app.js

require('dotenv').config();
const express=require("express");
const bp=require("body-parser");
const ejs=require("ejs");
const mongoose=require("mongoose");
const session=require("express-session");
const passport=require("passport");
const plm=require("passport-local-mongoose");
const GoogleStrategy = require('passport-google-oauth20').Strategy;
const findOrCreate=require("mongoose-findorcreate");


const app=express();

app.use(express.static("public"));
app.set('view engine','ejs');
app.use(bp.urlencoded({extended:true}));

////documentations always help/////

app.use(session({
    secret:"Some secret code here long.",
    resave:false,
    saveUninitialized:false
})); //session initial configuration

app.use(passport.initialize()); //setting up passport.
app.use(passport.session()); //using passport to set up session.

mongoose.connect("mongodb://127.0.0.1:27017/userDB");

const userSchema=new mongoose.Schema({ //to have a plugin it has to be a mongoose schema.
    email:String,
    password:String,
    googleId:String,
    secret:String
});

userSchema.plugin(plm); //plm as a plugin
userSchema.plugin(findOrCreate);

const User=new mongoose.model("User",userSchema);

passport.use(User.createStrategy());

passport.serializeUser(function(user, done) {
    done(null, user);
});
  
passport.deserializeUser(function(user, done) {
    done(null, user);
});

passport.use(new GoogleStrategy({
    clientID: process.env.CLIENT_ID,
    clientSecret: process.env.CLIENT_SECRET,
    callbackURL: "http://localhost:3000/auth/google/secrets",
    userProfileURL:"https://www.googleapis.com/oauth2/v3/userinfo"
  },
  function(accessToken, refreshToken, profile, cb) {
    console.log(profile);
    User.findOrCreate({ googleId: profile.id }, function (err, user) {
      return cb(err, user);
    });
  }
));

app.get("/",function(req,res){
    res.render("home");
});

app.get("/auth/google",
    passport.authenticate("google",{
        scope:["profile", "email"]
    })
);

app.get('/auth/google/secrets', 
  passport.authenticate('google', { failureRedirect: '/login' }),
  function(req, res) {
    // Successful authentication, redirect hto secrets page.
    res.redirect('/secrets');
  });

app.get("/login",function(req,res){
    res.render("login");
});

app.get("/register",function(req,res){
    res.render("register");
});

app.get("/secrets",function(req,res){
    User.find({secret:{$ne:null}}).then(function(found){
        if(found){
            res.render("secrets",{userWithSecrets: found});
        }
    });
});

app.get("/logout",function(req,res){
    req.logout(function(err){
        if(err){
            console.log(err);
        }
    });
    res.redirect("/");
});

app.get("/submit",function(req,res){
    if(req.isAuthenticated()){
        res.render("submit");
    }else{
        res.redirect("/login");
    }
});

app.post("/register",function(req,res){
    User.register({username:req.body.username},req.body.password,function(err,user){
        if(err){
            console.log(err);
            res.redirect("/register");
        } else{
            passport.authenticate("local")(req,res,function(){
                res.redirect("secrets");
            });
        }
    });
});

app.post("/login",function(req,res){
    const user=new User({
        username:req.body.username,
        password:req.body.password
    });

    req.login(user,function(err){
        if(err){
            console.log(err);
        }else{
            passport.authenticate("local")(req,res,function(){
            res.redirect("secrets");
            });
        }
    });
});

app.post("/submit",function(req,res){
    const newSecret=req.body.secret;
    console.log(req.user._id);
    User.findById(req.user._id).then(function(found){
        if(found){
            found.secret=newSecret;
            found.save().then(function(){
                    res.redirect("/secrets");
            });
        }
    });
});

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