import random

from kivy import app, clock, properties, vector
from kivy.uix import widget


class PongGame(widget.Widget):
    # ADD note: why the None needed... the API allows for *args, **kwargs
    ball = properties.ObjectProperty(None)

    def serve_ball(self):
        self.ball.center = self.center
        # NOTE: Breaking this out
        random_ball_direction = random.randint(0, 360)
        self.ball.velocity = vector.Vector(4, 0).rotate(random_ball_direction)

    def update(self, dt):
        self.ball.move()

        # bounce off top and bottom
        if (self.ball.y < 0) or (self.ball.top > self.height):
            self.ball.velocity_y *= -1

        # bounce off left and right
        if (self.ball.x < 0) or (self.ball.right > self.width):
            self.ball.velocity_x *= -1


class PongBall(widget.Widget):
    velocity_x = properties.NumericProperty(0)
    velocity_y = properties.NumericProperty(0)

    velocity = properties.ReferenceListProperty(velocity_x, velocity_y)

    def move(self):
        self.pos = vector.Vector(*self.velocity) + self.pos


class PongApp(app.App):

    def build(self):
        game = PongGame()
        game.serve_ball()
        clock.Clock.schedule_interval(game.update, 1.0 / 60.0)
        return game


def run_pong_game():
    PongApp().run()


if __name__ == '__main__':
    run_pong_game()