; Minimal servlet for getting information out of a request

; This is a magical incantation that makes this file a servlet
; and gives access to useful servlet functionality

(require (lib "unitsig.ss")
         (lib "servlet-sig.ss" "web-server"))

(unit/sig 
    () (import servlet^)
  
  ; Here is where the interesting code actually starts.
  
  ; Get the bindings from the request
  (let ((my-bindings (request-bindings initial-request)))
    (cond
      ; make sure q is defined   
      [(not (exists-binding? 'q my-bindings))
       '(html (head (title "Error"))
              (body ((bgcolor "red"))
                    (p "This page needs you to define q!")))]
      ; make sure r is defined
      [(not (exists-binding? 'r my-bindings))
       '(html (head (title "Error"))
              (body ((bgcolor "blue"))
                    (p "This page needs you to define r!")))]
      ; use the values of q and r to construct a new page
      [else
       (let ((q (car (extract-bindings 'q my-bindings)))
             (r (car (extract-bindings 'r my-bindings))))
         `(html (head (title "Relationships"))
                (body ([bgcolor "white"])
                      (p "Every "
                         ,q
                         " is a "
                         ,r
                         "."))))])))