// SPDX-License-Identifier: MIT

pragma solidity ^0.7.6;

/**
 * @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 `recipient`.
  *
  * Returns a boolean value indicating whether the operation succeeded.
  *
  * Emits a {Transfer} event.
  */
  function transfer(address recipient, 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 `sender` to `recipient` 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 sender,
    address recipient,
    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 contracts/interfaces/IRBAC.sol

abstract contract ReentrancyGuard {
    // Booleans are more expensive than uint256 or any type that takes up a full
    // word because each write operation emits an extra SLOAD to first read the
    // slot's contents, replace the bits taken up by the boolean, and then write
    // back. This is the compiler's defense against contract upgrades and
    // pointer aliasing, and it cannot be disabled.

    // The values being non-zero value makes deployment a bit more expensive,
    // but in exchange the refund on every call to nonReentrant will be lower in
    // amount. Since refunds are capped to a percentage of the total
    // transaction's gas, it is best to keep them low in cases like this one, to
    // increase the likelihood of the full refund coming into effect.
    uint256 private constant _NOT_ENTERED = 1;
    uint256 private constant _ENTERED = 2;

    uint256 private _status;

    constructor () {
        _status = _NOT_ENTERED;
    }

    /**
     * @dev Prevents a contract from calling itself, directly or indirectly.
     * Calling a `nonReentrant` function from another `nonReentrant`
     * function is not supported. It is possible to prevent this from happening
     * by making the `nonReentrant` function external, and make it call a
     * `private` function that does the actual work.
     */
    modifier nonReentrant() {
        // On the first call to nonReentrant, _notEntered will be true
        require(_status != _ENTERED, "ReentrancyGuard: reentrant call");

        // Any calls to nonReentrant after this point will fail
        _status = _ENTERED;

        _;

        // By storing the original value once again, a refund is triggered (see
        // https://eips.ethereum.org/EIPS/eip-2200)
        _status = _NOT_ENTERED;
    }
}

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) {
        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
        // for accounts without code, i.e. `keccak256('')`
        bytes32 codehash;
        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
        // solhint-disable-next-line no-inline-assembly
        assembly { codehash := extcodehash(account) }
        return (codehash != accountHash && codehash != 0x0);
    }

    /**
     * @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");

        // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
        (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");
        return _functionCallWithValue(target, data, value, errorMessage);
    }

    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
        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

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}


abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

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 () {
        address msgSender = _msgSender();
        _owner = msgSender;
        emit OwnershipTransferred(address(0), 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 {
        emit OwnershipTransferred(_owner, address(0));
        _owner = 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");
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}

contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;
    using Address for address;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint8 private _decimals;

    /**
     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with
     * a default value of 18.
     *
     * To select a different value for {decimals}, use {_setupDecimals}.
     *
     * All three of these values are immutable: they can only be set once during
     * construction.
     */
    constructor (string memory name, string memory symbol) public {
        _name = name;
        _symbol = symbol;
        _decimals = 18;
    }

    /**
     * @dev Returns the name of the token.
     */
    function name() public view returns (string memory) {
        return _name;
    }

    /**
     * @dev Returns the symbol of the token, usually a shorter version of the
     * name.
     */
    function symbol() public view 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 {_setupDecimals} is
     * called.
     *
     * 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 returns (uint8) {
        return _decimals;
    }

    /**
     * @dev See {IERC20-totalSupply}.
     */
    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }

    /**
     * @dev See {IERC20-balanceOf}.
     */
    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }

    /**
     * @dev See {IERC20-transfer}.
     *
     * Requirements:
     *
     * - `recipient` cannot be the zero address.
     * - the caller must have a balance of at least `amount`.
     */
    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, 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}.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     */
    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), 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};
     *
     * Requirements:
     * - `sender` and `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     * - the caller must have allowance for ``sender``'s tokens of at least
     * `amount`.
     */
    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
        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) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(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) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    /**
     * @dev Moves tokens `amount` from `sender` to `recipient`.
     *
     * This is 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:
     *
     * - `sender` cannot be the zero address.
     * - `recipient` cannot be the zero address.
     * - `sender` must have a balance of at least `amount`.
     */
    function _transfer(address sender, address recipient, uint256 amount) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        _beforeTokenTransfer(sender, recipient, amount);

        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(amount);
        emit Transfer(sender, recipient, 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
     *
     * - `to` 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 = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(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);

        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    /**
     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.
     *
     * This is 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 Sets {decimals} to a value other than the default one of 18.
     *
     * WARNING: This function should only be called from the constructor. Most
     * applications that interact with token contracts will not expect
     * {decimals} to ever change, and may work incorrectly if it does.
     */
    function _setupDecimals(uint8 decimals_) internal {
        _decimals = decimals_;
    }

    /**
     * @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 to 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 { }
}

interface IRBAC {
  function isAdmin(address user) external view returns (bool);
}

// File contracts/libraries/SafeMath.sol

pragma solidity >=0.6.0 <0.8.0;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
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) {
    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) {
    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) {
    // 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) {
    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) {
    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) {
    uint256 c = a + b;
    require(c >= a, "SafeMath: addition overflow");
    return c;
  }

  /**
   * @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) {
    require(b <= a, "SafeMath: subtraction overflow");
    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) {
    if (a == 0) return 0;
    uint256 c = a * b;
    require(c / a == b, "SafeMath: multiplication overflow");
    return c;
  }

  /**
   * @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. 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) internal pure returns (uint256) {
    require(b > 0, "SafeMath: division by zero");
    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) {
    require(b > 0, "SafeMath: modulo by zero");
    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) {
    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.
   *
   * CAUTION: This function is deprecated because it requires allocating memory for the error
   * message unnecessarily. For custom revert reasons use {tryDiv}.
   *
   * 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) {
    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) {
    require(b > 0, errorMessage);
    return a % b;
  }
}

pragma solidity ^0.7.6;

contract KwikswapStaking is ReentrancyGuard, Ownable, ERC20("Kwikswap X", "KWIK-X") {
    
  // Using SafeMath library for mathematical operations over uint256
  using SafeMath for uint256;

  /// Representing stake structure
  struct Stake {
    address user;
    uint256 amountStaked;
    uint256 stakingTime;
    uint256 unlockingTime;
    uint256 userReward;
    uint256 withdrawReward;
    uint256 pendingReward;
    bool isWithdrawn;
  }
  
  // Pointer to admin contract
  IRBAC public admin;

  // Array holding all stakes
  Stake[] public stakes;
  
  // Registeration Days StakingPool
  uint256 public registerationDays;

  // Token being staked
  IERC20 public token;
  
    // Token being rewarded
  IERC20 public rewardToken;

  // Mapping user to his stakes
  mapping(address => Stake) public userToHisStakeIds;

  // Total amount staked at the moment
  uint256 public totalStaked;
  
  // Total amount staked at the moment
  uint256 public APY = 12;
  
  uint public userStaked;
  
  uint256 public oneYear = 365 ;
  
  uint public oneDay = 1 days;

  // Minimal time to stake in order to get eligible to participate in private sales
  uint256 public minimalTimeToStake;

  // Minimal amount staked
  uint256 public minimalAmountToStake;


  // Initially set token address and admin wallet address
  constructor(address _token, address _admin, address _rewardToken) {
    token = IERC20(_token);
    admin = IRBAC(_admin);
    rewardToken = IERC20(_rewardToken);
  }
    
     
  // Function which can be called only by admin
  function setStakingRules(
    uint256 _minimalTimeToStake,
    uint256 _minimalAmountToStake
  ) onlyOwner public {
    // Only admin can call this
    
    // Set minimal time to stake
    minimalTimeToStake = _minimalTimeToStake;
    // Set minimal amount to stake
    minimalAmountToStake = _minimalAmountToStake;
  }
  
  function updateAdmin(address _admin)public onlyOwner {
      admin = IRBAC(_admin);
  }
  
  function updateAPY(uint _APY) public onlyOwner returns(bool) {
      APY = _APY;
      return true;
  }
  
    // Function to deposit tokens (create stake)
  function depositTokens(uint256 amount) public {
    
    // Require that user is meeting requirement for minimal stake amount
    require(amount >= minimalAmountToStake);
    
    // Allow only direct calls from EOA (Externally owner wallets - flashloan prevention)
    require(msg.sender == tx.origin);
    
    // Compute the ID of the stake
    // uint256 stakeId = userToHisStakeIds[msg.sender];
    if(msg.sender == userToHisStakeIds[msg.sender].user ){
           userToHisStakeIds[msg.sender].amountStaked = userToHisStakeIds[msg.sender].amountStaked + amount;
           userToHisStakeIds[msg.sender].unlockingTime = block.timestamp.add(minimalTimeToStake);
           
           if(calculateReward(msg.sender)>= 0){
               claimReward(msg.sender);
               userToHisStakeIds[msg.sender].stakingTime = block.timestamp;
               userToHisStakeIds[msg.sender].withdrawReward = 0;
           }
    }
    else{
    
    // Create new stake object
    Stake storage s = userToHisStakeIds[msg.sender];
    s.user = msg.sender;
    s.amountStaked= amount;
    s.stakingTime = block.timestamp;
    s.unlockingTime = block.timestamp.add(minimalTimeToStake);
    s.userReward= 0;
    s.withdrawReward=0;
    s.isWithdrawn= false;
      
    // Push stake to array of all stakes
    stakes.push(s);
    }

    // Take tokens from the user
    token.transferFrom(msg.sender, address(this), amount);
    
    // Increase how much is staked in total
    totalStaked = totalStaked.add(amount);
    userStaked++;
  }
  
    //function for calculating total reward
  function calculateReward(address _user) public view returns (uint256) {
    require(userToHisStakeIds[msg.sender].amountStaked >= 0, "No stake found");
        Stake memory s = userToHisStakeIds[_user];
        uint256 stakingDays =  (block.timestamp-s.stakingTime).div(oneDay);
        uint256 rewardPerDay = ((s.amountStaked.mul(APY)).div(oneYear)).div(100);
        uint256 rewardAmount = ((rewardPerDay.mul(stakingDays)).sub(s.withdrawReward));
    return rewardAmount;
  }
  
  function getTotalRewardEarned() public view returns(uint){
        Stake memory s = userToHisStakeIds[msg.sender];
    return s.userReward;
  }
    

  function claimReward(address _user) public {
      require(msg.sender == _user);
      uint256 amountToWithdraw = calculateReward(_user);
      _mint(_user, amountToWithdraw);
      Stake storage s = userToHisStakeIds[_user];
      s.withdrawReward = s.withdrawReward + amountToWithdraw;
      s.userReward = s.userReward + amountToWithdraw;
  }

  
  function withdrawStakeInternal(address _user) internal returns (uint256) {
    Stake storage s = userToHisStakeIds[_user];
    
    // Only user can withdraw his stakes
    require(s.user == _user);
    
    // Stake can't be withdrawn more than once and time has to expire in order to make stake able to withdraw
    if (s.isWithdrawn == true || block.timestamp < s.unlockingTime) {
      return 0;
    } 
    
    else {
      // Mark stake that it's withdrawn
      s.isWithdrawn = true;
      
      // Reduce total amount staked
      totalStaked = totalStaked.sub(s.amountStaked);
      
      // Transfer back tokens to user
      return s.amountStaked;
    }
  }

    
    function withdrawStake() public returns(bool){
    uint256 amount = withdrawStakeInternal(msg.sender);
    require(amount > 0);
    token.transfer(msg.sender, amount);
    
    if(calculateReward(msg.sender)>= 0){
        claimReward(msg.sender);
        delete userToHisStakeIds[msg.sender];
    }
    userStaked--;
    return true;
    
  }
  
  
  //function to update the Registeration days
  function updateRegisterationDays(uint256 _daysTime) onlyOwner public returns(uint256){
       registerationDays = _daysTime;
       return registerationDays;
  }

  function register(address _user) public returns(uint256){
      Stake storage s = userToHisStakeIds[_user];
      s.unlockingTime = s.unlockingTime.add(registerationDays);
      return s.unlockingTime;
  }
  
}