Add database support and model for tips

app/models/exercise.rb

@@ -24,6 +24,8 @@ class Exercise < ApplicationRecord
   has_many :tags, through: :exercise_tags
   accepts_nested_attributes_for :exercise_tags
   has_many :user_exercise_feedbacks
+  has_many :exercise_tips
+  has_many :tips, through: :exercise_tips
 
   has_many :external_users, source: :user, source_type: 'ExternalUser', through: :submissions
   has_many :internal_users, source: :user, source_type: 'InternalUser', through: :submissions

app/models/exercise_tip.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class ExerciseTip < ApplicationRecord
+  belongs_to :exercise
+  belongs_to :tip
+  belongs_to :parent_exercise_tip, class_name: 'ExerciseTip', optional: true
+  attr_accessor :children
+
+  # Ensure no parent tip is set if current tip has rank == 1
+  validates :rank, exclusion: {in: [1]}, if: :parent_exercise_tip_id?
+
+  validate :tip_chain?, if: :parent_exercise_tip_id?
+
+  def tip_chain?
+    # Ensure each referenced parent exercise tip is set for this exercise
+    errors.add :parent_exercise_tip, I18n.t('activerecord.errors.messages.together', attribute: I18n.t('activerecord.attributes.exercise_tip.tip')) unless ExerciseTip.exists?(exercise: exercise, tip: parent_exercise_tip)
+  end
+end

app/models/tip.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class Tip < ApplicationRecord
+  include Creation
+
+  has_many :exercise_tips
+  has_many :exercises, through: :exercise_tips
+  belongs_to :file_type, optional: true
+  validates_presence_of :file_type, if: :example?
+  validate :content?
+
+  def content?
+    errors.add :description, I18n.t('activerecord.errors.messages.at_least', attribute: I18n.t('activerecord.attributes.tip.example')) unless [description?, example?].include?(true)
+  end
+
+  def to_s
+    if title?
+      "#{I18n.t('activerecord.models.tip.one')}: #{title} (#{id})"
+    else
+      "#{I18n.t('activerecord.models.tip.one')} #{id}"
+    end
+  end
+end

config/locales/de.yml

@@ -121,6 +121,10 @@ de:
         name: Name
         usage: Verwendet
         difficulty: Anteil an der Aufgabe
+      tip:
+        title: Titel
+        description: Beschreibung
+        example: Beispiel
       file_template:
         name: "Name"
         file_type: "Dateityp"
@@ -215,6 +219,7 @@ de:
     errors:
       messages:
         together: 'muss zusammen mit %{attribute} definiert werden'
+        at_least: 'oder %{attribute} muss definiert sein'
       models:
         exercise:
           at_most_one_main_file: dürfen höchstens eine Hauptdatei enthalten

config/locales/en.yml

@@ -121,6 +121,10 @@ en:
         name: Name
         usage: Used
         difficulty: Share on the Exercise
+      tip:
+        title: title
+        description: description
+        example: example
       file_template:
         name: "Name"
         file_type: "File Type"
@@ -215,6 +219,7 @@ en:
     errors:
       messages:
         together: 'has to be set along with %{attribute}'
+        at_least: 'or %{attribute} must be defined'
       models:
         exercise:
           at_most_one_main_file: must include at most one main file

db/migrate/20201007104221_create_tips.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class CreateTips < ActiveRecord::Migration[5.2]
+  def change
+    create_table :tips do |t|
+      t.string :title
+      t.text :description
+      t.text :example
+      t.references :file_type, foreign_key: true
+      t.references :user, polymorphic: true, null: false
+      t.timestamps
+    end
+
+    create_table :exercise_tips do |t|
+      t.references :exercise, null: false
+      t.references :tip, null: false
+      t.integer :rank, null: false
+      t.references :parent_exercise_tip, foreign_key: {to_table: :exercise_tips}
+      t.index %i[exercise_id tip_id rank], unique: true
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_05_06_093054) do
+ActiveRecord::Schema.define(version: 2020_10_07_104221) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -137,6 +137,17 @@ ActiveRecord::Schema.define(version: 2020_05_06_093054) do
     t.integer "factor", default: 1
   end
 
+  create_table "exercise_tips", force: :cascade do |t|
+    t.bigint "exercise_id", null: false
+    t.bigint "tip_id", null: false
+    t.integer "rank", null: false
+    t.bigint "parent_exercise_tip_id"
+    t.index ["exercise_id", "tip_id", "rank"], name: "index_exercise_tips_on_exercise_id_and_tip_id_and_rank", unique: true
+    t.index ["exercise_id"], name: "index_exercise_tips_on_exercise_id"
+    t.index ["parent_exercise_tip_id"], name: "index_exercise_tips_on_parent_exercise_tip_id"
+    t.index ["tip_id"], name: "index_exercise_tips_on_tip_id"
+  end
+
   create_table "exercises", id: :serial, force: :cascade do |t|
     t.text "description"
     t.integer "execution_environment_id"
@@ -389,6 +400,19 @@ ActiveRecord::Schema.define(version: 2020_05_06_093054) do
     t.index ["submission_id"], name: "index_testruns_on_submission_id"
   end
 
+  create_table "tips", force: :cascade do |t|
+    t.string "title"
+    t.text "description"
+    t.text "example"
+    t.bigint "file_type_id"
+    t.string "user_type", null: false
+    t.bigint "user_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["file_type_id"], name: "index_tips_on_file_type_id"
+    t.index ["user_type", "user_id"], name: "index_tips_on_user_type_and_user_id"
+  end
+
   create_table "user_exercise_feedbacks", id: :serial, force: :cascade do |t|
     t.integer "exercise_id", null: false
     t.integer "user_id", null: false
@@ -427,4 +451,5 @@ ActiveRecord::Schema.define(version: 2020_05_06_093054) do
 
   add_foreign_key "request_for_comments", "submissions", name: "request_for_comments_submissions_id_fk"
   add_foreign_key "submissions", "study_groups"
+  add_foreign_key "tips", "file_types"
 end