// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (utils/Address.sol)

pragma solidity ^0.8.1;

/**
 * @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
     * ====
     *
     * [IMPORTANT]
     * ====
     * You shouldn't rely on `isContract` to protect against flash loan attacks!
     *
     * Preventing calls from contracts is highly discouraged. It breaks composability, breaks support for smart wallets
     * like Gnosis Safe, and does not provide security since it can be circumvented by calling from a contract
     * constructor.
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize/address.code.length, which returns 0
        // for contracts in construction, since the code is only stored at the end
        // of the constructor execution.

        return account.code.length > 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 functionCallWithValue(target, data, 0, "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");
        (bool success, bytes memory returndata) = target.call{value: value}(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.staticcall(data);
        return verifyCallResultFromTarget(target, 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) {
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return verifyCallResultFromTarget(target, success, returndata, errorMessage);
    }

    /**
     * @dev Tool to verify that a low level call to smart-contract was successful, and revert (either by bubbling
     * the revert reason or using the provided one) in case of unsuccessful call or if target was not a contract.
     *
     * _Available since v4.8._
     */
    function verifyCallResultFromTarget(
        address target,
        bool success,
        bytes memory returndata,
        string memory errorMessage
    ) internal view returns (bytes memory) {
        if (success) {
            if (returndata.length == 0) {
                // only check isContract if the call was successful and the return data is empty
                // otherwise we already know that it was a contract
                require(isContract(target), "Address: call to non-contract");
            }
            return returndata;
        } else {
            _revert(returndata, errorMessage);
        }
    }

    /**
     * @dev Tool to verify that a low level call was successful, and revert if it wasn't, either by bubbling the
     * revert reason or 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 {
            _revert(returndata, errorMessage);
        }
    }

    function _revert(bytes memory returndata, string memory errorMessage) private pure {
        // 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
            /// @solidity memory-safe-assembly
            assembly {
                let returndata_size := mload(returndata)
                revert(add(32, returndata), returndata_size)
            }
        } else {
            revert(errorMessage);
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

pragma solidity ^0.8.0;

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

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

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;

import "./IERC20.sol";
import "./extensions/IERC20Metadata.sol";
import "../../utils/Context.sol";

/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin Contracts guidelines: functions revert
 * instead returning `false` on failure. This behavior is nonetheless
 * conventional and does not conflict with the expectations of ERC20
 * applications.
 *
 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
 * This allows applications to reconstruct the allowance for all accounts just
 * by listening to said events. Other implementations of the EIP may not emit
 * these events, as it isn't required by the specification.
 *
 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
 * functions have been added to mitigate the well-known issues around setting
 * allowances. See {IERC20-approve}.
 */
contract ERC20 is Context, IERC20, IERC20Metadata {
    mapping(address => uint256) private _balances;

    mapping(address => mapping(address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;

    /**
     * @dev Sets the values for {name} and {symbol}.
     *
     * The default value of {decimals} is 18. To select a different value for
     * {decimals} you should overload it.
     *
     * All two of these values are immutable: they can only be set once during
     * construction.
     */
    constructor(string memory name_, string memory symbol_) {
        _name = name_;
        _symbol = symbol_;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view virtual override returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view virtual override returns (string memory) {
        return _symbol;
    }

    /**
     * @dev Returns the number of decimals used to get its user representation.
     * For example, if `decimals` equals `2`, a balance of `505` tokens should
     * be displayed to a user as `5.05` (`505 / 10 ** 2`).
     *
     * Tokens usually opt for a value of 18, imitating the relationship between
     * Ether and Wei. This is the value {ERC20} uses, unless this function is
     * overridden;
     *
     * NOTE: This information is only used for _display_ purposes: it in
     * no way affects any of the arithmetic of the contract, including
     * {IERC20-balanceOf} and {IERC20-transfer}.
     */
    function decimals() public view virtual override returns (uint8) {
        return 18;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view virtual override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `to` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address to, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _transfer(owner, to, amount);
        return true;
    }

    /**
     * @dev See {IERC20-allowance}.
     */
    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    /**
     * @dev See {IERC20-approve}.
     *
     * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
     * `transferFrom`. This is semantically equivalent to an infinite approval.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, amount);
        return true;
    }

    /**
     * @dev See {IERC20-transferFrom}.
     *
     * Emits an {Approval} event indicating the updated allowance. This is not
     * required by the EIP. See the note at the beginning of {ERC20}.
     *
     * NOTE: Does not update the allowance if the current allowance
     * is the maximum `uint256`.
     *
     * Requirements:
     *
     * - `from` and `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     * - the caller must have allowance for ``from``'s tokens of at least
     * `amount`.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual override returns (bool) {
        address spender = _msgSender();
        _spendAllowance(from, spender, amount);
        _transfer(from, to, amount);
        return true;
    }

    /**
     * @dev Atomically increases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        address owner = _msgSender();
        _approve(owner, spender, allowance(owner, spender) + addedValue);
        return true;
    }

    /**
     * @dev Atomically decreases the allowance granted to `spender` by the caller.
     *
     * This is an alternative to {approve} that can be used as a mitigation for
     * problems described in {IERC20-approve}.
     *
     * Emits an {Approval} event indicating the updated allowance.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `spender` must have allowance for the caller of at least
     * `subtractedValue`.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        address owner = _msgSender();
        uint256 currentAllowance = allowance(owner, spender);
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `from` to `to`.
     *
     * This internal function is equivalent to {transfer}, and can be used to
     * e.g. implement automatic token fees, slashing mechanisms, etc.
     *
     * Emits a {Transfer} event.
     *
     * Requirements:
     *
     * - `from` cannot be the zero address.
     * - `to` cannot be the zero address.
     * - `from` must have a balance of at least `amount`.
     */
    function _transfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {
        require(from != address(0), "ERC20: transfer from the zero address");
        require(to != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(from, to, amount);

        uint256 fromBalance = _balances[from];
        require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[from] = fromBalance - amount;
            // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
            // decrementing then incrementing.
            _balances[to] += amount;
        }

        emit Transfer(from, to, amount);

        _afterTokenTransfer(from, to, amount);
    }

    /** @dev Creates `amount` tokens and assigns them to `account`, increasing
     * the total supply.
     *
     * Emits a {Transfer} event with `from` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     */
    function _mint(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), account, amount);

        _totalSupply += amount;
        unchecked {
            // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
            _balances[account] += amount;
        }
        emit Transfer(address(0), account, amount);

        _afterTokenTransfer(address(0), account, amount);
    }

    /**
     * @dev Destroys `amount` tokens from `account`, reducing the
     * total supply.
     *
     * Emits a {Transfer} event with `to` set to the zero address.
     *
     * Requirements:
     *
     * - `account` cannot be the zero address.
     * - `account` must have at least `amount` tokens.
     */
    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");

        _beforeTokenTransfer(account, address(0), amount);

        uint256 accountBalance = _balances[account];
        require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
        unchecked {
            _balances[account] = accountBalance - amount;
            // Overflow not possible: amount <= accountBalance <= totalSupply.
            _totalSupply -= amount;
        }

        emit Transfer(account, address(0), amount);

        _afterTokenTransfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
     *
     * This internal function is equivalent to `approve`, and can be used to
     * e.g. set automatic allowances for certain subsystems, etc.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `owner` cannot be the zero address.
     * - `spender` cannot be the zero address.
     */
    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    /**
     * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
     *
     * Does not update the allowance amount in case of infinite allowance.
     * Revert if not enough allowance is available.
     *
     * Might emit an {Approval} event.
     */
    function _spendAllowance(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        uint256 currentAllowance = allowance(owner, spender);
        if (currentAllowance != type(uint256).max) {
            require(currentAllowance >= amount, "ERC20: insufficient allowance");
            unchecked {
                _approve(owner, spender, currentAllowance - amount);
            }
        }
    }

    /**
     * @dev Hook that is called before any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * will be transferred to `to`.
     * - when `from` is zero, `amount` tokens will be minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens 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 amount
    ) internal virtual {}

    /**
     * @dev Hook that is called after any transfer of tokens. This includes
     * minting and burning.
     *
     * Calling conditions:
     *
     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
     * has been transferred to `to`.
     * - when `from` is zero, `amount` tokens have been minted for `to`.
     * - when `to` is zero, `amount` of ``from``'s tokens have been 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 _afterTokenTransfer(
        address from,
        address to,
        uint256 amount
    ) internal virtual {}
}

// SPDX-License-Identifier: BUSL-1.1
pragma solidity ^0.8.11;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

interface IGumBallFactory {
    function getTreasury() external view returns (address);
}

interface IXGBT {
    function balanceOf(address account) external view returns (uint256);
    function notifyRewardAmount(address _rewardsToken, uint256 reward) external; 
}

contract GBT is ERC20, ReentrancyGuard {
    using SafeERC20 for IERC20;

    // Bonding Curve Variables
    address public immutable BASE_TOKEN;

    uint256 public immutable reserveVirtualBASE;
    uint256 public reserveRealBASE;
    uint256 public reserveGBT;
    
    uint256 public immutable initial_totalSupply;

    // Treasury Variables
    uint256 public treasuryBASE;
    uint256 public treasuryGBT;

    // Addresses
    address public XGBT;
    address public artist;
    address public immutable factory;

    // Allowlist Variables
    mapping(address => bool) public allowlist;
    mapping(address => uint256) public limit;
    uint256 public immutable start;
    uint256 public immutable delay;

    // Borrow Variables
    uint256 public borrowedTotalBASE;
    mapping(address => uint256) public borrowedBASE;

    // Fee
    uint256 public constant PROTOCOL = 25;
    uint256 public constant TREASURY = 200;
    uint256 public constant GUMBAR = 400;
    uint256 public constant ARTIST = 400;
    uint256 public constant DIVISOR = 1000;

    // Events
    event Buy(address indexed user, uint256 amount);
    event Sell(address indexed user, uint256 amount);
    event Borrow(address indexed user, uint256 amount);
    event Repay(address indexed user, uint256 amount);
    event Skim(address indexed user);
    event AllowListUpdated(address[] accounts, bool flag);
    event XGBTSet(address indexed _XGBT);
    event ChangeArtist(address newArtist);

    constructor(
        string memory _name,
        string memory _symbol,
        address _baseToken,
        uint256 _initialVirtualBASE,
        uint256 _supplyGBT,
        address _artist,
        address _factory,
        uint256 _delay
        ) ERC20(_name, _symbol) {

        BASE_TOKEN = _baseToken;
        artist = _artist;
        factory = _factory;

        reserveVirtualBASE = _initialVirtualBASE;

        reserveRealBASE = 0;
        initial_totalSupply = _supplyGBT;
        reserveGBT = _supplyGBT;

        start = block.timestamp;
        delay = _delay;

        _mint(address(this), _supplyGBT);

    }

    //////////////////
    ///// Public /////
    //////////////////

    /** @dev returns the current price of {GBT} */
    function currentPrice() external view returns (uint256) {
        return ((reserveVirtualBASE + reserveRealBASE) * 1e18) / reserveGBT;
    }

    /** @dev returns the allowance @param user can borrow */
    function borrowCredit(address account) external view returns (uint256) {
        uint256 borrowPowerGBT = IXGBT(XGBT).balanceOf(account);
        if (borrowPowerGBT == 0) {
            return 0;
        }
        uint256 borrowTotalBASE = (reserveVirtualBASE * totalSupply() / (totalSupply() - borrowPowerGBT)) - reserveVirtualBASE;
        uint256 borrowableBASE = borrowTotalBASE - borrowedBASE[account];
        return borrowableBASE;
    }

    function skimReward() external view returns (uint256) {
        return treasuryBASE * 10 / 10000;
    }

    /** @dev returns amount borrowed by @param user */
    function debt(address account) external view returns (uint256) {
        return borrowedBASE[account];
    }

    function baseBal() external view returns (uint256) {
        return IERC20(BASE_TOKEN).balanceOf(address(this));
    }

    function gbtBal() external view returns (uint256) {
        return IERC20(address(this)).balanceOf(address(this));
    }

    function getFactory() external view returns (address) {
        return factory;
    }

    function initSupply() external view returns (uint256) {
        return initial_totalSupply;
    }

    function floorPrice() external view returns (uint256) {
        return (reserveVirtualBASE * 1e18) / totalSupply();
    }

    function mustStayGBT(address account) external view returns (uint256) {
        uint256 accountBorrowedBASE = borrowedBASE[account];
        if (accountBorrowedBASE == 0) {
            return 0;
        }
        uint256 amount = totalSupply() - (reserveVirtualBASE * totalSupply() / (accountBorrowedBASE + reserveVirtualBASE));
        return amount;
    }

    ////////////////////
    ///// External /////
    ////////////////////

    /** @dev Buy function.  User spends {BASE} and receives {GBT}
      * @param _amountBASE is the amount of the {BASE} being spent
      * @param _minGBT is the minimum amount of {GBT} out
      * @param expireTimestamp is the expire time on txn
      *
      * If a delay was set on the proxy deployment and has not elapsed:
      *     1. the user must be whitelisted by the protocol to call the function
      *     2. the whitelisted user cannont buy more than 1 GBT until the delay has elapsed
    */
    function buy(uint256 _amountBASE, uint256 _minGBT, uint256 expireTimestamp) external nonReentrant {
        require(start + delay <= block.timestamp || allowlist[msg.sender], "Market Closed");
        require(expireTimestamp == 0 || expireTimestamp > block.timestamp, "Expired");
        require(_amountBASE > 0, "Amount cannot be zero");

        address account = msg.sender;

        syncReserves();
        uint256 feeAmountBASE = _amountBASE * PROTOCOL / DIVISOR;
        treasuryBASE += (feeAmountBASE);

        uint256 oldReserveBASE = reserveVirtualBASE + reserveRealBASE;
        uint256 newReserveBASE = oldReserveBASE + _amountBASE - feeAmountBASE;

        uint256 oldReserveGBT = reserveGBT;
        uint256 newReserveGBT = oldReserveBASE * oldReserveGBT / newReserveBASE;

        uint256 outGBT = oldReserveGBT - newReserveGBT;

        require(outGBT > _minGBT, "Less than Min");

        if (start + delay >= block.timestamp) {
            require(outGBT <= 10e18 && limit[account] <= 10e18, "Over allowlist limit");
            limit[account] += outGBT;
            require(limit[account] <= 10e18, "Allowlist amount overflow");
        }

        reserveRealBASE = newReserveBASE - reserveVirtualBASE;
        reserveGBT = newReserveGBT;

        IERC20(BASE_TOKEN).safeTransferFrom(account, address(this), _amountBASE);
        IERC20(address(this)).safeTransfer(account, outGBT);

        emit Buy(account, _amountBASE);
    }

    /** @dev Sell function.  User sells their {GBT} token for {BASE}
      * @param _amountGBT is the amount of {GBT} in
      * @param _minETH is the minimum amount of {ETH} out 
      * @param expireTimestamp is the expire time on txn
    */
    function sell(uint256 _amountGBT, uint256 _minETH, uint256 expireTimestamp) external nonReentrant {
        require(expireTimestamp == 0 || expireTimestamp > block.timestamp, "Expired");
        require(_amountGBT > 0, "Amount cannot be zero");

        address account = msg.sender;

        syncReserves();
        uint256 feeAmountGBT = _amountGBT * PROTOCOL / DIVISOR;
        treasuryGBT += feeAmountGBT;

        uint256 oldReserveGBT = reserveGBT;
        uint256 newReserveGBT = reserveGBT + _amountGBT - feeAmountGBT;

        uint256 oldReserveBASE = reserveVirtualBASE + reserveRealBASE;
        uint256 newReserveBASE = oldReserveBASE * oldReserveGBT / newReserveGBT;

        uint256 outBASE = oldReserveBASE - newReserveBASE;

        require(outBASE > _minETH, "Less than Min");

        reserveRealBASE = newReserveBASE - reserveVirtualBASE;
        reserveGBT = newReserveGBT;

        IERC20(address(this)).safeTransferFrom(account, address(this), _amountGBT);
        IERC20(BASE_TOKEN).safeTransfer(account, outBASE);

        emit Sell(account, _amountGBT);
    }

    /** @dev Distributes fees according to their weights.  Rewards the caller 0.1% of {treasuryBASE} */
    function treasurySkim() external {
        uint256 _treasuryGBT = treasuryGBT;
        uint256 _treasuryBASE = treasuryBASE;

        // Reward for the caller
        uint256 reward = _treasuryBASE * 10 / 10000;   // 0.1%
        _treasuryBASE -= reward;

        treasuryBASE = 0;
        treasuryGBT = 0;

        address treasury = IGumBallFactory(factory).getTreasury();

        IERC20(address(this)).safeApprove(XGBT, 0);
        IERC20(address(this)).safeApprove(XGBT, _treasuryGBT * GUMBAR / DIVISOR);
        IXGBT(XGBT).notifyRewardAmount(address(this), _treasuryGBT * GUMBAR / DIVISOR);
        IERC20(address(this)).safeTransfer(artist, _treasuryGBT * ARTIST / DIVISOR);
        IERC20(address(this)).safeTransfer(treasury, _treasuryGBT * TREASURY / DIVISOR);

        // requires here
        IERC20(BASE_TOKEN).safeApprove(XGBT, 0);
        IERC20(BASE_TOKEN).safeApprove(XGBT, _treasuryBASE * GUMBAR / DIVISOR);
        IXGBT(XGBT).notifyRewardAmount(BASE_TOKEN, _treasuryBASE * GUMBAR / DIVISOR);
        IERC20(BASE_TOKEN).safeTransfer(artist, _treasuryBASE * ARTIST / DIVISOR);
        IERC20(BASE_TOKEN).safeTransfer(treasury, _treasuryBASE * TREASURY / DIVISOR);
        IERC20(BASE_TOKEN).safeTransfer(msg.sender, reward);

        emit Skim(msg.sender);
    }

    /** @dev User borrows an amount of {BASE} equal to @param _amount */
    function borrowSome(uint256 _amount) external nonReentrant {
        require(_amount > 0, "!Zero");

        address account = msg.sender;

        uint256 borrowPowerGBT = IXGBT(XGBT).balanceOf(account);

        uint256 borrowTotalBASE = (reserveVirtualBASE * totalSupply() / (totalSupply() - borrowPowerGBT)) - reserveVirtualBASE;
        uint256 borrowableBASE = borrowTotalBASE - borrowedBASE[account];

        require(borrowableBASE >= _amount, "Borrow Underflow");

        borrowedBASE[account] += _amount;
        borrowedTotalBASE += _amount;

        IERC20(BASE_TOKEN).safeTransfer(account, _amount);

        emit Borrow(account, _amount);
    }

    /** @dev User borrows the maximum amount of {BASE} their locked {XGBT} will allow */
    function borrowMax() external nonReentrant {

        address account = msg.sender;

        uint256 borrowPowerGBT = IXGBT(XGBT).balanceOf(account);

        uint256 borrowTotalBASE = (reserveVirtualBASE * totalSupply() / (totalSupply() - borrowPowerGBT)) - reserveVirtualBASE;
        uint256 borrowableBASE = borrowTotalBASE - borrowedBASE[account];

        borrowedBASE[account] += borrowableBASE;
        borrowedTotalBASE += borrowableBASE;

        IERC20(BASE_TOKEN).safeTransfer(account, borrowableBASE);

        emit Borrow(account, borrowableBASE);
    }

    /** @dev User repays a portion of their debt equal to @param _amount */
    function repaySome(uint256 _amount) external nonReentrant {
        require(_amount > 0, "!Zero");

        address account = msg.sender;
        
        borrowedBASE[account] -= _amount;
        borrowedTotalBASE -= _amount;

        IERC20(BASE_TOKEN).safeTransferFrom(account, address(this), _amount);

        emit Repay(account, _amount);
    }

    /** @dev User repays their debt and opens unlocking of {XGBT} */
    function repayMax() external nonReentrant {

        address account = msg.sender;

        uint256 amountRepayBASE = borrowedBASE[account];
        borrowedBASE[account] = 0;
        borrowedTotalBASE -= amountRepayBASE;

        IERC20(BASE_TOKEN).safeTransferFrom(account, address(this), amountRepayBASE);

        emit Repay(account, amountRepayBASE);
    }

    ////////////////////
    ///// Internal /////
    ////////////////////

    /** @dev Remove yield and rebalance */
    function syncReserves() internal {
        uint256 baseBalance = IERC20(BASE_TOKEN).balanceOf(address(this)) + borrowedTotalBASE;
        if(baseBalance > reserveRealBASE + treasuryBASE) {
            treasuryBASE += (baseBalance - reserveRealBASE - treasuryBASE);
        }
        uint256 gbtBalance = IERC20(address(this)).balanceOf(address(this));
        if (gbtBalance > reserveGBT + treasuryGBT) {
            treasuryGBT += (gbtBalance - reserveGBT - treasuryGBT);
        }
    }

    ////////////////////
    //// Restricted ////
    ////////////////////

    function updateAllowlist(address[] memory accounts, bool _bool) external {
        require(msg.sender == factory || msg.sender == artist, "!AUTH");
        for (uint256 i = 0; i < accounts.length; i++) {
            allowlist[accounts[i]] = _bool;
        }
        emit AllowListUpdated(accounts, _bool);
    }

    function setXGBT(address _XGBT) external OnlyFactory {
        XGBT = _XGBT;
        emit XGBTSet(_XGBT);
    }

    function setArtist(address _artist) external {
        require(msg.sender == artist, "!AUTH");
        artist = _artist;
        emit ChangeArtist(_artist);
    }

    modifier OnlyFactory() {
        require(msg.sender == factory, "!AUTH");
        _;
    }
}

contract GBTFactory {
    address public factory;
    address public lastGBT;

    event FactorySet(address indexed _factory);

    constructor() {
        factory = msg.sender;
    }

    function setFactory(address _factory) external OnlyFactory {
        factory = _factory;
        emit FactorySet(_factory);
    }

    function createGBT(
        string memory _name,
        string memory _symbol,
        address _baseToken,
        uint256 _initialVirtualBASE,
        uint256 _supplyGBT,
        address _artist,
        address _factory,
        uint256 _delay
    ) external OnlyFactory returns (address) {
        GBT newGBT = new GBT(_name, _symbol, _baseToken, _initialVirtualBASE, _supplyGBT, _artist, _factory, _delay);
        lastGBT = address(newGBT);
        return lastGBT;
    }

    modifier OnlyFactory() {
        require(msg.sender == factory, "!AUTH");
        _;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @dev Emitted when `value` tokens are moved from one account (`from`) to
     * another (`to`).
     *
     * Note that `value` may be zero.
     */
    event Transfer(address indexed from, address indexed to, uint256 value);

    /**
     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
     * a call to {approve}. `value` is the new allowance.
     */
    event Approval(address indexed owner, address indexed spender, uint256 value);

    /**
     * @dev Returns the amount of tokens in existence.
     */
    function totalSupply() external view returns (uint256);

    /**
     * @dev Returns the amount of tokens owned by `account`.
     */
    function balanceOf(address account) external view returns (uint256);

    /**
     * @dev Moves `amount` tokens from the caller's account to `to`.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transfer(address to, uint256 amount) external returns (bool);

    /**
     * @dev Returns the remaining number of tokens that `spender` will be
     * allowed to spend on behalf of `owner` through {transferFrom}. This is
     * zero by default.
     *
     * This value changes when {approve} or {transferFrom} are called.
     */
    function allowance(address owner, address spender) external view returns (uint256);

    /**
     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * IMPORTANT: Beware that changing an allowance with this method brings the risk
     * that someone may use both the old and the new allowance by unfortunate
     * transaction ordering. One possible solution to mitigate this race
     * condition is to first reduce the spender's allowance to 0 and set the
     * desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     *
     * Emits an {Approval} event.
     */
    function approve(address spender, uint256 amount) external returns (bool);

    /**
     * @dev Moves `amount` tokens from `from` to `to` using the
     * allowance mechanism. `amount` is then deducted from the caller's
     * allowance.
     *
     * Returns a boolean value indicating whether the operation succeeded.
     *
     * Emits a {Transfer} event.
     */
    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) external returns (bool);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";

/**
 * @dev Interface for the optional metadata functions from the ERC20 standard.
 *
 * _Available since v4.1._
 */
interface IERC20Metadata is IERC20 {
    /**
     * @dev Returns the name of the token.
     */
    function name() external view returns (string memory);

    /**
     * @dev Returns the symbol of the token.
     */
    function symbol() external view returns (string memory);

    /**
     * @dev Returns the decimals places of the token.
     */
    function decimals() external view returns (uint8);
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (security/ReentrancyGuard.sol)

pragma solidity ^0.8.0;

/**
 * @dev Contract module that helps prevent reentrant calls to a function.
 *
 * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
 * available, which can be applied to functions to make sure there are no nested
 * (reentrant) calls to them.
 *
 * Note that because there is a single `nonReentrant` guard, functions marked as
 * `nonReentrant` may not call one another. This can be worked around by making
 * those functions `private`, and then adding `external` `nonReentrant` entry
 * points to them.
 *
 * TIP: If you would like to learn more about reentrancy and alternative ways
 * to protect against it, check out our blog post
 * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
 */
abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor() {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and making it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        _nonReentrantBefore();
        _;
        _nonReentrantAfter();
    }

    function _nonReentrantBefore() private {
        // On the first call to nonReentrant, _status will be _NOT_ENTERED
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;
    }

    function _nonReentrantAfter() private {
        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/utils/SafeERC20.sol)

pragma solidity ^0.8.0;

import "../IERC20.sol";
import "../extensions/draft-IERC20Permit.sol";
import "../../../utils/Address.sol";

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using Address for address;

    function safeTransfer(
        IERC20 token,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(
        IERC20 token,
        address from,
        address to,
        uint256 value
    ) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        require(
            (value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        uint256 newAllowance = token.allowance(address(this), spender) + value;
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(
        IERC20 token,
        address spender,
        uint256 value
    ) internal {
        unchecked {
            uint256 oldAllowance = token.allowance(address(this), spender);
            require(oldAllowance >= value, "SafeERC20: decreased allowance below zero");
            uint256 newAllowance = oldAllowance - value;
            _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
        }
    }

    function safePermit(
        IERC20Permit token,
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) internal {
        uint256 nonceBefore = token.nonces(owner);
        token.permit(owner, spender, value, deadline, v, r, s);
        uint256 nonceAfter = token.nonces(owner);
        require(nonceAfter == nonceBefore + 1, "SafeERC20: permit did not succeed");
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address-functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) {
            // Return data is optional
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/draft-IERC20Permit.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on {IERC20-approve}, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit {
    /**
     * @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
     * given ``owner``'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

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