X-Git-Url: http://git.shiar.net/perl/list-index.git/blobdiff_plain/2af0622fdc633320a7172164ddb9c7436e41998f..e288145c227aef0ecfed7c26e135ca2bbd77c040:/lib/List/Index.pm

diff --git a/lib/List/Index.pm b/lib/List/Index.pm
index 4ce9c25..719aca7 100644
--- a/lib/List/Index.pm
+++ b/lib/List/Index.pm
@@ -22,17 +22,17 @@ sub ranges {
 	my $length   = $options->{length  } || 4;
 	my $pages    = $options->{pages   } || 1 + int $#$self / $pagesize;
 
-	$pagesize = @$self / $pages;
-	my $offset = $pagesize + .5;
-	my $shrunk = 0;
-	my $enlarged = 0;
+	$pagesize = $pages >= $#$self ? 1 : @$self / $pages;
+	my $lookbehind = -$context;
+	my $lookahead  =  $context;
+
 	my @links = ('');
-	while ($offset < @$self) {
+	for (my $offset = $pagesize + .5; $offset < @$self; $offset += $pagesize) {
 		my $link = substr $self->[$offset], 0, $length;
 		if ($context) {
 			my $penalty = 0;
 			# take a value slightly before the current offset
-			if ((my $before = $offset - $context + $shrunk) > 0) {
+			if ((my $before = $offset + $lookbehind) > 0) {
 				# see how much of it matches the current link
 				my $trim = 1;
 				for my $match (split //, $self->[$before - 1]) {
@@ -49,9 +49,10 @@ sub ranges {
 				}
 			}
 
-			$shrunk = 0;
+			$lookbehind = -$context;
+
 			# take a value after the current offset
-			if ((my $after = $offset + $context - $enlarged) < $#$self) {
+			if ((my $after = $offset + $lookahead) < $#$self) {
 				# see how much of it matches the current link
 				my $trim = 1;
 				for my $match (split //, $self->[$after]) {
@@ -63,27 +64,28 @@ sub ranges {
 					$link = substr $self->[$after], 0, $trim;
 					# advance lookbehind offset on the next page
 					$penalty = 0;
-					for ($offset .. $#$self) {
-						last if $self->[$offset + $shrunk] =~ /^\Q$link/;
-						$shrunk++;
+					for ($offset .. $after) {
+						last if $self->[$_] =~ /^\Q$link/;
+						$lookbehind++;
 					}
 				}
 			}
-			$enlarged = $penalty;
+
+			$lookahead = $context - $penalty;
 		}
 
-		push @links, $link;
-		$offset += $pagesize;
+		push @links, $link unless $links[-1] eq $link;
 	}
 
-	use List::MoreUtils 'uniq';
-	@links = uniq @links;
+	# add range end to each link
 	for my $i (0 .. $#links - 1) {
-		my ($link, $lastchar) = $links[$i + 1] =~ /(.*)(.)/;
-		$link .= $lastchar le 'a' ? '.' : chr( ord($lastchar) - 1 );
-		next if $link eq $links[$i] and $i;
-		$links[$i] .= '-'.$link;
+		# end at start of next value with the last character decremented
+		my $next = $links[$i + 1];
+		$next =~ s{(.)$}{ $1 le 'a' ? '.' : chr( ord($1) - 1 ) }e;
+		# amend range if it's ahead
+		$links[$i] .= '-'.$next unless $next eq $links[$i];
 	}
+	# final value takes the rest
 	$links[-1] .= '-';
 
 	return \@links;