static_file_server.rb

require 'rack/utils'

class StaticFileServer
    def initialize
      @middleware_stack = ActionDispatch::MiddlewareStack.new
      @middleware_stack.use ActionDispatch::ShowExceptions, show_exception_app unless Rails.env.development?
      @middleware_stack.use Bugsnag::Rack
    end

    def call(env)
      @app = build_app
      @app.call(env)
    end

    private

    def build_app
      @app ||= @middleware_stack.build(Base.new)
    end

    def show_exception_app
      ActionDispatch::PublicExceptions.new(Rails.public_path)
    end

    class Base
      def call(env)
        path = env["SERVER_NAME"]
        raise StandardError.exception("This is a test")
        file, headers = pick_file_and_headers_for_path(path, env)
        ::Rack::File.new(file, headers).call(env)
      end

      private

      def get_best_encoding(request)
        Rack::Utils.select_best_encoding(%w(gzip identity), request.accept_encoding)
      end

      def headers
        @headers ||= {'Content-Type' => 'text/html' }
      end

      def pick_file_and_headers_for_path(path, env)
        request = Rack::Request.new(env)
        encoding = get_best_encoding(request)
        file = "#{Rails.root.to_s}/public/media_kits/" + path + '.html'
        if File.exist?(file)
          if encoding == 'gzip'
            file = file + '.gz'
            headers['Content-Encoding'] = 'gzip'
          end
        else
          raise ActionController::RoutingError.exception("Page Not Found")
        end
        [file, headers]
      end
    end
end