Adds new private thread notification

app/models/thredded/private_topic.rb

@@ -36,7 +36,38 @@ def user_id=(ids)
     end
 
     def users_to_sentence
-      users.map{ |user| user.to_s.capitalize }.to_sentence
+      users.map { |user| user.to_s.capitalize }.to_sentence
+    end
+
+    def self.unread_privates?(user)
+      brand_new_private_topics?(user) || latest_private_topic_unread?(user)
+    end
+
+    private
+
+    def self.brand_new_private_topics?(user)
+      user_private_topic_count(user) > 0 && latest_private_topic_read_date(user).blank?
+    end
+
+    def self.latest_private_topic_unread?(user)
+      latest_private_topic_date(user) > latest_private_topic_read_date(user)
+    end
+
+    def self.latest_private_topic_date(user)
+      user.thredded_private_topics.maximum('updated_at')
+    end
+
+    def self.latest_private_topic_read_date(user)
+      user
+      .thredded_private_topics
+      .includes(:user_topic_reads)
+      .where('thredded_user_topic_reads.user_id = ?', user.id)
+      .references(:user_topic_reads)
+      .maximum('thredded_user_topic_reads.updated_at')
+    end
+
+    def self.user_private_topic_count(user)
+      user.thredded_private_topics.count
     end
   end
 end

app/views/thredded/shared/_topic_nav.html.erb

@@ -9,11 +9,10 @@
   <% end %>
 
   <ul class="listings">
-    <% cache ['topic-nav-list', current_user, messageboard] do %>
-      <li class="topic_list"><%= link_to 'topics', messageboard_topics_path %></li>
-      <% if can? :list, messageboard.private_topics.build %>
-        <li class="private_topic_list"><%= link_to 'private topics', messageboard_private_topics_path %></li>
-      <% end %>
+    <li class="topic_list"><%= link_to 'topics', messageboard_topics_path %></li>
+    <% if can? :list, messageboard.private_topics.build %>
+        <% unread = Thredded::PrivateTopic.unread_privates?(current_user) %>
+        <li class="private_topic_list"><%= link_to 'private topics', messageboard_private_topics_path, class: unread ? 'unread' : '' %></li>
     <% end %>
 
     <%= render 'thredded/search/form' %>

spec/models/thredded/private_topic_spec.rb

@@ -50,5 +50,28 @@ module Thredded
         @topic.users_to_sentence.should eq 'Privateuser1 and Privateuser2'
       end
     end
+
+    describe '.unread_privates?' do
+      context 'when a user sends another user a PM' do
+        it 'the user should have unread private topics' do
+          expect(PrivateTopic.unread_privates?(@user2)).to be_true
+        end
+      end
+
+      context 'when a user reads a private thread' do
+        it 'the user should not have unread private topics' do
+          create(:user_topic_read, user: @user2, topic: @topic)
+          expect(PrivateTopic.unread_privates?(@user2)).to be_false
+        end
+      end
+
+      context 'when a user reads a PM and gets another PM' do
+        it 'the user should have unread private topics' do
+          create(:user_topic_read, user: @user2, topic: @topic)
+          create(:private_topic, messageboard: @messageboard, users: [@user1, @user2])
+          expect(PrivateTopic.unread_privates?(@user2)).to be_true
+        end
+      end
+    end
   end
 end