Uniswap V3 Flashloans and Arbitrage

01_deployContracts.js

const { Contract, ContractFactory, utils, BigNumber } = require("ethers")
const WETH9 = require("../WETH9.json")

const artifacts = {
  UniswapV3Factory: require("@uniswap/v3-core/artifacts/contracts/UniswapV3Factory.sol/UniswapV3Factory.json"),
  SwapRouter: require("@uniswap/v3-periphery/artifacts/contracts/SwapRouter.sol/SwapRouter.json"),
  NFTDescriptor: require("@uniswap/v3-periphery/artifacts/contracts/libraries/NFTDescriptor.sol/NFTDescriptor.json"),
  NonfungibleTokenPositionDescriptor: require("@uniswap/v3-periphery/artifacts/contracts/NonfungibleTokenPositionDescriptor.sol/NonfungibleTokenPositionDescriptor.json"),
  NonfungiblePositionManager: require("@uniswap/v3-periphery/artifacts/contracts/NonfungiblePositionManager.sol/NonfungiblePositionManager.json"),
  WETH9,
};

const linkLibraries = ({ bytecode, linkReferences }, libraries) => {
  Object.keys(linkReferences).forEach((fileName) => {
    Object.keys(linkReferences[fileName]).forEach((contractName) => {
      if (!libraries.hasOwnProperty(contractName)) {
        throw new Error(`Missing link library name ${contractName}`)
      }
      const address = utils
        .getAddress(libraries[contractName])
        .toLowerCase()
        .slice(2)
      linkReferences[fileName][contractName].forEach(
        ({ start, length }) => {
          const start2 = 2 + start * 2
          const length2 = length * 2
          bytecode = bytecode
            .slice(0, start2)
            .concat(address)
            .concat(bytecode.slice(start2 + length2, bytecode.length))
        }
      )
    })
  })
  return bytecode
}

async function main() {
  const [owner] = await ethers.getSigners();

  Weth = new ContractFactory(artifacts.WETH9.abi, artifacts.WETH9.bytecode, owner);
  weth = await Weth.deploy();

  Factory = new ContractFactory(artifacts.UniswapV3Factory.abi, artifacts.UniswapV3Factory.bytecode, owner);
  factory = await Factory.deploy();

  SwapRouter = new ContractFactory(artifacts.SwapRouter.abi, artifacts.SwapRouter.bytecode, owner);
  swapRouter = await SwapRouter.deploy(factory.address, weth.address);

  NFTDescriptor = new ContractFactory(artifacts.NFTDescriptor.abi, artifacts.NFTDescriptor.bytecode, owner);
  nftDescriptor = await NFTDescriptor.deploy();

  const linkedBytecode = linkLibraries(
    {
      bytecode: artifacts.NonfungibleTokenPositionDescriptor.bytecode,
      linkReferences: {
        "NFTDescriptor.sol": {
          NFTDescriptor: [
            {
              length: 20,
              start: 1261,
            },
          ],
        },
      },
    },
    {
      NFTDescriptor: nftDescriptor.address,
    }
  );

  NonfungibleTokenPositionDescriptor = new ContractFactory(artifacts.NonfungibleTokenPositionDescriptor.abi, linkedBytecode, owner);
  nonfungibleTokenPositionDescriptor = await NonfungibleTokenPositionDescriptor.deploy(weth.address);

  NonfungiblePositionManager = new ContractFactory(artifacts.NonfungiblePositionManager.abi, artifacts.NonfungiblePositionManager.bytecode, owner);
  nonfungiblePositionManager = await NonfungiblePositionManager.deploy(factory.address, weth.address, nonfungibleTokenPositionDescriptor.address);

  console.log('WETH_ADDRESS=', `'${weth.address}'`)
  console.log('FACTORY_ADDRESS=', `'${factory.address}'`)
  console.log('SWAP_ROUTER_ADDRESS=', `'${swapRouter.address}'`)
  console.log('NFT_DESCRIPTOR_ADDRESS=', `'${nftDescriptor.address}'`)
  console.log('POSITION_DESCRIPTOR_ADDRESS=', `'${nonfungibleTokenPositionDescriptor.address}'`)
  console.log('POSITION_MANAGER_ADDRESS=', `'${nonfungiblePositionManager.address}'`)
}

/*
npx hardhat run --network localhost scripts/01_deployContracts.js
*/

main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

02_deployTokens.js

async function main() {
  const [owner, signer2] = await ethers.getSigners();

  Tether = await ethers.getContractFactory('Tether', owner);
  tether = await Tether.deploy();

  Usdc = await ethers.getContractFactory('UsdCoin', owner);
  usdc = await Usdc.deploy();

  await tether.connect(owner).mint(
    owner.address,
    ethers.utils.parseEther('100000')
  )
  await usdc.connect(owner).mint(
    owner.address,
    ethers.utils.parseEther('100000')
  )

  console.log('TETHER_ADDRESS=', `'${tether.address}'`)
  console.log('USDC_ADDRESS=', `'${usdc.address}'`)
}

/*
npx hardhat run --network localhost scripts/02_deployTokens.js
*/


main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

03_deployPools.js

// Token addresses
TETHER_ADDRESS= '0x0165878A594ca255338adfa4d48449f69242Eb8F'
USDC_ADDRESS= '0xa513E6E4b8f2a923D98304ec87F64353C4D5C853'

// Uniswap contract address
WETH_ADDRESS= '0x5FbDB2315678afecb367f032d93F642f64180aa3'
FACTORY_ADDRESS= '0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512'
SWAP_ROUTER_ADDRESS= '0x9fE46736679d2D9a65F0992F2272dE9f3c7fa6e0'
NFT_DESCRIPTOR_ADDRESS= '0xCf7Ed3AccA5a467e9e704C703E8D87F634fB0Fc9'
POSITION_DESCRIPTOR_ADDRESS= '0xDc64a140Aa3E981100a9becA4E685f962f0cF6C9'
POSITION_MANAGER_ADDRESS= '0x5FC8d32690cc91D4c39d9d3abcBD16989F875707'

const artifacts = {
  UniswapV3Factory: require("@uniswap/v3-core/artifacts/contracts/UniswapV3Factory.sol/UniswapV3Factory.json"),
  NonfungiblePositionManager: require("@uniswap/v3-periphery/artifacts/contracts/NonfungiblePositionManager.sol/NonfungiblePositionManager.json"),
};

const { Contract, BigNumber } = require("ethers")
const bn = require('bignumber.js')
bn.config({ EXPONENTIAL_AT: 999999, DECIMAL_PLACES: 40 })

const provider = waffle.provider;

function encodePriceSqrt(reserve1, reserve0) {
  return BigNumber.from(
    new bn(reserve1.toString())
      .div(reserve0.toString())
      .sqrt()
      .multipliedBy(new bn(2).pow(96))
      .integerValue(3)
      .toString()
  )
}

const nonfungiblePositionManager = new Contract(
  POSITION_MANAGER_ADDRESS,
  artifacts.NonfungiblePositionManager.abi,
  provider
)
const factory = new Contract(
  FACTORY_ADDRESS,
  artifacts.UniswapV3Factory.abi,
  provider
)

async function deployPool(token0, token1, fee, price) {
  const [owner] = await ethers.getSigners();
  await nonfungiblePositionManager.connect(owner).createAndInitializePoolIfNecessary(
    token0,
    token1,
    fee,
    price,
    { gasLimit: 5000000 }
  )
  const poolAddress = await factory.connect(owner).getPool(
    token0,
    token1,
    fee,
  )
  return poolAddress
}


async function main() {
  const usdtUsdc500 = await deployPool(TETHER_ADDRESS, USDC_ADDRESS, 500, encodePriceSqrt(1, 1))
  const usdtUsdc3000 = await deployPool(TETHER_ADDRESS, USDC_ADDRESS, 3000, encodePriceSqrt(1, 2))
  const usdtUsdc10000 = await deployPool(TETHER_ADDRESS, USDC_ADDRESS, 10000, encodePriceSqrt(2, 1))

  console.log('USDT_USDC_500=', `'${usdtUsdc500}'`)
  console.log('USDT_USDC_3000=', `'${usdtUsdc3000}'`)
  console.log('USDT_USDC_10000=', `'${usdtUsdc10000}'`)
}

/*
npx hardhat run --network localhost scripts/03_deployPools.js
*/

main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

04_addLiquidity.js

// Uniswap contract addresses
WETH_ADDRESS= '0x5FbDB2315678afecb367f032d93F642f64180aa3'
FACTORY_ADDRESS= '0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512'
SWAP_ROUTER_ADDRESS= '0x9fE46736679d2D9a65F0992F2272dE9f3c7fa6e0'
NFT_DESCRIPTOR_ADDRESS= '0xCf7Ed3AccA5a467e9e704C703E8D87F634fB0Fc9'
POSITION_DESCRIPTOR_ADDRESS= '0xDc64a140Aa3E981100a9becA4E685f962f0cF6C9'
POSITION_MANAGER_ADDRESS= '0x5FC8d32690cc91D4c39d9d3abcBD16989F875707'

// Pool addresses
USDT_USDC_500= '0x1FA8DDa81477A5b6FA1b2e149e93ed9C7928992F'
USDT_USDC_3000= '0x3B00F82071576B8489A6e3df223dcC0e937841d1'
USDT_USDC_10000= '0xb09EB46A30889ae3cE4AFa5d8ebD136B4f389B85'

// Token addresses
TETHER_ADDRESS= '0x0165878A594ca255338adfa4d48449f69242Eb8F'
USDC_ADDRESS= '0xa513E6E4b8f2a923D98304ec87F64353C4D5C853'

const artifacts = {
  NonfungiblePositionManager: require("@uniswap/v3-periphery/artifacts/contracts/NonfungiblePositionManager.sol/NonfungiblePositionManager.json"),
  Usdt: require("../artifacts/contracts/Tether.sol/Tether.json"),
  Usdc: require("../artifacts/contracts/UsdCoin.sol/UsdCoin.json"),
  UniswapV3Pool: require("@uniswap/v3-core/artifacts/contracts/UniswapV3Pool.sol/UniswapV3Pool.json"),
};

const { Contract } = require("ethers")
const { Token } = require('@uniswap/sdk-core')
const { Pool, Position, nearestUsableTick } = require('@uniswap/v3-sdk')

async function getPoolData(poolContract) {
  const [tickSpacing, fee, liquidity, slot0] = await Promise.all([
    poolContract.tickSpacing(),
    poolContract.fee(),
    poolContract.liquidity(),
    poolContract.slot0(),
  ])

  return {
    tickSpacing: tickSpacing,
    fee: fee,
    liquidity: liquidity,
    sqrtPriceX96: slot0[0],
    tick: slot0[1],
  }
}

LIQUIDITY = ethers.utils.parseEther('100')
DEADLINE = Math.floor(Date.now() / 1000) + (60 * 10)
POOL_ADDRESSES = [USDT_USDC_500, USDT_USDC_3000, USDT_USDC_10000] // ,


async function main() {
  const [owner, signer2] = await ethers.getSigners();
  const provider = waffle.provider;

  const nonfungiblePositionManager = new Contract(
    POSITION_MANAGER_ADDRESS,
    artifacts.NonfungiblePositionManager.abi,
    provider
  )
  const usdtContract = new Contract(TETHER_ADDRESS,artifacts.Usdt.abi,provider)
  const usdcContract = new Contract(USDC_ADDRESS,artifacts.Usdc.abi,provider)

  await usdtContract.connect(owner).approve(POSITION_MANAGER_ADDRESS, ethers.utils.parseEther('9999999'))
  await usdcContract.connect(owner).approve(POSITION_MANAGER_ADDRESS, ethers.utils.parseEther('9999999'))

  const UsdtToken = new Token(31337, TETHER_ADDRESS, 18, 'USDT', 'Tether')
  const UsdcToken = new Token(31337, USDC_ADDRESS, 18, 'USDC', 'UsdCoin')

  const poolContract1 = new Contract(USDT_USDC_500, artifacts.UniswapV3Pool.abi, provider)
  const poolContract2 = new Contract(USDT_USDC_3000, artifacts.UniswapV3Pool.abi, provider)
  const poolContract3 = new Contract(USDT_USDC_10000, artifacts.UniswapV3Pool.abi, provider)

  const poolData = {}
  poolData[USDT_USDC_500] = await getPoolData(poolContract1)
  poolData[USDT_USDC_3000] = await getPoolData(poolContract2)
  poolData[USDT_USDC_10000] = await getPoolData(poolContract3)

  // appears I cannot interact with contracts in the async map
  const mintParams = {}
  POOL_ADDRESSES.map(async poolAddress => {
    pd = poolData[poolAddress]

    const poolObj = new Pool(
      UsdtToken,
      UsdcToken,
      pd.fee,
      pd.sqrtPriceX96.toString(),
      pd.liquidity.toString(),
      pd.tick
    )

    const tickLower = nearestUsableTick(pd.tick, pd.tickSpacing) - pd.tickSpacing * 100
    const tickUpper = nearestUsableTick(pd.tick, pd.tickSpacing) + pd.tickSpacing * 100

    const positionObj = new Position({
      pool: poolObj,
      liquidity: LIQUIDITY,
      tickLower: tickLower,
      tickUpper: tickUpper,
    })

    const { amount0: amount0Desired, amount1: amount1Desired} = positionObj.mintAmounts
    const params = {
      token0: TETHER_ADDRESS,
      token1: USDC_ADDRESS,
      fee: pd.fee,
      tickLower: tickLower,
      tickUpper: tickUpper,
      amount0Desired: amount0Desired.toString(),
      amount1Desired: amount1Desired.toString(),
      amount0Min: 0,
      amount1Min: 0,
      recipient: signer2.address,
      deadline: DEADLINE
    }

    mintParams[poolAddress] = params
  })

  const tx1 = await nonfungiblePositionManager.connect(owner).mint(mintParams[USDT_USDC_500], { gasLimit: '1000000' })
  await tx1.wait()

  const tx2 = await nonfungiblePositionManager.connect(owner).mint(mintParams[USDT_USDC_3000], { gasLimit: '1000000' })
  await tx2.wait()

  const tx3 = await nonfungiblePositionManager.connect(owner).mint(mintParams[USDT_USDC_10000], { gasLimit: '1000000' })
  await tx3.wait()
  console.log('done')
}

/*
npx hardhat run --network localhost scripts/04_addLiquidity.js
*/

main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

05_checkLiquidity.js

// pool
USDT_USDC_500= '0x1FA8DDa81477A5b6FA1b2e149e93ed9C7928992F'
USDT_USDC_3000= '0x3B00F82071576B8489A6e3df223dcC0e937841d1'
USDT_USDC_10000= '0xb09EB46A30889ae3cE4AFa5d8ebD136B4f389B85'

const UniswapV3Pool = require("@uniswap/v3-core/artifacts/contracts/UniswapV3Pool.sol/UniswapV3Pool.json")
const { Contract, BigNumber } = require("ethers")

async function getPoolData(poolContract) {
  const [tickSpacing, fee, liquidity, slot0] = await Promise.all([
    poolContract.tickSpacing(),
    poolContract.fee(),
    poolContract.liquidity(),
    poolContract.slot0(),
  ])

  const sqrtPriceX96 = slot0[0]
  const numerator = BigNumber.from(sqrtPriceX96).pow(2)
  const denominator = BigNumber.from(2).pow(192)

  const priceRatio = numerator/denominator
  return {
    tickSpacing: tickSpacing,
    fee: fee,
    liquidity: liquidity.toString(),
    sqrtPriceX96: sqrtPriceX96.toString(),
    priceRatio: priceRatio.toString(),
    tick: slot0[1],
  }
}


async function main() {
  const provider = waffle.provider;

  const poolContract500 = new Contract(USDT_USDC_500, UniswapV3Pool.abi, provider)
  const poolData500 = await getPoolData(poolContract500)
  console.log('poolData500', poolData500)

  const poolContract3000 = new Contract(USDT_USDC_3000, UniswapV3Pool.abi, provider)
  const poolData3000 = await getPoolData(poolContract3000)
  console.log('poolData3000', poolData3000)

  const poolContract10000 = new Contract(USDT_USDC_10000, UniswapV3Pool.abi, provider)
  const poolData10000 = await getPoolData(poolContract10000)
  console.log('poolData10000', poolData10000)
}

/*
npx hardhat run --network localhost scripts/05_checkLiquidity.js
*/

main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

06_flashSwap.js

const { Contract } = require("ethers")

// Uniswap contract address
WETH_ADDRESS= '0x5FbDB2315678afecb367f032d93F642f64180aa3'
FACTORY_ADDRESS= '0xe7f1725E7734CE288F8367e1Bb143E90bb3F0512'
SWAP_ROUTER_ADDRESS= '0x9fE46736679d2D9a65F0992F2272dE9f3c7fa6e0'
NFT_DESCRIPTOR_ADDRESS= '0xCf7Ed3AccA5a467e9e704C703E8D87F634fB0Fc9'
POSITION_DESCRIPTOR_ADDRESS= '0xDc64a140Aa3E981100a9becA4E685f962f0cF6C9'
POSITION_MANAGER_ADDRESS= '0x5FC8d32690cc91D4c39d9d3abcBD16989F875707'

// Token addresses
TETHER_ADDRESS= '0x0165878A594ca255338adfa4d48449f69242Eb8F'
USDC_ADDRESS= '0xa513E6E4b8f2a923D98304ec87F64353C4D5C853'

const WETH9 = require("../WETH9.json")
const artifacts = {
  UniswapV3Factory: require("@uniswap/v3-core/artifacts/contracts/UniswapV3Factory.sol/UniswapV3Factory.json"),
  SwapRouter: require("@uniswap/v3-periphery/artifacts/contracts/SwapRouter.sol/SwapRouter.json"),
  NFTDescriptor: require("@uniswap/v3-periphery/artifacts/contracts/libraries/NFTDescriptor.sol/NFTDescriptor.json"),
  NonfungibleTokenPositionDescriptor: require("@uniswap/v3-periphery/artifacts/contracts/NonfungibleTokenPositionDescriptor.sol/NonfungibleTokenPositionDescriptor.json"),
  NonfungiblePositionManager: require("@uniswap/v3-periphery/artifacts/contracts/NonfungiblePositionManager.sol/NonfungiblePositionManager.json"),
  Usdt: require("../artifacts/contracts/Tether.sol/Tether.json"),
  Usdc: require("../artifacts/contracts/UsdCoin.sol/UsdCoin.json"),
  WETH9,
};

const toEth = (wei) => ethers.utils.formatEther(wei)

async function main() {
  const provider = waffle.provider;
  const [owner, signer2] = await ethers.getSigners();

  Flash = await ethers.getContractFactory('PairFlash', signer2);
  flash = await Flash.deploy(SWAP_ROUTER_ADDRESS, FACTORY_ADDRESS, WETH_ADDRESS);
  console.log('flash', flash.address)

  const usdtContract = new Contract(TETHER_ADDRESS,artifacts.Usdt.abi,provider)
  const usdcContract = new Contract(USDC_ADDRESS,artifacts.Usdc.abi,provider)

  let usdtBalance = await usdtContract.connect(provider).balanceOf(signer2.address)
  let usdcBalance = await usdcContract.connect(provider).balanceOf(signer2.address)
  console.log('-------------------- BEFORE')
  console.log('usdtBalance', toEth(usdtBalance.toString()))
  console.log('usdcBalance', toEth(usdcBalance.toString()))
  console.log('--------------------')

  const tx = await flash.connect(signer2).initFlash(
    [
      TETHER_ADDRESS,
      USDC_ADDRESS,
      500,
      ethers.utils.parseEther('1'),
      ethers.utils.parseEther('1'),
      3000,
      10000
    ],
    { gasLimit: ethers.utils.hexlify(1000000) }
  );
  await tx.wait()

  usdtBalance = await usdtContract.connect(provider).balanceOf(signer2.address)
  usdcBalance = await usdcContract.connect(provider).balanceOf(signer2.address)
  console.log('-------------------- AFTER')
  console.log('usdtBalance', toEth(usdtBalance.toString()))
  console.log('usdcBalance', toEth(usdcBalance.toString()))
  console.log('--------------------')
}

/*
npx hardhat run --network localhost scripts/06_flashSwap.js
*/

main()
  .then(() => process.exit(0))
  .catch((error) => {
    console.error(error);
    process.exit(1);
  });

hardhat.config.js

require("@nomiclabs/hardhat-waffle");

module.exports = {
  solidity: {
    compilers: [
      { version: "0.7.6" },
    ],
    settings: {
      optimizer: {
        enabled: true,
        runs: 5000,
        details: { yul: false },
      },
    }
  },
};

package.json

{
  "name": "solidity-flashswap-1",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@nomiclabs/hardhat-ethers": "^2.2.1",
    "@nomiclabs/hardhat-waffle": "^2.0.3",
    "@openzeppelin/contracts": "^3.4.0",
    "@uniswap/v3-periphery": "^1.0.1",
    "@uniswap/v3-sdk": "^3.9.0",
    "bignumber.js": "^9.1.0",
    "ethereum-waffle": "^3.4.4",
    "ethers": "^5.7.2",
    "hardhat": "^2.12.2"
  }
}

PairFlash.sol

// SPDX-License-Identifier: GPL-2.0-or-later
pragma solidity =0.7.6;
pragma abicoder v2;

import '@uniswap/v3-core/contracts/interfaces/callback/IUniswapV3FlashCallback.sol';
import '@uniswap/v3-core/contracts/libraries/LowGasSafeMath.sol';

import '@uniswap/v3-periphery/contracts/base/PeripheryPayments.sol';
import '@uniswap/v3-periphery/contracts/base/PeripheryImmutableState.sol';
import '@uniswap/v3-periphery/contracts/libraries/PoolAddress.sol';
import '@uniswap/v3-periphery/contracts/libraries/CallbackValidation.sol';
import '@uniswap/v3-periphery/contracts/libraries/TransferHelper.sol';
import '@uniswap/v3-periphery/contracts/interfaces/ISwapRouter.sol';

contract PairFlash is IUniswapV3FlashCallback, PeripheryImmutableState, PeripheryPayments {
    using LowGasSafeMath for uint256;
    using LowGasSafeMath for int256;

    ISwapRouter public immutable swapRouter;

    constructor(
        ISwapRouter _swapRouter,
        address _factory,
        address _WETH9
    ) PeripheryImmutableState(_factory, _WETH9) {
        swapRouter = _swapRouter;
    }

    function uniswapV3FlashCallback(
        uint256 fee0,
        uint256 fee1,
        bytes calldata data
    ) external override {
        FlashCallbackData memory decoded = abi.decode(data, (FlashCallbackData));
        CallbackValidation.verifyCallback(factory, decoded.poolKey);

        address token0 = decoded.poolKey.token0;
        address token1 = decoded.poolKey.token1;

        TransferHelper.safeApprove(token0, address(swapRouter), decoded.amount0);
        TransferHelper.safeApprove(token1, address(swapRouter), decoded.amount1);

        uint256 amount1Min = LowGasSafeMath.add(decoded.amount1, fee1);
        uint256 amount0Min = LowGasSafeMath.add(decoded.amount0, fee0);

        uint256 amountOut0 =
            swapRouter.exactInputSingle(
                ISwapRouter.ExactInputSingleParams({
                    tokenIn: token1,
                    tokenOut: token0,
                    fee: decoded.poolFee2,
                    recipient: address(this),
                    deadline: block.timestamp,
                    amountIn: decoded.amount1,
                    amountOutMinimum: amount0Min,
                    sqrtPriceLimitX96: 0
                })
            );

        uint256 amountOut1 =
            swapRouter.exactInputSingle(
                ISwapRouter.ExactInputSingleParams({
                    tokenIn: token0,
                    tokenOut: token1,
                    fee: decoded.poolFee3,
                    recipient: address(this),
                    deadline: block.timestamp,
                    amountIn: decoded.amount0,
                    amountOutMinimum: amount1Min,
                    sqrtPriceLimitX96: 0
                })
            );

        uint256 amount0Owed = LowGasSafeMath.add(decoded.amount0, fee0);
        uint256 amount1Owed = LowGasSafeMath.add(decoded.amount1, fee1);

        TransferHelper.safeApprove(token0, address(this), amount0Owed);
        TransferHelper.safeApprove(token1, address(this), amount1Owed);

        if (amount0Owed > 0) pay(token0, address(this), msg.sender, amount0Owed);
        if (amount1Owed > 0) pay(token1, address(this), msg.sender, amount1Owed);

        if (amountOut0 > amount0Owed) {
            uint256 profit0 = LowGasSafeMath.sub(amountOut0, amount0Owed);

            TransferHelper.safeApprove(token0, address(this), profit0);
            pay(token0, address(this), decoded.payer, profit0);
        }
        if (amountOut1 > amount1Owed) {
            uint256 profit1 = LowGasSafeMath.sub(amountOut1, amount1Owed);
            TransferHelper.safeApprove(token0, address(this), profit1);
            pay(token1, address(this), decoded.payer, profit1);
        }
    }

    struct FlashParams {
        address token0;
        address token1;
        uint24 fee1;
        uint256 amount0;
        uint256 amount1;
        uint24 fee2;
        uint24 fee3;
    }

    struct FlashCallbackData {
        uint256 amount0;
        uint256 amount1;
        address payer;
        PoolAddress.PoolKey poolKey;
        uint24 poolFee2;
        uint24 poolFee3;
    }

    function initFlash(FlashParams memory params) external {
        // {token0: token0, token1: token1, fee: fee}
        PoolAddress.PoolKey memory poolKey = PoolAddress.PoolKey({token0: params.token0, token1: params.token1, fee: params.fee1});
        IUniswapV3Pool pool = IUniswapV3Pool(PoolAddress.computeAddress(factory, poolKey));

        pool.flash(
            address(this),
            params.amount0,
            params.amount1,
            abi.encode(
                FlashCallbackData({
                    amount0: params.amount0,
                    amount1: params.amount1,
                    payer: msg.sender,
                    poolKey: poolKey,
                    poolFee2: params.fee2,
                    poolFee3: params.fee3
                })
            )
        );
    }
}

Tether.sol

// SPDX-License-Identifier: GPL-2.0-or-later
pragma solidity =0.7.6;

import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
import "@openzeppelin/contracts/access/Ownable.sol";

contract Tether is ERC20, Ownable {
  constructor() ERC20('Tether', 'USDT') {}

  function mint(address to, uint256 amount) public onlyOwner {
    _mint(to, amount);
  }
}

UsdCoin.sol

// SPDX-License-Identifier: GPL-2.0-or-later
pragma solidity =0.7.6;

import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
import "@openzeppelin/contracts/access/Ownable.sol";

contract UsdCoin is ERC20, Ownable {
  constructor() ERC20('UsdCoin', 'USDC') {}

  function mint(address to, uint256 amount) public onlyOwner {
    _mint(to, amount);
  }
}

WETH9.json

{
  "bytecode": 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  "abi": [
    {
      "constant": true,
      "inputs": [],
      "name": "name",
      "outputs": [{ "name": "", "type": "string" }],
      "payable": false,
      "stateMutability": "view",
      "type": "function"
    },
    {
      "constant": false,
      "inputs": [
        { "name": "guy", "type": "address" },
        { "name": "wad", "type": "uint256" }
      ],
      "name": "approve",
      "outputs": [{ "name": "", "type": "bool" }],
      "payable": false,
      "stateMutability": "nonpayable",
      "type": "function"
    },
    {
      "constant": true,
      "inputs": [],
      "name": "totalSupply",
      "outputs": [{ "name": "", "type": "uint256" }],
      "payable": false,
      "stateMutability": "view",
      "type": "function"
    },
    {
      "constant": false,
      "inputs": [
        { "name": "src", "type": "address" },
        { "name": "dst", "type": "address" },
        { "name": "wad", "type": "uint256" }
      ],
      "name": "transferFrom",
      "outputs": [{ "name": "", "type": "bool" }],
      "payable": false,
      "stateMutability": "nonpayable",
      "type": "function"
    },
    {
      "constant": false,
      "inputs": [{ "name": "wad", "type": "uint256" }],
      "name": "withdraw",
      "outputs": [],
      "payable": false,
      "stateMutability": "nonpayable",
      "type": "function"
    },
    {
      "constant": true,
      "inputs": [],
      "name": "decimals",
      "outputs": [{ "name": "", "type": "uint8" }],
      "payable": false,
      "stateMutability": "view",
      "type": "function"
    },
    {
      "constant": true,
      "inputs": [{ "name": "", "type": "address" }],
      "name": "balanceOf",
      "outputs": [{ "name": "", "type": "uint256" }],
      "payable": false,
      "stateMutability": "view",
      "type": "function"
    },
    {
      "constant": true,
      "inputs": [],
      "name": "symbol",
      "outputs": [{ "name": "", "type": "string" }],
      "payable": false,
      "stateMutability": "view",
      "type": "function"
    },
    {
      "constant": false,
      "inputs": [
        { "name": "dst", "type": "address" },
        { "name": "wad", "type": "uint256" }
      ],
      "name": "transfer",
      "outputs": [{ "name": "", "type": "bool" }],
      "payable": false,
      "stateMutability": "nonpayable",
      "type": "function"
    },
    {
      "constant": false,
      "inputs": [],
      "name": "deposit",
      "outputs": [],
      "payable": true,
      "stateMutability": "payable",
      "type": "function"
    },
    {
      "constant": true,
      "inputs": [
        { "name": "", "type": "address" },
        { "name": "", "type": "address" }
      ],
      "name": "allowance",
      "outputs": [{ "name": "", "type": "uint256" }],
      "payable": false,
      "stateMutability": "view",
      "type": "function"
    },
    { "payable": true, "stateMutability": "payable", "type": "fallback" },
    {
      "anonymous": false,
      "inputs": [
        { "indexed": true, "name": "src", "type": "address" },
        { "indexed": true, "name": "guy", "type": "address" },
        { "indexed": false, "name": "wad", "type": "uint256" }
      ],
      "name": "Approval",
      "type": "event"
    },
    {
      "anonymous": false,
      "inputs": [
        { "indexed": true, "name": "src", "type": "address" },
        { "indexed": true, "name": "dst", "type": "address" },
        { "indexed": false, "name": "wad", "type": "uint256" }
      ],
      "name": "Transfer",
      "type": "event"
    },
    {
      "anonymous": false,
      "inputs": [
        { "indexed": true, "name": "dst", "type": "address" },
        { "indexed": false, "name": "wad", "type": "uint256" }
      ],
      "name": "Deposit",
      "type": "event"
    },
    {
      "anonymous": false,
      "inputs": [
        { "indexed": true, "name": "src", "type": "address" },
        { "indexed": false, "name": "wad", "type": "uint256" }
      ],
      "name": "Withdrawal",
      "type": "event"
    }
  ]
}