feat(extension): Add support for alternative Flashloan providers to migration extension (#167)

* Add morpho flashloan implementation

* Balancer flashloan option

* Adjust subsidy amounts

* Rename old migrate method to migrateAave

* Rename to MigrationExtension

* Reorder imports

* Add morpho and balancer address as constructor args

Author: ckoopmann

contracts/adapters/AaveMigrationExtension.sol renamed to contracts/adapters/MigrationExtension.sol

@@ -25,6 +25,8 @@ import { SafeCast } from "@openzeppelin/contracts/utils/SafeCast.sol";
 import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
 import { SafeMath } from "@openzeppelin/contracts/math/SafeMath.sol";
 
+import { IBalancerVault } from "../interfaces/IBalancerVault.sol";
+import { IMorpho } from "../interfaces/IMorpho.sol";
 import { FlashLoanSimpleReceiverBase } from "../lib/FlashLoanSimpleReceiverBase.sol";
 import { IPoolAddressesProvider } from "../interfaces/IPoolAddressesProvider.sol";
 
@@ -39,7 +41,7 @@ import { ITradeModule } from "../interfaces/ITradeModule.sol";
 import { PreciseUnitMath } from "../lib/PreciseUnitMath.sol";
 
 /**
- * @title AaveMigrationExtension
+ * @title MigrationExtension
  * @author Index Coop
  * @notice This extension facilitates the migration of a SetToken's position from an unwrapped collateral
  * asset to another SetToken that consists solely of Aave's wrapped collateral asset. The migration is
@@ -49,7 +51,7 @@ import { PreciseUnitMath } from "../lib/PreciseUnitMath.sol";
  * redeeming any excess wrapped SetToken. This process is specifically designed to efficiently migrate
  * the SetToken's collateral using only the TradeModule on the SetToken.
  */
-contract AaveMigrationExtension is BaseExtension, FlashLoanSimpleReceiverBase, IERC721Receiver {
+contract MigrationExtension is BaseExtension, FlashLoanSimpleReceiverBase, IERC721Receiver {
     using PreciseUnitMath for uint256;
     using SafeCast for int256;
     using SafeERC20 for IERC20;
@@ -81,13 +83,15 @@ contract AaveMigrationExtension is BaseExtension, FlashLoanSimpleReceiverBase, I
     ITradeModule public immutable tradeModule;
     IDebtIssuanceModule public immutable issuanceModule;
     INonfungiblePositionManager public immutable nonfungiblePositionManager;
+    IMorpho public immutable morpho;
+    IBalancerVault public immutable balancer;
 
     uint256[] public tokenIds; // UniV3 LP Token IDs
 
     /* ============ Constructor ============ */
 
     /**
-     * @notice Initializes the AaveMigrationExtension with immutable migration variables.
+     * @notice Initializes the MigrationExtension with immutable migration variables.
      * @param _manager BaseManager contract for managing the SetToken's operations and permissions.
      * @param _underlyingToken Address of the underlying token to be migrated.
      * @param _aaveToken Address of Aave's wrapped collateral asset.
@@ -105,7 +109,9 @@ contract AaveMigrationExtension is BaseExtension, FlashLoanSimpleReceiverBase, I
         ITradeModule _tradeModule,
         IDebtIssuanceModule _issuanceModule,
         INonfungiblePositionManager _nonfungiblePositionManager,
-        IPoolAddressesProvider _addressProvider
+        IPoolAddressesProvider _addressProvider,
+        IMorpho _morpho,
+        IBalancerVault _balancer
     ) 
         public
         BaseExtension(_manager)
@@ -119,6 +125,8 @@ contract AaveMigrationExtension is BaseExtension, FlashLoanSimpleReceiverBase, I
         tradeModule = _tradeModule;
         issuanceModule = _issuanceModule;
         nonfungiblePositionManager = _nonfungiblePositionManager;
+        morpho = _morpho;
+        balancer = _balancer;
     }
 
     /* ========== External Functions ========== */
@@ -258,12 +266,13 @@ contract AaveMigrationExtension is BaseExtension, FlashLoanSimpleReceiverBase, I
     /**
      * @notice OPERATOR ONLY: Migrates a SetToken's position from an unwrapped collateral asset to another SetToken 
      * that consists solely of Aave's wrapped collateral asset
+     * using Aave Flashloan
      * @param _decodedParams The decoded migration parameters.
      * @param _underlyingLoanAmount The amount of unwrapped collateral asset to be borrowed via flash loan.
      * @param _maxSubsidy The maximum amount of unwrapped collateral asset to be transferred to the Extension as a subsidy.
      * @return underlyingOutputAmount The amount of unwrapped collateral asset returned to the operator.
      */
-    function migrate(
+    function migrateAave(
         DecodedParams memory _decodedParams,
         uint256 _underlyingLoanAmount,
         uint256 _maxSubsidy
@@ -293,6 +302,109 @@ contract AaveMigrationExtension is BaseExtension, FlashLoanSimpleReceiverBase, I
         underlyingOutputAmount = _returnExcessUnderlying();
     }
 
+    /**
+     * @notice OPERATOR ONLY: Migrates a SetToken's position from an unwrapped collateral asset to another SetToken 
+     * that consists solely of Aave's wrapped collateral asset
+     * using Balancer Flashloan
+     * @param _decodedParams The decoded migration parameters.
+     * @param _underlyingLoanAmount The amount of unwrapped collateral asset to be borrowed via flash loan.
+     * @param _maxSubsidy The maximum amount of unwrapped collateral asset to be transferred to the Extension as a subsidy.
+     * @return underlyingOutputAmount The amount of unwrapped collateral asset returned to the operator.
+     */
+    function migrateBalancer(
+        DecodedParams memory _decodedParams,
+        uint256 _underlyingLoanAmount,
+        uint256 _maxSubsidy
+    )
+        external
+        onlyOperator
+        returns (uint256 underlyingOutputAmount)
+    {
+        // Subsidize the migration
+        if (_maxSubsidy > 0) {
+            underlyingToken.transferFrom(msg.sender, address(this), _maxSubsidy);
+        }
+
+        // Encode migration parameters for flash loan callback
+        bytes memory params = abi.encode(_decodedParams);
+        address[] memory tokens = new address[](1);
+        tokens[0] = address(underlyingToken);
+        uint256[] memory amounts = new  uint256[](1);
+        amounts[0] = _underlyingLoanAmount;
+
+        // Request flash loan for the underlying token
+        balancer.flashLoan(address(this), tokens, amounts, params);
+
+        // Return remaining underlying token to the operator
+        underlyingOutputAmount = _returnExcessUnderlying();
+    }
+
+    /**
+     * @dev Callback function for Balancer flashloan
+    */
+    function receiveFlashLoan(
+        IERC20[] memory tokens,
+        uint256[] memory amounts,
+        uint256[] memory feeAmounts,
+        bytes memory params
+    ) external {
+        require(msg.sender == address(balancer));
+        // Decode parameters and migrate
+        DecodedParams memory decodedParams = abi.decode(params, (DecodedParams));
+        _migrate(decodedParams);
+
+        underlyingToken.transfer(address(balancer), amounts[0] + feeAmounts[0]);
+    }
+
+
+    /**
+     * @notice OPERATOR ONLY: Migrates a SetToken's position from an unwrapped collateral asset to another SetToken 
+     * that consists solely of Aave's wrapped collateral asset
+     * using Morpho Flashloan
+     * @param _decodedParams The decoded migration parameters.
+     * @param _underlyingLoanAmount The amount of unwrapped collateral asset to be borrowed via flash loan.
+     * @param _maxSubsidy The maximum amount of unwrapped collateral asset to be transferred to the Extension as a subsidy.
+     * @return underlyingOutputAmount The amount of unwrapped collateral asset returned to the operator.
+     */
+    function migrateMorpho(
+        DecodedParams memory _decodedParams,
+        uint256 _underlyingLoanAmount,
+        uint256 _maxSubsidy
+    )
+        external
+        onlyOperator
+        returns (uint256 underlyingOutputAmount)
+    {
+        // Subsidize the migration
+        if (_maxSubsidy > 0) {
+            underlyingToken.transferFrom(msg.sender, address(this), _maxSubsidy);
+        }
+
+        // Encode migration parameters for flash loan callback
+        bytes memory params = abi.encode(_decodedParams);
+
+        // Request flash loan for the underlying token
+        morpho.flashLoan(address(underlyingToken), _underlyingLoanAmount, params);
+
+        // Return remaining underlying token to the operator
+        underlyingOutputAmount = _returnExcessUnderlying();
+    }
+
+    /**
+     * @dev Callback function for Morpho Flashloan
+    */
+    function onMorphoFlashLoan(uint256 assets, bytes calldata params) external 
+    {
+        require(msg.sender == address(morpho), "MigrationExtension: invalid flashloan sender");
+
+        // Decode parameters and migrate
+        DecodedParams memory decodedParams = abi.decode(params, (DecodedParams));
+        _migrate(decodedParams);
+
+        underlyingToken.approve(address(morpho), assets);
+    }
+
+
     /**
      * @dev Callback function for Aave V3 flash loan, executed post-loan. It decodes the provided parameters, conducts the migration, and repays the flash loan.
      * @param amount The amount borrowed.

contracts/interfaces/IBalancerVault.sol

@@ -0,0 +1,4 @@
+pragma solidity 0.6.10;
+interface IBalancerVault {
+    function flashLoan(address recipient, address[] memory tokens, uint256[] memory amounts, bytes memory userData) external;
+}

contracts/interfaces/IMorpho.sol

@@ -0,0 +1,151 @@
+// SPDX-License-bytes32entifier: UNLICENSED
+pragma solidity 0.6.10;
+pragma experimental ABIEncoderV2;
+
+interface IMorpho {
+
+    struct Authorization {
+        address authorizer;
+        address authorized;
+        bool isAuthorized;
+        uint256 nonce;
+        uint256 deadline;
+    }
+
+    struct MarketParams {
+        address loanToken;
+        address collateralToken;
+        address oracle;
+        address irm;
+        uint256 lltv;
+    }
+
+    struct Signature {
+        uint8 v;
+        bytes32 r;
+        bytes32 s;
+    }
+
+    event AccrueInterest(bytes32 indexed id, uint256 prevBorrowRate, uint256 interest, uint256 feeShares);
+    event Borrow(
+        bytes32 indexed id,
+        address caller,
+        address indexed onBehalf,
+        address indexed receiver,
+        uint256 assets,
+        uint256 shares
+    );
+    event CreateMarket(bytes32 indexed id, MarketParams marketParams);
+    event EnableIrm(address indexed irm);
+    event EnableLltv(uint256 lltv);
+    event FlashLoan(address indexed caller, address indexed token, uint256 assets);
+    event IncrementNonce(address indexed caller, address indexed authorizer, uint256 usedNonce);
+    event Liquidate(
+        bytes32 indexed id,
+        address indexed caller,
+        address indexed borrower,
+        uint256 repaidAssets,
+        uint256 repaidShares,
+        uint256 seizedAssets,
+        uint256 badDebtAssets,
+        uint256 badDebtShares
+    );
+    event Repay(bytes32 indexed id, address indexed caller, address indexed onBehalf, uint256 assets, uint256 shares);
+    event SetAuthorization(
+        address indexed caller, address indexed authorizer, address indexed authorized, bool newIsAuthorized
+    );
+    event SetFee(bytes32 indexed id, uint256 newFee);
+    event SetFeeRecipient(address indexed newFeeRecipient);
+    event SetOwner(address indexed newOwner);
+    event Supply(bytes32 indexed id, address indexed caller, address indexed onBehalf, uint256 assets, uint256 shares);
+    event SupplyCollateral(bytes32 indexed id, address indexed caller, address indexed onBehalf, uint256 assets);
+    event Withdraw(
+        bytes32 indexed id,
+        address caller,
+        address indexed onBehalf,
+        address indexed receiver,
+        uint256 assets,
+        uint256 shares
+    );
+    event WithdrawCollateral(
+        bytes32 indexed id, address caller, address indexed onBehalf, address indexed receiver, uint256 assets
+    );
+
+
+    function DOMAIN_SEPARATOR() external view returns (bytes32);
+    function accrueInterest(MarketParams memory marketParams) external;
+    function borrow(
+        MarketParams memory marketParams,
+        uint256 assets,
+        uint256 shares,
+        address onBehalf,
+        address receiver
+    ) external returns (uint256, uint256);
+    function createMarket(MarketParams memory marketParams) external;
+    function enableIrm(address irm) external;
+    function enableLltv(uint256 lltv) external;
+    function extSloads(bytes32[] memory slots) external view returns (bytes32[] memory res);
+    function feeRecipient() external view returns (address);
+    function flashLoan(address token, uint256 assets, bytes memory data) external;
+    function idToMarketParams(bytes32)
+        external
+        view
+        returns (address loanToken, address collateralToken, address oracle, address irm, uint256 lltv);
+    function isAuthorized(address, address) external view returns (bool);
+    function isIrmEnabled(address) external view returns (bool);
+    function isLltvEnabled(uint256) external view returns (bool);
+    function liquidate(
+        MarketParams memory marketParams,
+        address borrower,
+        uint256 seizedAssets,
+        uint256 repaidShares,
+        bytes memory data
+    ) external returns (uint256, uint256);
+    function market(bytes32)
+        external
+        view
+        returns (
+            uint128 totalSupplyAssets,
+            uint128 totalSupplyShares,
+            uint128 totalBorrowAssets,
+            uint128 totalBorrowShares,
+            uint128 lastUpdate,
+            uint128 fee
+        );
+    function nonce(address) external view returns (uint256);
+    function owner() external view returns (address);
+    function position(bytes32, address)
+        external
+        view
+        returns (uint256 supplyShares, uint128 borrowShares, uint128 collateral);
+    function repay(
+        MarketParams memory marketParams,
+        uint256 assets,
+        uint256 shares,
+        address onBehalf,
+        bytes memory data
+    ) external returns (uint256, uint256);
+    function setAuthorization(address authorized, bool newIsAuthorized) external;
+    function setAuthorizationWithSig(Authorization memory authorization, Signature memory signature) external;
+    function setFee(MarketParams memory marketParams, uint256 newFee) external;
+    function setFeeRecipient(address newFeeRecipient) external;
+    function setOwner(address newOwner) external;
+    function supply(
+        MarketParams memory marketParams,
+        uint256 assets,
+        uint256 shares,
+        address onBehalf,
+        bytes memory data
+    ) external returns (uint256, uint256);
+    function supplyCollateral(MarketParams memory marketParams, uint256 assets, address onBehalf, bytes memory data)
+        external;
+    function withdraw(
+        MarketParams memory marketParams,
+        uint256 assets,
+        uint256 shares,
+        address onBehalf,
+        address receiver
+    ) external returns (uint256, uint256);
+    function withdrawCollateral(MarketParams memory marketParams, uint256 assets, address onBehalf, address receiver)
+        external;
+}