method: ~a" (substring str start end)))))

(define* (parse-request-uri str #:optional (start 0) (end (string-length str)))
  "Parse a URI from an HTTP request line.  Note that URIs in requests do
not have to have a scheme or host name.  The result is a URI-reference
object."
  (cond
   ((= start end)
    (bad-request "Missing Request-URI"))
   ((string= str "*" start end)
    #f)
   ((eqv? (string-ref str start) #\/)
    (let* ((q (string-index str #\? start end))
           (f (string-index str #\# start end))
           (q (and q (or (not f) (< q f)) q)))
      (build-uri-reference
       #:path (substring str start (or q f end))
       #:query (and q (substring str (1+ q) (or f end)))
       #:fragment (and f (substring str (1+ f) end)))))
   (else
    (or (string->uri (substring str start end))
        (bad-request "Invalid URI: ~a" (substring str start end))))))

(define (read-request-line port)
  "Read the first line of an HTTP request from PORT, returning
three values: the method, the URI, and the version."
  (let* ((line (read-header-line port))
         (d0 (string-index line char-set:whitespace)) ; "delimiter zero"
         (d1 (string-rindex line char-set:whitespace)))
    (unless (and d0 d1 (< d0 d1))
      (bad-request "Bad Request-Line: ~s" line))
    (values (parse-http-method line 0 d0)
            (parse-request-uri line (skip-whitespace line (1+ d0) d1) d1)
            (parse-http-version line (1+ d1) (string-length line)))))

(define (write-uri uri port)
  (put-string port (uri->string uri #:include-fragment? #f)))

(define (write-request-line method uri version port)
  "Write the first line of an HTTP request to PORT."
  (put-symbol port method)
  (put-char port #\space)
  (when (http-proxy-port? port)
    (let ((scheme (uri-scheme uri))
          (host (uri-host uri))
          (host-port (uri-port uri)))
      (when (and scheme host)
        (put-symbol port scheme)
        (put-string port "://")
        (cond
         ((string-index host #\:)
          (put-char port #\[)
          (put-string port host)
          (put-char port #\]))
         (else
          (put-string port host)))
        (unless ((@@ (web uri) default-port?) scheme host-port)
          (put-char port #\:)
          (put-non-negative-integer port host-port)))))
  (let ((path (uri-path uri))
        (query (uri-query uri)))
    (if (string-null? path)
        (put-string port "/")
        (put-string port path))
    (when query
      (put-string port "?")
      (put-string port query)))
  (put-char port #\space)
  (write-http-version version port)
  (put-string port "\r\n"))

(define (read-response-line port)
  "Read the first line of an HTTP response from PORT, returning three
values: the HTTP version, the response code, and the (possibly empty)
\"reason phrase\"."
  (let* ((line (read-header-line port))
         (d0 (string-index line char-set:whitespace)) ; "delimiter zero"
         (d1 (and d0 (string-index line char-set:whitespace
                                   (skip-whitespace line d0)))))
    (unless (and d0 d1)
      (bad-response "Bad Response-Line: ~s" line))
    (values (parse-http-version line 0 d0)
            (parse-non-negative-integer line (skip-whitespace line d0 d1)
                                        d1)
            (string-trim-both line char-set:whitespace d1))))

(define (write-response-line version code reason-phrase port)
  "Write the first line of an HTTP response to PORT."
  (write-http-version version port)
  (put-char port #\space)
  (put-non-negative-integer port code)
  (put-char port #\space)
  (put-string port reason-phrase)
  (put-string port "\r\n"))