feat: v4 direct minter

.gitmodules

@@ -2,3 +2,7 @@
 	path = lib/aave-helpers
 	url = https://github.com/aave-dao/aave-helpers
 	branch = main
+[submodule "lib/aave-v4"]
+	path = lib/aave-v4
+	url = https://github.com/aave/aave-v4
+	branch = v0.5.9

README.md

@@ -2,19 +2,21 @@
 
 ![header](./header.png)
 
-The GHO direct minter is a generic facilitator that can inject GHO into an aave pool.
+The GHO direct minter is a generic facilitator that can inject GHO into an Aave pool.
 
 ### Summary
 
 The `GhoDirectMinter` is a smart contract that can be used to mint & burn GHO directly into/from an Aave pool.
 In order to mint GHO the `GhoDirectMinter` will need to be registered as a `Facilitator` in the GHO contract.
 
-This repository contains two contracts:
+This repository contains the following contracts:
 
-- [`GhoDirectMinter`](./src/GhoDirectMinter.sol) which contains the actual Facilitator
-- [`LidoGHOListing`](./src/proposals/LidoGHOListing.sol) which is a reference implementation of a proposal to 1) list GHO on Aave Lido instance and 2) deploy and active a `GhoDirectMinter` facilitator.
+- [`GhoDirectMinter`](./src/GhoDirectMinter.sol) — Facilitator for Aave v3 pools.
+- [`GhoDirectMinterV4`](./src/GhoDirectMinterV4.sol) — Facilitator for the Aave v4 Hub.
 
-### Specification
+---
+
+### GhoDirectMinter (v3)
 
 **Prerequisites:**
 
@@ -29,13 +31,42 @@ The `GhoDirectMinter` offers the following functions:
 - `withdrawAndBurn` which allows a permissioned entity to withdraw GHO from the pool and burn it.
 - `transferExcessToTreasury` which allows the permissionless transfer of the accrued fee to the collector.
 
-While default permissioned entity is the owner(likely the governance short executor), but the contract inherits from [UpgradeableOwnableWithGuardian](https://github.com/bgd-labs/solidity-utils/blob/main/src/contracts/access-control/UpgradeableOwnableWithGuardian.sol) which allows to share permissions with another party (e.g. the GHO stewards).
+While default permissioned entity is the owner (likely the governance short executor), the contract inherits from [UpgradeableOwnableWithGuardian](https://github.com/bgd-labs/solidity-utils/blob/main/src/contracts/access-control/UpgradeableOwnableWithGuardian.sol) which allows to share permissions with another party (e.g. the GHO stewards).
 
-### Risk considerations
+**Risk considerations:**
 
 The `GhoDirectMinter` can only inject and remove available GHO from the pool.
 The actual maximum exposure of the reserve is managed via the `BucketSize` and the chosen `borrow cap`.
 
+---
+
+### GhoDirectMinterV4
+
+The `GhoDirectMinterV4` is the Aave v4 equivalent. Instead of interacting with an Aave v3 Pool, it injects GHO as liquidity into an Aave v4 Hub.
+
+**Prerequisites:**
+
+- GHO must be registered as an asset on the Hub.
+- the `GhoDirectMinterV4` must be registered as a **spoke** on the Hub for the GHO asset with `addCap` set to `MAX_ALLOWED_SPOKE_CAP` and `drawCap` set to `0`.
+- the `GhoDirectMinterV4` must be registered as a GHO `Facilitator` with a non-zero bucket capacity.
+- the Hub's `AccessManager` must grant `HUB_ADMIN_ROLE` to the entity that will call `addSpoke` (e.g. the governance executor).
+
+The `GhoDirectMinterV4` offers the following functions:
+
+- `mintAndSupply` — mints GHO directly to the Hub and calls `hub.add()` to register the added liquidity.
+- `withdrawAndBurn` — calls `hub.remove()` to withdraw GHO and then burns it.
+- `transferExcessToTreasury` — computes the excess shares (spoke balance above the facilitator bucket level) and transfers them to the Hub's fee receiver via `hub.payFeeShares()`.
+
+**Caveats:**
+
+- The Hub uses a share-based accounting model. Share-to-asset conversions may introduce small rounding differences (typically ±1 wei). The `transferExcessToTreasury` function underestimates excess shares to ensure the facilitator always remains at or above its bucket level.
+- The constructor derives `ASSET_ID` from `hub.getAssetId(gho)`, so GHO must already be registered on the Hub at deployment time.
+
+**Risk considerations:**
+
+The `GhoDirectMinterV4` can only inject and remove available GHO from the Hub.
+The actual maximum exposure is managed via the GHO `BucketSize`, the spoke's `addCap`, and Hub-level parameters.
+
 ## Development
 
 This project uses [Foundry](https://getfoundry.sh). See the [book](https://book.getfoundry.sh/getting-started/installation.html) for detailed instructions on how to install and use Foundry.

foundry.lock

@@ -4,5 +4,11 @@
       "name": "main",
       "rev": "0459d4ef721c6306a194a36a559a8462f9b19633"
     }
+  },
+  "lib/aave-v4": {
+    "tag": {
+      "name": "v0.5.9",
+      "rev": "c3b92877ec49c791e7eaaf77afe73eabd9bb7b1e"
+    }
   }
 }

foundry.toml

@@ -33,6 +33,7 @@ gnosis = "${RPC_GNOSIS}"
 zkEVM = "${RPC_ZKEVM}"
 celo = "${RPC_CELO}"
 zksync = "${RPC_ZKSYNC}"
+devnet = "https://virtual.mainnet-aave.us-east.rpc.tenderly.co/38393fd3-0a79-4e60-b8cc-c6bb5903454a"
 
 [fmt]
 tab_width = 2

remappings.txt

@@ -7,3 +7,5 @@ forge-std/=lib/aave-helpers/lib/forge-std/src/
 openzeppelin-contracts-upgradeable/=lib/aave-helpers/lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/lib/openzeppelin-contracts-upgradeable/
 openzeppelin-contracts/=lib/aave-helpers/lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/lib/openzeppelin-contracts-upgradeable/lib/openzeppelin-contracts/
 solidity-utils/=lib/aave-helpers/lib/aave-address-book/lib/aave-v3-origin/lib/solidity-utils/src/
+aave-v4/=lib/aave-v4/src/
+lib/aave-v4/:src=lib/aave-v4/src/

script/Deploy.s.sol

@@ -7,8 +7,9 @@ import {ICollector} from "aave-v3-origin/contracts/treasury/ICollector.sol";
 import {
   ITransparentProxyFactory
 } from "solidity-utils/contracts/transparent-proxy/interfaces/ITransparentProxyFactory.sol";
-import {GhoDirectMinter} from "../src/GhoDirectMinter.sol";
-import {IGhoToken} from "../src/interfaces/IGhoToken.sol";
+import {GhoDirectMinter} from "src/GhoDirectMinter.sol";
+import {GhoDirectMinterV4} from "src/GhoDirectMinterV4.sol";
+import {IGhoToken} from "src/interfaces/IGhoToken.sol";
 
 import {AaveV3Ethereum, AaveV3EthereumAssets} from "aave-address-book/AaveV3Ethereum.sol";
 import {AaveV3EthereumLido} from "aave-address-book/AaveV3EthereumLido.sol";
@@ -32,6 +33,21 @@ library DeploymentLibrary {
     );
   }
 
+  function _deployV4Facilitator(
+    ITransparentProxyFactory proxyFactory,
+    address upgradeAdmin,
+    address hub,
+    address gho,
+    address council
+  ) internal returns (address) {
+    address impl = address(new GhoDirectMinterV4(hub, gho));
+    return proxyFactory.create(
+      impl,
+      upgradeAdmin,
+      abi.encodeCall(GhoDirectMinterV4.initialize, (address(GovernanceV3Ethereum.EXECUTOR_LVL_1), council))
+    );
+  }
+
   function _deployCore() internal returns (address) {
     address council = 0x8513e6F37dBc52De87b166980Fa3F50639694B60;
 

src/GhoDirectMinterV4.sol

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity ^0.8.0;
+
+import {
+  UpgradeableOwnableWithGuardian
+} from "solidity-utils/contracts/access-control/UpgradeableOwnableWithGuardian.sol";
+import {Initializable} from "openzeppelin-contracts-upgradeable/contracts/proxy/utils/Initializable.sol";
+import {SafeERC20, IERC20} from "openzeppelin-contracts/contracts/token/ERC20/utils/SafeERC20.sol";
+import {IHub} from "aave-v4/hub/interfaces/IHub.sol";
+import {IGhoDirectMinterV4} from "src/interfaces/IGhoDirectMinterV4.sol";
+import {IGhoToken} from "src/interfaces/IGhoToken.sol";
+
+/// @title GhoDirectMinterV4
+/// @author Aave Labs
+/// @notice A GHO facilitator that injects (mints) and removes (burns) GHO from an Aave V4 Hub.
+/// @dev The GhoDirectMinterV4 is expected to be registered as a spoke on the Hub with infinite addCap.
+contract GhoDirectMinterV4 is Initializable, UpgradeableOwnableWithGuardian, IGhoDirectMinterV4 {
+  IGhoToken internal immutable GHO;
+  IHub internal immutable HUB;
+  uint256 internal immutable ASSET_ID;
+
+  /// @dev Constructor.
+  /// @param hub_ The address of the Aave v4 Hub.
+  /// @param gho_ The address of the GHO token.
+  constructor(address hub_, address gho_) {
+    _disableInitializers();
+    HUB = IHub(hub_);
+    ASSET_ID = HUB.getAssetId(gho_); // reverts on invalid `underlying`
+    GHO = IGhoToken(gho_);
+  }
+
+  /// @inheritdoc IGhoDirectMinterV4
+  function initialize(address owner, address council) external virtual initializer {
+    __Ownable_With_Guardian_init(owner, council);
+  }
+
+  /// @inheritdoc IGhoDirectMinterV4
+  function mintAndSupply(uint256 amount) external onlyOwnerOrGuardian {
+    GHO.mint(address(HUB), amount);
+    HUB.add(ASSET_ID, amount); // this spoke is given infinite cap
+  }
+
+  /// @inheritdoc IGhoDirectMinterV4
+  function withdrawAndBurn(uint256 amount) external onlyOwnerOrGuardian {
+    HUB.remove(ASSET_ID, amount, address(this));
+    GHO.burn(amount);
+  }
+
+  /// @inheritdoc IGhoDirectMinterV4
+  function transferExcessToTreasury() external {
+    (, uint256 level) = GHO.getFacilitatorBucket(address(this));
+    uint256 balance = HUB.getSpokeAddedAssets(ASSET_ID, address(this));
+    uint256 excess = balance - level;
+    // underestimate excess shares to ensure the facilitator remains at or above bucket level
+    uint256 excessShares = HUB.previewAddByAssets(ASSET_ID, excess);
+    if (excessShares > 0) {
+      HUB.payFeeShares(ASSET_ID, excessShares);
+    }
+  }
+
+  /// @inheritdoc IGhoDirectMinterV4
+  function hub() external view returns (address) {
+    return address(HUB);
+  }
+
+  /// @inheritdoc IGhoDirectMinterV4
+  function assetId() external view returns (uint256) {
+    return ASSET_ID;
+  }
+
+  /// @inheritdoc IGhoDirectMinterV4
+  function gho() external view returns (address) {
+    return address(GHO);
+  }
+}

src/interfaces/IGhoDirectMinterV4.sol

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: BUSL-1.1
+pragma solidity ^0.8.0;
+
+/// @title IGhoDirectMinterV4
+/// @author Aave Labs
+/// @notice Interface for the GhoDirectMinter, a GHO facilitator that injects (mints) and removes (burns) GHO from an Aave V4 Hub.
+/// @dev The GhoDirectMinter is expected to be registered as a spoke on the Hub with infinite addCap.
+interface IGhoDirectMinterV4 {
+  /// @notice Initializes the contract.
+  /// @param owner The address of the owner.
+  /// @param council The address of the guardian council.
+  function initialize(address owner, address council) external;
+
+  /// @notice Mints GHO and adds it as liquidity to the Hub.
+  /// @dev Only callable by the owner or guardian.
+  /// @param amount The amount of GHO to mint and supply.
+  function mintAndSupply(uint256 amount) external;
+
+  /// @notice Removes GHO liquidity from the Hub and burns it.
+  /// @dev Only callable by the owner or guardian.
+  /// @param amount The amount of GHO to withdraw and burn.
+  function withdrawAndBurn(uint256 amount) external;
+
+  /// @notice Transfers excess GHO interest (added shares above facilitator bucket level) to the fee receiver.
+  /// @dev Callable by anyone.
+  /// @dev Due to rounding in the share conversion, the amount transferred may be slightly less than the true excess.
+  function transferExcessToTreasury() external;
+
+  /// @notice Returns the address of the Aave v4 Hub.
+  /// @return The Hub contract address.
+  function hub() external view returns (address);
+
+  /// @notice Returns the asset identifier for GHO in the Hub.
+  /// @return The asset identifier.
+  function assetId() external view returns (uint256);
+
+  /// @notice Returns the address of the GHO token.
+  /// @return The GHO token address.
+  function gho() external view returns (address);
+}