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Merge pull request #98 from hifi-finance/feat/flash-swap-uni-v3
Implement Flash Swap for Uniswap V3
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packages/flash-swap/contracts/uniswap-v3/FlashUniswapV3.sol
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| // SPDX-License-Identifier: LGPL-3.0-or-later | ||
| pragma solidity ^0.8.4; | ||
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| import "@prb/contracts/token/erc20/IErc20.sol"; | ||
| import "@prb/contracts/token/erc20/SafeErc20.sol"; | ||
| import "@hifi/protocol/contracts/core/balance-sheet/IBalanceSheetV2.sol"; | ||
| import "@uniswap/v3-core/contracts/interfaces/IUniswapV3Pool.sol"; | ||
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| import "./IFlashUniswapV3.sol"; | ||
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| /// @title FlashUniswapV3 | ||
| /// @author Hifi | ||
| contract FlashUniswapV3 is IFlashUniswapV3 { | ||
| using SafeErc20 for IErc20; | ||
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| /// PUBLIC STORAGE /// | ||
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| /// @inheritdoc IFlashUniswapV3 | ||
| IBalanceSheetV2 public immutable override balanceSheet; | ||
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| /// @inheritdoc IFlashUniswapV3 | ||
| address public immutable override uniV3Factory; | ||
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| /// @dev TickMath constants for computing the sqrt price limit. | ||
| uint160 internal constant MIN_SQRT_RATIO = 4295128739; | ||
| uint160 internal constant MAX_SQRT_RATIO = 1461446703485210103287273052203988822378723970342; | ||
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| /// @dev The Uniswap V3 pool init code hash. | ||
| bytes32 internal constant POOL_INIT_CODE_HASH = 0xe34f199b19b2b4f47f68442619d555527d244f78a3297ea89325f843f87b8b54; | ||
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| /// CONSTRUCTOR /// | ||
| constructor(IBalanceSheetV2 balanceSheet_, address uniV3Factory_) { | ||
| balanceSheet = balanceSheet_; | ||
| uniV3Factory = uniV3Factory_; | ||
| } | ||
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| struct FlashLiquidateLocalVars { | ||
| PoolKey poolKey; | ||
| IErc20 underlying; | ||
| bool zeroForOne; | ||
| } | ||
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| struct UniswapV3SwapCallbackParams { | ||
| IHToken bond; | ||
| address borrower; | ||
| IErc20 collateral; | ||
| PoolKey poolKey; | ||
| address sender; | ||
| int256 turnout; | ||
| uint256 underlyingAmount; | ||
| } | ||
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| /// PUBLIC NON-CONSTANT FUNCTIONS /// | ||
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| /// @inheritdoc IFlashUniswapV3 | ||
| function flashLiquidate(FlashLiquidateParams memory params) external override { | ||
| FlashLiquidateLocalVars memory vars; | ||
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| // This flash swap contract does not support liquidating vaults backed by underlying. | ||
| vars.underlying = params.bond.underlying(); | ||
| if (params.collateral == vars.underlying) { | ||
| revert FlashUniswapV3__LiquidateUnderlyingBackedVault({ | ||
| borrower: params.borrower, | ||
| underlying: address(vars.underlying) | ||
| }); | ||
| } | ||
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| // Compute the flash pool key and address. | ||
| vars.poolKey = getPoolKey({ | ||
| tokenA: address(params.collateral), | ||
| tokenB: address(vars.underlying), | ||
| fee: params.poolFee | ||
| }); | ||
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| // The direction of the swap, true for token0 to token1, false for token1 to token0. | ||
| vars.zeroForOne = address(vars.underlying) == vars.poolKey.token1; | ||
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| IUniswapV3Pool(poolFor(vars.poolKey)).swap({ | ||
| recipient: address(this), | ||
| zeroForOne: vars.zeroForOne, | ||
| amountSpecified: int256(params.underlyingAmount) * -1, | ||
| sqrtPriceLimitX96: vars.zeroForOne ? MIN_SQRT_RATIO + 1 : MAX_SQRT_RATIO - 1, | ||
| data: abi.encode( | ||
| UniswapV3SwapCallbackParams({ | ||
| bond: params.bond, | ||
| borrower: params.borrower, | ||
| collateral: params.collateral, | ||
| poolKey: vars.poolKey, | ||
| sender: msg.sender, | ||
| turnout: params.turnout, | ||
| underlyingAmount: params.underlyingAmount | ||
| }) | ||
| ) | ||
| }); | ||
| } | ||
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| struct UniswapV3SwapCallbackLocalVars { | ||
| uint256 mintedHTokenAmount; | ||
| uint256 profitAmount; | ||
| uint256 repayAmount; | ||
| uint256 seizeAmount; | ||
| uint256 subsidyAmount; | ||
| } | ||
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| /// @inheritdoc IUniswapV3SwapCallback | ||
| function uniswapV3SwapCallback( | ||
| int256 amount0Delta, | ||
| int256 amount1Delta, | ||
| bytes calldata data | ||
| ) external override { | ||
| UniswapV3SwapCallbackLocalVars memory vars; | ||
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| // Unpack the ABI encoded data passed by the UniswapV3Pool contract. | ||
| UniswapV3SwapCallbackParams memory params = abi.decode(data, (UniswapV3SwapCallbackParams)); | ||
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| // Check that the caller is the Uniswap V3 flash pool contract. | ||
| if (msg.sender != poolFor(params.poolKey)) { | ||
| revert FlashUniswapV3__CallNotAuthorized(msg.sender); | ||
| } | ||
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| // Mint hTokens and liquidate the borrower. | ||
| vars.mintedHTokenAmount = mintHTokens({ bond: params.bond, underlyingAmount: params.underlyingAmount }); | ||
| vars.seizeAmount = liquidateBorrow({ | ||
| borrower: params.borrower, | ||
| bond: params.bond, | ||
| collateral: params.collateral, | ||
| mintedHTokenAmount: vars.mintedHTokenAmount | ||
| }); | ||
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| // Calculate the amount of collateral required to repay. | ||
| vars.repayAmount = uint256(amount0Delta > 0 ? amount0Delta : amount1Delta); | ||
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| // Note that "turnout" is a signed int. When it is negative, it acts as a maximum subsidy amount. | ||
| // When its value is positive, it acts as a minimum profit. | ||
| if (int256(vars.seizeAmount) < int256(vars.repayAmount) + params.turnout) { | ||
| revert FlashUniswapV3__TurnoutNotSatisfied({ | ||
| seizeAmount: vars.seizeAmount, | ||
| repayAmount: vars.repayAmount, | ||
| turnout: params.turnout | ||
| }); | ||
| } | ||
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| // Transfer the subsidy amount. | ||
| if (vars.repayAmount > vars.seizeAmount) { | ||
| unchecked { | ||
| vars.subsidyAmount = vars.repayAmount - vars.seizeAmount; | ||
| } | ||
| params.collateral.safeTransferFrom(params.sender, address(this), vars.subsidyAmount); | ||
| } | ||
| // Or reap the profit. | ||
| else if (vars.seizeAmount > vars.repayAmount) { | ||
| unchecked { | ||
| vars.profitAmount = vars.seizeAmount - vars.repayAmount; | ||
| } | ||
| params.collateral.safeTransfer(params.sender, vars.profitAmount); | ||
| } | ||
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| // Pay back the loan. | ||
| params.collateral.safeTransfer(msg.sender, vars.repayAmount); | ||
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| // Emit an event. | ||
| emit FlashSwapAndLiquidateBorrow({ | ||
| liquidator: params.sender, | ||
| borrower: params.borrower, | ||
| bond: address(params.bond), | ||
| collateral: address(params.collateral), | ||
| underlyingAmount: params.underlyingAmount, | ||
| seizeAmount: vars.seizeAmount, | ||
| repayAmount: vars.repayAmount, | ||
| subsidyAmount: vars.subsidyAmount, | ||
| profitAmount: vars.profitAmount | ||
| }); | ||
| } | ||
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| /// INTERNAL CONSTANT FUNCTIONS /// | ||
|
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| /// @dev Returns the Uniswap V3 pool key for a given token pair and fee level. | ||
| function getPoolKey( | ||
| address tokenA, | ||
| address tokenB, | ||
| uint24 fee | ||
| ) internal pure returns (PoolKey memory) { | ||
| if (tokenA > tokenB) (tokenA, tokenB) = (tokenB, tokenA); | ||
| return PoolKey({ token0: tokenA, token1: tokenB, fee: fee }); | ||
| } | ||
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| /// @dev Calculates the CREATE2 address for a Uniswap V3 pool without making any external calls. | ||
| function poolFor(PoolKey memory key) internal view returns (address pool) { | ||
| // solhint-disable-next-line reason-string | ||
| require(key.token0 < key.token1); | ||
| pool = address( | ||
| uint160( | ||
| uint256( | ||
| keccak256( | ||
| abi.encodePacked( | ||
| hex"ff", | ||
| uniV3Factory, | ||
| keccak256(abi.encode(key.token0, key.token1, key.fee)), | ||
| POOL_INIT_CODE_HASH | ||
| ) | ||
| ) | ||
| ) | ||
| ) | ||
| ); | ||
| } | ||
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| /// INTERNAL NON-CONSTANT FUNCTIONS /// | ||
|
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| /// @dev Liquidates the borrower, receiving collateral at a discount. | ||
| function liquidateBorrow( | ||
| address borrower, | ||
| IHToken bond, | ||
| IErc20 collateral, | ||
| uint256 mintedHTokenAmount | ||
| ) internal returns (uint256 seizeCollateralAmount) { | ||
| uint256 collateralAmount = balanceSheet.getCollateralAmount(borrower, collateral); | ||
| uint256 hypotheticalRepayAmount = balanceSheet.getRepayAmount(collateral, collateralAmount, bond); | ||
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| // If the hypothetical repay amount is bigger than the debt amount, this could be a single-collateral multi-bond | ||
| // vault. Otherwise, it could be a multi-collateral single-bond vault. However, it is difficult to generalize | ||
| // for the multi-collateral and multi-bond situation. The repay amount could be greater, smaller, or equal | ||
| // to the debt amount depending on the collateral and debt amount distribution. | ||
| uint256 debtAmount = balanceSheet.getDebtAmount(borrower, bond); | ||
| uint256 repayAmount = hypotheticalRepayAmount > debtAmount ? debtAmount : hypotheticalRepayAmount; | ||
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| // Truncate the repay amount such that we keep the dust in this contract rather than the BalanceSheet. | ||
| uint256 truncatedRepayAmount = mintedHTokenAmount > repayAmount ? repayAmount : mintedHTokenAmount; | ||
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| // Liquidate borrow. | ||
| uint256 oldCollateralBalance = collateral.balanceOf(address(this)); | ||
| balanceSheet.liquidateBorrow(borrower, bond, truncatedRepayAmount, collateral); | ||
| uint256 newCollateralBalance = collateral.balanceOf(address(this)); | ||
| unchecked { | ||
| seizeCollateralAmount = newCollateralBalance - oldCollateralBalance; | ||
| } | ||
| } | ||
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| /// @dev Deposits the underlying in the HToken contract to mint hTokens on a one-to-one basis. | ||
| function mintHTokens(IHToken bond, uint256 underlyingAmount) internal returns (uint256 mintedHTokenAmount) { | ||
| IErc20 underlying = bond.underlying(); | ||
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| // Allow the HToken contract to spend underlying if allowance not enough. | ||
| uint256 allowance = underlying.allowance(address(this), address(bond)); | ||
| if (allowance < underlyingAmount) { | ||
| underlying.approve(address(bond), type(uint256).max); | ||
| } | ||
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| // Deposit underlying to mint hTokens. | ||
| uint256 oldHTokenBalance = bond.balanceOf(address(this)); | ||
| bond.depositUnderlying(underlyingAmount); | ||
| uint256 newHTokenBalance = bond.balanceOf(address(this)); | ||
| unchecked { | ||
| mintedHTokenAmount = newHTokenBalance - oldHTokenBalance; | ||
| } | ||
| } | ||
| } |
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