'''
    graphics3.py
    Jeff Ondich, 11 October 2018

    Started in Pascal on 1/25/95
    Ported to C++, Java, and Python
    Adapted to Python 3 by Jed Yang in 2016

    1. Try it.

    2. How can you slow down or speed up the motion of the ball?

    3. I can speed up the animation, to some point, by changing the value in the
       time.sleep() function.  However, at some point, the screen flashes and
       the animation no longer looks good.  Is there something you can change in
       the step() method to speed up the animation?

    4. Try to get the ball to bounce from side to side instead
       of up and down.
 
    5. Can you get the colors to change gradually from red to blue
       and back instead of abruptly?
'''

import time
from graphics import *

class BouncingBall:
    def __init__(self, x, y, radius, window):
        self.window = window
        self.going_up = False
        self.down_color = color_rgb(200, 10, 60)
        self.up_color = color_rgb(60, 60, 200)
        self.circle = Circle(Point(x, y), radius)
        self.circle.setFill(self.down_color)
        self.circle.draw(window)

    def step(self):
        # Move the ball
        if self.going_up:
            dy = -4
        else:
            dy = 4
        self.circle.move(0, dy)

        # Does the ball need to bounce?
        height = self.window.getHeight()
        width = self.window.getWidth()
        x = self.circle.getCenter().getX()
        y = self.circle.getCenter().getY()

        if y + dy >= height - self.circle.getRadius():
            self.going_up = True
            self.circle.setFill(self.up_color)
        elif y + dy <= self.circle.getRadius():
            self.going_up = False
            self.circle.setFill(self.down_color)

def main():
    # First, create a window with a white background.
    window_width = 650
    window_height = 500
    window = GraphWin('Bounce', window_width, window_height)
    window.setBackground(color_rgb(255, 255, 255))

    # Create a BouncingBall object with the specified position and size,
    # and associate it with the window created above.
    ball = BouncingBall(window_width / 2, 50, 50, window)

    # Until the user kills the program with a Ctrl+C, move the ball
    # one step, wait for a bit, move the ball another step, wait, etc.
    print('Type Ctrl-C in the terminal window to make the animation stop.')
    while True:
        ball.step()
        time.sleep(0.02)

main()