FEATURE: collapse PM notifications

app/models/post_alert_observer.rb

@@ -60,8 +60,12 @@ class PostAlertObserver < ActiveRecord::Observer
   def after_create_post(post)
     if post.topic.private_message?
       # If it's a private message, notify the topic_allowed_users
-      post.topic.all_allowed_users.reject{ |a| a.id == post.user_id }.each do |a|
-        create_notification(a, Notification.types[:private_message], post)
+      post.topic.all_allowed_users.reject{ |user| user.id == post.user_id }.each do |user|
+        next if user.blank?
+
+        destroy_notifications(user, Notification.types[:private_message], post.topic)
+        unread_post = first_unread_post(user,post.topic)
+        create_notification(user, Notification.types[:private_message], unread_post)
       end
     elsif post.post_type != Post.types[:moderator_action]
       # If it's not a private message and it's not an automatic post caused by a moderator action, notify the users
@@ -75,6 +79,22 @@ class PostAlertObserver < ActiveRecord::Observer
       "#{action}_#{model.class.name.underscore.gsub(/.+\//, '')}"
     end
 
+    def first_unread_post(user, topic)
+      Post.where('post_number > COALESCE((
+                 SELECT last_read_post_number FROM topic_users tu
+                 WHERE tu.user_id = ? AND tu.topic_id = ? ),0)',
+                  user.id, topic.id)
+          .order('post_number').first
+    end
+
+    def destroy_notifications(user, type, topic)
+      return if user.blank?
+      return unless Guardian.new(user).can_see?(topic)
+
+      user.notifications.where(notification_type: type,
+                               topic_id: topic.id).destroy_all
+    end
+
     def create_notification(user, type, post, opts={})
       return if user.blank?
 

spec/models/notification_spec.rb

@@ -129,13 +129,17 @@ describe Notification do
       @target = @post.topic.topic_allowed_users.reject{|a| a.user_id == @post.user_id}[0].user
     end
 
-    it 'should create a private message notification' do
+    it 'should create and rollup private message notifications' do
       @target.notifications.first.notification_type.should == Notification.types[:private_message]
+      @post.user.unread_notifications.should == 0
+      @target.unread_private_messages.should == 1
+
+      Fabricate(:post, topic: @topic, user: @topic.user)
+      @target.reload
+      @target.unread_private_messages.should == 1
+
     end
 
-    it 'should not add a pm notification for the creator' do
-      @post.user.unread_notifications.should == 0
-    end
   end
 
   describe '.post' do
@@ -165,7 +169,7 @@ describe Notification do
     it 'correctly updates the read state' do
       user = Fabricate(:user)
 
-      pm = Notification.create!(read: false,
+      Notification.create!(read: false,
                            user_id: user.id,
                            topic_id: 2,
                            post_number: 1,
@@ -192,7 +196,7 @@ describe Notification do
     it "marks multiple posts as read if needed" do
       user = Fabricate(:user)
 
-      notifications = (1..3).map do |i|
+      (1..3).map do |i|
         Notification.create!(read: false, user_id: user.id, topic_id: 2, post_number: i, data: '[]', notification_type: 1)
       end
       Notification.create!(read: true, user_id: user.id, topic_id: 2, post_number: 4, data: '[]', notification_type: 1)