#!/usr/bin/env python

import os, random

def readpuzzle():
  "Returns a random puzzle from Gordon Royle's list of minimum sudoku."
  filename = '/home/davidbau/public_html/sudoku/sudoku17'
  desc = file(filename)
  linelen = len(desc.readline()) or 82
  filesize = os.stat(filename)[6]
  desc.seek(random.randrange(filesize // linelen) * linelen)
  line = desc.readline()
  while len(line) != linelen:
    line = desc.readline()
  return [int(x) for x in line.strip()]

def blockrandom():
  "Returns a random permutation of range(8) keeping blocks of 3 together."
  o = random.sample([random.sample(x, 3)
    for x in [[0,1,2], [3,4,5], [6,7,8]]], 3)
  return [item for sublist in o for item in sublist]

def permuted(puzzle):
  "Returns a randomly permuted equivalent puzzle."
  rows, cols = blockrandom(), blockrandom()
  puzzle = [puzzle[cols[x] + 9 * rows[y]]
            for x in xrange(9) for y in xrange(9)]
  if random.randint(0, 1):
    puzzle = [puzzle[y + x * 9] for x in xrange(9) for y in xrange(9)]
  return puzzle

def substituted(puzzle):
  "Returns a equivalent puzzle with randomly substituted numbers."
  num = [0] + random.sample(xrange(1, 10), 9)
  return [num[puzzle[x]] for x in xrange(len(puzzle))]
  
puzzlestring = ''.join([str(n) for n in substituted(permuted(readpuzzle()))])
pathinfo = os.getenv('REQUEST_URI') or ''
pdf = pathinfo.endswith('pdf')

if pdf:
  print "Location: http://davidbau.com/generated/sudoku.pdf?" + puzzlestring
else:
  print "Location: http://davidbau.com/sudoku/#" + puzzlestring

print