static_files.rb

# Allow the metal piece to run in isolation
require(File.dirname(__FILE__) + "/../../config/environment") unless defined?(Rails)

# Speeds up the presentation of static files by not going through Rails at all.
# TODO: streaming for large files
class StaticFiles
  MAX_FILE_SIZE = 262_144 # 256KB
  
  def self.call(env)
    static_file_name = File.join Rails.root, "assets", env["SERVER_NAME"], "original", env["PATH_INFO"]
    if env["PATH_INFO"] != "/" && File.exist?(static_file_name) && File.size(static_file_name) < MAX_FILE_SIZE
      content_type = File.mime_type?(static_file_name)
      if Rails.env == "production"
        [200, {
          "Content-Type"  => content_type,
          "Expires"       => (Time.now + 1.week).to_s(:rfc822),
          "Cache-Control" => "max-age=#{1.week.to_i}",
          "X-Sendfile"    => static_file_name
        }, [""]]
      else
        file = File.open(static_file_name)
        contents = file.read
        file.close
        [200, {
          "Content-Type"  => content_type,
          "Expires"       => (Time.now + 1.week).to_s(:rfc822),
          "Cache-Control" => "max-age=#{1.week.to_i}"
        }, [contents]]
      end
    else
      [404, {"Content-Type" => "text/html"}, ["Not Found"]]
    end
  end
end