+sub diff_line_class {
+ my ($line, $from, $to) = @_;
+
+ # ordinary diff
+ my $num_sign = 1;
+ # combined diff
+ if ($from && $to && ref($from->{'href'}) eq "ARRAY") {
+ $num_sign = scalar @{$from->{'href'}};
+ }
+
+ my @diff_line_classifier = (
+ { regexp => qr/^\@\@{$num_sign} /, class => "chunk_header"},
+ { regexp => qr/^\\/, class => "incomplete" },
+ { regexp => qr/^ {$num_sign}/, class => "ctx" },
+ # classifier for context must come before classifier add/rem,
+ # or we would have to use more complicated regexp, for example
+ # qr/(?= {0,$m}\+)[+ ]{$num_sign}/, where $m = $num_sign - 1;
+ { regexp => qr/^[+ ]{$num_sign}/, class => "add" },
+ { regexp => qr/^[- ]{$num_sign}/, class => "rem" },
+ );
+ for my $clsfy (@diff_line_classifier) {
+ return $clsfy->{'class'}
+ if ($line =~ $clsfy->{'regexp'});
+ }
+
+ # fallback
+ return "";
+}
+