// File: @openzeppelin/contracts/utils/math/SafeMath.sol


// OpenZeppelin Contracts v4.4.1 (utils/math/SafeMath.sol)
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

// CAUTION
// This version of SafeMath should only be used with Solidity 0.8 or later,
// because it relies on the compiler's built in overflow checks.

/**
 * @dev Wrappers over Solidity's arithmetic operations.
 *
 * NOTE: `SafeMath` is generally not needed starting with Solidity 0.8, since the compiler
 * now has built in overflow checking.
 */
library SafeMath {
    /**
     * @dev Returns the addition of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            uint256 c = a + b;
            if (c < a) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the substraction of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b > a) return (false, 0);
            return (true, a - b);
        }
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
     *
     * _Available since v3.4._
     */
    function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
            // benefit is lost if 'b' is also tested.
            // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
            if (a == 0) return (true, 0);
            uint256 c = a * b;
            if (c / a != b) return (false, 0);
            return (true, c);
        }
    }

    /**
     * @dev Returns the division of two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a / b);
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
     *
     * _Available since v3.4._
     */
    function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
        unchecked {
            if (b == 0) return (false, 0);
            return (true, a % b);
        }
    }

    /**
     * @dev Returns the addition of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `+` operator.
     *
     * Requirements:
     *
     * - Addition cannot overflow.
     */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        return a + b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting on
     * overflow (when the result is negative).
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return a - b;
    }

    /**
     * @dev Returns the multiplication of two unsigned integers, reverting on
     * overflow.
     *
     * Counterpart to Solidity's `*` operator.
     *
     * Requirements:
     *
     * - Multiplication cannot overflow.
     */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        return a * b;
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator.
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return a / b;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting when dividing by zero.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return a % b;
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {trySub}.
     *
     * Counterpart to Solidity's `-` operator.
     *
     * Requirements:
     *
     * - Subtraction cannot overflow.
     */
    function sub(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b <= a, errorMessage);
            return a - b;
        }
    }

    /**
     * @dev Returns the integer division of two unsigned integers, reverting with custom message on
     * division by zero. The result is rounded towards zero.
     *
     * Counterpart to Solidity's `/` operator. Note: this function uses a
     * `revert` opcode (which leaves remaining gas untouched) while Solidity
     * uses an invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function div(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a / b;
        }
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * reverting with custom message when dividing by zero.
     *
     * CAUTION: This function is deprecated because it requires allocating memory for the error
     * message unnecessarily. For custom revert reasons use {tryMod}.
     *
     * Counterpart to Solidity's `%` operator. This function uses a `revert`
     * opcode (which leaves remaining gas untouched) while Solidity uses an
     * invalid opcode to revert (consuming all remaining gas).
     *
     * Requirements:
     *
     * - The divisor cannot be zero.
     */
    function mod(
        uint256 a,
        uint256 b,
        string memory errorMessage
    ) internal pure returns (uint256) {
        unchecked {
            require(b > 0, errorMessage);
            return a % b;
        }
    }
}

// File: @openzeppelin/contracts/utils/Context.sol


// 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;
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol


// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

pragma solidity ^0.8.0;


/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(newOwner != address(0), "Ownable: new owner is the zero address");
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol


// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/IERC20.sol)

pragma solidity ^0.8.0;

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
    /**
     * @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);

    /**
     * @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);
}

// File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol


// OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)

pragma solidity ^0.8.0;


/**
 * @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);
}

// File: @openzeppelin/contracts/token/ERC20/ERC20.sol


// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/ERC20.sol)

pragma solidity ^0.8.0;




/**
 * @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.zeppelin.solutions/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, _allowances[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 = _allowances[owner][spender];
        require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
        unchecked {
            _approve(owner, spender, currentAllowance - subtractedValue);
        }

        return true;
    }

    /**
     * @dev Moves `amount` of tokens from `sender` to `recipient`.
     *
     * 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;
        }
        _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;
        _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;
        }
        _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 Spend `amount` form the allowance of `owner` toward `spender`.
     *
     * 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 {}
}

// File: contracts/satoshi.sol

/**
 *Submitted for verification at BscScan.com on 2021-12-06
 */


pragma solidity ^0.8.0;




contract SatoshiViralStake is Ownable {
    using SafeMath for uint256;

    // stakeToken address (SATs)
    // 0x1f9840a85d5aF5bf1D1762F925BDADdC4201F984 : UNI
    IERC20 public stakeToken;
    // rewardToken address (WBTC)
    // 0x110a13FC3efE6A245B50102D2d79B3E76125Ae83 : USDT
    IERC20 public rewardToken;

    // maxStakableToken : available stakable token maximan amount
    // first totalSupply, second can be set
    uint256 public maxStakeableToken;
    // minStakableToken : available stakable token minimam amount
    // first 1e18, second can be set
    uint256 public minimumStakeToken;

    // total amount of unstaked token
    uint256 public totalUnStakedToken;
    // total amount of staked token
    uint256 public totalStakedToken;
    // total amount of claimed reward token
    uint256 public totalClaimedRewardToken;
    // total stakers : user array
    uint256 public totalStakers;

    // percent divider : proportion
    uint256 public percentDivider;
    // duration : lock time
    uint256 public Duration = 3600 * 24 * 7 seconds;
    // bonus : how much reward can be get
    uint256 public Bonus = 1;

    // Stake
    struct Stake {
        uint256 unstaketime; // when unstake is available
        uint256 staketime; // when token is staked
        uint256 amount; // amount of staked token
        uint256 reward; // amount of ward (total)
        uint256 availableUnstakedAmount;
        uint256 availableUnclaimedReward;
        bool withdrawn; // status : reward is taken
        bool unstaked; // status : stakeToken is unstaked
    }

    struct User {
        uint256 totalStakedTokenUser; // how much token did user stake
        uint256 totalUnstakedTokenUser; // how much token did user unstake
        uint256 totalClaimedRewardTokenUser; // how much reward did user claim
        uint256 stakeCount; // how many times did user stake
        bool alreadyExists; // is this user already exist?
    }

    // user array : addreess => user
    mapping(address => User) public Stakers;
    // staker id array : id => address
    mapping(uint256 => address) public StakersID;
    // record of stakers : address => id => Stake
    mapping(address => mapping(uint256 => Stake)) public stakersRecord;

    // STAKE event
    event STAKE(address Staker, uint256 amount);
    // UNSTAKE event
    event UNSTAKE(address Staker, uint256 amount);
    // CLAIM event
    event CLAIM(address Staker, uint256 amount);

    // constructor
    constructor(address stakingtoken, address rewardingtoken) {
        // stakingtoken: staking token address (SATs)
        // rewardtoken: reward token address (WBTC)

        // get IERC20 stakeToken
        stakeToken = IERC20(stakingtoken);
        // get IERC20 rewardToken
        rewardToken = IERC20(rewardingtoken);
        // available maximum amount of stakeToken
        maxStakeableToken = stakeToken.totalSupply();
        // available minimum amount of stakeToken
        minimumStakeToken = 0;
        // percent divider: proportion
        percentDivider = 1e2;
    }

    // stake function
    function stake(uint256 amount) public {
        require(amount >= minimumStakeToken, "stake more than minimum amount");

        // insert stakers to list
        if (!Stakers[msg.sender].alreadyExists) {
            Stakers[msg.sender].alreadyExists = true;
            StakersID[totalStakers] = msg.sender;
            totalStakers++;
        }

        // transfer stakeToken (SATs) to smart contract
        stakeToken.transferFrom(msg.sender, address(this), amount);

        // get stakeCount of staker
        uint256 index = Stakers[msg.sender].stakeCount;
        // add amount to totalStakedTokenUser of staker
        Stakers[msg.sender].totalStakedTokenUser = Stakers[msg.sender]
            .totalStakedTokenUser
            .add(amount);

        // add amount to totalStakedToken => smart contract totalStakedToken
        totalStakedToken = totalStakedToken.add(amount);

        // create new record with staketime as block.timestamp
        stakersRecord[msg.sender][index].staketime = block.timestamp;
        // set unstake time of new record
        stakersRecord[msg.sender][index].unstaketime = block.timestamp.add(
            Duration
        );
        // set amount => staking amount
        stakersRecord[msg.sender][index].amount = amount;
        // set reward => claiming reward
        // amount * Bonus / percentDivider
        // percentDivider is constant
        stakersRecord[msg.sender][index].reward = GetRewardOf(amount);

        stakersRecord[msg.sender][index].availableUnstakedAmount = amount;
        stakersRecord[msg.sender][index].availableUnclaimedReward = GetRewardOf(
            amount
        );

        stakersRecord[msg.sender][index].unstaked = false;
        stakersRecord[msg.sender][index].withdrawn = false;

        // increase stakeCount of User => User[stakeCount] ++
        Stakers[msg.sender].stakeCount++;

        // emite STAKE
        emit STAKE(msg.sender, amount);
    }

    // unstake function
    function unstake(uint256 amount) public {
        // check the index of stake token that unstaked before
        // require(
        //     amount > GetMaxUnstakeAmount(),
        //     "amount must be less than available max unstake amount"
        // );

        uint256 sendAmount = amount;

        for (uint256 index; index < Stakers[msg.sender].stakeCount; index++) {
            if (stakersRecord[msg.sender][index].unstaked || amount == 0) {
                continue;
            }
            if (
                stakersRecord[msg.sender][index].unstaketime >= block.timestamp
            ) {
                continue;
            }
            if (
                stakersRecord[msg.sender][index].availableUnstakedAmount >
                amount
            ) {
                stakersRecord[msg.sender][index].availableUnstakedAmount =
                    stakersRecord[msg.sender][index].availableUnstakedAmount -
                    amount;
                amount = 0;
            } else {
                amount =
                    amount -
                    stakersRecord[msg.sender][index].availableUnstakedAmount;
                stakersRecord[msg.sender][index].availableUnstakedAmount = 0;
                stakersRecord[msg.sender][index].unstaked = true;
            }
        }

        // transfer stakeToken to staker => from smart contract to staker
        stakeToken.transfer(msg.sender, sendAmount);

        // add totalUnStakedToken amount
        totalUnStakedToken = totalUnStakedToken.add(sendAmount);
        // add totalUnstakedTokenUser of Staker amount
        Stakers[msg.sender].totalUnstakedTokenUser = Stakers[msg.sender]
            .totalUnstakedTokenUser
            .add(sendAmount);

        // emit UNSTAKE
        emit UNSTAKE(msg.sender, sendAmount);
    }

    // claim function
    function claim(uint256 amount) public {
        // check the index of stake token that unstaked before
        // require(
        //     amount > GetMaxUnclaimedAmount(),
        //     "amount must be less than available max unclaimed amount"
        // );

        uint256 sendReward = amount;

        for (uint256 index; index < Stakers[msg.sender].stakeCount; index++) {
            if (stakersRecord[msg.sender][index].withdrawn || amount == 0) {
                continue;
            }
            if (
                stakersRecord[msg.sender][index].unstaketime >= block.timestamp
            ) {
                continue;
            }
            if (
                stakersRecord[msg.sender][index].availableUnclaimedReward >
                amount
            ) {
                stakersRecord[msg.sender][index].availableUnclaimedReward =
                    stakersRecord[msg.sender][index].availableUnclaimedReward -
                    amount;
                amount = 0;
            } else {
                amount =
                    amount -
                    stakersRecord[msg.sender][index].availableUnclaimedReward;
                stakersRecord[msg.sender][index].availableUnclaimedReward = 0;
                stakersRecord[msg.sender][index].withdrawn = true;
            }
        }

        // give rewardToken to staker => send rewardToken from smart contrac to staker
        rewardToken.transfer(msg.sender, sendReward);
        // add totalRewardToken amount
        totalClaimedRewardToken = totalClaimedRewardToken.add(sendReward);
        // add totalClaimUser of Staker amount
        Stakers[msg.sender].totalClaimedRewardTokenUser = Stakers[msg.sender]
            .totalClaimedRewardTokenUser
            .add(sendReward);

        // emit CLAIM
        emit CLAIM(msg.sender, sendReward);
    }

    // SetStakeLimits with min value and max value
    function SetStakeLimits(uint256 _min, uint256 _max) external onlyOwner {
        minimumStakeToken = _min;
        maxStakeableToken = _max;
    }

    // set StakeDuration
    function SetStakeDuration(uint256 newDuration) external onlyOwner {
        Duration = newDuration;
    }

    // set StakeBonus
    function SetStakeBonus(uint256 newBonus) external onlyOwner {
        Bonus = newBonus;
    }

    // set PercentDivider
    function SetPercentDivider(uint256 newPercentDivider) external onlyOwner {
        percentDivider = newPercentDivider;
    }

    // get StakeToken balance
    function GetStakeTokenBalanceOf(address account)
        public
        view
        returns (uint256)
    {
        uint256 stakeTokenBalance = stakeToken.balanceOf(account);
        return stakeTokenBalance;
    }

    // get RewardToken balance
    function GetRewardTokenBalanceOf(address account)
        public
        view
        returns (uint256)
    {
        uint256 rewardTokenBalance = rewardToken.balanceOf(account);
        return rewardTokenBalance;
    }

    // get Staking List of Staker
    function GetStakingListOf(address user)
        public
        view
        returns (Stake[] memory)
    {
        uint256 stakeCount = Stakers[user].stakeCount;
        Stake[] memory stakingList = new Stake[](stakeCount);
        for (uint256 i = 0; i < stakeCount; i++) {
            Stake storage staking = stakersRecord[user][i];
            stakingList[i] = staking;
        }
        return stakingList;
    }

    // get Staking List of Staker
    function GetRewardOf(uint256 amount) public view returns (uint256 reward) {
        return amount.div(totalStakedToken).mul(1e2).mul(1e9);
    }

    // get Available Unstake Token Amount
    function GetMaxUnstakeAmount(address user)
        public
        view
        returns (uint256 reward)
    {
        uint256 maxUnstakeAmount;
        for (uint256 index; index < Stakers[user].stakeCount; index++) {
            if (!stakersRecord[user][index].unstaked) {
                if (stakersRecord[user][index].unstaketime < block.timestamp) {
                    maxUnstakeAmount = maxUnstakeAmount.add(
                        stakersRecord[user][index].availableUnstakedAmount
                    );
                }
            }
        }
        return maxUnstakeAmount;
    }

    // get Available Unstake Token Amount
    function GetMaxUnclaimedAmount(address user)
        public
        view
        returns (uint256 reward)
    {
        uint256 maxUnclaimedReward;
        for (uint256 index; index < Stakers[user].stakeCount; index++) {
            if (!stakersRecord[user][index].withdrawn) {
                if (stakersRecord[user][index].unstaketime < block.timestamp) {
                    maxUnclaimedReward = maxUnclaimedReward.add(
                        stakersRecord[user][index].availableUnclaimedReward
                    );
                }
            }
        }
        return maxUnclaimedReward;
    }

    function GetTimestamp() public view returns (uint256 time) {
        return block.timestamp;
    }
}