pragma solidity ^0.6.0;
pragma experimental ABIEncoderV2;


interface ERC20 {
    function totalSupply() external view returns (uint256 supply);

    function balanceOf(address _owner) external view returns (uint256 balance);

    function transfer(address _to, uint256 _value) external returns (bool success);

    function transferFrom(address _from, address _to, uint256 _value)
        external
        returns (bool success);

    function approve(address _spender, uint256 _value) external returns (bool success);

    function allowance(address _owner, address _spender) external view returns (uint256 remaining);

    function decimals() external view returns (uint256 digits);

    event Approval(address indexed _owner, address indexed _spender, uint256 _value);
}

abstract contract GasTokenInterface is ERC20 {
    function free(uint256 value) public virtual returns (bool success);

    function freeUpTo(uint256 value) public virtual returns (uint256 freed);

    function freeFrom(address from, uint256 value) public virtual returns (bool success);

    function freeFromUpTo(address from, uint256 value) public virtual returns (uint256 freed);
}

contract GasBurner {
    // solhint-disable-next-line const-name-snakecase
    GasTokenInterface public constant gasToken = GasTokenInterface(0x0000000000b3F879cb30FE243b4Dfee438691c04);

    modifier burnGas(uint _amount) {
        uint gst2Amount = _amount;

        if (_amount == 0) {
            gst2Amount = (gasleft() + 14154) / (2 * 24000 - 6870);
            gst2Amount = gst2Amount - (gst2Amount / 3); // 33.3% less because of gaslimit != gas_used
        }

        if (gasToken.balanceOf(address(this)) >= gst2Amount) {
            gasToken.free(gst2Amount);
        }

        _;
    }
}

abstract contract DSProxyInterface {

    /// Truffle wont compile if this isn't commented
    // function execute(bytes memory _code, bytes memory _data)
    //     public virtual
    //     payable
    //     returns (address, bytes32);

    function execute(address _target, bytes memory _data) public virtual payable returns (bytes32);

    function setCache(address _cacheAddr) public virtual payable returns (bool);

    function owner() public virtual returns (address);
}

library Address {
    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);
    }

    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");
    }

    function functionCall(address target, bytes memory data) internal returns (bytes memory) {
      return functionCall(target, data, "Address: low-level call failed");
    }

    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
        return _functionCallWithValue(target, data, 0, errorMessage);
    }

    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");
    }

    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);
            }
        }
    }
}

// SPDX-License-Identifier: MIT
library SafeMath {
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    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;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by 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;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}

library SafeERC20 {
    using SafeMath for uint256;
    using Address for address;

    function safeTransfer(ERC20 token, address to, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
    }

    function safeTransferFrom(ERC20 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.
     */
    function safeApprove(ERC20 token, address spender, uint256 value) internal {
        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
    }

    function safeIncreaseAllowance(ERC20 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(ERC20 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));
    }

    function _callOptionalReturn(ERC20 token, bytes memory data) private {

        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");
        }
    }
}

contract AdminAuth {

    using SafeERC20 for ERC20;

    address public owner;
    address public admin;

    modifier onlyOwner() {
        require(owner == msg.sender);
        _;
    }

    constructor() public {
        owner = msg.sender;
    }

    /// @notice Admin is set by owner first time, after that admin is super role and has permission to change owner
    /// @param _admin Address of multisig that becomes admin
    function setAdminByOwner(address _admin) public {
        require(msg.sender == owner);
        require(admin == address(0));

        admin = _admin;
    }

    /// @notice Admin is able to set new admin
    /// @param _admin Address of multisig that becomes new admin
    function setAdminByAdmin(address _admin) public {
        require(msg.sender == admin);

        admin = _admin;
    }

    /// @notice Admin is able to change owner
    /// @param _owner Address of new owner
    function setOwnerByAdmin(address _owner) public {
        require(msg.sender == admin);

        owner = _owner;
    }

    /// @notice Destroy the contract
    function kill() public onlyOwner {
        selfdestruct(payable(owner));
    }

    /// @notice  withdraw stuck funds
    function withdrawStuckFunds(address _token, uint _amount) public onlyOwner {
        if (_token == 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE) {
            payable(owner).transfer(_amount);
        } else {
            ERC20(_token).safeTransfer(owner, _amount);
        }
    }
}

/// @title Contract with the actuall DSProxy permission calls the automation operations
contract CompoundMonitorProxy is AdminAuth {

    using SafeERC20 for ERC20;

    uint public CHANGE_PERIOD;
    address public monitor;
    address public newMonitor;
    address public lastMonitor;
    uint public changeRequestedTimestamp;

    mapping(address => bool) public allowed;

    event MonitorChangeInitiated(address oldMonitor, address newMonitor);
    event MonitorChangeCanceled();
    event MonitorChangeFinished(address monitor);
    event MonitorChangeReverted(address monitor);

    // if someone who is allowed become malicious, owner can't be changed
    modifier onlyAllowed() {
        require(allowed[msg.sender] || msg.sender == owner);
        _;
    }

    modifier onlyMonitor() {
        require (msg.sender == monitor);
        _;
    }

    constructor(uint _changePeriod) public {
        CHANGE_PERIOD = _changePeriod * 1 days;
    }

    /// @notice Only monitor contract is able to call execute on users proxy
    /// @param _owner Address of cdp owner (users DSProxy address)
    /// @param _compoundSaverProxy Address of CompoundSaverProxy
    /// @param _data Data to send to CompoundSaverProxy
    function callExecute(address _owner, address _compoundSaverProxy, bytes memory _data) public payable onlyMonitor {
        // execute reverts if calling specific method fails
        DSProxyInterface(_owner).execute{value: msg.value}(_compoundSaverProxy, _data);

        // return if anything left
        if (address(this).balance > 0) {
            msg.sender.transfer(address(this).balance);
        }
    }

    /// @notice Allowed users are able to set Monitor contract without any waiting period first time
    /// @param _monitor Address of Monitor contract
    function setMonitor(address _monitor) public onlyAllowed {
        require(monitor == address(0));
        monitor = _monitor;
    }

    /// @notice Allowed users are able to start procedure for changing monitor
    /// @dev after CHANGE_PERIOD needs to call confirmNewMonitor to actually make a change
    /// @param _newMonitor address of new monitor
    function changeMonitor(address _newMonitor) public onlyAllowed {
        require(changeRequestedTimestamp == 0);

        changeRequestedTimestamp = now;
        lastMonitor = monitor;
        newMonitor = _newMonitor;

        emit MonitorChangeInitiated(lastMonitor, newMonitor);
    }

    /// @notice At any point allowed users are able to cancel monitor change
    function cancelMonitorChange() public onlyAllowed {
        require(changeRequestedTimestamp > 0);

        changeRequestedTimestamp = 0;
        newMonitor = address(0);

        emit MonitorChangeCanceled();
    }

    /// @notice Anyone is able to confirm new monitor after CHANGE_PERIOD if process is started
    function confirmNewMonitor() public onlyAllowed {
        require((changeRequestedTimestamp + CHANGE_PERIOD) < now);
        require(changeRequestedTimestamp != 0);
        require(newMonitor != address(0));

        monitor = newMonitor;
        newMonitor = address(0);
        changeRequestedTimestamp = 0;

        emit MonitorChangeFinished(monitor);
    }

    /// @notice Its possible to revert monitor to last used monitor
    function revertMonitor() public onlyAllowed {
        require(lastMonitor != address(0));

        monitor = lastMonitor;

        emit MonitorChangeReverted(monitor);
    }


    /// @notice Allowed users are able to add new allowed user
    /// @param _user Address of user that will be allowed
    function addAllowed(address _user) public onlyAllowed {
        allowed[_user] = true;
    }

    /// @notice Allowed users are able to remove allowed user
    /// @dev owner is always allowed even if someone tries to remove it from allowed mapping
    /// @param _user Address of allowed user
    function removeAllowed(address _user) public onlyAllowed {
        allowed[_user] = false;
    }

    function setChangePeriod(uint _periodInDays) public onlyAllowed {
        require(_periodInDays * 1 days > CHANGE_PERIOD);

        CHANGE_PERIOD = _periodInDays * 1 days;
    }

    /// @notice In case something is left in contract, owner is able to withdraw it
    /// @param _token address of token to withdraw balance
    function withdrawToken(address _token) public onlyOwner {
        uint balance = ERC20(_token).balanceOf(address(this));
        ERC20(_token).safeTransfer(msg.sender, balance);
    }

    /// @notice In case something is left in contract, owner is able to withdraw it
    function withdrawEth() public onlyOwner {
        uint balance = address(this).balance;
        msg.sender.transfer(balance);
    }
}

/// @title Stores subscription information for Compound automatization
contract CompoundSubscriptions is AdminAuth {

    struct CompoundHolder {
        address user;
        uint128 minRatio;
        uint128 maxRatio;
        uint128 optimalRatioBoost;
        uint128 optimalRatioRepay;
        bool boostEnabled;
    }

    struct SubPosition {
        uint arrPos;
        bool subscribed;
    }

    CompoundHolder[] public subscribers;
    mapping (address => SubPosition) public subscribersPos;

    uint public changeIndex;

    event Subscribed(address indexed user);
    event Unsubscribed(address indexed user);
    event Updated(address indexed user);
    event ParamUpdates(address indexed user, uint128, uint128, uint128, uint128, bool);

    /// @dev Called by the DSProxy contract which owns the Compound position
    /// @notice Adds the users Compound poistion in the list of subscriptions so it can be monitored
    /// @param _minRatio Minimum ratio below which repay is triggered
    /// @param _maxRatio Maximum ratio after which boost is triggered
    /// @param _optimalBoost Ratio amount which boost should target
    /// @param _optimalRepay Ratio amount which repay should target
    /// @param _boostEnabled Boolean determing if boost is enabled
    function subscribe(uint128 _minRatio, uint128 _maxRatio, uint128 _optimalBoost, uint128 _optimalRepay, bool _boostEnabled) external {

        // if boost is not enabled, set max ratio to max uint
        uint128 localMaxRatio = _boostEnabled ? _maxRatio : uint128(-1);
        require(checkParams(_minRatio, localMaxRatio), "Must be correct params");

        SubPosition storage subInfo = subscribersPos[msg.sender];

        CompoundHolder memory subscription = CompoundHolder({
                minRatio: _minRatio,
                maxRatio: localMaxRatio,
                optimalRatioBoost: _optimalBoost,
                optimalRatioRepay: _optimalRepay,
                user: msg.sender,
                boostEnabled: _boostEnabled
            });

        changeIndex++;

        if (subInfo.subscribed) {
            subscribers[subInfo.arrPos] = subscription;

            emit Updated(msg.sender);
            emit ParamUpdates(msg.sender, _minRatio, localMaxRatio, _optimalBoost, _optimalRepay, _boostEnabled);
        } else {
            subscribers.push(subscription);

            subInfo.arrPos = subscribers.length - 1;
            subInfo.subscribed = true;

            emit Subscribed(msg.sender);
        }
    }

    /// @notice Called by the users DSProxy
    /// @dev Owner who subscribed cancels his subscription
    function unsubscribe() external {
        _unsubscribe(msg.sender);
    }

    /// @dev Checks limit if minRatio is bigger than max
    /// @param _minRatio Minimum ratio, bellow which repay can be triggered
    /// @param _maxRatio Maximum ratio, over which boost can be triggered
    /// @return Returns bool if the params are correct
    function checkParams(uint128 _minRatio, uint128 _maxRatio) internal pure returns (bool) {

        if (_minRatio > _maxRatio) {
            return false;
        }

        return true;
    }

    /// @dev Internal method to remove a subscriber from the list
    /// @param _user The actual address that owns the Compound position
    function _unsubscribe(address _user) internal {
        require(subscribers.length > 0, "Must have subscribers in the list");

        SubPosition storage subInfo = subscribersPos[_user];

        require(subInfo.subscribed, "Must first be subscribed");

        address lastOwner = subscribers[subscribers.length - 1].user;

        SubPosition storage subInfo2 = subscribersPos[lastOwner];
        subInfo2.arrPos = subInfo.arrPos;

        subscribers[subInfo.arrPos] = subscribers[subscribers.length - 1];
        subscribers.pop(); // remove last element and reduce arr length

        changeIndex++;
        subInfo.subscribed = false;
        subInfo.arrPos = 0;

        emit Unsubscribed(msg.sender);
    }

    /// @dev Checks if the user is subscribed
    /// @param _user The actual address that owns the Compound position
    /// @return If the user is subscribed
    function isSubscribed(address _user) public view returns (bool) {
        SubPosition storage subInfo = subscribersPos[_user];

        return subInfo.subscribed;
    }

    /// @dev Returns subscribtion information about a user
    /// @param _user The actual address that owns the Compound position
    /// @return Subscription information about the user if exists
    function getHolder(address _user) public view returns (CompoundHolder memory) {
        SubPosition storage subInfo = subscribersPos[_user];

        return subscribers[subInfo.arrPos];
    }

    /// @notice Helper method to return all the subscribed CDPs
    /// @return List of all subscribers
    function getSubscribers() public view returns (CompoundHolder[] memory) {
        return subscribers;
    }

    /// @notice Helper method for the frontend, returns all the subscribed CDPs paginated
    /// @param _page What page of subscribers you want
    /// @param _perPage Number of entries per page
    /// @return List of all subscribers for that page
    function getSubscribersByPage(uint _page, uint _perPage) public view returns (CompoundHolder[] memory) {
        CompoundHolder[] memory holders = new CompoundHolder[](_perPage);

        uint start = _page * _perPage;
        uint end = start + _perPage;

        end = (end > holders.length) ? holders.length : end;

        uint count = 0;
        for (uint i = start; i < end; i++) {
            holders[count] = subscribers[i];
            count++;
        }

        return holders;
    }

    ////////////// ADMIN METHODS ///////////////////

    /// @notice Admin function to unsubscribe a CDP
    /// @param _user The actual address that owns the Compound position
    function unsubscribeByAdmin(address _user) public onlyOwner {
        SubPosition storage subInfo = subscribersPos[_user];

        if (subInfo.subscribed) {
            _unsubscribe(_user);
        }
    }
}

contract DSMath {
    function add(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x + y) >= x);
    }

    function sub(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require((z = x - y) <= x);
    }

    function mul(uint256 x, uint256 y) internal pure returns (uint256 z) {
        require(y == 0 || (z = x * y) / y == x);
    }

    function div(uint256 x, uint256 y) internal pure returns (uint256 z) {
        return x / y;
    }

    function min(uint256 x, uint256 y) internal pure returns (uint256 z) {
        return x <= y ? x : y;
    }

    function max(uint256 x, uint256 y) internal pure returns (uint256 z) {
        return x >= y ? x : y;
    }

    function imin(int256 x, int256 y) internal pure returns (int256 z) {
        return x <= y ? x : y;
    }

    function imax(int256 x, int256 y) internal pure returns (int256 z) {
        return x >= y ? x : y;
    }

    uint256 constant WAD = 10**18;
    uint256 constant RAY = 10**27;

    function wmul(uint256 x, uint256 y) internal pure returns (uint256 z) {
        z = add(mul(x, y), WAD / 2) / WAD;
    }

    function rmul(uint256 x, uint256 y) internal pure returns (uint256 z) {
        z = add(mul(x, y), RAY / 2) / RAY;
    }

    function wdiv(uint256 x, uint256 y) internal pure returns (uint256 z) {
        z = add(mul(x, WAD), y / 2) / y;
    }

    function rdiv(uint256 x, uint256 y) internal pure returns (uint256 z) {
        z = add(mul(x, RAY), y / 2) / y;
    }

    // This famous algorithm is called "exponentiation by squaring"
    // and calculates x^n with x as fixed-point and n as regular unsigned.
    //
    // It's O(log n), instead of O(n) for naive repeated multiplication.
    //
    // These facts are why it works:
    //
    //  If n is even, then x^n = (x^2)^(n/2).
    //  If n is odd,  then x^n = x * x^(n-1),
    //   and applying the equation for even x gives
    //    x^n = x * (x^2)^((n-1) / 2).
    //
    //  Also, EVM division is flooring and
    //    floor[(n-1) / 2] = floor[n / 2].
    //
    function rpow(uint256 x, uint256 n) internal pure returns (uint256 z) {
        z = n % 2 != 0 ? x : RAY;

        for (n /= 2; n != 0; n /= 2) {
            x = rmul(x, x);

            if (n % 2 != 0) {
                z = rmul(z, x);
            }
        }
    }
}

contract DefisaverLogger {
    event LogEvent(
        address indexed contractAddress,
        address indexed caller,
        string indexed logName,
        bytes data
    );

    // solhint-disable-next-line func-name-mixedcase
    function Log(address _contract, address _caller, string memory _logName, bytes memory _data)
        public
    {
        emit LogEvent(_contract, _caller, _logName, _data);
    }
}

abstract contract CompoundOracleInterface {
    function getUnderlyingPrice(address cToken) external view virtual returns (uint);
}

abstract contract ComptrollerInterface {
    function enterMarkets(address[] calldata cTokens) external virtual returns (uint256[] memory);

    function exitMarket(address cToken) external virtual returns (uint256);

    function getAssetsIn(address account) external virtual view returns (address[] memory);

    function markets(address account) public virtual view returns (bool, uint256);

    function getAccountLiquidity(address account) external virtual view returns (uint256, uint256, uint256);

    function claimComp(address holder) virtual public;
}

abstract contract CTokenInterface is ERC20 {
    function mint(uint256 mintAmount) external virtual returns (uint256);

    function mint() external virtual payable;

    function accrueInterest() public virtual returns (uint);

    function redeem(uint256 redeemTokens) external virtual returns (uint256);

    function redeemUnderlying(uint256 redeemAmount) external virtual returns (uint256);

    function borrow(uint256 borrowAmount) external virtual returns (uint256);

    function repayBorrow(uint256 repayAmount) external virtual returns (uint256);

    function repayBorrow() external virtual payable;

    function repayBorrowBehalf(address borrower, uint256 repayAmount) external virtual returns (uint256);

    function repayBorrowBehalf(address borrower) external virtual payable;

    function liquidateBorrow(address borrower, uint256 repayAmount, address cTokenCollateral)
        external virtual
        returns (uint256);

    function liquidateBorrow(address borrower, address cTokenCollateral) external virtual payable;

    function exchangeRateCurrent() external virtual returns (uint256);

    function supplyRatePerBlock() external virtual returns (uint256);

    function borrowRatePerBlock() external virtual returns (uint256);

    function totalReserves() external virtual returns (uint256);

    function reserveFactorMantissa() external virtual returns (uint256);

    function borrowBalanceCurrent(address account) external virtual returns (uint256);

    function totalBorrowsCurrent() external virtual returns (uint256);

    function getCash() external virtual returns (uint256);

    function balanceOfUnderlying(address owner) external virtual returns (uint256);

    function underlying() external virtual returns (address);

    function getAccountSnapshot(address account) external virtual view returns (uint, uint, uint, uint);
}

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);
    }

    /**
    * @dev Subtracts two numbers, returns an error on overflow (i.e. if subtrahend is greater than minuend).
    */
    function subUInt(uint a, uint b) internal pure returns (MathError, uint) {
        if (b <= a) {
            return (MathError.NO_ERROR, a - b);
        } else {
            return (MathError.INTEGER_UNDERFLOW, 0);
        }
    }

    /**
    * @dev Adds two numbers, returns an error on overflow.
    */
    function addUInt(uint a, uint b) internal pure returns (MathError, uint) {
        uint c = a + b;

        if (c >= a) {
            return (MathError.NO_ERROR, c);
        } else {
            return (MathError.INTEGER_OVERFLOW, 0);
        }
    }

    /**
    * @dev add a and b and then subtract c
    */
    function addThenSubUInt(uint a, uint b, uint c) internal pure returns (MathError, uint) {
        (MathError err0, uint sum) = addUInt(a, b);

        if (err0 != MathError.NO_ERROR) {
            return (err0, 0);
        }

        return subUInt(sum, c);
    }
}

contract Exponential is CarefulMath {
    uint constant expScale = 1e18;
    uint constant halfExpScale = expScale/2;
    uint constant mantissaOne = expScale;

    struct Exp {
        uint mantissa;
    }

    /**
     * @dev Creates an exponential from numerator and denominator values.
     *      Note: Returns an error if (`num` * 10e18) > MAX_INT,
     *            or if `denom` is zero.
     */
    function getExp(uint num, uint denom) pure internal returns (MathError, Exp memory) {
        (MathError err0, uint scaledNumerator) = mulUInt(num, expScale);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        (MathError err1, uint rational) = divUInt(scaledNumerator, denom);
        if (err1 != MathError.NO_ERROR) {
            return (err1, Exp({mantissa: 0}));
        }

        return (MathError.NO_ERROR, Exp({mantissa: rational}));
    }

    /**
     * @dev Adds two exponentials, returning a new exponential.
     */
    function addExp(Exp memory a, Exp memory b) pure internal returns (MathError, Exp memory) {
        (MathError error, uint result) = addUInt(a.mantissa, b.mantissa);

        return (error, Exp({mantissa: result}));
    }

    /**
     * @dev Subtracts two exponentials, returning a new exponential.
     */
    function subExp(Exp memory a, Exp memory b) pure internal returns (MathError, Exp memory) {
        (MathError error, uint result) = subUInt(a.mantissa, b.mantissa);

        return (error, Exp({mantissa: result}));
    }

    /**
     * @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 Multiply an Exp by a scalar, truncate, then add an to an unsigned integer, returning an unsigned integer.
     */
    function mulScalarTruncateAddUInt(Exp memory a, uint scalar, uint addend) pure internal returns (MathError, uint) {
        (MathError err, Exp memory product) = mulScalar(a, scalar);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return addUInt(truncate(product), addend);
    }

    /**
     * @dev Divide an Exp by a scalar, returning a new Exp.
     */
    function divScalar(Exp memory a, uint scalar) pure internal returns (MathError, Exp memory) {
        (MathError err0, uint descaledMantissa) = divUInt(a.mantissa, scalar);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        return (MathError.NO_ERROR, Exp({mantissa: descaledMantissa}));
    }

    /**
     * @dev Divide a scalar by an Exp, returning a new Exp.
     */
    function divScalarByExp(uint scalar, Exp memory divisor) pure internal returns (MathError, Exp memory) {
        /*
          We are doing this as:
          getExp(mulUInt(expScale, scalar), divisor.mantissa)

          How it works:
          Exp = a / b;
          Scalar = s;
          `s / (a / b)` = `b * s / a` and since for an Exp `a = mantissa, b = expScale`
        */
        (MathError err0, uint numerator) = mulUInt(expScale, scalar);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }
        return getExp(numerator, divisor.mantissa);
    }

    /**
     * @dev Divide a scalar by an Exp, then truncate to return an unsigned integer.
     */
    function divScalarByExpTruncate(uint scalar, Exp memory divisor) pure internal returns (MathError, uint) {
        (MathError err, Exp memory fraction) = divScalarByExp(scalar, divisor);
        if (err != MathError.NO_ERROR) {
            return (err, 0);
        }

        return (MathError.NO_ERROR, truncate(fraction));
    }

    /**
     * @dev Multiplies two exponentials, returning a new exponential.
     */
    function mulExp(Exp memory a, Exp memory b) pure internal returns (MathError, Exp memory) {

        (MathError err0, uint doubleScaledProduct) = mulUInt(a.mantissa, b.mantissa);
        if (err0 != MathError.NO_ERROR) {
            return (err0, Exp({mantissa: 0}));
        }

        // We add half the scale before dividing so that we get rounding instead of truncation.
        //  See "Listing 6" and text above it at https://accu.org/index.php/journals/1717
        // Without this change, a result like 6.6...e-19 will be truncated to 0 instead of being rounded to 1e-18.
        (MathError err1, uint doubleScaledProductWithHalfScale) = addUInt(halfExpScale, doubleScaledProduct);
        if (err1 != MathError.NO_ERROR) {
            return (err1, Exp({mantissa: 0}));
        }

        (MathError err2, uint product) = divUInt(doubleScaledProductWithHalfScale, expScale);
        // The only error `div` can return is MathError.DIVISION_BY_ZERO but we control `expScale` and it is not zero.
        assert(err2 == MathError.NO_ERROR);

        return (MathError.NO_ERROR, Exp({mantissa: product}));
    }

    /**
     * @dev Multiplies two exponentials given their mantissas, returning a new exponential.
     */
    function mulExp(uint a, uint b) pure internal returns (MathError, Exp memory) {
        return mulExp(Exp({mantissa: a}), Exp({mantissa: b}));
    }

    /**
     * @dev Multiplies three exponentials, returning a new exponential.
     */
    function mulExp3(Exp memory a, Exp memory b, Exp memory c) pure internal returns (MathError, Exp memory) {
        (MathError err, Exp memory ab) = mulExp(a, b);
        if (err != MathError.NO_ERROR) {
            return (err, ab);
        }
        return mulExp(ab, c);
    }

    /**
     * @dev Divides two exponentials, returning a new exponential.
     *     (a/scale) / (b/scale) = (a/scale) * (scale/b) = a/b,
     *  which we can scale as an Exp by calling getExp(a.mantissa, b.mantissa)
     */
    function divExp(Exp memory a, Exp memory b) pure internal returns (MathError, Exp memory) {
        return getExp(a.mantissa, b.mantissa);
    }

    /**
     * @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;
    }

    /**
     * @dev Checks if first Exp is less than second Exp.
     */
    function lessThanExp(Exp memory left, Exp memory right) pure internal returns (bool) {
        return left.mantissa < right.mantissa;
    }

    /**
     * @dev Checks if left Exp <= right Exp.
     */
    function lessThanOrEqualExp(Exp memory left, Exp memory right) pure internal returns (bool) {
        return left.mantissa <= right.mantissa;
    }

    /**
     * @dev Checks if left Exp > right Exp.
     */
    function greaterThanExp(Exp memory left, Exp memory right) pure internal returns (bool) {
        return left.mantissa > right.mantissa;
    }

    /**
     * @dev returns true if Exp is exactly zero
     */
    function isZeroExp(Exp memory value) pure internal returns (bool) {
        return value.mantissa == 0;
    }
}

contract CompoundSafetyRatio is Exponential, DSMath {
    // solhint-disable-next-line const-name-snakecase
    ComptrollerInterface public constant comp = ComptrollerInterface(0x3d9819210A31b4961b30EF54bE2aeD79B9c9Cd3B);

    // solhint-disable-next-line const-name-snakecase
    CompoundOracleInterface public constant oracle = CompoundOracleInterface(0xDDc46a3B076aec7ab3Fc37420A8eDd2959764Ec4);


    /// @notice Calcualted the ratio of debt / adjusted collateral
    /// @param _user Address of the user
    function getSafetyRatio(address _user) public view returns (uint) {
        // For each asset the account is in
        address[] memory assets = comp.getAssetsIn(_user);

        uint sumCollateral = 0;
        uint sumBorrow = 0;

        for (uint i = 0; i < assets.length; i++) {
            address asset = assets[i];

            (, uint cTokenBalance, uint borrowBalance, uint exchangeRateMantissa)
                                        = CTokenInterface(asset).getAccountSnapshot(_user);

            Exp memory oraclePrice;

            if (cTokenBalance != 0 || borrowBalance != 0) {
                oraclePrice = Exp({mantissa: oracle.getUnderlyingPrice(asset)});
            }

            // Sum up collateral in Eth
            if (cTokenBalance != 0) {

                (, uint collFactorMantissa) = comp.markets(address(asset));

                Exp memory collateralFactor = Exp({mantissa: collFactorMantissa});
                Exp memory exchangeRate = Exp({mantissa: exchangeRateMantissa});

                (, Exp memory tokensToEther) = mulExp3(collateralFactor, exchangeRate, oraclePrice);

                (, sumCollateral) = mulScalarTruncateAddUInt(tokensToEther, cTokenBalance, sumCollateral);
            }

            // Sum up debt in Eth
            if (borrowBalance != 0) {
                (, sumBorrow) = mulScalarTruncateAddUInt(oraclePrice, borrowBalance, sumBorrow);
            }
        }

        if (sumBorrow == 0) return uint(-1);

        uint borrowPowerUsed = (sumBorrow * 10**18) / sumCollateral;
        return wdiv(1e18, borrowPowerUsed);
    }
}

/// @title Contract implements logic of calling boost/repay in the automatic system
contract CompoundMonitor is AdminAuth, DSMath, CompoundSafetyRatio, GasBurner {

    using SafeERC20 for ERC20;

    enum Method { Boost, Repay }

    uint public REPAY_GAS_TOKEN = 25;
    uint public BOOST_GAS_TOKEN = 20;

    uint constant public MAX_GAS_PRICE = 80000000000; // 80 gwei

    uint public REPAY_GAS_COST = 2200000;
    uint public BOOST_GAS_COST = 1700000;

    address public constant GAS_TOKEN_INTERFACE_ADDRESS = 0x0000000000b3F879cb30FE243b4Dfee438691c04;
    address public constant DEFISAVER_LOGGER = 0x5c55B921f590a89C1Ebe84dF170E655a82b62126;

    CompoundMonitorProxy public compoundMonitorProxy;
    CompoundSubscriptions public subscriptionsContract;
    address public compoundFlashLoanTakerAddress;

    DefisaverLogger public logger = DefisaverLogger(DEFISAVER_LOGGER);

    /// @dev Addresses that are able to call methods for repay and boost
    mapping(address => bool) public approvedCallers;

    modifier onlyApproved() {
        require(approvedCallers[msg.sender]);
        _;
    }

    /// @param _compoundMonitorProxy Proxy contracts that actually is authorized to call DSProxy
    /// @param _subscriptions Subscriptions contract for Compound positions
    /// @param _compoundFlashLoanTaker Contract that actually performs Repay/Boost
    constructor(address _compoundMonitorProxy, address _subscriptions, address _compoundFlashLoanTaker) public {
        approvedCallers[msg.sender] = true;

        compoundMonitorProxy = CompoundMonitorProxy(_compoundMonitorProxy);
        subscriptionsContract = CompoundSubscriptions(_subscriptions);
        compoundFlashLoanTakerAddress = _compoundFlashLoanTaker;
    }

    /// @notice Bots call this method to repay for user when conditions are met
    /// @dev If the contract ownes gas token it will try and use it for gas price reduction
    /// @param _data Amount and exchange data [amount, minPrice, exchangeType, gasCost, 0xPrice]
    /// @param _addrData cTokens addreses and exchange [cCollAddress, cBorrowAddress, exchangeAddress]
    /// @param _callData 0x callData
    /// @param _user The actual address that owns the Compound position
    function repayFor(
        uint[5] memory _data, // amount, minPrice, exchangeType, gasCost, 0xPrice
        address[3] memory _addrData, // cCollAddress, cBorrowAddress, exchangeAddress
        bytes memory _callData,
        address _user
    ) public payable onlyApproved burnGas(REPAY_GAS_TOKEN) {

        (bool isAllowed, uint ratioBefore) = canCall(Method.Repay, _user);
        require(isAllowed); // check if conditions are met

        _data[3] = calcGasCost(REPAY_GAS_COST);

        compoundMonitorProxy.callExecute{value: msg.value}(
            _user,
            compoundFlashLoanTakerAddress,
            abi.encodeWithSignature("repayWithLoan(uint256[5],address[3],bytes)",
            _data, _addrData, _callData));

        (bool isGoodRatio, uint ratioAfter) = ratioGoodAfter(Method.Repay, _user);
        require(isGoodRatio); // check if the after result of the actions is good

        returnEth();

        logger.Log(address(this), _user, "AutomaticCompoundRepay", abi.encode(ratioBefore, ratioAfter));
    }

    /// @notice Bots call this method to boost for user when conditions are met
    /// @dev If the contract ownes gas token it will try and use it for gas price reduction
    /// @param _data Amount and exchange data [amount, minPrice, exchangeType, gasCost, 0xPrice]
    /// @param _addrData cTokens addreses and exchange [cCollAddress, cBorrowAddress, exchangeAddress]
    /// @param _callData 0x callData
    /// @param _user The actual address that owns the Compound position
    function boostFor(
        uint[5] memory _data, // amount, minPrice, exchangeType, gasCost, 0xPrice
        address[3] memory _addrData, // cCollAddress, cBorrowAddress, exchangeAddress
        bytes memory _callData,
        address _user
    ) public payable onlyApproved burnGas(BOOST_GAS_TOKEN) {

        (bool isAllowed, uint ratioBefore) = canCall(Method.Boost, _user);
        require(isAllowed); // check if conditions are met

        _data[3] = calcGasCost(BOOST_GAS_COST);

        compoundMonitorProxy.callExecute{value: msg.value}(
            _user,
            compoundFlashLoanTakerAddress,
            abi.encodeWithSignature("boostWithLoan(uint256[5],address[3],bytes)",
            _data, _addrData, _callData));


        (bool isGoodRatio, uint ratioAfter) = ratioGoodAfter(Method.Boost, _user);
        require(isGoodRatio);  // check if the after result of the actions is good

        returnEth();

        logger.Log(address(this), _user, "AutomaticCompoundBoost", abi.encode(ratioBefore, ratioAfter));
    }

/******************* INTERNAL METHODS ********************************/
    function returnEth() internal {
        // return if some eth left
        if (address(this).balance > 0) {
            msg.sender.transfer(address(this).balance);
        }
    }

/******************* STATIC METHODS ********************************/

    /// @notice Checks if Boost/Repay could be triggered for the CDP
    /// @dev Called by MCDMonitor to enforce the min/max check
    /// @param _method Type of action to be called
    /// @param _user The actual address that owns the Compound position
    /// @return Boolean if it can be called and the ratio
    function canCall(Method _method, address _user) public view returns(bool, uint) {
        bool subscribed = subscriptionsContract.isSubscribed(_user);
        CompoundSubscriptions.CompoundHolder memory holder = subscriptionsContract.getHolder(_user);

        // check if cdp is subscribed
        if (!subscribed) return (false, 0);

        // check if boost and boost allowed
        if (_method == Method.Boost && !holder.boostEnabled) return (false, 0);

        uint currRatio = getSafetyRatio(_user);

        if (_method == Method.Repay) {
            return (currRatio < holder.minRatio, currRatio);
        } else if (_method == Method.Boost) {
            return (currRatio > holder.maxRatio, currRatio);
        }
    }

    /// @dev After the Boost/Repay check if the ratio doesn't trigger another call
    /// @param _method Type of action to be called
    /// @param _user The actual address that owns the Compound position
    /// @return Boolean if the recent action preformed correctly and the ratio
    function ratioGoodAfter(Method _method, address _user) public view returns(bool, uint) {
        CompoundSubscriptions.CompoundHolder memory holder;

        holder= subscriptionsContract.getHolder(_user);

        uint currRatio = getSafetyRatio(_user);

        if (_method == Method.Repay) {
            return (currRatio < holder.maxRatio, currRatio);
        } else if (_method == Method.Boost) {
            return (currRatio > holder.minRatio, currRatio);
        }
    }

    /// @notice Calculates gas cost (in Eth) of tx
    /// @dev Gas price is limited to MAX_GAS_PRICE to prevent attack of draining user CDP
    /// @param _gasAmount Amount of gas used for the tx
    function calcGasCost(uint _gasAmount) public view returns (uint) {
        uint gasPrice = tx.gasprice <= MAX_GAS_PRICE ? tx.gasprice : MAX_GAS_PRICE;

        return mul(gasPrice, _gasAmount);
    }

/******************* OWNER ONLY OPERATIONS ********************************/

    /// @notice Allows owner to change gas cost for boost operation, but only up to 3 millions
    /// @param _gasCost New gas cost for boost method
    function changeBoostGasCost(uint _gasCost) public onlyOwner {
        require(_gasCost < 3000000);

        BOOST_GAS_COST = _gasCost;
    }

    /// @notice Allows owner to change gas cost for repay operation, but only up to 3 millions
    /// @param _gasCost New gas cost for repay method
    function changeRepayGasCost(uint _gasCost) public onlyOwner {
        require(_gasCost < 3000000);

        REPAY_GAS_COST = _gasCost;
    }

    /// @notice Adds a new bot address which will be able to call repay/boost
    /// @param _caller Bot address
    function addCaller(address _caller) public onlyOwner {
        approvedCallers[_caller] = true;
    }

    /// @notice Removes a bot address so it can't call repay/boost
    /// @param _caller Bot address
    function removeCaller(address _caller) public onlyOwner {
        approvedCallers[_caller] = false;
    }

    /// @notice If any tokens gets stuck in the contract owner can withdraw it
    /// @param _tokenAddress Address of the ERC20 token
    /// @param _to Address of the receiver
    /// @param _amount The amount to be sent
    function transferERC20(address _tokenAddress, address _to, uint _amount) public onlyOwner {
        ERC20(_tokenAddress).safeTransfer(_to, _amount);
    }

    /// @notice If any Eth gets stuck in the contract owner can withdraw it
    /// @param _to Address of the receiver
    /// @param _amount The amount to be sent
    function transferEth(address payable _to, uint _amount) public onlyOwner {
        _to.transfer(_amount);
    }
}