#!/usr/bin/env python
#================================================================
# Sudoku puzzle solver.  For documentation, see:
#   http://www.nmt.edu/tcc/help/lang/python/sudoku/
#----------------------------------------------------------------
#================================================================
# Imports
#----------------------------------------------------------------

import sys
import time
import sudosolver
# - - -   m a i n   - - -

def main():
    """sudoku main program
    """

    #-- 1 --
    argList  =  sys.argv[1:]

    #-- 2 --
    # [ if argList is empty ->
    #     sys.stderr  +:=  error message
    #   else ->
    #     sys.stdout  +:=  solutions to valid puzzles named in
    #         argList
    #     sys.stderr  +:=  error messages about invalid puzzles
    #         named in argList ]
    if  len(argList) == 0:
        message ( "*** You must supply names of "
            "at least one sudoku puzzle file.\n" )
    else:
        for  arg in argList:
            solveFile ( arg )
# - - -   m e s s a g e   - - -

def message ( * L ):
    """Write a message to sys.stderr.

      [ L is a list of strings ->
          sys.stderr  +:=  concatenation of L ]
    """
    sys.stderr.write ( "*** %s\n" % "".join(L) )
# - - -   f a t a l   - - -

def fatal ( *L ):
    """Write a message and terminate.

      [ L is a list of strings ->
          sys.stderr  +:=  concatenation of L
          stop execution ]
    """
    message ( *L )
    sys.exit(1)
# - - -   s o l v e F i l e   - - -

def solveFile ( fileName ):
    """Try to solve one puzzle.

      [ fileName is a string ->
          if fileName names a readable, valid sudoku puzzle
          file ->
            sys.stdout  +:=  solution(s) to that puzzle if any
            sys.stderr  +:=  message if there are no solutions
          else ->
            sys.stderr  +:=  error message about a bad puzzle ]
    """
    #-- 1 --
    # [ if fileName names a readable file ->
    #     rawPuzzle  :=  contents of that file
    #   else ->
    #     sys.stderr  +:=  error message
    #     return ]
    try:
        inFile  =  open ( fileName )
        rawPuzzle  =  inFile.read()
    except IOError, detail:
        message ( "*** Can't open file '%s' for reading. %s\n" %
                (fileName, detail) )
        return
    #-- 2 --
    # [ if rawPuzzle is a valid sudoku puzzle ->
    #     solver  :=  an instance of SudokuSolver to solve
    #         rawPuzzle that will call solutionFound when it
    #         finds a solution
    #   else ->
    #     sys.stderr  +:=  error message
    #     return ] 
    try:
        solver  =  sudosolver.SudokuSolver ( rawPuzzle, solutionFound )
    except ValueError, detail:
        message ( "Invalid puzzle: %s" % detail )
        return
    #-- 3 --
    # [ sys.stdout  +:=  (fileName) + (puzzle in its initial
    #                    state ]
    separator  =  "=" * 9
    print "\n%s %s %s" % (separator, fileName, separator)
    solver.write ( sys.stdout )
    #-- 4 --
    # [ sys.stdout  +:=  solutions to solver, if any ]
    startClock  =  time.clock()
    solver.solve()
    endClock  =  time.clock()
    #-- 5 --
    # [ sys.stdout  +:=  report on the number of solutions in
    #                    solver ]
    print "\nNumber of solutions found:", solver.nSolutions
    print "Elapsed cpu time: %.2f seconds." % (endClock-startClock)
# - - -   s o l u t i o n F o u n d   - - -

def solutionFound ( solver ):
    """Report a successful solution of the puzzle.

      [ sys.stdout  +:=  display of the state of solver ]
    """
    print "\n--- Solution #%d:" % solver.nSolutions
    solver.write ( sys.stdout )
#================================================================
# Epilogue
#----------------------------------------------------------------

if __name__ == "__main__":
    main()