# `FlashLev.close` exercise Write your code inside the [`FlashLev` contract](https://github.com/Cyfrin/defi-reth/blob/main/foundry/src/exercises/FlashLev.sol). This exercise is designed to test your understanding of how to structure a smart contract function for closing a leveraged position using a flash loan. ```solidity function close(CloseParams calldata params) external { // Write your code here } ``` ## Instructions 1. **Get debt owed to Aave** - Get the amount of debt owed to Aave > **Hint:** Look for a function inside `AaveHelper` to get the debt of this contract. 2. **Initiate a flash loan** - Encode flash loan data into `FlashLoanData`. - Call `flashLoan` to initiate a flash loan. > **Hint:** Look inside `AaveHelper` to see how to call the function `flashLoan`. # `_flashLoanCallback` ```solidity function _flashLoanCallback( address token, uint256 amount, uint256 fee, bytes memory params ) internal override { // Write your code here // Code for opening a position is omitted } ``` ## Instructions 1. **Implement logic for closing a position** - Implement flash loan callback logic for closing a position. > **Hint:** > > - Look into `AaveHelper` for how to repay stablecoin debt and withdraw collateral. > - Look into `SwapHelper` for how to swap tokens. 2. **Handle profit and loss** - If there is profit, transfer it to the caller that initiated a call to close. - Otherwise, there is a loss. Pull the loss from the caller to repay the flash loan. > **Hint:** Caller is stored in `FlashLoanData.caller` 3. **Repay flash loan** - Approve Aave to repay flash loan amount. > **Hint:** > > - Address to approve is `pool`, initialized inside `AaveHelper`. > - Amount to approve for repayment is amount borrowed + fee. ## Testing ```shell forge test --fork-url $FORK_URL --match-path test/exercise-aave-flash-lev.sol --match-test test_flashLev -vvv ```