app.js

var express = require('express'); // Express web server framework
var request = require('request'); // "Request" library
var cors = require('cors');
var querystring = require('querystring');
var cookieParser = require('cookie-parser');
var access_token_genius = '' // Your genius access token
var client_id = ''; // Your client id
var client_secret = ''; // Your secret
var redirect_uri = ''; // Your redirect uri
const phin = require('phin')


const Genius = require('genius-lyrics-scrape');
const { resolve } = require('path');
const token = access_token_genius
 
const client = new Genius.Client(token)
/**
 * Generates a random string containing numbers and letters
 * @param  {number} length The length of the string
 * @return {string} The generated string
 */
var generateRandomString = function(length) {
  var text = '';
  var possible = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';

  for (var i = 0; i < length; i++) {
    text += possible.charAt(Math.floor(Math.random() * possible.length));
  }
  return text;
};

var stateKey = 'spotify_auth_state';

var app = express();

app.use(express.static(__dirname + '/public'))
   .use(cors())
   .use(cookieParser());

app.get('/login', function(req, res) {

  var state = generateRandomString(16);
  res.cookie(stateKey, state);

  // your application requests authorization
  var scope = 'user-read-private user-read-email user-read-currently-playing';
  res.redirect('https://accounts.spotify.com/authorize?' +
    querystring.stringify({
      response_type: 'code',
      client_id: client_id,
      scope: scope,
      redirect_uri: redirect_uri,
      state: state
    }));
});

app.get('/callback', function(req, res) {

  // your application requests refresh and access tokens
  // after checking the state parameter

  var code = req.query.code || null;
  var state = req.query.state || null;
  var storedState = req.cookies ? req.cookies[stateKey] : null;
  if (state === null || state !== storedState) {
    res.redirect('/#' +
      querystring.stringify({
        error: 'state_mismatch'
      }));
  } else {
    res.clearCookie(stateKey);
    var authOptions = {
      url: 'https://accounts.spotify.com/api/token',
      form: {
        code: code,
        redirect_uri: redirect_uri,
        grant_type: 'authorization_code'
      },
      headers: {
        'Authorization': 'Basic ' + (new Buffer(client_id + ':' + client_secret).toString('base64'))
      },
      json: true
    };

    request.post(authOptions, function(error, response, body) {
      if (!error && response.statusCode === 200) {

        var access_token = body.access_token,
            refresh_token = body.refresh_token;

        var options = {
          url: 'https://api.spotify.com/v1/me',
          headers: { 'Authorization': 'Bearer ' + access_token },
          json: true
        };

        // use the access token to access the Spotify Web API
        request.get(options, function(error, response, body) {
          console.log(body);
        });

        // we can also pass the token to the browser to make requests from there
        res.redirect('/#' +
          querystring.stringify({
            access_token: access_token,
            refresh_token: refresh_token
          }));
      } else {
        res.redirect('/#' +
          querystring.stringify({
            error: 'invalid_token'
          }));
      }
    });
  }
});

app.get('/refresh_token', function(req, res) {

  // requesting access token from refresh token
  var refresh_token = req.query.refresh_token;
  var authOptions = {
    url: 'https://accounts.spotify.com/api/token',
    headers: { 'Authorization': 'Basic ' + (new Buffer(client_id + ':' + client_secret).toString('base64')) },
    form: {
      grant_type: 'refresh_token',
      refresh_token: refresh_token
    },
    json: true
  };
  
  request.post(authOptions, function(error, response, body) {
    if (!error && response.statusCode === 200) {
      var access_token = body.access_token;
      res.send({
        'access_token': access_token
      });
    }
  });
});

function findLink(accessToken, name, artist) {
  return new Promise((resolve, reject) => {
    phin({
      url: `https://api.genius.com/search?q=` + name + artist,
      headers: { Authorization: 'Bearer ' + access_token_genius},
      parse: 'json'
    }).then(res => {
      var link = res.body.response.hits[0].result.url
      var cInd = name.indexOf("Ft.")
      if(cInd != -1) {
        name = name.substring(0, cInd) + name.substring(cInd, cInd+1) + "ea" + name.substring(cInd+1)
      }
      var dInd = name.indexOf("&amp")
      if(dInd != -1) {
        name = name.substring(0, dInd+1) + name.substring(dInd+5)
      }
      for(var j=0; j<res.body.response.hits.length; j++) {
        var curr = res.body.response.hits[j].result.title_with_featured.toString()

        ind = curr.indexOf("Ft.")
        if(ind != -1) {
          curr = curr.substring(0, ind) + curr.substring(ind, ind+1) + "ea" + curr.substring(ind+1)
        }
        curr = curr.toLowerCase()
        name = name.toLowerCase()
        same = true
        for(var i=0; i < name.length; i++) {
          if(name.charAt(i) == "(" || curr.charAt(i) == "(") break;
          if(name.charAt(i) == " " || curr.charAt(i) == " ") continue;
          if(name.charAt(i) != curr.charAt(i)) {
            same = false
            break;
          }
        }
        if(same) {
          link = res.body.response.hits[j].result.url
          break;
        }
      }
      client.scrapeLyrics(link)
      .then(scraped => {
        lyrics = scraped
        resolve(lyrics)
      })
      .catch(err => console.err(err))
    }).catch(err => resolve("Couldn't find song"))
  })
}

app.get('/findLyrics', function(req, res) {
  var name = req.query.name
  var artist = req.query.artist
  var lyrics = ""
  findLink(access_token_genius, name, artist).then((lyricsM) => (
    lyrics = lyricsM,
    res.send({
      'lyrics': lyrics
    })
  ))
});

console.log('Listening on 8888');
app.listen(8888);