import tkinter as tk
from tkinter import messagebox

def calculate():
    try:
        price = float(entry_price.get())
        #quantity = int(entry_quantity.get())
        rate = float(entry_rate.get())

        if price < 0 or rate < 0: #price < 0 or quantity < 0 or rate < 0:
            messagebox.showerror("Error", "Invalid input.", detail="Value cannot be negative.")
            return

        if rate > 100:
            messagebox.showerror("Error", "Invalid input.", detail="Discount rate cannot exceed 100%.")
            return

        #subtotal = price * quantity
        discount = price * rate / 100 #subtotal * rate / 100
        total = price - discount #subtotal - discount

        result_var.set(f"Total: {total:,.2f}")

    except ValueError:
        messagebox.showerror("Error", "Invalid input.", detail="Please enter numeric values. Fractions are allowed for price and discount rate.")


root = tk.Tk()
root.title("Discount Calculator")
root.geometry("280x250")
tk.Label(root, text="Price").pack(pady=5)
entry_price = tk.Entry(root, width=20)
entry_price.pack(pady=5)

# tk.Label(root, text="Quantity").pack(pady=5)
# entry_quantity = tk.Entry(root, width=20)
# entry_quantity.pack(pady=5)
tk.Label(root, text="Discount (%)").pack(pady=5)
entry_rate = tk.Entry(root, width=20)
entry_rate.pack(pady=5)

tk.Button(root, text="Calculate", command=calculate).pack(pady=10)

result_var = tk.StringVar()
tk.Label(root, textvariable=result_var).pack(pady=10)

root.mainloop()