X-Git-Url: http://git.shiar.nl/perl/list-index.git/blobdiff_plain/d6c30ef4ef400982bc1b08e9b7bf93993ea29be5..c6b7152b5b448744cce44c7ae52cf530c1e19bba:/lib/List/Index.pm

diff --git a/lib/List/Index.pm b/lib/List/Index.pm
index c42db44..57027fa 100644
--- a/lib/List/Index.pm
+++ b/lib/List/Index.pm
@@ -23,28 +23,50 @@ sub ranges {
 	my $pages    = $options->{pages   } || 1 + int $#$self / $pagesize;
 
 	$pagesize = @$self / $pages;
-	my $offset = 0;
-	my @links;
+	my $offset = $pagesize;
+	my @links = ('');
 	while ($offset < @$self) {
 		my $link = substr $self->[$offset], 0, $length;
 		if ($context) {
-			my $trim = 1;
-			my $before = $offset > $context ? $self->[$offset - $context] : '';
-			for my $match (split //, $before) {
-				scalar $link =~ /\G\Q$match/g or last;
-				$trim++;
+			{
+				# take a value slightly before the current offset
+				my $before = $offset > $context ? $self->[$offset - $context] : '.';
+				# see how much of it matches the current link
+				my $trim = 1;
+				for my $match (split //, $before) {
+					scalar $link =~ /\G\Q$match/g or last;
+					$trim++;
+				}
+				# truncate link upto where the earlier value starts to differ
+				substr($link, $trim) = '' unless $trim > length $link;
+			}
+
+			if ($offset + $context < $#$self) {
+				# take a value after the current offset
+				my $after = $self->[$offset + $context];
+				# see how much of it matches the current link
+				my $trim = 1;
+				for my $match (split //, $after) {
+					scalar $link =~ /\G\Q$match/g or last;
+					$trim++;
+				}
+				# use this link if it's shorter
+				if ($trim < length $link) {
+					$link = substr $after, 0, $trim;
+				}
 			}
-			substr($link, $trim) = '' unless $trim > length $link;
 		}
 
-		push @links, [$link];
+		push @links, $link;
 		$offset += $pagesize;
 	}
 
+	use List::MoreUtils 'uniq';
+	@links = map { [$_] } uniq @links;
 	for my $i (0 .. $#links - 1) {
 		my ($link, $lastchar) = $links[$i + 1]->[0] =~ /(.*)(.)/;
-		$link .= $lastchar eq '.' ? 'a' : chr( ord($lastchar) - 1 )
-			unless $lastchar eq 'a';
+		$link .= $lastchar le 'a' ? '.' : chr( ord($lastchar) - 1 );
+		next if $link eq $links[$i]->[0] and $i;
 		$links[$i]->[1] = $link;
 	}
 	$links[-1]->[1] = '';