Renamed MixinExchange to MixinExchangeManager and added documentation

contracts/staking/contracts/src/Staking.sol

@@ -19,7 +19,7 @@
 pragma solidity ^0.5.9;
 
 import "./interfaces/IStaking.sol";
-import "./core/MixinExchange.sol";
+import "./core/MixinExchangeManager.sol";
 import "./core/MixinZrxVault.sol";
 import "./core/MixinRewardVault.sol";
 import "./core/MixinScheduler.sol";
@@ -38,7 +38,7 @@ contract Staking is
     MixinScheduler,
     MixinRewardVault,
     MixinZrxVault,
-    MixinExchange,
+    MixinExchangeManager,
     MixinStakeBalances,
     MixinPools,
     MixinRewards,

contracts/staking/contracts/src/core/MixinExchangeManager.sol

@@ -18,20 +18,25 @@
 
 pragma solidity ^0.5.5;
 
+import "@0x/contracts-utils/contracts/src/Authorizable.sol";
 import "../interfaces/IStakingEvents.sol";
 import "../immutable/MixinConstants.sol";
 import "../immutable/MixinStorage.sol";
 
 
-contract MixinExchange is
+contract MixinExchangeManager is
+    Authorizable,
     IStakingEvents,
     MixinConstants,
     MixinStorage
 {
 
-    /// @dev This mixin contains logic for managing exchanges
-    /// 
+    /// @dev This mixin contains logic for managing exchanges.
+    /// Any exchange contract that connects to the staking contract
+    /// must be added here. When an exchange contract is deprecated
+    /// then it should be removed.
 
+    /// @dev Asserts that the call is coming from a valid exchange.
     modifier onlyExchange() {
         require(
             isValidExchangeAddress(msg.sender),
@@ -40,9 +45,11 @@ contract MixinExchange is
         _;
     }
 
+    /// @dev Adds a new exchange address
+    /// @param addr Address of exchange contract to add
     function addExchangeAddress(address addr)
         external
-        // @TODO - Only by 0x multi-sig
+        onlyOwner
     {
         require(
             !validExchanges[addr],
@@ -52,9 +59,11 @@ contract MixinExchange is
         emit ExchangeAdded(addr);
     }
 
+    /// @dev Removes an existing exchange address
+    /// @param addr Address of exchange contract to remove
     function removeExchangeAddress(address addr)
         external
-        // @TODO - Only by 0x multi-sig
+        onlyOwner
     {
         require(
             validExchanges[addr],
@@ -64,6 +73,8 @@ contract MixinExchange is
         emit ExchangeRemoved(addr);
     }
 
+    /// @dev Returns true iff the address is a valid exchange
+    /// @param addr Address of exchange contract
     function isValidExchangeAddress(address addr)
         public
         view

contracts/staking/contracts/src/core/MixinFees.sol

@@ -26,7 +26,7 @@ import "../interfaces/IStakingEvents.sol";
 import "./MixinStakeBalances.sol";
 import "./MixinScheduler.sol";
 import "./MixinPools.sol";
-import "./MixinExchange.sol";
+import "./MixinExchangeManager.sol";
 import "./MixinRewardVault.sol";
 import "../interfaces/IStructs.sol";
 
@@ -37,7 +37,7 @@ contract MixinFees is
     MixinStorage,
     MixinScheduler,
     MixinRewardVault,
-    MixinExchange,
+    MixinExchangeManager,
     MixinStakeBalances,
     MixinPools
 {

contracts/staking/contracts/test/TestSignatureValidator.sol

@@ -1,40 +0,0 @@
-/*
-
-  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 ^0.5.5;
-pragma experimental ABIEncoderV2;
-
-import "@0x/contracts-exchange-libs/contracts/src/LibEIP712ExchangeDomain.sol";
-import "../src/MixinSignatureValidator.sol";
-import "../src/MixinTransactions.sol";
-import "../src/MixinExchangeRichErrors.sol";
-
-
-contract TestSignatureValidator is
-    LibEIP712ExchangeDomain,
-    MixinSignatureValidator,
-    MixinTransactions,
-    MixinExchangeRichErrors
-{
-
-    // solhint-disable no-empty-blocks
-    constructor (uint256 chainId)
-        public
-        LibEIP712ExchangeDomain(chainId, address(0))
-    {}
-}