/**
* This is an example of a basic node.js script that performs
* the Authorization Code oAuth2 flow to authenticate against
* the Spotify Accounts.
*
* For more information, read
* https://developer.spotify.com/web-api/authorization-guide/#authorization_code_flow
*/

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 client_id = 'CLIENT_ID'; // Your client id
var client_secret = 'CLIENT_SECRET'; // Your secret
var redirect_uri = 'REDIRECT_URI'; // Your redirect uri

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