        uint40 stakeId;
        uint72 stakedHearts;
        uint72 stakeShares;
        uint16 lockedDay;
        uint16 stakedDays;
        uint16 unlockedDay;
        bool   isAutoStake;
        
        (stakeId,
         stakedHearts,
         stakeShares,
         lockedDay,
         stakedDays,
         unlockedDay,
         isAutoStake
        ) = _hx.stakeLists(address(this), 0);

        return HEXStake(
            stakeId,
            stakedHearts,
            stakeShares,
            lockedDay,
            stakedDays,
            unlockedDay,
            isAutoStake
        );
    }
}

interface IHedron {
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    event Claim(uint256 data, address indexed claimant, uint40 indexed stakeId);
    event LoanEnd(
        uint256 data,
        address indexed borrower,
        uint40 indexed stakeId
    );
    event LoanLiquidateBid(
        uint256 data,
        address indexed bidder,
        uint40 indexed stakeId,
        uint40 indexed liquidationId
    );
    event LoanLiquidateExit(
        uint256 data,
        address indexed liquidator,
        uint40 indexed stakeId,
        uint40 indexed liquidationId
    );
    event LoanLiquidateStart(
        uint256 data,
        address indexed borrower,
        uint40 indexed stakeId,
        uint40 indexed liquidationId
    );
    event LoanPayment(
        uint256 data,
        address indexed borrower,
        uint40 indexed stakeId
    );
    event LoanStart(
        uint256 data,
        address indexed borrower,
        uint40 indexed stakeId
    );
    event Mint(uint256 data, address indexed minter, uint40 indexed stakeId);
    event Transfer(address indexed from, address indexed to, uint256 value);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function balanceOf(address account) external view returns (uint256);

    function calcLoanPayment(
        address borrower,
        uint256 hsiIndex,
        address hsiAddress
    ) external view returns (uint256, uint256);

    function calcLoanPayoff(
        address borrower,
        uint256 hsiIndex,
        address hsiAddress
    ) external view returns (uint256, uint256);

    function claimInstanced(
        uint256 hsiIndex,
        address hsiAddress,
        address hsiStarterAddress
    ) external;

    function claimNative(uint256 stakeIndex, uint40 stakeId)
        external
        returns (uint256);

    function currentDay() external view returns (uint256);

    function dailyDataList(uint256)
        external
        view
        returns (
            uint72 dayMintedTotal,
            uint72 dayLoanedTotal,
            uint72 dayBurntTotal,
            uint32 dayInterestRate,
            uint8 dayMintMultiplier
        );

    function decimals() external view returns (uint8);

    function decreaseAllowance(address spender, uint256 subtractedValue)
        external
        returns (bool);

    function hsim() external view returns (address);

    function increaseAllowance(address spender, uint256 addedValue)
        external
        returns (bool);

    function liquidationList(uint256)
        external
        view
        returns (
            uint256 liquidationStart,
            address hsiAddress,
            uint96 bidAmount,
            address liquidator,
            uint88 endOffset,
            bool isActive
        );

    function loanInstanced(uint256 hsiIndex, address hsiAddress)
        external
        returns (uint256);

    function loanLiquidate(
        address owner,
        uint256 hsiIndex,
        address hsiAddress
    ) external returns (uint256);

    function loanLiquidateBid(uint256 liquidationId, uint256 liquidationBid)
        external
        returns (uint256);

    function loanLiquidateExit(uint256 hsiIndex, uint256 liquidationId)
        external
        returns (address);

    function loanPayment(uint256 hsiIndex, address hsiAddress)
        external
        returns (uint256);

    function loanPayoff(uint256 hsiIndex, address hsiAddress)
        external
        returns (uint256);

    function loanedSupply() external view returns (uint256);

    function mintInstanced(uint256 hsiIndex, address hsiAddress)
        external
        returns (uint256);

    function mintNative(uint256 stakeIndex, uint40 stakeId)
        external
        returns (uint256);

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

    function proofOfBenevolence(uint256 amount) external;

    function shareList(uint256)
        external
        view
        returns (
            HEXStakeMinimal memory stake,
            uint16 mintedDays,
            uint8 launchBonus,
            uint16 loanStart,
            uint16 loanedDays,
            uint32 interestRate,
            uint8 paymentsMade,
            bool isLoaned
        );

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

    function totalSupply() external view returns (uint256);

    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);
}

library LibPart {
    bytes32 public constant TYPE_HASH = keccak256("Part(address account,uint96 value)");

    struct Part {
        address payable account;
        uint96 value;
    }

    function hash(Part memory part) internal pure returns (bytes32) {
        return keccak256(abi.encode(TYPE_HASH, part.account, part.value));
    }
}

abstract contract AbstractRoyalties {
    mapping (uint256 => LibPart.Part[]) internal royalties;

    function _saveRoyalties(uint256 id, LibPart.Part[] memory _royalties) internal {
        uint256 totalValue;
        for (uint i = 0; i < _royalties.length; i++) {
            require(_royalties[i].account != address(0x0), "Recipient should be present");
            require(_royalties[i].value != 0, "Royalty value should be positive");
            totalValue += _royalties[i].value;
            royalties[id].push(_royalties[i]);
        }
        require(totalValue < 10000, "Royalty total value should be < 10000");
        _onRoyaltiesSet(id, _royalties);
    }

    function _updateAccount(uint256 _id, address _from, address _to) internal {
        uint length = royalties[_id].length;
        for(uint i = 0; i < length; i++) {
            if (royalties[_id][i].account == _from) {
                royalties[_id][i].account = payable(address(uint160(_to)));
            }
        }
    }

    function _onRoyaltiesSet(uint256 id, LibPart.Part[] memory _royalties) virtual internal;
}

interface RoyaltiesV2 {
    event RoyaltiesSet(uint256 tokenId, LibPart.Part[] royalties);

    function getRaribleV2Royalties(uint256 id) external view returns (LibPart.Part[] memory);
}

contract RoyaltiesV2Impl is AbstractRoyalties, RoyaltiesV2 {

    function getRaribleV2Royalties(uint256 id) override external view returns (LibPart.Part[] memory) {
        return royalties[id];
    }

    function _onRoyaltiesSet(uint256 id, LibPart.Part[] memory _royalties) override internal {
        emit RoyaltiesSet(id, _royalties);
    }
}

library LibRoyaltiesV2 {
    /*
     * bytes4(keccak256('getRaribleV2Royalties(uint256)')) == 0xcad96cca
     */
    bytes4 constant _INTERFACE_ID_ROYALTIES = 0xcad96cca;
}

contract HEXStakeInstanceManager is ERC721, ERC721Enumerable, RoyaltiesV2Impl {

    using Counters for Counters.Counter;

    bytes4 private constant _INTERFACE_ID_ERC2981 = 0x2a55205a;
    uint96 private constant _hsimRoyaltyBasis = 15; // Rarible V2 royalty basis
    string private constant _hostname = "https://api.hedron.pro/";
    string private constant _endpoint = "/hsi/";
    
    Counters.Counter private _tokenIds;
    address          private _creator;
    IHEX             private _hx;
    address          private _hxAddress;
    address          private _hsiImplementation;

    mapping(address => address[]) public  hsiLists;
    mapping(uint256 => address)   public  hsiToken;
 
    constructor(
        address hexAddress
    )
        ERC721("HEX Stake Instance", "HSI")
    {
        /* _creator is not an admin key. It is set at contsruction to be a link
           to the parent contract. In this case Hedron */
        _creator = msg.sender;

        // set HEX contract address
        _hx = IHEX(payable(hexAddress));
        _hxAddress = hexAddress;

        // create HSI implementation
        _hsiImplementation = address(new HEXStakeInstance());
        
        // initialize the HSI just in case
        HEXStakeInstance hsi = HEXStakeInstance(_hsiImplementation);
        hsi.initialize(hexAddress);
    }

    function _baseURI(
    )
        internal
        view
        virtual
        override
        returns (string memory)
    {
        string memory chainid = Strings.toString(block.chainid);
        return string(abi.encodePacked(_hostname, chainid, _endpoint));
    }

    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId
    )
        internal
        override(ERC721, ERC721Enumerable) 
    {
        super._beforeTokenTransfer(from, to, tokenId);
    }

    event HSIStart(
        uint256         timestamp,
        address indexed hsiAddress,
        address indexed staker
    );

    event HSIEnd(
        uint256         timestamp,
        address indexed hsiAddress,
        address indexed staker
    );

    event HSITransfer(
        uint256         timestamp,
        address indexed hsiAddress,
        address indexed oldStaker,
        address indexed newStaker
    );

    event HSITokenize(
        uint256         timestamp,
        uint256 indexed hsiTokenId,
        address indexed hsiAddress,
        address indexed staker
    );

    event HSIDetokenize(
        uint256         timestamp,
        uint256 indexed hsiTokenId,
        address indexed hsiAddress,
        address indexed staker
    );

    /**
     * @dev Removes a HEX stake instance (HSI) contract address from an address mapping.
     * @param hsiList A mapped list of HSI contract addresses.
     * @param hsiIndex The index of the HSI contract address which will be removed.
     */
    function _pruneHSI(
        address[] storage hsiList,
        uint256 hsiIndex
    )
        internal
    {
        uint256 lastIndex = hsiList.length - 1;

        if (hsiIndex != lastIndex) {
            hsiList[hsiIndex] = hsiList[lastIndex];
        }

        hsiList.pop();
    }

    /**
     * @dev Loads share data from a HEX stake instance (HSI) into a "ShareCache" object.
     * @param hsi A HSI contract object from which share data will be loaded.
     * @return "ShareCache" object containing the loaded share data.
     */
    function _hsiLoad(
        HEXStakeInstance hsi
    ) 
        internal
        view
        returns (ShareCache memory)
    {
        HEXStakeMinimal memory stake;
        uint16                 mintedDays;
        uint8                  launchBonus;
        uint16                 loanStart;
        uint16                 loanedDays;
        uint32                 interestRate;
        uint8                  paymentsMade;
        bool                   isLoaned;

        (stake,
         mintedDays,
         launchBonus,
         loanStart,
         loanedDays,
         interestRate,
         paymentsMade,
         isLoaned) = hsi.share();

        return ShareCache(
            stake,
            mintedDays,
            launchBonus,
            loanStart,
            loanedDays,
            interestRate,
            paymentsMade,
            isLoaned
        );
    }

    // Internal NFT Marketplace Glue

    /** @dev Sets the Rarible V2 royalties on a specific token
     *  @param tokenId Unique ID of the HSI NFT token.
     */
    function _setRoyalties(
        uint256 tokenId
    )
        internal
    {
        LibPart.Part[] memory _royalties = new LibPart.Part[](1);
        _royalties[0].value = _hsimRoyaltyBasis;
        _royalties[0].account = payable(_hdrnFlowAddress);
        _saveRoyalties(tokenId, _royalties);
    }

    /**
     * @dev Retreives the number of HSI elements in an addresses HSI list.
     * @param user Address to retrieve the HSI list for.
     * @return Number of HSI elements found within the HSI list.
     */
    function hsiCount(
        address user
    )
        public
        view
        returns (uint256)
    {
        return hsiLists[user].length;
    }

    /**
     * @dev Wrapper function for hsiCount to allow HEX based applications to pull stake data.
     * @param user Address to retrieve the HSI list for.
     * @return Number of HSI elements found within the HSI list. 
     */
    function stakeCount(
        address user
    )
        external
        view
        returns (uint256)
    {
        return hsiCount(user);
    }

    /**
     * @dev Wrapper function for hsiLists to allow HEX based applications to pull stake data.
     * @param user Address to retrieve the HSI list for.
     * @param hsiIndex The index of the HSI contract address which will returned. 
     * @return "HEXStake" object containing HEX stake data. 
     */
    function stakeLists(
        address user,
        uint256 hsiIndex
    )
        external
        view
        returns (HEXStake memory)
    {
        address[] storage hsiList = hsiLists[user];

        HEXStakeInstance hsi = HEXStakeInstance(hsiList[hsiIndex]);

        return hsi.stakeDataFetch();
    }

    /**
     * @dev Creates a new HEX stake instance (HSI), transfers HEX ERC20 tokens to the
     *      HSI's contract address, and calls the "initialize" function.
     * @param amount Number of HEX ERC20 tokens to be staked.
     * @param length Number of days the HEX ERC20 tokens will be staked.
     * @return Address of the newly created HSI contract.
     */
    function hexStakeStart (
        uint256 amount,
        uint256 length
    )
        external
        returns (address)
    {
        require(amount <= _hx.balanceOf(msg.sender),
            "HSIM: Insufficient HEX to facilitate stake");

        address[] storage hsiList = hsiLists[msg.sender];

        address hsiAddress = Clones.clone(_hsiImplementation);
        HEXStakeInstance hsi = HEXStakeInstance(hsiAddress);
        hsi.initialize(_hxAddress);

        hsiList.push(hsiAddress);
        uint256 hsiIndex = hsiList.length - 1;

        require(_hx.transferFrom(msg.sender, hsiAddress, amount),
            "HSIM: HEX transfer from message sender to HSIM failed");

        hsi.create(length);

        IHedron hedron = IHedron(_creator);
        hedron.claimInstanced(hsiIndex, hsiAddress, msg.sender);

        emit HSIStart(block.timestamp, hsiAddress, msg.sender);

        return hsiAddress;
    }

    /**
     * @dev Calls the HEX stake instance (HSI) function "destroy", transfers HEX ERC20 tokens
     *      from the HSI's contract address to the senders address.
     * @param hsiIndex Index of the HSI contract's address in the caller's HSI list.
     * @param hsiAddress Address of the HSI contract in which to call the "destroy" function.
     * @return Amount of HEX ERC20 tokens awarded via ending the HEX stake.
     */
    function hexStakeEnd (
        uint256 hsiIndex,
        address hsiAddress
    )
        external
        returns (uint256)
    {
        address[] storage hsiList = hsiLists[msg.sender];

        require(hsiAddress == hsiList[hsiIndex],
            "HSIM: HSI index address mismatch");

        HEXStakeInstance hsi = HEXStakeInstance(hsiAddress);
        ShareCache memory share = _hsiLoad(hsi);

        require (share._isLoaned == false,
            "HSIM: Cannot call stakeEnd against a loaned stake");

        hsi.destroy();

        emit HSIEnd(block.timestamp, hsiAddress, msg.sender);

        uint256 hsiBalance = _hx.balanceOf(hsiAddress);

        if (hsiBalance > 0) {
            require(_hx.transferFrom(hsiAddress, msg.sender, hsiBalance),
                "HSIM: HEX transfer from HSI failed");
        }

        _pruneHSI(hsiList, hsiIndex);

        return hsiBalance;
    }

    /**
     * @dev Converts a HEX stake instance (HSI) contract address mapping into a
     *      HSI ERC721 token.
     * @param hsiIndex Index of the HSI contract's address in the caller's HSI list.
     * @param hsiAddress Address of the HSI contract to be converted.
     * @return Token ID of the newly minted HSI ERC721 token.
     */
    function hexStakeTokenize (
        uint256 hsiIndex,
        address hsiAddress
    )
        external
        returns (uint256)
    {
        address[] storage hsiList = hsiLists[msg.sender];

        require(hsiAddress == hsiList[hsiIndex],
            "HSIM: HSI index address mismatch");

        HEXStakeInstance hsi = HEXStakeInstance(hsiAddress);
        ShareCache memory share = _hsiLoad(hsi);

        require (share._isLoaned == false,
            "HSIM: Cannot tokenize a loaned stake");

        _tokenIds.increment();

        uint256 newTokenId = _tokenIds.current();

        _mint(msg.sender, newTokenId);
         hsiToken[newTokenId] = hsiAddress;

        _setRoyalties(newTokenId);

        _pruneHSI(hsiList, hsiIndex);

        emit HSITokenize(
            block.timestamp,
            newTokenId,
            hsiAddress,
            msg.sender
        );

        return newTokenId;
    }

    /**
     * @dev Converts a HEX stake instance (HSI) ERC721 token into an address mapping.
     * @param tokenId ID of the HSI ERC721 token to be converted.
     * @return Address of the detokenized HSI contract.
     */
    function hexStakeDetokenize (
        uint256 tokenId
    )
        external
        returns (address)
    {
        require(ownerOf(tokenId) == msg.sender,
            "HSIM: Detokenization requires token ownership");

        address hsiAddress = hsiToken[tokenId];
        address[] storage hsiList = hsiLists[msg.sender];

        hsiList.push(hsiAddress);
        hsiToken[tokenId] = address(0);

        _burn(tokenId);

        emit HSIDetokenize(
            block.timestamp,
            tokenId, 
            hsiAddress,
            msg.sender
        );

        return hsiAddress;
    }

    /**
     * @dev Updates the share data of a HEX stake instance (HSI) contract.
     *      This is a pivileged operation only Hedron.sol can call.
     * @param holder Address of the HSI contract owner.
     * @param hsiIndex Index of the HSI contract's address in the holder's HSI list.
     * @param hsiAddress Address of the HSI contract to be updated.
     * @param share "ShareCache" object containing updated share data.
     */
    function hsiUpdate (
        address holder,
        uint256 hsiIndex,
        address hsiAddress,
        ShareCache memory share
    )
        external
    {
        require(msg.sender == _creator,
            "HSIM: Caller must be contract creator");

        address[] storage hsiList = hsiLists[holder];

        require(hsiAddress == hsiList[hsiIndex],
            "HSIM: HSI index address mismatch");

        HEXStakeInstance hsi = HEXStakeInstance(hsiAddress);
        hsi.update(share);
    }

    /**
     * @dev Transfers ownership of a HEX stake instance (HSI) contract to a new address.
     *      This is a pivileged operation only Hedron.sol can call. End users can use
     *      the NFT tokenize / detokenize to handle HSI transfers.
     * @param currentHolder Address to transfer the HSI contract from.
     * @param hsiIndex Index of the HSI contract's address in the currentHolder's HSI list.
     * @param hsiAddress Address of the HSI contract to be transfered.
     * @param newHolder Address to transfer to HSI contract to.
     */
    function hsiTransfer (
        address currentHolder,
        uint256 hsiIndex,
        address hsiAddress,
        address newHolder
    )
        external
    {
        require(msg.sender == _creator,
            "HSIM: Caller must be contract creator");

        address[] storage hsiListCurrent = hsiLists[currentHolder];
        address[] storage hsiListNew = hsiLists[newHolder];

        require(hsiAddress == hsiListCurrent[hsiIndex],
            "HSIM: HSI index address mismatch");

        hsiListNew.push(hsiAddress);
        _pruneHSI(hsiListCurrent, hsiIndex);

        emit HSITransfer(
                    block.timestamp,
                    hsiAddress,
                    currentHolder,
                    newHolder
                );
    }

    // External NFT Marketplace Glue

    /**
     * @dev Implements ERC2981 royalty functionality. We just read the royalty data from
     *      the Rarible V2 implementation. 
     * @param tokenId Unique ID of the HSI NFT token.
     * @param salePrice Price the HSI NFT token was sold for.
     * @return receiver address to send the royalties to as well as the royalty amount.
     */
    function royaltyInfo(
        uint256 tokenId,
        uint256 salePrice
    )
        external
        view
        returns (address receiver, uint256 royaltyAmount)
    {
        LibPart.Part[] memory _royalties = royalties[tokenId];
        
        if (_royalties.length > 0) {
            return (_royalties[0].account, (salePrice * _royalties[0].value) / 10000);
        }

        return (address(0), 0);
    }

    /**
     * @dev returns _hdrnFlowAddress, needed for some NFT marketplaces. This is not
     *       an admin key.
     * @return _hdrnFlowAddress
     */
    function owner(
    )
        external
        pure
        returns (address) 
    {
        return _hdrnFlowAddress;
    }

    /**
     * @dev Adds Rarible V2 and ERC2981 interface support.
     * @param interfaceId Unique contract interface identifier.
     * @return True if the interface is supported, false if not.
     */
    function supportsInterface(
        bytes4 interfaceId
    )
        public
        view
        virtual
        override(ERC721, ERC721Enumerable)
        returns (bool)
    {
        if (interfaceId == LibRoyaltiesV2._INTERFACE_ID_ROYALTIES) {
            return true;
        }

        if (interfaceId == _INTERFACE_ID_ERC2981) {
            return true;
        }

        return super.supportsInterface(interfaceId);
    }
}