class Board:
    """A tic-tac-toe board."""
    def __init__(self):
        self.squares = {}
        self.clear()
    
    def set_square(self, sq, piece):
        self.squares[sq] = piece;

    def clear_square(self, sq):
        self.squares[sq] = '-'

    def clear(self):
        for x in range(9):
            self.squares[x] = '-'

    def get_pieces(self, piece):
        opensq = []
        for x,y in self.squares.items():
            if y == piece:
                opensq.append(x)
        return set(opensq)

    def open_squares(self):
        return self.get_pieces("-")

    def render(self):
        for x in range(9):
            print(self.squares[x], end="")
            if x % 3 == 2:
                print()

class Player:
    """A tic-tac-toe player"""
    def __init__(self, piece):
        self.piece = piece

    def make_move(self, game):
        pass

class HumanPlayer(Player):
    def make_move(self, game):
        sq = "a"
        sqs = game.open_squares()
        print("Which square would you like (1-9)?")
        while sq not in sqs:
            try:
                sq = int(input("> "))-1
            except:
                sq = "a"
                print("A number 1-9 please")
        game.set_square(sq, self.piece)

class AIPlayer(Player):
    def choose_move(self, game, player, oplayer, alpha=-100, beta=100, first=False):
        if game.game_over():
            return game.evaluate(player)
        best = -2
        best_sq = -1
        moves = game.open_squares()
        for move in moves:
            game.set_square(move, player.piece)
            alpha = max(alpha, -self.choose_move(game, oplayer, player, -beta, -alpha))
            game.clear_square(move)
            if alpha > best:
                best = alpha
                best_sq = move
            if(alpha >= beta):
                break;
        if first:
            return best_sq
        return best
    
    def make_move(self, game):
        if game.player1 == self:
            y = game.player2
        else:
            y = game.player1
        game.set_square(self.choose_move(game, self, y, first=True), self.piece)

class Game:
    def __init__(self, p1, p2):
        self.board = Board()
        self.player1 = p1
        self.player2 = p2
        self.turn = p1
        self.wins = ({0,1,2},{3,4,5},{6,7,8},{0,3,6},
                     {1,4,7},{2,5,8},{0,4,8},{2,4,6})

    def set_square(self, sq, piece):
        self.board.set_square(sq, piece)

    def clear_square(self, sq):
        self.board.clear_square(sq)

    def open_squares(self):
        return self.board.open_squares()

    def reset(self):
        self.board.clear()

    def check_win(self, player):
        psquares = self.board.get_pieces(player.piece)
        for win in self.wins:
            if psquares & win == win:
                return True
        return False

    def check_filled(self):
        if len(self.open_squares()) == 0:
            return True
        return False

    def game_over(self):
        if self.check_win(self.player1) or \
           self.check_win(self.player2) or \
           self.check_filled():
            return True
        return False
            
    def evaluate(self, player):
        p1win = self.check_win(self.player1)
        p2win = self.check_win(self.player2)
        if p1win:
            if player == self.player1:
                return 1
            return -1
        if p2win:
            if player == self.player2:
                return 1
            return -1
        return 0

    def play(self):
        while not self.game_over():
            self.board.render()
            self.turn.make_move(self)
            if self.turn == self.player1:
                self.turn = self.player2
            else:
                self.turn = self.player1
        self.board.render()
        end = self.evaluate(self.player1)
        if end == 1:
            print("Player one wins!")
        elif end == -1:
            print("Player two wins!")
        else:
            print("Cat's game!")

val = "x"
print("Is player one human?")
while val != "y" and val != "n":
    val = input("y/n: ").lower()
if val == "y":
    h = HumanPlayer("X")
else:
    h = AIPlayer("X")

val = "x"
print("Is player two human?")
while val != "y" and val != "n":
    val = input("y/n: ").lower()
if val == "y":
    c = HumanPlayer("O")
else:
    c = AIPlayer("O")

g = Game(h, c)

play =  "y"
while play == "y":
    g.play()
    g.reset()
    print("Play again?")
    play = input("y/n: ").lower()