Recover usage of Todos counter cache

We’re being kept up to date the counter data but we’re not using it.
The only thing which is not real if is the number of projects that the 
user read changes the number of todos can be stale for some time.

The counters will be sync just after the user receives a new todo or mark any as done

app/controllers/dashboard/todos_controller.rb

@@ -37,8 +37,8 @@ class Dashboard::TodosController < Dashboard::ApplicationController
 
   def todos_counts
     {
-      count: TodosFinder.new(current_user, state: :pending).execute.count,
-      done_count: TodosFinder.new(current_user, state: :done).execute.count
+      count: current_user.todos_pending_count,
+      done_count: current_user.todos_done_count
     }
   end
 end

app/helpers/todos_helper.rb

 module TodosHelper
   def todos_pending_count
-    @todos_pending_count ||= TodosFinder.new(current_user, state: :pending).execute.count
+    @todos_pending_count ||= current_user.todos_pending_count
   end
 
   def todos_done_count
-    @todos_done_count ||= TodosFinder.new(current_user, state: :done).execute.count
+    @todos_done_count ||= current_user.todos_done_count
   end
 
   def todo_action_name(todo)

app/services/todo_service.rb

@@ -144,8 +144,9 @@ class TodoService
   def mark_todos_as_done(todos, current_user)
     todos = current_user.todos.where(id: todos.map(&:id)) unless todos.respond_to?(:update_all)
 
-    todos.update_all(state: :done)
+    marked_todos = todos.update_all(state: :done)
     current_user.update_todos_count_cache
+    marked_todos
   end
 
   # When user marks an issue as todo

lib/api/todos.rb

@@ -61,9 +61,9 @@ module API
       #
       delete ':id' do
         todo = current_user.todos.find(params[:id])
-        todo.done
+        TodoService.new.mark_todos_as_done([todo], current_user)
 
-        present todo, with: Entities::Todo, current_user: current_user
+        present todo.reload, with: Entities::Todo, current_user: current_user
       end
 
       # Mark all todos as done
@@ -74,8 +74,6 @@ module API
       delete do
         todos = find_todos
         TodoService.new.mark_todos_as_done(todos, current_user)
-
-        todos.length
       end
     end
   end

spec/services/todo_service_spec.rb

@@ -472,6 +472,42 @@ describe TodoService, services: true do
     expect(john_doe.todos_pending_count).to eq(1)
   end
 
+  describe '#mark_todos_as_done' do
+    let(:issue) { create(:issue, project: project, author: author, assignee: john_doe) }
+
+    it 'marks a relation of todos as done' do
+      create(:todo, :mentioned, user: john_doe, target: issue, project: project)
+
+      todos = TodosFinder.new(john_doe, {}).execute
+      expect { TodoService.new.mark_todos_as_done(todos, john_doe) }
+       .to change { john_doe.todos.done.count }.from(0).to(1)
+    end
+
+    it 'marks an array of todos as done' do
+      todo = create(:todo, :mentioned, user: john_doe, target: issue, project: project)
+
+      expect { TodoService.new.mark_todos_as_done([todo], john_doe) }
+        .to change { todo.reload.state }.from('pending').to('done')
+    end
+
+    it 'returns the number of updated todos' do # Needed on API
+      todo = create(:todo, :mentioned, user: john_doe, target: issue, project: project)
+
+      expect(TodoService.new.mark_todos_as_done([todo], john_doe)).to eq(1)
+    end
+
+    it 'caches the number of todos of a user', :caching do
+      create(:todo, :mentioned, user: john_doe, target: issue, project: project)
+      todo = create(:todo, :mentioned, user: john_doe, target: issue, project: project)
+      TodoService.new.mark_todos_as_done([todo], john_doe)
+
+      expect_any_instance_of(TodosFinder).not_to receive(:execute)
+
+      expect(john_doe.todos_done_count).to eq(1)
+      expect(john_doe.todos_pending_count).to eq(1)
+    end
+  end
+
   def should_create_todo(attributes = {})
     attributes.reverse_merge!(
       project: project,