#!/usr/bin/perl
use strict;
use warnings;
use Bit::Vector::Overload;
use Graph::UnionFind;

# Insert real data here.
my %items = (
    a => [ qw/one six/ ],
    b => [ qw/two three five/ ],
    c => [ qw/one two five/ ],
);
my $icount = keys %items;
print "Doing $icount items\n";

# Assign an index position to each item.
# Form a mapping from items to bit positions.
# Collect a list of bitmaps for combination work.
my @revipos;
my %ipos;
my @ilst;
my $ix = 0;
for my $itm ( sort keys %items ) {
   $ipos{$itm} = $ix;
   push @revipos,$itm;
   my $set1 = new Bit::Vector($icount + 1);
   $set1->Bit_On($ix);
   push @ilst, $set1;
   ++$ix;
}

# Form a mapping from keywords to bit positions.
my $scount = 0;
my @revkpos;
my %kpos;
for my $itm ( @revipos ) {
   for my $keyw ( @{ $items{ $itm }} ) {
      if (!exists $kpos{$keyw}) {
         $kpos{$keyw} = $scount++;
         push @revkpos, $keyw;
      }
   }
}
# Also form a reverse index for later printing.
#my %revkpos = reverse(%kpos);

my $uf = Graph::UnionFind->new;
# Supplemental data to look up by union number.
my %union_data;

# Form bit vectors with ones in the keyword positions,
# one for every item.
my %keyword_vecs;
my @lst1;
my $i = 0;
for my $itm ( @revipos ) {
   #print "doing item $i\n";
   my $set0 = new Bit::Vector($scount + 1);
   $keyword_vecs{$itm} = $set0;
   for my $keyw ( @{ $items{ $itm }} ) {
      $set0->Bit_On($kpos{$keyw});
   }

   # hold both sets - items and keywords together.
   #push @lst1,[$ilst[$ipos{$itm}], $set0];

   # unionfind to detect partitions.
   $uf->add($i);

   my $unioned = 0;
   my @ukeys = keys %union_data;
   for my $uk (@ukeys) {
      my $partu = $uf->find($uk);
      if ($uk != $partu) {
         delete $union_data{$uk};
      }
      if ($set0 & $union_data{$partu}) {
         $unioned = 1;
         $uf->union( $i, $partu);
         my $parti = $uf->find( $i );
         my $newset = $set0 | $union_data{$partu};
         delete $union_data{$partu} if ($partu != $parti);
         $union_data{$parti} = $newset;
      }
   }
   $union_data{$i} = $set0 if (!$unioned);
   
   ++$i;
}
print "Expecting ",scalar(keys %union_data)," partitions\n";

my @parts;
my %unique_parts;
my $pcount = 0;
for $i (0 .. $#revipos) {
   my $parti =  $uf->find( $i );
   if (!exists $unique_parts{$parti}) {
      $unique_parts{$parti} = $pcount;
      push @{ $parts[$pcount] }, $i;
      $pcount++;
   } else {
      push @{ $parts[ $unique_parts{$parti} ] }, $i;
   }
}
print "Found $pcount partitions\n";
for $i (0 .. $#parts) {
   print scalar( @{ $parts[$i] })," items in partition $i\n";
}