# =========================================================
# File: gui_menu.py
# 2015-04-27 by A. Ortiz, ITESM CEM.
#
# This program demonstrates how to write a Tkinter
# GUI-based application with a menu that contains several
# options for the user. Requires Python 3.
# =========================================================

from tkinter import *
from tkinter.messagebox import *

#----------------------------------------------------------
def average(x):
    """Calculate the arithmetic mean of the list of numbers
       contained in a.
    """
    return sum(x) / len(x)

#----------------------------------------------------------
def fact(n):
    """Calculate the factorial of n.
       n! = (1)(2)(3)...(n - 1)(n)
    """
    r = 1
    for i in range(1, n + 1):
        r *= i
    return r

#----------------------------------------------------------
def main():
    """Main program. Controls all the GUI elements.
    """

    #------------------------------------------------------
    def about():
        showinfo('About',
                 'GUI Example Application 1.0\n'
                 '© 2015 by Ariel Ortiz')

    #------------------------------------------------------
    def confirm_quit():
        response = askyesno('Quit',
                     'Are you sure you want to quit?')
        if response:
            root.destroy()

    #------------------------------------------------------
    def dialog_average():

        #--------------------------------------------------
        def calc_average():
            data_string = data.get('1.0', END).strip()
            data_list = data_string.split()
            if len(data_list) == 0:
                showerror('You made a boo-boo!',
                          'Please specify at least one number.')
                return
            nums = []
            for e in data_list:
                if not e.isdigit():
                    showerror('You made a boo-boo!',
                              'Please input only digits.')
                    return
                else:
                    nums.append(int(e))
            dialog.destroy()
            r = average(nums)
            showinfo('Result',
                     'The average is {0:.2f}'.format(r))
        #--------------------------------------------------

        dialog = Toplevel(root)
        dialog.transient(root)
        dialog.grab_set()
        dialog.title('Average')

        text = Label(dialog,
                     text='Input numbers:\n'
                          '(use spaces or <Enter>\n'
                          'to separate values)')
        text.grid(row=0, column=0, padx=10, pady=10)

        data = Text(dialog, height=5, width=10)
        data.grid(row=0, column=1, padx=10, pady=10)

        cont = Button(dialog, text='Continue',
                      command=calc_average)
        cont.grid(row=1, column=1, padx=10, pady=10)

    #------------------------------------------------------
    def dialog_factorial():

        #--------------------------------------------------
        def calc_factorial():
            data_string = data.get('1.0', END).strip()
            if not data_string.isdigit():
                showerror('You made a boo-boo!',
                          'Please input only digits.')
                return
            n = int(data_string)
            dialog.destroy()
            r = fact(n)
            showinfo('Result',
                     'The factorial of {0} is {1}'.format(n, r))

        #--------------------------------------------------
        def enter_calc_factorial(event):
            calc_factorial()
        #--------------------------------------------------

        dialog = Toplevel(root)
        dialog.transient(root)
        dialog.grab_set()
        dialog.title('Factorial')

        text = Label(dialog, text='Input number:')
        text.grid(row=0, column=0, padx=10, pady=10)

        data = Text(dialog, height=1, width=10)
        data.grid(row=0, column=1, padx=10, pady=10)
        data.bind('<Return>', enter_calc_factorial)

        cont = Button(dialog, text='Continue',
                      command=calc_factorial)
        cont.grid(row=1, column=1, padx=10, pady=10)

    #------------------------------------------------------
    root = Tk()
    root.minsize(width=300, height=200)
    root.title('Example')

    app_menu = Menu(root)
    root.config(menu=app_menu)

    compute_menu = Menu(app_menu)
    app_menu.add_cascade(label='Compute',
                         menu=compute_menu)
    compute_menu.add_command(label='Average...',
                             command=dialog_average)
    compute_menu.add_command(label='Factorial...',
                             command=dialog_factorial)
    compute_menu.add_separator()
    compute_menu.add_command(label='Quit',
                             command=confirm_quit)

    help_menu = Menu(app_menu)
    app_menu.add_cascade(label='Help', menu=help_menu)
    help_menu.add_command(label='About...',
                          command=about)

    root.mainloop()

main()