# file: tumbleWhileTrig.py
#
# author: Bob Muller
# date: November 11, 2007
#
# This file contains python code using the turtle graphics system.
# The code in this file, causes a block to tumble across the x-axis.
# 
# Note that the solution presented here uses the math.sin and math.cos
# functions and recursive functions.
#
# The code contained here is used in CS074 The Digital World.
#
import turtle
import math

def setup(h,w):
    turtle.setup(height=h,width=w)
    turtle.radians()
    turtle.up()

# block draws a colored block with corner at point (x,y) and inclined
# at (radian) angle r.
#
def block(x, y, width, height, r, color):

    turtle.color(color)
    
    # Compute the Cartesian coordinates of the 3 other
    # corners of the block.
    #
    rightAngle = math.pi / 2.0

    x1 = x + math.cos(r) * height
    y1 = y + math.sin(r) * height
    
    x2 = x1 + math.cos(r + rightAngle) * width
    y2 = y1 + math.sin(r + rightAngle) * width
    
    x3 = x + math.cos(r + rightAngle) * width
    y3 = y + math.sin(r + rightAngle) * width

    # Now do the drawing.
    #
    turtle.goto(x,y)
    turtle.begin_fill()
    turtle.goto(x1, y1)
    turtle.goto(x2, y2)
    turtle.goto(x3, y3)
    turtle.goto(x,y)

    turtle.end_fill()

# fall uses the block function to draw the block at a specified angle 
# r (for radians).
#
def fall(x, y, width, height, r, delta):

    while r > 0.0:

        # Draw the block.
        #
        block(x, y, width, height, r, 'Brown')
                 
        # Erase the block.
        #
        block(x, y, width, height, r, 'White')

        # Now decrease the angle. We use the max function to
        # prevent the block from falling below the line y == 0.
        #
        r = max(0.0, r - delta)


# tumble is the top-level. width is the block width, height is the height and delta is 
# the rate of change.
#
def tumble(width, height, delta):
    
    # The center is x == 0 so -halfWidth is left edge and halfWidth is right edge.
    #
    halfWidth = turtle.window_width() / 2.0

    x = -halfWidth + width

    while (x - width) < halfWidth:
        
        # Use the fall function to make the block fall. NB: math.pi / 2.0 == 90 degrees.
        #
        fall(x, 0, width, height, math.pi / 2.0, delta)

        # Now that the block has fallen over, move the block to the right,
        #
        x = x + height        

        # and swap the height and width. NB: A temp is required.
        #
        temp = height
        height = width
        width = temp