Tic Tac Toe

index.js

#!/usr/bin/env node

const readline = require("readline");
const boxen = require("boxen");

const NUM_ROWS = 3;
const NUM_COLS = 3;

// Set up game loop
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});

// track game state as 2d array
const getEmptyBoard = () => Array.from(Array(NUM_ROWS), () => Array.from(new Array(NUM_COLS)));

const INITIAL_GAME_STATE = {
  board: getEmptyBoard(),
  turn: 'o',
  winner: undefined,
}

const getNextPlayer = (turn) => turn === 'o' ? 'x' : 'o';

// FIXME: DRY this out
const checkForWinner = (boardState) => {
  const winningMoves = [
    [[0,0], [0,1], [0,2]],
    [[1,0], [1,1], [1,2]],
    [[2,0], [2,1], [2,2]],
    [[0,0], [1,0], [2,0]],
    [[0,1], [1,1], [2,1]],
    [[0,2], [1,2], [2,2]],
    [[0,0], [1,1], [2,2]],
    [[0,2], [1,1], [2,0]],
  ];

  const theWinningMove = winningMoves.filter(combo => {
    // TODO: put in helper function
    return boardState[combo[0][0]][combo[0][1]] !== undefined
      && boardState[combo[0][0]][combo[0][1]] === boardState[combo[1][0]][combo[1][1]]
      && boardState[combo[1][0]][combo[1][1]] === boardState[combo[2][0]][combo[2][1]];
  });

  return theWinningMove.length > 0
    && boardState[theWinningMove[0][0][0]][theWinningMove[0][0][1]];
}

const makeMove = (x, y, gameState) => {
  const {
    board,
    turn,
    turn: playerSymbol,
  } = gameState;

  // if move already made only logging error and not advancing game state
  if (board[x][y]) {
    console.error('INVALID MOVE');

    return gameState;
  } 

  // Update position
  board[x][y] = playerSymbol;

  return {
    ...gameState,
    turn: getNextPlayer(turn),
    board,
  }
}

// Main game engine
const getMove = (gameState) => {
    const {
      turn,
    } = gameState;

    rl.question(`It's ${turn}'s move: `, (coordinates) => {

    // Assume input = 'x,y' for now
    const [x, y] = coordinates.trim().split(',');

    const newGameState = makeMove(x, y, gameState);
    const { board } = newGameState;

    renderBoard(board);

    const winner = checkForWinner(board);

    if (winner) {
      console.log('We have a winner!!! Congratulations Player:', winner);
      rl.close();
    } else {
      getMove(newGameState);
    }
  });
}

// pass in 2d array to re-render board with new state
const renderBoard = (movesPlayed) => {
  const boxenOptions = {
    padding: 1,
    margin: 1,
    borderStyle: "round",
    borderColor: "green",
  };

  const board = movesPlayed.map(row =>{
    return row.map(cell => {
      return cell === undefined ? '_' : cell;
    }).join(' ');
  }).join('\n');

  const gameBox = boxen(board, boxenOptions);

  console.log(gameBox);
}

const initGame = () => {
  const gameState = {
    board,
  } = INITIAL_GAME_STATE;

  console.log('Please enter the (0-indexed) row and column you would like to play at. ');

  renderBoard(board);

  getMove(gameState);
}

initGame();