Add `GET /api/v1/instance/languages` to REST API (#24443)

Co-authored-by: Eugen Rochko <eugen@zeonfederated.com>
Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/controllers/api/v1/instances/languages_controller.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+class Api::V1::Instances::LanguagesController < Api::BaseController
+  skip_before_action :require_authenticated_user!, unless: :limited_federation_mode?
+  skip_around_action :set_locale
+
+  before_action :set_languages
+
+  vary_by ''
+
+  def show
+    cache_even_if_authenticated!
+    render json: @languages, each_serializer: REST::LanguageSerializer
+  end
+
+  private
+
+  def set_languages
+    @languages = LanguagesHelper::SUPPORTED_LOCALES.keys.map { |code| LanguagePresenter.new(code) }
+  end
+end

app/presenters/language_presenter.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class LanguagePresenter < ActiveModelSerializers::Model
+  attributes :code, :name, :native_name
+
+  def initialize(code)
+    super()
+
+    @code = code
+    @item = LanguagesHelper::SUPPORTED_LOCALES[code]
+  end
+
+  def name
+    @item[0]
+  end
+
+  def native_name
+    @item[1]
+  end
+end

app/serializers/rest/language_serializer.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class REST::LanguageSerializer < ActiveModel::Serializer
+  attributes :code, :name
+end

config/routes/api.rb

@@ -120,6 +120,7 @@ namespace :api, format: false do
       resource :privacy_policy, only: [:show], controller: 'instances/privacy_policies'
       resource :extended_description, only: [:show], controller: 'instances/extended_descriptions'
       resource :translation_languages, only: [:show], controller: 'instances/translation_languages'
+      resource :languages, only: [:show], controller: 'instances/languages'
       resource :activity, only: [:show], controller: 'instances/activity'
     end
 

spec/requests/api/v1/instances/languages_spec.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'Languages' do
+  describe 'GET /api/v1/instance/languages' do
+    before do
+      get '/api/v1/instance/languages'
+    end
+
+    it 'returns http success' do
+      expect(response).to have_http_status(200)
+    end
+
+    it 'returns the supported languages' do
+      expect(body_as_json.pluck(:code)).to match_array LanguagesHelper::SUPPORTED_LOCALES.keys.map(&:to_s)
+    end
+  end
+end