a todo app written in go with menu, list, add and remove features

todo-app.go

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"strings"
	"time"
)

const (
	todoFile = "todo.txt"
)

func StoreTodo(todo string) {
	todoFile, err := os.OpenFile(todoFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		panic(err)
	}
	defer todoFile.Close()

	todoFile.WriteString(todo + " | " + time.Now().Format("2006-01-02 15:04:05") + "\n")
}

func addTodo() {
	fmt.Printf("\nEnter your todo: ")
	reader := bufio.NewReader(os.Stdin)
	todo, _ := reader.ReadString('\n')
	todo = strings.TrimSpace(todo)
	StoreTodo(todo)
	fmt.Printf("Todo added: %s\n", todo)

	fmt.Printf("\n back to main menu (enter)")
	fmt.Scanln()
}

func listTodo() {
	var i int
	todoFile, err := os.Open(todoFile)
	if err != nil {
		panic(err)
	}
	defer todoFile.Close()

	fmt.Printf("\nLIST OF TODOS: \n")

	scannedTodos := bufio.NewScanner(todoFile)
	for scannedTodos.Scan() {
		fmt.Println(i+1, ">", scannedTodos.Text())
		i++
	}

	if err := scannedTodos.Err(); err != nil {
		panic(err)
	}

	fmt.Printf("\n%d Todo(s) saved \n", i)
}

func list() {
	listTodo()
	fmt.Printf("\n back to main menu (enter)")
	fmt.Scanln()
}

func removeTodo() {
	var i int
	i = getUserChoice("Enter the number of the todo you want to remove: ")

	TODOFile, err := os.OpenFile(todoFile, os.O_RDWR, 0644)
	if err != nil {
		panic(err)
	}
	defer TODOFile.Close()

	todos, err := io.ReadAll(TODOFile)
	if err != nil {
		panic(err)
	}

	lines := strings.Split(string(todos), "\n")
	if i < 1 || i > len(lines) {
		fmt.Println("Invalid todo number")
		return
	}

	lines = append(lines[:i-1], lines[i:]...)

	err = TODOFile.Truncate(0)
	if err != nil {
		panic(err)
	}

	_, err = TODOFile.Seek(0, 0)
	if err != nil {
		panic(err)
	}

	_, err = TODOFile.WriteString(strings.Join(lines, "\n"))
	if err != nil {
		panic(err)
	}

	fmt.Printf("Todo removed\n")
}

func remove() {
	listTodo()
	removeTodo()
	fmt.Printf("\n back to main menu (enter)")
	fmt.Scanln()
}

func getUserChoice(prompt string) int {
	var choice int
	for {
		fmt.Print(prompt)
		_, err := fmt.Scanln(&choice)
		if err == nil {
			break // Input is valid, exit the loop
		}
		fmt.Println("Invalid input. Please enter a valid number.")
	}
	return choice
}

func main() {
	for {
		fmt.Println("\nWhat do you want to do? ")
		fmt.Println("1. Add a todo")
		fmt.Println("2. List all todos")
		fmt.Println("3. Remove a todo")
		fmt.Println("4. Exit")

		action := getUserChoice("Enter your choice: ")

		switch action {
		case 1:
			addTodo()
		case 2:
			list()
		case 3:
			remove()
		case 4:
			fmt.Println("Goodbye!")
			return // Exit the program gracefully
		default:
			fmt.Printf("Invalid action: %v\n", action)
		}
	}
}