1 files changed, 113 insertions, 0 deletions
diff --git a/contracts/core/contracts/extensions/Forwarder/MixinWeth.sol b/contracts/core/contracts/extensions/Forwarder/MixinWeth.sol
new file mode 100644
index 000000000..d2814a49b
--- /dev/null
+++ b/contracts/core/contracts/extensions/Forwarder/MixinWeth.sol
@@ -0,0 +1,113 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "../../protocol/Exchange/libs/LibMath.sol";
+import "./libs/LibConstants.sol";
+import "./mixins/MWeth.sol";
+
+
+contract MixinWeth is
+    LibMath,
+    LibConstants,
+    MWeth
+{
+    /// @dev Default payabale function, this allows us to withdraw WETH
+    function ()
+        public
+        payable
+    {
+        require(
+            msg.sender == address(ETHER_TOKEN),
+            "DEFAULT_FUNCTION_WETH_CONTRACT_ONLY"
+        );
+    }
+
+    /// @dev Converts message call's ETH value into WETH.
+    function convertEthToWeth()
+        internal
+    {
+        require(
+            msg.value > 0,
+            "INVALID_MSG_VALUE"
+        );
+        ETHER_TOKEN.deposit.value(msg.value)();
+    }
+
+    /// @dev Transfers feePercentage of WETH spent on primary orders to feeRecipient.
+    ///      Refunds any excess ETH to msg.sender.
+    /// @param wethSoldExcludingFeeOrders Amount of WETH sold when filling primary orders.
+    /// @param wethSoldForZrx Amount of WETH sold when purchasing ZRX required for primary order fees.
+    /// @param feePercentage Percentage of WETH sold that will payed as fee to forwarding contract feeRecipient.
+    /// @param feeRecipient Address that will receive ETH when orders are filled.
+    function transferEthFeeAndRefund(
+        uint256 wethSoldExcludingFeeOrders,
+        uint256 wethSoldForZrx,
+        uint256 feePercentage,
+        address feeRecipient
+    )
+        internal
+    {
+        // Ensure feePercentage is less than 5%.
+        require(
+            feePercentage <= MAX_FEE_PERCENTAGE,
+            "FEE_PERCENTAGE_TOO_LARGE"
+        );
+
+        // Ensure that no extra WETH owned by this contract has been sold.
+        uint256 wethSold = safeAdd(wethSoldExcludingFeeOrders, wethSoldForZrx);
+        require(
+            wethSold <= msg.value,
+            "OVERSOLD_WETH"
+        );
+
+        // Calculate amount of WETH that hasn't been sold.
+        uint256 wethRemaining = safeSub(msg.value, wethSold);
+
+        // Calculate ETH fee to pay to feeRecipient.
+        uint256 ethFee = getPartialAmountFloor(
+            feePercentage,
+            PERCENTAGE_DENOMINATOR,
+            wethSoldExcludingFeeOrders
+        );
+
+        // Ensure fee is less than amount of WETH remaining.
+        require(
+            ethFee <= wethRemaining,
+            "INSUFFICIENT_ETH_REMAINING"
+        );
+    
+        // Do nothing if no WETH remaining
+        if (wethRemaining > 0) {
+            // Convert remaining WETH to ETH
+            ETHER_TOKEN.withdraw(wethRemaining);
+
+            // Pay ETH to feeRecipient
+            if (ethFee > 0) {
+                feeRecipient.transfer(ethFee);
+            }
+
+            // Refund remaining ETH to msg.sender.
+            uint256 ethRefund = safeSub(wethRemaining, ethFee);
+            if (ethRefund > 0) {
+                msg.sender.transfer(ethRefund);
+            }
+        }
+    }
+}