app.js

const express = require("express");
const mongoose = require("mongoose");
const cookieParser = require("cookie-parser");

const app = express();
app.use(express.urlencoded({ extended : true }));
app.use(express.static(__dirname+"/public"));
app.use(cookieParser());
app.set("view engine", "ejs");

const optionsForMongoose = {
    useNewUrlParser: true,
    useUnifiedTopology: true
};
const url = "mongodb://localhost:27017/ADP_Project";
mongoose.connect(url, optionsForMongoose);

const itemSchema = new mongoose.Schema({
    text: String
});
const Item = new mongoose.model("item", itemSchema);

const userSchema = new mongoose.Schema({
    username: {
        type: String,
        required: true
    },
    password: {
        type: String,
        required: true
    },
    itemList: [itemSchema]
});
const User = new mongoose.model("user", userSchema)

app.get("/", function(req, res) {
    var userName = req.cookies.username;
    if(userName) {
        res.render("home", {
            user: userName
        });
    } else {
        res.redirect("/login");
    }
});

app.get("/login", function(req, res) {
    var bad_auth = req.query.msg ? true : false;
    if(bad_auth) {
        res.render("login", {
            error: "Invalid Username or Password"
        });
    } else {
        res.render("login", {
            error: ""
        });
    }
});

app.post("/login", function(req, res) {
    const newUser = new User({
        username: req.body.name,
        password: req.body.password,
        itemList: []
    });
    User.findOne({username: newUser.username}, function(err, user) {
        if(!err) {
            if(user) {
                if(user.password !== newUser.password) {
                    res.redirect("/login?msg=fail");
                } else {
                    res.cookie("username", user.username);
                    res.redirect("/");
                }
            } else {
                res.redirect("/login?msg=fail");
            }
        } else {
            res.redirect("/login?msg=fail");
        }
    });
});

app.get("/register", function(req, res) {
    var bad_auth = req.query.msg ? true : false;
    if(bad_auth) {
        res.render("register", {
            error: "Username already exists, please choose some other username"
        });
    }
    res.render("register", {
        error: ""
    });
});

app.post("/register", function(req, res) {
    const newUser = new User({
        username: req.body.name,
        password: req.body.password,
        itemList: []
    });
    User.findOne({username: newUser.username}, function(error, user) {
        if(!error) {
            if(!user) {
                User.insertMany([newUser], function(err, docs) {
                    if(!err) {
                        console.log(docs);
                        res.cookie("username", newUser.username);
                        res.redirect("/");
                    } else {
                        res.redirect("/register?msg=fail");
                    }
                });
            } else {
                res.redirect("/register?msg=fail");
            }
        }
    });
});

app.listen(3000, function() {
    console.log("Server started at port 3000");
});