Several simple Rack Applications and Middlewares

content_length.ru

use Rack::ContentLength

run Proc.new { |env|

  [200, {}, ['Hello from Rack']]

}

powered_by_rack.rb

# This is Rack Middleware!

class PoweredByRack

  POWERED_BY_HEADER = "X-Powered-By"
  POWERED_BY_VALUE = "Rack (Ruby Webserver Interface) v#{Rack.release}"

  def initialize(app, header_value=nil)
    @app = app
    @header_value = header_value || POWERED_BY_VALUE
  end

  def call(env)
    status, headers, body = @app.call(env)

    headers[POWERED_BY_HEADER] = @header_value

    [status, headers, body]
  end
end

# invoke with either:
#     use PoweredByRack
#     use PoweredByRack, "Rack Powered!"

request.ru

class Hello
  def self.call(env)
    request = Rack::Request.new(env)

    # Evaluate request.accept_language
    
    # Return language appropriate body
    
  end
end
run Hello

response.ru

class Hello
  def self.call(env)
    response = Rack::Response.new
    response['Content-Type'] = 'text/plain'
    response.status = 200
    response.body = ['Hello', ' from Rack!']
    response.finish
  end
end

run Hello

simple.ru

run Proc.new { |env|

  [200, {}, ['Hello from Rack']]

}