Rack Domain redirect

production.rb

XXX.configure do
  require 'rack_domain_redirect'
  config.middleware.insert 0, Rack::DomainRedirect
end

rack_domain_redirect.rb

module Rack
  class DomainRedirect
    attr_accessor :prefix
    def initialize(app, &block)
      @app = app
      @prefix = 'www'
      yield self if block_given?
    end

    def call(env)
      parts = env['SERVER_NAME'].split('.')
      suffix, chunk, prefix = parts.pop, parts.pop, parts.pop

      if prefix != 'www' && prefix != 'staging' && prefix != 'couptopia'
        destination  = "#{env['rack.url_scheme']}://#{@prefix}.#{chunk}.#{suffix}"
        destination << "#{env['PATH_INFO']}"
        destination << "?#{env['QUERY_STRING']}" unless env['QUERY_STRING'].empty?

        [301, {'Location' => destination}, ['See Ya!']]
      else
        @app.call(env)
      end
    end
  end
end