binance.util.js

import fetch from 'node-fetch';
import { handleResponse, median } from './helper.util.js';

function getRateDetails(currency, tradeType) {
  let params = {
    asset: 'USDT',
    fiat: currency,
    tradeType
  };
  if (currency === 'USD') {
    params = {
      ...params,
      ...{
        publisherType: 'merchant',
        merchantCheck: true
      }
    };
  }
  return getPriceDetails(params);
}

function getExchangeRates(currencies) {
  return Promise.all(
    currencies.split('|').map((currency) =>
      getExchangeRate(currency).then((price) => ({
        currency,
        price
      }))
    )
  );
}

function getExchangeRate(currency) {
  return new Promise(async (resolve, reject) => {
    try {
      const [buyRate, sellRate] = await Promise.all([
        getRate(currency, 'BUY'),
        getRate(currency, 'SELL')
      ]);
      resolve({
        buy: buyRate,
        sell: sellRate
      });
    } catch (error) {
      reject(error);
    }
  });
}

function getRate(currency, tradeType) {
  let params = {
    asset: 'USDT',
    fiat: currency,
    tradeType
  };
  if (currency === 'USD') {
    params = {
      ...params,
      ...{
        publisherType: 'merchant',
        merchantCheck: true
      }
    };
  }
  return getPrice(params);
}

function getPriceDetails(params) {
  return new Promise(async (resolve, reject) => {
    try {
      const { tradeType } = params;
      const prices = [];
      const ads = await getAds(params);
      ads.map((ad) => {
        prices.push(parseFloat(ad.adv.price));
      });
      const min = tradeType === 'SELL' ? prices.length - 1 : 0;
      const max = tradeType === 'SELL' ? 0 : prices.length - 1;
      resolve({
        min: prices[min],
        med: median(prices),
        max: prices[max]
      });
    } catch (error) {
      reject(error);
    }
  });
}

function getPrice(params) {
  return getAd({
    ...params,
    ...{
      page: 1,
      rows: 1
    }
  }).then(({ data }) => parseFloat(data[0].adv.price));
}

function getAds(params) {
  return new Promise(async (resolve, reject) => {
    try {
      const ads = [];
      const rowsPerPage = 20; //Max limit of rows per page is 20.
      let currentPage = 1;
      let totalPages;
      do {
        const { data, total } = await getAd({
          ...params,
          ...{
            page: currentPage,
            rows: rowsPerPage
          }
        });
        ads.push(...data);
        totalPages = totalPages ?? Math.ceil(total / rowsPerPage);
        currentPage++;
      } while (currentPage <= totalPages);
      resolve(ads);
    } catch (error) {
      reject(error);
    }
  });
}

function getAd(params) {
  return fetch('https://p2p.binance.com/bapi/c2c/v2/friendly/c2c/adv/search', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(params)
  })
    .then(handleResponse)
    .then(({ data }) => data);
}

export { getExchangeRates, getRateDetails };