Add backend for tips and enable markdown support

app/assets/javascripts/editor/editor.js.erb

@@ -315,6 +315,9 @@ var CodeOceanEditor = {
         }).fail(_.noop)
             .always(function () {
                 ace.edit(editor).session.setMode(newMode);
+                if (newMode === 'ace/mode/python') {
+                    ace.edit(editor).setTheme('ace/theme/tomorrow')
+                }
             });
     },
 

app/assets/javascripts/exercises.js.erb

@@ -30,7 +30,11 @@ $(document).on('turbolinks:load', function () {
         editor.setShowPrintMargin(false);
         editor.setTheme(THEME);
 
+        // For creating / editing an exercise
         var textarea = $('textarea[id="exercise_files_attributes_' + index + '_content"]');
+        if ($('.edit_tip, .new_tip').isPresent()) {
+            textarea = $('textarea[id="tip_example"]')
+        }
         var content = textarea.val();
 
         if (content != undefined) {
@@ -383,11 +387,11 @@ $(document).on('turbolinks:load', function () {
             observeExportButtons();
         }
         toggleCodeHeight();
-        if (window.hljs) {
-            highlightCode();
-        }
     }
 
+    if (window.hljs) {
+        highlightCode();
+    }
 
     if ($('#editor-edit').isPresent()) {
         configureEditors();

app/assets/javascripts/forms.js

@@ -31,12 +31,16 @@ $(document).on('turbolinks:load', function() {
   });
 
   // enable chosen hook when editing an exercise to update ace code highlighting
-  if ($.isController('exercises') && $('.edit_exercise, .new_exercise').isPresent()) {
+  if ($.isController('exercises') && $('.edit_exercise, .new_exercise').isPresent() ||
+      $.isController('tips') && $('.edit_tip, .new_tip').isPresent()  ) {
       chosen_inputs.filter(function(){
           return $(this).attr('id').includes('file_type_id');
       }).on('change chosen:ready', function(event, parameter) {
           // Set ACE editor mode (for code highlighting) on change of file type and after initialization
           editorInstance = $(event.target).closest('.card-body').find('.editor')[0];
+          if (editorInstance === undefined) {
+              editorInstance = $(event.target).closest('.container').find('.editor')[0];
+          }
           selectedFileType = event.target.value;
           CodeOceanEditor.updateEditorModeToFileTypeID(editorInstance, selectedFileType);
       })

app/controllers/tips_controller.rb

@@ -0,0 +1,62 @@
+class TipsController < ApplicationController
+  include CommonBehavior
+
+  before_action :set_tip, only: MEMBER_ACTIONS
+  before_action :set_file_types, only: %i[create edit new update]
+
+  def authorize!
+    authorize(@tip || @tips)
+  end
+  private :authorize!
+
+  def create
+    @tip = Tip.new(tip_params)
+    authorize!
+    create_and_respond(object: @tip)
+  end
+
+  def destroy
+    destroy_and_respond(object: @tip)
+  end
+
+  def edit
+  end
+
+  def tip_params
+    return unless params[:tip].present?
+
+    params[:tip]
+      .permit(:title, :description, :example, :file_type_id)
+      .each { |_key, value| value.strip! unless value.is_a?(Array) }
+      .merge(user_id: current_user.id, user_type: current_user.class.name)
+  end
+  private :tip_params
+
+  def index
+    @tips = Tip.all.paginate(page: params[:page])
+    authorize!
+  end
+
+  def new
+    @tip = Tip.new
+    authorize!
+  end
+
+  def set_tip
+    @tip = Tip.find(params[:id])
+    authorize!
+  end
+  private :set_tip
+
+  def show
+  end
+
+  def update
+    update_and_respond(object: @tip, params: tip_params)
+  end
+
+  def set_file_types
+    @file_types = FileType.all.order(:name)
+  end
+  private :set_file_types
+end

app/helpers/application_helper.rb

@@ -5,10 +5,10 @@ module ApplicationHelper
     APPLICATION_NAME
   end
 
-  def code_tag(code)
+  def code_tag(code, language = nil)
     if code.present?
       content_tag(:pre) do
-        content_tag(:code, code)
+        content_tag(:code, code, class: "language-#{language}")
       end
     else
       empty

app/models/file_type.rb

@@ -32,6 +32,10 @@ class FileType < ApplicationRecord
   end
   private :set_default_values
 
+  def programming_language
+    editor_mode.gsub('ace/mode/', '')
+  end
+
   def to_s
     name
   end

app/models/tip.rb

@@ -20,4 +20,9 @@ class Tip < ApplicationRecord
       "#{I18n.t('activerecord.models.tip.one')} #{id}"
     end
   end
+
+  def can_be_destroyed?
+    # This tip can only be destroyed if it is no parent to any other exercise tip
+    ExerciseTip.where(parent_exercise_tip: exercise_tips).none?
+  end
 end

app/policies/tip_policy.rb

@@ -0,0 +1,13 @@
+class TipPolicy < AdminOnlyPolicy
+
+  class Scope < Scope
+    def resolve
+      if @user.admin? || @user.teacher?
+        @scope.all
+      else
+        @scope.none
+      end
+    end
+  end
+
+end

app/views/application/_navigation.html.slim

@@ -10,7 +10,7 @@
           li = link_to(t('breadcrumbs.statistics.show'), statistics_path, class: 'dropdown-item') if policy(:statistics).show?
           li.dropdown-divider role='separator'
         = render('navigation_submenu', title: t('activerecord.models.exercise.other'),
-                models: [Exercise, ExerciseCollection, ProxyExercise, Tag, Submission], link: exercises_path, cached: true)
+                models: [Exercise, ExerciseCollection, ProxyExercise, Tag, Tip, Submission], link: exercises_path, cached: true)
         = render('navigation_submenu', title: t('navigation.sections.users'), models: [InternalUser, ExternalUser],
                 cached: true)
         = render('navigation_collection_link', model: StudyGroup, cached: true)

app/views/tips/_collapsed_card.html.slim

@@ -13,11 +13,11 @@
     .card-body.p-3
       h5
         = t('exercises.implement.tips.description')
-      = tip.description
+      = render_markdown(tip.description)
       - if tip.example?
-        h5.mt-2
+        h5
           = t('exercises.implement.tips.example')
         pre
-          code.mh-100 class="language-#{tip.file_type.editor_mode.gsub("ace/mode/", "")}"
+          code.mh-100 class="language-#{tip.file_type.programming_language}"
             = tip.example
       = render(partial: 'tips/collapsed_card', collection: exercise_tip.children, as: :exercise_tip)

app/views/tips/_form.html.slim

@@ -0,0 +1,21 @@
+= form_for(@tip, builder: PagedownFormBuilder) do |f|
+  = render('shared/form_errors', object: @tip)
+  .form-group
+    = f.label(:title)
+    = f.text_field(:title, class: 'form-control', required: false)
+  .form-group
+    = f.label(:description)
+    = f.pagedown :description, input_html: { preview: true, rows: 5 }
+  .form-group
+    = f.label(:file_type_id, t('activerecord.attributes.file.file_type_id'))
+    = f.collection_select(:file_type_id, @file_types, :id, :name, {include_blank: true}, class: 'form-control')
+  .form-group
+    = f.label(:example)
+    = f.text_area(:example, class: 'code-field form-control', rows: 5, style: "display:none;", required: false)
+    #editor-edit.original-input data-file-id=@tip.id
+      #frames
+        .edit-frame
+          .editor-content.d-none
+          .editor.allow_ace_tooltip
+  .actions = render('shared/submit_button', f: f, object: @tip)
+  .editor

app/views/tips/edit.html.slim

@@ -0,0 +1,3 @@
+h1 = @tip.to_s
+
+= render('form')

app/views/tips/index.html.slim

@@ -0,0 +1,20 @@
+h1 = Tip.model_name.human(count: 2)
+
+.table-responsive
+  table.sortable.table
+    thead
+      tr
+        th = t('activerecord.attributes.tip.title')
+        th = t('activerecord.attributes.file.file_type')
+        th colspan=3 = t('shared.actions')
+    tbody
+      - @tips.each do |tip|
+        tr
+          td = link_to_if(policy(tip).show?, tip.title || tip.to_s, tip)
+          td = tip.file_type ? link_to_if(policy(tip.file_type).show?, tip.file_type.name, tip.file_type) : ''
+          td = link_to(t('shared.show'), tip) if policy(tip).show?
+          td = link_to(t('shared.edit'), edit_tip_path(tip)) if policy(tip).edit?
+          td = link_to(t('shared.destroy'), tip, data: {confirm: t('shared.confirm_destroy')}, method: :delete) if tip.can_be_destroyed? &&  policy(tip).destroy?
+
+= render('shared/pagination', collection: @tips)
+p = render('shared/new_button', model: Tip, path: new_tip_path)

app/views/tips/new.html.slim

@@ -0,0 +1,3 @@
+h1 = t('shared.new_model', model: Tip.model_name.human)
+
+= render('form')

app/views/tips/show.html.slim

@@ -0,0 +1,17 @@
+- content_for :head do
+  // Force a full page reload, see https://github.com/turbolinks/turbolinks/issues/326.
+     Otherwise, code might not be highlighted correctly (race condition)
+  meta name='turbolinks-visit-control' content='reload'
+  = javascript_pack_tag('highlight', 'data-turbolinks-track': true)
+  = stylesheet_pack_tag('highlight', media: 'all', 'data-turbolinks-track': true)
+
+h1
+  = @tip.to_s
+  = render('shared/edit_button', object: @tip)
+
+= row(label: 'tip.title', value: @tip.title)
+= row(label: 'tip.description', value: render_markdown(@tip.description), class: 'm-0')
+= row(label: 'file.file_type', value: @tip.file_type_id? ? \
+  link_to_if(policy(@tip.file_type).show?, @tip.file_type.name, @tip.file_type) : '')
+= row(label: 'tip.example', value: @tip.file_type_id? ? \
+  code_tag(@tip.example, @tip.file_type.programming_language) : '')

config/routes.rb

@@ -107,6 +107,8 @@ Rails.application.routes.draw do
 
   resources :tags
 
+  resources :tips
+
   resources :user_exercise_feedbacks, except: [:show, :index]
 
   resources :external_users, only: [:index, :show], concerns: :statistics do