Grading Period Grade join table - MGP

fixes CNVS-16454

test plan:
 * test in the console
 - `GradingPeriodGrade.all` should return `[]` (no error)
 - `Enrollment.find(1).grading_period_grades` should return `[]` (no error)
 - make a GradingPeriod:
   `g = GradingPeriod.create(weight: 100, start_date: Time.now, end_date: 1.month.from_now)`
   `g.save!`
 - `g.grading_period_grades` should return `[]` (no error)

Change-Id: I7183d715dbfac3fcd89ab7e453237ad4ce6c650d
Reviewed-on: https://gerrit.instructure.com/45312
Product-Review: Cameron Sutter <csutter@instructure.com>
Reviewed-by: Nick Cloward <ncloward@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>

app/models/enrollment.rb

@@ -40,6 +40,7 @@ class Enrollment < ActiveRecord::Base
   has_many :role_overrides, :as => :context
   has_many :pseudonyms, :primary_key => :user_id, :foreign_key => :user_id
   has_many :course_account_associations, :foreign_key => 'course_id', :primary_key => 'course_id'
+  has_many :grading_period_grades
 
   EXPORTABLE_ATTRIBUTES = [
     :id, :user_id, :course_id, :type, :uuid, :workflow_state, :created_at, :updated_at, :associated_user_id, :sis_source_id, :sis_batch_id, :start_at, :end_at,

app/models/grading_period.rb

@@ -3,13 +3,14 @@ class GradingPeriod < ActiveRecord::Base
   include Workflow
 
   belongs_to :grading_period_group, :inverse_of => :grading_periods
+  has_many :grading_period_grades
 
   validates_presence_of :weight, :start_date, :end_date
   validate :validate_dates
 
   set_policy do
     [:read, :update, :create, :delete].each do |permission|
-      given { |user, http_session| grading_period_group.grants_right?(user, http_session, permission) }
+      given { |user| grading_period_group.grants_right?(user, permission) }
       can permission
     end
   end

app/models/grading_period_grade.rb

@@ -0,0 +1,15 @@
+class GradingPeriodGrade < ActiveRecord::Base
+  #TODO: when we create a controller for this, remove attr_accessible and use strong params instead
+  attr_accessible :enrollment_id, :grading_period_id, :current_grade, :final_grade
+  belongs_to :enrollment
+  belongs_to :grading_period
+
+  validates :enrollment_id, :grading_period_id, presence: true
+
+  set_policy do
+    [:read, :update, :create, :delete].each do |permission|
+      given { |user| grading_period.grants_right?(user, permission) }
+      can permission
+    end
+  end
+end

app/models/grading_period_group.rb

@@ -5,15 +5,15 @@ class GradingPeriodGroup < ActiveRecord::Base
 
   # Naive permissions, need to be fleshed out
   set_policy do
-    given { |user, http_session| (course || account).grants_right?(user, http_session, :read) }
+    given { |user| (course || account).grants_right?(user, :read) }
     can :read
 
-    given do |user, http_session|
+    given do |user|
       return false unless (course || account).root_account.feature_enabled?(:multiple_grading_periods)
       if course
-        course.grants_right?(user, http_session, :update)
+        course.grants_right?(user, :update)
       elsif account
-        account.grants_right?(user, http_session, :manage_courses)
+        account.grants_right?(user, :manage_courses)
       end
     end
     can :read and can :update and can :create and can :delete

db/migrate/20141204222243_create_grading_period_grades_join_table.rb

@@ -0,0 +1,18 @@
+class CreateGradingPeriodGradesJoinTable < ActiveRecord::Migration
+  tag :predeploy
+
+  def change
+    create_table :grading_period_grades do |t|
+      t.integer :enrollment_id, :limit => 8
+      t.integer :grading_period_id, :limit => 8
+      t.float :current_grade
+      t.float :final_grade
+      t.timestamps
+    end
+
+    add_foreign_key :grading_period_grades, :enrollments
+    add_foreign_key :grading_period_grades, :grading_periods
+    add_index :grading_period_grades, :enrollment_id
+    add_index :grading_period_grades, :grading_period_id
+  end
+end