source: gsdl/trunk/perllib/classify/AZCompactList.pm@ 17209

###########################################################################
#
# AZCompactList.pm --
# A component of the Greenstone digital library software
# from the New Zealand Digital Library Project at the 
# University of Waikato, New Zealand.
#
# Copyright (C) 1999 New Zealand Digital Library Project
#
# This program 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 program 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 program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
###########################################################################
# classifier plugin for sorting alphabetically

package AZCompactList;

use BaseClassifier;
use sorttools;

use strict;
no strict 'refs'; # allow filehandles to be variables and viceversa

sub BEGIN {
    @AZCompactList::ISA = ('BaseClassifier');
}

my $doclevel_list = 
    [ { 'name' => "top",
    'desc' => "{AZCompactList.doclevel.top}" },
      { 'name' => "section",
    'desc' => "{AZCompactList.doclevel.section}" } ];

my $arguments = 
    [ { 'name' => "metadata",
    'desc' => "{AZCompactList.metadata}",
    'type' => "metadata",
    'reqd' => "yes" },
      { 'name' => "firstvalueonly",
    'desc' => "{AZCompactList.firstvalueonly}",
    'type' => "flag",
    'reqd' => "no" },
      { 'name' => "allvalues",
    'desc' => "{AZCompactList.allvalues}",
    'type' => "flag",
    'reqd' => "no" },
      { 'name' => "sort",
    'desc' => "{AZCompactList.sort}",
    'type' => "metadata",
#   'deft' => "Title",
    'reqd' => "no" },
      { 'name' => "removeprefix",
    'desc' => "{BasClas.removeprefix}",
    'type' => "regexp",
    'deft' => "",
    'reqd' => "no" },
      { 'name' => "removesuffix",
    'desc' => "{BasClas.removesuffix}",
    'type' => "regexp",
    'deft' => "",
    'reqd' => "no" },
      { 'name' => "mingroup",
    'desc' => "{AZCompactList.mingroup}",
    'type' => "int",
    'deft' => "1",
    'range' => "1,",
    'reqd' => "no" },
      { 'name' => "minnesting",
    'desc' => "{AZCompactList.minnesting}",
    'type' => "int",
    'deft' => "20",
    'range' => "2,",
    'reqd' => "no" },
      { 'name' => "mincompact",
    'desc' => "{AZCompactList.mincompact}",
    'type' => "int",
    'deft' => "10",
    'range' => "1,",
    'reqd' => "no" },
      { 'name' => "maxcompact",
    'desc' => "{AZCompactList.maxcompact}",
    'type' => "int",
    'deft' => "30",
    'range' => "1,",
    'reqd' => "no" },
      { 'name' => "doclevel",
    'desc' => "{AZCompactList.doclevel}",
    'type' => "enum",
    'list' => $doclevel_list,
    'deft' => "top",
    'reqd' => "no" },
      { 'name' => "freqsort",
    'desc' => "{AZCompactList.freqsort}",
    'type' => "flag"},
      { 'name' => "recopt",
    'desc' => "{AZCompactList.recopt}",
    'type' => "flag",
    'reqd' => "no" } ];

my $options = 
{   'name'     => "AZCompactList",
    'desc'     => "{AZCompactList.desc}",
    'abstract' => "no",
    'inherits' => "yes",
    'args'     => $arguments };


sub new {
    my ($class) = shift (@_);
    my ($pluginlist,$inputargs,$hashArgOptLists) = @_;
    push(@$pluginlist, $class);

    push(@{$hashArgOptLists->{"ArgList"}},@{$arguments});
    push(@{$hashArgOptLists->{"OptList"}},$options);

    my $self = new BaseClassifier($pluginlist, $inputargs, $hashArgOptLists);

    if ($self->{'info_only'}) {
    # don't worry about any options etc
    return bless $self, $class;
    }
    
    if (!$self->{"metadata"}) {
    my $outhandle = $self->{'outhandle'};
    print $outhandle "AZCompactList Error: required option -metadata not supplied\n";
    $self->print_txt_usage("");  
    die "AZCompactList Error: required option -metadata not supplied\n";
    }

    # Manually set $self parameters.
    $self->{'list'} = {};
    $self->{'listmetavalue'} = {};
    $self->{'list_mvpair'} = {};
    $self->{'reclassify'} = {};
    $self->{'reclassifylist'} = {};

    $self->{'buttonname'} = $self->generate_title_from_metadata($self->{'metadata'}) unless ($self->{'buttonname'});
    
    if (defined($self->{"removeprefix"}) && $self->{"removeprefix"}) {
    $self->{"removeprefix"} =~ s/^\^//; # don't need a leading ^
    }
    if (defined($self->{"removesuffix"}) && $self->{"removesuffix"}) {
    $self->{"removesuffix"} =~ s/\$$//; # don't need a trailing $
    }
    
    $self->{'recopt'} = ($self->{'recopt'} == 0) ? undef : "on";

    # Clean out the unused keys
    if($self->{"removeprefix"} eq "") {delete $self->{"removeprefix"};}
    if($self->{"removesuffix"} eq "") {delete $self->{"removesuffix"};}

    return bless $self, $class;
}

sub init 
{
    my $self = shift (@_);
    
    $self->{'list'} = {};
    $self->{'listmetavalue'} = {};
    $self->{'list_mvpair'} = {};
    $self->{'reclassify'} = {};
    $self->{'reclassifylist'} = {};
}

my $tmp = 0;

sub classify
{
    my $self = shift (@_);
    my ($doc_obj) = @_;

    my $doc_OID = $doc_obj->get_OID();

    my @sectionlist = ();
    my $topsection = $doc_obj->get_top_section();
    my $metaname = $self->{'metadata'};
    my $outhandle = $self->{'outhandle'};

    $metaname =~ s/(\/|\|).*//; # grab first name in n1/n2/n3 or n1|n2|n3 list
    my @commameta_list = split(/,/, $metaname);

    if ($self->{'doclevel'} =~ /^top(level)?/i)
    {
    push(@sectionlist,$topsection);
    }
    else
    {
    my $thissection = $doc_obj->get_next_section($topsection);
    while (defined $thissection) 
    {
        push(@sectionlist,$thissection);
        $thissection = $doc_obj->get_next_section ($thissection);
    }
    }

    my $thissection;
    foreach $thissection (@sectionlist)
    {
    my $full_doc_OID 
        = ($thissection ne "") ? "$doc_OID.$thissection" : $doc_OID;
    if (defined $self->{'list_mvpair'}->{$full_doc_OID}) 
    {
        print $outhandle "WARNING: AZCompactList::classify called multiple times for $full_doc_OID\n";
    } 
    $self->{'list'}->{$full_doc_OID} = [];  
    $self->{'listmetavalue'}->{$full_doc_OID} = [];
    $self->{'list_mvpair'}->{$full_doc_OID} = [];

    my $metavalues = [];
    foreach my $cmn (@commameta_list) {
        my $cmvalues = $doc_obj->get_metadata($thissection,$cmn);
        push(@$metavalues,@$cmvalues) if (@{$cmvalues});
        last if (@{$cmvalues} && !$self->{'allvalues'});
    }

    my $metavalue;
    foreach $metavalue (@$metavalues) 
    {
        # Tidy up use of white space in metavalue for classifying
        $metavalue =~ s/^\s*//s;
        $metavalue =~ s/\s*$//s;
        $metavalue =~ s/\n/ /s;
        $metavalue =~ s/\s{2,}/ /s;

        # if this document doesn't contain the metadata element we're
        # sorting by we won't include it in this classification
        if (defined $metavalue && $metavalue =~ /\w/) 
        {
        if (defined($self->{'removeprefix'}) &&
            length($self->{'removeprefix'})) {
            $metavalue =~ s/^$self->{'removeprefix'}//;

            # check that it's not now empty
            if (!$metavalue) {next;}
        }

        if (defined($self->{'removesuffix'}) &&
            length($self->{'removesuffix'})) {
            $metavalue =~ s/$self->{'removesuffix'}$//;

            # check that it's not now empty
            if (!$metavalue) {next;}
        }

        my $formatted_metavalue;
        if ($self->{'no_metadata_formatting'}) {
            $formatted_metavalue = $metavalue;
        } else {
            $formatted_metavalue = &sorttools::format_metadata_for_sorting($self->{'metadata'},  $metavalue, $doc_obj);
        }
        
        #### prefix-str
        if (! defined($formatted_metavalue)) {
            print $outhandle "Warning: AZCompactList: metavalue is ";
            print $outhandle "empty\n";
            $formatted_metavalue="";
        }

        my $mv_pair = { 'mv' => $metavalue, 'fmv' => $formatted_metavalue };
        push(@{$self->{'list'}->{$full_doc_OID}},$formatted_metavalue);
        push(@{$self->{'listmetavalue'}->{$full_doc_OID}} ,$metavalue);
        push(@{$self->{'list_mvpair'}->{$full_doc_OID}},$mv_pair);


        last if ($self->{'firstvalueonly'});
        }
    }

    # This is used in reclassify below for AZCompactSectionList
    my $sortmeta = $doc_obj->get_metadata_element($thissection, $self->{'sort'});
    $self->{'reclassify'}->{$full_doc_OID} = [$doc_obj,$sortmeta];
    }
}

sub reinit 
{
    my ($self,$classlist_ref) = @_;
    my $outhandle = $self->{'outhandle'};
    
    my %mtfreq = ();
    my @single_classlist = ();
    my @multiple_classlist = ();

    # find out how often each metavalue occurs
    map 
    { 
    foreach my $mvp (@{$self->{'list_mvpair'}->{$_}} )
    {
###     print STDERR "*** plain mv = $mvp->{'mv'}\n";
###     print STDERR "*** format mv = $mvp->{'fmv'}\n";

        my $metavalue = $mvp->{'mv'};
        $metavalue =~ s!^-!\\-!; # in case it starts with "-"
        $mtfreq{$metavalue}++;
    }
    } @$classlist_ref;

    # use this information to split the list: single metavalue/repeated value
    map
    { 
    my $i = 1;
    my $metavalue;
    foreach my $mvp (@{$self->{'list_mvpair'}->{$_}})
    {
        my $metavalue = $mvp->{'mv'};
        $metavalue =~ s!^-!\\-!; # in case it starts with "-"
        my $cs_metavalue = $mvp->{'mv'}; # case sensative
        if ($mtfreq{$metavalue} >= $self->{'mingroup'})
        {
###     print STDERR "*** pushing on $cs_metavalue\n";
        push(@multiple_classlist,[$_,$i,$metavalue]); 
        } 
        else
        {
        push(@single_classlist,[$_,$cs_metavalue]); 
        $metavalue =~ tr/[A-Z]/[a-z]/;
        $self->{'reclassifylist'}->{"Metavalue_$i.$_"} = $metavalue;
        }
        $i++;
    }
    } @$classlist_ref;
    
    
    # Setup sub-classifiers for multiple list

    $self->{'classifiers'} = {};

    my $pm;
    foreach $pm ("List", "SectionList")
    {
    my $listname 
        = &util::filename_cat($ENV{'GSDLHOME'},"perllib/classify/$pm.pm");
    if (-e $listname) { require $listname; }
    else 
    { 
        print $outhandle "AZCompactList ERROR - couldn't find classifier \"$listname\"\n"; 
        die "\n";
    }
    }

    # Create classifiers objects for each entry >= mingroup
    my $metavalue;
    my $doclevel = $self->{'doclevel'};
    my $mingroup = $self->{'mingroup'};
    my @metaname_list = split(/\/|\|/,$self->{'metadata'});
    my $metaname = shift(@metaname_list);
    my $hierarchical = 0;
    if (scalar(@metaname_list) > 1) {
    $hierarchical = 1;
    $metaname = join('/',@metaname_list);
    }
    foreach $metavalue (keys %mtfreq)
    {
    if ($mtfreq{$metavalue} >= $mingroup)
    {
        # occurs more often than minimum required to compact into a group
        my $listclassobj;
        
        if (!$hierarchical) 
        {   
        my @args;
        push @args, ("-metadata", "$metaname");
        # buttonname is also used for the node's title
        push @args, ("-buttonname", "$metavalue");
        push @args, ("-sort", $self->{'sort'});

        my $ptArgs = \@args;
        if ($doclevel =~ m/^top(level)?/i)
        {
            eval ("\$listclassobj = new List([],\$ptArgs)"); 
        }
        else
        {
            eval ("\$listclassobj = new SectionList([],\$ptArgs)");
        }
        }
        else
        {
        
        my @args;
        push @args, ("-metadata", "$metaname");
        # buttonname is also used for the node's title
        push @args, ("-buttonname", "$metavalue");
        push @args, ("-sort", $self->{'sort'});

        if (defined $self->{'removeprefix'}) {
            push @args, ("-removeprefix", $self->{'removeprefix'});
        }
        if (defined $self->{'removesuffix'}) {
            push @args, ("-removesuffix", $self->{'removesuffix'});
        }
        
        push @args, ("-doclevel", "$doclevel");
        push @args, ("-mingroup", $mingroup);
        push @args, "-recopt ";

        my $ptArgs = \@args;
        eval ("\$listclassobj = new AZCompactList([],\$ptArgs)");
        }
        
        if ($@) {
        print $outhandle "$@";
        die "\n";
        }
        
        $listclassobj->init();

        if (defined $metavalue && $metavalue =~ /\w/) 
        {
        my $formatted_node = $metavalue;

        if (defined($self->{'removeprefix'}) &&
            length($self->{'removeprefix'})) {
            $formatted_node =~ s/^$self->{'removeprefix'}//;
            # check that it's not now empty
            if (!$formatted_node) {next;}
        }
        if (defined($self->{'removesuffix'}) &&
            length($self->{'removesuffix'})) {
            $formatted_node =~ s/$self->{'removesuffix'}$//;
            # check that it's not now empty
            if (!$formatted_node) {next;}
        }

        $formatted_node = &sorttools::format_metadata_for_sorting($self->{'metadata'}, $formatted_node) unless $self->{'no_metadata_formatting'};

        # In case our formatted string is empty...
        if (! defined($formatted_node)) {
            print $outhandle "Warning: AZCompactList: metavalue is ";
            print $outhandle "empty\n";
            $formatted_node="";
        }

        # use the lower case, for speed of lookup.
        my $meta_lc=lc($metavalue);
        $self->{'classifiers'}->{$meta_lc}
        = { 'classifyobj'   => $listclassobj,
            'formattednode' => $formatted_node };
        }
    }
    }


    return (\@single_classlist,\@multiple_classlist);
}


sub reclassify 
{
    my ($self,$multiple_cl_ref) = @_;

    # Entries in the current classify list that are "book nodes"
    # should be recursively classified.
    #--
    foreach my $dm_pair (@$multiple_cl_ref) 
    {
    my ($doc_OID,$mdoffset,$metavalue,$cs_metavalue) = @$dm_pair;
        my $listclassobj;

    # find metavalue in list of sub-classifiers
    # check if we have a key (lower case) for this metadata value
    my $node_name=lc($metavalue);
    if (exists $self->{'classifiers'}->{$node_name})
    {
        my ($doc_obj, $sortmeta) = @{$self->{'reclassify'}->{$doc_OID}};

        # record the metadata value offset temporarily, so eg AZList can
        # get the correct metadata value (for multi-valued metadata fields)
        $doc_obj->{'mdoffset'}=$mdoffset;

        if ($doc_OID =~ m/^[^\.]*\.([\d\.]+)$/)
        {
        my $section=$1;
        if ($self->{'doclevel'} =~ m/^top/i) { # toplevel
            $self->{'classifiers'}->{$node_name}->{'classifyobj'}
            ->classify($doc_obj, "Section=$section");
        } else { # section level
            # Thanks to Don Gourley for this...
            # classify can't handle multi-level section
            $self->{'classifiers'}->{$node_name}->{'classifyobj'}
            ->classify_section($section, $doc_obj, $sortmeta);
        }
        }
        else
        {
        $self->{'classifiers'}->{$node_name}->{'classifyobj'}
        ->classify($doc_obj); 
        }
    } else { # this key is not in the hash
        my $outhandle=$self->{outhandle};
        print $outhandle "Warning: AZCompactList::reclassify ";
        print $outhandle "could not find sub-node for metadata=`$metavalue' with doc_OID $doc_OID\n";
    }
    }
}



sub get_reclassify_info 
{
    my $self = shift (@_);
    
    my $node_name;
    foreach $node_name (keys %{$self->{'classifiers'}}) 
    {
        my $classifyinfo 
        = $self->{'classifiers'}->{$node_name}->{'classifyobj'}
            ->get_classify_info();
        $self->{'classifiers'}->{$node_name}->{'classifyinfo'} 
        = $classifyinfo;
        $self->{'reclassifylist'}->{"CLASSIFY.$node_name"} 
        = $self->{'classifiers'}->{$node_name}->{'formattednode'};
    }
}


sub alpha_numeric_cmp
{
    my ($self,$a,$b) = @_;

    my $title_a = $self->{'reclassifylist'}->{$a};
    my $title_b = $self->{'reclassifylist'}->{$b};
    
    if ($title_a =~ m/^(\d+(\.\d+)?)/)
    {
    my $val_a = $1;
    if ($title_b =~ m/^(\d+(\.\d+)?)/)
    {
        my $val_b = $1;
        if ($val_a != $val_b)
        {
        return ($val_a <=> $val_b);
        }
    }
    }
    
    return ($title_a cmp $title_b);
}

sub frequency_cmp
{
    my ($self,$a,$b) = @_;


    my $title_a = $self->{'reclassifylist'}->{$a};
    my $title_b = $self->{'reclassifylist'}->{$b};

    my $a_freq = 1;
    my $b_freq = 1;

    if ($a =~ m/^CLASSIFY\.(.*)$/)
    {
    my $a_node = $1;
    my $a_nodeinfo = $self->{'classifiers'}->{$a_node}->{'classifyinfo'};
    $a_freq = scalar(@{$a_nodeinfo->{'contains'}});
    }
    
    if ($b =~ m/^CLASSIFY\.(.*)$/)
    {
    my $b_node = $1;
    my $b_nodeinfo = $self->{'classifiers'}->{$b_node}->{'classifyinfo'};
    $b_freq = scalar(@{$b_nodeinfo->{'contains'}});
    }

    return $b_freq <=> $a_freq;
}

sub get_classify_info {
    my $self = shift (@_);

    my @classlist =keys %{$self->{'list_mvpair'}}; # list all doc oids

    my ($single_cl_ref,$multiple_cl_ref) = $self->reinit(\@classlist);
    $self->reclassify($multiple_cl_ref);
    $self->get_reclassify_info();

    my @reclassified_classlist;
    if ($self->{'freqsort'})
    {
    @reclassified_classlist 
        = sort { $self->frequency_cmp($a,$b) } keys %{$self->{'reclassifylist'}};
    # supress sub-grouping by alphabet
    map { $self->{'reclassifylist'}->{$_} = "A".$self->{'reclassifylist'}; } keys %{$self->{'reclassifylist'}};
    }
    else
    {
#   @reclassified_classlist 
#       = sort {$self->{'reclassifylist'}->{$a} cmp $self->{'reclassifylist'}->{$b};} keys %{$self->{'reclassifylist'}};

    # alpha_numeric_cmp is slower than "cmp" but handles numbers better ...

    @reclassified_classlist
        = sort { $self->alpha_numeric_cmp($a,$b) } keys %{$self->{'reclassifylist'}};

    }

    return $self->splitlist (\@reclassified_classlist);
}

sub get_entry {
    my $self = shift (@_);
    my ($title, $childtype, $metaname, $thistype) = @_;
    # organise into classification structure
    my %classifyinfo = ('childtype'=>$childtype,
                        'Title'=>$title,
                        'contains'=>[],
            'mdtype'=>$metaname);

    $classifyinfo{'thistype'} = $thistype
        if defined $thistype && $thistype =~ /\w/;

    return \%classifyinfo;
}



# splitlist takes an ordered list of classifications (@$classlistref) and 
# splits it up into alphabetical sub-sections.
sub splitlist {
    my $self = shift (@_);
    my ($classlistref) = @_;
    my $classhash = {};

    # top level
    my @metanames = split(/\/|\|/,$self->{'metadata'});
    my $metaname = shift(@metanames);

    my $childtype = "HList";
    $childtype = "VList" if (scalar (@$classlistref) <= $self->{'minnesting'});

    my $title = $self->{'buttonname'}; # should always be defined by now.
    my $classifyinfo;
    if (!defined($self->{'recopt'}))
    {
    $classifyinfo 
        = $self->get_entry ($title, $childtype, $metaname, "Invisible");
    }
    else
    {
    $classifyinfo 
        = $self->get_entry ($title, $childtype, $metaname, "VList");
    }

    # don't need to do any splitting if there are less than 'minnesting' classifications
    if ((scalar @$classlistref) <= $self->{'minnesting'}) {
    foreach my $subOID (@$classlistref) {
            if ($subOID =~ /^CLASSIFY\.(.*)$/ 
        && defined $self->{'classifiers'}->{$1}) 
        {
                push (@{$classifyinfo->{'contains'}}, 
              $self->{'classifiers'}->{$1}->{'classifyinfo'});
            } 
        else 
        {
        $subOID =~ s/^Metavalue_(\d+)\.//;
        my $metaname_offset = $1 -1;
        my $oid_rec = {'OID'=>$subOID, 'offset'=>$metaname_offset};
        push (@{$classifyinfo->{'contains'}}, $oid_rec);
        }
    }
    return $classifyinfo;
    }
    
    # first split up the list into separate A-Z and 0-9 classifications
    foreach my $classification (@$classlistref) {
    my $title = $self->{'reclassifylist'}->{$classification};
    $title =~ s/&(.){2,4};//g; # remove any HTML special chars
    $title =~ s/^\W+//g; # remove leading non-word chars

    # only want first character for classification
    $title =~ m/^(.)/; # always a char, or first byte of wide char?
    if (defined($1) && $1 ne "") {
        $title=$1;
    } else {
        print STDERR "no first character found for \"$title\" - \"" .
        $self->{'reclassifylist'}->{$classification} . "\"\n";
    }
    $title =~ tr/[a-z]/[A-Z]/;

    if ($title =~ /^[0-9]$/) {$title = '0-9';}
    elsif ($title !~ /^[A-Z]$/) {
        my $outhandle = $self->{'outhandle'};
        print $outhandle "AZCompactList: WARNING $classification has badly formatted title ($title)\n";
    }
    $classhash->{$title} = [] unless defined $classhash->{$title};
    push (@{$classhash->{$title}}, $classification);
    }
    $classhash = $self->compactlist ($classhash);

    my @tmparr = ();
    foreach my $subsection (sort keys (%$classhash)) {
    push (@tmparr, $subsection);
    }
    
    # if there's a 0-9 section it will have been sorted to the beginning
    # but we want it at the end
    if ($tmparr[0] eq '0-9') {
    shift @tmparr;
    push (@tmparr, '0-9');
    }
    foreach my $subclass (@tmparr) 
    {
    my $tempclassify 
        = (scalar(@tmparr)==1) 
        ? ($self->get_entry(" ", "VList", $metaname))
        : ($self->get_entry($subclass, "VList", $metaname));


    foreach my $subsubOID (@{$classhash->{$subclass}}) 
    {
            if ($subsubOID =~ /^CLASSIFY\.(.*)$/ 
        && defined $self->{'classifiers'}->{$1}) 
        {
        # this is a "bookshelf" node... >1 entry compacted
                push (@{$tempclassify->{'contains'}}, 
              $self->{'classifiers'}->{$1}->{'classifyinfo'});
        # set the metadata field name, for mdoffset to work
        $self->{'classifiers'}->{$1}->{'classifyinfo'}->{'mdtype'}=
            $metaname;
        }
        else
        {
        $subsubOID =~ s/^Metavalue_(\d+)\.//;
        # record the offset if this metadata type has multiple values
        my $metaname_offset = $1 -1;
        my $oid_rec = {'OID'=>$subsubOID, 'offset'=>$metaname_offset};
        push (@{$tempclassify->{'contains'}}, $oid_rec);
        }
    }
    push (@{$classifyinfo->{'contains'}}, $tempclassify);
    }

    return $classifyinfo;
}

sub compactlist {
    my $self = shift (@_);
    my ($classhashref) = @_;
    my $compactedhash = {};
    my @currentOIDs = ();
    my $currentfirstletter = "";
    my $currentlastletter = "";
    my $lastkey = "";

    # minimum and maximum documents to be displayed per page.
    # the actual maximum will be max + (min-1).
    # the smallest sub-section is a single letter at present
    # so in this case there may be many times max documents
    # displayed on a page.
    my $min = $self->{'mincompact'}; 
    my $max = $self->{'maxcompact'};

    foreach my $subsection (sort keys %$classhashref) {
    if ($subsection eq '0-9') {
        @{$compactedhash->{$subsection}} = @{$classhashref->{$subsection}};
        next;
    }
    $currentfirstletter = $subsection if $currentfirstletter eq "";
    if ((scalar (@currentOIDs) < $min) ||
        ((scalar (@currentOIDs) + scalar (@{$classhashref->{$subsection}})) <= $max)) {
        push (@currentOIDs, @{$classhashref->{$subsection}});
        $currentlastletter = $subsection;
    } else {

        if ($currentfirstletter eq $currentlastletter) {
        @{$compactedhash->{$currentfirstletter}} = @currentOIDs;
        $lastkey = $currentfirstletter;
        } else {
        @{$compactedhash->{"$currentfirstletter-$currentlastletter"}} = @currentOIDs;
        $lastkey = "$currentfirstletter-$currentlastletter";
        } 
        if (scalar (@{$classhashref->{$subsection}}) >= $max) {
        $compactedhash->{$subsection} = $classhashref->{$subsection};
        @currentOIDs = ();
        $currentfirstletter = "";
        $lastkey=$subsection;
        } else {
        @currentOIDs = @{$classhashref->{$subsection}};
        $currentfirstletter = $subsection;
        $currentlastletter = $subsection;
        }
    }
    }

    # add final OIDs to last sub-classification if there aren't many otherwise
    # add final sub-classification

    # don't add if there aren't any oids
    if (! scalar (@currentOIDs)) {return $compactedhash;}

    if (scalar (@currentOIDs) < $min) {
    my ($newkey) = $lastkey =~ /^(.)/;
    @currentOIDs = (@{$compactedhash->{$lastkey}}, @currentOIDs);
    delete $compactedhash->{$lastkey};
    @{$compactedhash->{"$newkey-$currentlastletter"}} = @currentOIDs;
    } else {
    if ($currentfirstletter eq $currentlastletter) {
        @{$compactedhash->{$currentfirstletter}} = @currentOIDs;
    } else {
        @{$compactedhash->{"$currentfirstletter-$currentlastletter"}} = @currentOIDs;
    } 
    }

    return $compactedhash;
}

1;