Brian/slippage iss review changes (#164)

Change logic to have modules return diff in position units and do the conversion on the SIP. Small javadoc updates.

Author: bweick

contracts/interfaces/IModuleIssuanceHookV2.sol

@@ -1,5 +1,5 @@
 /*
-    Copyright 2020 Set Labs Inc.
+    Copyright 2021 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.
@@ -50,16 +50,9 @@ interface IModuleIssuanceHookV2 {
 
     /**
      * 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  |
-     * | ------------------------------------|
+     * components array (i.e. if debt is greater than current debt position unit return negative number).
+     * Each entry in the returned arrays should index to the same component in the SetToken's components
+     * array (called using getComponents()).
      */
     function getIssuanceAdjustments(
         ISetToken _setToken,

contracts/protocol/modules/SlippageIssuanceModule.sol

@@ -34,7 +34,7 @@ import { Position } from "../lib/Position.sol";
  * @title SlippageIssuanceModule
  * @author Set Protocol
  *
- * The SlippageIssuanceModule is a module that enables users to issue and redeem SetTokens that requires a transaction that incurs slippage.
+ * The SlippageIssuanceModule is a module that enables users to issue and redeem SetTokens that requires a transaction that incurs slippage
  * in order to replicate the Set. Like the DebtIssuanceModule, module hooks are added to allow for syncing of positions, and component
  * level hooks are added to ensure positions are replicated correctly. The manager can define arbitrary issuance logic in the manager hook,
  * as well as specify issue and redeem fees. The getRequiredComponentIssuanceUnits and it's redemption counterpart now also include any
@@ -190,6 +190,8 @@ contract SlippageIssuanceModule is DebtIssuanceModule {
         );
     }
 
+    /* ============ External View Functions ============ */
+
     /**
      * Calculates the amount of each component needed to collateralize passed issue quantity plus fees of Sets as well as amount of debt
      * that will be returned to caller. Overrides inherited function to take into account position updates from pre action module hooks.
@@ -271,6 +273,8 @@ contract SlippageIssuanceModule is DebtIssuanceModule {
         );
     }
 
+    /* ============ Internal Functions ============ */
+
     /**
      * Similar to _calculateRequiredComponentIssuanceUnits but adjustments for positions that will be updated DURING the issue
      * or redeem process are added in. Adjustments can be either positive or negative, a negative debt adjustment means there
@@ -306,7 +310,7 @@ contract SlippageIssuanceModule is DebtIssuanceModule {
         uint256[] memory totalEquityUnits = new uint256[](components.length);
         uint256[] memory totalDebtUnits = new uint256[](components.length);
         for (uint256 i = 0; i < components.length; i++) {
-            // NOTE: If equityAdjustment is negative and exceeds debtUnits in absolute value this will revert
+            // NOTE: If equityAdjustment is negative and exceeds equityUnits in absolute value this will revert
             uint256 adjustedEquityUnits = equityUnits[i].toInt256().add(_equityAdjustments[i]).toUint256();
 
             // Use preciseMulCeil to round up to ensure overcollateration when small issue quantities are provided
@@ -316,7 +320,7 @@ contract SlippageIssuanceModule is DebtIssuanceModule {
                 adjustedEquityUnits.preciseMul(_quantity);
 
             // NOTE: If debtAdjustment is negative and exceeds debtUnits in absolute value this will revert
-            uint256 adjustedDebtUnits = debtUnits[i].toInt256().add(_debtAdjustments[i]).toUint256();
+            uint256 adjustedDebtUnits = debtUnits[i].toInt256().sub(_debtAdjustments[i]).toUint256();
 
             // Use preciseMulCeil to round up to ensure overcollateration when small redeem quantities are provided
             // and preciseMul to round down to ensure overcollateration when small issue quantities are provided