X-Git-Url: http://koha-dev.rot13.org:8081/gitweb/?a=blobdiff_plain;f=C4%2FTags.pm;h=7f94da4d0eaa1b2b37285e7690c0cad64b592da0;hb=d00d07cae751986a220d114ff165cbf5206a0283;hp=06c1e1db6de4153d94e4ff80359f1eaae87f55db;hpb=0b0212cae3497f7746eb58a5397453c6e0173ba0;p=koha-ffzg.git

diff --git a/C4/Tags.pm b/C4/Tags.pm
index 06c1e1db6d..7f94da4d0e 100644
--- a/C4/Tags.pm
+++ b/C4/Tags.pm
@@ -1,69 +1,72 @@
 package C4::Tags;
+
+# Copyright Liblime 2008
+# Parts Copyright ACPL 2011
+#
 # This file is part of Koha.
 #
-# Koha 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.
+# Koha 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 3 of the License, or
+# (at your option) any later version.
 #
-# Koha 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.
+# Koha 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
-# Koha; if not, write to the Free Software Foundation, Inc., 59 Temple Place,
-# Suite 330, Boston, MA  02111-1307 USA
+# You should have received a copy of the GNU General Public License
+# along with Koha; if not, see <http://www.gnu.org/licenses>.
 
 use strict;
 use warnings;
-use Carp;
+use Carp qw( carp );
 use Exporter;
 
 use C4::Context;
-use C4::Debug;
-
-use vars qw($VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS);
-use vars qw($ext_dict $select_all @fields);
-
+use Module::Load::Conditional qw( check_install );
+use Koha::Tags;
+use Koha::Tags::Approvals;
+use Koha::Tags::Indexes;
+use constant TAG_FIELDS => qw(tag_id borrowernumber biblionumber term language date_created);
+use constant TAG_SELECT => "SELECT " . join(',', TAG_FIELDS) . "\n FROM   tags_all\n";
+
+our (@ISA, @EXPORT_OK);
 BEGIN {
-	$VERSION = 0.03;
-	@ISA = qw(Exporter);
-	@EXPORT_OK = qw(
-		&get_tag &get_tags &get_tag_rows
-		&add_tags &add_tag
-		&delete_tag_row_by_id
-		&remove_tag
-		&delete_tag_rows_by_ids
-		&rectify_weights
-		&get_approval_rows
-		&blacklist
-		&whitelist
-		&is_approved
-		&approval_counts
-		&get_count_by_tag_status
-		&get_filters
-	);
-	# %EXPORT_TAGS = ();
-	$ext_dict = C4::Context->preference('TagsExternalDictionary');
-	if ($debug) {
-		require Data::Dumper;
-		import Data::Dumper qw(:DEFAULT);
-		print STDERR __PACKAGE__ . " external dictionary = " . ($ext_dict||'none') . "\n";
-	}
+    @ISA       = qw(Exporter);
+    @EXPORT_OK = qw(
+      get_tags get_tag_rows
+      add_tags
+      add_tag
+      add_tag_approval
+      add_tag_index
+      remove_tag
+      get_approval_rows
+      blacklist
+      whitelist
+      is_approved
+      approval_counts
+      get_count_by_tag_status
+      get_filters
+      stratify_tags
+    );
+    my $ext_dict = C4::Context->preference('TagsExternalDictionary');
+    if ( $ext_dict && ! check_install( module => 'Lingua::Ispell' ) ) {
+        warn "Ignoring TagsExternalDictionary, because Lingua::Ispell is not installed.";
+        $ext_dict = q{};
+    }
 	if ($ext_dict) {
 		require Lingua::Ispell;
-		import Lingua::Ispell qw(spellcheck add_word_lc save_dictionary);
+        import Lingua::Ispell qw(spellcheck add_word_lc);
+        $Lingua::Ispell::path = $ext_dict;
 	}
 }
 
-INIT {
-    $ext_dict and $Lingua::Ispell::path = $ext_dict;
-    $debug and print STDERR "\$Lingua::Ispell::path = $Lingua::Ispell::path\n";
-	@fields = qw(tag_id borrowernumber biblionumber term language date_created);
-	$select_all = "SELECT " . join(',',@fields) . "\n FROM   tags_all\n";
-}
+=head1 C4::Tags.pm - Support for user tagging of biblios.
+
+=cut
 
-sub get_filters (;$) {
+sub get_filters {
 	my $query = "SELECT * FROM tags_filters ";
 	my ($sth);
 	if (@_) {
@@ -79,7 +82,7 @@ sub get_filters (;$) {
 # 	(SELECT count(*) FROM tags_all     ) as tags_all,
 # 	(SELECT count(*) FROM tags_index   ) as tags_index,
 
-sub approval_counts () { 
+sub approval_counts {
 	my $query = "SELECT
 		(SELECT count(*) FROM tags_approval WHERE approved= 1) as approved_count,
 		(SELECT count(*) FROM tags_approval WHERE approved=-1) as rejected_count,
@@ -89,7 +92,6 @@ sub approval_counts () {
 	$sth->execute;
 	my $result = $sth->fetchrow_hashref();
 	$result->{approved_total} = $result->{approved_count} + $result->{rejected_count} + $result->{unapproved_count};
-	$debug and warn "counts returned: " . Dumper $result;
 	return $result;
 }
 
@@ -111,77 +113,44 @@ sub get_count_by_tag_status  {
   return $sth->fetchrow;
 }
 
-sub remove_tag ($;$) {
-	my $tag_id  = shift or return undef;
-	my $user_id = (@_) ? shift : undef;
-	my $rows = (defined $user_id) ?
-			get_tag_rows({tag_id=>$tag_id, borrowernumber=>$user_id}) :
-			get_tag_rows({tag_id=>$tag_id}) ;
-	$rows or return 0;
-	(scalar(@$rows) == 1) or return undef;	# should never happen (duplicate ids)
-	my $row = shift(@$rows);
-	($tag_id == $row->{tag_id}) or return 0;
-	my $tags = get_tags({term=>$row->{term}, biblionumber=>$row->{biblionumber}});
-	my $index = shift(@$tags);
-	$debug and print STDERR
-		sprintf "remove_tag: tag_id=>%s, biblionumber=>%s, weight=>%s, weight_total=>%s\n",
-			$row->{tag_id}, $row->{biblionumber}, $index->{weight}, $index->{weight_total};
-	if ($index->{weight} <= 1) {
-		delete_tag_index($row->{term},$row->{biblionumber});
-	} else {
-		decrement_weight($row->{term},$row->{biblionumber});
-	}
-	if ($index->{weight_total} <= 1) {
-		delete_tag_approval($row->{term});
-	} else {
-		decrement_weight_total($row->{term});
-	}
-	delete_tag_row_by_id($tag_id);
-}
-
-sub delete_tag_index ($$) {
-	(@_) or return undef;
-	my $sth = C4::Context->dbh->prepare("DELETE FROM tags_index WHERE term = ? AND biblionumber = ? LIMIT 1");
-	$sth->execute(@_);
-	return $sth->rows || 0;
-}
-sub delete_tag_approval ($) {
-	(@_) or return undef;
-	my $sth = C4::Context->dbh->prepare("DELETE FROM tags_approval WHERE term = ? LIMIT 1");
-	$sth->execute(shift);
-	return $sth->rows || 0;
-}
-sub delete_tag_row_by_id ($) {
-	(@_) or return undef;
-	my $sth = C4::Context->dbh->prepare("DELETE FROM tags_all WHERE tag_id = ? LIMIT 1");
-	$sth->execute(shift);
-	return $sth->rows || 0;
-}
-sub delete_tag_rows_by_ids (@) {
-	(@_) or return undef;
-	my $i=0;
-	foreach(@_) {
-		$i += delete_tag_row_by_id($_);
-	}
-	($i == scalar(@_)) or
-		warn sprintf "delete_tag_rows_by_ids tried %s tag_ids, only succeeded on $i", scalar(@_);
-	return $i;
-}
-
-sub get_tag_rows ($) {
+sub remove_tag {
+    my $tag_id  = shift or return;
+    my $user_id = (@_) ? shift : undef;
+    my $rows = (defined $user_id) ?
+            get_tag_rows({tag_id=>$tag_id, borrowernumber=>$user_id}) :
+            get_tag_rows({tag_id=>$tag_id}) ;
+    $rows or return 0;
+    (scalar(@$rows) == 1) or return;    # should never happen (duplicate ids)
+    my $row = shift(@$rows);
+    ($tag_id == $row->{tag_id}) or return 0;
+    my $tags = get_tags({term=>$row->{term}, biblionumber=>$row->{biblionumber}});
+    my $index = shift(@$tags);
+    if ($index->{weight} <= 1) {
+        Koha::Tags::Indexes->search({ term => $row->{term}, biblionumber => $row->{biblionumber} })->delete;
+    } else {
+        decrement_weight($row->{term},$row->{biblionumber});
+    }
+    if ($index->{weight_total} <= 1) {
+        Koha::Tags::Approvals->search({ term => $row->{term} })->delete;
+    } else {
+        decrement_weight_total($row->{term});
+    }
+    Koha::Tags->search({ tag_id => $tag_id })->delete;
+}
+
+sub get_tag_rows {
 	my $hash = shift || {};
-	my @ok_fields = @fields;
+    my @ok_fields = TAG_FIELDS;
 	push @ok_fields, 'limit';	# push the limit! :)
 	my $wheres;
 	my $limit  = "";
 	my @exe_args = ();
 	foreach my $key (keys %$hash) {
-		$debug and print STDERR "get_tag_rows arg. '$key' = ", $hash->{$key}, "\n";
 		unless (length $key) {
 			carp "Empty argument key to get_tag_rows: ignoring!";
 			next;
 		}
-		unless (1 == scalar grep {/^ $key $/x} @ok_fields) {
+		unless (1 == scalar grep { $_ eq $key } @ok_fields) {
 			carp "get_tag_rows received unreconized argument key '$key'.";
 			next;
 		}
@@ -197,9 +166,7 @@ sub get_tag_rows ($) {
 			push @exe_args, $hash->{$key};
 		}
 	}
-	my $query = $select_all . ($wheres||'') . $limit;
-	$debug and print STDERR "get_tag_rows query:\n $query\n",
-							"get_tag_rows query args: ", join(',', @exe_args), "\n";
+    my $query = TAG_SELECT . ($wheres||'') . $limit;
 	my $sth = C4::Context->dbh->prepare($query);
 	if (@exe_args) {
 		$sth->execute(@exe_args);
@@ -209,7 +176,7 @@ sub get_tag_rows ($) {
 	return $sth->fetchall_arrayref({});
 }
 
-sub get_tags (;$) {		# i.e., from tags_index
+sub get_tags {		# i.e., from tags_index
 	my $hash = shift || {};
 	my @ok_fields = qw(term biblionumber weight limit sort approved);
 	my $wheres;
@@ -217,12 +184,11 @@ sub get_tags (;$) {		# i.e., from tags_index
 	my $order  = "";
 	my @exe_args = ();
 	foreach my $key (keys %$hash) {
-		$debug and print STDERR "get_tags arg. '$key' = ", $hash->{$key}, "\n";
 		unless (length $key) {
 			carp "Empty argument key to get_tags: ignoring!";
 			next;
 		}
-		unless (1 == scalar grep {/^ $key $/x} @ok_fields) {
+		unless (1 == scalar grep { $_ eq $key } @ok_fields) {
 			carp "get_tags received unreconized argument key '$key'.";
 			next;
 		}
@@ -267,8 +233,6 @@ sub get_tags (;$) {		# i.e., from tags_index
 	LEFT JOIN tags_approval 
 	ON        tags_index.term = tags_approval.term
 	" . ($wheres||'') . $order . $limit;
-	$debug and print STDERR "get_tags query:\n $query\n",
-							"get_tags query args: ", join(',', @exe_args), "\n";
 	my $sth = C4::Context->dbh->prepare($query);
 	if (@exe_args) {
 		$sth->execute(@exe_args);
@@ -278,7 +242,7 @@ sub get_tags (;$) {		# i.e., from tags_index
 	return $sth->fetchall_arrayref({});
 }
 
-sub get_approval_rows (;$) {		# i.e., from tags_approval
+sub get_approval_rows {		# i.e., from tags_approval
 	my $hash = shift || {};
 	my @ok_fields = qw(term approved date_approved approved_by weight_total limit sort borrowernumber);
 	my $wheres;
@@ -286,12 +250,11 @@ sub get_approval_rows (;$) {		# i.e., from tags_approval
 	my $order  = "";
 	my @exe_args = ();
 	foreach my $key (keys %$hash) {
-		$debug and print STDERR "get_approval_rows arg. '$key' = ", $hash->{$key}, "\n";
 		unless (length $key) {
 			carp "Empty argument key to get_approval_rows: ignoring!";
 			next;
 		}
-		unless (1 == scalar grep {/^ $key $/x} @ok_fields) {
+		unless (1 == scalar grep { $_ eq $key } @ok_fields) {
 			carp "get_approval_rows received unreconized argument key '$key'.";
 			next;
 		}
@@ -342,8 +305,6 @@ sub get_approval_rows (;$) {		# i.e., from tags_approval
 	LEFT JOIN borrowers
 	ON      tags_approval.approved_by = borrowers.borrowernumber ";
 	$query .= ($wheres||'') . $order . $limit;
-	$debug and print STDERR "get_approval_rows query:\n $query\n",
-							"get_approval_rows query args: ", join(',', @exe_args), "\n";
 	my $sth = C4::Context->dbh->prepare($query);
 	if (@exe_args) {
 		$sth->execute(@exe_args);
@@ -353,10 +314,11 @@ sub get_approval_rows (;$) {		# i.e., from tags_approval
 	return $sth->fetchall_arrayref({});
 }
 
-sub is_approved ($) {
-	my $term = shift or return undef;
+sub is_approved {
+	my $term = shift or return;
 	my $sth = C4::Context->dbh->prepare("SELECT approved FROM tags_approval WHERE term = ?");
 	$sth->execute($term);
+    my $ext_dict = C4::Context->preference('TagsExternalDictionary');
 	unless ($sth->rows) {
 		$ext_dict and return (spellcheck($term) ? 0 : 1);	# spellcheck returns empty on OK word
 		return 0;
@@ -364,8 +326,8 @@ sub is_approved ($) {
 	return $sth->fetchrow;
 }
 
-sub get_tag_index ($;$) {
-	my $term = shift or return undef;
+sub get_tag_index {
+	my $term = shift or return;
 	my $sth;
 	if (@_) {
 		$sth = C4::Context->dbh->prepare("SELECT * FROM tags_index WHERE term = ? AND biblionumber = ?");
@@ -379,7 +341,8 @@ sub get_tag_index ($;$) {
 
 sub whitelist {
 	my $operator = shift;
-	defined $operator or return undef; # have to test defined to allow =0 (kohaadmin)
+	defined $operator or return; # have to test defined to allow =0 (kohaadmin)
+    my $ext_dict = C4::Context->preference('TagsExternalDictionary');
 	if ($ext_dict) {
 		foreach (@_) {
 			spellcheck($_) or next;
@@ -401,7 +364,7 @@ sub whitelist {
 # a term mistakenly, you can still reverse it. But there is no going back to "neutral".
 sub blacklist {
 	my $operator = shift;
-	defined $operator or return undef; # have to test defined to allow =0 (kohaadmin)
+	defined $operator or return; # have to test defined to allow =0 (kohaadmin)
 	foreach (@_) {
 		my $aref = get_approval_rows({term=>$_});
 		if ($aref and scalar @$aref) {
@@ -414,23 +377,22 @@ sub blacklist {
 }
 sub add_filter {
 	my $operator = shift;
-	defined $operator or return undef; # have to test defined to allow =0 (kohaadmin)
+	defined $operator or return; # have to test defined to allow =0 (kohaadmin)
 	my $query = "INSERT INTO tags_blacklist (regexp,y,z) VALUES (?,?,?)";
 	# my $sth = C4::Context->dbh->prepare($query);
 	return scalar @_;
 }
 sub remove_filter {
 	my $operator = shift;
-	defined $operator or return undef; # have to test defined to allow =0 (kohaadmin)
+	defined $operator or return; # have to test defined to allow =0 (kohaadmin)
 	my $query = "REMOVE FROM tags_blacklist WHERE blacklist_id = ?";
 	# my $sth = C4::Context->dbh->prepare($query);
 	# $sth->execute($term);
 	return scalar @_;
 }
 
-sub add_tag_approval ($;$$) {	# or disapproval
-	$debug and warn "add_tag_approval(" . join(", ",map {defined($_) ? $_ : 'UNDEF'} @_) . ")";
-	my $term = shift or return undef;
+sub add_tag_approval {	# or disapproval
+	my $term = shift or return;
 	my $query = "SELECT * FROM tags_approval WHERE term = ?";
 	my $sth = C4::Context->dbh->prepare($query);
 	$sth->execute($term);
@@ -447,92 +409,55 @@ sub add_tag_approval ($;$$) {	# or disapproval
 	} else {
 		$query = "INSERT INTO tags_approval (term,date_approved) VALUES (?,NOW())";
 	}
-	$debug and print STDERR "add_tag_approval query: $query\nadd_tag_approval args: (" . join(", ", @exe_args) . ")\n";
 	$sth = C4::Context->dbh->prepare($query);
 	$sth->execute(@exe_args);
 	return $sth->rows;
 }
 
-sub mod_tag_approval ($$$) {
+sub mod_tag_approval {
 	my $operator = shift;
-	defined $operator or return undef; # have to test defined to allow =0 (kohaadmin)
-	my $term     = shift or return undef;
+	defined $operator or return; # have to test defined to allow =0 (kohaadmin)
+	my $term     = shift or return;
 	my $approval = (scalar @_ ? shift : 1);	# default is to approve
 	my $query = "UPDATE tags_approval SET approved_by=?, approved=?, date_approved=NOW() WHERE term = ?";
-	$debug and print STDERR "mod_tag_approval query: $query\nmod_tag_approval args: ($operator,$approval,$term)\n";
 	my $sth = C4::Context->dbh->prepare($query);
 	$sth->execute($operator,$approval,$term);
 }
 
-sub add_tag_index ($$;$) {
-	my $term         = shift or return undef;
-	my $biblionumber = shift or return undef;
+sub add_tag_index {
+	my $term         = shift or return;
+	my $biblionumber = shift or return;
 	my $query = "SELECT * FROM tags_index WHERE term = ? AND biblionumber = ?";
 	my $sth = C4::Context->dbh->prepare($query);
 	$sth->execute($term,$biblionumber);
 	($sth->rows) and return increment_weight($term,$biblionumber);
 	$query = "INSERT INTO tags_index (term,biblionumber) VALUES (?,?)";
-	$debug and print STDERR "add_tag_index query: $query\nadd_tag_index args: ($term,$biblionumber)\n";
 	$sth = C4::Context->dbh->prepare($query);
 	$sth->execute($term,$biblionumber);
 	return $sth->rows;
 }
 
-sub get_tag ($) {		# by tag_id
-	(@_) or return undef;
-	my $sth = C4::Context->dbh->prepare("$select_all WHERE tag_id = ?");
-	$sth->execute(shift);
-	return $sth->fetchrow_hashref;
-}
-
-sub rectify_weights (;$) {
-	my $dbh = C4::Context->dbh;
-	my $sth;
-	my $query = "
-	SELECT term,biblionumber,count(*) as count
-	FROM   tags_all
-	";
-	(@_) and $query .= " WHERE term =? ";
-	$query .= " GROUP BY term,biblionumber ";
-	$sth = $dbh->prepare($query);
-	if (@_) {
-		$sth->execute(shift);
-	} else {
-		$sth->execute();
-	}
-	my $results = $sth->fetchall_arrayref({}) or return undef;
-	my %tally = ();
-	foreach (@$results) {
-		_set_weight($_->{count},$_->{term},$_->{biblionumber});
-		$tally{$_->{term}} += $_->{count};
-	}
-	foreach (keys %tally) {
-		_set_weight_total($tally{$_},$_);
-	}
-	return ($results,\%tally);
-}
-
-sub increment_weights ($$) {
+sub increment_weights {
 	increment_weight(@_);
 	increment_weight_total(shift);
 }
-sub decrement_weights ($$) {
+sub decrement_weights {
 	decrement_weight(@_);
 	decrement_weight_total(shift);
 }
-sub increment_weight_total ($) {
+sub increment_weight_total {
 	_set_weight_total('weight_total+1',shift);
 }
-sub increment_weight ($$) {
+sub increment_weight {
 	_set_weight('weight+1',shift,shift);
 }
-sub decrement_weight_total ($) {
+sub decrement_weight_total {
 	_set_weight_total('weight_total-1',shift);
 }
-sub decrement_weight ($$) {
+sub decrement_weight {
 	_set_weight('weight-1',shift,shift);
 }
-sub _set_weight_total ($$) {
+sub _set_weight_total {
 	my $sth = C4::Context->dbh->prepare("
 	UPDATE tags_approval
 	SET    weight_total=" . (shift) . "
@@ -540,7 +465,7 @@ sub _set_weight_total ($$) {
 	");						# note: CANNOT use "?" for weight_total (see the args above).
 	$sth->execute(shift);	# just the term
 }
-sub _set_weight ($$$) {
+sub _set_weight {
 	my $dbh = C4::Context->dbh;
 	my $sth = $dbh->prepare("
 	UPDATE tags_index
@@ -551,22 +476,19 @@ sub _set_weight ($$$) {
 	$sth->execute(@_);
 }
 
-sub add_tag ($$;$$) {	# biblionumber,term,[borrowernumber,approvernumber]
-	my $biblionumber = shift or return undef;
-	my $term         = shift or return undef;
+sub add_tag {	# biblionumber,term,[borrowernumber,approvernumber]
+	my $biblionumber = shift or return;
+	my $term         = shift or return;
 	my $borrowernumber = (@_) ? shift : 0;		# the user, default to kohaadmin
 	$term =~ s/^\s+//;
 	$term =~ s/\s+$//;
-	($term) or return undef;	# must be more than whitespace
+	($term) or return;	# must be more than whitespace
 	my $rows = get_tag_rows({biblionumber=>$biblionumber, borrowernumber=>$borrowernumber, term=>$term, limit=>1});
 	my $query = "INSERT INTO tags_all
 	(borrowernumber,biblionumber,term,date_created)
 	VALUES (?,?,?,NOW())";
-	$debug and print STDERR "add_tag query: $query\n",
-							"add_tag query args: ($borrowernumber,$biblionumber,$term)\n";
 	if (scalar @$rows) {
-		$debug and carp "Duplicate tag detected.  Tag not added.";	
-		return undef;
+		return;
 	}
 	# add to tags_all regardless of approaval
 	my $sth = C4::Context->dbh->prepare($query);
@@ -575,27 +497,57 @@ sub add_tag ($$;$$) {	# biblionumber,term,[borrowernumber,approvernumber]
 	# then 
 	if (scalar @_) { 	# if arg remains, it is the borrowernumber of the approver: tag is pre-approved.
 		my $approver = shift;
-		$debug and print STDERR "term '$term' pre-approved by borrower #$approver\n";
 		add_tag_approval($term,$approver,1);
 		add_tag_index($term,$biblionumber,$approver);
 	} elsif (is_approved($term) >= 1) {
-		$debug and print STDERR "term '$term' approved by whitelist\n";
 		add_tag_approval($term,0,1);
 		add_tag_index($term,$biblionumber,1);
 	} else {
-		$debug and print STDERR "term '$term' NOT approved (yet)\n";
 		add_tag_approval($term);
 		add_tag_index($term,$biblionumber);
 	}
 }
 
+# This takes a set of tags, as returned by C<get_approval_rows> and divides
+# them up into a number of "strata" based on their weight. This is useful
+# to display them in a number of different sizes.
+#
+# Usage:
+#   ($min, $max) = stratify_tags($strata, $tags);
+# $stratum: the number of divisions you want
+# $tags: the tags, as provided by get_approval_rows
+# $min: the minimum stratum value
+# $max: the maximum stratum value. This may be the same as $min if there
+# is only one weight. Beware of divide by zeros.
+# This will add a field to the tag called "stratum" containing the calculated
+# value.
+sub stratify_tags {
+    my ( $strata, $tags ) = @_;
+    return (0,0) if !@$tags;
+    my ( $min, $max );
+    foreach (@$tags) {
+        my $w = $_->{weight_total};
+        $min = $w if ( !defined($min) || $min > $w );
+        $max = $w if ( !defined($max) || $max < $w );
+    }
+
+    # normalise min to zero
+    $max = $max - $min;
+    my $orig_min = $min;
+    $min = 0;
+
+    # if min and max are the same, just make it 1
+    my $span = ( $strata - 1 ) / ( $max || 1 );
+    foreach (@$tags) {
+        my $w = $_->{weight_total};
+        $_->{stratum} = int( ( $w - $orig_min ) * $span );
+    }
+    return ( $min, $max );
+}
+
 1;
 __END__
 
-=head1 C4::Tags.pm - Support for user tagging of biblios.
-
-More verose debugging messages are sent in the presence of non-zero $ENV{"DEBUG"}.
-
 =head2 add_tag(biblionumber,term[,borrowernumber])
 
 =head3 TO DO: Add real perldoc
@@ -649,7 +601,7 @@ This could be called an "approved terms" table.  See above regarding the Externa
 	approved       - Negative, 0 or positive if tag is rejected, pending or approved.
 	date_approved  - date of last action
 	approved_by    - staffer performing the last action
-	weight_total   - total occurance of term in any biblio by any users
+    weight_total   - total occurrence of term in any biblio by any users
 
 tags_index - This table is for performance, because by far the most common operation will 
 be fetching tags for a list of search results.  We will have a set of biblios, and we will