flash-loan-usage

Flash Loan Patterns

Flash Loan Providers

Aave V3 Flash Loan Receiver

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {FlashLoanSimpleReceiverBase} from
    "@aave/v3-core/contracts/flashloan/base/FlashLoanSimpleReceiverBase.sol";
import {IPoolAddressesProvider} from
    "@aave/v3-core/contracts/interfaces/IPoolAddressesProvider.sol";
import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract AaveFlashLoan is FlashLoanSimpleReceiverBase {
    address public immutable owner;

    constructor(IPoolAddressesProvider provider)
        FlashLoanSimpleReceiverBase(provider)
    {
        owner = msg.sender;
    }

    function executeOperation(
        address asset,
        uint256 amount,
        uint256 premium,
        address initiator,
        bytes calldata params
    ) external override returns (bool) {
        require(msg.sender == address(POOL), "caller must be pool");
        require(initiator == address(this), "untrusted initiator");

        (uint8 action) = abi.decode(params, (uint8));

        if (action == 1) _arbitrage(asset, amount);
        else if (action == 2) _liquidate(asset, amount, params);
        else if (action == 3) _collateralSwap(asset, amount, params);

        uint256 repayment = amount + premium;
        IERC20(asset).approve(address(POOL), repayment);
        return true;
    }

    function execute(address asset, uint256 amount, bytes calldata params) external {
        require(msg.sender == owner, "only owner");
        POOL.flashLoanSimple(address(this), asset, amount, params, 0);
    }

    function _arbitrage(address asset, uint256 amount) internal {
        // Buy low on DEX A, sell high on DEX B
        // Profit must exceed the 0.05% premium
    }

    function _liquidate(address asset, uint256 amount, bytes calldata params) internal {
        // Use borrowed funds to liquidate an underwater position
        // Receive collateral at a discount, swap back to repay
    }

    function _collateralSwap(address asset, uint256 amount, bytes calldata params) internal {
        // Repay existing debt, withdraw old collateral
        // Swap to new collateral, deposit, re-borrow
    }
}