feat(flash-swap): repay USDC liquidation 0.3% Uniswap fee from bot wa…

…llet balance
hifi-finance · Nov 3, 2021 · 6625f4a · 6625f4a
1 parent 4e3f8cb
commit 6625f4a
Show file tree

Hide file tree

Showing 6 changed files with 38 additions and 17 deletions.
diff --git a/packages/flash-swap/contracts/uniswap-v2/HifiFlashUniswapV2Underlying.sol b/packages/flash-swap/contracts/uniswap-v2/HifiFlashUniswapV2Underlying.sol
@@ -34,6 +34,9 @@ contract HifiFlashUniswapV2Underlying is IHifiFlashUniswapV2Underlying {
     /// @inheritdoc IHifiFlashUniswapV2Underlying
     IBalanceSheetV1 public override balanceSheet;
 
+    /// @inheritdoc IHifiFlashUniswapV2Underlying
+    address public override bot;
+
     /// @inheritdoc IHifiFlashUniswapV2Underlying
     address public override uniV2Factory;
 
@@ -43,10 +46,12 @@ contract HifiFlashUniswapV2Underlying is IHifiFlashUniswapV2Underlying {
     /// CONSTRUCTOR ///
     constructor(
         IBalanceSheetV1 balanceSheet_,
+        address bot_,
         address uniV2Factory_,
         bytes32 uniV2PairInitCodeHash_
     ) {
         balanceSheet = IBalanceSheetV1(balanceSheet_);
+        bot = bot_;
         uniV2Factory = uniV2Factory_;
         uniV2PairInitCodeHash = uniV2PairInitCodeHash_;
     }
@@ -102,6 +107,7 @@ contract HifiFlashUniswapV2Underlying is IHifiFlashUniswapV2Underlying {
         address borrower;
         IErc20 collateral;
         uint256 mintedHTokenAmount;
+        uint256 overshootCollateralAmount;
         uint256 repayCollateralAmount;
         uint256 seizedCollateralAmount;
         address swapToken;
@@ -151,6 +157,14 @@ contract HifiFlashUniswapV2Underlying is IHifiFlashUniswapV2Underlying {
         // Calculate the amount of collateral required to repay.
         vars.repayCollateralAmount = getRepayCollateralAmount(vars.underlyingAmount);
 
+        // The bot wallet compensates for any overshoot of collateral repay amount above seized amount.
+        if (vars.repayCollateralAmount > vars.seizedCollateralAmount) {
+            unchecked {
+                vars.overshootCollateralAmount = vars.repayCollateralAmount - vars.seizedCollateralAmount;
+            }
+            vars.collateral.safeTransferFrom(bot, address(this), vars.overshootCollateralAmount);
+        }
+
         // Pay back the loan.
         vars.collateral.safeTransfer(msg.sender, vars.repayCollateralAmount);
 

diff --git a/packages/flash-swap/contracts/uniswap-v2/IHifiFlashUniswapV2Underlying.sol b/packages/flash-swap/contracts/uniswap-v2/IHifiFlashUniswapV2Underlying.sol
@@ -27,6 +27,9 @@ interface IHifiFlashUniswapV2Underlying is IUniswapV2Callee {
     /// @notice The unique BalanceSheet contract associated with this contract.
     function balanceSheet() external view returns (IBalanceSheetV1);
 
+    /// @notice The unique bot wallet address associated with this contract.
+    function bot() external view returns (address);
+
     /// @notice Compares the token addresses to find the collateral address and the underlying amount.
     /// @dev See this StackExchange post: https://ethereum.stackexchange.com/q/102670/24693.
     ///

diff --git a/packages/flash-swap/test/integration/hifiFlashUniswapV2Underlying/effects/uniswapV2Call.ts b/packages/flash-swap/test/integration/hifiFlashUniswapV2Underlying/effects/uniswapV2Call.ts
@@ -226,11 +226,11 @@ export function shouldBehaveLikeUniswapV2Call(): void {
               .connect(this.signers.borrower)
               .approve(this.contracts.balanceSheet.address, wbtcDepositAmount);
 
-            // Minst USDC and send it to flash-swap to be used for Uniswap V2 fee repay
-            await this.contracts.usdc.__godMode_mint(
-              this.contracts.hifiFlashUniswapV2Underlying.address,
-              usdcRepayFeeAmount,
-            );
+            // Minst USDC to the bot wallet and approve the flash swap contract to spend it
+            await this.contracts.usdc.__godMode_mint(this.signers.bot.address, usdcRepayFeeAmount);
+            await this.contracts.usdc
+              .connect(this.signers.bot)
+              .approve(this.contracts.hifiFlashUniswapV2Underlying.address, usdcRepayFeeAmount);
 
             // Deposit the USDC in the BalanceSheet.
             await this.contracts.balanceSheet
@@ -271,14 +271,14 @@ export function shouldBehaveLikeUniswapV2Call(): void {
             it("flash swaps USDC making no USDC profit and spending allocated USDC to pay swap fee", async function () {
               const to: string = this.contracts.hifiFlashUniswapV2Underlying.address;
               const preUsdcBalanceAccount = await this.contracts.usdc.balanceOf(this.signers.liquidator.address);
-              const preUsdcBalanceContract = await this.contracts.usdc.balanceOf(to);
+              const preUsdcBalanceBot = await this.contracts.usdc.balanceOf(this.signers.bot.address);
               await this.contracts.uniswapV2Pair
                 .connect(this.signers.liquidator)
                 .swap(token0Amount, token1Amount, to, data);
               const newUsdcBalanceAccount = await this.contracts.usdc.balanceOf(this.signers.liquidator.address);
-              const newUsdcBalanceContract = await this.contracts.usdc.balanceOf(to);
+              const newUsdcBalanceBot = await this.contracts.usdc.balanceOf(this.signers.bot.address);
               expect(newUsdcBalanceAccount).to.equal(preUsdcBalanceAccount);
-              expect(preUsdcBalanceContract.sub(newUsdcBalanceContract)).to.equal(usdcRepayFeeAmount);
+              expect(preUsdcBalanceBot.sub(newUsdcBalanceBot)).to.equal(usdcRepayFeeAmount);
             });
           });
 
@@ -306,14 +306,14 @@ export function shouldBehaveLikeUniswapV2Call(): void {
                 it("flash swaps USDC making no USDC profit and spending allocated USDC to pay swap fee", async function () {
                   const to: string = this.contracts.hifiFlashUniswapV2Underlying.address;
                   const preUsdcBalanceAccount = await this.contracts.usdc.balanceOf(this.signers.liquidator.address);
-                  const preUsdcBalanceContract = await this.contracts.usdc.balanceOf(to);
+                  const preUsdcBalanceBot = await this.contracts.usdc.balanceOf(this.signers.bot.address);
                   await this.contracts.uniswapV2Pair
                     .connect(this.signers.liquidator)
                     .swap(token0Amount, token1Amount, to, data);
                   const newUsdcBalanceAccount = await this.contracts.usdc.balanceOf(this.signers.liquidator.address);
-                  const newUsdcBalanceContract = await this.contracts.usdc.balanceOf(to);
+                  const newUsdcBalanceBot = await this.contracts.usdc.balanceOf(this.signers.bot.address);
                   expect(newUsdcBalanceAccount).to.equal(preUsdcBalanceAccount);
-                  expect(preUsdcBalanceContract.sub(newUsdcBalanceContract)).to.equal(usdcRepayFeeAmount);
+                  expect(preUsdcBalanceBot.sub(newUsdcBalanceBot)).to.equal(usdcRepayFeeAmount);
                 });
               });
 
@@ -360,29 +360,29 @@ export function shouldBehaveLikeUniswapV2Call(): void {
                   it("flash swaps USDC making no USDC profit and spending allocated USDC to pay swap fee", async function () {
                     const to: string = this.contracts.hifiFlashUniswapV2Underlying.address;
                     const preUsdcBalanceAccount = await this.contracts.usdc.balanceOf(this.signers.liquidator.address);
-                    const preUsdcBalanceContract = await this.contracts.usdc.balanceOf(to);
+                    const preUsdcBalanceBot = await this.contracts.usdc.balanceOf(this.signers.bot.address);
                     await this.contracts.uniswapV2Pair
                       .connect(this.signers.liquidator)
                       .swap(localToken0Amount, localToken1Amount, to, data);
                     const newUsdcBalanceAccount = await this.contracts.usdc.balanceOf(this.signers.liquidator.address);
-                    const newUsdcBalanceContract = await this.contracts.usdc.balanceOf(to);
+                    const newUsdcBalanceBot = await this.contracts.usdc.balanceOf(this.signers.bot.address);
                     expect(newUsdcBalanceAccount).to.equal(preUsdcBalanceAccount);
-                    expect(preUsdcBalanceContract.sub(newUsdcBalanceContract)).to.equal(usdcRepayFeeAmount);
+                    expect(preUsdcBalanceBot.sub(newUsdcBalanceBot)).to.equal(usdcRepayFeeAmount);
                   });
                 });
 
                 context("initial order of tokens in the pair", function () {
                   it("flash swaps USDC making no USDC profit and spending allocated USDC to pay swap fee", async function () {
                     const to: string = this.contracts.hifiFlashUniswapV2Underlying.address;
                     const preUsdcBalanceAccount = await this.contracts.usdc.balanceOf(this.signers.liquidator.address);
-                    const preUsdcBalanceContract = await this.contracts.usdc.balanceOf(to);
+                    const preUsdcBalanceBot = await this.contracts.usdc.balanceOf(this.signers.bot.address);
                     await this.contracts.uniswapV2Pair
                       .connect(this.signers.liquidator)
                       .swap(token0Amount, token1Amount, to, data);
                     const newUsdcBalanceAccount = await this.contracts.usdc.balanceOf(this.signers.liquidator.address);
-                    const newUsdcBalanceContract = await this.contracts.usdc.balanceOf(to);
+                    const newUsdcBalanceBot = await this.contracts.usdc.balanceOf(this.signers.bot.address);
                     expect(newUsdcBalanceAccount).to.equal(preUsdcBalanceAccount);
-                    expect(preUsdcBalanceContract.sub(newUsdcBalanceContract)).to.equal(usdcRepayFeeAmount);
+                    expect(preUsdcBalanceBot.sub(newUsdcBalanceBot)).to.equal(usdcRepayFeeAmount);
                   });
 
                   it("emits a FlashLiquidateBorrow event", async function () {

diff --git a/packages/flash-swap/test/shared/contexts.ts b/packages/flash-swap/test/shared/contexts.ts
@@ -18,6 +18,7 @@ export function baseContext(description: string, hooks: () => void): void {
       this.signers.borrower = signers[1];
       this.signers.liquidator = signers[2];
       this.signers.raider = signers[3];
+      this.signers.bot = signers[4];
 
       // Get rid of this when https://github.com/nomiclabs/hardhat/issues/849 gets fixed.
       this.loadFixture = createFixtureLoader(signers as Signer[] as Wallet[]);

diff --git a/packages/flash-swap/test/shared/fixtures.ts b/packages/flash-swap/test/shared/fixtures.ts
@@ -102,10 +102,12 @@ export async function integrationFixture(signers: Signer[]): Promise<Integration
     ])
   );
 
+  const bot: Signer = signers[4];
   const hifiFlashUniswapV2UnderlyingArtifact: Artifact = await artifacts.readArtifact("HifiFlashUniswapV2Underlying");
   const hifiFlashUniswapV2Underlying: HifiFlashUniswapV2Underlying = <HifiFlashUniswapV2Underlying>(
     await waffle.deployContract(deployer, hifiFlashUniswapV2UnderlyingArtifact, [
       balanceSheet.address,
+      await bot.getAddress(),
       uniswapV2Factory.address,
       uniV2PairInitCodeHash,
     ])

diff --git a/packages/flash-swap/test/shared/types.ts b/packages/flash-swap/test/shared/types.ts
@@ -38,4 +38,5 @@ export interface Signers {
   borrower: SignerWithAddress;
   liquidator: SignerWithAddress;
   raider: SignerWithAddress;
+  bot: SignerWithAddress;
 }