#----------------------------------------------------------------------
# Randomness and the Sierpinski Gasket
# See page 261 of the Computer Science Companion
#
# Copyright (C) February 17, 2017 -- Dr. William T. Verts
#
# Once the random library has been imported:
#    import random
# then a whole bunch of functions become available:
#    random.random()          returns a float >= 0.0 and < 1.0
#    random.randrange(N)      returns an int >= 0 and < N
#    random.randint(M,N)      returns an int >= M and <= N
#    random.choice(L)         returns a value from the list L
#    random.seed(N)           restarts the random sequence at N
#
# I wish to create a drawing using randomness.  First, pick three 2D
# points P0, P1, and P2, where each has an X and Y value.  For example,
# point P0 would be defined by variables P0X and P0Y.  Initially, the
# three points are placed at the top center of the canvas, lower left
# corner, and lower right corner.  The three points don't move.
#
# Pick a fourth point PP that will move around the screen.  Start it
# at P0.  In an infinite loop: pick one of the three fixed points at
# random, then move PP to a point halfway between its current position
# and the selected point, drop a dot on screen at PP's new position,
# repaint the screen.
#
# Will the triangle between P0-P1-P2 eventually fill in?  NO!
# The figure formed is a fractal called a Sierpinski Gasket.
#----------------------------------------------------------------------

import random

def Main1():
    W = 800
    H = 600
    Canvas = makeEmptyPicture(W,H)
    show(Canvas)
    P0X = W / 2
    P0Y = 0
    P1X = 0
    P1Y = H - 1
    P2X = W - 1
    P2Y = H - 1
    PPX = P0X
    PPY = P0Y
    
    while (True):
        N = random.randrange(3)
        if (N == 0):
            PPX = (PPX + P0X) / 2
            PPY = (PPY + P0Y) / 2
            MyColor = red
        elif (N == 1):
            PPX = (PPX + P1X) / 2
            PPY = (PPY + P1Y) / 2
            MyColor = green
        else:
            PPX = (PPX + P2X) / 2
            PPY = (PPY + P2Y) / 2
            MyColor = blue
            
        PX = getPixel(Canvas,PPX,PPY)
        setColor(PX, MyColor)
        repaint(Canvas)
    return

#----------------------------------------------------------------------
# The screen updates far too slowly.  That's because the repaint is
# called after every pixel.  To refresh the screen only after every
# 1000 pixels, you'll need a counter variable that starts at 1000 and
# counts down every pass through the loop - when it reaches zero the
# screen is refreshed and the counter reinitialized.
#----------------------------------------------------------------------

def Main2():
    W = 800
    H = 600
    Canvas = makeEmptyPicture(W,H)
    show(Canvas)
    P0X = W / 2
    P0Y = 0
    P1X = 0
    P1Y = H - 1
    P2X = W - 1
    P2Y = H - 1
    PPX = P0X
    PPY = P0Y
    Counter = 1000
    
    while (True):
        N = random.randrange(3)
        if (N == 0):
            PPX = (PPX + P0X) / 2
            PPY = (PPY + P0Y) / 2
            MyColor = red
        elif (N == 1):
            PPX = (PPX + P1X) / 2
            PPY = (PPY + P1Y) / 2
            MyColor = green
        else:
            PPX = (PPX + P2X) / 2
            PPY = (PPY + P2Y) / 2
            MyColor = blue
            
        PX = getPixel(Canvas,PPX,PPY)
        setColor(PX, MyColor)
        Counter = Counter - 1
        if (Counter == 0):
            repaint(Canvas)
            Counter = 1000
    return

#----------------------------------------------------------------------
# Colors can be either selected at random or synthesized at random.
# Here the lower-left triangle pixels are chosen from the list
# containing green, blue, and cyan.  The pixels in the lower-right
# triangle are synthesized by picking random values for each of the
# three primary colors (R, G, and B).
#----------------------------------------------------------------------

def Main3():
    W = 800
    H = 600
    Canvas = makeEmptyPicture(W,H)
    show(Canvas)
    P0X = W / 2
    P0Y = 0
    P1X = 0
    P1Y = H - 1
    P2X = W - 1
    P2Y = H - 1
    PPX = P0X
    PPY = P0Y
    Counter = 1000
    
    while (True):
        N = random.randrange(3)
        if (N == 0):
            PPX = (PPX + P0X) / 2
            PPY = (PPY + P0Y) / 2
            MyColor = red
        elif (N == 1):
            PPX = (PPX + P1X) / 2
            PPY = (PPY + P1Y) / 2
            MyColor = random.choice([green,blue,cyan])
        else:
            PPX = (PPX + P2X) / 2
            PPY = (PPY + P2Y) / 2
            R = random.randrange(256)
            G = random.randrange(256)
            B = random.randrange(256)
            MyColor = makeColor(R,G,B)
            
        PX = getPixel(Canvas,PPX,PPY)
        setColor(PX, MyColor)
        Counter = Counter - 1
        if (Counter == 0):
            repaint(Canvas)
            Counter = 1000
    return

#----------------------------------------------------------------------
# Finally, the three corners of the triangle can themselves be
# placed at random around the canvas.
#----------------------------------------------------------------------

def Main4():
    W = 800
    H = 600
    Canvas = makeEmptyPicture(W,H)
    show(Canvas)
    P0X = random.randrange(W)
    P0Y = random.randrange(H)
    P1X = random.randrange(W)
    P1Y = random.randrange(H)
    P2X = random.randrange(W)
    P2Y = random.randrange(H)
    PPX = P0X
    PPY = P0Y
    Counter = 1000
    
    while (True):
        N = random.randrange(3)
        if (N == 0):
            PPX = (PPX + P0X) / 2
            PPY = (PPY + P0Y) / 2
            MyColor = red
        elif (N == 1):
            PPX = (PPX + P1X) / 2
            PPY = (PPY + P1Y) / 2
            MyColor = random.choice([green,blue,cyan])
        else:
            PPX = (PPX + P2X) / 2
            PPY = (PPY + P2Y) / 2
            R = random.randrange(256)
            G = random.randrange(256)
            B = random.randrange(256)
            MyColor = makeColor(R,G,B)
            
        PX = getPixel(Canvas,PPX,PPY)
        setColor(PX, MyColor)
        Counter = Counter - 1
        if (Counter == 0):
            repaint(Canvas)
            Counter = 1000
    return
    
#----------------------------------------------------------------------
# CHALLENGE FOR NEXT CLASS
#
# By rethinking the problem, can you rewrite the program to be
# significantly shorter and use fewer variables?  (You may need
# to write a helper function!)
#----------------------------------------------------------------------