Combine Exchange with AssetProxyDispatcher

packages/contracts/src/contracts/current/protocol/Exchange/Exchange.sol

@@ -21,24 +21,26 @@ pragma experimental ABIEncoderV2;
 
 import "./MixinExchangeCore.sol";
 import "./MixinSignatureValidator.sol";
-import "./MixinSettlementProxy.sol";
+import "./MixinSettlement.sol";
 import "./MixinWrapperFunctions.sol";
+import "./MixinAssetProxyDispatcher.sol";
 
 contract Exchange is
     MixinExchangeCore,
     MixinSignatureValidator,
-    MixinSettlementProxy,
-    MixinWrapperFunctions
+    MixinSettlement,
+    MixinWrapperFunctions,
+    MixinAssetProxyDispatcher
 {
     string constant public VERSION = "2.0.1-alpha";
 
     function Exchange(
-        address _assetProxyDispatcher,
         bytes memory _zrxProxyData)
         public
         MixinExchangeCore()
         MixinSignatureValidator()
-        MixinSettlementProxy(_assetProxyDispatcher, _zrxProxyData)
+        MixinSettlement(_zrxProxyData)
         MixinWrapperFunctions()
+        MixinAssetProxyDispatcher()
     {}
 }

packages/contracts/src/contracts/current/protocol/Exchange/MixinAssetProxyDispatcher.sol

@@ -18,39 +18,39 @@
 
 pragma solidity ^0.4.21;
 
-import "./IAssetProxyDispatcher.sol";
-import "./IAssetProxy.sol";
+import "./mixins/MAssetProxyDispatcher.sol";
+import "../AssetProxy/IAssetProxy.sol";
 import "../../utils/Ownable/Ownable.sol";
-import "../../utils/Authorizable/Authorizable.sol";
 
-contract AssetProxyDispatcher is
+contract MixinAssetProxyDispatcher is
     Ownable,
-    Authorizable,
-    IAssetProxyDispatcher
+    MAssetProxyDispatcher
 {
     // Mapping from Asset Proxy Id's to their respective Asset Proxy
     mapping (uint8 => IAssetProxy) public assetProxies;
 
-    /// @dev Transfers assets. Either succeeds or throws.
+    /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
     /// @param assetMetadata Byte array encoded for the respective asset proxy.
     /// @param from Address to transfer token from.
     /// @param to Address to transfer token to.
     /// @param amount Amount of token to transfer.
-    function transferFrom(
-        bytes assetMetadata,
+    function dispatchTransferFrom(
+        bytes memory assetMetadata,
         address from,
         address to,
         uint256 amount)
-        external
-        onlyAuthorized
+        internal
     {
-        // Lookup asset proxy
-        require(assetMetadata.length >= 1);
-        uint8 assetProxyId = uint8(assetMetadata[0]);
-        IAssetProxy assetProxy = assetProxies[assetProxyId];
+        // Do nothing if no amount should be transferred.
+        if (amount > 0) {
+            // Lookup asset proxy
+            require(assetMetadata.length >= 1);
+            uint8 assetProxyId = uint8(assetMetadata[0]);
+            IAssetProxy assetProxy = assetProxies[assetProxyId];
 
-        // transferFrom will either succeed or throw.
-        assetProxy.transferFrom(assetMetadata, from, to, amount);
+            // transferFrom will either succeed or throw.
+            assetProxy.transferFrom(assetMetadata, from, to, amount);
+        }
     }
 
     /// @dev Registers an asset proxy to an asset proxy id.

packages/contracts/src/contracts/current/protocol/Exchange/MixinSettlement.sol

@@ -20,24 +20,18 @@ pragma solidity ^0.4.21;
 pragma experimental ABIEncoderV2;
 
 import "./mixins/MSettlement.sol";
+import "./mixins/MAssetProxyDispatcher.sol";
 import "./LibPartialAmount.sol";
-import "../AssetProxyDispatcher/IAssetProxy.sol";
+import "../AssetProxy/IAssetProxy.sol";
 
 /// @dev Provides MixinSettlement
-contract MixinSettlementProxy is
+contract MixinSettlement is
     MSettlement,
+    MAssetProxyDispatcher,
     LibPartialAmount
 {
-    IAssetProxy ASSET_PROXY_DISPATCHER;
     bytes ZRX_PROXY_DATA;
 
-    function assetProxyDispatcher()
-        public view
-        returns (address)
-    {
-        return address(ASSET_PROXY_DISPATCHER);
-    }
-
     function zrxProxyData()
         external view
         returns (bytes memory)
@@ -45,12 +39,9 @@ contract MixinSettlementProxy is
         return ZRX_PROXY_DATA;
     }
 
-    function MixinSettlementProxy(
-        address _assetProxyDispatcher,
-        bytes memory _zrxProxyData)
+    function MixinSettlement(bytes memory _zrxProxyData)
         public
     {
-        ASSET_PROXY_DISPATCHER = IAssetProxy(_assetProxyDispatcher);
         ZRX_PROXY_DATA = _zrxProxyData;
     }
 
@@ -66,38 +57,32 @@ contract MixinSettlementProxy is
         )
     {
         makerAssetFilledAmount = getPartialAmount(takerAssetFilledAmount, order.takerAssetAmount, order.makerAssetAmount);
-        ASSET_PROXY_DISPATCHER.transferFrom(
+        dispatchTransferFrom(
             order.makerAssetData,
             order.makerAddress,
             takerAddress,
             makerAssetFilledAmount
         );
-        ASSET_PROXY_DISPATCHER.transferFrom(
+        dispatchTransferFrom(
             order.takerAssetData,
             takerAddress,
             order.makerAddress,
             takerAssetFilledAmount
         );
-        if (order.feeRecipientAddress != address(0)) {
-            if (order.makerFee > 0) {
-                makerFeePaid = getPartialAmount(takerAssetFilledAmount, order.takerAssetAmount, order.makerFee);
-                ASSET_PROXY_DISPATCHER.transferFrom(
-                    ZRX_PROXY_DATA,
-                    order.makerAddress,
-                    order.feeRecipientAddress,
-                    makerFeePaid
-                );
-            }
-            if (order.takerFee > 0) {
-                takerFeePaid = getPartialAmount(takerAssetFilledAmount, order.takerAssetAmount, order.takerFee);
-                ASSET_PROXY_DISPATCHER.transferFrom(
-                    ZRX_PROXY_DATA,
-                    takerAddress,
-                    order.feeRecipientAddress,
-                    takerFeePaid
-                );
-            }
-        }
+        makerFeePaid = getPartialAmount(takerAssetFilledAmount, order.takerAssetAmount, order.makerFee);
+        dispatchTransferFrom(
+            ZRX_PROXY_DATA,
+            order.makerAddress,
+            order.feeRecipientAddress,
+            makerFeePaid
+        );
+        takerFeePaid = getPartialAmount(takerAssetFilledAmount, order.takerAssetAmount, order.takerFee);
+        dispatchTransferFrom(
+            ZRX_PROXY_DATA,
+            takerAddress,
+            order.feeRecipientAddress,
+            takerFeePaid
+        );
         return (makerAssetFilledAmount, makerFeePaid, takerFeePaid);
     }
 }

packages/contracts/src/contracts/current/protocol/Exchange/mixins/MAssetProxyDispatcher.sol

@@ -18,15 +18,7 @@
 
 pragma solidity ^0.4.21;
 
-import "../../utils/Ownable/IOwnable.sol";
-import "../../utils/Authorizable/IAuthorizable.sol";
-import "./IAssetProxy.sol";
-
-contract IAssetProxyDispatcher is
-    IOwnable,
-    IAuthorizable,
-    IAssetProxy
-{
+contract MAssetProxyDispatcher {
 
     // Logs registration of new asset proxy
     event AssetProxySet(
@@ -35,6 +27,18 @@ contract IAssetProxyDispatcher is
         address oldAssetProxy
     );
 
+    /// @dev Forwards arguments to assetProxy and calls `transferFrom`. Either succeeds or throws.
+    /// @param assetMetadata Byte array encoded for the respective asset proxy.
+    /// @param from Address to transfer token from.
+    /// @param to Address to transfer token to.
+    /// @param amount Amount of token to transfer.
+    function dispatchTransferFrom(
+        bytes memory assetMetadata,
+        address from,
+        address to,
+        uint256 amount)
+        internal;
+
     /// @dev Registers an asset proxy to an asset proxy id.
     ///      An id can only be assigned to a single proxy at a given time,
     ///      however, an asset proxy may be registered to multiple ids.