From 0db11884bcdc5a3607d2f22372f7a4985b3d9bae Mon Sep 17 00:00:00 2001
From: Thomas Hille <thomahi@gmx.de>
Date: Sun, 29 Jan 2017 20:26:45 +0100
Subject: [PATCH] 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/controllers/exercises_controller.rb       | 53 +++++++++++-
 app/controllers/proxy_exercises_controller.rb | 80 +++++++++++++++++++
 app/controllers/tags_controller.rb            | 55 +++++++++++++
 app/models/concerns/user.rb                   |  4 +
 app/models/exercise.rb                        | 10 +++
 app/models/exercise_collection.rb             |  5 ++
 app/models/exercise_tag.rb                    | 13 +++
 app/models/intervention.rb                    | 15 ++++
 app/models/proxy_exercise.rb                  | 27 +++++++
 app/models/tag.rb                             | 22 +++++
 app/models/user_exercise_feedback.rb          |  8 ++
 app/models/user_exercise_intervention.rb      | 11 +++
 app/models/user_proxy_exercise_exercise.rb    | 14 ++++
 app/policies/exercise_policy.rb               |  2 +-
 app/policies/proxy_exercise_policy.rb         | 34 ++++++++
 app/policies/tag_policy.rb                    | 34 ++++++++
 app/views/exercises/_editor.html.slim         |  2 +-
 app/views/exercises/_form.html.slim           | 19 +++++
 app/views/exercises/implement.html.slim       |  1 +
 app/views/exercises/index.html.slim           |  6 ++
 app/views/exercises/show.html.slim            |  3 +
 app/views/proxy_exercises/_form.html.slim     | 24 ++++++
 app/views/proxy_exercises/edit.html.slim      |  3 +
 app/views/proxy_exercises/index.html.slim     | 35 ++++++++
 app/views/proxy_exercises/new.html.slim       |  3 +
 .../proxy_exercises/reload.json.jbuilder      |  3 +
 app/views/proxy_exercises/show.html.slim      | 23 ++++++
 app/views/tags/_form.html.slim                |  6 ++
 app/views/tags/edit.html.slim                 |  3 +
 app/views/tags/index.html.slim                | 19 +++++
 app/views/tags/new.html.slim                  |  3 +
 app/views/tags/show.html.slim                 |  6 ++
 config/locales/de.yml                         | 17 ++++
 config/locales/en.yml                         | 17 ++++
 config/routes.rb                              | 17 ++++
 ...70205163247_create_exercise_collections.rb | 14 ++++
 .../20170205165450_create_proxy_exercises.rb  | 23 ++++++
 .../20170205210357_create_interventions.rb    | 16 ++++
 db/migrate/20170206141210_add_tags.rb         | 19 +++++
 .../20170206152503_add_user_feedback.rb       | 11 +++
 40 files changed, 675 insertions(+), 5 deletions(-)
 create mode 100644 app/controllers/proxy_exercises_controller.rb
 create mode 100644 app/controllers/tags_controller.rb
 create mode 100644 app/models/exercise_collection.rb
 create mode 100644 app/models/exercise_tag.rb
 create mode 100644 app/models/intervention.rb
 create mode 100644 app/models/proxy_exercise.rb
 create mode 100644 app/models/tag.rb
 create mode 100644 app/models/user_exercise_feedback.rb
 create mode 100644 app/models/user_exercise_intervention.rb
 create mode 100644 app/models/user_proxy_exercise_exercise.rb
 create mode 100644 app/policies/proxy_exercise_policy.rb
 create mode 100644 app/policies/tag_policy.rb
 create mode 100644 app/views/proxy_exercises/_form.html.slim
 create mode 100644 app/views/proxy_exercises/edit.html.slim
 create mode 100644 app/views/proxy_exercises/index.html.slim
 create mode 100644 app/views/proxy_exercises/new.html.slim
 create mode 100644 app/views/proxy_exercises/reload.json.jbuilder
 create mode 100644 app/views/proxy_exercises/show.html.slim
 create mode 100644 app/views/tags/_form.html.slim
 create mode 100644 app/views/tags/edit.html.slim
 create mode 100644 app/views/tags/index.html.slim
 create mode 100644 app/views/tags/new.html.slim
 create mode 100644 app/views/tags/show.html.slim
 create mode 100644 db/migrate/20170205163247_create_exercise_collections.rb
 create mode 100644 db/migrate/20170205165450_create_proxy_exercises.rb
 create mode 100644 db/migrate/20170205210357_create_interventions.rb
 create mode 100644 db/migrate/20170206141210_add_tags.rb
 create mode 100644 db/migrate/20170206152503_add_user_feedback.rb

diff --git a/app/controllers/exercises_controller.rb b/app/controllers/exercises_controller.rb
index 79314208..f27324ad 100644
--- a/app/controllers/exercises_controller.rb
+++ b/app/controllers/exercises_controller.rb
@@ -6,7 +6,7 @@ class ExercisesController < ApplicationController
 
   before_action :handle_file_uploads, only: [:create, :update]
   before_action :set_execution_environments, only: [:create, :edit, :new, :update]
-  before_action :set_exercise, only: MEMBER_ACTIONS + [:clone, :implement, :run, :statistics, :submit, :reload]
+  before_action :set_exercise, only: MEMBER_ACTIONS + [:clone, :implement, :working_times, :run, :statistics, :submit, :reload]
   before_action :set_external_user, only: [:statistics]
   before_action :set_file_types, only: [:create, :edit, :new, :update]
 
@@ -54,6 +54,20 @@ class ExercisesController < ApplicationController
 
   def create
     @exercise = Exercise.new(exercise_params)
+    collect_set_and_unset_exercise_tags
+    myparam = exercise_params
+    checked_exercise_tags = @exercise_tags.select { | et | myparam[:tag_ids].include? et.tag.id.to_s }
+    removed_exercise_tags = @exercise_tags.reject { | et | myparam[:tag_ids].include? et.tag.id.to_s }
+
+    for et in checked_exercise_tags
+      et.factor = params[:tag_factors][et.tag_id.to_s][:factor]
+      et.exercise = @exercise
+    end
+
+    myparam[:exercise_tags] = checked_exercise_tags
+    myparam.delete :tag_ids
+    removed_exercise_tags.map {|et| et.destroy}
+
     authorize!
     create_and_respond(object: @exercise)
   end
@@ -63,6 +77,7 @@ class ExercisesController < ApplicationController
   end
 
   def edit
+    collect_set_and_unset_exercise_tags
   end
 
   def import_proforma_xml
@@ -118,7 +133,8 @@ class ExercisesController < ApplicationController
   private :user_by_code_harbor_token
 
   def exercise_params
-    params[:exercise].permit(:description, :execution_environment_id, :file_id, :instructions, :public, :hide_file_tree, :allow_file_creation, :allow_auto_completion, :title, files_attributes: file_attributes).merge(user_id: current_user.id, user_type: current_user.class.name)
+    params[:exercise][:expected_worktime_seconds] = params[:exercise][:expected_worktime_minutes].to_i * 60
+    params[:exercise].permit(:description, :execution_environment_id, :file_id, :instructions, :public, :hide_file_tree, :allow_file_creation, :allow_auto_completion, :title, :expected_difficulty, :expected_worktime_seconds, files_attributes: file_attributes, :tag_ids => []).merge(user_id: current_user.id, user_type: current_user.class.name)
   end
   private :exercise_params
 
@@ -150,6 +166,12 @@ class ExercisesController < ApplicationController
     end
   end
 
+  def working_times
+    working_time_accumulated = Time.parse(@exercise.average_working_time_for_only(current_user.id) || "00:00:00").seconds_since_midnight
+    working_time_avg = Time.parse(@exercise.average_working_time || "00:00:00").seconds_since_midnight
+    render(json: {working_time_avg: working_time_avg, working_time_accumulated: working_time_accumulated})
+  end
+
   def index
     @search = policy_scope(Exercise).search(params[:q])
     @exercises = @search.result.includes(:execution_environment, :user).order(:title).paginate(page: params[:page])
@@ -174,6 +196,8 @@ class ExercisesController < ApplicationController
 
   def new
     @exercise = Exercise.new
+    collect_set_and_unset_exercise_tags
+
     authorize!
   end
 
@@ -201,6 +225,16 @@ class ExercisesController < ApplicationController
   end
   private :set_file_types
 
+  def collect_set_and_unset_exercise_tags
+    @search = policy_scope(Tag).search(params[:q])
+    @tags = @search.result.order(:name)
+    exercise_tags = @exercise.exercise_tags
+    tags_set = exercise_tags.collect{|e| e.tag}.to_set
+    tags_not_set = Tag.all.to_set.subtract tags_set
+    @exercise_tags = exercise_tags + tags_not_set.collect { |tag| ExerciseTag.new(exercise: @exercise, tag: tag)}
+  end
+  private :collect_set_and_unset_exercise_tags
+
   def show
   end
 
@@ -252,7 +286,20 @@ class ExercisesController < ApplicationController
   private :transmit_lti_score
 
   def update
-    update_and_respond(object: @exercise, params: exercise_params)
+    collect_set_and_unset_exercise_tags
+    myparam = exercise_params
+    checked_exercise_tags = @exercise_tags.select { | et | myparam[:tag_ids].include? et.tag.id.to_s }
+    removed_exercise_tags = @exercise_tags.reject { | et | myparam[:tag_ids].include? et.tag.id.to_s }
+
+    for et in checked_exercise_tags
+      et.factor = params[:tag_factors][et.tag_id.to_s][:factor]
+      et.exercise = @exercise
+    end
+
+    myparam[:exercise_tags] = checked_exercise_tags
+    myparam.delete :tag_ids
+    removed_exercise_tags.map {|et| et.destroy}
+    update_and_respond(object: @exercise, params: myparam)
   end
 
   def redirect_after_submit
diff --git a/app/controllers/proxy_exercises_controller.rb b/app/controllers/proxy_exercises_controller.rb
new file mode 100644
index 00000000..02fe0220
--- /dev/null
+++ b/app/controllers/proxy_exercises_controller.rb
@@ -0,0 +1,80 @@
+class ProxyExercisesController < ApplicationController
+  include CommonBehavior
+
+  before_action :set_exercise, only: MEMBER_ACTIONS + [:clone, :reload]
+
+  def authorize!
+    authorize(@proxy_exercise || @proxy_exercises)
+  end
+  private :authorize!
+
+  def clone
+    proxy_exercise = @proxy_exercise.duplicate(token: nil, exercises: @proxy_exercise.exercises)
+    proxy_exercise.send(:generate_token)
+    if proxy_exercise.save
+      redirect_to(proxy_exercise, notice: t('shared.object_cloned', model:  ProxyExercise.model_name.human))
+    else
+      flash[:danger] = t('shared.message_failure')
+      redirect_to(@proxy_exercise)
+    end
+  end
+
+  def create
+    myparams = proxy_exercise_params
+    myparams[:exercises] = Exercise.find(myparams[:exercise_ids].reject { |c| c.empty? })
+    @proxy_exercise = ProxyExercise.new(myparams)
+    authorize!
+
+    create_and_respond(object: @proxy_exercise)
+  end
+
+  def destroy
+    destroy_and_respond(object: @proxy_exercise)
+  end
+
+  def edit
+    @search = policy_scope(Exercise).search(params[:q])
+    @exercises = @search.result.order(:title)
+    authorize!
+  end
+
+  def proxy_exercise_params
+    params[:proxy_exercise].permit(:description, :title, :exercise_ids  => [])
+  end
+  private :proxy_exercise_params
+
+  def index
+    @search = policy_scope(ProxyExercise).search(params[:q])
+    @proxy_exercises = @search.result.order(:title).paginate(page: params[:page])
+    authorize!
+  end
+
+  def new
+    @proxy_exercise =  ProxyExercise.new
+    @search = policy_scope(Exercise).search(params[:q])
+    @exercises = @search.result.order(:title)
+    authorize!
+  end
+
+  def set_exercise
+    @proxy_exercise = ProxyExercise.find(params[:id])
+    authorize!
+  end
+  private :set_exercise
+
+  def show
+    @search = @proxy_exercise.exercises.search
+    @exercises = @proxy_exercise.exercises.search.result.order(:title) #@search.result.order(:title)
+  end
+
+  #we might want to think about auth here
+  def reload
+  end
+
+  def update
+    myparams = proxy_exercise_params
+    myparams[:exercises] = Exercise.find(myparams[:exercise_ids].reject { |c| c.blank? })
+    update_and_respond(object: @proxy_exercise, params: myparams)
+  end
+
+end
diff --git a/app/controllers/tags_controller.rb b/app/controllers/tags_controller.rb
new file mode 100644
index 00000000..ff6925dd
--- /dev/null
+++ b/app/controllers/tags_controller.rb
@@ -0,0 +1,55 @@
+class TagsController < ApplicationController
+  include CommonBehavior
+
+  before_action :set_tag, only: MEMBER_ACTIONS
+
+  def authorize!
+    authorize(@tag || @tags)
+  end
+  private :authorize!
+
+  def create
+    @tag = Tag.new(tag_params)
+    authorize!
+    create_and_respond(object: @tag)
+  end
+
+  def destroy
+    destroy_and_respond(object: @tag)
+  end
+
+  def edit
+  end
+
+  def tag_params
+    params[:tag].permit(:name)
+  end
+  private :tag_params
+
+  def index
+    @tags = Tag.all.paginate(page: params[:page])
+    authorize!
+  end
+
+  def new
+    @tag = Tag.new
+    authorize!
+  end
+
+  def set_tag
+    @tag = Tag.find(params[:id])
+    authorize!
+  end
+  private :set_tag
+
+  def show
+  end
+
+  def update
+    update_and_respond(object: @tag, params: tag_params)
+  end
+
+  def to_s
+    name
+  end
+end
diff --git a/app/models/concerns/user.rb b/app/models/concerns/user.rb
index ee72a715..330ccacd 100644
--- a/app/models/concerns/user.rb
+++ b/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
diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index 29f260c2..37e421a7 100644
--- a/app/models/exercise.rb
+++ b/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
diff --git a/app/models/exercise_collection.rb b/app/models/exercise_collection.rb
new file mode 100644
index 00000000..2dca0e9d
--- /dev/null
+++ b/app/models/exercise_collection.rb
@@ -0,0 +1,5 @@
+class ExerciseCollection < ActiveRecord::Base
+
+  has_and_belongs_to_many :exercises
+
+end
\ No newline at end of file
diff --git a/app/models/exercise_tag.rb b/app/models/exercise_tag.rb
new file mode 100644
index 00000000..4b8ab3e5
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/app/models/intervention.rb b/app/models/intervention.rb
new file mode 100644
index 00000000..960a4188
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/app/models/proxy_exercise.rb b/app/models/proxy_exercise.rb
new file mode 100644
index 00000000..1f6d47c1
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/app/models/tag.rb b/app/models/tag.rb
new file mode 100644
index 00000000..002ec687
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/app/models/user_exercise_feedback.rb b/app/models/user_exercise_feedback.rb
new file mode 100644
index 00000000..d3ec09d5
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/app/models/user_exercise_intervention.rb b/app/models/user_exercise_intervention.rb
new file mode 100644
index 00000000..60824c34
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/app/models/user_proxy_exercise_exercise.rb b/app/models/user_proxy_exercise_exercise.rb
new file mode 100644
index 00000000..e7defae6
--- /dev/null
+++ b/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
\ No newline at end of file
diff --git a/app/policies/exercise_policy.rb b/app/policies/exercise_policy.rb
index 55f7d16b..c89ad86a 100644
--- a/app/policies/exercise_policy.rb
+++ b/app/policies/exercise_policy.rb
@@ -16,7 +16,7 @@ class ExercisePolicy < AdminOrAuthorPolicy
     define_method(action) { admin? || author?}
   end
 
-  [:implement?, :submit?, :reload?].each do |action|
+  [:implement?, :working_times?, :submit?, :reload?].each do |action|
     define_method(action) { everyone }
   end
 
diff --git a/app/policies/proxy_exercise_policy.rb b/app/policies/proxy_exercise_policy.rb
new file mode 100644
index 00000000..28de525e
--- /dev/null
+++ b/app/policies/proxy_exercise_policy.rb
@@ -0,0 +1,34 @@
+class ProxyExercisePolicy < AdminOrAuthorPolicy
+  def author?
+    @user == @record.author
+  end
+  private :author?
+
+  def batch_update?
+    admin?
+  end
+
+  def show?
+    @user.internal_user?
+  end
+
+  [:clone?, :destroy?, :edit?, :update?].each do |action|
+    define_method(action) { admin? || author?}
+  end
+
+  [:reload?].each do |action|
+    define_method(action) { everyone }
+  end
+
+  class Scope < Scope
+    def resolve
+      if @user.admin?
+        @scope.all
+      elsif @user.internal_user?
+        @scope.where('user_id = ? OR public = TRUE', @user.id)
+      else
+        @scope.none
+      end
+    end
+  end
+end
diff --git a/app/policies/tag_policy.rb b/app/policies/tag_policy.rb
new file mode 100644
index 00000000..8325b9fa
--- /dev/null
+++ b/app/policies/tag_policy.rb
@@ -0,0 +1,34 @@
+class TagPolicy < AdminOrAuthorPolicy
+  def author?
+    @user == @record.author
+  end
+  private :author?
+
+  def batch_update?
+    admin?
+  end
+
+  def show?
+    @user.internal_user?
+  end
+
+  [:clone?, :destroy?, :edit?, :update?].each do |action|
+    define_method(action) { admin? || author?}
+  end
+
+  [:reload?].each do |action|
+    define_method(action) { everyone }
+  end
+
+  class Scope < Scope
+    def resolve
+      if @user.admin?
+        @scope.all
+      elsif @user.internal_user?
+        @scope.where('user_id = ? OR public = TRUE', @user.id)
+      else
+        @scope.none
+      end
+    end
+  end
+end
diff --git a/app/views/exercises/_editor.html.slim b/app/views/exercises/_editor.html.slim
index 56986673..ff18968c 100644
--- a/app/views/exercises/_editor.html.slim
+++ b/app/views/exercises/_editor.html.slim
@@ -21,4 +21,4 @@
       button style="display:none" id="autosave"
 
 
-= render('shared/modal', id: 'comment-modal', title: t('exercises.implement.comment.request'), template: 'exercises/_request_comment_dialogcontent')
+= render('shared/modal', id: 'comment-modal', title: t('exercises.implement.comment.request'), template: 'exercises/_request_comment_dialogcontent')
\ No newline at end of file
diff --git a/app/views/exercises/_form.html.slim b/app/views/exercises/_form.html.slim
index c4159254..0811b447 100644
--- a/app/views/exercises/_form.html.slim
+++ b/app/views/exercises/_form.html.slim
@@ -32,6 +32,25 @@
     label
       = f.check_box(:allow_auto_completion)
       = t('activerecord.attributes.exercise.allow_auto_completion')
+  .form-group
+    = f.label(t('activerecord.attributes.exercise.difficulty'))
+    = f.number_field :expected_difficulty, in: 1..10, step: 1
+  .form-group
+    = f.label(t('activerecord.attributes.exercise.worktime'))
+    = f.number_field "expected_worktime_minutes", value: @exercise.expected_worktime_seconds / 60, in: 1..1000, step: 1
+  h2 Tags
+  .table-responsive
+    table.table
+      thead
+        tr
+          th = t('activerecord.attributes.exercise.selection')
+          th = sort_link(@search, :title, t('activerecord.attributes.tag.name'))
+          th = t('activerecord.attributes.tag.difficulty')
+        = collection_check_boxes :exercise, :tag_ids, @exercise_tags, :tag_id, :id do |b|
+          tr
+            td = b.check_box
+            td = b.object.tag.name
+            td = number_field "tag_factors[#{b.object.tag.id}]", :factor, :value => b.object.factor, in: 1..10, step: 1
   h2 = t('activerecord.attributes.exercise.files')
   ul#files.list-unstyled.panel-group
     = f.fields_for :files do |files_form|
diff --git a/app/views/exercises/implement.html.slim b/app/views/exercises/implement.html.slim
index 87ff4e1f..300775a6 100644
--- a/app/views/exercises/implement.html.slim
+++ b/app/views/exercises/implement.html.slim
@@ -22,3 +22,4 @@
     #questions-column
       #questions-holder data-url="#{qa_url}/qa/index/#{@exercise.id}/#{@user_id}"
     = qa_js_tag
+
diff --git a/app/views/exercises/index.html.slim b/app/views/exercises/index.html.slim
index 9ad5cc25..bd8fe880 100644
--- a/app/views/exercises/index.html.slim
+++ b/app/views/exercises/index.html.slim
@@ -16,6 +16,9 @@ h1 = Exercise.model_name.human(count: 2)
         th = sort_link(@search, :execution_environment_id, t('activerecord.attributes.exercise.execution_environment'))
         th = t('.test_files')
         th = t('activerecord.attributes.exercise.maximum_score')
+        th = t('activerecord.attributes.exercise.tags')
+        th = t('activerecord.attributes.exercise.difficulty')
+        th = t('activerecord.attributes.exercise.worktime')
         th
           = t('activerecord.attributes.exercise.public')
           - if policy(Exercise).batch_update?
@@ -29,6 +32,9 @@ h1 = Exercise.model_name.human(count: 2)
           td = link_to_if(exercise.execution_environment && policy(exercise.execution_environment).show?, exercise.execution_environment, exercise.execution_environment)
           td = exercise.files.teacher_defined_tests.count
           td = exercise.maximum_score
+          td = exercise.exercise_tags.count
+          td = exercise.expected_difficulty
+          td = (exercise.expected_worktime_seconds / 60).ceil
           td.public data-value=exercise.public? = symbol_for(exercise.public?)
           td = link_to(t('shared.edit'), edit_exercise_path(exercise)) if policy(exercise).edit?
           td = link_to(t('.implement'), implement_exercise_path(exercise)) if policy(exercise).implement?
diff --git a/app/views/exercises/show.html.slim b/app/views/exercises/show.html.slim
index 902f8135..1efbd612 100644
--- a/app/views/exercises/show.html.slim
+++ b/app/views/exercises/show.html.slim
@@ -19,6 +19,9 @@ h1
 = row(label: 'exercise.allow_auto_completion', value: @exercise.allow_auto_completion?)
 = row(label: 'exercise.embedding_parameters') do
   = content_tag(:input, nil, class: 'form-control', readonly: true, value: embedding_parameters(@exercise))
+= row(label: 'exercise.difficulty', value: @exercise.expected_difficulty)
+= row(label: 'exercise.worktime', value: "#{@exercise.expected_worktime_seconds/60} min")
+= row(label: 'exercise.tags', value: @exercise.exercise_tags.map{|et| "#{et.tag.name} (#{et.factor})"}.sort.join(", "))
 
 h2 = t('activerecord.attributes.exercise.files')
 
diff --git a/app/views/proxy_exercises/_form.html.slim b/app/views/proxy_exercises/_form.html.slim
new file mode 100644
index 00000000..bd57bf06
--- /dev/null
+++ b/app/views/proxy_exercises/_form.html.slim
@@ -0,0 +1,24 @@
+= form_for(@proxy_exercise, multipart: true) do |f|
+  = render('shared/form_errors', object: @proxy_exercise)
+  .form-group
+    = f.label(:title)
+    = f.text_field(:title, class: 'form-control', required: true)
+  .form-group
+    = f.label(:description)
+    = f.pagedown_editor :description
+
+  h3 Exercises
+  .table-responsive
+    table.table
+      thead
+        tr
+          th = t('activerecord.attributes.exercise.selection')
+          th = sort_link(@search, :title, t('activerecord.attributes.submission.exercise'))
+          th = sort_link(@search, :created_at, t('shared.created_at'))
+      = collection_check_boxes :proxy_exercise, :exercise_ids, @exercises, :id, :title do |b|
+        tr
+          td = b.check_box
+          td = link_to(b.object, b.object)
+          td = l(b.object.created_at, format: :short)
+
+  .actions = render('shared/submit_button', f: f, object: @proxy_exercise)
\ No newline at end of file
diff --git a/app/views/proxy_exercises/edit.html.slim b/app/views/proxy_exercises/edit.html.slim
new file mode 100644
index 00000000..8aa200c9
--- /dev/null
+++ b/app/views/proxy_exercises/edit.html.slim
@@ -0,0 +1,3 @@
+h1 = t('activerecord.models.proxy_exercise.one', model: ProxyExercise.model_name.human)+ ": " + @proxy_exercise.title
+
+= render('form')
diff --git a/app/views/proxy_exercises/index.html.slim b/app/views/proxy_exercises/index.html.slim
new file mode 100644
index 00000000..2a8067c1
--- /dev/null
+++ b/app/views/proxy_exercises/index.html.slim
@@ -0,0 +1,35 @@
+h1 = ProxyExercise.model_name.human(count: 2)
+
+= render(layout: 'shared/form_filters') do |f|
+  .form-group
+    = f.label(:title_cont, t('activerecord.attributes.proxy_exercise.title'), class: 'sr-only')
+    = f.search_field(:title_cont, class: 'form-control', placeholder: t('activerecord.attributes.proxy_exercise.title'))
+
+.table-responsive
+  table.table
+    thead
+      tr
+        th = sort_link(@search, :title, t('activerecord.attributes.proxy_exercise.title'))
+        th = "Token"
+        th = t('activerecord.attributes.proxy_exercise.files_count')
+        th colspan=6 = t('shared.actions')
+    tbody
+      - @proxy_exercises.each do |proxy_exercise|
+        tr data-id=proxy_exercise.id
+          td = link_to(proxy_exercise.title,proxy_exercise)
+          td = proxy_exercise.token
+          td = proxy_exercise.count_files
+          td = link_to(t('shared.edit'), edit_proxy_exercise_path(proxy_exercise)) if policy(proxy_exercise).edit?
+
+          td
+            .btn-group
+              button.btn.btn-primary-outline.btn-xs.dropdown-toggle data-toggle="dropdown" type="button" = t('shared.actions_button')
+              span.caret
+              span.sr-only Toggle Dropdown
+              ul.dropdown-menu.pull-right role="menu"
+                li = link_to(t('shared.show'), proxy_exercise) if policy(proxy_exercise).show?
+                li = link_to(t('shared.destroy'), proxy_exercise, data: {confirm: t('shared.confirm_destroy')}, method: :delete) if policy(proxy_exercise).destroy?
+                li = link_to(t('.clone'), clone_proxy_exercise_path(proxy_exercise), data: {confirm: t('shared.confirm_destroy')}, method: :post) if policy(proxy_exercise).clone?
+
+= render('shared/pagination', collection: @proxy_exercises)
+p = render('shared/new_button', model: ProxyExercise)
diff --git a/app/views/proxy_exercises/new.html.slim b/app/views/proxy_exercises/new.html.slim
new file mode 100644
index 00000000..ae59a292
--- /dev/null
+++ b/app/views/proxy_exercises/new.html.slim
@@ -0,0 +1,3 @@
+h1 = t('shared.new_model', model: ProxyExercise.model_name.human)
+
+= render('form')
diff --git a/app/views/proxy_exercises/reload.json.jbuilder b/app/views/proxy_exercises/reload.json.jbuilder
new file mode 100644
index 00000000..8e5d4e3c
--- /dev/null
+++ b/app/views/proxy_exercises/reload.json.jbuilder
@@ -0,0 +1,3 @@
+json.set! :files do
+  json.array! @exercise.files.visible, :content, :id
+end
diff --git a/app/views/proxy_exercises/show.html.slim b/app/views/proxy_exercises/show.html.slim
new file mode 100644
index 00000000..c1888d79
--- /dev/null
+++ b/app/views/proxy_exercises/show.html.slim
@@ -0,0 +1,23 @@
+- content_for :head do
+  = javascript_include_tag('http://cdnjs.cloudflare.com/ajax/libs/highlight.js/8.4/highlight.min.js')
+  = stylesheet_link_tag('http://cdnjs.cloudflare.com/ajax/libs/highlight.js/8.4/styles/default.min.css')
+
+h1
+  = @proxy_exercise.title
+  - if policy(@proxy_exercise).edit?
+    = render('shared/edit_button', object: @proxy_exercise)
+
+= row(label: 'exercise.title', value: @proxy_exercise.title)
+= row(label: 'proxy_exercise.files_count', value: @exercises.count)
+= row(label: 'exercise.description', value: @proxy_exercise.description)
+h3 Exercises
+.table-responsive
+  table.table
+    thead
+      tr
+        th = sort_link(@search, :title, t('activerecord.attributes.submission.exercise'))
+        th = sort_link(@search, :created_at, t('shared.created_at'))
+    - @proxy_exercise.exercises.each do |exercise|
+      tr
+        td = link_to(exercise.title, exercise)
+        td = l(exercise.created_at, format: :short)
diff --git a/app/views/tags/_form.html.slim b/app/views/tags/_form.html.slim
new file mode 100644
index 00000000..4f02a28f
--- /dev/null
+++ b/app/views/tags/_form.html.slim
@@ -0,0 +1,6 @@
+= form_for(@tag) do |f|
+  = render('shared/form_errors', object: @tag)
+  .form-group
+    = f.label(:name)
+    = f.text_field(:name, class: 'form-control', required: true)
+  .actions = render('shared/submit_button', f: f, object: @tag)
diff --git a/app/views/tags/edit.html.slim b/app/views/tags/edit.html.slim
new file mode 100644
index 00000000..23c76720
--- /dev/null
+++ b/app/views/tags/edit.html.slim
@@ -0,0 +1,3 @@
+h1 = @tag.name
+
+= render('form')
diff --git a/app/views/tags/index.html.slim b/app/views/tags/index.html.slim
new file mode 100644
index 00000000..2d4916af
--- /dev/null
+++ b/app/views/tags/index.html.slim
@@ -0,0 +1,19 @@
+h1 = Tag.model_name.human(count: 2)
+
+.table-responsive
+  table.table
+    thead
+      tr
+        th = t('activerecord.attributes.hint.name')
+        /th = t('activerecord.attributes.hint.locale')
+        /th colspan=3 = t('shared.actions')
+    tbody
+      - @tags.each do |tag|
+        tr
+          td = tag.name
+          td = link_to(t('shared.show'), tag)
+          td = link_to(t('shared.edit'), edit_tag_path(tag))
+          td = link_to(t('shared.destroy'), tag, data: {confirm: t('shared.confirm_destroy')}, method: :delete) if tag.can_be_destroyed?
+
+= render('shared/pagination', collection: @tags)
+p = render('shared/new_button', model: Tag, path: new_tag_path)
diff --git a/app/views/tags/new.html.slim b/app/views/tags/new.html.slim
new file mode 100644
index 00000000..a933bede
--- /dev/null
+++ b/app/views/tags/new.html.slim
@@ -0,0 +1,3 @@
+h1 = t('shared.new_model', model: Hint.model_name.human)
+
+= render('form')
diff --git a/app/views/tags/show.html.slim b/app/views/tags/show.html.slim
new file mode 100644
index 00000000..81eda745
--- /dev/null
+++ b/app/views/tags/show.html.slim
@@ -0,0 +1,6 @@
+h1
+  = @tag.name
+  = render('shared/edit_button', object: @tag)
+
+= row(label: 'tag.name', value: @tag.name)
+= row(label: 'tag.usage', value: @tag.exercises.count)
diff --git a/config/locales/de.yml b/config/locales/de.yml
index 5b4329df..09c6932c 100644
--- a/config/locales/de.yml
+++ b/config/locales/de.yml
@@ -27,6 +27,7 @@ de:
       exercise:
         description: Beschreibung
         embedding_parameters: Parameter für LTI-Einbettung
+        tags: Tags
         execution_environment: Ausführungsumgebung
         execution_environment_id: Ausführungsumgebung
         files: Dateien
@@ -34,10 +35,16 @@ de:
         instructions: Anweisungen
         maximum_score: Erreichbare Punktzahl
         public: Öffentlich
+        selection: Ausgewählt
         title: Titel
         user: Autor
         allow_auto_completion: "Autovervollständigung aktivieren"
         allow_file_creation: "Dateierstellung erlauben"
+        difficulty: Schwierigkeitsgrad
+        worktime: "vermutete Arbeitszeit in Minuten"
+      proxy_exercise:
+        title: Title
+        files_count: Anzahl der Aufgaben
       external_user:
         consumer: Konsument
         email: E-Mail
@@ -91,6 +98,10 @@ de:
         files: Dateien
         score: Punktzahl
         user: Autor
+      tag:
+        name: Name
+        usage: Verwendet
+        difficulty: Anteil an der Aufgabe
       file_template:
         name: "Name"
         file_type: "Dateityp"
@@ -111,6 +122,9 @@ de:
       exercise:
         one: Aufgabe
         other: Aufgaben
+      proxy_exercise:
+        one: Proxy Aufgabe
+        other: Proxy Aufgaben
       external_user:
         one: Externer Nutzer
         other: Externe Nutzer
@@ -290,6 +304,9 @@ de:
         tests: Unit Tests
         time_difference: 'Arbeitszeit bis hier*'
         addendum: '* Differenzen von mehr als 30 Minuten werden ignoriert.'
+  proxy_exercises:
+      index:
+        clone: Duplizieren
   external_users:
     statistics:
       title: Statistiken für Externe Benutzer
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 5541d68f..e3c0bc6f 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -48,6 +48,7 @@ en:
       exercise:
         description: Description
         embedding_parameters: LTI Embedding Parameters
+        tags: Tags
         execution_environment: Execution Environment
         execution_environment_id: Execution Environment
         files: Files
@@ -55,10 +56,16 @@ en:
         instructions: Instructions
         maximum_score: Maximum Score
         public: Public
+        selection: Selected
         title: Title
         user: Author
         allow_auto_completion: "Allow auto completion"
         allow_file_creation: "Allow file creation"
+        difficulty: Difficulty
+        worktime: "Expected worktime in minutes"
+      proxy_exercise:
+        title: Title
+        files_count: Exercises Count
       external_user:
         consumer: Consumer
         email: Email
@@ -112,6 +119,10 @@ en:
         files: Files
         score: Score
         user: Author
+      tag:
+        name: Name
+        usage: Used
+        difficulty: Share on the Exercise
       file_template:
         name: "Name"
         file_type: "File Type"
@@ -132,6 +143,9 @@ en:
       exercise:
         one: Exercise
         other: Exercises
+      proxy_exercise:
+        one: Proxy Exercise
+        other: Proxy Exercises
       external_user:
         one: External User
         other: External Users
@@ -311,6 +325,9 @@ en:
         tests: Unit Test Results
         time_difference: 'Working Time until here*'
         addendum: '* Deltas longer than 30 minutes are ignored.'
+  proxy_exercises:
+      index:
+        clone: Duplicate
   external_users:
     statistics:
       title: External User Statistics
diff --git a/config/routes.rb b/config/routes.rb
index b4606f74..87cde74c 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -60,12 +60,29 @@ Rails.application.routes.draw do
     member do
       post :clone
       get :implement
+      get :working_times
       get :statistics
       get :reload
       post :submit
     end
   end
 
+  resources :proxy_exercises do
+    member do
+      post :clone
+      get :reload
+      post :submit
+    end
+  end
+
+  resources :tags do
+    member do
+      post :clone
+      get :reload
+      post :submit
+    end
+  end
+
   resources :external_users, only: [:index, :show], concerns: :statistics do
     resources :exercises, concerns: :statistics
   end
diff --git a/db/migrate/20170205163247_create_exercise_collections.rb b/db/migrate/20170205163247_create_exercise_collections.rb
new file mode 100644
index 00000000..ef27f756
--- /dev/null
+++ b/db/migrate/20170205163247_create_exercise_collections.rb
@@ -0,0 +1,14 @@
+class CreateExerciseCollections < ActiveRecord::Migration
+  def change
+    create_table :exercise_collections do |t|
+      t.string :name
+      t.timestamps
+    end
+
+    create_table :exercise_collections_exercises, id: false do |t|
+      t.belongs_to :exercise_collection, index: true
+      t.belongs_to :exercise, index: true
+    end
+
+  end
+end
diff --git a/db/migrate/20170205165450_create_proxy_exercises.rb b/db/migrate/20170205165450_create_proxy_exercises.rb
new file mode 100644
index 00000000..fb2704ce
--- /dev/null
+++ b/db/migrate/20170205165450_create_proxy_exercises.rb
@@ -0,0 +1,23 @@
+class CreateProxyExercises < ActiveRecord::Migration
+  def change
+    create_table :proxy_exercises do |t|
+      t.string :title
+      t.string :description
+      t.string :token
+      t.timestamps
+    end
+
+    create_table :exercises_proxy_exercises, id: false do |t|
+      t.belongs_to :proxy_exercise, index: true
+      t.belongs_to :exercise, index: true
+      t.timestamps
+    end
+
+    create_table :user_proxy_exercise_exercises do |t|
+      t.belongs_to :user, polymorphic: true, index: true
+      t.belongs_to :proxy_exercise, index: true
+      t.belongs_to :exercise, index: true
+      t.timestamps
+    end
+  end
+end
diff --git a/db/migrate/20170205210357_create_interventions.rb b/db/migrate/20170205210357_create_interventions.rb
new file mode 100644
index 00000000..1b7a8121
--- /dev/null
+++ b/db/migrate/20170205210357_create_interventions.rb
@@ -0,0 +1,16 @@
+class CreateInterventions < ActiveRecord::Migration
+  def change
+    create_table :user_exercise_interventions do |t|
+      t.belongs_to :user, polymorphic: true
+      t.belongs_to :exercise
+      t.belongs_to :intervention
+      t.timestamps
+    end
+
+    create_table :interventions do |t|
+      t.string :name
+      t.text :markup
+      t.timestamps
+    end
+  end
+end
diff --git a/db/migrate/20170206141210_add_tags.rb b/db/migrate/20170206141210_add_tags.rb
new file mode 100644
index 00000000..fd95b4dc
--- /dev/null
+++ b/db/migrate/20170206141210_add_tags.rb
@@ -0,0 +1,19 @@
+class AddTags < ActiveRecord::Migration
+
+  def change
+    add_column :exercises, :expected_worktime_seconds, :integer, default: 0
+    add_column :exercises, :expected_difficulty, :integer, default: 1
+
+    create_table :tags do |t|
+      t.string :name, null: false
+      t.timestamps
+    end
+
+    create_table :exercise_tags do |t|
+      t.belongs_to :exercise
+      t.belongs_to :tag
+      t.integer :factor, default: 0
+    end
+  end
+
+end
diff --git a/db/migrate/20170206152503_add_user_feedback.rb b/db/migrate/20170206152503_add_user_feedback.rb
new file mode 100644
index 00000000..f62ccd9d
--- /dev/null
+++ b/db/migrate/20170206152503_add_user_feedback.rb
@@ -0,0 +1,11 @@
+class AddUserFeedback < ActiveRecord::Migration
+  def change
+    create_table :user_exercise_feedbacks do |t|
+      t.belongs_to :exercise, null: false
+      t.belongs_to :user, polymorphic: true, null: false
+      t.integer :difficulty
+      t.integer :working_time_seconds
+      t.string :feedback_text
+    end
+  end
+end