add currently visited document, pre-rendering, to global state

its becoming apparent that this doesn't need to be global state, and
can be passed from iteration to iteration in the program loop. this
shall be revisited

gem300.rkt

@@ -7,15 +7,20 @@
 ;; rendered out gemtext document as it shall be shown to the user
 (define document-buffer null)
 
+;; global state which will be the document structure, before rendering
+(define document null)
+
 (define (go-cmd url)
   (if (non-empty-string? url)
       (let-values ([(status meta c-in) (net:get url)])
-        (let-values ([(document) (gmi:parse (port->lines c-in))]
+        (let-values ([(doc) (gmi:parse (port->lines c-in))]
                      [(db-in db-out) (make-pipe #f)])
 
+          (set! document doc)
+
           (set! document-buffer db-in)
           (parameterize ([current-output-port db-out])
-            (gmi:render document))
+            (gmi:render doc))
 
           (let ([remaining (pipe-content-length db-in)])
             (printf "document retrieved. ~a bytes\n" remaining))