billboard-top-100.js

const request = require('request');
const cheerio = require('cheerio');
const moment = require('moment');

const BILLBOARD_BASE_URL = 'http://www.billboard.com';
const BILLBOARD_CHARTS_URL = `${BILLBOARD_BASE_URL}/charts/`;
const BILLBOARD_CHART_CATEGORY_URL_PREFIX = `${BILLBOARD_BASE_URL}/pmc-ajax/charts-fetch-all-chart/selected_category-`;
const BILLBOARD_CHART_CATEGORY_URL_SUFFIX = '/chart_type-weekly/';

function getChart(name, date, cb) {
  let chartName = name;
  let chartDate = date;
  let callback = cb;

  if (typeof name === 'function') {
    // if name not specified, default to hot-100 chart for current week,
    // and set callback method accordingly
    callback = name;
    chartName = 'hot-100';
    chartDate = '';
  }

  if (typeof date === 'function') {
    // if date not specified, default to specified chart for current week,
    // and set callback method accordingly
    callback = date;
    chartDate = '';
  }

  const chart = {};
  chart.songs = [];

  const requestURL = `${BILLBOARD_CHARTS_URL}${chartName}/${chartDate}`;
  request(requestURL, (error, response, html) => {
    if (error) {
      callback(error, null);
      return;
    }

    const $ = cheerio.load(html);

    let d = null;
    for (let i = 0; i < $('.c-heading').length; i += 1) {
      if ($('.c-heading')[i].children[0].data.includes('Week of ')) {
        d = moment(new Date($('.c-heading')[i].children[0].data.trim().slice('Week of '.length)));
        break;
      }
    }

    chart.week = d.format('YYYY-MM-DD');

    const prevWeek = d.subtract(7, 'days').format('YYYY-MM-DD');
    chart.previousWeek = {
      date: prevWeek,
      url: `${BILLBOARD_CHARTS_URL}${chartName}/${prevWeek}`,
    };

    const nextWeek = d.add(14, 'days').format('YYYY-MM-DD');
    chart.nextWeek = {
      date: nextWeek,
      url: `${BILLBOARD_CHARTS_URL}${chartName}/${nextWeek}`,
    };

    const chartItems = $('.o-chart-results-list-row-container');
    for (let i = 0; i < chartItems.length; i += 1) {
      const infoContainer = chartItems[i].children[1];
      const titleAndArtistContainer = infoContainer.children[7].children[1].children[1];
      const posInfo = infoContainer.children[7].children[1];

      const rank = parseInt(infoContainer.children[1].children[1].children[0].data.trim(), 10);
      const title = titleAndArtistContainer.children[1].children[0].data.trim();
      const artist = titleAndArtistContainer.children[3]
        ? titleAndArtistContainer.children[3].children[0].data.trim() : undefined;
      const cover = infoContainer.children[3].children[1].children[1].children[1].attribs['data-lazy-src'];
      const position = {
        positionLastWeek: parseInt(posInfo.children[7].children[1].children[0].data.trim(), 10),
        peakPosition: parseInt(posInfo.children[9].children[1].children[0].data.trim(), 10),
        weeksOnChart: parseInt(posInfo.children[11].children[1].children[0].data.trim(), 10),
      };

      if (artist) {
        chart.songs.push({
          rank,
          title,
          artist,
          cover,
          position,
        });
      } else {
        chart.songs.push({
          rank,
          artist: title,
          cover,
          position,
        });
      }
    }

    if (chart.songs.length > 1) {
      callback(null, chart);
    } else {
      callback('Songs not found.', null);
    }
  });
}

const getChartsFromCategories = async (categoryURLs, cb) => {
  const charts = [];

  const promises = categoryURLs.map((categoryURL) => new Promise(((res) => {
    request(categoryURL, (error, response, html) => {
      if (error) {
        res();
      }
      const $ = cheerio.load(JSON.parse(html).html);

      const chartLinks = $('a.lrv-u-flex.lrv-u-flex-direction-column');
      for (let i = 0; i < chartLinks.length; i += 1) {
        if (chartLinks[i].attribs.href.startsWith('/charts/')) {
          charts.push({ name: chartLinks[i].children[1].children[1].children[0].data.trim(), url: `${BILLBOARD_BASE_URL}${chartLinks[i].attribs.href}` });
        }
      }
      res();
    });
  })));

  Promise.all(promises).then(() => {
    cb(charts);
  });
};

function listCharts(cb) {
  if (typeof cb !== 'function') {
    cb('Specified callback is not a function.', null);
    return;
  }

  request(BILLBOARD_CHARTS_URL, (error, response, html) => {
    if (error) {
      cb(error, null);
      return;
    }

    const $ = cheerio.load(html);

    const categoryElements = $('.o-nav__list-item.lrv-u-color-grey-medium-dark');
    const categoryURLs = [];
    for (let i = 0; i < categoryElements.length; i += 1) {
      if (categoryElements[i].children && categoryElements[i].children[1].attribs.href === '#') {
        const categoryName = encodeURIComponent(categoryElements[i].children[1].attribs.rel);
        categoryURLs.push(`${BILLBOARD_CHART_CATEGORY_URL_PREFIX}${categoryName}${BILLBOARD_CHART_CATEGORY_URL_SUFFIX}`);
      }
    }

    getChartsFromCategories(categoryURLs, (charts) => {
      if (charts.length > 0) {
        cb(null, charts);
      } else {
        cb('No charts found.', null);
      }
    });
  });
}

module.exports = {
  getChart,
  listCharts,
};