package.json

{
  "name": "paraswap_api_trade",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "dependencies": {
    "bignumber.js": "^9.0.1",
    "axios": "^0.19.0"
  }
}

paraswap_api_trade.js

const axios = require('axios');
const BN = require('bignumber.js');
const dotenv = require('dotenv');
dotenv.config();

const API_URL = 'https://apiv4.paraswap.io/v2';
const USER_ADDRESS = process.env.USER_ADDRESS;
const NULL_ADDRESS = '0x0000000000000000000000000000000000000000';

const referrer = 'chucknorris';
const SLIPPAGE = 1;//1%

const networks = {
  MAINNET: 1,
  POLYGON: 137,
};

const tokens = {
  [networks.MAINNET]: [
    {
      'decimals': 18,
      'symbol': 'ETH',
      'address': '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
    },
    {
      'decimals': 6,
      'symbol': 'USDC',
      'address': '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48',
    },
    {
      'decimals': 18,
      'symbol': 'DAI',
      'address': '0x6B175474E89094C44Da98b954EedeAC495271d0F',
    },
  ],
  [networks.POLYGON]: [
    {
      'decimals': 18,
      'symbol': 'MATIC',
      'address': '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
    },
    {
      'decimals': 8,
      'symbol': 'WBTC',
      'address': '0x1bfd67037b42cf73acf2047067bd4f2c47d9bfd6',
    },
  ],
};

function t(symbol, network) {
  network = network || networks.MAINNET;

  return tokens[network].find(t => t.symbol === symbol);
}

class ParaSwapper {
  constructor(network) {
    this.network = network;
  }

  async getRate(from, to, fromAmount) {
    const pricesURL = `${API_URL}/prices/?from=${from.address}&to=${to.address}&amount=${fromAmount}&fromDecimals=${from.decimals}&toDecimals=${to.decimals}&side=SELL&network=${this.network}`;

    const { data: { priceRoute } } = await axios.get(pricesURL, { headers: { 'X-Partner': referrer } });

    return priceRoute;
  }

  async buildSwap(from, to, srcAmount, minAmount, priceRoute) {
    const txURL = `${API_URL}/transactions/${this.network}`;

    const txConfig = {
      priceRoute,
      srcToken: from.address,
      srcDecimals: from.decimals,
      destToken: to.address,
      destDecimals: to.decimals,
      srcAmount,
      destAmount: minAmount,
      userAddress: USER_ADDRESS,
      referrer,
      receiver: NULL_ADDRESS,
    };

    const { data } = await axios.post(txURL, txConfig);

    return data;
  }
}

async function swap(_srcAmount, from, to, network) {
  try {
    const srcAmount = new BN(_srcAmount).times(10 ** from.decimals).toFixed(0);

    const ps = new ParaSwapper(network);

    const priceRoute = await ps.getRate(from, to, srcAmount);

    const minAmount = new BN(priceRoute.destAmount).times(1 - SLIPPAGE / 100).toFixed(0);

    const transaction = await ps.buildSwap(from, to, srcAmount, minAmount, priceRoute);

    console.log('transaction', transaction);

  } catch (error) {
    console.error(error.response.data);
  }
}

/*
swap(
  1,
  t("ETH", networks.MAINNET),
  t("DAI", networks.MAINNET),
  networks.MAINNET
);
*/

swap(
  1,
  t('MATIC', networks.POLYGON),
  t('WBTC', networks.POLYGON),
  networks.POLYGON,
);