Best way to swap ETH to WETH and buy token?

[Naografix]

Hello,

I play a little with Ethers to see how it works and I am confronted with a problem:

I created a test account on Ropsten and gave myself 2 ETH. And now i'm trying to find the best way to swap ETH to WETH and swap to the target token. I found nothing about it.

Can you help me?

This is my code base:

const ethers = require('ethers');

const DAI_ADDRESS = '0xad6d458402f60fd3bd25163575031acdce07538d';
const WETH_ADDRESS = '0xc778417e063141139fce010982780140aa0cd5ab';

const UNISWAP_FACTORY = '0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f';
const UNISWAP_ROUTER = '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D';
const MY_WALLET = '0x9965CB5fd7C765B6C396be2d1c7702f785c9e365';

const provider = new ethers.providers.WebSocketProvider('wss://ropsten.infura.io/ws/v3/');
const wallet = new ethers.Wallet('');
const account = wallet.connect(provider);

const router = new ethers.Contract(
    UNISWAP_ROUTER,
    [
        'function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts)',
        'function swapExactTokensForTokens(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline) external returns (uint[] memory amounts)'
    ],
    account
);

async function test() {
    const amountsIn = ethers.utils.parseUnits("0.01", "ether");
    console.log(amountsIn);
    const amountsOut  = await router.getAmountsOut(amountsIn, [WETH_ADDRESS, TOKEN]);
    const amountOutMin = amountsOut [1].sub(amountsOut [1].div(5));
    console.log(amountOutMin);

    const tx = await router.swapExactTokensForTokens(
        amountsIn,
        amountOutMin,
        [WETH_ADDRESS, TOKEN],
        MY_WALLET,
        Date.now() + 1000 * 60 * 5,
        {
            'gasLimit': 300000,
            'gasPrice': ethers.utils.parseUnits('25', 'gwei'),
        }
    );
    console.log(tx);
    const receipt = await tx.wait();
    console.log('Transaction receipt');
    console.log(receipt);
}

test();

[zemse]

Heya! To convert your ETH into WETH, you can directly use the deposit function on WETH9 contract. They have mentioned their ropsten address in readme (0xc778417e063141139fce010982780140aa0cd5ab).

[Naografix]

Hey, thank you for your answer but it's not exactly what I ask (or I just failed in my code :') )
Take a look!

I have ETH and I want to swap them to UNI.
So I understood I need to convert my ETH to WETH and swap to UNI, but with my code, it's considered like 3 distinct transactions

1 - Deposit
2 - Approve
3 - Swap

const routerContract = new ethers.Contract(
    UNISWAP_ROUTER,
    [
        'function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts)',
        'function swapExactTokensForTokens(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline) external returns (uint[] memory amounts)'
    ],
    account
);

const wethContract = new ethers.Contract(
    WETH_ADDRESS, 
    [
        'function deposit() public payable {}',
        'function approve(address spender, uint amount) external {}',
    ], 
    account);
const targetContract = new ethers.Contract(
    TOKEN,
    [
        'function approve(address spender, uint amount) public returns(bool)',
    ],
    account
);

async function test() {
    console.log("Calculating how many ether");
    const amountsIn = ethers.utils.parseUnits("0.1", "ether");

    await wethContract.deposit({value: amountsIn});
    await wethContract.approve(routerContract.address, amountsIn);
    
    console.log("Calculating how many tokens");
    const amountsOut = await routerContract.getAmountsOut(amountsIn, [WETH_ADDRESS, TOKEN]);
    const amountOutMin = amountsOut[1].sub(amountsOut[1].div(10));
    
    console.log("ok, trying to swap");
    const tx = await routerContract.swapExactTokensForTokens(
        amountsIn,
        amountOutMin,
        [WETH_ADDRESS, TOKEN],
        MY_WALLET,
        Date.now() + 1000 * 60 * 5,
        {
            'gasLimit': 300000,
            'gasPrice': ethers.utils.parseUnits('25', 'gwei'),
        }
    );
    console.log(tx);
    console.log("ok");
    const receipt = await tx.wait();
    console.log('Transaction receipt');
    console.log(receipt);
}

test();

EDIT: I'm looking for something like this

https://ropsten.etherscan.io/tx/0xa4d9ed99ecf74030687ce0546e23bf4fe9857d6c1aece24291c38babf7102e0c

Really thank you for your help!

[Naografix]

Ah! Finally I found this solution:

    const tx = await routerContract.swapExactETHForTokens(       
        amountOutMin,
        [WETH_ADDRESS, TOKEN],
        MY_WALLET,
        Date.now() + 1000 * 60 * 5,
        {
            'gasLimit': 300000,
            'gasPrice': ethers.utils.parseUnits('25', 'gwei'),
            'value': amountsIn,
        }
    );

[zemse]

Yeah there are two methods, swapExactETHForTokens and swapExactTokensForTokens. Keep in mind that the former costs slightly more since it also does the deposit. If you're gonna make this a lot of txs like this, to save gas you can deposit once with huge amount of ETH and get WETH. Then use the swapExactTokensForTokens in your script.