change code from template engine to next js - reactjs

Question

How do I convert my app that is made with .pug to next app ? I have an app using .pug engine and I want to convert it into next.
This is the app.js but as I know next is different how do I do it? Because here my files are in views, and in views the files are in pages etc how do I do it? Is there any way or I have to code it all again?
const express = require('express');
const app = express();
const port = process.env.PORT || 3000;
const middleware = require('./middleware')
const path = require('path')
const bodyParser = require("body-parser")
const mongoose = require("./database");
const session = require("express-session");
const http = require('http');
const server = app.listen(port, () => console.log("Server listening on port " + port));
const io = require("socket.io")(server, { pingTimeout: 60000 });
app.set("view engine", "pug");
app.set("views", "views");
app.use(bodyParser.urlencoded({ extended: false }));
app.use(express.static(path.join(__dirname, "public")));
app.use(session({
secret: "#########",
resave: true,
saveUninitialized: false
}))
// Routes
const loginRoute = require('./routes/loginRoutes');
const registerRoute = require('./routes/registerRoutes');
const logoutRoute = require('./routes/logout');
const postRoute = require('./routes/postRoutes');
const profileRoute = require('./routes/profileRoutes');
const uploadRoute = require('./routes/uploadRoutes');
const searchRoute = require('./routes/searchRoutes');
const messagesRoute = require('./routes/messagesRoutes');
const notificationsRoute = require('./routes/notificationRoutes');
// Api routes
const postsApiRoute = require('./routes/api/posts');
const usersApiRoute = require('./routes/api/users');
const chatsApiRoute = require('./routes/api/chats');
const messagesApiRoute = require('./routes/api/messages');
const notificationsApiRoute = require('./routes/api/notifications');
app.use("/login", loginRoute);
app.use("/register", registerRoute);
app.use("/logout", logoutRoute);
app.use("/posts", middleware.requireLogin, postRoute);
app.use("/profile", middleware.requireLogin, profileRoute);
app.use("/uploads", uploadRoute);
app.use("/search", middleware.requireLogin, searchRoute);
app.use("/messages", middleware.requireLogin, messagesRoute);
app.use("/notifications", middleware.requireLogin, notificationsRoute);
app.use("/api/posts", postsApiRoute);
app.use("/api/users", usersApiRoute);
app.use("/api/chats", chatsApiRoute);
app.use("/api/messages", messagesApiRoute);
app.use("/api/notifications", notificationsApiRoute);
app.get("/", middleware.requireLogin, (req, res, next) => {
var payload = {
pageTitle: "Home",
userLoggedIn: req.session.user,
userLoggedInJs: JSON.stringify(req.session.user),
}
res.status(200).render("home", payload);
})
io.on("connection", socket => {
socket.on("setup", userData => {
socket.join(userData._id);
socket.emit("connected");
})
socket.on("join room", room => socket.join(room));
socket.on("typing", room => socket.in(room).emit("typing"));
socket.on("stop typing", room => socket.in(room).emit("stop typing"));
socket.on("notification received", room => socket.in(room).emit("notification received"));
socket.on("new message", newMessage => {
var chat = newMessage.chat;
if(!chat.users) return console.log("Chat.users not defined");
chat.users.forEach(user => {
if(user._id == newMessage.sender._id) return;
socket.in(user._id).emit("message received", newMessage);
})
});
})

Answer 1

If you don't want to refactor all your pug template engine pages to next.js pages, then you can make the pug pages coexist with the next.js. You can make the next.js the default route, and place next.js code after all pug page routes. And you also need to refactor app.get("/", middleware.requireLogin, (req, res, next) => {...} to make sure next.js is the default route.
To apply this rule, you need a custom next.js server.
sample code
const express = require('express');
const next = require('next');
const port = 3000;
const dev = process.env.NODE_ENV !== 'production'; // use default NodeJS environment variable to figure out dev mode
const app = next({dev, conf});
const handle = app.getRequestHandler();
const server = express();
// all your pug page routes should be declared before `server.get('*'`.
server.get('*', authMiddleware(false), (req, res) => {
// pass through everything to NextJS
return handle(req, res);
});
app.prepare().then(() => {
server.listen(port, (err) => {
if (err) throw err;
console.log('NextJS is ready on http://localhost:' + port);
});
}).catch(e => {
console.error(e.stack);
process.exit(1);
});