Add basic functionality

app/controllers/application_controller.rb

@@ -1,2 +1,5 @@
 class ApplicationController < ActionController::Base
+  def resource_class
+    controller_path.classify.constantize
+  end
 end

app/controllers/countries_controller.rb

@@ -0,0 +1,13 @@
+class CountriesController < ApplicationController
+  helper_method %i[countries country]
+
+  def countries
+    resource_class.all
+  end
+
+  def country
+    return resource_class.find(params[:id]) if params[:id].is_a?(Integer)
+    return resource_class.find_by(iso2: params[:id]) if params[:id].length == 2
+    resource_class.find_by(iso3: params[:id])
+  end
+end

app/controllers/people_controller.rb

@@ -0,0 +1,7 @@
+class PeopleController < ApplicationController
+  helper_method :person
+
+  def person
+    resource_class.find(params[:id])
+  end
+end