import tkinter as tk
from tkinter import messagebox

class TodoApp:
    def __init__(self, root):
        self.root = root
        self.root.title("To-Do List App")
        
        self.tasks = []

        self.task_entry = tk.Entry(root, width=40)
        self.task_entry.grid(row=0, column=0, padx=10, pady=10)

        add_button = tk.Button(root, text="Add Task", command=self.add_task)
        add_button.grid(row=0, column=1, padx=5, pady=10)

        remove_button = tk.Button(root, text="Remove Task", command=self.remove_task)
        remove_button.grid(row=0, column=2, padx=5, pady=10)

        self.task_listbox = tk.Listbox(root, width=50)
        self.task_listbox.grid(row=1, column=0, columnspan=3, padx=10, pady=10)

        self.load_tasks()

    def add_task(self):
        task = self.task_entry.get()
        if task:
            self.tasks.append(task)
            self.update_task_listbox()
            self.task_entry.delete(0, tk.END)
            self.save_tasks()

    def remove_task(self):
        try:
            selected_index = self.task_listbox.curselection()[0]
            del self.tasks[selected_index]
            self.update_task_listbox()
            self.save_tasks()
        except IndexError:
            messagebox.showwarning("Warning", "No task selected.")

    def update_task_listbox(self):
        self.task_listbox.delete(0, tk.END)
        for task in self.tasks:
            self.task_listbox.insert(tk.END, task)

    def save_tasks(self):
        with open("tasks.txt", "w") as f:
            for task in self.tasks:
                f.write(task + "\n")

    def load_tasks(self):
        try:
            with open("tasks.txt", "r") as f:
                self.tasks = [line.strip() for line in f.readlines()]
                self.update_task_listbox()
        except FileNotFoundError:
            pass

if __name__ == "__main__":
    root = tk.Tk()
    app = TodoApp(root)
    root.mainloop()