Super Token Yield Backends: Aave & ERC4626 #2125
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| // SPDX-License-Identifier: MIT | ||
| pragma solidity ^0.8.23; | ||
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| /** | ||
| * A yield backend acts as interface between an ERC20 wrapper SuperToken and a yield generating protocol. | ||
| * The underlying token can be deposited on upgrade and withdrawn on downgrade. | ||
| * | ||
| * It is possible to transition from no/one yield backend to another/no yield backend. | ||
| * one -> another could be seen as a composition of one -> no -> another | ||
| * | ||
| * one -> no means withdraw not in the context of a downgrade. | ||
| * | ||
| * Contracts implementing this act as a kind of hot-pluggable library, | ||
| * using delegatecall to execute its logic on the SuperToken contract. | ||
| * This means that underlying tokens are transferred directly between the SuperToken contract and the yield protocol, | ||
| * as are yield protocol tokens representing positions in that protocol. | ||
| * If an implementation requires to hold state, it shall do so using a namespaced storage layout (EIP-7201). | ||
| */ | ||
| interface IYieldBackend { | ||
| /// Invoked by `SuperToken` as delegatecall. | ||
| /// Sets up the SuperToken as needed, e.g. by giving required approvals. | ||
| function enable() external; | ||
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| /// Invoked by `SuperToken` as delegatecall. | ||
| /// Restores the prior state, e.g. by revoking given approvals | ||
| function disable() external; | ||
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| /// Invoked by `SuperToken` as delegatecall. | ||
| /// Deposits the given amount of the underlying asset into the yield backend. | ||
| function deposit(uint256 amount) external; | ||
| /// Invoked by `SuperToken` as delegatecall. | ||
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| /// Deposits the maximum amount of the underlying asset into the yield backend. | ||
| /// Maximum is defined by the underlying asset balance of the SuperToken and the yield backend capacity. | ||
| function depositMax() external; | ||
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| /// Invoked by `SuperToken` as delegatecall. | ||
| /// Withdraws the given amount of the underlying asset from the yield backend. | ||
| function withdraw(uint256 amount) external; | ||
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| /// Invoked by `SuperToken` as delegatecall. | ||
| /// Withdraws the maximum amount of the underlying asset from the yield backend. | ||
| /// Maximum is defined by how much can be withdrawn from the yield backend at that point in time. | ||
| function withdrawMax() external; | ||
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| /// Invoked by `SuperToken` as delegatecall. | ||
| /// tranfers the deposited asset exceeding totalSupply of the SuperToken to the preset receiver account | ||
| function withdrawSurplus(uint256 totalSupply) external; | ||
| } | ||
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| // SPDX-License-Identifier: AGPLv3 | ||
| pragma solidity ^0.8.23; | ||
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| import { IYieldBackend } from "../interfaces/superfluid/IYieldBackend.sol"; | ||
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| /** | ||
| * @dev Helper to delegatecall yield backend methods. | ||
| * Reverts if the call fails. | ||
| * Does NOT return anything! | ||
| */ | ||
| library YieldBackendHelperLib { | ||
| function dCall(IYieldBackend yieldBackend, bytes memory callData) internal { | ||
| (bool success,) = address(yieldBackend).delegatecall(callData); | ||
| require(success, "yield backend delegatecall failed"); | ||
| } | ||
| } |
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| // SPDX-License-Identifier: MIT | ||
| pragma solidity ^0.8.23; | ||
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| import { IYieldBackend } from "../interfaces/superfluid/IYieldBackend.sol"; | ||
| import { IERC20, ISuperToken } from "../interfaces/superfluid/ISuperfluid.sol"; | ||
| import { IPool } from "aave-v3/interfaces/IPool.sol"; | ||
| import { IWETH } from "aave-v3/helpers/interfaces/IWETH.sol"; | ||
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| /** | ||
| * Aave supports a simple deposit/withdraw workflow nicely matching the IYieldBackend interface. | ||
| * Deposits are represented by transferrable aTokens. | ||
| * | ||
| * This contract is conceptually a hot-pluggable library. | ||
| * All methods are supposed to be invoked as delegatecall. | ||
| */ | ||
| contract AaveYieldBackend is IYieldBackend { | ||
| IERC20 public immutable ASSET_TOKEN; | ||
| IPool public immutable AAVE_POOL; | ||
| IERC20 public immutable A_TOKEN; | ||
| bool public immutable USING_WETH; | ||
| // TODO: make an immutable | ||
| address constant SURPLUS_RECEIVER = 0xac808840f02c47C05507f48165d2222FF28EF4e1; // dao.superfluid.eth | ||
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| AaveYieldBackend internal immutable _SELF; | ||
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| // THIS CONTRACT CANNOT HAVE STATE VARIABLES! | ||
| // IF STATE IS NEEDED, USE NAMESPACED STORAGE LAYOUT (EIP-7201) | ||
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| /** | ||
| * @param assetToken the asset (Aave terminology) supplied to Aave for yield. Typically, this will be | ||
| * the underlyingToken of a SuperToken. | ||
| * @param aavePool the Aave pool | ||
| */ | ||
| constructor(IERC20 assetToken, IPool aavePool) { | ||
| // TODO: any checks to be done? | ||
| if (address(assetToken) == address(0)) { | ||
| // native token, need to wrap to WETH | ||
| USING_WETH = true; | ||
| // This implementation currently only supports Base | ||
| if (block.chainid == 10 || block.chainid == 8453) { | ||
| // base, optimism | ||
| ASSET_TOKEN = IERC20(0x4200000000000000000000000000000000000006); | ||
| } else { | ||
| revert("not supported"); | ||
| } | ||
| } else { | ||
| ASSET_TOKEN = assetToken; | ||
| } | ||
| AAVE_POOL = IPool(aavePool); | ||
| A_TOKEN = IERC20(aavePool.getReserveAToken(address(ASSET_TOKEN))); | ||
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| _SELF = this; | ||
| } | ||
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| function enable() external { | ||
| // approve Aave pool to fetch asset | ||
| ASSET_TOKEN.approve(address(AAVE_POOL), type(uint256).max); | ||
| } | ||
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| function disable() external { | ||
| // Revoke approval | ||
| ASSET_TOKEN.approve(address(AAVE_POOL), 0); | ||
| } | ||
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| function deposit(uint256 amount) public { | ||
| // TODO: can this constraint break anything? | ||
| require(amount > 0, "amount must be greater than 0"); | ||
| if (USING_WETH) { | ||
| // wrap ETH to WETH | ||
| IWETH(address(ASSET_TOKEN)).deposit{value: amount}(); | ||
| } | ||
| // Deposit asset and get back aTokens | ||
| AAVE_POOL.supply(address(ASSET_TOKEN), amount, address(this), 0); | ||
| } | ||
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| function depositMax() external { | ||
| uint256 amount = USING_WETH ? | ||
| address(this).balance : | ||
| ASSET_TOKEN.balanceOf(address(this)); | ||
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| if (amount > 0) { | ||
| deposit(amount); | ||
| } | ||
| } | ||
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| function withdraw(uint256 amount) external { | ||
| // withdraw amount asset by redeeming the corresponding aTokens amount | ||
| if (USING_WETH) { | ||
| AAVE_POOL.withdraw(address(ASSET_TOKEN), amount, address(_SELF)); | ||
| _SELF.unwrapAndForwardWETH(amount); | ||
| } else { | ||
| AAVE_POOL.withdraw(address(ASSET_TOKEN), amount, address(this)); | ||
| } | ||
| } | ||
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| function withdrawMax() external { | ||
| // We can delegate the max calculation to the Aave pool by setting amount to type(uint256).max | ||
| AAVE_POOL.withdraw(address(ASSET_TOKEN), type(uint256).max, address(this)); | ||
| } | ||
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| function withdrawSurplus(uint256 totalSupply) external { | ||
| // totalSupply is always 18 decimals while assetToken and aToken may not | ||
| (uint256 normalizedTotalSupply,) = ISuperToken(address(this)).toUnderlyingAmount(totalSupply); | ||
| // decrement by 1 in order to offset Aave's rounding up | ||
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| uint256 surplusAmount = A_TOKEN.balanceOf(address(this)) - normalizedTotalSupply - 1; | ||
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| AAVE_POOL.withdraw(address(ASSET_TOKEN), surplusAmount, SURPLUS_RECEIVER); | ||
| } | ||
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| // ============ functions operating on this contract itself (NOT in delegatecall context) ============ | ||
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| // allow unwrapping from WETH to this contract | ||
| receive() external payable {} | ||
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| // To be invoked by `withdraw` executed via delegatecall in a SuperToken context. | ||
| // Since WETH never stays in this contract, no validation of msg.sender is necessary. | ||
| function unwrapAndForwardWETH(uint256 amount) external { | ||
| IWETH(address(ASSET_TOKEN)).withdraw(amount); | ||
| (bool success, ) = address(msg.sender).call{value: amount}(""); | ||
| require(success, "call failed"); | ||
| } | ||
| } | ||
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