001_health_check.rb

class HealthCheck
  class Middleware

    def initialize(application)
      @application = application
    end

    def call(environment)
      if environment['PATH_INFO'] == '/health-check'
        if HealthCheck.healthy?
          [200, {}, ['OK']]
        else
          [500, {}, ['PROBLEM']]
        end
      else
        @application.call(environment)
      end
    end
  end
end

002_mobile_format_basic.rb

module Mobile
  class Format

    def initialize(application)
      @application = application
    end

    def call(environment)
      request = Rack::Request.new(environment)

      user_agent = ::Mobile::UserAgent.new(request.env['HTTP_USER_AGENT'])

      if request.params['mobile'] == '1' || user_agent.mobile?
        request.env['HTTP_ACCEPT'] = 'text/html+mobile'
      end

      status, headers, body = @application.call(request.env)

      response = Rack::Response.new(body, status, headers)
      response.finish
    end
  end
end

003_mobile_format_refactored.rb

module Mobile
  class Format

    def initialize(application)
      @application = application
    end

    def call(environment)
      request = Rack::Request.new(environment)
      
      set_mobile_accept_header(request) if serve_mobile?(request)
      response = response(request)
      response.finish
    end

    private

    def user_agent(request)
      Mobile::UserAgent.new(request.env['HTTP_USER_AGENT'])
    end

    def mobile_requested?(request)
      request.params['mobile'] == '1'
    end

    def serve_mobile?(request)
      mobile_requested?(request) || user_agent(request).mobile?
    end

    def set_mobile_accept_header(request)
      request.env['HTTP_ACCEPT'] = 'text/html+mobile'
    end

    def response(request)
      status, headers, body = @application.call(request.env)
      Rack::Response.new(body, status, headers)
    end

  end
end

004_mobile_format_ivar.rb

module Mobile
  class Format

    def initialize(application)
      @application = application
    end

    def call(environment)
      @environment = environment

      set_mobile_accept_header if serve_mobile?
      response.finish
    end

    private

    def request
      @request ||= Rack::Request.new(@environment)
    end

    def user_agent
      Mobile::UserAgent.new(request.env['HTTP_USER_AGENT'])
    end

    def mobile_requested?
      request.params['mobile'] == '1'
    end

    def serve_mobile?
      mobile_requested? || user_agent.mobile?
    end

    def set_mobile_accept_header
      request.env['HTTP_ACCEPT'] = 'text/html+mobile'
    end

    def response
      status, headers, body = @application.call(request.env)
      Rack::Response.new(body, status, headers)
    end

  end
end

005_mobile_format_with_responder.rb

module Mobile
  class Format

    def initialize(application)
      @application = application
    end

    def call(environment)
      responder = Mobile::Format::Responder.new(@application, environment)
      responder.respond
    end

    class Responder

      def initialize(application, environment)
        @application = application
        @environment = environment
      end

      def respond
        set_mobile_accept_header if serve_mobile?
        response.finish
      end

      private

      def request
        @request ||= Rack::Request.new(@environment)
      end

      def user_agent
        ::Mobile::UserAgent.new(request.env['HTTP_USER_AGENT'])
      end

      def mobile_requested?
        request.params['mobile'] == '1'
      end

      def serve_mobile?
        mobile_requested? || user_agent.mobile?
      end

      def set_mobile_accept_header
        request.env['HTTP_ACCEPT'] = 'text/html+mobile'
      end

      def response
        @response ||= begin
          status, headers, body = @application.call(request.env)
          Rack::Response.new(body, status, headers)
        end
      end
    end
  end
end