add helper

contracts/SmartRoute/helper/DODOCalleeHelper.sol

@@ -0,0 +1,60 @@
+/*
+Copyright 2020 DODO ZOO.
+SPDX-License-Identifier: Apache-2.0
+
+*/
+
+pragma solidity 0.6.9;
+pragma experimental ABIEncoderV2;
+
+import {IDODOV2} from "../intf/IDODOV2.sol";
+import {IERC20} from "../../intf/IERC20.sol";
+import {IWETH} from "../../intf/IWETH.sol";
+import {SafeERC20} from "../../lib/SafeERC20.sol";
+import {ReentrancyGuard} from "../../lib/ReentrancyGuard.sol";
+
+contract DODOCalleeHelper is ReentrancyGuard {
+    using SafeERC20 for IERC20;
+    address payable public _WETH_;
+
+    fallback() external payable {
+        require(msg.sender == _WETH_, "WE_DONT_SAVED_YOUR_ETH");
+    }
+
+    receive() external payable {
+        require(msg.sender == _WETH_, "WE_DONT_SAVED_YOUR_ETH");
+    }
+
+    constructor(address payable _weth) public {
+        _WETH_ = _weth;
+    }
+
+    function DVMSellShareCall(
+        address payable assetTo,
+        uint256,
+        uint256 baseAmount,
+        uint256 quoteAmount,
+        bytes calldata
+    ) external preventReentrant {
+        address _baseToken = IDODOV2(msg.sender)._BASE_TOKEN_();
+        address _quoteToken = IDODOV2(msg.sender)._QUOTE_TOKEN_();
+        _withdraw(assetTo, _baseToken, baseAmount, _baseToken == _WETH_);
+        _withdraw(assetTo, _quoteToken, quoteAmount, _quoteToken == _WETH_);
+    }
+
+    function _withdraw(
+        address payable to,
+        address token,
+        uint256 amount,
+        bool isETH
+    ) internal {
+        if (isETH) {
+            if (amount > 0) {
+                IWETH(_WETH_).withdraw(amount);
+                to.transfer(amount);
+            }
+        } else {
+            SafeERC20.safeTransfer(IERC20(token), to, amount);
+        }
+    }
+}