add multiplex TokenForEth functions to metatransactions

contracts/zero-ex/contracts/src/features/MetaTransactionsFeature.sol

@@ -15,6 +15,7 @@
 pragma solidity ^0.6.5;
 pragma experimental ABIEncoderV2;
 
+import "@0x/contracts-erc20/contracts/src/v06/IEtherTokenV06.sol";
 import "@0x/contracts-utils/contracts/src/v06/errors/LibRichErrorsV06.sol";
 import "@0x/contracts-utils/contracts/src/v06/LibBytesV06.sol";
 import "@0x/contracts-utils/contracts/src/v06/LibSafeMathV06.sol";
@@ -92,6 +93,9 @@ contract MetaTransactionsFeature is
             ")"
         );
 
+    /// @dev The WETH token contract.
+    IEtherTokenV06 private immutable WETH;
+
     /// @dev Refunds up to `msg.value` leftover ETH at the end of the call.
     modifier refundsAttachedEth() {
         _;
@@ -109,7 +113,12 @@ contract MetaTransactionsFeature is
         require(initialBalance <= address(this).balance, "MetaTransactionsFeature/ETH_LEAK");
     }
 
-    constructor(address zeroExAddress) public FixinCommon() FixinEIP712(zeroExAddress) {}
+    constructor(
+        address zeroExAddress,
+        IEtherTokenV06 weth
+    ) public FixinCommon() FixinEIP712(zeroExAddress) {
+        WETH = weth;
+    }
 
     /// @dev Initialize and register this feature.
     ///      Should be delegatecalled by `Migrate.migrate()`.
@@ -248,8 +257,12 @@ contract MetaTransactionsFeature is
             returnResult = _executeFillRfqOrderCall(state);
         } else if (state.selector == IMultiplexFeature.multiplexBatchSellTokenForToken.selector) {
             returnResult = _executeMultiplexBatchSellTokenForTokenCall(state);
+        } else if (state.selector == IMultiplexFeature.multiplexBatchSellTokenForEth.selector) {
+            returnResult = _executeMultiplexBatchSellTokenForEthCall(state);
         } else if (state.selector == IMultiplexFeature.multiplexMultiHopSellTokenForToken.selector) {
             returnResult = _executeMultiplexMultiHopSellTokenForTokenCall(state);
+        } else if (state.selector == IMultiplexFeature.multiplexMultiHopSellTokenForEth.selector) {
+            returnResult = _executeMultiplexMultiHopSellTokenForEthCall(state);
         } else {
             LibMetaTransactionsRichErrors.MetaTransactionUnsupportedFunctionError(state.hash, state.selector).rrevert();
         }
@@ -497,6 +510,46 @@ contract MetaTransactionsFeature is
             );
     }
 
+    /// @dev Execute a `IMultiplexFeature.multiplexBatchSellTokenForEth()` meta-transaction
+    ///      call by decoding the call args and translating the call to the internal
+    ///      `IMultiplexFeature._multiplexBatchSellTokenForEth()` variant, where we can override the
+    ///      msgSender address.
+    function _executeMultiplexBatchSellTokenForEthCall(ExecuteState memory state) private returns (bytes memory returnResult) {
+        IERC20TokenV06 inputToken;
+        IMultiplexFeature.BatchSellSubcall[] memory calls;
+        uint256 sellAmount;
+        uint256 minBuyAmount;
+
+        bytes memory args = _extractArgumentsFromCallData(state.mtx.callData);
+        (inputToken, calls, sellAmount, minBuyAmount) = abi.decode(
+            args,
+            (IERC20TokenV06, IMultiplexFeature.BatchSellSubcall[], uint256, uint256)
+        );
+
+        returnResult = _callSelf(
+            state.hash,
+            abi.encodeWithSelector(
+                IMultiplexFeature._multiplexBatchSell.selector,
+                IMultiplexFeature.BatchSellParams({
+                    inputToken: inputToken,
+                    outputToken: IERC20TokenV06(WETH),
+                    sellAmount: sellAmount,
+                    calls: calls,
+                    useSelfBalance: false,
+                    recipient: address(this),
+                    msgSender: state.mtx.signer
+                }),
+                minBuyAmount
+            ),
+            state.mtx.value
+        );
+
+        // Unwrap and transfer WETH
+        uint256 boughtAmount = abi.decode(returnResult, (uint256));
+        WETH.withdraw(boughtAmount);
+        _transferEth(state.mtx.signer, boughtAmount);
+    }
+
     /// @dev Execute a `IMultiplexFeature.multiplexMultiHopSellTokenForToken()` meta-transaction
     ///      call by decoding the call args and translating the call to the internal
     ///      `IMultiplexFeature._multiplexMultiHopSell()` variant, where we can override the
@@ -532,6 +585,50 @@ contract MetaTransactionsFeature is
             );
     }
 
+    /// @dev Execute a `IMultiplexFeature.multiplexMultiHopSellTokenForEth()` meta-transaction
+    ///      call by decoding the call args and translating the call to the internal
+    ///      `IMultiplexFeature._multiplexMultiHopSellTokenForEth()` variant, where we can override the
+    ///      msgSender address.
+    function _executeMultiplexMultiHopSellTokenForEthCall(ExecuteState memory state) private returns (bytes memory returnResult) {
+        address[] memory tokens;
+        IMultiplexFeature.MultiHopSellSubcall[] memory calls;
+        uint256 sellAmount;
+        uint256 minBuyAmount;
+
+        bytes memory args = _extractArgumentsFromCallData(state.mtx.callData);
+        (tokens, calls, sellAmount, minBuyAmount) = abi.decode(
+            args,
+            (address[], IMultiplexFeature.MultiHopSellSubcall[], uint256, uint256)
+        );
+
+        require(
+            tokens[tokens.length - 1] == address(WETH),
+            "MetaTransactionsFeature::multiplexMultiHopSellTokenForEth/NOT_WETH"
+        );
+
+        returnResult = _callSelf(
+            state.hash,
+            abi.encodeWithSelector(
+                IMultiplexFeature._multiplexMultiHopSell.selector,
+                IMultiplexFeature.MultiHopSellParams({
+                    tokens: tokens,
+                    sellAmount: sellAmount,
+                    calls: calls,
+                    useSelfBalance: false,
+                    recipient: address(this),
+                    msgSender: state.mtx.signer
+                }),
+                minBuyAmount
+            ),
+            state.mtx.value
+        );
+
+        // Unwrap and transfer WETH
+        uint256 boughtAmount = abi.decode(returnResult, (uint256));
+        WETH.withdraw(boughtAmount);
+        _transferEth(state.mtx.signer, boughtAmount);
+    }
+
     /// @dev Make an arbitrary internal, meta-transaction call.
     ///      Warning: Do not let unadulterated `callData` into this function.
     function _callSelf(bytes32 hash, bytes memory callData, uint256 value) private returns (bytes memory returnResult) {

contracts/zero-ex/contracts/src/features/multiplex/MultiplexFeature.sol

@@ -331,9 +331,7 @@ contract MultiplexFeature is
             );
     }
 
-    /// @dev Executes a multi-hop sell and checks that at least
+    /// @dev Executes a multi-hop sell. Internal variant.
-    ///      `minBuyAmount` of output tokens were bought. Internal
-    ///      variant.
     /// @param params Multi-hop sell parameters.
     /// @param minBuyAmount The minimum amount of output tokens that
     ///        must be bought for this function to not revert.