import tkinter as tk
from tkinter import ttk


class View(tk.Tk):

    PAD = 10
    MAX_BUTTONS_PER_ROW = 4
    BUTTON_CAPTIONS = [
        'C', '+/-', '%', '/',
        7, 8, 9, '*',
        4, 5, 6, '-',
        1, 2, 3, '+',
        0, '.', '='
    ]

    def __init__(self, controller):
        super().__init__()

        self.title('PyCalc')

        self.controller = controller

        self.value_var = tk.StringVar()

        self._make_main_frame()
        self._make_entry()
        self._make_buttons()

    def main(self):
        self.mainloop()

    def _make_main_frame(self):
        self.main_frm = ttk.Frame(self)
        self.main_frm.pack(padx=self.PAD, pady=self.PAD)

    def _make_entry(self):
        ent = ttk.Entry(self.main_frm, justify='right', textvariable=self.value_var, state='readonly')
        ent.pack(fill='x')

    def _make_buttons(self):
        outer_frm = ttk.Frame(self.main_frm)
        outer_frm.pack()

        frm = ttk.Frame(outer_frm)
        frm.pack()

        for buttons_in_row, caption in enumerate(self.BUTTON_CAPTIONS):
            if buttons_in_row % self.MAX_BUTTONS_PER_ROW == 0:
                frm = ttk.Frame(outer_frm)
                frm.pack()

            btn = ttk.Button(
                frm, text=caption, command=(
                    lambda button=caption: self.controller.on_button_click(button)
                )
            )
            btn.pack(side='left')