Prevent deletion of course which has ClassSchedules or ExaminationRes…

…ults

app/controllers/courses_controller.rb

@@ -49,9 +49,36 @@ def update
   end
 
   def destroy
-    @course.destroy.destroyed?
-
-    respond_with(@course)
+    errors = []
+
+    if @course.class_schedules_count.positive?
+      errors << t(
+        'courses.destroy.remove_class_schedules_first',
+        class_schedules_count: @course.class_schedules_count
+      )
+    end
+
+    if @course.examination_results_count.positive?
+      errors << t(
+        'courses.destroy.remove_examination_results_first',
+        examination_results_count: @course.examination_results_count
+      )
+    end
+
+    if errors.any?
+      joined_errors = "#{t('courses.destroy.unable_to_destroy')} #{errors.join(', ')}"
+
+      redirect_back(
+        fallback_location: courses_path,
+        flash: {
+          danger: joined_errors
+        }
+      )
+    else
+      @course.destroy
+
+      respond_with(@course)
+    end
   end
 
   private

app/helpers/courses_helper.rb

@@ -0,0 +1,10 @@
+module CoursesHelper
+  def link_to_destroy_course(course)
+    link_to_disabled_destroy(
+      policy(course).destroy?,
+      course.class_schedules_count.positive? || course.examination_results_count.positive?,
+      course_path(course),
+      t('courses.destroy.prerequisites_are_not_met')
+    )
+  end
+end

app/views/courses/index.html.haml

@@ -35,4 +35,4 @@
               - if policy(course).tap { |p| break p.edit? || p.destroy? }
                 %td.col-xs-2.col-sm-3.col-md-2.text-right
                   = link_to_edit(policy(course).edit?, edit_course_path(course))
-                  = link_to_destroy(policy(course).destroy?, course_path(course))
+                  = link_to_destroy_course(course)

app/views/courses/show.html.haml

@@ -10,7 +10,7 @@
 
     .pull-right
       = link_to_edit(policy(@course).edit?, edit_course_path(@course))
-      = link_to_destroy(policy(@course).destroy?, course_path(@course))
+      = link_to_destroy_course(@course)
 
   .col-xs-12.col-sm-8.col-sm-offset-2.vert-offset-top-1
     %h5

config/locales/general.ru.yml

@@ -137,6 +137,11 @@ ru:
       results_per_examination: 'Количество сданных зачетных работ'
       course_description_help: 'Может отображаться студентам'
       course_variant_help: 'Отображается только администраторам, чтобы отличать очень похожие предметы'
+    destroy:
+      unable_to_destroy: 'Невозможно удалить предмет так как'
+      remove_class_schedules_first: "с ним связаны %{class_schedules_count} расписаний занятий"
+      remove_examination_results_first: 'он имеет %{examination_results_count} сданных зачетных работ'
+      prerequisites_are_not_met: "С этим предметом связаны расписания занятий и сданы зачетные работы. Сначала уберите эти связи"
   crops:
     crop_image:
       title:        'Кадрирование изображения'

config/locales/general.uk.yml

@@ -137,6 +137,11 @@ uk:
       results_per_examination: 'Кількість зданих залікових робіт'
       course_description_help: 'Може відображатися студентам'
       course_variant_help: 'Відображається тільки адміністраторам, щоб відрізняти дуже схожі предмети'
+    destroy:
+      unable_to_destroy: 'Неможливо видалити предмет бо'
+      remove_class_schedules_first: "з ним пов'язано %{class_schedules_count} розкладів занять"
+      remove_examination_results_first: 'він має %{examination_results_count} зданих залікових робіт'
+      prerequisites_are_not_met: "З цим предметом пов`язані розклади занять та здані залікові роботи. Спочатку приберіть ці зв'язки"
   crops:
     crop_image:
       title:    'Кадрування зображення'

spec/controllers/courses_controller_spec.rb

@@ -113,16 +113,67 @@
 
         describe '#destroy' do
           Given(:actions) { ['course:destroy'] }
-          Given!(:course) { create :course }
 
           Given { expect(ClassScheduleWithPeople).to receive(:refresh_later) }
 
           describe 'with success' do
+            Given!(:course) { create :course }
+
             Then { expect { delete :destroy, params: { id: course.id } }.to change(Course, :count).by(-1) }
             And  { expect(response).to redirect_to(courses_path) }
             And  { is_expected.to set_flash[:notice] }
             And  { expect(assigns(:course)).to eq(course) }
           end
+
+          shared_examples :courses_destroy_prerequisites_are_not_met do
+            Then { expect { delete :destroy, params: { id: course.id } }.not_to change(Course, :count) }
+            And  { expect(response).to redirect_to(courses_path) }
+            And  { is_expected.to set_flash[:danger].to(expected_flash_message) }
+            And  { expect(assigns(:course)).to eq(course) }
+          end
+
+          describe 'class_schedules_count is not zero' do
+            Given!(:course) { create :course, class_schedules_count: 1 }
+            Given(:expected_flash_message) do
+              I18n.t('courses.destroy.unable_to_destroy') + ' ' + I18n.t(
+                'courses.destroy.remove_class_schedules_first',
+                class_schedules_count: 1
+              )
+            end
+
+            it_behaves_like :courses_destroy_prerequisites_are_not_met
+          end
+
+          describe 'examination_results_count is not zero' do
+            Given!(:course) { create :course, examination_results_count: 2 }
+            Given(:expected_flash_message) do
+              I18n.t('courses.destroy.unable_to_destroy') + ' ' + I18n.t(
+                'courses.destroy.remove_examination_results_first',
+                examination_results_count: 2
+              )
+            end
+
+            it_behaves_like :courses_destroy_prerequisites_are_not_met
+          end
+
+          describe 'both class_schedules_count and examination_results_count are not zero' do
+            Given!(:course) { create :course, class_schedules_count: 1, examination_results_count: 2 }
+            Given(:expected_flash_message) do
+              I18n.t('courses.destroy.unable_to_destroy') +
+                ' ' +
+                I18n.t(
+                  'courses.destroy.remove_class_schedules_first',
+                  class_schedules_count: 1
+                ) +
+                ', ' +
+                I18n.t(
+                  'courses.destroy.remove_examination_results_first',
+                  examination_results_count: 2
+                )
+            end
+
+            it_behaves_like :courses_destroy_prerequisites_are_not_met
+          end
         end
       end
     end

spec/views/courses/index.html.haml_spec.rb

@@ -4,7 +4,7 @@
   Given(:page) { Capybara::Node::Simple.new(response.body) }
   Given(:user) { create :person, roles: [create(:role, activities: activities)] }
   Given(:course) { create :course }
-  Given(:activities) { %w(course:index) }
+  Given(:activities) { %w[course:index] }
 
   Given { allow(view).to receive(:policy).with(course).and_return(CoursePolicy.new(user, course)) }
 
@@ -36,7 +36,7 @@
     end
 
     context 'with :show rights' do
-      Given(:activities) { %w(course:index course:show) }
+      Given(:activities) { %w[course:index course:show] }
 
       Then { expect(row).to have_link(course.title, href: course_path(course)) }
       And  { no_new_link }
@@ -45,7 +45,7 @@
     end
 
     context 'with :new rights' do
-      Given(:activities) { %w(course:index course:new) }
+      Given(:activities) { %w[course:index course:new] }
 
       Then { expect(table_container).to have_link('', href: new_course_path) }
       And  { no_show_link }
@@ -54,7 +54,7 @@
     end
 
     context 'with :edit rights' do
-      Given(:activities) { %w(course:index course:edit) }
+      Given(:activities) { %w[course:index course:edit] }
 
       Then { expect(table_container).to have_link(I18n.t('links.edit'), href: edit_course_path(course)) }
       And  { no_show_link }
@@ -63,9 +63,34 @@
     end
 
     context 'with :destroy rights' do
-      Given(:activities) { %w(course:index course:destroy) }
-
-      Then { expect(table_container).to have_link(I18n.t('links.delete'), href: "/courses/#{course.id}") }
+      Given(:course_with_schedule) { create :course, class_schedules_count: 1 }
+      Given(:course_with_examination_results) { create :course, examination_results_count: 2 }
+      Given(:course_with_both) { create :course, class_schedules_count: 1, examination_results_count: 2 }
+
+      Given(:activities) { %w[course:index course:destroy] }
+      Given(:have_disabled_destroy_link) { have_selector('.disabled-button-with-popover a.btn-danger.disabled') }
+
+      Given { allow(view).to receive(:policy).with(course_with_schedule).and_return(CoursePolicy.new(user, course_with_schedule)) }
+      Given { allow(view).to receive(:policy).with(course_with_examination_results).and_return(CoursePolicy.new(user, course_with_examination_results)) }
+      Given { allow(view).to receive(:policy).with(course_with_both).and_return(CoursePolicy.new(user, course_with_both)) }
+      Given { assign(:courses, [course, course_with_schedule, course_with_examination_results, course_with_both]) }
+
+      def course_row_by_title(course)
+        table_container.find('tbody tr', text: course.title)
+      end
+
+      def have_course_link(course)
+        have_link(I18n.t('links.delete'), href: "/courses/#{course.id}")
+      end
+
+      Then { expect(course_row_by_title(course)).to have_course_link(course) }
+      And  { expect(course_row_by_title(course)).not_to have_disabled_destroy_link }
+      And  { expect(course_row_by_title(course_with_schedule)).to have_disabled_destroy_link }
+      And  { expect(course_row_by_title(course_with_examination_results)).to have_disabled_destroy_link }
+      And  { expect(course_row_by_title(course_with_both)).to have_disabled_destroy_link }
+      And  { expect(course_row_by_title(course_with_schedule)).not_to have_course_link(course_with_schedule) }
+      And  { expect(course_row_by_title(course_with_examination_results)).not_to have_course_link(course_with_examination_results) }
+      And  { expect(course_row_by_title(course_with_both)).not_to have_course_link(course_with_both) }
       And  { no_show_link }
       And  { no_edit_link }
       And  { no_new_link }

spec/views/courses/show.html.haml_spec.rb

@@ -5,13 +5,15 @@
   Given(:user) { create :person, roles: [create(:role, activities: activities)] }
   Given(:course) { create :course, title: course_title }
   Given(:academic_group) { create :academic_group }
-  Given(:activities) { %w(course:show) }
+  Given(:activities) { %w[course:show] }
   Given(:course_title) { 'Bhakta Program' }
 
   Given { allow(view).to receive(:policy).with(course).and_return(CoursePolicy.new(user, course)) }
   Given { allow(view).to receive(:policy).with(Course).and_return(CoursePolicy.new(user, Course)) }
   Given { allow(view).to receive(:policy).with(Examination).and_return(CoursePolicy.new(user, Examination)) }
-  Given { allow(view).to receive(:policy).with(academic_group).and_return(AcademicGroupPolicy.new(user, academic_group)) }
+  Given do
+    allow(view).to receive(:policy).with(academic_group).and_return(AcademicGroupPolicy.new(user, academic_group))
+  end
 
   Given { assign(:course, course) }
   Given { assign(:academic_groups, [academic_group]) }
@@ -36,23 +38,55 @@
     end
 
     context 'with course:edit rights' do
-      Given(:activities) { %w(course:edit) }
+      Given(:activities) { %w[course:edit] }
 
       Then { expect(container).to(have_edit_course_link) }
       And  { expect_no_destroy_link }
       And  { expect_no_academic_group_link }
     end
 
     context 'with course:destroy rights' do
-      Given(:activities) { %w(course:destroy) }
+      Given(:activities) { %w[course:destroy] }
 
-      Then { expect(container).to(have_destroy_course_link) }
-      And  { expect_no_edit_link }
-      And  { expect_no_academic_group_link }
+      describe 'with enabled "destroy" link' do
+        Then { expect(container).to(have_destroy_course_link) }
+        And  { expect_no_edit_link }
+        And  { expect_no_academic_group_link }
+      end
+
+      describe 'with disabled "destroy" link' do
+        shared_examples :courses_destroy_is_disabled do
+          Then { expect(container).not_to(have_destroy_course_link) }
+
+          And do
+            expect(container).to(
+              have_selector('.col-xs-12:nth-child(2) .disabled-button-with-popover a.btn-danger.disabled')
+            )
+          end
+        end
+
+        describe 'course has ClassSchedules' do
+          Given(:course) { create :course, title: course_title, class_schedules_count: 1 }
+
+          it_behaves_like :courses_destroy_is_disabled
+        end
+
+        describe 'course has ExaminationResults' do
+          Given(:course) { create :course, title: course_title, examination_results_count: 2 }
+
+          it_behaves_like :courses_destroy_is_disabled
+        end
+
+        describe 'course has both ClassSchedules and ExaminationResults' do
+          Given(:course) { create :course, title: course_title, class_schedules_count: 1, examination_results_count: 2 }
+
+          it_behaves_like :courses_destroy_is_disabled
+        end
+      end
     end
 
     context 'with academic_group:show rights' do
-      Given(:activities) { %w(academic_group:show) }
+      Given(:activities) { %w[academic_group:show] }
 
       Then { expect(container).to(have_academic_group_link) }
       And  { expect_no_destroy_link }