LoginSystem/main.go

package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"net/http"
	"strconv"

	"github.com/boltdb/bolt"
	"github.com/gorilla/sessions"
)

// Functions implemented: signup, login with username and password, logout, the user cannot login again if he/she is already logged in (except admin)
//                        cannot signup for username already used, check how many users logged in (INDEX.html)
// User for testing: username -> hello, password -> world
// Admin user (hard-coded): admin

var store = sessions.NewCookieStore([]byte("secret-key"))
var db *bolt.DB
var Online_users int = 0

type Status struct {
	NumberLoggedIn int
}

type LogoutCheck struct {
	LoggedOut bool
}

type SignupNewName struct {
	Success bool
}

type LoginCheck struct {
	Success bool
	Repeat  bool
}

func loginHandler(rw http.ResponseWriter, req *http.Request) {
	if req.Method == "GET" {
		username := req.FormValue("username")
		password := req.FormValue("password")
		log.Println("The typed username is:" + username)
		log.Println("The typed password is:" + password)

		var typed LoginCheck
		db.Update(func(tx *bolt.Tx) error {
			users := tx.Bucket([]byte("Users"))
			password_database_byte := users.Get([]byte(username))
			password_database := string(password_database_byte)
			if password_database_byte == nil {
				log.Println("Error: The username is not valid!")
				typed.Success = false
				typed.Repeat = false
			} else {
				if password == password_database {
					log.Println("Password is correct")

					session, err := store.Get(req, username)
					if err != nil {
						http.Error(rw, err.Error(), http.StatusInternalServerError)
						return nil
					}

					if session.Values["auth"] == true && username != "admin" {
						typed.Success = false
						typed.Repeat = true
						log.Println("Alert: " + username + " has already loggged in, please logged in with a different account!")
					} else {
						session.Values["auth"] = true
						err = session.Save(req, rw)
						if err != nil {
							http.Error(rw, err.Error(), http.StatusInternalServerError)
							return nil
						}

						Online_users = Online_users + 1
						typed.Success = true
						typed.Repeat = false
						log.Println("Logged in")
					}

				} else {
					typed.Success = false
					typed.Repeat = false
					log.Println("WRONG password!!")
				}
			}
			send_message, _ := json.Marshal(typed)
			rw.Write(send_message)
			return nil
		})

	}
}

func logoutHandler(rw http.ResponseWriter, req *http.Request) {
	log.Println("Logout button is clicked!")
	username := req.FormValue("username")
	log.Println(username + " wants to log out")
	session, err := store.Get(req, username)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}
	session.Values["auth"] = nil
	err = session.Save(req, rw)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}

	var result LogoutCheck
	result.LoggedOut = true
	send_message, _ := json.Marshal(result)
	rw.Write(send_message)
	log.Println("Pass log-out message to html")

	Online_users = Online_users - 1
	log.Println("Logged out successfully")
}

func checkloginHandler(rw http.ResponseWriter, req *http.Request) {
	log.Println("Check button is clicked")
	log.Println("Logged in users: " + strconv.Itoa(Online_users))

	var status Status
	status.NumberLoggedIn = Online_users
	send_message, _ := json.Marshal(status)
	rw.Write(send_message)
}

func signupHandler(rw http.ResponseWriter, req *http.Request) {
	username := req.FormValue("username")
	password := req.FormValue("password")
	log.Println("Create an account that username is:" + username)
	log.Println("Create an account that password is:" + password)
	db.Update(func(tx *bolt.Tx) error {
		users := tx.Bucket([]byte("Users"))
		exist_user := users.Get([]byte(username))
		if exist_user != nil {
			log.Println("Error: The username has already been used!")
			rw.Write([]byte("fail"))
		} else {
			err := users.Put([]byte(username), []byte(password))
			if err != nil {
				return fmt.Errorf("create user: %s", err)
			}
			rw.Write([]byte("success"))
		}
		return nil
	})

}

func main() {
	portPointer := flag.String("port", "8000", "An integer")
	flag.Parse()
	log.Println("Port Number: " + *portPointer)
	httpFileServer := http.FileServer(http.Dir("./files"))
	http.Handle("/", httpFileServer)

	var err1 error
	db, err1 = bolt.Open("my.db", 0600, nil)
	if err1 != nil {
		log.Fatal(err1)
	} else {
		log.Println("database opened")
	}
	defer db.Close()

	db.Update(func(tx *bolt.Tx) error {
		users, err2 := tx.CreateBucketIfNotExists([]byte("Users"))
		if err2 != nil {
			return fmt.Errorf("create bucket: %s", err2)
		}
		err3 := users.Put([]byte("admin"), []byte("admin"))

		if err3 != nil {
			return fmt.Errorf("create admin: %s", err3)
		}
		return nil
	})

	http.HandleFunc("/login", loginHandler)
	http.HandleFunc("/logout", logoutHandler)
	http.HandleFunc("/checklogin", checkloginHandler)
	http.HandleFunc("/signup", signupHandler)

	log.Printf("Listening http://localhost:%s\n", *portPointer)
	if error := http.ListenAndServe(":"+*portPointer, nil); error != nil {
		log.Printf("Error: %s\n", error)
	}
}