Trying out HTTP 103 Early Hints

src/dispatcher-tree.rkt

@@ -8,7 +8,9 @@
          (prefix-in sequencer: web-server/dispatchers/dispatch-sequencer)
          (prefix-in lift: web-server/dispatchers/dispatch-lift)
          (prefix-in filter: web-server/dispatchers/dispatch-filter)
+         web-server/private/connection-manager
          "config.rkt"
+         "static-data.rkt"
          "url-utils.rkt")
 
 (provide
@@ -31,6 +33,24 @@
   ; don't forget that I'm returning *code* - return a call to the function
   (datum->syntax stx `(make-dispatcher-tree ,ds)))
 
+(define (write-bytes* out . bs)
+  (for ([b bs]) (write-bytes b out)))
+
+;; HTTP 103 Early Hints https://datatracker.ietf.org/doc/html/rfc8297
+;; a dispatcher services a request or calls next-dispatcher
+(define ((early-hints:make original-dispatcher) conn req)
+  ;; normally this would call output-response/method to write output based on the method
+  ;; e.g. if it's HEAD then only output the headers
+  (define o (connection-o-port conn))
+  (write-bytes* o
+                #"HTTP/1.1 103 Early Hints\r\n"
+                #"Link: " (string->bytes/latin-1 link-header) #"\r\n"
+                #"\r\n")
+  (flush-output o)
+  ;; after doing early hints, I need to run the original dispatcher to generate the real response.
+  ;; dispatchers do not return anything.
+  (original-dispatcher conn req))
+
 (define (make-dispatcher-tree ds)
   (host:make
    (λ (host-sym)
@@ -47,7 +67,7 @@
               (pathprocedure:make "/buddyfight/wiki/It_Doesn't_Work!!" (hash-ref ds 'page-it-works))
               (filter:make (pregexp (format "^/~a/wiki/Category:.+$" px-wikiname)) (lift:make (hash-ref ds 'page-category)))
               (filter:make (pregexp (format "^/~a/wiki/File:.+$" px-wikiname)) (lift:make (hash-ref ds 'page-file)))
-              (filter:make (pregexp (format "^/~a/wiki/.+$" px-wikiname)) (lift:make (hash-ref ds 'page-wiki)))
+              (filter:make (pregexp (format "^/~a/wiki/.+$" px-wikiname)) (early-hints:make (lift:make (hash-ref ds 'page-wiki))))
               (filter:make (pregexp (format "^/~a/search$" px-wikiname)) (lift:make (hash-ref ds 'page-search)))
               (filter:make (pregexp (format "^/~a(/(wiki(/)?)?)?$" px-wikiname)) (lift:make (hash-ref ds 'redirect-wiki-home)))
               (hash-ref ds 'static-dispatcher)