Day 1

.tool-versions

@@ -0,0 +1 @@
+ruby 3.3.0

Gemfile

@@ -29,6 +29,9 @@ gem 'activeadmin'
 gem 'activeadmin_addons'
 gem 'devise'
 
+# serializer
+gem 'alba'
+
 group :development, :test do
   gem 'bundler-audit'
   gem 'capybara'

Gemfile.lock

@@ -95,6 +95,8 @@ GEM
       uri (>= 0.13.1)
     addressable (2.8.7)
       public_suffix (>= 2.0.2, < 7.0)
+    alba (3.5.0)
+      ostruct (~> 0.6)
     arbre (1.7.0)
       activesupport (>= 3.0.0)
       ruby2_keywords (>= 0.0.2)
@@ -448,6 +450,7 @@ DEPENDENCIES
   activeadmin
   activeadmin_addons
   activerecord-import
+  alba
   bundler-audit
   capybara
   config

app/controllers/application_controller.rb

@@ -1,4 +1,14 @@
 class ApplicationController < ActionController::Base
   # Only allow modern browsers supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has.
   allow_browser versions: :modern
+
+  private
+
+  def serialize(obj, with: nil)
+    serializer = with || begin
+      model = obj.try(:model) || obj.class
+      "#{model.name}Serializer".constantize
+    end
+    serializer.new(obj).serialize
+  end
 end

app/controllers/books_controller.rb

@@ -0,0 +1,17 @@
+class BooksController < ApplicationController
+  def index
+    books =  Book.order(:created_at).limit(per_page).offset(page * per_page)
+
+    render json: serialize(books)
+  end
+
+  private
+
+  def per_page
+    ::Settings.app.items_per_page
+  end
+
+  def page
+    [ params[:page].to_i, 0 ].max
+  end
+end

app/serializers/application_serializer.rb

@@ -0,0 +1,7 @@
+class ApplicationSerializer
+  include Alba::Serializer
+
+  def self.one(name, **options)
+    options[:resource] ||= proc { "#{_1.class.name}Serializer".constantize }
+  end
+end

app/serializers/book_serializer.rb

@@ -0,0 +1,3 @@
+class BookSerializer < ApplicationSerializer
+  attributes :id, :title, :series, :serno, :libid, :size, :filename, :ext, :del, :insno, :published_at, :created_at, :updated_at
+end

config/database.yml

@@ -17,6 +17,7 @@ development:
 
 test:
   <<: *default
+  <<: *postgre
   database: library_test
 
 production:

config/routes.rb

@@ -20,10 +20,11 @@
   #   # end
   # end
 
+  resources :books, only: :index
+
   # Reveal health status on /up that returns 200 if the app boots with no exceptions, otherwise 500.
   # Can be used by load balancers and uptime monitors to verify that the app is live.
   get 'up' => 'rails/health#show', as: :rails_health_check
-
   # Render dynamic PWA files from app/views/pwa/*
   get 'service-worker' => 'rails/pwa#service_worker', as: :pwa_service_worker
   get 'manifest' => 'rails/pwa#manifest', as: :pwa_manifest

spec/controllers/books_controller_spec.rb

@@ -0,0 +1,41 @@
+RSpec.describe BooksController, type: :controller do
+  let(:per_page) { ::Settings.app.items_per_page }
+
+  describe 'GET #index' do
+    context 'when without page' do
+      before { get :index }
+
+      it 'responds with ok status' do
+        expect(response).to have_http_status :ok
+      end
+
+      it 'responds first 20 books' do
+        expect(JSON.parse(response.body).size).to eq(per_page)
+      end
+    end
+
+    context 'when with page' do
+      before { get :index, params: { page: 3 } }
+
+      it 'responds with ok status' do
+        expect(response).to have_http_status :ok
+      end
+
+      it 'returns other 20 books' do
+        expect(JSON.parse(response.body).size).to eq(per_page)
+      end
+    end
+
+    context 'when page too big' do
+      before { get :index, params: { page: (Book.count / per_page + per_page) } }
+
+      it 'responds with ok status' do
+        expect(response).to have_http_status :ok
+      end
+
+      it 'returns 0 books' do
+        expect(JSON.parse(response.body).size).to eq(0)
+      end
+    end
+  end
+end