Add SDG::Review model

and its relation with relatables

Note about sdg_review factory: Cannot use the constantize method on
the relatable_type as long as the relatable classes will be loaded and
this will throw an exception because the database is not available at
factiry definition time.

app/models/concerns/sdg/relatable.rb

@@ -10,6 +10,8 @@ module SDG::Relatable
                source: :related_sdg,
                source_type: sdg_type
     end
+
+    has_one :sdg_review, as: :relatable, dependent: :destroy, class_name: "SDG::Review"
   end
 
   class_methods do

app/models/sdg/review.rb

@@ -0,0 +1,5 @@
+class SDG::Review < ApplicationRecord
+  validates :relatable_id, uniqueness: { scope: [:relatable_type] }
+
+  belongs_to :relatable, polymorphic: true, optional: false
+end

db/migrate/20201221100246_create_sdg_reviews.rb

@@ -0,0 +1,8 @@
+class CreateSDGReviews < ActiveRecord::Migration[5.2]
+  def change
+    create_table :sdg_reviews do |t|
+      t.references :relatable, polymorphic: true, index: { unique: true }
+      t.timestamps
+    end
+  end
+end

db/schema.rb

@@ -1352,6 +1352,14 @@ ActiveRecord::Schema.define(version: 2021_01_07_125458) do
     t.index ["related_sdg_type", "related_sdg_id"], name: "index_sdg_relations_on_related_sdg_type_and_related_sdg_id"
   end
 
+  create_table "sdg_reviews", force: :cascade do |t|
+    t.string "relatable_type"
+    t.bigint "relatable_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["relatable_type", "relatable_id"], name: "index_sdg_reviews_on_relatable_type_and_relatable_id", unique: true
+  end
+
   create_table "sdg_targets", force: :cascade do |t|
     t.bigint "goal_id"
     t.string "code", null: false

spec/factories/sdg.rb

@@ -18,4 +18,13 @@ FactoryBot.define do
   factory :sdg_phase, class: "SDG::Phase" do
     kind { :sensitization }
   end
+
+  factory :sdg_review, class: "SDG::Review" do
+    SDG::Related::RELATABLE_TYPES.map { |relatable_type| relatable_type.downcase.gsub("::", "_") }
+    .each do |relatable|
+      trait :"#{relatable}_review" do
+        association :relatable, factory: relatable
+      end
+    end
+  end
 end

spec/models/sdg/relatable_spec.rb

@@ -117,6 +117,18 @@ describe SDG::Relatable do
     end
   end
 
+  describe "#sdg_review" do
+    it "returns nil when relatable is not reviewed" do
+      expect(relatable.sdg_review).to be_blank
+    end
+
+    it "returns the review when relatable is reviewed" do
+      review = create(:sdg_review, relatable: relatable)
+
+      expect(relatable.sdg_review).to eq(review)
+    end
+  end
+
   describe ".by_goal" do
     it "returns everything if no code is provided" do
       expect(relatable.class.by_goal("")).to eq [relatable]

spec/models/sdg/review_spec.rb

@@ -0,0 +1,23 @@
+require "rails_helper"
+
+describe SDG::Review do
+  describe "Validations" do
+    it "is valid for any given relatable" do
+      review = build(:sdg_review, :debate_review)
+
+      expect(review).to be_valid
+    end
+
+    it "is not valid without a relatable" do
+      review = build(:sdg_review, relatable: nil)
+
+      expect(review).not_to be_valid
+    end
+
+    it "is not valid when a review for given relatable already exists" do
+      relatable = create(:sdg_review, :proposal_review).relatable
+
+      expect(build(:sdg_review, relatable: relatable)).not_to be_valid
+    end
+  end
+end