import calendar
import tkinter as tk
import time
from tkinter import ttk


class MyDatePicker(tk.Toplevel):
    """
    Description:
        A tkinter GUI date picker.
    """

    def __init__(self, widget=None, format_str=None):
        """
        :param widget: widget of parent instance.

        :param format_str: print format in which to display date.
        :type format_str: string

        Example::
            a = MyDatePicker(self, widget=self.parent widget,
                             format_str='%02d-%s-%s')
        """

        super().__init__()
        self.widget = widget
        self.str_format = format_str

        self.title("Date Picker")
        self.resizable(0, 0)
        self.geometry("+630+390")

        self.init_frames()
        self.init_needed_vars()
        self.init_month_year_labels()
        self.init_buttons()
        self.space_between_widgets()
        self.fill_days()
        self.make_calendar()

    def init_frames(self):
        self.frame1 = tk.Frame(self)
        self.frame1.pack()

        self.frame_days = tk.Frame(self)
        self.frame_days.pack()

    def init_needed_vars(self):
        self.month_names = tuple(calendar.month_name)
        self.day_names = tuple(calendar.day_abbr)
        self.year = time.strftime("%Y")
        self.month = time.strftime("%B")

    def init_month_year_labels(self):
        self.year_str_var = tk.StringVar()
        self.month_str_var = tk.StringVar()

        self.year_str_var.set(self.year)
        self.year_lbl = tk.Label(self.frame1, textvariable=self.year_str_var,
                                 width=3)
        self.year_lbl.grid(row=0, column=5)

        self.month_str_var.set(self.month)
        self.month_lbl = tk.Label(self.frame1, textvariable=self.month_str_var,
                                  width=8)
        self.month_lbl.grid(row=0, column=1)

    def init_buttons(self):
        self.left_yr = ttk.Button(self.frame1, text="←", width=5,
                                  command=self.prev_year)
        self.left_yr.grid(row=0, column=4)

        self.right_yr = ttk.Button(self.frame1, text="→", width=5,
                                   command=self.next_year)
        self.right_yr.grid(row=0, column=6)

        self.left_mon = ttk.Button(self.frame1, text="←", width=5,
                                   command=self.prev_month)
        self.left_mon.grid(row=0, column=0)

        self.right_mon = ttk.Button(self.frame1, text="→", width=5,
                                    command=self.next_month)
        self.right_mon.grid(row=0, column=2)

    def space_between_widgets(self):
        self.frame1.grid_columnconfigure(3, minsize=40)

    def prev_year(self):
        self.prev_yr = int(self.year_str_var.get()) - 1
        self.year_str_var.set(self.prev_yr)

        self.make_calendar()

    def next_year(self):
        self.next_yr = int(self.year_str_var.get()) + 1
        self.year_str_var.set(self.next_yr)

        self.make_calendar()

    def prev_month(self):
        index_current_month = self.month_names.index(self.month_str_var.get())
        index_prev_month = index_current_month - 1

        #  index 0 is empty string, use index 12 instead,
        # which is index of December.
        if index_prev_month == 0:
            self.month_str_var.set(self.month_names[12])
        else:
            self.month_str_var.set(self.month_names[index_current_month - 1])

        self.make_calendar()

    def next_month(self):
        index_current_month = self.month_names.index(self.month_str_var.get())

        try:
            self.month_str_var.set(self.month_names[index_current_month + 1])
        except IndexError:
            #  index 13 does not exist, use index 1 instead, which is January.
            self.month_str_var.set(self.month_names[1])

        self.make_calendar()

    def fill_days(self):
        col = 0
        #  Creates days label
        for day in self.day_names:
            self.lbl_day = tk.Label(self.frame_days, text=day)
            self.lbl_day.grid(row=0, column=col)
            col += 1

    def make_calendar(self):
        #  Delete date buttons if already present.
        #  Each button must have its own instance attribute for this to work.
        try:
            for dates in self.m_cal:
                for date in dates:
                    if date == 0:
                        continue

                    self.delete_buttons(date)

        except AttributeError:
            pass

        year = int(self.year_str_var.get())
        month = self.month_names.index(self.month_str_var.get())
        self.m_cal = calendar.monthcalendar(year, month)

        #  build dates buttons.
        for dates in self.m_cal:
            row = self.m_cal.index(dates) + 1
            for date in dates:
                col = dates.index(date)

                if date == 0:
                    continue

                self.make_button(str(date), str(row), str(col))

    def make_button(self, date, row, column):
        """
        Description:
            Build a date button.

        :param date: date.
        :type date: string

        :param row: row number.
        :type row: string

        :param column: column number.
        :type column: string
        """
        exec(
            "self.btn_" + date + " = ttk.Button(self.frame_days, text=" + date
            + ", width=5)n"
            "self.btn_" + date + ".grid(row=" + row + " , column=" + column
            + ")n"
            "self.btn_" + date + ".bind("<Button-1>", self.get_date)"
        )

    def delete_buttons(self, date):
        """
        Description:
            Delete a date button.

        :param date: date.
        :type: string
        """
        exec(
            "self.btn_" + str(date) + ".destroy()"
        )

    def get_date(self, clicked=None):
        """
        Description:
            Get the date from the calendar on button click.

        :param clicked: button clicked event.
        :type clicked: tkinter event
        """

        clicked_button = clicked.widget
        year = self.year_str_var.get()
        month = self.month_str_var.get()
        date = clicked_button['text']

        self.full_date = self.str_format % (date, month, year)
        print(self.full_date)
        #  Replace with parent 'widget' of your choice.
        try:
            self.widget.delete(0, tk.END)
            self.widget.insert(0, self.full_date)
        except AttributeError:
            pass


if __name__ == '__main__':
    def application():
        MyDatePicker(format_str='%02d-%s-%s')

    root = tk.Tk()
    btn = tk.Button(root, text="test", command=application)
    btn.pack()
    root.mainloop()