snake.js

import Direction from './direction';

function randomCoords(xMax, yMax) {
return {x: Math.floor(Math.random() * xMax), y: Math.floor(Math.random() * yMax)};
}

var SnakeGameLogic = function SnakeGameLogic(rows, cols, initialSnakePoints, initialDirection) {
  var appleCoords = randomCoords(cols, rows);
  var getApplePoint = function getApplePoint() {
    return appleCoords;
  };

  var score = 0;
  var getScore = function getScore() {
    return score;
  };

  var snakePoints = initialSnakePoints;
  var getSnakePoints = function getSnakePoints() {
    return snakePoints;
  };

  var canContinue = true;
  var shouldContinue = function shouldContinue() {
    return canContinue;
  };

  var direction = initialDirection;
  var input = function input(code) {
    if (Math.abs(direction - code) !== 2) {
      direction = code;
    }
  };

  var update = function update() {
    var head = snakePoints[snakePoints.length - 1];
    var newHead = {x: head.x, y: head.y};
    switch (direction) {
      case 0: newHead.y -= 1; break;
      case 1: newHead.x += 1; break;
      case 2: newHead.y += 1; break;
      case 3: newHead.x -= 1; break;
    }
    snakePoints.push(newHead);

    // if ate apple
    if (newHead.x === appleCoords.x && newHead.y === appleCoords.y) {
      appleCoords = randomCoords(cols, rows);
      score += 1;
    } else {
      snakePoints.shift();
    }

    // if hit wall
    canContinue = !(newHead.x > cols - 1 || newHead.y > rows - 1 || newHead.x < 0 || newHead.y < 0);
  };

  return {
    getApplePoint: getApplePoint,
    getScore: getScore,
    getSnakePoints: getSnakePoints,
    input: input,
    shouldContinue: shouldContinue,
    update: update
  };
};

export default SnakeGameLogic;