33. Gra Snake

const GRID_SIZE = 20;
const INITIAL_SNAKE = [{ x: 10, y: 10 }];
const INITIAL_DIRECTION = { x: 1, y: 0 };

function useSnakeGame() {
  const [snake, setSnake] = useState(INITIAL_SNAKE);
  const [food, setFood] = useState(generateFood(INITIAL_SNAKE));
  const [direction, setDirection] = useState(INITIAL_DIRECTION);
  const [gameOver, setGameOver] = useState(false);
  const [score, setScore] = useState(0);
  const directionRef = useRef(direction); // ref dla aktualnego kierunku w setInterval

  useEffect(() => { directionRef.current = direction; }, [direction]);

  useEffect(() => {
    if (gameOver) return;
    const interval = setInterval(() => {
      setSnake((prev) => {
        const newHead = {
          x: prev[0].x + directionRef.current.x,
          y: prev[0].y + directionRef.current.y,
        };
        // Kolizja ze ścianą
        if (newHead.x < 0 || newHead.x >= GRID_SIZE || newHead.y < 0 || newHead.y >= GRID_SIZE) {
          setGameOver(true);
          return prev;
        }
        // Kolizja z samym sobą
        if (prev.some((seg) => seg.x === newHead.x && seg.y === newHead.y)) {
          setGameOver(true);
          return prev;
        }
        const ateFood = newHead.x === food.x && newHead.y === food.y;
        if (ateFood) {
          setScore((s) => s + 10);
          setFood(generateFood([newHead, ...prev]));
          return [newHead, ...prev];
        }
        return [newHead, ...prev.slice(0, -1)];
      });
    }, 150);
    return () => clearInterval(interval);
  }, [gameOver, food]);

  function handleKey(e) {
    const keys = {
      ArrowUp:    { x: 0, y: -1 },
      ArrowDown:  { x: 0, y: 1 },
      ArrowLeft:  { x: -1, y: 0 },
      ArrowRight: { x: 1, y: 0 },
    };
    if (keys[e.key]) {
      e.preventDefault();
      setDirection(keys[e.key]);
    }
  }

  return { snake, food, score, gameOver, handleKey };
}

function generateFood(snake) {
  let pos;
  do {
    pos = { x: Math.floor(Math.random() * GRID_SIZE), y: Math.floor(Math.random() * GRID_SIZE) };
  } while (snake.some((s) => s.x === pos.x && s.y === pos.y));
  return pos;
}