index.js

const express = require('express')
const bodyParser = require('body-parser')
const app = express()
const port = 3000

const admin = require("firebase-admin");
const serviceAccount = require("./url-shortner-338c1-firebase-adminsdk-yfrrz-cc29eab9ce.json");
admin.initializeApp({
    credential: admin.credential.cert(serviceAccount)
});

const staticFolder = express.static("public");

const urlsdb = admin.firestore().collection("urlsdb")
const usersdb = admin.firestore().collection("usersdb")

app.use(staticFolder);
app.use(bodyParser.json());

app.get('/:short_url', (req,res) => {
    const short_url = req.params.short_url;

    const doc = urlsdb.doc(short_url)

    doc.get().then(response=>{
        const data = response.data()
        if (data && data.url){
            res.redirect(301,data.url);
        }else {
            res.redirect(404,"https://github.com/JayantGoel001")
        }
    })
});

app.post('/admin/urls/', (req, res) => {
    const {email,password,short_url,url} = req.body;
    usersdb.doc(email).get().then(response=>{
        const user = response.data();
        if (user && user.email === email && user.password===password){
            const doc = urlsdb.doc(short_url);
            doc.set({url}).then(_ => {
                res.send({statusCode:201,message:"Done"});
            })
        }else {
            res.send({statusCode:403,message:"Not Possible"})
        }
    })
})

app.listen(port, () => {
    console.log(`Example app listening at http://localhost:${port}`)
})