1 files changed, 82 insertions, 0 deletions
diff --git a/lib/gitlab/diff/highlight.rb b/lib/gitlab/diff/highlight.rb
new file mode 100644
index 00000000000..a7f925ce134
--- /dev/null
+++ b/lib/gitlab/diff/highlight.rb
@@ -0,0 +1,82 @@
+module Gitlab
+  module Diff
+    class Highlight
+      attr_reader :diff_file, :diff_lines, :raw_lines
+
+      delegate :old_path, :new_path, :old_ref, :new_ref, to: :diff_file, prefix: :diff
+
+      def initialize(diff_lines)
+        if diff_lines.is_a?(Gitlab::Diff::File)
+          @diff_file = diff_lines
+          @diff_lines = @diff_file.diff_lines
+        else
+          @diff_lines = diff_lines
+        end
+        @raw_lines = @diff_lines.map(&:text)
+      end
+
+      def highlight
+        @diff_lines.map.with_index do |diff_line, i|
+          diff_line = diff_line.dup
+          # ignore highlighting for "match" lines
+          next diff_line if diff_line.type == 'match' || diff_line.type == 'nonewline'
+
+          rich_line = highlight_line(diff_line, i)
+
+          if line_inline_diffs = inline_diffs[i]
+            rich_line = InlineDiffMarker.new(diff_line.text, rich_line).mark(line_inline_diffs)
+          end
+
+          diff_line.text = rich_line.html_safe
+
+          diff_line
+        end
+      end
+
+      private
+
+      def highlight_line(diff_line, index)
+        return html_escape(diff_line.text) unless diff_file && diff_file.diff_refs
+
+        line_prefix = diff_line.text.match(/\A(.)/) ? $1 : ' '
+
+        case diff_line.type
+        when 'new', nil
+          rich_line = new_lines[diff_line.new_pos - 1]
+        when 'old'
+          rich_line = old_lines[diff_line.old_pos - 1]
+        end
+
+        # Only update text if line is found. This will prevent
+        # issues with submodules given the line only exists in diff content.
+        rich_line ? line_prefix + rich_line : html_escape(diff_line.text)
+      end
+
+      def inline_diffs
+        @inline_diffs ||= InlineDiff.new(@raw_lines).inline_diffs
+      end
+
+      def old_lines
+        return unless diff_file
+        @old_lines ||= Gitlab::Highlight.highlight_lines(*processing_args(:old))
+      end
+
+      def new_lines
+        return unless diff_file
+        @new_lines ||= Gitlab::Highlight.highlight_lines(*processing_args(:new))
+      end
+
+      def processing_args(version)
+        ref  = send("diff_#{version}_ref")
+        path = send("diff_#{version}_path")
+
+        [ref.project.repository, ref.id, path]
+      end
+
+      def html_escape(str)
+        replacements = { '&' => '&amp;', '>' => '&gt;', '<' => '&lt;', '"' => '&quot;', "'" => '&#39;' }
+        str.gsub(/[&"'><]/, replacements)
+      end
+    end
+  end
+end