arbeitszeitmessung/Backend/main.go

package main

import (
	"arbeitszeitmessung/models"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net/http"
	"os"
	"strconv"

	_ "github.com/lib/pq"
)

func main() {
	var err error
	models.DB, err = OpenDatabase()
	if err != nil {
		log.Fatal(err)
	}
	defer models.DB.Close()

	// handles the different http routes
	http.HandleFunc("/time/new", timeCreateHandler)
	http.HandleFunc("/time", timeHandler)
	http.HandleFunc("/logout", logoutHandler)

	// starting the http server
	fmt.Printf("Server is running at http://localhost:8000 exposed to port %s\n", getEnv("EXPOSED_PORT", "8000"))
	log.Fatal(http.ListenAndServe(":8080", nil))
}

// Relevant for arduino inputs -> creates new Booking from get and put method
// GET only for demo purpose
func timeCreateHandler(w http.ResponseWriter, r *http.Request) {
	setCors(w)
	// switch with request methods
	switch r.Method {
	case "PUT":
		createBooking(w, r)
	case "GET":
		createBooking(w, r)
	case "OPTIONS":
		// just support options header for non GET Requests from SWAGGER
		w.WriteHeader(http.StatusOK)
	default:
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
	}
}

// Frontendrelevant backend functionality -> not used by the arduino devices
func timeHandler(w http.ResponseWriter, r *http.Request) {
	setCors(w)
	switch r.Method {
	case "GET":
		getBookings(w, r)
	case "PUT":
		updateBooking(w, r)
	case "OPTIONS":
		// just support options header for non GET Requests from SWAGGER
		w.WriteHeader(http.StatusOK)
	default:
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
	}
}

func logoutHandler(w http.ResponseWriter, r *http.Request) {
	setCors(w)
	switch r.Method {
	case "GET":
		autoLogout(w, r)
	default:
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
	}
}

func autoLogout(w http.ResponseWriter, r *http.Request) {
	users, err := (*models.User).GetAll(nil)
	var logged_out_users []models.User
	if err != nil {
		fmt.Printf("Error getting user list %v\n", err)
	}
	for _, user := range users {
		if user.CheckAnwesenheit() {
			err = user.Logout()
			if err != nil {
				fmt.Printf("Error logging out user %v\n", err)
			}
			logged_out_users = append(logged_out_users, user)
		}

	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(logged_out_users)

}

// Creates a booking from the http query params -> no body needed
// after that entry wi'll be written to database and the booking is returned as json
func createBooking(w http.ResponseWriter, r *http.Request) {

	booking := (*models.Booking).FromUrlParams(nil, r.URL.Query())
	if booking.Verify() {
		err := booking.Insert()
		if errors.Is(models.SameBookingError{}, err) {
			http.Error(w, "Booking already exists", http.StatusConflict)
			return
		}
		if err != nil {
			log.Println("Error inserting booking: ", err)
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusAccepted)
		json.NewEncoder(w).Encode(booking)
	}
	w.WriteHeader(http.StatusBadRequest)
}

// Returns bookings from DB with similar card uid -> checks for card uid in http query params
func getBookings(w http.ResponseWriter, r *http.Request) {
	card_uid := r.URL.Query().Get("card_uid")
	if card_uid == "" {
		http.Error(w, "Missing cardID query parameter", http.StatusBadRequest)
		return
	}
	bookings, err := (*models.Booking).GetBookingsByCardID(nil, card_uid)
	if err != nil {
		log.Println("Error getting bookings: ", err)
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(bookings)
}

// Updates a booking form the given json body
func updateBooking(w http.ResponseWriter, r *http.Request) {
	_booking_id := r.URL.Query().Get("counter_id")
	if _booking_id == "" {
		http.Error(w, "Missing bookingID query parameter", http.StatusBadRequest)
		return
	}
	booking_id, err := strconv.Atoi(_booking_id)
	if err != nil {
		http.Error(w, "Invalid bookingID query parameter", http.StatusBadRequest)
		return
	}
	_booking, err := (*models.Booking).GetBookingById(nil, booking_id)
	if err != nil {
		log.Println("Error getting booking: ", err)
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}
	var booking models.Booking
	dec := json.NewDecoder(r.Body)
	dec.DisallowUnknownFields()
	err = dec.Decode(&booking)
	if err != nil {
		log.Println("Error parsing booking: ", err)
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}
	if booking.CounterId != 0 && booking.CounterId != _booking.CounterId {
		log.Println("Booking Ids do not match")
		http.Error(w, "Booking Ids do not match", http.StatusBadRequest)
		return
	}
	_booking.Update(booking)
	_booking.Save()
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(_booking)
}

// Returns env with default fallback value.
//
// Params:
//
//	key - enviroment var name
//	fallback - default value
func getEnv(key, fallback string) string {
	if value, ok := os.LookupEnv(key); ok {
		return value
	}
	return fallback
}

// setting cors, important for later frontend use
// in DEBUG == "true" everything is set to "*" so that no cors errors will be happen
func setCors(w http.ResponseWriter) {
	if os.Getenv("DEBUG") == "true" {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "*")
		w.Header().Set("Access-Control-Allow-Headers", "*")
	}
}