import tkinter as tk
from tkinter import messagebox
import sqlite3

# Database setup
def setup_database():
    conn = sqlite3.connect('users.db')
    cursor = conn.cursor()
    cursor.execute('''
        CREATE TABLE IF NOT EXISTS users (
            username TEXT PRIMARY KEY,
            password TEXT
        )
    ''')
    conn.commit()
    conn.close()

# Register user function
def register_user():
    username = username_entry.get()
    password = password_entry.get()

    if not username or not password:
        messagebox.showerror("Error", "All fields are required!")
        return

    conn = sqlite3.connect('users.db')
    cursor = conn.cursor()

    try:
        cursor.execute("INSERT INTO users (username, password) VALUES (?, ?)", (username, password))
        conn.commit()
        messagebox.showinfo("Success", "Registration successful!")
    except sqlite3.IntegrityError:
        messagebox.showerror("Error", "Username already exists!")
    finally:
        conn.close()

# Login user function
def login_user():
    username = username_entry.get()
    password = password_entry.get()

    conn = sqlite3.connect('users.db')
    cursor = conn.cursor()
    cursor.execute("SELECT * FROM users WHERE username = ? AND password = ?", (username, password))
    user = cursor.fetchone()

    if user:
        messagebox.showinfo("Success", f"Welcome {username}!")
    else:
        messagebox.showerror("Error", "Invalid username or password.")
    
    conn.close()

# UI setup
def setup_ui():
    global username_entry, password_entry

    root = tk.Tk()
    root.title("Login System")

    tk.Label(root, text="Username:").grid(row=0, column=0, padx=10, pady=10)
    username_entry = tk.Entry(root)
    username_entry.grid(row=0, column=1, padx=10, pady=10)

    tk.Label(root, text="Password:").grid(row=1, column=0, padx=10, pady=10)
    password_entry = tk.Entry(root, show='*')
    password_entry.grid(row=1, column=1, padx=10, pady=10)

    register_button = tk.Button(root, text="Register", command=register_user)
    register_button.grid(row=2, column=0, padx=10, pady=10)

    login_button = tk.Button(root, text="Login", command=login_user)
    login_button.grid(row=2, column=1, padx=10, pady=10)

    root.mainloop()

if __name__ == "__main__":
    setup_database()
    setup_ui()