Rack Middleware for filtering domains

domain_filter.rb

class DomainFilter
  def initialize(app, domain, &block)
    @external_app = app
    @domain_app = Rack::Builder.new(&block)
    @domain = domain
  end

  def call(env)
    if env["HTTP_HOST"].match(@domain)
      @domain_app.call(env)
    else
      @external_app.call(env)
    end
  end
end


# use DomainFilter, /\Amy\.domain\.com\z/ do
#   run MySinatraApp
# end
#