Implement osToken flashloans

abi/Errors.json

@@ -39,6 +39,11 @@
     "name": "ExitRequestNotProcessed",
     "type": "error"
   },
+  {
+    "inputs": [],
+    "name": "FlashLoanFailed",
+    "type": "error"
+  },
   {
     "inputs": [],
     "name": "HarvestFailed",

abi/IOsTokenFlashLoanRecipient.json

@@ -0,0 +1,20 @@
+[
+  {
+    "inputs": [
+      {
+        "internalType": "uint256",
+        "name": "amount",
+        "type": "uint256"
+      },
+      {
+        "internalType": "bytes",
+        "name": "userData",
+        "type": "bytes"
+      }
+    ],
+    "name": "receiveFlashLoan",
+    "outputs": [],
+    "stateMutability": "nonpayable",
+    "type": "function"
+  }
+]

abi/IOsTokenFlashLoans.json

@@ -0,0 +1,44 @@
+[
+  {
+    "anonymous": false,
+    "inputs": [
+      {
+        "indexed": true,
+        "internalType": "address",
+        "name": "recipient",
+        "type": "address"
+      },
+      {
+        "indexed": false,
+        "internalType": "uint256",
+        "name": "amount",
+        "type": "uint256"
+      }
+    ],
+    "name": "OsTokenFlashLoan",
+    "type": "event"
+  },
+  {
+    "inputs": [
+      {
+        "internalType": "address",
+        "name": "recipient",
+        "type": "address"
+      },
+      {
+        "internalType": "uint256",
+        "name": "amount",
+        "type": "uint256"
+      },
+      {
+        "internalType": "bytes",
+        "name": "userData",
+        "type": "bytes"
+      }
+    ],
+    "name": "flashLoan",
+    "outputs": [],
+    "stateMutability": "nonpayable",
+    "type": "function"
+  }
+]

abi/IOsTokenVaultEscrow.json

@@ -254,7 +254,13 @@
       }
     ],
     "name": "claimExitedAssets",
-    "outputs": [],
+    "outputs": [
+      {
+        "internalType": "uint256",
+        "name": "claimedAssets",
+        "type": "uint256"
+      }
+    ],
     "stateMutability": "nonpayable",
     "type": "function"
   },

contracts/interfaces/IOsTokenFlashLoanRecipient.sol

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: BUSL-1.1
+
+pragma solidity ^0.8.22;
+
+/**
+ * @title IOsTokenFlashLoanRecipient
+ * @author StakeWise
+ * @notice Interface for OsTokenFlashLoanRecipient contract
+ */
+interface IOsTokenFlashLoanRecipient {
+  /**
+   * @notice Receive flash loan hook
+   * @param amount The osToken flash loan amount
+   * @param userData Arbitrary data passed to the hook
+   */
+  function receiveFlashLoan(uint256 amount, bytes memory userData) external;
+}

contracts/interfaces/IOsTokenFlashLoans.sol

@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: BUSL-1.1
+
+pragma solidity ^0.8.22;
+
+/**
+ * @title IOsTokenFlashLoans
+ * @author StakeWise
+ * @notice Interface for OsTokenFlashLoans contract
+ */
+interface IOsTokenFlashLoans {
+  /**
+   * @notice Event emitted on position creation
+   * @param recipient The address of the recipient
+   * @param amount The flashLoan osToken shares amount
+   */
+  event OsTokenFlashLoan(address indexed recipient, uint256 amount);
+
+  /**
+   * @notice Flash loan OsToken shares
+   * @param recipient The address of the recipient
+   * @param amount The flashLoan osToken shares amount
+   * @param userData Arbitrary data passed to the `IOsTokenFlashLoanRecipient.receiveFlashLoan` function
+   */
+  function flashLoan(address recipient, uint256 amount, bytes memory userData) external;
+}

contracts/interfaces/IOsTokenVaultEscrow.sol

@@ -182,12 +182,13 @@ interface IOsTokenVaultEscrow is IMulticall {
    * @param vault The address of the vault
    * @param exitPositionTicket The exit position ticket
    * @param osTokenShares The amount of osToken shares to burn
+   * @return claimedAssets The amount of assets claimed
    */
   function claimExitedAssets(
     address vault,
     uint256 exitPositionTicket,
     uint256 osTokenShares
-  ) external;
+  ) external returns (uint256 claimedAssets);
 
   /**
    * @notice Liquidates the osToken shares

contracts/libraries/Errors.sol

@@ -54,4 +54,5 @@ library Errors {
   error InvalidWithdrawalCredentials();
   error EigenPodNotFound();
   error InvalidQueuedShares();
+  error FlashLoanFailed();
 }

contracts/tokens/OsTokenFlashLoans.sol

@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: BUSL-1.1
+
+pragma solidity ^0.8.22;
+
+import {IERC20} from '@openzeppelin/contracts/token/ERC20/IERC20.sol';
+import {ReentrancyGuard} from '@openzeppelin/contracts/utils/ReentrancyGuard.sol';
+import {IOsTokenFlashLoans} from '../interfaces/IOsTokenFlashLoans.sol';
+import {IOsTokenFlashLoanRecipient} from '../interfaces/IOsTokenFlashLoanRecipient.sol';
+import {IOsToken} from '../interfaces/IOsToken.sol';
+import {Errors} from '../libraries/Errors.sol';
+
+/**
+ * @title OsTokenFlashLoans
+ * @author StakeWise
+ * @notice Handles OsToken flash loans
+ */
+contract OsTokenFlashLoans is ReentrancyGuard, IOsTokenFlashLoans {
+  uint256 private constant _maxFlashLoanAmount = 1_000_000 ether;
+  address private immutable _osToken;
+
+  /**
+   * @dev Constructor
+   * @param osToken The address of the OsToken contract
+   */
+  constructor(address osToken) ReentrancyGuard() {
+    _osToken = osToken;
+  }
+
+  /// @inheritdoc IOsTokenFlashLoans
+  function flashLoan(
+    address recipient,
+    uint256 osTokenShares,
+    bytes memory userData
+  ) external override nonReentrant {
+    // check if not more than max flash loan amount requested
+    if (osTokenShares == 0 || osTokenShares > _maxFlashLoanAmount) {
+      revert Errors.InvalidShares();
+    }
+
+    // get current balance
+    uint256 preLoanBalance = IERC20(_osToken).balanceOf(address(this));
+
+    // mint OsToken shares for the recipient
+    IOsToken(_osToken).mint(recipient, osTokenShares);
+
+    // execute callback
+    IOsTokenFlashLoanRecipient(recipient).receiveFlashLoan(osTokenShares, userData);
+
+    // get post loan balance
+    uint256 postLoanBalance = IERC20(_osToken).balanceOf(address(this));
+
+    // check if the amount was repaid
+    if (postLoanBalance < preLoanBalance + osTokenShares) {
+      revert Errors.FlashLoanFailed();
+    }
+
+    // burn OsToken shares
+    IOsToken(address(_osToken)).burn(address(this), osTokenShares);
+
+    // emit event
+    emit OsTokenFlashLoan(recipient, osTokenShares);
+  }
+}

contracts/tokens/OsTokenVaultEscrow.sol

@@ -152,7 +152,7 @@ abstract contract OsTokenVaultEscrow is Ownable2Step, Multicall, IOsTokenVaultEs
     address vault,
     uint256 exitPositionTicket,
     uint256 osTokenShares
-  ) external override {
+  ) external override returns (uint256 claimedAssets) {
     // burn osToken shares
     _osTokenVaultController.burnShares(msg.sender, osTokenShares);
 
@@ -167,33 +167,26 @@ abstract contract OsTokenVaultEscrow is Ownable2Step, Multicall, IOsTokenVaultEs
     }
 
     // calculate assets to withdraw
-    uint256 assetsToTransfer;
     if (position.osTokenShares != osTokenShares) {
-      assetsToTransfer = Math.mulDiv(position.exitedAssets, osTokenShares, position.osTokenShares);
+      claimedAssets = Math.mulDiv(position.exitedAssets, osTokenShares, position.osTokenShares);
 
       // update position osTokenShares
-      position.exitedAssets -= SafeCast.toUint96(assetsToTransfer);
+      position.exitedAssets -= SafeCast.toUint96(claimedAssets);
       position.osTokenShares -= SafeCast.toUint128(osTokenShares);
       _positions[vault][exitPositionTicket] = position;
     } else {
-      assetsToTransfer = position.exitedAssets;
+      claimedAssets = position.exitedAssets;
 
       // remove position as it is fully processed
       delete _positions[vault][exitPositionTicket];
     }
-    if (assetsToTransfer == 0) revert Errors.ExitRequestNotProcessed();
+    if (claimedAssets == 0) revert Errors.ExitRequestNotProcessed();
 
     // transfer assets
-    _transferAssets(position.owner, assetsToTransfer);
+    _transferAssets(position.owner, claimedAssets);
 
     // emit event
-    emit ExitedAssetsClaimed(
-      msg.sender,
-      vault,
-      exitPositionTicket,
-      osTokenShares,
-      assetsToTransfer
-    );
+    emit ExitedAssetsClaimed(msg.sender, vault, exitPositionTicket, osTokenShares, claimedAssets);
   }
 
   /// @inheritdoc IOsTokenVaultEscrow

contracts/vaults/ethereum/EthGenesisVault.sol

@@ -201,7 +201,7 @@ contract EthGenesisVault is Initializable, EthVault, IEthGenesisVault {
     // calculate max osToken shares that user can mint based on its current staked balance and osToken position
     uint256 userMaxOsTokenShares = _calcMaxOsTokenShares(userAssets);
     unchecked {
-      // cannot underflow because userOsTokenShares < userMaxOsTokenShares
+      // cannot underflow because mintedShares < userMaxOsTokenShares
       return mintedShares < userMaxOsTokenShares ? userMaxOsTokenShares - mintedShares : 0;
     }
   }

contracts/vaults/ethereum/EthVault.sol

@@ -2,7 +2,6 @@
 
 pragma solidity ^0.8.22;
 
-import {Math} from '@openzeppelin/contracts/utils/math/Math.sol';
 import {Initializable} from '@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol';
 import {IEthVault} from '../../interfaces/IEthVault.sol';
 import {IEthVaultFactory} from '../../interfaces/IEthVaultFactory.sol';

contracts/vaults/gnosis/GnoGenesisVault.sol

@@ -199,7 +199,7 @@ contract GnoGenesisVault is Initializable, GnoVault, IGnoGenesisVault {
     // calculate max osToken shares that user can mint based on its current staked balance and osToken position
     uint256 userMaxOsTokenShares = _calcMaxOsTokenShares(userAssets);
     unchecked {
-      // cannot underflow because userOsTokenShares < userMaxOsTokenShares
+      // cannot underflow because mintedShares < userMaxOsTokenShares
       return mintedShares < userMaxOsTokenShares ? userMaxOsTokenShares - mintedShares : 0;
     }
   }

contracts/vaults/modules/VaultOsToken.sol

@@ -205,7 +205,7 @@ abstract contract VaultOsToken is VaultImmutables, VaultState, VaultEnterExit, I
       }
       // calculate max OsToken shares that can be minted
       unchecked {
-        // cannot underflow because userOsTokenShares < userMaxOsTokenShares
+        // cannot underflow because position.shares < userMaxOsTokenShares
         osTokenShares = userMaxOsTokenShares - position.shares;
       }
     }

contracts/vaults/modules/VaultState.sol

@@ -192,9 +192,9 @@ abstract contract VaultState is VaultImmutables, Initializable, VaultAdmin, Vaul
   }
 
   /**
-	 * @dev Internal function that must be used to process exit queue
+   * @dev Internal function that must be used to process exit queue
    * @dev Make sure that sufficient time passed between exit queue updates (at least 1 day).
-          Currently it's restricted by the keeper's harvest interval
+   *      Currently it's restricted by the keeper's harvest interval
    * @return burnedShares The total amount of burned shares
    */
   function _updateExitQueue() internal virtual returns (uint256 burnedShares) {
@@ -334,8 +334,8 @@ abstract contract VaultState is VaultImmutables, Initializable, VaultAdmin, Vaul
   ) internal virtual returns (int256, bool);
 
   /**
-	 * @dev Internal function for retrieving the total assets stored in the Vault.
-          NB! Assets can be forcibly sent to the vault, the returned value must be used with caution
+   * @dev Internal function for retrieving the total assets stored in the Vault.
+   *      NB! Assets can be forcibly sent to the vault, the returned value must be used with caution
    * @return The total amount of assets stored in the Vault
    */
   function _vaultAssets() internal view virtual returns (uint256);