#!/usr/bin/python3

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

from board import Board


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

    strings = [(
        ".2..785..\n"
        "4...52...\n"
        "..1..3.2.\n"
        ".....1...\n"
        "7348.526.\n"
        "2.9.67..5\n"
        ".687..3.9\n"
        "342.1.7..\n"
        "19..86..2\n"
    ), (
        "..1..6435\n"
        ".....1...\n"
        ".5.47.98.\n"
        "..2.8.7.9\n"
        "..87..612\n"
        ".64.1..5.\n"
        "91.3428.7\n"
        ".27....9.\n"
        "6.3.9.5..\n"
    ), (
        ".....6...\n"
        "..2.35.8.\n"
        "....2..13\n"
        ".2....19.\n"
        "93....7..\n"
        "5....4...\n"
        "1......7.\n"
        ".7...142.\n"
        ".9.4.3...\n"
    ), (
        "...82....\n"
        "...6.9..1\n"
        "9.4..1...\n"
        ".9.7..28.\n"
        ".......57\n"
        "7.5......\n"
        ".78962..5\n"
        ".2..8.7.3\n"
        ".6..74.2.\n"
    ), (
        "4......1.\n"
        ".15.4.6..\n"
        ".....7...\n"
        "...21...8\n"
        "...734..2\n"
        ".3..8....\n"
        "8.19...45\n"
        ".4....7..\n"
        "2....3...\n"
    ), (
        "3........\n"
        ".6...791.\n"
        ".....325.\n"
        ".19.645..\n"
        ".......6.\n"
        ".85......\n"
        "...8.....\n"
        "..1..97..\n"
        "47..5....\n"
    )]

    for string in strings[2:-3]:
        iterations = 0
        while '.' in string:
            iterations += 1
            new_string = iterate_board(string)
            assert new_string != string
            string = new_string
        print(f"Solved in {iterations} iterations.")


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

    Return an updated string.
    """

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

    return board.get_new_board()


if __name__ == '__main__':
    main()