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| Original file line number | Diff line number | Diff line change |
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| // SPDX-License-Identifier: agpl-3.0 | ||
| pragma solidity 0.6.12; | ||
| pragma experimental ABIEncoderV2; | ||
|
|
||
| import {BaseUniswapAdapter} from './BaseUniswapAdapter.sol'; | ||
| import {ILendingPoolAddressesProvider} from '../interfaces/ILendingPoolAddressesProvider.sol'; | ||
| import {IUniswapV2Router02} from '../interfaces/IUniswapV2Router02.sol'; | ||
| import {IERC20} from '../dependencies/openzeppelin/contracts/IERC20.sol'; | ||
| import {DataTypes} from '../protocol/libraries/types/DataTypes.sol'; | ||
| import {Helpers} from '../protocol/libraries/helpers/Helpers.sol'; | ||
| import {IPriceOracleGetter} from '../interfaces/IPriceOracleGetter.sol'; | ||
| import {IAToken} from '../interfaces/IAToken.sol'; | ||
| import {ReserveConfiguration} from '../protocol/libraries/configuration/ReserveConfiguration.sol'; | ||
|
|
||
| /** | ||
| * @title UniswapLiquiditySwapAdapter | ||
| * @notice Uniswap V2 Adapter to swap liquidity. | ||
| * @author Aave | ||
| **/ | ||
| contract FlashLiquidationAdapter is BaseUniswapAdapter { | ||
| using ReserveConfiguration for DataTypes.ReserveConfigurationMap; | ||
| uint256 internal constant LIQUIDATION_CLOSE_FACTOR_PERCENT = 5000; | ||
|
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||
| struct LiquidationParams { | ||
| address collateralAsset; | ||
| address borrowedAsset; | ||
| address user; | ||
| uint256 debtToCover; | ||
| bool useEthPath; | ||
| } | ||
|
|
||
| struct LiquidationCallLocalVars { | ||
| uint256 initFlashBorrowedBalance; | ||
| uint256 diffFlashBorrowedBalance; | ||
| uint256 initCollateralBalance; | ||
| uint256 diffCollateralBalance; | ||
| uint256 flashLoanDebt; | ||
| uint256 soldAmount; | ||
| uint256 remainingTokens; | ||
| uint256 borrowedAssetLeftovers; | ||
| } | ||
|
|
||
| constructor( | ||
| ILendingPoolAddressesProvider addressesProvider, | ||
| IUniswapV2Router02 uniswapRouter, | ||
| address wethAddress | ||
| ) public BaseUniswapAdapter(addressesProvider, uniswapRouter, wethAddress) {} | ||
|
|
||
| /** | ||
| * @dev Liquidate a non-healthy position collateral-wise, with a Health Factor below 1, using Flash Loan and Uniswap to repay flash loan premium. | ||
| * - The caller (liquidator) with a flash loan covers `debtToCover` amount of debt of the user getting liquidated, and receives | ||
| * a proportionally amount of the `collateralAsset` plus a bonus to cover market risk minus the flash loan premium. | ||
| * @param assets Address of asset to be swapped | ||
| * @param amounts Amount of the asset to be swapped | ||
| * @param premiums Fee of the flash loan | ||
| * @param initiator Address of the caller | ||
| * @param params Additional variadic field to include extra params. Expected parameters: | ||
| * address collateralAsset The collateral asset to release and will be exchanged to pay the flash loan premium | ||
| * address borrowedAsset The asset that must be covered | ||
| * address user The user address with a Health Factor below 1 | ||
| * uint256 debtToCover The amount of debt to cover | ||
| * bool useEthPath Use WETH as connector path between the collateralAsset and borrowedAsset at Uniswap | ||
| */ | ||
| function executeOperation( | ||
| address[] calldata assets, | ||
| uint256[] calldata amounts, | ||
| uint256[] calldata premiums, | ||
| address initiator, | ||
| bytes calldata params | ||
| ) external override returns (bool) { | ||
| require(msg.sender == address(LENDING_POOL), 'CALLER_MUST_BE_LENDING_POOL'); | ||
|
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| LiquidationParams memory decodedParams = _decodeParams(params); | ||
|
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| require(assets.length == 1 && assets[0] == decodedParams.borrowedAsset, 'INCONSISTENT_PARAMS'); | ||
|
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| _liquidateAndSwap( | ||
| decodedParams.collateralAsset, | ||
| decodedParams.borrowedAsset, | ||
| decodedParams.user, | ||
| decodedParams.debtToCover, | ||
| decodedParams.useEthPath, | ||
| amounts[0], | ||
| premiums[0], | ||
| initiator | ||
| ); | ||
|
|
||
| return true; | ||
| } | ||
|
|
||
| /** | ||
| * @dev | ||
| * @param collateralAsset The collateral asset to release and will be exchanged to pay the flash loan premium | ||
| * @param borrowedAsset The asset that must be covered | ||
| * @param user The user address with a Health Factor below 1 | ||
| * @param debtToCover The amount of debt to coverage, can be max(-1) to liquidate all possible debt | ||
| * @param useEthPath true if the swap needs to occur using ETH in the routing, false otherwise | ||
| * @param flashBorrowedAmount Amount of asset requested at the flash loan to liquidate the user position | ||
| * @param premium Fee of the requested flash loan | ||
| * @param initiator Address of the caller | ||
| */ | ||
| function _liquidateAndSwap( | ||
| address collateralAsset, | ||
| address borrowedAsset, | ||
| address user, | ||
| uint256 debtToCover, | ||
| bool useEthPath, | ||
| uint256 flashBorrowedAmount, | ||
| uint256 premium, | ||
| address initiator | ||
| ) internal { | ||
| LiquidationCallLocalVars memory vars; | ||
| vars.initCollateralBalance = IERC20(collateralAsset).balanceOf(address(this)); | ||
| if (collateralAsset != borrowedAsset) { | ||
| vars.initFlashBorrowedBalance = IERC20(borrowedAsset).balanceOf(address(this)); | ||
|
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| // Track leftover balance to rescue funds in case of external transfers into this contract | ||
| vars.borrowedAssetLeftovers = vars.initFlashBorrowedBalance.sub(flashBorrowedAmount); | ||
| } | ||
| vars.flashLoanDebt = flashBorrowedAmount.add(premium); | ||
|
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| // Approve LendingPool to use debt token for liquidation | ||
| IERC20(borrowedAsset).approve(address(LENDING_POOL), debtToCover); | ||
|
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| // Liquidate the user position and release the underlying collateral | ||
| LENDING_POOL.liquidationCall(collateralAsset, borrowedAsset, user, debtToCover, false); | ||
|
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| // Discover the liquidated tokens | ||
| uint256 collateralBalanceAfter = IERC20(collateralAsset).balanceOf(address(this)); | ||
|
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| // Track only collateral released, not current asset balance of the contract | ||
| vars.diffCollateralBalance = collateralBalanceAfter.sub(vars.initCollateralBalance); | ||
|
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| if (collateralAsset != borrowedAsset) { | ||
| // Discover flash loan balance after the liquidation | ||
| uint256 flashBorrowedAssetAfter = IERC20(borrowedAsset).balanceOf(address(this)); | ||
|
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| // Use only flash loan borrowed assets, not current asset balance of the contract | ||
| vars.diffFlashBorrowedBalance = flashBorrowedAssetAfter.sub(vars.borrowedAssetLeftovers); | ||
|
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| // Swap released collateral into the debt asset, to repay the flash loan | ||
| vars.soldAmount = _swapTokensForExactTokens( | ||
| collateralAsset, | ||
| borrowedAsset, | ||
| vars.diffCollateralBalance, | ||
| vars.flashLoanDebt.sub(vars.diffFlashBorrowedBalance), | ||
| useEthPath | ||
| ); | ||
| vars.remainingTokens = vars.diffCollateralBalance.sub(vars.soldAmount); | ||
| } else { | ||
| vars.remainingTokens = vars.diffCollateralBalance.sub(premium); | ||
| } | ||
|
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| // Allow repay of flash loan | ||
| IERC20(borrowedAsset).approve(address(LENDING_POOL), vars.flashLoanDebt); | ||
|
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| // Transfer remaining tokens to initiator | ||
| if (vars.remainingTokens > 0) { | ||
| IERC20(collateralAsset).transfer(initiator, vars.remainingTokens); | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * @dev Decodes the information encoded in the flash loan params | ||
| * @param params Additional variadic field to include extra params. Expected parameters: | ||
| * address collateralAsset The collateral asset to claim | ||
| * address borrowedAsset The asset that must be covered and will be exchanged to pay the flash loan premium | ||
| * address user The user address with a Health Factor below 1 | ||
| * uint256 debtToCover The amount of debt to cover | ||
| * bool useEthPath Use WETH as connector path between the collateralAsset and borrowedAsset at Uniswap | ||
| * @return LiquidationParams struct containing decoded params | ||
| */ | ||
| function _decodeParams(bytes memory params) internal pure returns (LiquidationParams memory) { | ||
| ( | ||
| address collateralAsset, | ||
| address borrowedAsset, | ||
| address user, | ||
| uint256 debtToCover, | ||
| bool useEthPath | ||
| ) = abi.decode(params, (address, address, address, uint256, bool)); | ||
|
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| return LiquidationParams(collateralAsset, borrowedAsset, user, debtToCover, useEthPath); | ||
| } | ||
| } |
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