Add active_language controller and cookie storage

app/controllers/active_language_controller.rb

@@ -0,0 +1,10 @@
+class ActiveLanguageController < ApplicationController
+
+  def set_active_language
+    if Language.find_by_id(params[:active_language_id]) != nil
+      cookies[:active_language_id] = params[:active_language_id]
+    else
+      redirect_to root_path, status: :unprocessable_entity
+    end
+  end
+end

app/helpers/active_language_helper.rb

@@ -0,0 +1,8 @@
+module ActiveLanguageHelper
+
+  def active_language_select_tag
+    languages = Language.all.to_a.delete_if {|language| language.name == "English" }
+    options = options_from_collection_for_select(languages, "id", "name", cookies[:active_language_id] || 1)
+    select_tag "active_language_id", options
+  end
+end

app/views/layouts/application.html.erb

@@ -18,6 +18,11 @@
           <% if user_signed_in? %>
             <pre style="display: inline;">|</pre>
             <%= link_to "Languages", admin_languages_path %>
+            <pre style="display: inline;">|</pre>
+            <%= form_tag '/set_active_language', class: "d-inline" do %>
+              <%= active_language_select_tag %>
+              <%= submit_tag "Switch Language" %>
+            <% end %>
           <% end %>
         </div>
         <div class="ms-auto p-2">