#!/usr/bin/env perl

=pod

=head1 NAME

generatetriads - generates all letter groups of a given size

=head1 SYNOPSIS

  generatetriads [-n GROUPSIZE]

=head1 DESCRIPTION

Generates all combinations of GROUPSIZE letters.

=head1 OPTIONS

=head2 -n GROUPSIZE

Set the number of letters with -n. By default, n=3 (triads).

=head1 AUTHOR

Martin Krzywinski

=head1 CONTACT

  Martin Krzywinski
  Genome Sciences Centre
  Vancouver BC Canada
  www.bcgsc.ca
  martink@bcgsc.ca

=cut

################################################################
#
# Copyright 2002-2008 Martin Krzywinski <martink@bcgsc.ca>
#
# This file is part of the Genome Sciences Centre Perl code base.
#
# This script is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This script is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this script; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
################################################################

use strict;
use Config::General;
use Data::Dumper;
use File::Basename;
use FindBin;
use Getopt::Long;
use IO::File;
use Math::VecStat qw(sum min max average);
use Math::Combinatorics;
use Pod::Usage;
use Storable;
use Time::HiRes qw(gettimeofday tv_interval);
use lib "$FindBin::RealBin";
use lib "$FindBin::RealBin/../lib";
use lib "$FindBin::RealBin/lib";
use vars qw(%OPT %CONF);

################################################################
#
# *** YOUR MODULE IMPORTS HERE
#
################################################################

GetOptions(\%OPT,
	   "n=i",
	   "configfile=s","help","man","debug+");

pod2usage() if $OPT{help};
pod2usage(-verbose=>2) if $OPT{man};
loadconfiguration($OPT{configfile});
populateconfiguration(); # copy command line options to config hash
validateconfiguration(); 
if($CONF{debug} > 1) {
  $Data::Dumper::Pad = "debug parameters";
  $Data::Dumper::Indent = 1;
  $Data::Dumper::Quotekeys = 0;
  $Data::Dumper::Terse = 1;
  print Dumper(\%CONF);
}

my @c = ("a".."z");
my $n = @c ** $CONF{n};
for my $i (0..$n-1) {
  my @group;
  for my $j (0..$CONF{n}-1) {
    my $r = $i/@c**$j % @c;
    push @group, $r;
  }
  printinfo( join("",@c[reverse @group]) );
}

sub validateconfiguration {
  $CONF{n} ||= 3;
}

################################################################
#
# *** DO NOT EDIT BELOW THIS LINE ***
#
################################################################

sub populateconfiguration {
  foreach my $key (keys %OPT) {
    $CONF{$key} = $OPT{$key};
  }

  # any configuration fields of the form __XXX__ are parsed and replaced with eval(XXX). The configuration
  # can therefore depend on itself.
  #
  # flag = 10
  # note = __2*$CONF{flag}__ # would become 2*10 = 20

  for my $key (keys %CONF) {
    my $value = $CONF{$key};
    while($value =~ /__([^_].+?)__/g) {
      my $source = "__" . $1 . "__";
      my $target = eval $1;
      $value =~ s/\Q$source\E/$target/g;
      #printinfo($source,$target,$value);
    }
    $CONF{$key} = $value;
  }

}

sub loadconfiguration {
  my $file = shift;
  my ($scriptname) = fileparse($0);
  if(-e $file && -r _) {
    # great the file exists
  } elsif (-e "/home/$ENV{LOGNAME}/.$scriptname.conf" && -r _) {
    $file = "/home/$ENV{LOGNAME}/.$scriptname.conf";
  } elsif (-e "$FindBin::RealBin/$scriptname.conf" && -r _) {
    $file = "$FindBin::RealBin/$scriptname.conf";
  } elsif (-e "$FindBin::RealBin/etc/$scriptname.conf" && -r _) {
    $file = "$FindBin::RealBin/etc/$scriptname.conf";
  } elsif (-e "$FindBin::RealBin/../etc/$scriptname.conf" && -r _) {
    $file = "$FindBin::RealBin/../etc/$scriptname.conf";
  } else {
    return undef;
  }
  $OPT{configfile} = $file;
  my $conf = new Config::General(-ConfigFile=>$file,
				 -AllowMultiOptions=>"yes",
				 -LowerCaseNames=>1,
				 -AutoTrue=>1);
  %CONF = $conf->getall;
}

sub printdebug {
  printinfo("debug",@_)  if $CONF{debug};
}

sub printinfo {
  printf("%s\n",join(" ",@_));
}