Split complex Gitlab::InlineDiff::processing method

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

lib/gitlab/inline_diff.rb

@@ -16,15 +16,7 @@ module Gitlab
           # Skip inline diff if empty line was replaced with content
           next if first_line == "-\n"
 
-          first_the_same_symbols = 0
-          (0..max_length + 1).each do |i|
-            first_the_same_symbols = i - 1
-            if first_line[i] != second_line[i] && i > 0
-              break
-            end
-          end
-
-          first_token = first_line[0..first_the_same_symbols][1..-1]
+          first_token = find_first_token(first_line, second_line)
           start = first_token + START
 
           if first_token.empty?
@@ -36,23 +28,48 @@ module Gitlab
             diff_arr[index+2].sub!(first_token, first_token => start)
           end
 
+          last_token = find_last_token(first_line, second_line, first_token)
+
+          # This is tricky: escape backslashes so that `sub` doesn't interpret them
+          # as backreferences. Regexp.escape does NOT do the right thing.
+          replace_token = FINISH + last_token.gsub(/\\/, '\&\&')
+          diff_arr[index+1].sub!(/#{Regexp.escape(last_token)}$/, replace_token)
+          diff_arr[index+2].sub!(/#{Regexp.escape(last_token)}$/, replace_token)
+        end
+
+        diff_arr
+      end
+
+      def find_first_token(first_line, second_line)
+        max_length = [first_line.size, second_line.size].max
+        first_the_same_symbols = 0
+
+        (0..max_length + 1).each do |i|
+          first_the_same_symbols = i - 1
+
+          if first_line[i] != second_line[i] && i > 0
+            break
+          end
+        end
+
+        first_line[0..first_the_same_symbols][1..-1]
+      end
+
+      def find_last_token(first_line, second_line, first_token)
+        max_length = [first_line.size, second_line.size].max
         last_the_same_symbols = 0
+
         (1..max_length + 1).each do |i|
           last_the_same_symbols = -i
           shortest_line = second_line.size > first_line.size ? first_line : second_line
-            if ( first_line[-i] != second_line[-i] ) || "#{first_token}#{START}".size == shortest_line[1..-i].size
+
+          if (first_line[-i] != second_line[-i]) || "#{first_token}#{START}".size == shortest_line[1..-i].size
             break
           end
         end
+
         last_the_same_symbols += 1
-          last_token = first_line[last_the_same_symbols..-1]
-          # This is tricky: escape backslashes so that `sub` doesn't interpret them
-          # as backreferences. Regexp.escape does NOT do the right thing.
-          replace_token = FINISH + last_token.gsub(/\\/, '\&\&')
-          diff_arr[index+1].sub!(/#{Regexp.escape(last_token)}$/, replace_token)
-          diff_arr[index+2].sub!(/#{Regexp.escape(last_token)}$/, replace_token)
-        end
-        diff_arr
+        first_line[last_the_same_symbols..-1]
       end
 
       def _indexes_of_changed_lines(diff_arr)