import pygame
import sys
import random

# Initialize Pygame
pygame.init()

# Constants
SCREEN_WIDTH, SCREEN_HEIGHT = 640, 480
GRID_SIZE = 20
FPS = 10

# Colors
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
GREEN = (0, 255, 0)
RED = (255, 0, 0)


class Game:
    def __init__(self):
        # Set up the display
        self.screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT))
        self.clock = pygame.time.Clock()
        self.snake = Snake([(SCREEN_WIDTH // 2, SCREEN_HEIGHT // 2)], (0, -1), 1)
        self.food = Food(self.generate_food_position())

    def generate_food_position(self):
        return (random.randint(0, (SCREEN_WIDTH // GRID_SIZE) - 1) * GRID_SIZE,
                random.randint(0, (SCREEN_HEIGHT // GRID_SIZE) - 1) * GRID_SIZE)

    def main_loop(self):
        while True:
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    pygame.quit()
                    sys.exit()

            # Handle user input and update game state
            self.handle_input()
            self.update_game_state()

            # Draw everything
            self.screen.fill(BLACK)
            self.draw_snake()
            self.draw_food()
            pygame.display.flip()

            # Cap the frame rate
            self.clock.tick(FPS)

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

    def update_game_state(self):
        self.snake.move()
        if self.snake.position[0] == self.food.position:
            self.snake.grow()
            self.food.position = self.generate_food_position()

    def draw_snake(self):
        for segment in self.snake.position:
            pygame.draw.rect(self.screen, GREEN, (segment[0], segment[1], GRID_SIZE, GRID_SIZE))

    def draw_food(self):
        pygame.draw.rect(self.screen, RED, (self.food.position[0], self.food.position[1], GRID_SIZE, GRID_SIZE))


class Snake:
    def __init__(self, position, direction, length):
        self.position = position
        self.direction = direction
        self.length = length

    def move(self):
        head_x, head_y = self.position[0]
        new_dir_x, new_dir_y = self.direction
        new_head = (head_x + new_dir_x * GRID_SIZE, head_y + new_dir_y * GRID_SIZE)
        self.position.insert(0, new_head)
        if len(self.position) > self.length:
            self.position.pop()

    def change_direction(self, new_direction):
        self.direction = new_direction

    def grow(self):
        self.length += 1


class Food:
    def __init__(self, position):
        self.position = position

    def spawn(self, board_size):
        pass  # This method is not used in this implementation