# Tic Tac Toe

import random

def drawBoard(board):
# This function prints out the board that it was passed.
# "board" is a list of 10 strings representing the board (ignore index 0)
    print '    |    |'
    print ' ' + board[7] + '  | ' + board[8] + '  | ' + board[9]
    print '    |    |'
    print '-----------'
    print '    |    |'
    print ' ' + board[4] + '  | ' + board[5] + '  | ' + board[6]
    print '    |    |'
    print '-----------'
    print '    |    |'
    print ' ' + board[1] + '  | ' + board[2] + '  | ' + board[3]
    print '    |    |'

def inputPlayerLetter():
    # Let's the player type which letter they want to
    # Returns a list with the player's letter as the first item, and the computer's letter as the second.
    letter = ''
    while not (letter == 'X' or letter == 'O'):
        print 'Do you want to be X or O?'
        letter = raw_input().upper()
        # the first element in the tuple is the player's letter, the second is the computer's letter.
    if letter == 'X':
        return ['X', 'O']
    else:
        return ['O', 'X']
def whoGoesFirst():
    # Randomly choose the player who goes first.
    if random.randint(0, 1) == 0:
        return 'computer'
    else:
        return 'player'
def playAgain():
    # This function returns True if the player wants to play again, otherwise it returns False.
    print 'Do you want to play again? (yes or no)'
    return raw_input().lower().startswith('y')

def makeMove(board, letter, move):
    board[move] = letter

def isWinner(bo, le):
    # Given a board and a player's letter, this function returns True if that player has won.
    # We use bo instead of board and le instead of letter so we don't have to type as much.
    return ((bo[7] == le and bo[8] == le and bo[9] ==le) or # across the top
            (bo[4] == le and bo[5] == le and bo[6] == le) or # across the middle
            (bo[1] == le and bo[2] == le and bo[3] == le) or #across the bottom
            (bo[7] == le and bo[4] == le and bo[1] == le) or # down the left side
            (bo[8] == le and bo[5] == le and bo[2] == le) or #down the middle
            (bo[9] == le and bo[6] == le and bo[3] == le) or #down the right side
            (bo[7] == le and bo[5] == le and bo[3] == le) or #diagonal
            (bo[9] == le and bo[5] == le and bo[1] == le)) # diagonal

def getBoardCopy(board):
    # Make a duplicate of the board list and return it the duplicate.
    dupeBoard = []

    for i in board:
        dupeBoard.append(i)
        
    return dupeBoard

def isSpaceFree(board, move):
    # Return true if the passed move is free on the passed board.
    return board[move] == ' '

def getPlayerMove(board):
    # Let the player type in their move.
    move = ' '
    while move not in '1 2 3 4 5 6 7 8 9'.split() or not isSpaceFree(board, int(move)):
        print 'What is your next move? (1-9)'
        move = raw_input()
    return int(move)

def chooseRandomMoveFromList(board, movesList):
    # Returns a valid move from the passed list on the passed board.
    # Returns None if there is no valid move.
    possibleMoves = []
    for i in movesList:
        if isSpaceFree(board, i):
            possibleMoves.append(i)

    if len(possibleMoves) != 0:
        return random.choice(possibleMoves)
    else:
        return None

def getComputerMove(board, computerLetter):
    # Given a board and the computer's letter, determine where to move and return that move.
    if computerLetter == 'X':
        playerLetter = 'O'
    else:
            playerLetter = 'X'
            # Here is our algorithm for our Tic Tac Toe AI:
            # First, check if we can win in the next move
    for i in range(1, 9):
            copy = getBoardCopy(board)
            if isSpaceFree(copy, i):
                    makeMove(copy, computerLetter, i)
                    if isWinner(copy, computerLetter):
                        return i

                    # Check if the player could win on their next move, and block them.
    for i in range(1, 9):
            copy = getBoardCopy(board)
            if isSpaceFree(copy, i):
                    makeMove(copy, playerLetter, i)
                    if isWinner(copy, playerLetter):
                                return i
                            # Try to take one of the corners, if they are free.
    move = chooseRandomMoveFromList(board, [1, 3, 7, 9])
    if move != None:
        return move
                            # Try to take the center, if it is free.
    if isSpaceFree(board, 5):
        return 5

# Move on one of the sides.
    return chooseRandomMoveFromList(board, [2, 4, 6, 8])

def isBoardFull(board):
    # Return True if every space on the board has been taken. Otherwise return False.
    for i in range(1, 10):
        if isSpaceFree(board, i):
            return False
        return True


print 'Welcome to Tic Tac Toe!'

while True:
    # Reset the board
    theBoard = [' '] * 10
    playerLetter, computerLetter = inputPlayerLetter()
    turn = whoGoesFirst()
    print 'The ' + turn + ' will go first.'
    gameIsPlaying = True
    while gameIsPlaying:
        if turn == 'player':
            # Player's turn.
            drawBoard(theBoard)
            move = getPlayerMove(theBoard)
            makeMove(theBoard, playerLetter, move)
            if isWinner(theBoard, playerLetter):
                drawBoard(theBoard)
                print 'Hooray! You have won the game!'
                gameIsPlaying = False
            else:
                if isBoardFull(theBoard):
                    drawBoard(theBoard)
                    print 'The game is a tie!'
                    break
                else:
                    turn = 'computer'
        else:# Computer's turn.
            move = getComputerMove(theBoard, computerLetter)
            makeMove(theBoard, computerLetter, move)
            if isWinner(theBoard, computerLetter):
                drawBoard(theBoard)
                print 'The computer has beaten you! You lose.'
                gameIsPlaying = False
            else:
                if isBoardFull(theBoard):
                    drawBoard(theBoard)
                    print 'The game is a tie!'
                    break
                else:
                    turn = 'player'
        if not playAgain():
            break