#lang racket
(define (robots-field name (body '()))
  (define robots-field-base (string-append name ":"))
  (if (nil? body) robots-field-base
      (string-append robots-field-base " " body)))

(define (robots-ua (name "*"))
  (string-append "User-agent: " name))

(define (robots-disallow list)
  (if (empty? list)
      "Disallow:"

(define (robots-config (#:crawl-delay 10))
  (string-append
   (robots-ua)
   (