add an internal fallback URL for CaaS

app.rb

@@ -50,6 +50,7 @@ DURATION_PARTS = [
 config = Config.new
 
 set :session_secret, config.session_secret.unwrap
+set :public_folder, __dir__ + "/static"
 
 module Sinatra
   module RequestHeadersHelper
@@ -499,14 +500,16 @@ get "/bytes/:size" do
   generate_bytes(Integer(n))
 end
 
-get "/kitty" do
+get "/api/caas" do
+  send_file Dir[__dir__ + "/static/cat*.jpg"].sample
+end
+
 get "/meow" do
   caas_host = ENV.fetch "CAAS_SERVICE_HOST", nil
   caas_port = ENV.fetch "CAAS_SERVICE_PORT", nil
   url = "http://#{caas_host}:#{caas_port}/"
   unless caas_host && caas_port
-    # fail-safe url
-    url = "https://i.imgur.com/epzPw7L.jpeg"
+    url = url("/api/caas")
   end
   tmp_file = Tempfile.open binmode: true do |f|
     # f.chmod 0o644