#!/usr/bin/python3

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

import argparse
from board import Board


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

    parser = argparse.ArgumentParser()
    parser.add_argument('file', help='file containing the Sudoku to solve')
    args = parser.parse_args()
    sudoku_file = args.file

    strings = find_strings_in(sudoku_file)

    # default string if file wasn't computed
    if len(strings) == 0:
        strings = [(
            ".....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"
        )]

    for string in strings:
        solve_board(string, debug=False)


def find_strings_in(sudoku_file: str) -> list:
    """Extract the Sudoku string from a file.
    
    Return a list of the Sudoku strings.
    """

    strings: list = []

    try:
        with open(sudoku_file, 'r') as sudokus:
            string = ""
            for line in sudokus.readlines():
                if len(line) == 10:
                    string += line
                elif len(line) == 1:
                    strings.append(string)
                    string = ""
                else:
                    raise AssertionError("Invalid file")

    except FileNotFoundError:
        print("File not found, using default string.")

    return strings


def solve_board(string: str, debug=False):
    """This function loops over the iteration process."""

    board = Board(string, debug=debug)
    print(board)
    input("Hit ENTER to solve")
    iterations = 0
    while '.' in string:
        iterations += 1
        print(board)
        board.compute_possible_values()
        board.compute_obligated_values()
        string = board.update_string()
        board.update_board()
        print(board)

    print(f"Solved in {iterations} iterations.")
    input("Hit ENTER to continue")


if __name__ == '__main__':
    main()