Brian/slippage issuance (#162)

Issuance module that allows for issue/redeem of assets that may be susceptible to slippage. Allows user to set slippage limit similar to a Uniswap trade. Additional functionality added to helper functions to give better estimates of required components by taking into account positional changes during issue/redeem.

Author: bweick

contracts/interfaces/IModuleIssuanceHookV2.sol

@@ -0,0 +1,92 @@
+/*
+    Copyright 2020 Set Labs Inc.
+
+    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.
+
+    SPDX-License-Identifier: Apache License, Version 2.0
+*/
+pragma solidity 0.6.10;
+
+import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+
+import { ISetToken } from "./ISetToken.sol";
+
+
+/**
+ * CHANGELOG:
+ *      - Added a module level issue hook that can be used to set state ahead of component level
+ *        issue hooks
+ *      - Added view function that return expected positional adjustments during issue/redeem to
+ *        the issuance module in order to give more accurate token flow information
+ */
+interface IModuleIssuanceHookV2 {
+
+    function moduleIssueHook(ISetToken _setToken, uint256 _setTokenQuantity) external;
+    function moduleRedeemHook(ISetToken _setToken, uint256 _setTokenQuantity) external;
+    
+    function componentIssueHook(
+        ISetToken _setToken,
+        uint256 _setTokenQuantity,
+        IERC20 _component,
+        bool _isEquity
+    ) external;
+
+    function componentRedeemHook(
+        ISetToken _setToken,
+        uint256 _setTokenQuantity,
+        IERC20 _component,
+        bool _isEquity
+    ) external;
+
+    /**
+     * Adjustments should return the NET CHANGE in POSITION UNITS for each component in the SetToken's
+     * components array. Each entry in the returned arrays should index to the same component in the
+     * SetToken's components array (called using getComponents()). Directional adjustments should be made
+     * according to the following table (i.e. returning a negative debt number means debt is reduced during
+     * issue/redeem):
+     * | ------------------------------------|
+     * | Type    |  Positive |  Negative     |
+     * | -----   |---------- | --------------|
+     * | Equity  | Add Equity| Equity Reduced|
+     * | Debt    | Add Debt  | Debt Reduced  |
+     * | ------------------------------------|
+     */
+    function getIssuanceAdjustments(
+        ISetToken _setToken,
+        uint256 _setTokenQuantity
+    )
+        external
+        view
+        returns (int256[] memory, int256[] memory);
+
+    /**
+     * Adjustments should return the NET CHANGE in POSITION UNITS for each component in the SetToken's
+     * components array. Each entry in the returned arrays should index to the same component in the
+     * SetToken's components array (called using getComponents()). Directional adjustments should be made
+     * according to the following table (i.e. returning a negative debt number means debt is reduced during
+     * issue/redeem):
+     * | ------------------------------------|
+     * | Type    |  Positive |  Negative     |
+     * | -----   |---------- | --------------|
+     * | Equity  | Add Equity| Equity Reduced|
+     * | Debt    | Add Debt  | Debt Reduced  |
+     * | ------------------------------------|
+     */
+    function getRedemptionAdjustments(
+        ISetToken _setToken,
+        uint256 _setTokenQuantity
+    )
+        external
+        view
+        returns (int256[] memory, int256[] memory);
+}

contracts/mocks/protocol/module/DebtModuleMock.sol

@@ -44,6 +44,8 @@ contract DebtModuleMock is ModuleBase {
     address public module;
     bool public moduleIssueHookCalled;
     bool public moduleRedeemHookCalled;
+    mapping(address=>int256) public equityIssuanceAdjustment;
+    mapping(address=>int256) public debtIssuanceAdjustment;
 
     constructor(IController _controller, address _module) public ModuleBase(_controller) {
         module = _module;
@@ -53,6 +55,14 @@ contract DebtModuleMock is ModuleBase {
         _setToken.editExternalPosition(_token, address(this), _amount.toInt256().mul(-1), "");
     }
 
+    function addEquityIssuanceAdjustment(address _token, int256 _amount) external {
+        equityIssuanceAdjustment[_token] = _amount;
+    }
+
+    function addDebtIssuanceAdjustment(address _token, int256 _amount) external {
+        debtIssuanceAdjustment[_token] = _amount;
+    }
+
     function moduleIssueHook(ISetToken /*_setToken*/, uint256 /*_setTokenQuantity*/) external { moduleIssueHookCalled = true; }
     function moduleRedeemHook(ISetToken /*_setToken*/, uint256 /*_setTokenQuantity*/) external { moduleRedeemHookCalled = true; }
 
@@ -82,6 +92,45 @@ contract DebtModuleMock is ModuleBase {
         _setToken.invokeTransfer(_component, address(this), notionalAmount);
     }
 
+
+    function getIssuanceAdjustments(
+        ISetToken _setToken,
+        uint256 /* _setTokenQuantity */
+    )
+        external
+        view
+        returns (int256[] memory, int256[] memory)
+    {
+        address[] memory components = _setToken.getComponents();
+        int256[] memory equityAdjustments = new int256[](components.length);
+        int256[] memory debtAdjustments = new int256[](components.length);
+        for(uint256 i = 0; i < components.length; i++) {
+            equityAdjustments[i] = equityIssuanceAdjustment[components[i]];
+            debtAdjustments[i] = debtIssuanceAdjustment[components[i]];
+        }
+
+        return (equityAdjustments, debtAdjustments);
+    }
+
+    function getRedemptionAdjustments(
+        ISetToken _setToken,
+        uint256 /* _setTokenQuantity */
+    )
+        external
+        view
+        returns (int256[] memory, int256[] memory)
+    {
+        address[] memory components = _setToken.getComponents();
+        int256[] memory equityAdjustments = new int256[](components.length);
+        int256[] memory debtAdjustments = new int256[](components.length);
+        for(uint256 i = 0; i < components.length; i++) {
+            equityAdjustments[i] = equityIssuanceAdjustment[components[i]];
+            debtAdjustments[i] = debtIssuanceAdjustment[components[i]];
+        }
+
+        return (equityAdjustments, debtAdjustments);
+    }
+
     function initialize(ISetToken _setToken) external {
         _setToken.initializeModule();
         IDebtIssuanceModule(module).registerToIssuanceModule(_setToken);

contracts/protocol/modules/DebtIssuanceModule.sol

@@ -417,6 +417,7 @@ contract DebtIssuanceModule is ModuleBase, ReentrancyGuard {
     )
         external
         view
+        virtual
         returns (address[] memory, uint256[] memory, uint256[] memory)
     {
         (