What is Flash Loan? How to integrate flash loan functionality on the frontend?
考察点：高级DeFi概念。
答案：
闪电贷是DeFi的创新机制，允许在单个交易中借入大量资金而无需抵押，但必须在同一交易中归还。主要用于套利、债务重组、清算等场景。
工作原理：
- 在一个交易中借入资金
- 执行套利或其他操作
- 获得利润后归还本金和手续费
- 如果无法归还，整个交易回滚
前端集成实现：
const FLASHLOAN_ABI = [
"function flashLoan(address receiverAddress, address[] assets, uint256[] amounts, uint256[] modes, address onBehalfOf, bytes params, uint16 referralCode)",
"function executeOperation(address[] assets, uint256[] amounts, uint256[] premiums, address initiator, bytes params) external returns (bool)"
];
class FlashLoanExecutor {
constructor(provider, signer, aavePool) {
this.provider = provider;
this.signer = signer;
this.aavePool = aavePool;
}
async deployFlashLoanContract(strategy) {
const contractFactory = new ethers.ContractFactory(
FLASHLOAN_CONTRACT_ABI,
FLASHLOAN_CONTRACT_BYTECODE,
this.signer
);
const contract = await contractFactory.deploy(
this.aavePool.address,
strategy.targetProtocols
);
return await contract.deployed();
}
async executeArbitrage(params) {
const {
asset,
amount,
exchanges,
expectedProfit
} = params;
const executeParams = ethers.utils.defaultAbiCoder.encode(
['address[]', 'uint256[]', 'uint256'],
[exchanges, [amount], expectedProfit]
);
try {
const tx = await this.aavePool.flashLoan(
this.flashLoanContract.address,
[asset],
[amount],
[0],
this.signer.address,
executeParams,
0
);
return await tx.wait();
} catch (error) {
throw new Error(`闪电贷执行失败: ${error.message}`);
}
}
async findArbitrageOpportunity() {
const exchanges = ['uniswap', 'sushiswap', 'curve'];
const assets = ['USDC', 'DAI', 'USDT'];
const opportunities = [];
for (const asset of assets) {
const prices = await Promise.all(
exchanges.map(ex => this.getPrice(ex, asset))
);
const maxPrice = Math.max(...prices);
const minPrice = Math.min(...prices);
const priceDiff = ((maxPrice - minPrice) / minPrice) * 100;
if (priceDiff > 0.5) {
opportunities.push({
asset,
buyExchange: exchanges[prices.indexOf(minPrice)],
sellExchange: exchanges[prices.indexOf(maxPrice)],
priceDiff,
estimatedProfit: this.calculateProfit(priceDiff, 100000)
});
}
}
return opportunities.sort((a, b) => b.estimatedProfit - a.estimatedProfit);
}
}
const FlashLoanInterface = () => {
const [executor] = useState(new FlashLoanExecutor(provider, signer, aavePool));
const [opportunities, setOpportunities] = useState([]);
const [executing, setExecuting] = useState(false);
const [results, setResults] = useState([]);
useEffect(() => {
const scanOpportunities = async () => {
const opps = await executor.findArbitrageOpportunity();
setOpportunities(opps);
};
scanOpportunities();
const interval = setInterval(scanOpportunities, 30000);
return () => clearInterval(interval);
}, [executor]);
const executeFlashLoan = async (opportunity) => {
setExecuting(true);
try {
const result = await executor.executeArbitrage({
asset: opportunity.asset,
amount: ethers.utils.parseUnits("100000", 6),
exchanges: [opportunity.buyExchange, opportunity.sellExchange],
expectedProfit: opportunity.estimatedProfit
});
setResults(prev => [...prev, {
...opportunity,
txHash: result.transactionHash,
success: true,
timestamp: Date.now()
}]);
alert(`套利成功！交易哈希: ${result.transactionHash}`);
} catch (error) {
alert(`套利失败: ${error.message}`);
setResults(prev => [...prev, {
...opportunity,
success: false,
error: error.message,
timestamp: Date.now()
}]);
} finally {
setExecuting(false);
}
};
return (
<div className="flashloan-interface">
<h2>闪电贷套利</h2>
<div className="opportunities">
<h3>套利机会</h3>
{opportunities.map((opp, index) => (
<div key={index} className="opportunity-card">
<div>资产: {opp.asset}</div>
<div>价差: {opp.priceDiff.toFixed(3)}%</div>
<div>买入: {opp.buyExchange}</div>
<div>卖出: {opp.sellExchange}</div>
<div>预期利润: ${opp.estimatedProfit.toFixed(2)}</div>
<button
onClick={() => executeFlashLoan(opp)}
disabled={executing}
>
{executing ? '执行中...' : '执行套利'}
</button>
</div>
))}
</div>
<div className="results">
<h3>执行历史</h3>
{results.map((result, index) => (
<div key={index} className={`result ${result.success ? 'success' : 'error'}`}>
<div>{new Date(result.timestamp).toLocaleString()}</div>
<div>{result.asset} - {result.success ? '成功' : '失败'}</div>
{result.txHash && <div>交易: {result.txHash}</div>}
{result.error && <div>错误: {result.error}</div>}
</div>
))}
</div>
</div>
);
};
const FLASHLOAN_STRATEGY_CONTRACT = `
pragma solidity ^0.8.0;
contract ArbitrageBot {
address private aavePool;
function executeOperation(
address[] calldata assets,
uint256[] calldata amounts,
uint256[] calldata premiums,
address initiator,
bytes calldata params
) external returns (bool) {
// 解析参数
(address[] memory exchanges, uint256[] memory tradeAmounts, uint256 expectedProfit) =
abi.decode(params, (address[], uint256[], uint256));
// 执行套利逻辑
uint256 profit = performArbitrage(assets[0], amounts[0], exchanges);
// 确保有足够资金还款
require(profit >= premiums[0], "Insufficient profit for repayment");
// 归还闪电贷
IERC20(assets[0]).transfer(msg.sender, amounts[0] + premiums[0]);
return true;
}
function performArbitrage(address asset, uint256 amount, address[] memory exchanges)
private returns (uint256 profit) {
// 具体套利实现
}
}
`;
使用场景：
- 套利交易：利用不同DEX间价差
- 债务重组：更换借贷协议获得更优利率
- 清算保护：防止自己的头寸被清算
- 资本效率：无需预付资金执行大额交易