tic_tac_toe_node.js

/**
  move positions

   0 | 1 | 2
  ---+---+---
   3 | 4 | 5
  ---+---+---
   6 | 7 | 8

*/

exports.game = function() {
  var sys = require('sys');
  var WinningPatterns =
    [[(/ OO....../),0],[(/O..O.. ../),6],
     [(/......OO /),8],[(/.. ..O..O/),2],
     [(/ ..O..O../),0],[(/...... OO/),6],
     [(/..O..O.. /),8],[(/OO ....../),2],
     [(/ ...O...O/),0],[(/..O.O. ../),6],
     [(/O...O... /),8],[(/.. .O.O../),2],
     [(/O O....../),1],[(/O.. ..O../),3],
     [(/......O O/),7],[(/..O.. ..O/),5],
     [(/. ..O..O./),1],[(/... OO.../),3],
     [(/.O..O.. ./),7],[(/...OO .../),5]];
  
  var BlockingPatterns = 
    [[(/  X . X  /),1],[(/ XX....../),0],[(/X..X.. ../),6],
     [(/......XX /),8],[(/.. ..X..X/),2],[(/ ..X..X../),0],
     [(/...... XX/),6],[(/..X..X.. /),8],[(/XX ....../),2],
     [(/ ...X...X/),0],[(/..X.X. ../),6],[(/X...X... /),8],
     [(/.. .X.X../),2],[(/X X....../),1],[(/X.. ..X../),3],
     [(/......X X/),7],[(/..X.. ..X/),5],[(/. ..X..X./),1],
     [(/... XX.../),3],[(/.X..X.. ./),7],[(/...XX .../),5],
     [(/ X X.. ../),0],[(/ ..X.. X /),6],[(/.. ..X X /),8],
     [(/ X ..X.. /),2],[(/  XX.. ../),0],[(/X.. .. X /),6],
     [(/.. .XX   /),8],[(/X  ..X.. /),2],[(/ X  ..X../),0],
     [(/ ..X..  X/),6],[(/..X..  X /),8],[(/X  ..X.. /),2]];
       
  var WonPatterns =
    [[(/OOO....../),'O'], [(/...OOO.../),'O'],
     [(/......OOO/),'O'], [(/O..O..O../),'O'],
     [(/.O..O..O./),'O'], [(/..O..O..O/),'O'],
     [(/O...O...O/),'O'], [(/..O.O.O../),'O'],
     [(/XXX....../),'X'], [(/...XXX.../),'X'],
     [(/......XXX/),'X'], [(/X..X..X../),'X'],
     [(/.X..X..X./),'X'], [(/..X..X..X/),'X'],
     [(/X...X...X/),'X'], [(/..X.X.X../),'X']];
  var board = [];
  for (var i=0; i<9; i+=1) {
    board.push(' ');
  }
  var X = 'X',
      O = 'O';
  var players = [X, O],
      turn = X;
      
  var moveCPU = function() {
    var movePos;
    movePos = getWinningPatternMove();
    if (movePos === -1) {
      movePos = getBlockingPatternMove();
      if (movePos === -1) {
        movePos = getFirstAvailableMove();
      }
    }
    move(movePos, O);
  };
  var move = function(pos, piece) {
    if (piece !== turn) { return false; }
    pos = Number(pos);
    if (pos >= 0 && pos <= 8 &&
      !isNaN(pos) && board[pos] === ' ') {
      board.splice(pos, 1, piece);
      turn = (piece === X) ? O : X;
      return true;
    }
    return false;
  };
  var getDisplay = function() {
    var display = 
      '\n\n' +
      ' ' + board[0] + ' |' +
      ' ' + board[1] + ' |' +
      ' ' + board[2] +
      '\n---+---+---\n' +
      ' ' + board[3] + ' |' +
      ' ' + board[4] + ' |' +
      ' ' + board[5] +
      '\n---+---+---\n' +
      ' ' + board[6] + ' |' +
      ' ' + board[7] + ' |' +
      ' ' + board[8] +
      '\n\n';
    return display;
  };
  var display = function() {
    sys.print(getDisplay());
  };
  var isBoardFilled = function() {
    var movePos = getFirstAvailableMove();
    if (movePos === -1) {
      display();
      sys.print('Game is a draw.\n');
      process.stdio.close();
      return true;
    }
    return false;
  };
  var isGameWinner = function() {
    var flatBoard = board.join(''),
        i, max = WonPatterns.length, array;
    var gameWinner;
    for (i=0; i<max; i+=1) {
      array = flatBoard.match(WonPatterns[i][0]);
      if (array) { gameWinner = WonPatterns[i][1]; }
    }
    if (gameWinner) {
      display();
      sys.print(gameWinner + ' is the winner!\n');
      process.stdio.close();
      return true;
    }
    return false;
  };
  var getWinningPatternMove = function() {
    var flatBoard = board.join(''),
        i, max = WinningPatterns.length, array;
    for (i=0; i<max; i+=1) {
      array = flatBoard.match(WinningPatterns[i][0]);
      if (array) { return WinningPatterns[i][1]; }
    }
    return -1;
  };
  var getBlockingPatternMove = function() {
    var flatBoard = board.join(''),
        i, max = BlockingPatterns.length, array;
    for (i=0; i<max; i+=1) {
      array = flatBoard.match(BlockingPatterns[i][0]);
      if (array) { return BlockingPatterns[i][1]; }
    }
    return -1;
  };
  var getFirstAvailableMove = function() {
    if (board[4] === ' ') {
      return 4;
    }
    return board.indexOf(' ');
  };
  return {
    play: function() {
      display();
      sys.print("Enter your move [0-8]: ");
      process.stdio.addListener('data', function(response) {
        if (move(response, X)) {
          if (!isGameWinner() && !isBoardFilled()) {
              moveCPU();
              if (!isGameWinner()) {
                display();
                sys.print("Enter your move [0-8]: ");
              }
          }
        } else {
          sys.print("\nI'm sorry Dave, I'm afraid I can't do that.\n");
          sys.print("Enter your move [0-8]: ");
        }
      });
      process.stdio.open();
    },
    getBoardDisplay : function() {
      return getDisplay();
    },
    getTurn: function() {
      return turn;
    },
    getBoard: function() {
      return board.slice(0);
    },
    getCpuGamePiece: function() {
      return O;
    },
    getHumanGamePiece: function() {
      return X;
    },
    movePlayer: function(pos) {
      return move(pos, X);
    }
  };
};