// File: contracts/Lfi.sol



// SPDX-License-Identifier: GPLv3
pragma solidity ^0.7.6;

import "./libraries/AddressArray.sol";
import "./interfaces/ILfi.sol";
import "./Reflect.sol";

contract Lfi is Reflect, ILfi {
    using AddressArray for address[];

    uint256 public immutable teamPreMinted;
    address public immutable teamAccount;

    address public governanceAccount;
    uint256 public cap;

    address[] private _treasuryPoolAddresses;

    constructor(
        string memory name_,
        string memory symbol_,
        uint256 cap_,
        uint8 feePercentage_,
        uint256 teamPreMinted_,
        address teamAccount_
    )
        Reflect(
            name_,
            symbol_,
            cap_,
            feePercentage_,
            teamPreMinted_,
            teamAccount_
        )
    {
        require(
            teamAccount_ != address(0),
            "LFI: team account is the zero address"
        );

        governanceAccount = msg.sender;
        cap = cap_;
        teamPreMinted = teamPreMinted_;
        teamAccount = teamAccount_;
    }

    modifier onlyBy(address account) {
        require(msg.sender == account, "LFI: sender not authorized");
        _;
    }

    modifier onlyTreasuryPool() {
        require(
            _treasuryPoolAddresses.contains(msg.sender),
            "LFI: sender not a treasury pool"
        );
        _;
    }

    function treasuryPoolAddresses() external view returns (address[] memory) {
        return _treasuryPoolAddresses;
    }

    function redeem(address to, uint256 amount)
        external
        override
        onlyTreasuryPool()
    {
        require(to != address(0), "LFI: redeem to the zero address");
        require(amount > 0, "LFI: redeem 0");

        _transfer(address(this), to, amount);
    }

    function setGovernanceAccount(address newGovernanceAccount)
        external
        onlyBy(governanceAccount)
    {
        require(
            newGovernanceAccount != address(0),
            "LFI: new governance account is the zero address"
        );

        governanceAccount = newGovernanceAccount;
    }

    function addTreasuryPoolAddress(address address_)
        external
        onlyBy(governanceAccount)
    {
        require(address_ != address(0), "LFI: address is the zero address");
        require(
            !_treasuryPoolAddresses.contains(address_),
            "LFI: address is already a treasury pool"
        );

        _treasuryPoolAddresses.push(address_);
    }

    function removeTreasuryPoolAddress(address address_)
        external
        onlyBy(governanceAccount)
    {
        require(address_ != address(0), "LFI: address is the zero address");

        uint256 index = _treasuryPoolAddresses.indexOf(address_);
        require(index > 0, "LFI: address not an existing treasury pool");

        _treasuryPoolAddresses.removeAt(index);
    }
}

// File: contracts/libraries/AddressArray.sol



// SPDX-License-Identifier: Apache-2.0

pragma solidity ^0.7.6;

library AddressArray {
    /**
     * Searches for the specified element and returns the one-based index of the first occurrence within the entire array.
     * @param array The array to search.
     * @param element The element to locate in the array.
     * @return The one-based index of the first occurrence of item within the entire arry, if found; otherwise, 0.
     */
    function indexOf(address[] storage array, address element)
        internal
        view
        returns (uint256)
    {
        uint256 length = array.length;
        for (uint256 i = 0; i < length; i++) {
            if (array[i] == element) {
                return i + 1;
            }
        }
        return 0;
    }

    /**
     * Determines whether an element is in the array.
     * @param array The array to search.
     * @param element The element to locate in the array.
     * @return true if item is found in the array; otherwise, false.
     */
    function contains(address[] storage array, address element)
        internal
        view
        returns (bool)
    {
        uint256 index = indexOf(array, element);
        return index > 0;
    }

    /**
     * Removes the element at the specified index of the array.
     * @param array The array to search.
     * @param index The one-based index of the element to remove.
     */
    function removeAt(address[] storage array, uint256 index) internal {
        require(index > 0, "AddressArray: index is one-based");

        uint256 length = array.length;
        require(index <= length, "AddressArray: index is greater than length");

        array[index - 1] = array[length - 1];
        array.pop();
    }
}

// File: contracts/interfaces/ILfi.sol



// SPDX-License-Identifier: Apache-2.0
pragma solidity ^0.7.6;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

interface ILfi is IERC20 {
    function redeem(address to, uint256 amount) external;
}

// File: contracts/Reflect.sol



// SPDX-License-Identifier: GPLv3
pragma solidity ^0.7.6;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/math/SafeMath.sol";
import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract Reflect is Context, IERC20, Ownable {
    using SafeMath for uint256;
    using Address for address;

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

    mapping(address => bool) private _isExcluded;
    address[] private _excluded;

    uint8 private constant DECIMALS = 18;
    uint256 private constant MAX = type(uint256).max;
    uint256 private _tTotal;
    uint256 private _rTotal;
    uint256 private _tFeeTotal;

    string private _name;
    string private _symbol;
    uint8 private _feePercentage;

    constructor(
        string memory name_,
        string memory symbol_,
        uint256 tTotal_,
        uint8 feePercentage_,
        uint256 teamPreMinted_,
        address teamAccount_
    ) {
        require(tTotal_ > 0, "tTotal is 0");
        require(feePercentage_ < 100, "fee >= 100%");

        _name = name_;
        _symbol = symbol_;
        _feePercentage = feePercentage_;

        _tTotal = tTotal_;
        _rTotal = (MAX - (MAX % tTotal_));

        // https://github.com/crytic/slither/wiki/Detector-Documentation#divide-before-multiply
        // slither-disable-next-line divide-before-multiply
        _rOwned[teamAccount_] = _rTotal.div(tTotal_).mul(teamPreMinted_); // rTotal/(tTotal/teamPreMinted)
        _rOwned[address(this)] = _rTotal.sub(_rOwned[teamAccount_]);
        _excludeAccount(address(this));
    }

    // https://github.com/crytic/slither/wiki/Detector-Documentation#state-variables-that-could-be-declared-constant
    // slither-disable-next-line external-function
    function name() public view returns (string memory) {
        return _name;
    }

    // https://github.com/crytic/slither/wiki/Detector-Documentation#state-variables-that-could-be-declared-constant
    // slither-disable-next-line external-function
    function symbol() public view returns (string memory) {
        return _symbol;
    }

    // https://github.com/crytic/slither/wiki/Detector-Documentation#state-variables-that-could-be-declared-constant
    // slither-disable-next-line external-function
    function decimals() public pure returns (uint8) {
        return DECIMALS;
    }

    function totalSupply() public view override returns (uint256) {
        return _tTotal;
    }

    function balanceOf(address account) public view override returns (uint256) {
        if (_isExcluded[account]) return _tOwned[account];
        return tokenFromReflection(_rOwned[account]);
    }

    function transfer(address recipient, uint256 amount)
        public
        override
        returns (bool)
    {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    function allowance(address owner, address spender)
        public
        view
        override
        returns (uint256)
    {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint256 amount)
        public
        override
        returns (bool)
    {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) public override returns (bool) {
        _transfer(sender, recipient, amount);
        _approve(
            sender,
            _msgSender(),
            _allowances[sender][_msgSender()].sub(
                amount,
                "ERC20: transfer amount exceeds allowance"
            )
        );
        return true;
    }

    // https://github.com/crytic/slither/wiki/Detector-Documentation#state-variables-that-could-be-declared-constant
    // slither-disable-next-line external-function
    function increaseAllowance(address spender, uint256 addedValue)
        public
        virtual
        returns (bool)
    {
        _approve(
            _msgSender(),
            spender,
            _allowances[_msgSender()][spender].add(addedValue)
        );
        return true;
    }

    // https://github.com/crytic/slither/wiki/Detector-Documentation#state-variables-that-could-be-declared-constant
    // slither-disable-next-line external-function
    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;
    }

    function isExcluded(address account) external view returns (bool) {
        return _isExcluded[account];
    }

    function totalFees() external view returns (uint256) {
        return _tFeeTotal;
    }

    function reflect(uint256 tAmount) external {
        address sender = _msgSender();
        require(
            !_isExcluded[sender],
            "Excluded addresses cannot call this function"
        );
        (uint256 rAmount, , , , ) = _getValues(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _rTotal = _rTotal.sub(rAmount);
        _tFeeTotal = _tFeeTotal.add(tAmount);
    }

    function reflectionFromToken(uint256 tAmount, bool deductTransferFee)
        external
        view
        returns (uint256)
    {
        require(tAmount <= _tTotal, "Amount must be less than supply");
        if (!deductTransferFee) {
            (uint256 rAmount, , , , ) = _getValues(tAmount);
            return rAmount;
        } else {
            (, uint256 rTransferAmount, , , ) = _getValues(tAmount);
            return rTransferAmount;
        }
    }

    function tokenFromReflection(uint256 rAmount)
        public
        view
        returns (uint256)
    {
        require(
            rAmount <= _rTotal,
            "Amount must be less than total reflections"
        );
        uint256 currentRate = _getRate();
        return rAmount.div(currentRate);
    }

    function excludeAccount(address account) external onlyOwner() {
        _excludeAccount(account);
    }

    function includeAccount(address account) external onlyOwner() {
        _includeAccount(account);
    }

    function feePercentage() external view returns (uint8) {
        return _feePercentage;
    }

    function excludedAccounts() external view returns (address[] memory) {
        return _excluded;
    }

    function tOwned(address account) external view returns (uint256) {
        return _tOwned[account];
    }

    function rOwned(address account) external view returns (uint256) {
        return _rOwned[account];
    }

    function rTotal() external view returns (uint256) {
        return _rTotal;
    }

    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal {
        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);
    }

    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");
        require(amount > 0, "Transfer amount must be greater than zero");
        if (_isExcluded[sender] && !_isExcluded[recipient]) {
            _transferFromExcluded(sender, recipient, amount);
        } else if (!_isExcluded[sender] && _isExcluded[recipient]) {
            _transferToExcluded(sender, recipient, amount);
        } else if (!_isExcluded[sender] && !_isExcluded[recipient]) {
            _transferStandard(sender, recipient, amount);
        } else if (_isExcluded[sender] && _isExcluded[recipient]) {
            _transferBothExcluded(sender, recipient, amount);
        } else {
            _transferStandard(sender, recipient, amount);
        }
    }

    function _transferStandard(
        address sender,
        address recipient,
        uint256 tAmount
    ) private {
        (
            uint256 rAmount,
            uint256 rTransferAmount,
            uint256 rFee,
            uint256 tTransferAmount,
            uint256 tFee
        ) = _getValues(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function _transferToExcluded(
        address sender,
        address recipient,
        uint256 tAmount
    ) private {
        (
            uint256 rAmount,
            uint256 rTransferAmount,
            uint256 rFee,
            uint256 tTransferAmount,
            uint256 tFee
        ) = _getValues(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _tOwned[recipient] = _tOwned[recipient].add(tTransferAmount);
        _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function _transferFromExcluded(
        address sender,
        address recipient,
        uint256 tAmount
    ) private {
        (
            uint256 rAmount,
            uint256 rTransferAmount,
            uint256 rFee,
            uint256 tTransferAmount,
            uint256 tFee
        ) = _getValues(tAmount);
        _tOwned[sender] = _tOwned[sender].sub(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function _transferBothExcluded(
        address sender,
        address recipient,
        uint256 tAmount
    ) private {
        (
            uint256 rAmount,
            uint256 rTransferAmount,
            uint256 rFee,
            uint256 tTransferAmount,
            uint256 tFee
        ) = _getValues(tAmount);
        _tOwned[sender] = _tOwned[sender].sub(tAmount);
        _rOwned[sender] = _rOwned[sender].sub(rAmount);
        _tOwned[recipient] = _tOwned[recipient].add(tTransferAmount);
        _rOwned[recipient] = _rOwned[recipient].add(rTransferAmount);
        _reflectFee(rFee, tFee);
        emit Transfer(sender, recipient, tTransferAmount);
    }

    function _reflectFee(uint256 rFee, uint256 tFee) private {
        _rTotal = _rTotal.sub(rFee);
        _tFeeTotal = _tFeeTotal.add(tFee);
    }

    function _getValues(uint256 tAmount)
        private
        view
        returns (
            uint256,
            uint256,
            uint256,
            uint256,
            uint256
        )
    {
        (uint256 tTransferAmount, uint256 tFee) = _getTValues(tAmount);
        uint256 currentRate = _getRate();
        (uint256 rAmount, uint256 rTransferAmount, uint256 rFee) =
            _getRValues(tAmount, tFee, currentRate);
        return (rAmount, rTransferAmount, rFee, tTransferAmount, tFee);
    }

    function _getTValues(uint256 tAmount)
        private
        view
        returns (uint256, uint256)
    {
        uint256 tFee = tAmount.mul(_feePercentage).div(100);
        uint256 tTransferAmount = tAmount.sub(tFee);
        return (tTransferAmount, tFee);
    }

    function _getRValues(
        uint256 tAmount,
        uint256 tFee,
        uint256 currentRate
    )
        private
        pure
        returns (
            uint256,
            uint256,
            uint256
        )
    {
        uint256 rAmount = tAmount.mul(currentRate);
        uint256 rFee = tFee.mul(currentRate);
        uint256 rTransferAmount = rAmount.sub(rFee);
        return (rAmount, rTransferAmount, rFee);
    }

    function _getRate() private view returns (uint256) {
        (uint256 rSupply, uint256 tSupply) = _getCurrentSupply();
        return rSupply.div(tSupply);
    }

    function _getCurrentSupply() private view returns (uint256, uint256) {
        uint256 rSupply = _rTotal;
        uint256 tSupply = _tTotal;
        for (uint256 i = 0; i < _excluded.length; i++) {
            if (
                _rOwned[_excluded[i]] > rSupply ||
                _tOwned[_excluded[i]] > tSupply
            ) return (_rTotal, _tTotal);
            rSupply = rSupply.sub(_rOwned[_excluded[i]]);
            tSupply = tSupply.sub(_tOwned[_excluded[i]]);
        }
        if (rSupply < _rTotal.div(_tTotal)) return (_rTotal, _tTotal);
        return (rSupply, tSupply);
    }

    function _excludeAccount(address account) private {
        require(!_isExcluded[account], "Account is already excluded");
        if (_rOwned[account] > 0) {
            _tOwned[account] = tokenFromReflection(_rOwned[account]);
        }
        _isExcluded[account] = true;
        _excluded.push(account);
    }

    function _includeAccount(address account) private {
        require(_isExcluded[account], "Account is already excluded");
        for (uint256 i = 0; i < _excluded.length; i++) {
            if (_excluded[i] == account) {
                _excluded[i] = _excluded[_excluded.length - 1];
                _tOwned[account] = 0;
                _isExcluded[account] = false;
                _excluded.pop();
                break;
            }
        }
    }
}

// File: @openzeppelin/contracts/token/ERC20/IERC20.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <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 `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: @openzeppelin/contracts/math/SafeMath.sol



// SPDX-License-Identifier: MIT

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;
    }
}

// File: @openzeppelin/contracts/utils/Address.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.2 <0.8.0;

/**
 * @dev Collection of functions related to the address type
 */
library Address {
    /**
     * @dev Returns true if `account` is a contract.
     *
     * [IMPORTANT]
     * ====
     * It is unsafe to assume that an address for which this function returns
     * false is an externally-owned account (EOA) and not a contract.
     *
     * Among others, `isContract` will return false for the following
     * types of addresses:
     *
     *  - an externally-owned account
     *  - a contract in construction
     *  - an address where a contract will be created
     *  - an address where a contract lived, but was destroyed
     * ====
     */
    function isContract(address account) internal view returns (bool) {
        // This method relies on extcodesize, which returns 0 for contracts in
        // construction, since the code is only stored at the end of the
        // constructor execution.

        uint256 size;
        // solhint-disable-next-line no-inline-assembly
        assembly { size := extcodesize(account) }
        return size > 0;
    }

    /**
     * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
     * `recipient`, forwarding all available gas and reverting on errors.
     *
     * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
     * of certain opcodes, possibly making contracts go over the 2300 gas limit
     * imposed by `transfer`, making them unable to receive funds via
     * `transfer`. {sendValue} removes this limitation.
     *
     * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
     *
     * IMPORTANT: because control is transferred to `recipient`, care must be
     * taken to not create reentrancy vulnerabilities. Consider using
     * {ReentrancyGuard} or the
     * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
     */
    function sendValue(address payable recipient, uint256 amount) internal {
        require(address(this).balance >= amount, "Address: insufficient balance");

        // 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");
        require(isContract(target), "Address: call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.call{ value: value }(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory) {
        return functionStaticCall(target, data, "Address: low-level static call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a static call.
     *
     * _Available since v3.3._
     */
    function functionStaticCall(address target, bytes memory data, string memory errorMessage) internal view returns (bytes memory) {
        require(isContract(target), "Address: static call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.staticcall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory) {
        return functionDelegateCall(target, data, "Address: low-level delegate call failed");
    }

    /**
     * @dev Same as {xref-Address-functionCall-address-bytes-string-}[`functionCall`],
     * but performing a delegate call.
     *
     * _Available since v3.4._
     */
    function functionDelegateCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        require(isContract(target), "Address: delegate call to non-contract");

        // solhint-disable-next-line avoid-low-level-calls
        (bool success, bytes memory returndata) = target.delegatecall(data);
        return _verifyCallResult(success, returndata, errorMessage);
    }

    function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage) private pure returns(bytes memory) {
        if (success) {
            return returndata;
        } else {
            // Look for revert reason and bubble it up if present
            if (returndata.length > 0) {
                // The easiest way to bubble the revert reason is using memory via assembly

                // solhint-disable-next-line no-inline-assembly
                assembly {
                    let returndata_size := mload(returndata)
                    revert(add(32, returndata), returndata_size)
                }
            } else {
                revert(errorMessage);
            }
        }
    }
}

// File: @openzeppelin/contracts/utils/Context.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <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 GSN 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 payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
        return msg.data;
    }
}

// File: @openzeppelin/contracts/access/Ownable.sol



// SPDX-License-Identifier: MIT

pragma solidity >=0.6.0 <0.8.0;

import "../utils/Context.sol";
/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor () internal {
        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;
    }
}