import os
import pyglet

class Sprite(object):
    """Base Sprite Class

    Sprites will get their basic position (x, y), movement (dx, dy), and size 
    (w, h) attributes set in this base class. The sprite's image will be set 
    to the image file that corresponds to its subclass name from the images 
    directory. Very basic draw and update methods are implemented but are 
    expected to be overridden in many cases.

    """

    def __init__(self, x, y):
        """ Init position, movement, size, and image values. Also set image. """

        # This class is meant to be subclassed only
        if self.__class__.__name__ == 'Sprite':
            raise NotImplementedError('Don\'t instantiate sprite base class')

        self.x, self.y = x, y
        self.image = images[self.__class__.__name__]

        # Width and Height are taken from this sprite's image object
        self.w, self.h = self.image.width, self.image.height

    def draw(self):
        """ A basic, single-frame blit to the screen """

        self.image.blit(self.x, self.y)

    def update(self):
        """ Move the sprite according to its dx/dy and draw it """

        self.draw()


class Background(Sprite):
    """ Image of a black background and net. Sprite may be a bit overkill """

    pass


class Paddle(Sprite):
    """ Paddle that will be controlled by the player and enemy AI """

    pass


class Ball(Sprite):
    """ Pong ball that will bounce of walls and paddles """

    pass


def load_images():
    """ Creates a dict mapping Sprite classnames to image objects """

    images = {}

    for filename in os.listdir('images'):
        key = filename.split('.')[0]
        value = pyglet.image.load(os.sep.join(['images', filename]))

        images[key] = value

    return images


def update(dt):
    """ Scheduled function that will update sprites and call ai """

    background.update()
    player.update()
    enemy.update()
    ball.update()


# Load images so that Sprite.__init__ will work
images = load_images()

# Load game objects
background = Background(0, 0)
player = Paddle(100, 200)
enemy = Paddle(530, 200)
ball = Ball(120, 214)

window = pyglet.window.Window()

# Schedule our update function and start the game loop
pyglet.clock.schedule(update)
pyglet.app.run()