import pygame
import random

# Constants
WIDTH, HEIGHT = 400, 400
GRID_SIZE = 20
GRID_WIDTH = WIDTH // GRID_SIZE
GRID_HEIGHT = HEIGHT // GRID_SIZE
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
GREEN = (0, 255, 0)
RED = (255, 0, 0)


class App:

  def __init__(self):
    pygame.init()
    self.screen = pygame.display.set_mode((WIDTH, HEIGHT))
    pygame.display.set_caption("Snake Game")
    self.clock = pygame.time.Clock()
    self.snake = Snake()
    self.food = Food()

  def run(self):
    running = True
    while running:
      for event in pygame.event.get():
        if event.type == pygame.QUIT:
          running = False

      self.snake.handle_keys()
      self.snake.move()
      self.check_collision()

      self.screen.fill(BLACK)
      self.snake.draw(self.screen)
      self.food.draw(self.screen)
      pygame.display.update()
      self.clock.tick(10)

    pygame.quit()

  def check_collision(self):
    if self.snake.head == self.food.position:
      self.snake.length += 1
      self.food.randomize_position()
    if (self.snake.head[0] < 0 or self.snake.head[0] >= GRID_WIDTH
        or self.snake.head[1] < 0 or self.snake.head[1] >= GRID_HEIGHT
        or self.snake.head in self.snake.body[:-1]):
      pygame.quit()


class Snake:

  def __init__(self):
    self.length = 1
    self.body = [(random.randint(0, GRID_WIDTH - 1),
                  random.randint(0, GRID_HEIGHT - 1))]
    self.direction = (1, 0)

  @property
  def head(self):
    return self.body[-1]

  def move(self):
    x, y = self.head
    dx, dy = self.direction
    new_head = ((x + dx) % GRID_WIDTH, (y + dy) % GRID_HEIGHT)
    self.body.append(new_head)
    if len(self.body) > self.length:
      del self.body[0]

  def handle_keys(self):
    keys = pygame.key.get_pressed()
    if keys[pygame.K_UP] and self.direction != (0, 1):
      self.direction = (0, -1)
    elif keys[pygame.K_DOWN] and self.direction != (0, -1):
      self.direction = (0, 1)
    elif keys[pygame.K_LEFT] and self.direction != (1, 0):
      self.direction = (-1, 0)
    elif keys[pygame.K_RIGHT] and self.direction != (-1, 0):
      self.direction = (1, 0)

  def draw(self, surface):
    for segment in self.body:
      pygame.draw.rect(surface, GREEN,
                       (segment[0] * GRID_SIZE, segment[1] * GRID_SIZE,
                        GRID_SIZE, GRID_SIZE))


class Food:

  def __init__(self):
    self.position = (random.randint(0, GRID_WIDTH - 1),
                     random.randint(0, GRID_HEIGHT - 1))

  def randomize_position(self):
    self.position = (random.randint(0, GRID_WIDTH - 1),
                     random.randint(0, GRID_HEIGHT - 1))

  def draw(self, surface):
    pygame.draw.rect(surface, RED,
                     (self.position[0] * GRID_SIZE,
                      self.position[1] * GRID_SIZE, GRID_SIZE, GRID_SIZE))


if __name__ == "__main__":
  game = App()
  game.run()