"use strict";

const cvs = document.getElementById("snake");
const ctx = cvs.getContext("2d");
const box = 20;

let snake = [{ x: 9 * box, y: 10 * box }];
let food = {
  x: Math.floor(Math.random() * 19 + 1) * box,
  y: Math.floor(Math.random() * 19 + 1) * box,
};
let score = 0;
let d;
let game;

document.addEventListener("keydown", direction);
function direction(event) {
  let key = event.keyCode;
  if ((key == 37 || key == 65) && d != "RIGHT") d = "LEFT";
  else if ((key == 38 || key == 87) && d != "DOWN") d = "UP";
  else if ((key == 39 || key == 68) && d != "LEFT") d = "RIGHT";
  else if ((key == 40 || key == 83) && d != "UP") d = "DOWN";
}

function collision(head, array) {
  return array.some((part) => head.x == part.x && head.y == part.y);
}

function draw() {
  ctx.fillStyle = "#0f380f";
  ctx.fillRect(0, 0, cvs.width, cvs.height);

  ctx.fillStyle = "red";
  ctx.fillRect(food.x, food.y, box, box);

  for (let i = 0; i < snake.length; i++) {
    ctx.fillStyle = i == 0 ? "lime" : "white";
    ctx.fillRect(snake[i].x, snake[i].y, box, box);
    ctx.strokeStyle = "black";
    ctx.strokeRect(snake[i].x, snake[i].y, box, box);
  }

  let snakeX = snake[0].x;
  let snakeY = snake[0].y;

  if (d == "LEFT") snakeX -= box;
  if (d == "UP") snakeY -= box;
  if (d == "RIGHT") snakeX += box;
  if (d == "DOWN") snakeY += box;

  if (snakeX == food.x && snakeY == food.y) {
    score++;
    food = {
      x: Math.floor(Math.random() * 19 + 1) * box,
      y: Math.floor(Math.random() * 19 + 1) * box,
    };
  } else {
    snake.pop();
  }

  let newHead = { x: snakeX, y: snakeY };

  if (
    snakeX < 0 ||
    snakeX >= cvs.width ||
    snakeY < 0 ||
    snakeY >= cvs.height ||
    collision(newHead, snake)
  ) {
    clearInterval(game);
    document.getElementById("restartBtn").style.display = "block";
    return;
  }

  snake.unshift(newHead);

  ctx.fillStyle = "white";
  ctx.font = "20px Arial";
  ctx.fillText("Score: " + score, 10, 20);
}

function restartGame() {
  snake = [{ x: 9 * box, y: 10 * box }];
  food = {
    x: Math.floor(Math.random() * 19 + 1) * box,
    y: Math.floor(Math.random() * 19 + 1) * box,
  };
  score = 0;
  d = "";
  document.getElementById("restartBtn").style.display = "none";
  game = setInterval(draw, 150);
}

document.getElementById("restartBtn").addEventListener("click", restartGame);
game = setInterval(draw, 150);