Contract Source Code:

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);
}

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);
        }
    }
}

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 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);
            }
        }
    }
}

abstract contract TokenInterface {
    function allowance(address, address) public virtual returns (uint256);

    function balanceOf(address) public virtual returns (uint256);

    function approve(address, uint256) public virtual;

    function transfer(address, uint256) public virtual returns (bool);

    function transferFrom(address, address, uint256) public virtual returns (bool);

    function deposit() public virtual payable;

    function withdraw(uint256) public virtual;
}

interface ExchangeInterfaceV2 {
    function sell(address _srcAddr, address _destAddr, uint _srcAmount) external payable returns (uint);

    function buy(address _srcAddr, address _destAddr, uint _destAmount) external payable returns(uint);

    function getSellRate(address _srcAddr, address _destAddr, uint _srcAmount) external view returns (uint);

    function getBuyRate(address _srcAddr, address _destAddr, uint _srcAmount) external view returns (uint);
}

contract ZrxAllowlist is AdminAuth {

    mapping (address => bool) public zrxAllowlist;

    function setAllowlistAddr(address _zrxAddr, bool _state) public onlyOwner {
        zrxAllowlist[_zrxAddr] = _state;
    }

    function isZrxAddr(address _zrxAddr) public view returns (bool) {
        return zrxAllowlist[_zrxAddr];
    }
}

contract Discount {
    address public owner;
    mapping(address => CustomServiceFee) public serviceFees;

    uint256 constant MAX_SERVICE_FEE = 400;

    struct CustomServiceFee {
        bool active;
        uint256 amount;
    }

    constructor() public {
        owner = msg.sender;
    }

    function isCustomFeeSet(address _user) public view returns (bool) {
        return serviceFees[_user].active;
    }

    function getCustomServiceFee(address _user) public view returns (uint256) {
        return serviceFees[_user].amount;
    }

    function setServiceFee(address _user, uint256 _fee) public {
        require(msg.sender == owner, "Only owner");
        require(_fee >= MAX_SERVICE_FEE || _fee == 0);

        serviceFees[_user] = CustomServiceFee({active: true, amount: _fee});
    }

    function disableServiceFee(address _user) public {
        require(msg.sender == owner, "Only owner");

        serviceFees[_user] = CustomServiceFee({active: false, amount: 0});
    }
}

contract SaverExchangeHelper {

    using SafeERC20 for ERC20;

    address public constant KYBER_ETH_ADDRESS = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;
    address public constant WETH_ADDRESS = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
    address public constant DGD_ADDRESS = 0xE0B7927c4aF23765Cb51314A0E0521A9645F0E2A;

    address payable public constant WALLET_ID = 0x322d58b9E75a6918f7e7849AEe0fF09369977e08;
    address public constant DISCOUNT_ADDRESS = 0x1b14E8D511c9A4395425314f849bD737BAF8208F;
    address public constant SAVER_EXCHANGE_REGISTRY = 0x25dd3F51e0C3c3Ff164DDC02A8E4D65Bb9cBB12D;

    address public constant KYBER_WRAPPER = 0x42A9237b872368E1bec4Ca8D26A928D7d39d338C;
    address public constant UNISWAP_WRAPPER = 0x880A845A85F843a5c67DB2061623c6Fc3bB4c511;
    address public constant OASIS_WRAPPER = 0x4c9B55f2083629A1F7aDa257ae984E03096eCD25;
    address public constant ERC20_PROXY_0X = 0x95E6F48254609A6ee006F7D493c8e5fB97094ceF;
    address public constant ZRX_ALLOWLIST_ADDR = 0x019739e288973F92bDD3c1d87178E206E51fd911;


    function getDecimals(address _token) internal view returns (uint256) {
        if (_token == DGD_ADDRESS) return 9;
        if (_token == KYBER_ETH_ADDRESS) return 18;

        return ERC20(_token).decimals();
    }

    function getBalance(address _tokenAddr) internal view returns (uint balance) {
        if (_tokenAddr == KYBER_ETH_ADDRESS) {
            balance = address(this).balance;
        } else {
            balance = ERC20(_tokenAddr).balanceOf(address(this));
        }
    }

    function approve0xProxy(address _tokenAddr, uint _amount) internal {
        if (_tokenAddr != KYBER_ETH_ADDRESS) {
            ERC20(_tokenAddr).safeApprove(address(ERC20_PROXY_0X), _amount);
        }
    }

    function sendLeftover(address _srcAddr, address _destAddr, address payable _to) internal {
        // send back any leftover ether or tokens
        if (address(this).balance > 0) {
            _to.transfer(address(this).balance);
        }

        if (getBalance(_srcAddr) > 0) {
            ERC20(_srcAddr).safeTransfer(_to, getBalance(_srcAddr));
        }

        if (getBalance(_destAddr) > 0) {
            ERC20(_destAddr).safeTransfer(_to, getBalance(_destAddr));
        }
    }

    function sliceUint(bytes memory bs, uint256 start) internal pure returns (uint256) {
        require(bs.length >= start + 32, "slicing out of range");

        uint256 x;
        assembly {
            x := mload(add(bs, add(0x20, start)))
        }

        return x;
    }
}

contract SaverExchangeRegistry is AdminAuth {

	mapping(address => bool) private wrappers;

	constructor() public {
		wrappers[0x880A845A85F843a5c67DB2061623c6Fc3bB4c511] = true;
		wrappers[0x4c9B55f2083629A1F7aDa257ae984E03096eCD25] = true;
		wrappers[0x42A9237b872368E1bec4Ca8D26A928D7d39d338C] = true;
	}

	function addWrapper(address _wrapper) public onlyOwner {
		wrappers[_wrapper] = true;
	}

	function removeWrapper(address _wrapper) public onlyOwner {
		wrappers[_wrapper] = false;
	}

	function isWrapper(address _wrapper) public view returns(bool) {
		return wrappers[_wrapper];
	}
}

contract SaverExchangeCore is SaverExchangeHelper, DSMath {

    // first is empty to keep the legacy order in place
    enum ExchangeType { _, OASIS, KYBER, UNISWAP, ZEROX }

    enum ActionType { SELL, BUY }

    struct ExchangeData {
        address srcAddr;
        address destAddr;
        uint srcAmount;
        uint destAmount;
        uint minPrice;
        address wrapper;
        address exchangeAddr;
        bytes callData;
        uint256 price0x;
    }

    /// @notice Internal method that preforms a sell on 0x/on-chain
    /// @dev Usefull for other DFS contract to integrate for exchanging
    /// @param exData Exchange data struct
    /// @return (address, uint) Address of the wrapper used and destAmount
    function _sell(ExchangeData memory exData) internal returns (address, uint) {

        address wrapper;
        uint swapedTokens;
        bool success;
        uint tokensLeft = exData.srcAmount;

        // if selling eth, convert to weth
        if (exData.srcAddr == KYBER_ETH_ADDRESS) {
            exData.srcAddr = ethToWethAddr(exData.srcAddr);
            TokenInterface(WETH_ADDRESS).deposit.value(exData.srcAmount)();
        }

        // Try 0x first and then fallback on specific wrapper
        if (exData.price0x > 0) {
            approve0xProxy(exData.srcAddr, exData.srcAmount);

            (success, swapedTokens, tokensLeft) = takeOrder(exData, address(this).balance, ActionType.SELL);

            if (success) {
                wrapper = exData.exchangeAddr;
            }
        }

        // fallback to desired wrapper if 0x failed
        if (!success) {
            swapedTokens = saverSwap(exData, ActionType.SELL);
            wrapper = exData.wrapper;
        }

        require(getBalance(exData.destAddr) >= wmul(exData.minPrice, exData.srcAmount), "Final amount isn't correct");

        // if anything is left in weth, pull it to user as eth
        if (getBalance(WETH_ADDRESS) > 0) {
            TokenInterface(WETH_ADDRESS).withdraw(
                TokenInterface(WETH_ADDRESS).balanceOf(address(this))
            );
        }            

        return (wrapper, swapedTokens);
    }

    /// @notice Internal method that preforms a buy on 0x/on-chain
    /// @dev Usefull for other DFS contract to integrate for exchanging
    /// @param exData Exchange data struct
    /// @return (address, uint) Address of the wrapper used and srcAmount
    function _buy(ExchangeData memory exData) internal returns (address, uint) {

        address wrapper;
        uint swapedTokens;
        bool success;

        require(exData.destAmount != 0, "Dest amount must be specified");

        // if selling eth, convert to weth
        if (exData.srcAddr == KYBER_ETH_ADDRESS) {
            exData.srcAddr = ethToWethAddr(exData.srcAddr);
            TokenInterface(WETH_ADDRESS).deposit.value(exData.srcAmount)();
        }

        if (exData.price0x > 0) { 
            approve0xProxy(exData.srcAddr, exData.srcAmount);

            (success, swapedTokens,) = takeOrder(exData, address(this).balance, ActionType.BUY);

            if (success) {
                wrapper = exData.exchangeAddr;
            }
        }

        // fallback to desired wrapper if 0x failed
        if (!success) {
            swapedTokens = saverSwap(exData, ActionType.BUY);
            wrapper = exData.wrapper;
        }

        require(getBalance(exData.destAddr) >= exData.destAmount, "Final amount isn't correct");

        // if anything is left in weth, pull it to user as eth
        if (getBalance(WETH_ADDRESS) > 0) {
            TokenInterface(WETH_ADDRESS).withdraw(
                TokenInterface(WETH_ADDRESS).balanceOf(address(this))
            );
        }

        return (wrapper, getBalance(exData.destAddr));
    }

    /// @notice Takes order from 0x and returns bool indicating if it is successful
    /// @param _exData Exchange data
    /// @param _ethAmount Ether fee needed for 0x order
    function takeOrder(
        ExchangeData memory _exData,
        uint256 _ethAmount,
        ActionType _type
    ) private returns (bool success, uint256, uint256) {

        // write in the exact amount we are selling/buing in an order
        if (_type == ActionType.SELL) {
            writeUint256(_exData.callData, 36, _exData.srcAmount);
        } else {
            writeUint256(_exData.callData, 36, _exData.destAmount);
        }

        if (ZrxAllowlist(ZRX_ALLOWLIST_ADDR).isZrxAddr(_exData.exchangeAddr)) {
            (success, ) = _exData.exchangeAddr.call{value: _ethAmount}(_exData.callData);
        } else {
            success = false;
        }

        uint256 tokensSwaped = 0;
        uint256 tokensLeft = _exData.srcAmount;

        if (success) {
            // check to see if any _src tokens are left over after exchange
            tokensLeft = getBalance(_exData.srcAddr);

            // convert weth -> eth if needed
            if (_exData.destAddr == KYBER_ETH_ADDRESS) {
                TokenInterface(WETH_ADDRESS).withdraw(
                    TokenInterface(WETH_ADDRESS).balanceOf(address(this))
                );
            }

            // get the current balance of the swaped tokens
            tokensSwaped = getBalance(_exData.destAddr);
        }

        return (success, tokensSwaped, tokensLeft);
    }

    /// @notice Returns the best estimated price from 2 exchanges
    /// @param _amount Amount of source tokens you want to exchange
    /// @param _srcToken Address of the source token
    /// @param _destToken Address of the destination token
    /// @param _exchangeType Which exchange will be used
    /// @param _type Type of action SELL|BUY
    /// @return (address, uint) The address of the best exchange and the exchange price
    function getBestPrice(
        uint256 _amount,
        address _srcToken,
        address _destToken,
        ExchangeType _exchangeType,
        ActionType _type
    ) public returns (address, uint256) {

        if (_exchangeType == ExchangeType.OASIS) {
            return (OASIS_WRAPPER, getExpectedRate(OASIS_WRAPPER, _srcToken, _destToken, _amount, _type));
        }

        if (_exchangeType == ExchangeType.KYBER) {
            return (KYBER_WRAPPER, getExpectedRate(KYBER_WRAPPER, _srcToken, _destToken, _amount, _type));
        }

        if (_exchangeType == ExchangeType.UNISWAP) {
            return (UNISWAP_WRAPPER, getExpectedRate(UNISWAP_WRAPPER, _srcToken, _destToken, _amount, _type));
        }

        uint expectedRateKyber = getExpectedRate(KYBER_WRAPPER, _srcToken, _destToken, _amount, _type);
        uint expectedRateUniswap = getExpectedRate(UNISWAP_WRAPPER, _srcToken, _destToken, _amount, _type);
        uint expectedRateOasis = getExpectedRate(OASIS_WRAPPER, _srcToken, _destToken, _amount, _type);

        if (_type == ActionType.SELL) {
            return getBiggestRate(expectedRateKyber, expectedRateUniswap, expectedRateOasis);
        } else {
            return getSmallestRate(expectedRateKyber, expectedRateUniswap, expectedRateOasis);
        }
    }

    /// @notice Return the expected rate from the exchange wrapper
    /// @dev In case of Oasis/Uniswap handles the different precision tokens
    /// @param _wrapper Address of exchange wrapper
    /// @param _srcToken From token
    /// @param _destToken To token
    /// @param _amount Amount to be exchanged
    /// @param _type Type of action SELL|BUY
    function getExpectedRate(
        address _wrapper,
        address _srcToken,
        address _destToken,
        uint256 _amount,
        ActionType _type
    ) public returns (uint256) {
        bool success;
        bytes memory result;

        if (_type == ActionType.SELL) {
            (success, result) = _wrapper.call(abi.encodeWithSignature(
                "getSellRate(address,address,uint256)",
                _srcToken,
                _destToken,
                _amount
            ));

        } else {
            (success, result) = _wrapper.call(abi.encodeWithSignature(
                "getBuyRate(address,address,uint256)",
                _srcToken,
                _destToken,
                _amount
            ));
        }

        if (success) {
            uint rate = sliceUint(result, 0);

            if (_wrapper != KYBER_WRAPPER) {
                rate = rate * (10**(18 - getDecimals(_destToken)));
            }

            return rate;
        }

        return 0;
    }

    /// @notice Calls wraper contract for exchage to preform an on-chain swap
    /// @param _exData Exchange data struct
    /// @param _type Type of action SELL|BUY
    /// @return swapedTokens For Sell that the destAmount, for Buy thats the srcAmount
    function saverSwap(ExchangeData memory _exData, ActionType _type) internal returns (uint swapedTokens) {
        require(SaverExchangeRegistry(SAVER_EXCHANGE_REGISTRY).isWrapper(_exData.wrapper), "Wrapper is not valid");

        uint ethValue = 0;

        ERC20(_exData.srcAddr).safeTransfer(_exData.wrapper, _exData.srcAmount);
        
        if (_type == ActionType.SELL) {
            swapedTokens = ExchangeInterfaceV2(_exData.wrapper).
                    sell{value: ethValue}(_exData.srcAddr, _exData.destAddr, _exData.srcAmount);
        } else {
            swapedTokens = ExchangeInterfaceV2(_exData.wrapper).
                    buy{value: ethValue}(_exData.srcAddr, _exData.destAddr, _exData.destAmount);
        }
    }

    /// @notice Finds the biggest rate between exchanges, needed for sell rate
    /// @param _expectedRateKyber Kyber rate
    /// @param _expectedRateUniswap Uniswap rate
    /// @param _expectedRateOasis Oasis rate
    function getBiggestRate(
        uint _expectedRateKyber,
        uint _expectedRateUniswap,
        uint _expectedRateOasis
    ) internal pure returns (address, uint) {
        if (
            (_expectedRateUniswap >= _expectedRateKyber) && (_expectedRateUniswap >= _expectedRateOasis)
        ) {
            return (UNISWAP_WRAPPER, _expectedRateUniswap);
        }

        if (
            (_expectedRateKyber >= _expectedRateUniswap) && (_expectedRateKyber >= _expectedRateOasis)
        ) {
            return (KYBER_WRAPPER, _expectedRateKyber);
        }

        if (
            (_expectedRateOasis >= _expectedRateKyber) && (_expectedRateOasis >= _expectedRateUniswap)
        ) {
            return (OASIS_WRAPPER, _expectedRateOasis);
        }
    }

    /// @notice Finds the smallest rate between exchanges, needed for buy rate
    /// @param _expectedRateKyber Kyber rate
    /// @param _expectedRateUniswap Uniswap rate
    /// @param _expectedRateOasis Oasis rate
    function getSmallestRate(
        uint _expectedRateKyber,
        uint _expectedRateUniswap,
        uint _expectedRateOasis
    ) internal pure returns (address, uint) {
        if (
            (_expectedRateUniswap <= _expectedRateKyber) && (_expectedRateUniswap <= _expectedRateOasis)
        ) {
            return (UNISWAP_WRAPPER, _expectedRateUniswap);
        }

        if (
            (_expectedRateKyber <= _expectedRateUniswap) && (_expectedRateKyber <= _expectedRateOasis)
        ) {
            return (KYBER_WRAPPER, _expectedRateKyber);
        }

        if (
            (_expectedRateOasis <= _expectedRateKyber) && (_expectedRateOasis <= _expectedRateUniswap)
        ) {
            return (OASIS_WRAPPER, _expectedRateOasis);
        }
    }

    function writeUint256(bytes memory _b, uint256 _index, uint _input) internal pure {
        if (_b.length < _index + 32) {
            revert("Incorrent lengt while writting bytes32");
        }

        bytes32 input = bytes32(_input);

        _index += 32;

        // Read the bytes32 from array memory
        assembly {
            mstore(add(_b, _index), input)
        }
    }

    /// @notice Converts Kybers Eth address -> Weth
    /// @param _src Input address
    function ethToWethAddr(address _src) internal pure returns (address) {
        return _src == KYBER_ETH_ADDRESS ? WETH_ADDRESS : _src;
    }

    // solhint-disable-next-line no-empty-blocks
    receive() external virtual payable {}
}

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);
    }
}

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);
        }

        _;
    }
}

contract SaverExchange is SaverExchangeCore, AdminAuth, GasBurner {

    using SafeERC20 for ERC20;

    uint256 public constant SERVICE_FEE = 800; // 0.125% Fee

    // solhint-disable-next-line const-name-snakecase
    DefisaverLogger public constant logger = DefisaverLogger(0x5c55B921f590a89C1Ebe84dF170E655a82b62126);

    uint public burnAmount = 10;

    /// @notice Takes a src amount of tokens and converts it into the dest token
    /// @dev Takes fee from the _srcAmount before the exchange
    /// @param exData [srcAddr, destAddr, srcAmount, destAmount, minPrice, exchangeType, exchangeAddr, callData, price0x]
    /// @param _user User address who called the exchange
    function sell(ExchangeData memory exData, address payable _user) public payable burnGas(burnAmount) {

        // take fee
        uint dfsFee = getFee(exData.srcAmount, exData.srcAddr);
        exData.srcAmount = sub(exData.srcAmount, dfsFee);

        // Perform the exchange
        (address wrapper, uint destAmount) = _sell(exData);

        // send back any leftover ether or tokens
        sendLeftover(exData.srcAddr, exData.destAddr, _user);

        // log the event
        logger.Log(address(this), msg.sender, "ExchangeSell", abi.encode(wrapper, exData.srcAddr, exData.destAddr, exData.srcAmount, destAmount));
    }

    /// @notice Takes a dest amount of tokens and converts it from the src token
    /// @dev Send always more than needed for the swap, extra will be returned
    /// @param exData [srcAddr, destAddr, srcAmount, destAmount, minPrice, exchangeType, exchangeAddr, callData, price0x]
    /// @param _user User address who called the exchange
    function buy(ExchangeData memory exData, address payable _user) public payable burnGas(burnAmount){

        uint dfsFee = getFee(exData.srcAmount, exData.srcAddr);
        exData.srcAmount = sub(exData.srcAmount, dfsFee);

        // Perform the exchange
        (address wrapper, uint srcAmount) = _buy(exData);

        // send back any leftover ether or tokens
        sendLeftover(exData.srcAddr, exData.destAddr, _user);

        // log the event
        logger.Log(address(this), msg.sender, "ExchangeBuy", abi.encode(wrapper, exData.srcAddr, exData.destAddr, srcAmount, exData.destAmount));

    }

    /// @notice Takes a feePercentage and sends it to wallet
    /// @param _amount Dai amount of the whole trade
    /// @param _token Address of the token
    /// @return feeAmount Amount in Dai owner earned on the fee
    function getFee(uint256 _amount, address _token) internal returns (uint256 feeAmount) {
        uint256 fee = SERVICE_FEE;

        if (Discount(DISCOUNT_ADDRESS).isCustomFeeSet(msg.sender)) {
            fee = Discount(DISCOUNT_ADDRESS).getCustomServiceFee(msg.sender);
        }

        if (fee == 0) {
            feeAmount = 0;
        } else {
            feeAmount = _amount / fee;
            if (_token == KYBER_ETH_ADDRESS) {
                WALLET_ID.transfer(feeAmount);
            } else {
                ERC20(_token).safeTransfer(WALLET_ID, feeAmount);
            }
        }
    }

    /// @notice Changes the amount of gas token we burn for each call
    /// @dev Only callable by the owner
    /// @param _newBurnAmount New amount of gas tokens to be burned
    function changeBurnAmount(uint _newBurnAmount) public {
        require(owner == msg.sender);

        burnAmount = _newBurnAmount;
    }

}

contract AllowanceProxy is AdminAuth {

    using SafeERC20 for ERC20;

    address public constant KYBER_ETH_ADDRESS = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;

    // TODO: Real saver exchange address
    SaverExchange saverExchange = SaverExchange(0x235abFAd01eb1BDa28Ef94087FBAA63E18074926);

    function callSell(SaverExchangeCore.ExchangeData memory exData) public payable {
        pullAndSendTokens(exData.srcAddr, exData.srcAmount);

        saverExchange.sell{value: msg.value}(exData, msg.sender);
    }

    function callBuy(SaverExchangeCore.ExchangeData memory exData) public payable {
        pullAndSendTokens(exData.srcAddr, exData.srcAmount);

        saverExchange.buy{value: msg.value}(exData, msg.sender);
    }

    function pullAndSendTokens(address _tokenAddr, uint _amount) internal {
        if (_tokenAddr == KYBER_ETH_ADDRESS) {
            require(msg.value >= _amount, "msg.value smaller than amount");
        } else {
            ERC20(_tokenAddr).safeTransferFrom(msg.sender, address(saverExchange), _amount);
        }
    }

    function ownerChangeExchange(address payable _newExchange) public onlyOwner {
        saverExchange = SaverExchange(_newExchange);
    }
}