Add StudyGroups with ExternalUsers only

app/controllers/concerns/lti.rb

@@ -52,6 +52,11 @@ module Lti
   end
   private :external_user_name
 
+  def mooc_course
+    # All Xikolo platforms set the custom_course to the course code
+   params[:custom_course]
+  end
+
   def refuse_lti_launch(options = {})
     return_to_consumer(lti_errorlog: options[:message], lti_errormsg: t('sessions.oauth.failure'))
   end
@@ -133,6 +138,13 @@ module Lti
   end
   private :set_current_user
 
+  def set_study_group_membership
+    return if mooc_course
+    group = StudyGroup.find_or_create_by(external_id: @provider.resource_link_id, consumer: @consumer)
+    group.users |= [@current_user] # add current user if not already member of the group
+    group.save
+  end
+
   def store_lti_session_data(options = {})
     lti_parameters = LtiParameter.find_or_create_by(consumers_id: options[:consumer].id,
                                                     external_users_id: @current_user.id,

app/controllers/sessions_controller.rb

@@ -1,7 +1,7 @@
 class SessionsController < ApplicationController
   include Lti
 
-  [:require_oauth_parameters, :require_valid_consumer_key, :require_valid_oauth_signature, :require_unique_oauth_nonce, :set_current_user, :require_valid_exercise_token].each do |method_name|
+  [:require_oauth_parameters, :require_valid_consumer_key, :require_valid_oauth_signature, :require_unique_oauth_nonce, :set_current_user, :set_study_group_membership, :require_valid_exercise_token].each do |method_name|
     before_action(method_name, only: :create_through_lti)
   end
 

app/models/external_user.rb

@@ -4,11 +4,11 @@ class ExternalUser < User
   validates :external_id, presence: true
 
   def displayname
-    result = name
+    if name.blank?
-    if(result == nil || result == "")
+      "User " + id.to_s
-      result = "User " + id.to_s
+    else
+      name
     end
-    result
   end
 
 end

app/models/study_group.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class StudyGroup < ApplicationRecord
+  has_many :study_group_memberships
+  # Use `ExternalUser` as `source_type` for now.
+  # Using `User` will lead ActiveRecord to access the inexistent table `users`.
+  # Issue created: https://github.com/rails/rails/issues/34531
+  has_many :users, through: :study_group_memberships, source_type: 'ExternalUser'
+  has_many :submissions
+  belongs_to :consumer
+end

app/models/study_group_membership.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class StudyGroupMembership < ApplicationRecord
+  belongs_to :user, polymorphic: true
+  belongs_to :study_group
+
+  validates_uniqueness_of :user_id, :scope => [:user_type, :study_group_id]
+end

app/models/submission.rb

@@ -6,6 +6,7 @@ class Submission < ApplicationRecord
   FILENAME_URL_PLACEHOLDER = '{filename}'
 
   belongs_to :exercise
+  belongs_to :study_group, optional: true
 
   has_many :testruns
   has_many :structured_errors

app/models/user.rb

@@ -4,6 +4,8 @@ class User < ApplicationRecord
   ROLES = %w(admin teacher)
 
   belongs_to :consumer
+  has_many :study_group_memberships, as: :user
+  has_many :study_groups, through: :study_group_memberships, as: :user
   has_many :exercises, as: :user
   has_many :file_types, as: :user
   has_many :submissions, as: :user

db/migrate/20181122084546_create_study_groups.rb

@@ -0,0 +1,13 @@
+class CreateStudyGroups < ActiveRecord::Migration[5.2]
+  def change
+    create_table :study_groups do |t|
+      t.string :name
+      t.string :external_id
+      t.belongs_to :consumer
+      t.timestamps
+    end
+
+    add_index :study_groups, [:external_id, :consumer_id], unique: true
+  end
+end
+

db/migrate/20181122090243_create_study_group_memberships.rb

@@ -0,0 +1,8 @@
+class CreateStudyGroupMemberships < ActiveRecord::Migration[5.2]
+  def change
+    create_table :study_group_memberships do |t|
+      t.belongs_to :study_group
+      t.belongs_to :user, polymorphic: true
+    end
+  end
+end

db/migrate/20181122090244_add_study_group_to_submission.rb

@@ -0,0 +1,5 @@
+class AddStudyGroupToSubmission < ActiveRecord::Migration[5.2]
+  def change
+    add_reference :submissions, :study_group, index: true, null: true, foreign_key: true
+  end
+end

db/schema.rb

@@ -315,6 +315,24 @@ ActiveRecord::Schema.define(version: 2018_11_29_093207) do
     t.index ["submission_id"], name: "index_structured_errors_on_submission_id"
   end
 
+  create_table "study_group_memberships", force: :cascade do |t|
+    t.bigint "study_group_id"
+    t.string "user_type"
+    t.bigint "user_id"
+    t.index ["study_group_id"], name: "index_study_group_memberships_on_study_group_id"
+    t.index ["user_type", "user_id"], name: "index_study_group_memberships_on_user_type_and_user_id"
+  end
+
+  create_table "study_groups", force: :cascade do |t|
+    t.string "name"
+    t.string "external_id"
+    t.bigint "consumer_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["consumer_id"], name: "index_study_groups_on_consumer_id"
+    t.index ["external_id", "consumer_id"], name: "index_study_groups_on_external_id_and_consumer_id", unique: true
+  end
+
   create_table "submissions", force: :cascade do |t|
     t.integer "exercise_id"
     t.float "score"
@@ -323,7 +341,9 @@ ActiveRecord::Schema.define(version: 2018_11_29_093207) do
     t.datetime "updated_at"
     t.string "cause", limit: 255
     t.string "user_type", limit: 255
+    t.bigint "study_group_id"
     t.index ["exercise_id"], name: "index_submissions_on_exercise_id"
+    t.index ["study_group_id"], name: "index_submissions_on_study_group_id"
     t.index ["user_id"], name: "index_submissions_on_user_id"
   end
 

spec/controllers/sessions_controller_spec.rb

@@ -66,7 +66,7 @@ describe SessionsController do
       it 'refuses the LTI launch' do
         expect_any_instance_of(IMS::LTI::ToolProvider).to receive(:valid_request?).and_return(true)
         expect(controller).to receive(:refuse_lti_launch).with(message: I18n.t('sessions.oauth.invalid_exercise_token')).and_call_original
-        post :create_through_lti, params: { custom_token: '', oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex }
+        post :create_through_lti, params: { custom_token: '', oauth_consumer_key: consumer.oauth_key, oauth_nonce: nonce, oauth_signature: SecureRandom.hex, user_id: '123' }
       end
     end