FIX: remove notifications on deleted topics from the stream

app/controllers/notifications_controller.rb

@@ -28,6 +28,7 @@ class NotificationsController < ApplicationController
     end
 
     notifications = Notification.where(user_id: user.id)
+        .visible
         .includes(:topic)
         .limit(60)
         .where('created_at < ?', params[:before])

app/models/notification.rb

@@ -8,7 +8,10 @@ class Notification < ActiveRecord::Base
   validates_presence_of :notification_type
 
   scope :unread, lambda { where(read: false) }
-  scope :recent, lambda {|n=nil| n ||= 10; order('created_at desc').limit(n) }
+  scope :recent, lambda {|n=nil| n ||= 10; order('notifications.created_at desc').limit(n) }
+  scope :visible , lambda { where('notifications.topic_id IS NULL OR notifications.topic_id IN (
+                                SELECT id FROM topics
+                                  WHERE deleted_at IS NULL)') }
 
   after_save :refresh_notification_count
   after_destroy :refresh_notification_count
@@ -39,6 +42,7 @@ class Notification < ActiveRecord::Base
   def self.interesting_after(min_date)
     result =  where("created_at > ?", min_date)
               .includes(:topic)
+              .visible
               .unread
               .limit(20)
               .order("CASE WHEN notification_type = #{Notification.types[:replied]} THEN 1
@@ -98,13 +102,19 @@ class Notification < ActiveRecord::Base
 
   def self.recent_report(user, count = nil)
     count ||= 10
-    notifications = user.notifications.recent(count).includes(:topic).to_a
+    notifications = user.notifications
+                        .visible
+                        .recent(count)
+                        .includes(:topic)
+                        .to_a
 
     if notifications.present?
-      notifications += user.notifications
-        .order('created_at desc')
+      notifications += user
+        .notifications
+        .order('notifications.created_at desc')
         .where(read: false, notification_type: Notification.types[:private_message])
-        .where('id < ?', notifications.last.id)
+        .joins(:topic)
+        .where('notifications.id < ?', notifications.last.id)
         .limit(count)
 
       notifications.sort do |x,y|

app/models/user.rb

@@ -237,7 +237,7 @@ class User < ActiveRecord::Base
   end
 
   def unread_notifications_by_type
-    @unread_notifications_by_type ||= notifications.where("id > ? and read = false", seen_notification_id).group(:notification_type).count
+    @unread_notifications_by_type ||= notifications.visible.where("id > ? and read = false", seen_notification_id).group(:notification_type).count
   end
 
   def reload
@@ -248,7 +248,7 @@ class User < ActiveRecord::Base
   end
 
   def unread_private_messages
-    @unread_pms ||= notifications.where("read = false AND notification_type = ?", Notification.types[:private_message]).count
+    @unread_pms ||= notifications.visible.where("read = false AND notification_type = ?", Notification.types[:private_message]).count
   end
 
   def unread_notifications