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prints USDC/ETH trades from Uniswap to stdout
const { ethers } = require("ethers");
const provider = new ethers.providers.JsonRpcProvider("http://0.0.0.0:8545");
// https://info.uniswap.org/pair/0xb4e16d0168e52d35cacd2c6185b44281ec28c9dc
const uniswapUsdtWethExchange = "0xB4e16d0168e52d35CaCD2c6185b44281Ec28C9Dc";
// this ABI object works for both Uniswap and SushiSwap
const uniswapAbi = [
"event Swap(address indexed sender, uint amount0In, uint amount1In, uint amount0Out, uint amount1Out, address indexed to)",
];
function getAmountsFromSwapArgs(swapArgs) {
const { amount0In, amount0Out, amount1In, amount1Out } = swapArgs;
// 1. The eq method is for objects created
// from ethers.js BigNumber helper
// 2. Note, this code only handles simple one-to-one token swaps.
// (It's also possible to swap both token0 and token1 for token0 and token1)
let token0AmountBigDecimal = amount0In;
if (token0AmountBigDecimal.eq(0)) {
token0AmountBigDecimal = amount0Out;
}
let token1AmountBigDecimal = amount1In;
if (token1AmountBigDecimal.eq(0)) {
token1AmountBigDecimal = amount1Out;
}
return { token0AmountBigDecimal, token1AmountBigDecimal };
}
function convertSwapEventToPrice({ swapArgs, token0Decimals, token1Decimals }) {
const {
token0AmountBigDecimal,
token1AmountBigDecimal,
} = getAmountsFromSwapArgs(swapArgs);
const token0AmountFloat = parseFloat(
ethers.utils.formatUnits(token0AmountBigDecimal, token0Decimals)
);
const token1AmounFloat = parseFloat(
ethers.utils.formatUnits(token1AmountBigDecimal, token1Decimals)
);
if (token1AmounFloat > 0) {
const priceOfToken0InTermsOfToken1 = token0AmountFloat / token1AmounFloat;
return { price: priceOfToken0InTermsOfToken1, volume: token0AmountFloat };
}
return null;
}
const uniswapContract = new ethers.Contract(
uniswapUsdtWethExchange,
uniswapAbi,
provider
);
const filter = uniswapContract.filters.Swap();
uniswapContract.on(filter, (from, a0in, a0out, a1in, a1out, to, event) => {
const { price, volume } = convertSwapEventToPrice({
swapArgs: event.args,
// the USDC ERC20 uses 6 decimals
token0Decimals: 6,
// the WETH ERC20 uses 18 decimals
token1Decimals: 18,
});
console.log({ price, volume });
});
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