Move diff logic out of helper

app/helpers/wiki_page_versions_helper.rb

@@ -12,59 +12,13 @@ module WikiPageVersionsHelper
     status.join(" ")
   end
 
-  def wiki_page_diff(thispage, otherpage)
+  def wiki_other_names_diff(thispage, otherpage)
+    pattern = Regexp.new('\S+|\s+')
+    DiffBuilder.new("#{thispage.other_names}\n\n", "#{otherpage.other_names}\n\n", pattern).build
+  end
+
+  def wiki_body_diff(thispage, otherpage)
     pattern = Regexp.new('(?:<.+?>)|(?:\w+)|(?:[ \t]+)|(?:\r?\n)|(?:.+?)')
-    other_names_pattern = Regexp.new('\S+|\s+')
+    DiffBuilder.new(thispage.body, otherpage.body, pattern).build
-
-    thisarr = thispage.body.scan(pattern)
-    otharr = otherpage.body.scan(pattern)
-
-    if thispage.other_names.present? || otherpage.other_names.present?
-      thisarr = "#{thispage.other_names}\n\n".scan(other_names_pattern) + thisarr
-      otharr = "#{otherpage.other_names}\n\n".scan(other_names_pattern) + otharr
-    end
-
-    cbo = Diff::LCS::ContextDiffCallbacks.new
-    diffs = thisarr.diff(otharr, cbo)
-
-    escape_html = ->(str) {str.gsub(/&/, '&amp;').gsub(/</, '&lt;').gsub(/>/, '&gt;')}
-
-    output = thisarr
-    output.each { |q| q.replace(escape_html[q]) }
-
-    diffs.reverse_each do |hunk|
-      newchange = hunk.max {|a, b| a.old_position <=> b.old_position}
-      newstart = newchange.old_position
-      oldstart = hunk.min {|a, b| a.old_position <=> b.old_position}.old_position
-
-      if newchange.action == '+'
-        output.insert(newstart, '</ins>')
-      end
-
-      hunk.reverse_each do |chg|
-        case chg.action
-        when '-'
-          oldstart = chg.old_position
-          output[chg.old_position] = '<br>' if chg.old_element.match(/^\r?\n$/)
-        when '+'
-          if chg.new_element.match(/^\r?\n$/)
-            output.insert(chg.old_position, '<br>')
-          else
-            output.insert(chg.old_position, (escape_html[chg.new_element]).to_s)
-          end
-        end
-      end
-
-      if newchange.action == '+'
-        output.insert(newstart, '<ins>')
-      end
-
-      if hunk[0].action == '-'
-        output.insert((newstart == oldstart || newchange.action != '+') ? newstart + 1 : newstart, '</del>')
-        output.insert(oldstart, '<del>')
-      end
-    end
-
-    output.join.gsub(/\r?\n/, '<br>').html_safe
   end
 end

app/logical/diff_builder.rb

@@ -0,0 +1,57 @@
+class DiffBuilder
+  attr_reader :this_text, :that_text, :pattern
+
+  def initialize(this_text, that_text, pattern)
+    @this_text = this_text
+    @that_text = that_text
+    @pattern = pattern
+  end
+
+  def build
+    thisarr = this_text.scan(pattern)
+    otharr = that_text.scan(pattern)
+
+    cbo = Diff::LCS::ContextDiffCallbacks.new
+    diffs = thisarr.diff(otharr, cbo)
+
+    escape_html = ->(str) {str.gsub(/&/, '&amp;').gsub(/</, '&lt;').gsub(/>/, '&gt;')}
+
+    output = thisarr
+    output.each { |q| q.replace(escape_html[q]) }
+
+    diffs.reverse_each do |hunk|
+      newchange = hunk.max {|a, b| a.old_position <=> b.old_position}
+      newstart = newchange.old_position
+      oldstart = hunk.min {|a, b| a.old_position <=> b.old_position}.old_position
+
+      if newchange.action == '+'
+        output.insert(newstart, '</ins>')
+      end
+
+      hunk.reverse_each do |chg|
+        case chg.action
+        when '-'
+          oldstart = chg.old_position
+          output[chg.old_position] = '<br>' if chg.old_element.match(/^\r?\n$/)
+        when '+'
+          if chg.new_element.match(/^\r?\n$/)
+            output.insert(chg.old_position, '<br>')
+          else
+            output.insert(chg.old_position, (escape_html[chg.new_element]).to_s)
+          end
+        end
+      end
+
+      if newchange.action == '+'
+        output.insert(newstart, '<ins>')
+      end
+
+      if hunk[0].action == '-'
+        output.insert((newstart == oldstart || newchange.action != '+') ? newstart + 1 : newstart, '</del>')
+        output.insert(oldstart, '<del>')
+      end
+    end
+
+    output.join.gsub(/\r?\n/, '<br>').html_safe
+  end
+end

app/views/wiki_page_versions/diff.html.erb

@@ -7,7 +7,10 @@
     <p>Showing differences between <%= compact_time @thispage.updated_at %> (<%= link_to_user @thispage.updater %>) and <%= compact_time @otherpage.updated_at %> (<%= link_to_user @otherpage.updater %>)</p>
 
     <div>
-      <%= wiki_page_diff(@thispage, @otherpage) %>
+      <%= wiki_other_names_diff(@thispage, @otherpage) %>
+    </div>
+    <div>
+      <%= wiki_body_diff(@thispage, @otherpage) %>
     </div>
   <% else %>
     <p>The artist requested removal of this page.</p>