public class TicTacToe extends TwoPlayerGame implements PlayableGame
{   public static final String BLANK = " ";
    public final int DRAW = 0;
    private String one = BLANK, two = BLANK, three = BLANK, four = BLANK, five = BLANK, six = BLANK,
	seven = BLANK, eight = BLANK, nine = BLANK;
    private int winner;

    public TicTacToe() { 
    }

    public String getRules() {
        return "\n*** The Rules of Tic Tac Toe ***\n" +
	    "                 1 2 3\n" +
	    "                 4 5 6\n" +
	    "                 7 8 9\n" +
	    "Player 1 is X and player 2 is O\n";
    }
    public String getSquare(int n) {
        switch (n) {
	case 1: return one;
	case 2: return two;
	case 3: return three;
	case 4: return four;
	case 5: return five;
	case 6: return six;
	case 7: return seven;
	case 8: return eight;
	case 9: return nine;
	}
	return "";
    }

    public String getWinner() {
        if (winner == 0)
	    return "It's a draw!\n";
        return "Player " + winner + " is the winner.\n";
    }

    public String reportState() {
        return  "\n" +
            one + " | " + two + " | " + three + "\n" +
            "----------\n" +
	    four + " | " + five + " | " + six + "\n" +
            "----------\n" +
	    seven + " | " + eight + " | " + nine + "\n";
    }

    public String prompt() {
        return "\nPlayer " + getPlayer() + ": Type in an empty square, 1 to 9 :  ";
    }

    public String move(String s) {
        int square = Integer.parseInt(s);
        String mark="";
        if (getPlayer()==PLAYER_ONE)
            mark = "X";
	else
	    mark = "O";
        if (makeLegalMove(square,mark)) {
            changePlayer();
            if (gameOver()) {
                return reportState() + "\nGame over! " + getWinner() + "\n";
	    } else {
                return reportState() + prompt();
	    }
	}
        return "\nOops. " + square + " is an illegal move." + prompt();
    }

    public boolean gameOver() {
        return xWins() || oWins() || itsADraw();
    }
    private boolean itsADraw() {
        for (int k = 0; k<= 9; k++) 
            if (getSquare(k).equals(BLANK))
		return false;
	winner = DRAW;
	return true;
    }
    private boolean xWins() {
        if (one.equals("X") && one.equals(two) && two.equals(three) ||
	    four.equals("X") && four.equals(five) && five.equals(six) ||
	    seven.equals("X") && seven.equals(eight) && eight.equals(nine) ||
	    one.equals("X") && one.equals(five) && five.equals(nine) ||
            one.equals("X") && one.equals(four) && four.equals(seven) ||
	    two.equals("X") && two.equals(five) && five.equals(eight) ||
	    three.equals("X") && three.equals(six) && six.equals(nine) ||
	    three.equals("X") && three.equals(five) && five.equals(seven)) {
	    winner = PLAYER_ONE;
	    return true;
	}
	return false;
    }
    private boolean oWins() {
        if (one.equals("O") && one.equals(two) && two.equals(three) ||
	    four.equals("O") && four.equals(five) && five.equals(six) ||
	    seven.equals("O") && seven.equals(eight) && eight.equals(nine) ||
	    one.equals("O") && one.equals(five) && five.equals(nine) ||
            one.equals("O") && one.equals(four) && four.equals(seven) ||
	    two.equals("O") && two.equals(five) && five.equals(eight) ||
	    three.equals("O") && three.equals(six) && six.equals(nine) ||
	    three.equals("O") && three.equals(five) && five.equals(seven)) {
	    winner = PLAYER_TWO;
	    return true;
	}
	return false;
    }

    public void play(UserInterface ui) {
        IPlayer computer = null;
        int answer = 0;
        ui.prompt("Tic Tac Toe: Two humans or one human? ");
        int nHumans = Integer.parseInt(ui.getUserInput());
        computerIsPlayer = nHumans == 1;
        ui.report(getRules());
        if (computerIsPlayer) {
            computer = new TicTacToePlayer(this);
	}
        while (!gameOver())
        {   ui.report(reportState());
            if (getPlayer() == PLAYER_TWO || !computerIsPlayer) 
	    {    ui.prompt(prompt());
                 answer = Integer.parseInt(ui.getUserInput()); // Get move 
		 if (getPlayer() == PLAYER_ONE) {
		     if (makeLegalMove(answer, "X"))
			 changePlayer();
		 } else {
		     if (makeLegalMove(answer, "O"))
			 changePlayer();
		 }
	    } else {
                answer = Integer.parseInt(computer.move(prompt()));
                ui.report("\nMy turn. I move to  " + answer + "\n");
		if (makeLegalMove(answer, "X"))
		    changePlayer();
	    }
        } // while
	ui.report(reportState() + getWinner());  // The game is now over
    }

    public boolean makeLegalMove(int m, String s) {
	switch(m) {
        case 1: if (one.equals(BLANK)) {one = s; return true; } break;
        case 2: if (two.equals(BLANK)) {two = s; return true;}; break;
        case 3: if (three.equals(BLANK)) {three = s; return true; } break;
        case 4: if (four.equals(BLANK)) {four = s; return true; } break;
        case 5: if (five.equals(BLANK)) {five = s; return true; } break;
        case 6: if (six.equals(BLANK)) {six = s; return true; } break;
        case 7: if (seven.equals(BLANK)) {seven = s; return true; } break;
        case 8: if (eight.equals(BLANK)) {eight = s; return true; } break;
        case 9: if (nine.equals(BLANK)) { nine = s; return true; } break;
	}
        return false;
    }

    public static void main(String args[]) {
        KeyboardReader ui = new KeyboardReader();
        TicTacToe game = new TicTacToe();
        game.play((UserInterface)ui);
    }

}