server.js

var express = require('express');
var mongoose = require('mongoose');
var bijective = require('./bijective.js');
var Urls = require('./models');

mongoose.connect('mongodb://localhost/url-shortener');

var app = express();
app.use(express.static('public'));

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

  var shortUrl = '';

  Urls.findOne({url: req.params.longUrl}, function (err, doc){
    if (doc){
      res.send({'key': bijective.encode(doc._id)});
    } else {

      var newUrl = Urls({
        url: req.params.longUrl
      });

      newUrl.save(function(err) {
        if (err) console.log(err);

        res.send({'key': bijective.encode(newUrl._id)});
      });
    }

  });

});

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

  var id = bijective.decode(req.params.key);

  Urls.findOne({_id: id}, function (err, doc){
    if (doc) {
      res.redirect(doc.url);
    } else {
      res.redirect("/");
    }
  });

});


app.listen(3000, function () {
  console.log('Example app listening on port 3000!')
});