#!/usr/bin/env python3

"""
Animated Towers of Hanoi using Tk with optional bitmap file in background.

Usage: hanoi.py [n [bitmapfile]]

n is the number of pieces to animate; default is 4, maximum 15.

The bitmap file can be any X11 bitmap file (look in /usr/include/X11/bitmaps for
samples); it is displayed as the background of the animation. Default is no
bitmap.
"""

from tkinter import Tk, Canvas

# Basic Towers-of-Hanoi algorithm: move n pieces from a to b, using c
# as temporary. For each move, call report()
def hanoi(n, a, b, c, report):
 if n <= 0: return
 hanoi(n-1, a, c, b, report)
 report(n, a, b)
 hanoi(n-1, c, b, a, report)


# The graphical interface
class Tkhanoi:

 # Create our objects
 def __init__(self, n, bitmap = None):
 self.n = n
 self.tk = tk = Tk()
 self.canvas = c = Canvas(tk)
 c.pack()
 width, height = tk.getint(c['width']), tk.getint(c['height'])

 # Add background bitmap
 if bitmap:
 self.bitmap = c.create_bitmap(width//2, height//2,
 bitmap=bitmap,
 foreground='blue')

 # Generate pegs
 pegwidth = 10
 pegheight = height//2
 pegdist = width//3
 x1, y1 = (pegdist-pegwidth)//2, height*1//3
 x2, y2 = x1+pegwidth, y1+pegheight
 self.pegs = []
 p = c.create_rectangle(x1, y1, x2, y2, fill='black')
 self.pegs.append(p)
 x1, x2 = x1+pegdist, x2+pegdist
 p = c.create_rectangle(x1, y1, x2, y2, fill='black')
 self.pegs.append(p)
 x1, x2 = x1+pegdist, x2+pegdist
 p = c.create_rectangle(x1, y1, x2, y2, fill='black')
 self.pegs.append(p)
 self.tk.update()

 # Generate pieces
 pieceheight = pegheight//16
 maxpiecewidth = pegdist*2//3
 minpiecewidth = 2*pegwidth
 self.pegstate = [[], [], []]
 self.pieces = {}
 x1, y1 = (pegdist-maxpiecewidth)//2, y2-pieceheight-2
 x2, y2 = x1+maxpiecewidth, y1+pieceheight
 dx = (maxpiecewidth-minpiecewidth) // (2*max(1, n-1))
 for i in range(n, 0, -1):
 p = c.create_rectangle(x1, y1, x2, y2, fill='red')
 self.pieces[i] = p
 self.pegstate[0].append(i)
 x1, x2 = x1 + dx, x2-dx
 y1, y2 = y1 - pieceheight-2, y2-pieceheight-2
 self.tk.update()
 self.tk.after(25)

 # Run -- never returns
 def run(self):
 while 1:
 hanoi(self.n, 0, 1, 2, self.report)
 hanoi(self.n, 1, 2, 0, self.report)
 hanoi(self.n, 2, 0, 1, self.report)
 hanoi(self.n, 0, 2, 1, self.report)
 hanoi(self.n, 2, 1, 0, self.report)
 hanoi(self.n, 1, 0, 2, self.report)

 # Reporting callback for the actual hanoi function
 def report(self, i, a, b):
 if self.pegstate[a][-1] != i: raise RuntimeError # Assertion
 del self.pegstate[a][-1]
 p = self.pieces[i]
 c = self.canvas

 # Lift the piece above peg a
 ax1, ay1, ax2, ay2 = c.bbox(self.pegs[a])
 while 1:
 x1, y1, x2, y2 = c.bbox(p)
 if y2 < ay1: break
 c.move(p, 0, -1)
 self.tk.update()

 # Move it towards peg b
 bx1, by1, bx2, by2 = c.bbox(self.pegs[b])
 newcenter = (bx1+bx2)//2
 while 1:
 x1, y1, x2, y2 = c.bbox(p)
 center = (x1+x2)//2
 if center == newcenter: break
 if center > newcenter: c.move(p, -1, 0)
 else: c.move(p, 1, 0)
 self.tk.update()

 # Move it down on top of the previous piece
 pieceheight = y2-y1
 newbottom = by2 - pieceheight*len(self.pegstate[b]) - 2
 while 1:
 x1, y1, x2, y2 = c.bbox(p)
 if y2 >= newbottom: break
 c.move(p, 0, 1)
 self.tk.update()

 # Update peg state
 self.pegstate[b].append(i)


def main():
 import sys

 # First argument is number of pegs, default 4
 if sys.argv[1:]:
 n = int(sys.argv[1])
 else:
 n = 4

 # Second argument is bitmap file, default none
 if sys.argv[2:]:
 bitmap = sys.argv[2]
 # Reverse meaning of leading '@' compared to Tk
 if bitmap[0] == '@': bitmap = bitmap[1:]
 else: bitmap = '@' + bitmap
 else:
 bitmap = None

 # Create the graphical objects...
 h = Tkhanoi(n, bitmap)

 # ...and run!
 h.run()


# Call main when run as script
if __name__ == '__main__':
 main()