FIX: Acting and undoing repeatedly was broken

app/models/post_action.rb

@@ -131,20 +131,36 @@ class PostAction < ActiveRecord::Base
       post.topic.posts_count != 1
     end
 
-    post_action = create( post_id: post.id,
+    where_attrs = {
+      post_id: post.id,
       user_id: user.id,
-                          post_action_type_id: post_action_type_id,
+      post_action_type_id: post_action_type_id
+    }
+
+    action_attributes = {
       message: opts[:message],
       staff_took_action: opts[:take_action] || false,
       related_post_id: related_post_id,
-                          targets_topic: !!targets_topic )
+      targets_topic: !!targets_topic
+    }
 
+    # First try to revive a trashed record
+    row_count = PostAction.where(where_attrs)
+      .with_deleted
+      .where("deleted_at IS NOT NULL")
+      .update_all(action_attributes.merge(deleted_at: nil))
+
+    if row_count == 0
+      post_action = create(where_attrs.merge(action_attributes))
       if post_action && post_action.is_like?
         BadgeGranter.update_badges(action: :post_like, post_id: post.id)
       end
+    else
+      post_action = PostAction.where(where_attrs).first
+      post_action.update_counters
+    end
 
     post_action
-
   rescue ActiveRecord::RecordNotUnique
     # can happen despite being .create
     # since already bookmarked

spec/models/post_action_spec.rb

@@ -175,6 +175,19 @@ describe PostAction do
     end
   end
 
+  describe "undo/redo repeatedly" do
+    it "doesn't create a second action for the same user/type" do
+      PostAction.act(codinghorror, post, PostActionType.types[:like])
+      PostAction.remove_act(codinghorror, post, PostActionType.types[:like])
+      PostAction.act(codinghorror, post, PostActionType.types[:like])
+      PostAction.where(post: post).with_deleted.count.should == 1
+      PostAction.remove_act(codinghorror, post, PostActionType.types[:like])
+
+      # Check that we don't lose consistency into negatives
+      post.reload.like_count.should == 0
+    end
+  end
+
   describe 'when a user votes for something' do
     it 'should increase the vote counts when a user votes' do
       lambda {