#!/usr/bin/python3

"""This is a Sudoku Solver."""

from board import Board


def main():
    """Provided a string representing a Sudoku game, solve it."""

    string = (
        "..4...618\n"
        "9...8....\n"
        ".2...6.4.\n"
        "...5.34.6\n"
        "7.3.1.2.5\n"
        "6.94.7...\n"
        ".6.2...8.\n"
        "....4...3\n"
        "418...7..\n"
    )

    while '.' in string:
        new_string = iterate_board(string)
        assert new_string != string
        string = new_string


def iterate_board(string):
    """This function consists of one iteration through the solving process.

    Return an updated string.
    """

    board = Board(string)
    board.compute_possible_values()
    board.intersect_lines_and_columns()
    board.create_squares()
    board.discard_with_grids()
    print(f"New board:\n{board}")

    return board.get_new_board()


if __name__ == '__main__':
    main()