"""
    Basic pong, with many balls using lists
    by Rory Solomon
 
    For Code Toolkit: Python
    Eugene Lang College, Fall 2020

    Note: In all my while loops below I'm using len(ballX). As we
    discussed in class, the lists ballX, ballY, ballXDirection, and
    ballYDirection *should* all be the same length at all times. So
    really, I could use any of them inside len(). This is not ideal
    programming practice because if one list becomes a different
    length, that could introduce an "index out of bounds" error. For
    this example, it should be OK. But if I were to expand this game
    (for example, if balls were to disappear) I'd need to be careful
    about how I manage the lists.
    
"""

paddle1Y = 250
paddle2Y = 250

def setup ():
    size(600, 600)

    noStroke()
    fill(255)

    rectMode(CENTER)

    global ballX, ballY, ballXDirection, ballYDirection
    # initialize each as a list with just one item
    ballX = [300]
    ballY = [300]
    ballXDirection = [2]
    ballYDirection = [2]

def draw():

    global paddle1Y, paddle2Y, ballX, ballY, ballXDirection, ballYDirection

    background(0)

    # draw ball(s)
    i = 0
    while i < len(ballX):
        ellipse( ballX[i], ballY[i], 10, 10)
        i = i + 1

    # draw paddles
    rect(20, paddle1Y, 10, 50)
    rect(540, paddle2Y, 10, 50)

    # move paddles
    if keyPressed:
        if key == 'q':
            paddle1Y = paddle1Y - 5
        elif key == 'z':
            paddle1Y = paddle1Y + 5
        elif key == 'i':
            paddle2Y = paddle2Y - 5          
        elif key == 'm':
            paddle2Y = paddle2Y + 5

    # check ceiling and floor collision for each ball
    i = 0
    while i < len(ballX):
        if ballY[i] <= 0:
            ballYDirection[i] = 3

        if ballY[i] >= 600:
            ballYDirection[i] = -3
      
        i = i + 1

    # check paddle collisions for each ball
    i = 0
    while i < len(ballX):
        if ballY[i] >= paddle1Y and ballY[i] <= paddle1Y + 50 and ballX[i] <= 20:
            ballXDirection[i] = 1

        if ballY[i] >= paddle2Y and ballY[i] <= paddle2Y + 50 and ballX[i] >= 540:
            ballXDirection[i] = -1

        i = i + 1


    # update all ball positions
    i = 0
    while i < len(ballX):
        ballX[i] = ballX[i] + ballXDirection[i]
        ballY[i] = ballY[i] + ballYDirection[i]
        i = i + 1
        

def mousePressed():
    global ballX, ballY, ballXDirection, ballYDirection
    
    ballX.append(300)
    ballY.append(300)
    ballXDirection.append( random(-3, 3) )
    ballYDirection.append( random(-3, 3) )