Extended Exercises by worktime, difficulty and tags, added ProxyExercises as prework for recommendations

Tags can be added to exercises in the edit view. Tags can monitored under /tags.
Added the concept of ProxyExercises which are a collection of Exercises. They can be found under /proxy_exercises
Added Interventions as prework to show interventions later to the user.
Added exercise/[:id]/working_time to return the working time of the user in this exercise and the average working time of all users in this exercise

app/models/concerns/user.rb

@@ -8,6 +8,10 @@ module User
     has_many :exercises, as: :user
     has_many :file_types, as: :user
     has_many :submissions, as: :user
+    has_many :user_proxy_exercise_exercises, as: :user
+    has_many :user_exercise_interventions, as: :user
+    has_many :interventions, through: :user_exercise_interventions
+
 
     scope :with_submissions, -> { where('id IN (SELECT user_id FROM submissions)') }
   end

app/models/exercise.rb

@@ -12,6 +12,15 @@ class Exercise < ActiveRecord::Base
   belongs_to :execution_environment
   has_many :submissions
 
+  has_and_belongs_to_many :proxy_exercises
+  has_many :user_proxy_exercise_exercises
+  has_and_belongs_to_many :exercise_collections
+  has_many :user_exercise_interventions
+  has_many :interventions, through: :user_exercise_interventions
+  has_many :exercise_tags
+  has_many :tags, through: :exercise_tags
+  accepts_nested_attributes_for :exercise_tags
+
   has_many :external_users, source: :user, source_type: ExternalUser, through: :submissions
   has_many :internal_users, source: :user, source_type: InternalUser, through: :submissions
   alias_method :users, :external_users
@@ -105,6 +114,7 @@ class Exercise < ActiveRecord::Base
   def duplicate(attributes = {})
     exercise = dup
     exercise.attributes = attributes
+    exercise_tags.each  { |et| exercise.exercise_tags << et.dup }
     files.each { |file| exercise.files << file.dup }
     exercise
   end

app/models/exercise_collection.rb

@@ -0,0 +1,5 @@
+class ExerciseCollection < ActiveRecord::Base
+
+  has_and_belongs_to_many :exercises
+
+end

app/models/exercise_tag.rb

@@ -0,0 +1,13 @@
+class ExerciseTag < ActiveRecord::Base
+
+  belongs_to :tag
+  belongs_to :exercise
+
+  before_save :destroy_if_empty_exercise_or_tag
+
+  private
+  def destroy_if_empty_exercise_or_tag
+     destroy if exercise_id.blank? || tag_id.blank?
+  end
+
+end

app/models/intervention.rb

@@ -0,0 +1,15 @@
+class Intervention < ActiveRecord::Base
+
+  NAME = %w(overallSlower longSession syntaxErrors videoNotWatched)
+
+  has_many :user_exercise_interventions
+  has_many :users, through: :user_exercise_interventions, source_type: "ExternalUser"
+  #belongs_to :user, polymorphic: true
+  #belongs_to :external_users, source: :user, source_type: ExternalUser
+  #belongs_to :internal_users, source: :user, source_type: InternalUser, through: :user_interventions
+ # alias_method :users, :external_users
+  #has_many :exercises, through: :user_interventions
+
+  validates :name, inclusion: {in: NAME}
+
+end

app/models/proxy_exercise.rb

@@ -0,0 +1,27 @@
+class ProxyExercise < ActiveRecord::Base
+
+    after_initialize :generate_token
+
+    has_and_belongs_to_many :exercises
+    has_many :user_proxy_exercise_exercises
+
+    def count_files
+        exercises.count
+    end
+
+    def generate_token
+      self.token ||= SecureRandom.hex(4)
+    end
+    private :generate_token
+
+    def duplicate(attributes = {})
+      proxy_exercise = dup
+      proxy_exercise.attributes = attributes
+      proxy_exercise
+    end
+
+    def to_s
+      title
+    end
+
+end

app/models/tag.rb

@@ -0,0 +1,22 @@
+class Tag < ActiveRecord::Base
+
+  has_many :exercise_tags
+  has_many :exercises, through: :exercise_tags
+
+  validates_uniqueness_of :name
+
+  def destroy
+    if (can_be_destroyed?)
+      super
+    end
+  end
+
+  def can_be_destroyed?
+    !exercises.any?
+  end
+
+  def to_s
+    name
+  end
+
+end

app/models/user_exercise_feedback.rb

@@ -0,0 +1,8 @@
+class UserExerciseFeedback < ActiveRecord::Base
+
+  belongs_to :user, polymorphic: true
+  belongs_to :exercise
+
+  validates :user_id, uniqueness: { scope: [:exercise_id, :user_type] }
+
+end

app/models/user_exercise_intervention.rb

@@ -0,0 +1,11 @@
+class UserExerciseIntervention < ActiveRecord::Base
+
+  belongs_to :user, polymorphic: true
+  belongs_to :intervention
+  belongs_to :exercise
+
+  validates :user, presence: true
+  validates :exercise, presence: true
+  validates :intervention, presence: true
+
+end

app/models/user_proxy_exercise_exercise.rb

@@ -0,0 +1,14 @@
+class UserProxyExerciseExercise < ActiveRecord::Base
+
+  belongs_to :user, polymorphic: true
+  belongs_to :exercise
+  belongs_to :proxy_exercise
+
+  validates :user_id, presence: true
+  validates :user_type, presence: true
+  validates :exercise_id, presence: true
+  validates :proxy_exercise_id, presence: true
+
+  validates :user_id, uniqueness: { scope: [:proxy_exercise_id, :user_type] }
+
+end