/**
 *Submitted for verification at Etherscan.io on 2020-11-16
*/

pragma solidity ^0.6.2;


// SPDX-License-Identifier: MIT
/**
 * @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, 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) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    /**
     * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
     * overflow (when the result is negative).
     *
     * 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);
        uint256 c = a - b;

        return c;
    }

    /**
     * @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) {
        // 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 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts 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) {
        return div(a, b, "SafeMath: division by zero");
    }

    /**
     * @dev Returns the integer division of two unsigned integers. Reverts 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) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts 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 mod(a, b, "SafeMath: modulo by zero");
    }

    /**
     * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
     * Reverts with custom message 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, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

// SPDX-License-Identifier: MIT
/*
 * @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: contracts/GSN/Context.sol
// SPDX-License-Identifier: MIT
// File: contracts/token/ERC20/IERC20.sol
/**
 * @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/utils/Address.sol
/**
 * @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) {
        // 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);
            }
        }
    }
}

// File: contracts/token/ERC20/ERC20.sol
/**
 * @dev Implementation of the {IERC20} interface.
 *
 * This implementation is agnostic to the way tokens are created. This means
 * that a supply mechanism has to be added in a derived contract using {_mint}.
 * For a generic mechanism see {ERC20PresetMinterPauser}.
 *
 * TIP: For a detailed writeup see our guide
 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How
 * to implement supply mechanisms].
 *
 * We have followed general OpenZeppelin guidelines: functions revert instead
 * of 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 {
    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 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 { }
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(IERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
    }

    /**
     * @dev Deprecated. This function has issues similar to the ones found in
     * {IERC20-approve}, and its usage is discouraged.
     *
     * Whenever possible, use {safeIncreaseAllowance} and
     * {safeDecreaseAllowance} instead.
     */
    function safeApprove(IERC20 token, address spender, uint256 value) internal {
        // safeApprove should only be called when setting an initial allowance,
        // or when resetting it to zero. To increase and decrease it, use
        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
        // solhint-disable-next-line max-line-length
        require((value == 0) || (token.allowance(address(this), spender) == 0),
            "SafeERC20: approve from non-zero to non-zero allowance"
        );
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).add(value);
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
    }

    /**
     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
     * on the return value: the return value is optional (but if data is returned, it must not be false).
     * @param token The token targeted by the call.
     * @param data The call data (encoded using abi.encode or one of its variants).
     */
    function _callOptionalReturn(IERC20 token, bytes memory data) private {
        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
        // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
        // the target address contains contract code and also asserts for success in the low-level call.

        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
        if (returndata.length > 0) { // Return data is optional
            // solhint-disable-next-line max-line-length
            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
        }
    }
}

/**
  * @title Careful Math
  * @author Compound
  * @notice Derived from OpenZeppelin's SafeMath library
  *         https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/math/SafeMath.sol
  */
contract CarefulMath {

    /**
     * @dev Possible error codes that we can return
     */
    enum MathError {
        NO_ERROR,
        DIVISION_BY_ZERO,
        INTEGER_OVERFLOW,
        INTEGER_UNDERFLOW
    }

    /**
    * @dev Multiplies two numbers, returns an error on overflow.
    */
    function mulUInt(uint a, uint b) internal pure returns (MathError, uint) {
        if (a == 0) {
            return (MathError.NO_ERROR, 0);
        }

        uint c = a * b;

        if (c / a != b) {
            return (MathError.INTEGER_OVERFLOW, 0);
        } else {
            return (MathError.NO_ERROR, c);
        }
    }

    /**
    * @dev Integer division of two numbers, truncating the quotient.
    */
    function divUInt(uint a, uint b) internal pure returns (MathError, uint) {
        if (b == 0) {
            return (MathError.DIVISION_BY_ZERO, 0);
        }

        return (MathError.NO_ERROR, a / b);
    }
}

/**
 * @title Exponential module for storing fixed-precision decimals
 * @author Compound
 * @notice Exp is a struct which stores decimals with a fixed precision of 18 decimal places.
 *         Thus, if we wanted to store the 5.1, mantissa would store 5.1e18. That is:
 *         `Exp({mantissa: 5100000000000000000})`.
 */
contract Exponential is CarefulMath {
    uint constant expScale = 1e18;
    uint constant doubleScale = 1e36;
    uint constant halfExpScale = expScale/2;
    uint constant mantissaOne = expScale;

    struct Exp {
        uint mantissa;
    }

    struct Double {
        uint mantissa;
    }

    /**
     * @dev Multiply an Exp by a scalar, returning a new Exp.
     */
    function mulScalar(Exp memory a, uint scalar) pure internal returns (MathError, Exp memory) {
        (MathError err0, uint scaledMantissa) = mulUInt(a.mantissa, scalar);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        return (MathError.NO_ERROR, Exp({mantissa: scaledMantissa}));
    }

    /**
     * @dev Multiply an Exp by a scalar, then truncate to return an unsigned integer.
     */
    function mulScalarTruncate(Exp memory a, uint scalar) pure internal returns (MathError, uint) {
        (MathError err, Exp memory product) = mulScalar(a, scalar);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return (MathError.NO_ERROR, truncate(product));
    }
	
    /**
     * @dev Truncates the given exp to a whole number value.
     *      For example, truncate(Exp{mantissa: 15 * expScale}) = 15
     */
    function truncate(Exp memory exp) pure internal returns (uint) {
        // Note: We are not using careful math here as we're performing a division that cannot fail
        return exp.mantissa / expScale;
    }
}

// SPDX-License-Identifier: MIT
interface IVault is IERC20 {
    function token() external view returns (address);

    function claimInsurance() external; // NOTE: Only yDelegatedVault implements this

    function getRatio() external view returns (uint256);

    function deposit(uint256) external;

    function withdraw(uint256) external;

    function earn() external;
}

interface UniswapRouterV2 {
    function swapExactTokensForTokens(
        uint256 amountIn,
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external returns (uint256[] memory amounts);

    function addLiquidity(
        address tokenA,
        address tokenB,
        uint256 amountADesired,
        uint256 amountBDesired,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    )
        external
        returns (
            uint256 amountA,
            uint256 amountB,
            uint256 liquidity
        );

    function addLiquidityETH(
        address token,
        uint256 amountTokenDesired,
        uint256 amountTokenMin,
        uint256 amountETHMin,
        address to,
        uint256 deadline
    )
        external
        payable
        returns (
            uint256 amountToken,
            uint256 amountETH,
            uint256 liquidity
        );

    function removeLiquidity(
        address tokenA,
        address tokenB,
        uint256 liquidity,
        uint256 amountAMin,
        uint256 amountBMin,
        address to,
        uint256 deadline
    ) external returns (uint256 amountA, uint256 amountB);

    function getAmountsOut(uint256 amountIn, address[] calldata path)
        external
        view
        returns (uint256[] memory amounts);

    function getAmountsIn(uint256 amountOut, address[] calldata path)
        external
        view
        returns (uint256[] memory amounts);

    function swapETHForExactTokens(
        uint256 amountOut,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable returns (uint256[] memory amounts);

    function swapExactETHForTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable returns (uint256[] memory amounts);
}

interface IUniswapV2Pair {
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
    event Transfer(address indexed from, address indexed to, uint256 value);

    function name() external pure returns (string memory);

    function symbol() external pure returns (string memory);

    function decimals() external pure returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address owner) external view returns (uint256);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 value) external returns (bool);

    function transfer(address to, uint256 value) external returns (bool);

    function transferFrom(
        address from,
        address to,
        uint256 value
    ) external returns (bool);

    function DOMAIN_SEPARATOR() external view returns (bytes32);

    function PERMIT_TYPEHASH() external pure returns (bytes32);

    function nonces(address owner) external view returns (uint256);

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    event Mint(address indexed sender, uint256 amount0, uint256 amount1);
    event Burn(
        address indexed sender,
        uint256 amount0,
        uint256 amount1,
        address indexed to
    );
    event Swap(
        address indexed sender,
        uint256 amount0In,
        uint256 amount1In,
        uint256 amount0Out,
        uint256 amount1Out,
        address indexed to
    );
    event Sync(uint112 reserve0, uint112 reserve1);

    function MINIMUM_LIQUIDITY() external pure returns (uint256);

    function factory() external view returns (address);

    function token0() external view returns (address);

    function token1() external view returns (address);

    function getReserves()
        external
        view
        returns (
            uint112 reserve0,
            uint112 reserve1,
            uint32 blockTimestampLast
        );

    function price0CumulativeLast() external view returns (uint256);

    function price1CumulativeLast() external view returns (uint256);

    function kLast() external view returns (uint256);

    function mint(address to) external returns (uint256 liquidity);

    function burn(address to)
        external
        returns (uint256 amount0, uint256 amount1);

    function swap(
        uint256 amount0Out,
        uint256 amount1Out,
        address to,
        bytes calldata data
    ) external;

    function skim(address to) external;

    function sync() external;
}

interface IUniswapV2Factory {
    event PairCreated(
        address indexed token0,
        address indexed token1,
        address pair,
        uint256
    );

    function getPair(address tokenA, address tokenB)
        external
        view
        returns (address pair);

    function allPairs(uint256) external view returns (address pair);

    function allPairsLength() external view returns (uint256);

    function feeTo() external view returns (address);

    function feeToSetter() external view returns (address);

    function createPair(address tokenA, address tokenB)
        external
        returns (address pair);
}

// SPDX-License-Identifier: MIT
interface IController {
    function vaults(address) external view returns (address);

    function devfund() external view returns (address);

    function treasury() external view returns (address);
}

// SPDX-License-Identifier: MIT
interface IMasterchef {
    function notifyBuybackReward(uint256 _amount) external;
}

// Strategy Contract Basics
abstract contract StrategyBase {
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;

    // Perfomance fee 30% to buyback
    uint256 public performanceFee = 30000;
    uint256 public constant performanceMax = 100000;

    // Withdrawal fee 0.2% to buyback
    // - 0.14% to treasury
    // - 0.06% to dev fund
    uint256 public treasuryFee = 140;
    uint256 public constant treasuryMax = 100000;

    uint256 public devFundFee = 60;
    uint256 public constant devFundMax = 100000;

    // buyback ready
    bool public buybackEnabled = true;
    address public mmToken = 0xa283aA7CfBB27EF0cfBcb2493dD9F4330E0fd304;
    address public masterChef = 0xf8873a6080e8dbF41ADa900498DE0951074af577;
	
    // Tokens
    address public want;
    address public constant weth = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;

    // buyback coins
    address public constant usdcBuyback = 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48;
    address public wbtcBuyback = 0x2260FAC5E5542a773Aa44fBCfeDf7C193bc2C599;
    address public renbtcBuyback = 0xEB4C2781e4ebA804CE9a9803C67d0893436bB27D;

    // User accounts
    address public governance;
    address public controller;
    address public strategist;
    address public timelock;

    // Dex
    address public univ2Router2 = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D;

    constructor(
        address _want,
        address _governance,
        address _strategist,
        address _controller,
        address _timelock
    ) public {
        require(_want != address(0));
        require(_governance != address(0));
        require(_strategist != address(0));
        require(_controller != address(0));
        require(_timelock != address(0));

        want = _want;
        governance = _governance;
        strategist = _strategist;
        controller = _controller;
        timelock = _timelock;
    }

    // **** Modifiers **** //

    modifier onlyBenevolent {
        require(
            msg.sender == tx.origin ||
                msg.sender == governance ||
                msg.sender == strategist
        );
        _;
    }

    // **** Views **** //

    function balanceOfWant() public view returns (uint256) {
        return IERC20(want).balanceOf(address(this));
    }

    function balanceOfPool() public virtual view returns (uint256);

    function balanceOf() public view returns (uint256) {
        return balanceOfWant().add(balanceOfPool());
    }

    function getName() external virtual pure returns (string memory);

    // **** Setters **** //

    function setDevFundFee(uint256 _devFundFee) external {
        require(msg.sender == timelock, "!timelock");
        devFundFee = _devFundFee;
    }

    function setTreasuryFee(uint256 _treasuryFee) external {
        require(msg.sender == timelock, "!timelock");
        treasuryFee = _treasuryFee;
    }

    function setPerformanceFee(uint256 _performanceFee) external {
        require(msg.sender == timelock, "!timelock");
        performanceFee = _performanceFee;
    }

    function setStrategist(address _strategist) external {
        require(msg.sender == governance, "!governance");
        strategist = _strategist;
    }

    function setGovernance(address _governance) external {
        require(msg.sender == governance, "!governance");
        governance = _governance;
    }

    function setTimelock(address _timelock) external {
        require(msg.sender == timelock, "!timelock");
        timelock = _timelock;
    }

    function setController(address _controller) external {
        require(msg.sender == timelock, "!timelock");
        controller = _controller;
    }

    function setMmToken(address _mmToken) external {
        require(msg.sender == governance, "!governance");
        mmToken = _mmToken;
    }

    function setBuybackEnabled(bool _buybackEnabled) external {
        require(msg.sender == governance, "!governance");
        buybackEnabled = _buybackEnabled;
    }

    function setMasterChef(address _masterChef) external {
        require(msg.sender == governance, "!governance");
        masterChef = _masterChef;
    }

    // **** State mutations **** //
    function deposit() public virtual;

    // Controller only function for creating additional rewards from dust
    function withdraw(IERC20 _asset) external returns (uint256 balance) {
        require(msg.sender == controller, "!controller");
        require(want != address(_asset), "want");
        balance = _asset.balanceOf(address(this));
        _asset.safeTransfer(controller, balance);
    }

    // Withdraw partial funds, normally used with a vault withdrawal
    function withdraw(uint256 _amount) external {
        require(msg.sender == controller, "!controller");
        uint256 _balance = IERC20(want).balanceOf(address(this));
        if (_balance < _amount) {
            _amount = _withdrawSome(_amount.sub(_balance));
            _amount = _amount.add(_balance);
        }
				
        uint256 _feeDev = _amount.mul(devFundFee).div(devFundMax);
        uint256 _feeTreasury = _amount.mul(treasuryFee).div(treasuryMax);

        if (buybackEnabled == true) {            
            // we want buyback mm using LP token
            (address _buybackPrinciple, uint256 _buybackAmount) = _convertWantToBuyback(_feeDev.add(_feeTreasury));
            buybackAndNotify(_buybackPrinciple, _buybackAmount);			
        } else {
            IERC20(want).safeTransfer(IController(controller).devfund(), _feeDev);
            IERC20(want).safeTransfer(IController(controller).treasury(), _feeTreasury);
        }        

        address _vault = IController(controller).vaults(address(want));
        require(_vault != address(0), "!vault"); // additional protection so we don't burn the funds

        IERC20(want).safeTransfer(_vault, _amount.sub(_feeDev).sub(_feeTreasury));
    }
	
    // buyback MM and notify MasterChef
    function buybackAndNotify(address _buybackPrinciple, uint256 _buybackAmount) internal {
        if (buybackEnabled == true) {
            _swapUniswap(_buybackPrinciple, mmToken, _buybackAmount);
            uint256 _mmBought = IERC20(mmToken).balanceOf(address(this));
            IERC20(mmToken).safeTransfer(masterChef, _mmBought);
            IMasterchef(masterChef).notifyBuybackReward(_mmBought);
        }
    }

    // Withdraw all funds, normally used when migrating strategies
    function withdrawAll() external returns (uint256 balance) {
        require(msg.sender == controller, "!controller");
        _withdrawAll();

        balance = IERC20(want).balanceOf(address(this));

        address _vault = IController(controller).vaults(address(want));
        require(_vault != address(0), "!vault"); // additional protection so we don't burn the funds
        IERC20(want).safeTransfer(_vault, balance);
    }

    function _withdrawAll() internal {
        _withdrawSome(balanceOfPool());
    }

    function _withdrawSome(uint256 _amount) internal virtual returns (uint256);	
	
    // convert LP to buyback principle token
    function _convertWantToBuyback(uint256 _lpAmount) internal virtual returns (address, uint256);

    function harvest() public virtual;

    // **** Emergency functions ****

    // comment-out function execute(address _target, bytes memory _data)
    
    // **** Internal functions ****
    function _swapUniswap(
        address _from,
        address _to,
        uint256 _amount
    ) internal {
        require(_to != address(0));

        // Swap with uniswap
        IERC20(_from).safeApprove(univ2Router2, 0);
        IERC20(_from).safeApprove(univ2Router2, _amount);

        address[] memory path;

        if (_to == mmToken && buybackEnabled == true) {
            if (_from == usdcBuyback){
                path = new address[](2);
                path[0] = _from;
                path[1] = _to;			   
            }else{
                path = new address[](3);
                path[0] = _from;
                path[1] = usdcBuyback;
                path[2] = _to;
            }
        } else{		
            if (_from == weth || _to == weth) {
                path = new address[](2);
                path[0] = _from;
                path[1] = _to;
            } else {
                path = new address[](3);
                path[0] = _from;
                path[1] = weth;
                path[2] = _to;
            }		
        }

        UniswapRouterV2(univ2Router2).swapExactTokensForTokens(
            _amount,
            0,
            path,
            address(this),
            now.add(60)
        );
    }
}

// SPDX-License-Identifier: MIT
interface ICToken {
    function totalSupply() external view returns (uint256);

    function totalBorrows() external returns (uint256);

    function borrowIndex() external returns (uint256);

    function repayBorrow(uint256 repayAmount) external returns (uint256);

    function redeemUnderlying(uint256 redeemAmount) external returns (uint256);

    function borrow(uint256 borrowAmount) external returns (uint256);

    function mint(uint256 mintAmount) external returns (uint256);

    function transfer(address dst, uint256 amount) external returns (bool);

    function transferFrom(
        address src,
        address dst,
        uint256 amount
    ) external returns (bool);

    function approve(address spender, uint256 amount) external returns (bool);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function balanceOf(address owner) external view returns (uint256);

    function balanceOfUnderlying(address owner) external returns (uint256);

    function getAccountSnapshot(address account)
        external
        view
        returns (
            uint256,
            uint256,
            uint256,
            uint256
        );

    function borrowRatePerBlock() external view returns (uint256);

    function supplyRatePerBlock() external view returns (uint256);

    function totalBorrowsCurrent() external returns (uint256);

    function borrowBalanceCurrent(address account) external returns (uint256);

    function borrowBalanceStored(address account)
        external
        view
        returns (uint256);

    function exchangeRateCurrent() external returns (uint256);

    function exchangeRateStored() external view returns (uint256);

    function getCash() external view returns (uint256);

    function accrueInterest() external returns (uint256);

    function seize(
        address liquidator,
        address borrower,
        uint256 seizeTokens
    ) external returns (uint256);
}

interface IComptroller {
    /*** Assets You Are In ***/

    function enterMarkets(address[] calldata cTokens)
        external
        returns (uint256[] memory);

    // Claim all the COMP accrued by holder in all markets
    function claimComp(address holder) external;

    // Claim all the COMP accrued by holder in specific markets
    function claimComp(address holder, address[] calldata cTokens) external;

    // Claim all the COMP accrued by specific holders in specific markets for their supplies and/or borrows
    function claimComp(
        address[] calldata holders,
        address[] calldata cTokens,
        bool borrowers,
        bool suppliers
    ) external;

    function markets(address cTokenAddress)
        external
        view
        returns (bool, uint256);
}

interface ICompoundLens {
    function getCompBalanceMetadataExt(
        address comp,
        address comptroller,
        address account
    )
        external
        returns (
            uint256 balance,
            uint256 votes,
            address delegate,
            uint256 allocated
        );
}


abstract contract StrategyCmpdDaiBase is Exponential{
    using SafeERC20 for IERC20;
    using Address for address;
    using SafeMath for uint256;
	
    address public constant comptroller = 0x3d9819210A31b4961b30EF54bE2aeD79B9c9Cd3B;
    address public constant lens = 0xd513d22422a3062Bd342Ae374b4b9c20E0a9a074;
    address public constant dai = 0x6B175474E89094C44Da98b954EedeAC495271d0F;
    address public constant comp = 0xc00e94Cb662C3520282E6f5717214004A7f26888;
    address public constant cdai = 0x5d3a536E4D6DbD6114cc1Ead35777bAB948E3643;
    address public constant cether = 0x4Ddc2D193948926D02f9B1fE9e1daa0718270ED5;

    // Require a 0.1 buffer between market collateral factor and strategy's collateral factor when leveraging
    uint256 colFactorLeverageBuffer = 100;
    uint256 colFactorLeverageBufferMax = 1000;

    // Allow a 0.05 buffer between market collateral factor and strategy's collateral factor until we have to deleverage
    // This is so we can hit max leverage and keep accruing interest
    uint256 colFactorSyncBuffer = 50;
    uint256 colFactorSyncBufferMax = 1000;

    constructor() public {
        // Enter cDAI Market
        address[] memory ctokens = new address[](1);
        ctokens[0] = cdai;
        IComptroller(comptroller).enterMarkets(ctokens);
    }

    // **** Modifiers **** //

    // **** Views **** //

    function getSuppliedView() public view returns (uint256) {
        (, uint256 cTokenBal, , uint256 exchangeRate) = ICToken(cdai).getAccountSnapshot(address(this));
        (, uint256 bal) = mulScalarTruncate(Exp({mantissa: exchangeRate}), cTokenBal);
        return bal;
    }

    function getBorrowedView() public view returns (uint256) {
        return ICToken(cdai).borrowBalanceStored(address(this));
    }

    // Given an unleveraged supply balance, return the target leveraged supply balance which is still within the safety buffer
    function getLeveragedSupplyTarget(uint256 supplyBalance) public view returns (uint256) {
        uint256 leverage = getMaxLeverage();
        return supplyBalance.mul(leverage).div(1e18);
    }

    function getSafeLeverageColFactor() public view returns (uint256) {
        uint256 colFactor = getMarketColFactor();
        // Collateral factor within the buffer
        uint256 safeColFactor = colFactor.sub(colFactorLeverageBuffer.mul(1e18).div(colFactorLeverageBufferMax));
        return safeColFactor;
    }

    function getSafeSyncColFactor() public view returns (uint256) {
        uint256 colFactor = getMarketColFactor();
        // Collateral factor within the buffer
        uint256 safeColFactor = colFactor.sub(colFactorSyncBuffer.mul(1e18).div(colFactorSyncBufferMax));
        return safeColFactor;
    }

    function getMarketColFactor() public view returns (uint256) {
        (, uint256 colFactor) = IComptroller(comptroller).markets(cdai);
        return colFactor;
    }

    // Max leverage we can go up to, w.r.t safe buffer
    function getMaxLeverage() public view returns (uint256) {
        uint256 safeLeverageColFactor = getSafeLeverageColFactor();
        // Infinite geometric series
        uint256 leverage = uint256(1e36).div(1e18 - safeLeverageColFactor);
        return leverage;
    }	
	
    // If we have a strategy position at this SOS borrow rate and left unmonitored for 24+ hours, we might get liquidated
    // To safeguard with enough buffer, we divide the borrow rate by 2 which indicates allowing 48 hours response time
    function getSOSBorrowRate() public view returns (uint256) {
        uint256 safeColFactor = getSafeLeverageColFactor();
        return (colFactorLeverageBuffer.mul(182).mul(1e36).div(colFactorLeverageBufferMax)).div(safeColFactor);
    }

    // **** Pseudo-view functions (use `callStatic` on these) **** //
    /* The reason why these exists is because of the nature of the
       interest accruing supply + borrow balance. The "view" methods
       are technically snapshots and don't represent the real value.
       As such there are pseudo view methods where you can retrieve the
       results by calling `callStatic`.
    */

    function getCompAccrued() public returns (uint256) {
        (, , , uint256 accrued) = ICompoundLens(lens).getCompBalanceMetadataExt(comp, comptroller, address(this));
        return accrued;
    }

    function getColFactor() public returns (uint256) {
        uint256 supplied = getSupplied();
        uint256 borrowed = getBorrowed();

        return borrowed.mul(1e18).div(supplied);
    }

    function getSuppliedUnleveraged() public returns (uint256) {
        uint256 supplied = getSupplied();
        uint256 borrowed = getBorrowed();

        return supplied.sub(borrowed);
    }

    function getSupplied() public returns (uint256) {
        return ICToken(cdai).balanceOfUnderlying(address(this));
    }

    function getBorrowed() public returns (uint256) {
        return ICToken(cdai).borrowBalanceCurrent(address(this));
    }

    function getBorrowable() public returns (uint256) {
        uint256 supplied = getSupplied();
        uint256 borrowed = getBorrowed();

        (, uint256 colFactor) = IComptroller(comptroller).markets(cdai);

        // 99.99% just in case some dust accumulates
        return supplied.mul(colFactor).div(1e18).sub(borrowed).mul(9999).div(10000);
    }

    function getCurrentLeverage() public returns (uint256) {
        uint256 supplied = getSupplied();
        uint256 borrowed = getBorrowed();

        return supplied.mul(1e18).div(supplied.sub(borrowed));
    }

    // **** Setters **** //

    // **** State mutations **** //
    
    // comment-out function sync() public returns (bool) 

    // Leverages until we're supplying <x> amount
    // 1. Redeem <x> DAI
    // 2. Repay <x> DAI
    function _lUntil(uint256 _supplyAmount) internal {
        // 1. Borrow out <X> DAI
        // 2. Supply <X> DAI

        uint256 leverage = getMaxLeverage();
        uint256 unleveragedSupply = getSuppliedUnleveraged();
        require(_supplyAmount >= unleveragedSupply && _supplyAmount <= unleveragedSupply.mul(leverage).div(1e18), "!leverage");

        // Since we're only leveraging one asset
        // Supplied = borrowed
        uint256 _borrowAndSupply;
        uint256 supplied = getSupplied();
        while (supplied < _supplyAmount) {
            _borrowAndSupply = getBorrowable();

            if (supplied.add(_borrowAndSupply) > _supplyAmount) {
                _borrowAndSupply = _supplyAmount.sub(supplied);
            }

            ICToken(cdai).borrow(_borrowAndSupply);
            _supplyAllDAI();

            supplied = supplied.add(_borrowAndSupply);
        }
    }

    // Deleverages until we're supplying <x> amount
    // 1. Redeem <x> DAI
    // 2. Repay <x> DAI
    function _dlUntil(uint256 _supplyAmount) internal {
        uint256 unleveragedSupply = getSuppliedUnleveraged();
        uint256 supplied = getSupplied();
        require(_supplyAmount >= unleveragedSupply && _supplyAmount <= supplied, "!deleverage");

        // Since we're only leveraging on 1 asset
        // redeemable = borrowable
        uint256 _redeemAndRepay = getBorrowable();
        do {
            if (supplied.sub(_redeemAndRepay) < _supplyAmount) {
                _redeemAndRepay = supplied.sub(_supplyAmount);
            }

            require(ICToken(cdai).redeemUnderlying(_redeemAndRepay) == 0, "!redeemDlUntil");
            IERC20(dai).safeApprove(cdai, 0);
            IERC20(dai).safeApprove(cdai, _redeemAndRepay);
            require(ICToken(cdai).repayBorrow(_redeemAndRepay) == 0, "!repay");

            supplied = supplied.sub(_redeemAndRepay);
        } while (supplied > _supplyAmount);
    }
	
    // **** internal state changer ****
	
	// for redeem supplied (unleveraged) DAI from compound
    function _redeemDAI(uint256 _want) internal {
        uint256 maxRedeem = getSuppliedUnleveraged();
        _want = _want > maxRedeem? maxRedeem : _want;
        
		uint256 _redeem = _want;
        if (_redeem > 0) {
            // Make sure market can cover liquidity
            require(ICToken(cdai).getCash() >= _redeem, "!cash-liquidity");

            // How much borrowed amount do we need to free?
            uint256 borrowed = getBorrowed();
            uint256 supplied = getSupplied();
            uint256 curLeverage = getCurrentLeverage();
            uint256 borrowedToBeFree = _redeem.mul(curLeverage).div(1e18);

            // If the amount we need to free is > borrowed, Just free up all the borrowed amount
            if (borrowedToBeFree > borrowed) {
                _dlUntil(getSuppliedUnleveraged());
            } else {
                // Otherwise just keep freeing up borrowed amounts until we hit a safe number to redeem our underlying
                _dlUntil(supplied.sub(borrowedToBeFree));
            }

            // Redeems underlying
            require(ICToken(cdai).redeemUnderlying(_redeem) == 0, "!redeem");
        }
    }
	
	function _supplyAllDAI() internal {
	    uint256 _wad = IERC20(dai).balanceOf(address(this));
        _supplyDAI(_wad);
    }
	
	function _supplyDAI(uint256 _wad) internal {
        if (_wad > 0) {
            IERC20(dai).safeApprove(cdai, 0);
            IERC20(dai).safeApprove(cdai, _wad);
            require(ICToken(cdai).mint(_wad) == 0, "!depositIntoCmpd");
        }
    }
	
	function _claimComp() internal {
        address[] memory ctokens = new address[](1);
        ctokens[0] = cdai;
        IComptroller(comptroller).claimComp(address(this), ctokens);
	}
}


interface AggregatorV3Interface {
  
  function latestRoundData() external view returns (
      uint80 roundId,
      int256 answer,
      uint256 startedAt,
      uint256 updatedAt,
      uint80 answeredInRound
  );

}

interface ManagerLike {
    function ilks(uint256) external view returns (bytes32);
    function owns(uint256) external view returns (address);
    function urns(uint256) external view returns (address);
    function vat() external view returns (address);
    function open(bytes32, address) external returns (uint256);
    function give(uint256, address) external;
    function frob(uint256, int256, int256) external;
    function flux(uint256, address, uint256) external;
    function move(uint256, address, uint256) external;
    function exit(address, uint256, address, uint256) external;
    function quit(uint256, address) external;
    function enter(address, uint256) external;
}

interface VatLike {
    function can(address, address) external view returns (uint256);
    function ilks(bytes32) external view returns (uint256, uint256, uint256, uint256, uint256);
    function dai(address) external view returns (uint256);
    function urns(bytes32, address) external view returns (uint256, uint256);
    function frob(bytes32, address, address, address, int256, int256) external;
    function hope(address) external;
    function move(address, address, uint256) external;
}

interface GemJoinLike {
    function dec() external returns (uint256);
    function join(address, uint256) external payable;
    function exit(address, uint256) external;
}

interface DaiJoinLike {
    function join(address, uint256) external payable;
    function exit(address, uint256) external;
}

interface JugLike {
    function drip(bytes32) external returns (uint256);
}


// Base contract for MakerDAO based DAI-minting strategies

abstract contract StrategyMakerBase is StrategyBase {
    // MakerDAO modules
    address public dssCdpManager = 0x5ef30b9986345249bc32d8928B7ee64DE9435E39;
    address public daiJoin = 0x9759A6Ac90977b93B58547b4A71c78317f391A28;
    address public jug = 0x19c0976f590D67707E62397C87829d896Dc0f1F1;
    address public vat = 0x35D1b3F3D7966A1DFe207aa4514C12a259A0492B;
    address public debtToken = 0x6B175474E89094C44Da98b954EedeAC495271d0F;
    uint256 public minDebt = 501000000000000000000;

    // sub-strategy related constants
    address public collateral;
    uint256 public collateralDecimal = 1e18;
    address public gemJoin;
    address public collateralOracle;
    bytes32 public collateralIlk;
    AggregatorV3Interface internal priceFeed;
	
    // singleton CDP for this strategy
    uint256 public cdpId = 0;
	
    // configurable minimum collateralization percent this strategy would hold for CDP
    uint256 public minRatio = 300;
    // collateralization percent buffer in CDP debt actions
    uint256 public ratioBuff = 500;
    uint256 public ratioBuffMax = 10000;

    // Keeper bots, maintain ratio above minimum requirement
    mapping(address => bool) keepers;

    constructor(
        address _collateralJoin,
        bytes32 _collateralIlk,
        address _collateral,
        uint256 _collateralDecimal,
        address _collateralOracle,
        address _want,
        address _governance,
        address _strategist,
        address _controller,
        address _timelock
    )
        public
        StrategyBase(_want, _governance, _strategist, _controller, _timelock)
    {
        require(_want == _collateral, '!mismatchWant');
		
        gemJoin = _collateralJoin;
        collateralIlk = _collateralIlk;		    
        collateral = _collateral;   
        collateralDecimal = _collateralDecimal;
        collateralOracle = _collateralOracle;
        priceFeed = AggregatorV3Interface(collateralOracle);
    }

    // **** Modifiers **** //

    modifier onlyKeepers {
        require(
            keepers[msg.sender] ||
                msg.sender == address(this) ||
                msg.sender == strategist ||
                msg.sender == governance,
            "!keepers"
        );
        _;
    }
	
    modifier onlyGovernanceAndStrategist {
        require(msg.sender == governance || msg.sender == strategist, "!governance");
        _;
    }
	
    modifier onlyCDPInUse {
        uint256 collateralAmt = getCollateralBalance();
        require(collateralAmt > 0, '!zeroCollateral');
		
        uint256 debtAmt = getDebtBalance();
        require(debtAmt > 0, '!zeroDebt');		
        _;
    }
	
    modifier onlyCDPInitiated {        
        require(cdpId > 0, '!noCDP');	
        _;
    }
    
    modifier onlyAboveMinDebt(uint256 _daiAmt) {  
        uint256 debtAmt = getDebtBalance();   
        require((_daiAmt < debtAmt && (debtAmt.sub(_daiAmt) >= minDebt)) || debtAmt <= _daiAmt, '!minDebt');
        _;
    }
	
    function getCollateralBalance() public view returns (uint256) {
        uint256 ink;
        address urnHandler = ManagerLike(dssCdpManager).urns(cdpId);
        (ink, ) = VatLike(vat).urns(collateralIlk, urnHandler);
        return ink;
    }
	
    function getDebtBalance() public view returns (uint256) {	
        uint256 art;
        uint256 rate;
        address urnHandler = ManagerLike(dssCdpManager).urns(cdpId);
        (, art) = VatLike(vat).urns(collateralIlk, urnHandler);
        (, rate, , , ) = VatLike(vat).ilks(collateralIlk);
        return art.mul(rate).div(1e27);
    }	

    // **** Getters ****
	
    function balanceOfPool() public override view returns (uint256){
        return getCollateralBalance();
    }

    function collateralValue(uint256 collateralAmt) public view returns (uint256){
        uint256 collateralPrice = getLatestCollateralPrice();
        return collateralAmt.mul(collateralPrice).mul(1e18).div(collateralDecimal);
    }

    function currentRatio() public onlyCDPInUse view returns (uint256) {	    
        uint256 collateralAmt = collateralValue(getCollateralBalance()).mul(100);
        uint256 debtAmt = getDebtBalance();		
        return collateralAmt.div(debtAmt);
    } 
    
    // if borrow is true (for lockAndDraw): return (maxDebt - currentDebt) if positive value, otherwise return 0
    // if borrow is false (for redeemAndFree): return (currentDebt - maxDebt) if positive value, otherwise return 0
    function calculateDebtFor(uint256 collateralAmt, bool borrow) public view returns (uint256) {
        uint256 maxDebt = collateralValue(collateralAmt).mul(10000).div(minRatio.mul(10000).mul(ratioBuffMax + ratioBuff).div(ratioBuffMax).div(100));
		
        uint256 debtAmt = getDebtBalance();
		
        uint256 debt = 0;
        
        if (borrow && maxDebt >= debtAmt){
            debt = maxDebt.sub(debtAmt);
        } else if (!borrow && debtAmt >= maxDebt){
            debt = debtAmt.sub(maxDebt);
        }
        
        return (debt > 0)? debt : 0;
    }

    function borrowableDebt() public view returns (uint256) {
        uint256 collateralAmt = getCollateralBalance();
        return calculateDebtFor(collateralAmt, true);
    }

    function requiredPaidDebt(uint256 _redeemCollateralAmt) public view returns (uint256) {
        uint256 collateralAmt = getCollateralBalance().sub(_redeemCollateralAmt);
        return calculateDebtFor(collateralAmt, false);
    }

    // **** sub-strategy implementation ****
    function _convertWantToBuyback(uint256 _lpAmount) internal virtual override returns (address, uint256);
	
    function _depositDAI(uint256 _daiAmt) internal virtual;
	
    function _withdrawDAI(uint256 _daiAmt) internal virtual;
	
    // **** Oracle (using chainlink) ****
	
    function getLatestCollateralPrice() public view returns (uint256){
        require(collateralOracle != address(0), '!_collateralOracle');	
        (
            uint80 roundID, 
            int price,
            uint startedAt,
            uint timeStamp,
            uint80 answeredInRound
        ) = priceFeed.latestRoundData();
		
        if (price > 0){
            return uint256(price)/1e8;
        } else{
            return 0;
        }
    }

    // **** Setters ****
 
    function setMinDebt(uint256 _minDebt) external onlyGovernanceAndStrategist {
        minDebt = _minDebt;
    }	
 
    function setMinRatio(uint256 _minRatio) external onlyGovernanceAndStrategist {
        minRatio = _minRatio;
    }	
	
    function setRatioBuff(uint256 _ratioBuff) external onlyGovernanceAndStrategist {
        ratioBuff = _ratioBuff;
    }	

    function addKeeper(address _keeper) external onlyGovernanceAndStrategist {
        keepers[_keeper] = true;
    }

    function removeKeeper(address _keeper) external onlyGovernanceAndStrategist {
        keepers[_keeper] = false;
    }
	
    // **** MakerDAO CDP actions ****
    uint256 constant RAY = 10 ** 27;

    function mul(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require(y == 0 || (z = x * y) / y == x, "mul-overflow");
    }
	
    function toRad(uint256 wad) internal pure returns (uint256 rad) {
        rad = mul(wad, RAY);
    }
	
    function sub(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x - y) <= x, "sub-overflow");
    }
	
    function toInt(uint256 x) internal pure returns (int256 y) {
        y = int256(x);
        require(y >= 0, "int-overflow");
    }
	
    function convertTo18(address gemJoin, uint256 amt) internal returns (uint256 wad) {
        wad = mul(amt, 10 ** (18 - GemJoinLike(gemJoin).dec()));
    }
	
    function _getDrawDart(address vat, address jug, address urn, bytes32 ilk, uint wad) internal returns (int256 dart) {
        uint256 rate = JugLike(jug).drip(ilk);
        uint256 dai = VatLike(vat).dai(urn);
        if (dai < toRad(wad)) {
            dart = toInt(sub(toRad(wad), dai).div(rate));
            dart = mul(uint256(dart), rate) < toRad(wad) ? dart + 1 : dart;
        }
    }
	
	function _getWipeDart(address vat, uint dai, address urn, bytes32 ilk) internal view returns (int256 dart) {
        (, uint256 rate,,,) = VatLike(vat).ilks(ilk);
        (, uint256 art) = VatLike(vat).urns(ilk, urn);
        dart = toInt(dai.div(rate));
        dart = uint256(dart) <= art ? - dart : - toInt(art);
    }
	
    function openCDP() external {
        require(msg.sender == governance, "!governance");
        require(cdpId <= 0, "!cdpAlreadyOpened");
		
        cdpId = ManagerLike(dssCdpManager).open(collateralIlk, address(this));		
		
        IERC20(collateral).approve(gemJoin, uint256(-1));
        IERC20(debtToken).approve(daiJoin, uint256(-1));
    }
	
    function getUrnVatIlk() internal returns (address, address, bytes32){
        return (ManagerLike(dssCdpManager).urns(cdpId), ManagerLike(dssCdpManager).vat(), ManagerLike(dssCdpManager).ilks(cdpId));
    }
	
    function addCollateralAndBorrow(uint256 _collateralAmt, uint256 _daiAmt) internal onlyCDPInitiated {   
        require(_daiAmt.add(getDebtBalance()) >= minDebt, '!minDebt');
        (address urn, address vat, bytes32 ilk) = getUrnVatIlk();		
		GemJoinLike(gemJoin).join(urn, _collateralAmt);  
		ManagerLike(dssCdpManager).frob(cdpId, toInt(convertTo18(gemJoin, _collateralAmt)), _getDrawDart(vat, jug, urn, ilk, _daiAmt));
		ManagerLike(dssCdpManager).move(cdpId, address(this), toRad(_daiAmt));
        if (VatLike(vat).can(address(this), address(daiJoin)) == 0) {
            VatLike(vat).hope(daiJoin);
        }
        DaiJoinLike(daiJoin).exit(address(this), _daiAmt);
    } 
	
    function repayDAI(uint256 _daiAmt) internal onlyCDPInitiated onlyAboveMinDebt(_daiAmt) { 
        (address urn, address vat, bytes32 ilk) = getUrnVatIlk();		
        DaiJoinLike(daiJoin).join(urn, _daiAmt);
        ManagerLike(dssCdpManager).frob(cdpId, 0, _getWipeDart(vat, VatLike(vat).dai(urn), urn, ilk));
    } 
	
    function repayAndRedeemCollateral(uint256 _collateralAmt, uint _daiAmt) internal onlyCDPInitiated onlyAboveMinDebt(_daiAmt) { 
        (address urn, address vat, bytes32 ilk) = getUrnVatIlk();
        if (_daiAmt > 0){
            DaiJoinLike(daiJoin).join(urn, _daiAmt);
        }
        uint256 wad18 = convertTo18(gemJoin, _collateralAmt);
        ManagerLike(dssCdpManager).frob(cdpId, -toInt(wad18),  _getWipeDart(vat, VatLike(vat).dai(urn), urn, ilk));
        ManagerLike(dssCdpManager).flux(cdpId, address(this), wad18);
        GemJoinLike(gemJoin).exit(address(this), _collateralAmt);
    } 

    // **** State Mutation functions ****
	
    function keepMinRatio() external onlyCDPInUse onlyKeepers {		
        uint256 requiredPaidback = requiredPaidDebt(0);
        if (requiredPaidback > 0){
            _withdrawDAI(requiredPaidback);
            uint256 wad = IERC20(debtToken).balanceOf(address(this));
            require(wad >= requiredPaidback, '!mismatchAfterWithdraw');
			
            repayDAI(requiredPaidback);
            uint256 goodRatio = currentRatio();
            require(goodRatio >= minRatio.sub(1), '!stillBelowMinRatio');
        }
    }
	
    function deposit() public override {
        uint256 _want = IERC20(want).balanceOf(address(this));
        if (_want > 0) {	
            uint256 _newDebt = calculateDebtFor(_want.add(getCollateralBalance()), true);
            if(_newDebt.add(getDebtBalance()) >= minDebt){
               addCollateralAndBorrow(_want, _newDebt);
               uint256 wad = IERC20(debtToken).balanceOf(address(this));
               if(wad < _newDebt){
                  _newDebt = wad;
               }
               _depositDAI(_newDebt);
            }
        }
    }

    function _withdrawSome(uint256 _amount) internal override returns (uint256) {
        uint256 requiredPaidback = requiredPaidDebt(_amount);
        if (requiredPaidback > 0){
            _withdrawDAI(requiredPaidback);
        }
		
        uint256 wad = IERC20(debtToken).balanceOf(address(this));
        require(wad >= requiredPaidback, '!mismatchAfterWithdraw');
		
        repayAndRedeemCollateral(_amount, requiredPaidback);
        return _amount;
    }
    
}

contract StrategyMakerWETHV1 is StrategyMakerBase, StrategyCmpdDaiBase {
    // strategy specific
    address public weth_collateral = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
    address public link_eth_usd = 0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419;
    uint256 public weth_collateral_decimal = 1e18;
    bytes32 public weth_ilk = "ETH-A";
    address public weth_apt = 0x2F0b23f53734252Bda2277357e97e1517d6B042A;

    constructor(address _governance, address _strategist, address _controller, address _timelock) 
        public StrategyMakerBase(
            weth_apt,
            weth_ilk,
            weth_collateral,
            weth_collateral_decimal,			
            link_eth_usd,
            weth_collateral,
            _governance,
            _strategist,
            _controller,
            _timelock
        )
    {
	   
    }
	
    // **** Setters ****	

    function setColFactorLeverageBuffer(uint256 _colFactorLeverageBuffer) public onlyGovernanceAndStrategist {
        colFactorLeverageBuffer = _colFactorLeverageBuffer;
    }

    function setColFactorSyncBuffer(uint256 _colFactorSyncBuffer) public onlyGovernanceAndStrategist {
        colFactorSyncBuffer = _colFactorSyncBuffer;
    }
	
    // **** State Mutation functions ****

    function leverageToMax() public onlyKeepers{
        uint256 unleveragedSupply = getSuppliedUnleveraged();
        uint256 idealSupply = getLeveragedSupplyTarget(unleveragedSupply);
        _lUntil(idealSupply);
    }

    function deleverageToMin() public onlyKeepers{
        uint256 unleveragedSupply = getSuppliedUnleveraged();
        _dlUntil(unleveragedSupply);
    }
	
    function leverageUntil(uint256 _supplyAmount) public onlyKeepers {
        _lUntil(_supplyAmount);
    }
	
    function deleverageUntil(uint256 _supplyAmount) public onlyKeepers {
        _dlUntil(_supplyAmount);
    }
	
    function harvest() public override onlyBenevolent {
        _claimComp();
		
        uint256 _comp = IERC20(comp).balanceOf(address(this));
        if (_comp > 0) {
            _swapUniswap(comp, want, _comp);
        }

        uint256 _want = IERC20(want).balanceOf(address(this));
        uint256 _buybackAmount = _want.mul(performanceFee).div(performanceMax);

        if (buybackEnabled == true && _buybackAmount > 0) {
            buybackAndNotify(want, _buybackAmount);
        } else {
            // We want to get back WETH
            if (_want > 0) {
                // Performance Fees goes to treasury
                IERC20(want).safeTransfer(IController(controller).treasury(), _want.mul(performanceFee).div(performanceMax));
            }
        }

        // re-invest to compounding profit
        if (_want > 0) {
            deposit();
        }
    }
	
    function _convertWantToBuyback(uint256 _lpAmount) internal override returns (address, uint256){
        return (weth_collateral, _lpAmount);
    }
	
    function _depositDAI(uint256 _daiAmt) internal override{	
        if (_daiAmt > 0){		
            _supplyDAI(_daiAmt);
        }
    }
	
    function _withdrawDAI(uint256 _daiAmt) internal override{	
        if (_daiAmt > 0){			
            _redeemDAI(_daiAmt);
        }
    }

    // **** Views ****

    function getName() external override pure returns (string memory) {
        return "StrategyMakerWETHV1";
    }
}