# file: tumble.py
#
# author: Bob Muller
# date: March 17, 2008
#
# 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 is a simple recursive function. It first draws the block
# at a specified angle r (for radians) and then, if the block hasn't
# hit the surface, it erases the block and calls itself again having
# decreased the angle r.
#
def fall(x, y, width, height, r, delta):

    # Draw the block.
    #
    block(x, y, width, height, r, 'Brown')
    
    if r > 0:
                
        # Erase the block.
        #
        block(x, y, width, height, r, 'White')

        fall(x, y, width, height, max(0.0,r-delta), delta)

# tumble is the top-level function. It simply calls tumbleHelp so that it
# can pass along an x-coordinate.
#
def tumble(width, height, delta):

    initialX = -(turtle.window_width() / 2.0) + width

    tumbleHelp(initialX, width, height, delta)

def tumbleHelp(x, width, height, delta):

    if (x - width) < turtle.window_width() / 2.0:
        
        fall(x, 0, width, height, math.pi / 2.0, delta)

        # The block has now fallen to the right. Now continue
        # by calling this routine again with an increased x
        # component and swapping the values of the height and 
	# width variables.
        #
        tumbleHelp(x + height, height, width, delta)