import pygame  # Import the Pygame library for game development
import random  # Import the random module for generating random numbers

# Initialize Pygame
pygame.init()  # Initialize the Pygame library

# Set up the screen
WIDTH, HEIGHT = 600, 400  # Defines the width and height of the game window
GRID_SIZE = 20  # Defines the size of each grid cell
GRID_WIDTH, GRID_HEIGHT = WIDTH // GRID_SIZE, HEIGHT // GRID_SIZE  # Calculates the number of grid cells
screen = pygame.display.set_mode((WIDTH, HEIGHT))  # Create the game window with the specified dimensions
pygame.display.set_caption("Snake Game")  # Set the title of the game window

# Define colors using RGB values
WHITE = (255, 255, 255)  # Defines the color white
GREEN = (0, 255, 0)  # Defines the color green
RED = (255, 0, 0)  # Defines the color red
BLACK = (0, 0, 0)  # Defines the color black
PINK = (255, 192, 203)  # Defines the color pink
PURPLE = (128, 0, 128)  # Defines the color purple
ORANGE = (255, 165, 0)  # Defines the color orange

# Snake class
class Snake:
    def __init__(self):
        self.length = 1  # Initial length of the snake
        self.positions = [((WIDTH / 2), (HEIGHT / 2))]  # Initial position of the snake's head
        self.direction = random.choice([UP, DOWN, LEFT, RIGHT])  # Initial direction of the snake
        self.color = GREEN  # Color of the snake

    def get_head_position(self):
        return self.positions[0]  # Get the position of the snake's head

    def turn(self, point):
        if self.length > 1 and (point[0]*-1, point[1]*-1) == self.direction:
            return  # Prevents the snake from turning back on itself
        else:
            self.direction = point  # Change the direction of the snake

    def move(self):
        cur = self.get_head_position()
        x, y = self.direction
        new = (((cur[0] + (x*GRID_SIZE)) % WIDTH), (cur[1] + (y*GRID_SIZE)) % HEIGHT)
        if len(self.positions) > 2 and new in self.positions[2:]:
            self.reset()  # Resets the game if snake collides with itself
            return -1
        else:
            self.positions.insert(0, new)  # Move the snake's head to the new position
            if len(self.positions) > self.length:
                self.positions.pop()  # Remove the last segment of the snake if it's longer than its length
            return 0

    def reset(self):
        self.length = 1  # Reset the length of the snake
        self.positions = [((WIDTH / 2), (HEIGHT / 2))]  # Reset the position of the snake's head
        self.direction = random.choice([UP, DOWN, LEFT, RIGHT])  # Reset the direction of the snake

    def draw(self, surface):
        for p in self.positions:
            r = pygame.Rect((p[0], p[1]), (GRID_SIZE, GRID_SIZE))
            pygame.draw.rect(surface, self.color, r)  # Draw the snake on the game surface
            pygame.draw.rect(surface, WHITE, r, 1)  # Draw the border of the snake segments

    def handle_keys(self):
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()  # Quit the game if the window is closed
            elif event.type == pygame.KEYDOWN:
                if event.key == pygame.K_UP:
                    self.turn(UP)  # Turn the snake upwards
                elif event.key == pygame.K_DOWN:
                    self.turn(DOWN)  # Turn the snake downwards
                elif event.key == pygame.K_LEFT:
                    self.turn(LEFT)  # Turn the snake to the left
                elif event.key == pygame.K_RIGHT:
                    self.turn(RIGHT)  # Turn the snake to the right

# Food class
class Food:
    def __init__(self):
        self.position = (0, 0)  # Initial position of the food
        self.color = RED  # Color of the food
        self.randomize_position()  # Set a random position for the food

    def randomize_position(self):
        self.position = (random.randint(0, GRID_WIDTH-1) * GRID_SIZE, random.randint(0, GRID_HEIGHT-1) * GRID_SIZE)  # Set a random position for the food within the grid

    def draw(self, surface):
        r = pygame.Rect((self.position[0], self.position[1]), (GRID_SIZE, GRID_SIZE))
        pygame.draw.rect(surface, self.color, r)  # Draw the food on the game surface
        pygame.draw.rect(surface, WHITE, r, 1)  # Draw the border of the food

# Directions
UP = (0, -1)
DOWN = (0, 1)
LEFT = (-1, 0)
RIGHT = (1, 0)

def main():
    clock = pygame.time.Clock()  # Create a clock object to control the frame rate
    snake = Snake()  # Create an instance of the Snake class
    food = Food()  # Create an instance of the Food class
    score = 0  # Initialize the score to zero

    while True:  # Main game loop
        screen.fill(BLACK)  # Fill the game window with Black color
        snake.handle_keys()  # Handle user input for controlling the snake
        result = snake.move()  # Move the snake
        if result == -1:
            score = 0  # Reset the score if the snake collides with itself
        if snake.get_head_position() == food.position:
            snake.length += 1  # Increase the length of the snake if it eats the food
            score += 1  # Increase the score
            food.randomize_position()  # Move the food to a random position

        snake.draw(screen)  # Draw the snake on the game surface
        food.draw(screen)  # Draw the food on the game surface
        
        # Displaying score
        font = pygame.font.SysFont(None, 25)  # Create a font object
        text = font.render(f"Score: {score}", True, WHITE)  # Render the text displaying the score
        screen.blit(text, (10, 10))  # Draw the text on the game surface

        pygame.display.update()  # Update the display
        clock.tick(10)  # Control the frame rate

if __name__ == "__main__":
    main()  # Start the game