nurl/app.js

const express = require('express');
const app = express();
const path = require('path');
const bodyParser = require('body-parser');
const mongoose = require('mongoose');
const config = require('./config');
const base58 = require('./base58.js');
const log4js = require('log4js');
const logger = log4js.getLogger();
logger.level = 'debug';

// grab the url model
const Url = require('./models/url');

mongoose.connect('mongodb://' + config.db.host + '/' + config.db.name);

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

app.use(express.static(path.join(__dirname, 'public')));

app.all('/*', function(req, res, next) {
  // CORS headers
  res.header("Access-Control-Allow-Origin", "*"); // restrict it to the required domain
  res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS');
  // Set custom headers for CORS
  res.header('Access-Control-Allow-Headers', 'Content-type,Accept,X-Access-Token,X-Key');
  if (req.method == 'OPTIONS') {
    res.status(200).end();
  } else {
    next();
  }
});

app.get('/', function(req, res){
  res.sendFile(path.join(__dirname, 'views/index.html'));
});

app.post('/api/v1/shorten', function(req, res){
    const longUrl = req.body.url;
    let shortUrl = '';

    // check if url already exists in database
  Url.findOne({long_url: longUrl}, function (err, doc){

    if (doc){
      shortUrl = config.webhost + base58.encode(doc._id);

      // the document exists, so we return it without creating a new entry
      res.send({'shortUrl': shortUrl});
    } else {
      // since it doesn't exist, let's go ahead and create it:
        const newUrl = Url({
            long_url: longUrl
        });

        // save the new link
      newUrl.save(function(err) {
        if (err){
            logger.error(err);
        }

        shortUrl = config.webhost + base58.encode(newUrl._id);

        res.send({'shortUrl': shortUrl});
      });
    }

  });

});

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

    const base58Id = req.params.encoded_id;

    const id = base58.decode(base58Id);

    // check if url already exists in database
    Url.findOneAndUpdate({_id: id}, {$inc:{visits:1}}, function (err, doc){
    if (doc) {
        logger.debug('doc', doc);
      res.redirect(doc.long_url);
    } else {
      res.redirect(config.webhost);
    }
  });

});

const server = app.listen(3000, function () {
    logger.info('Server listening on port 3000');
});