from tkinter import *
from tkinter import messagebox
from calendar import isleap

def is_valid(input):
    if input.isdigit():
        try:
            if len(input) > 1:
                if input[0] == "0":
                    return False
            if int(input) < 10000:
                return True
            else:
                return False
        except:
            return False
    elif input == "":
        return True
    else:
        return False

def get_leap_years():
    from_year = from_entry.get();
    to_year = to_entry.get();
    try:
        from_year = int(from_year)
    except:
        messagebox.showerror('Virhe', '"Vuodesta"-kentän arvo ei kelpaa')
        return
    try:
        to_year = int(to_year)
    except:
        messagebox.showerror('Virhe', '"Vuoteen"-kentän arvo ei kelpaa')
        return
    if from_year > to_year:
        messagebox.showerror('Virhe', '"Vuodesta"-kentän arvon pitää olla pienempi tai yhtä suuri kuin "Vuoteen"-kentä arvo')
        return
    leap_years = []
    for year in range(from_year, to_year+1):
        if isleap(year): leap_years.append(year)
    leap_years_text_box.config(state='normal')
    leap_years_text_box.delete('1.0', 'end');
    leap_years_text_box.insert('end', leap_years);
    leap_years_text_box.config(state='disabled')

window = Tk()
window.title('Karkausvuodet')
window.geometry('320x240')

validate_entry = window.register(is_valid)

years_frame = Frame(window)

from_frame = LabelFrame(years_frame, text="Vuodesta")
from_entry = Entry(from_frame, justify="center", width=6, validate="key", validatecommand=(validate_entry, '%P'))
from_entry.insert(0,'1901')
from_entry.pack(fill="x", expand="yes", padx=3, pady=3)
from_frame.pack(side=LEFT, ipadx=2, padx=5, pady=3)

to_frame = LabelFrame(years_frame, text="Vuoteen")
to_entry = Entry(to_frame, justify="center", width=6, validate="key", validatecommand=(validate_entry, '%P'))
to_entry.insert(0,'2000')
to_entry.pack(fill="x", expand="yes", padx=3, pady=3)
to_frame.pack(side=RIGHT, ipadx=2, padx=5, pady=3)

years_frame.pack(padx=5, pady=6)

get_leap_years_button = Button(window, bg="powderblue", text="Hae karkausvuodet", command=get_leap_years)
get_leap_years_button.pack(fill="both", padx=5, pady=6)

leap_years_frame = LabelFrame(window, text="Karkausvuodet ajanjaksolla")

leap_years_scrollbar = Scrollbar(leap_years_frame, orient='vertical')
leap_years_scrollbar.pack(side=RIGHT, fill="y", expand="yes", padx=0, pady=3)

leap_years_text_box = Text(leap_years_frame, state='normal', wrap=WORD)
leap_years_text_box.pack(side=LEFT, fill="both", expand="yes", padx=3, pady=3)

leap_years_scrollbar.config(command=leap_years_text_box.yview);
leap_years_text_box.config(state='disabled', yscrollcommand=leap_years_scrollbar.set)

leap_years_frame.pack(fill="both", expand="yes", padx=5, pady=6)

get_leap_years()

window.mainloop()