Add conditional stylesheets for mobile apps

app/models/application_platform.rb

@@ -1,4 +1,6 @@
 class ApplicationPlatform < PlatformAgent
+  SCOPED_STYLESHEET_PATHS = {}
+
   def ios?
     match? /iPhone|iPad/
   end
@@ -39,6 +41,18 @@ class ApplicationPlatform < PlatformAgent
     operating_system == "Windows"
   end
 
+  def ios_app?
+    match? /Fizzy iOS/
+  end
+
+  def android_app?
+    match? /Fizzy Android/
+  end
+
+  def mobile_app?
+    ios_app? || android_app?
+  end
+
   def operating_system
     case user_agent.platform
     when /Android/   then "Android"
@@ -51,4 +65,30 @@ class ApplicationPlatform < PlatformAgent
       os =~ /Linux/ ? "Linux" : os
     end
   end
+
+  def stylesheet_asset_name
+    case
+    when android_app? then "android"
+    when ios_app?     then "ios"
+    else                   "desktop"
+    end
+  end
+
+  def stylesheet_paths
+    scoped_stylesheet_paths("web") +
+    (mobile_app? ? scoped_stylesheet_paths("mobile_app") : []) +
+    scoped_stylesheet_paths(stylesheet_asset_name)
+  end
+
+  def scoped_stylesheet_paths(scope = css_asset_name)
+    # Allow new stylesheets to be added in dev/test without restarting server
+    SCOPED_STYLESHEET_PATHS.clear if Rails.env.local?
+
+    SCOPED_STYLESHEET_PATHS[scope] ||=
+      Rails.root.join("app/assets/stylesheets").then do |stylesheet_root|
+        stylesheet_root.glob("#{scope}/**/*.css").collect do |path|
+          path.to_s.remove(stylesheet_root.to_s + "/", ".css")
+        end
+      end
+  end
 end