Continue adding problem sheets

app/models/lecture.rb

@@ -9,6 +9,8 @@ class Lecture < ApplicationRecord
     :problems_class,
   ], default: :lecture
 
+  include Trackable
+
   def prepared?
     tracked_time_entries.where(kind: [:preparation]).any?
   end
@@ -25,10 +27,6 @@ class Lecture < ApplicationRecord
     tracked_time_entries.preparation.sum(&:duration).seconds
   end
 
-  def total_overall_time
-    tracked_time_entries.sum(&:duration).seconds
-  end
-
   def total_attendance_time
     tracked_time_entries.where(kind: [:concurrent, :catchup]).sum(&:duration).seconds
   end

app/models/tracked_time_entry.rb

@@ -6,7 +6,9 @@ class TrackedTimeEntry < ApplicationRecord
     :catchup,
 
     :preparation,
-    :review
+    :review,
+
+    :generic
   ]
 
   def duration

app/models/work_item.rb

@@ -2,6 +2,16 @@ class WorkItem < ApplicationRecord
   belongs_to :course
   has_many :tracked_time_entries, dependent: :destroy, as: :subject
 
+  validate :due_date_after_start_date
+
+  include Trackable
+
+  def due_date_after_start_date
+    if due_date.present? && start_time.present? && due_date < start_time
+      errors.add(:due_date, "can't be before start date")
+    end
+  end
+
   def week_number
     ((start_time.beginning_of_week - course.semester_start_date.to_time) / 1.week).floor + 1
   end