#!/usr/bin/env python3
"""
Example showing for tkinter and ttk how to:
  -- 1. Make a menubar with menu's
  -- 2. Put menu items on the menu's.
  -- 3. Establish callback functions for the menu items, that is,
        functions that are called when a menu item is selected.

Authors: <NAME> and his colleagues
         at Rose-Hulman Institute of Technology.
"""

import tkinter
from tkinter import ttk


class Data(object):
    def __init__(self):
        self.number = 0
        self.number_label = None


def main():
    data = Data()

    root = tkinter.Tk()

    main_frame = ttk.Frame(root, padding=50)
    main_frame.grid()

    label_text = 'The number is ' + str(data.number)
    label = ttk.Label(main_frame, text=label_text)
    label.grid()
    data.number_label = label

    # The default is for menus to be "tear-off" -- they can be dragged
    # off the menubar.  Use whichever style best suits your GUI.
    root.option_add('*tearOff', False)

    # Step 1:  Make the menu bar
    menubar = tkinter.Menu(root)
    root['menu'] = menubar

    # Step 2:  Make the pull-down menu's on the menu bar.
    change_menu = tkinter.Menu(menubar)
    menubar.add_cascade(menu=change_menu, label='ChangeIt')

    show_menu = tkinter.Menu(menubar)
    menubar.add_cascade(menu=show_menu, label='ShowIt')

    # Step 3:  Make menu items for each menu on the menu bar.
    # Bind callbacks using lambda, as we have seen elsewhere,
    # but this time with a    command=...   optional argument supplied.
    change_menu.add_command(label='Increase the number',
                            command=lambda: increase_number(data, 1))

    change_menu.add_command(label='Decrease the number',
                            command=lambda: increase_number(data, -1))

    show_menu.add_command(label='Show it in red',
                          command=lambda: show(data, 'red'))

    show_menu.add_command(label='Show it in yellow',
                          command=lambda: show(data, 'yellow'))

    root.mainloop()


def increase_number(data, amount):
    """
    Increases the number in the given Data object by the given amount
    and updates the Label in the given Data object that displays
    the number.
    """
    data.number = data.number + amount
    new_text = 'The number is {}'.format(data.number)
    data.number_label['text'] = new_text


def show(data, color):
    new_text = 'The number is {}'.format(data.number)
    data.number_label['text'] = new_text
    data.number_label['background'] = color


# ----------------------------------------------------------------------
# Calls  main  to start the ball rolling.
# ----------------------------------------------------------------------
main()
