#lang racket

(require net/url
         (prefix-in h: html)


;; URL parsing regexp. See 3986. Like the regexp in net/url, but we
;; allow/ignore leading and trailing space.
(define uri-px
  (pregexp (string-append
            "(?:"              ; / scheme-colon-opt
            "([^:/?#]*)"       ; | #1 = scheme-opt
            ":)?"              ; \
            "(?://"            ; / slash-slash-authority-opt
            "(?:"              ; | / user-at-opt
            "([^/?#@]*)"       ; | | #2 = user-opt
            "@)?"              ; | \
            "([^/?#:]*)?"      ; | #3 = host-opt
            "(?::"             ; | / colon-port-opt
            "([0-9]*)"         ; | | #4 = port-opt
            ")?"               ; | \
            ")?"               ; \
            "([^?#]*)"         ; #5 = path
            "(?:\\?"           ; / question-query-opt
            "([^#]*)"          ; | #6 = query-opt
            ")?"               ; \
            "(?:#"             ; / hash-fragment-opt
            "(.*?)"            ; | #7 = fragment-opt
            ")?"               ; \

(define/contract/provide (split-uri uri-string)
  (string? . -> . (values (or/c #f string?)
                          (or/c #f string?)
                          (or/c #f exact-positive-integer?)
                          (or/c #f string?)
                          (or/c #f string?)
                          (or/c #f string?)))
  (match uri-string
    [(pregexp uri-px (list _ scheme user host port path query fragment))
      ;; This is a bit of a hack to accomdate URIs in the real world,
      ;; like what you might find as HREF values on a web page, and
      ;; what most users would type in a browser address bar. e.g.
      ;; "".  If no scheme found, prepend
      ;; "http://" and try again.
      [(not scheme)
       (split-uri (string-append "http://" uri-string))]
        scheme host (and port (string->number port)) path query fragment)])]
    [else (error 'split-uri "can't parse" uri-string)]))

(define/contract/provide (combine-uri [scheme #f]
                                      [host #f]
                                      [port #f]
                                      [path #f]
                                      [query #f]
                                      [fragment #f])
  (() ((or/c #f string?)
       (or/c #f string?)
       (or/c #f exact-positive-integer?)
       (or/c #f string?)
       (or/c #f string?)
       (or/c #f string?))
   . ->* . string?)
  (string-append (if scheme (string-append scheme ":") "")
                 (if host (string-append "//" host) "")
                 (if port (string-append ":" (number->string port)) "")
                 (if (and path (not (string=? path ""))) path "/")
                 (if query (string-append "?" query) "")
                 (if fragment (string-append "#" fragment) "")))

(define/contract/provide (uri->scheme&host&port uri)
   . -> . (values (or/c "http" "https") string? exact-positive-integer?))
      ([(scheme host port path query frag) (split-uri uri)]
       [(scheme) (or scheme "http")]
       [(host) (or host "")]
       [(port) (or port (if (string=? scheme "https") 443 80))])
    (values scheme host port)))

(define/contract/provide (uri&headers->path&header uri heads)
  (string? dict? . -> . (values string? string?))
      ([(scheme host port path query frag) (split-uri uri)]
       [(scheme) (or scheme "")]
       [(host) (or host "")]
       [(port) (or port (if (string=? scheme "https") 443 80))]
       [(host-val) (string-append host (if (= port 80)
                                           "" ;servers may choke on :80
                                           (format ":~a" port)))]
       [(query) (if query (string-append "?" query) "")]
       [(frag) (if frag (string-append "#" frag) "")]
       [(path) (match path
                 [(or #f "") "/"]
                 [else path])]
       [(p+q+f) (string-append path query frag)]
       ;; Automatically add some headers unless supplied by caller
         (maybe-insert-field 'Date
                             (heads-dict->string heads)))])
    (values p+q+f header)))

(define/contract/provide (connect scheme host port)
  ((or/c "http" "https") string? exact-positive-integer?
   . -> . (values input-port? output-port?))
  (log-debug (format "connect ~a ~a ~a" scheme host port))
  (match scheme
    ["https" (ssl-connect host port)]
    ["http" (tcp-connect host port)]))

(define/contract/provide (disconnect in out)
  (input-port? output-port? . -> . any)
  (close-output-port out)
  (close-input-port in))

(define/contract/provide (connect-uri uri)
  (string?  . -> . (values input-port? output-port?))
  (define-values (scheme host port) (uri->scheme&host&port uri))
  (connect scheme host port))

;; When method is "put" or "post", this returns a boolean?. If #t, you
;; should go ahead and transmit the entity (the put or post data),
;; after which you should call purify-port to read the response
;; headers. If #f, you should not transmit the entity data and instead
;; go ahead and call purify-port to read the response headers. (The
;; reason for this is to support Expect 100 Continue.)
;; For other methods, this will always return #t and you should always
;; just go ahead and call purify-port to read the response headers.
(define/contract/provide (start-request in out ver method path heads)
  (input-port? output-port? (or/c "1.0" "1.1") string? string? string?
   . -> . boolean?)
  (log-debug (format "-> ~a ~a HTTP/~a" (string-upcase method) path ver))
  (when (log-level? (current-logger) 'debug)
    (for ([(k v) (in-dict (heads-string->dict heads))])
        (log-debug (format "-> ~a: ~a" k v))))

  (display (format "~a ~a HTTP/~a\r\n" (string-upcase method) path ver) out)
  (display (format "~a" heads) out)
  (100-continue? heads in out))

(define/contract (100-continue? heads in out)
  (string? input-port? output-port? . -> . boolean?)
  ;; If "Expect: 100-continue" is in the req headers, we should read
  ;; from the server here. If it gives "HTTP/1.1 100
  ;; Continue\r\n\r\n" then give it the data, else if response
  ;; header (e.g. redirect) do not actually put any data and instead
  ;; just return the headers as the response.
  (flush-output out)
  (match (extract-field "Expect" heads)
     (log-debug "Request header 'Expect: 100-continue'. Waiting/peeking...")
     (define s (sync/timeout 1.0 in))
       (match (regexp-match-peek-positions
               #rx"^HTTP/1\\.1 100 Continue(?:\r\n\r\n|\n\n|\r\r)"
         [(list (cons _ end))
          (read-string end in)
          (log-debug "Got 100 continue.")
          (log-debug "Did not get 100 continue.")
          ;; Note: Due to using regexp-match-peek-positions, the
          ;; response will remain to read later.
    [else #t]))

;; Examines the Content-Encoding header if any in `h`, and returns a
;; procedure (input-port? output-port? -> void?) which will copy the
;; bytes and decode them. If there no content encoding specified, or
;; an unsupported encoding, this simply returns `copy-port`.
(define/contract/provide (entity-content-decoder/ports h)
  ((or/c string? bytes?) . -> . (input-port? output-port? . -> . any))
  (match (extract-field "Content-Encoding" h)
      [(or "" #f) copy-port]
      ["gzip" gunzip-through-ports]
      ["deflate" inflate]
      [(var ce)
        (format "can't handle Content-Encoding \"~a\"" ce))

;; If you already have read the entity and have it in `bytes?`, you
;; may use this to decode it based on the Content-Encoding header if
;; any in `h`.
(define/contract/provide (entity-content-decode-bytes b h)
  (bytes? (or/c string? bytes?) . -> . bytes?)
  (define/contract (decode func in-bytes)
    ((input-port? output-port? . -> . void?) bytes? . -> . bytes?)
    (let ([in (open-input-bytes in-bytes)]
          [out (open-output-bytes)])
      (func in out)
          (get-output-bytes out)
        (close-input-port in)
        (close-output-port out))))
  (define func (entity-content-decoder/ports h))
  (if (equal? copy-port func)
      b ; avoid pointless copy
      (decode func b)))

;; This is the core procedure to read an HTTP entity in accordance
;; with the `Transfer-Encooding` header. It returns a custom
;; `input-port?` from which you can read the entity until the port
;; returns `eof`. By giving you the port and letting you do the reads,
;; you can read a very large entity in small pieces (to provide a
;; progress indicator, or simply to avoid consuming memory on one
;; large `bytes?` object).
(define/contract/provide (read-entity/transfer-decoding-port in h)
  (input-port? (or/c string? bytes?) . -> . input-port?)
  (define te (or (extract-field "Transfer-Encoding" h) ""))
  (define cl (extract-field/number "Content-Length" h 10))

  (define (read/no-op dst)
    (log-warning "can't read until eof using HTTP 1.1")

  (define (read/to-eof dst)
    (read-bytes! dst in))

  (define read/not-chunked
    (let ([remaining cl])
      (lambda (dst)
        (define to-do (min remaining (bytes-length dst)))
        (log-debug (format "remaining ~a to-do ~a" remaining to-do))
         [(or (zero? remaining)
              (zero? to-do))
          (log-debug "returning eof from zero? remaining or to-do")
          (define done (read-bytes! dst in 0 to-do))
           [(eof-object? done)
            (set! remaining 0)
            (log-debug "returning eof from eof-object? done")
            (set! remaining (- remaining done))

  (define read/chunked
    (let ([chunk #f])
      (lambda (dst)
        (when (not chunk)
          (set! chunk (get-next-chunk in)))
         [(eof-object? chunk)
          (define to-do (min (bytes-length dst) (bytes-length chunk)))
          ;; (log-debug (format "<- dst ~a chunk ~a to-do ~a"
          ;;                    (bytes-length dst) (bytes-length chunk) to-do))
           [(zero? to-do) eof]
            (bytes-copy! dst 0 chunk 0 to-do)
             [(= to-do (bytes-length chunk))
              (set! chunk (get-next-chunk in))]
              (set! chunk (subbytes chunk to-do (bytes-length chunk)))])

  (define read-in
     ;; If Transfer-Encoding is "chunked", read chunked (duh).
     [(string-ci=? te "chunked") read/chunked]
     ;; If Content-Length supplied, read exactly that amount.
     [cl read/not-chunked]
     ;; If connection will be closed, just read to eof.
     [(close-connection? h) read/to-eof]
     ;; Else nothing good we can do. With 1.1 persistent connection
     ;; there is no meaingful "eof".
     [else read/no-op]))

  (make-input-port 'http-entity-transfer-decoding-input-port
                   #f                   ;peek
                   (lambda () (void)))) ;close

;; Read another chunk for Transfer-Encoding: Chunked.
(define/contract (get-next-chunk in)
  (input-port? . -> . (or/c eof-object? bytes?))
  (define s (read-line in 'any))
  (define chunk-size (string->number (string-trim s) 16))
  ;; (log-debug (format "<- entity chunk size ~a" chunk-size))
   [(or (not chunk-size) (zero? chunk-size)) ;last chunk is 0 bytes
    (read-bytes-line in 'any) ;consume final blank line
        (read-bytes chunk-size in)
      (read-bytes-line in 'any))])) ;consume final blank line

(define/contract/provide (read-entity/port in h out)
  (input-port? (or/c string? bytes?) output-port? . -> . any)
  (let ([in (read-entity/transfer-decoding-port in h)])
    ((entity-content-decoder/ports h) in out)))

;; When you don't care about reading the entire entity into memory, or
;; don't care about providing a progress indicator, you can simply use
;; read-entity/bytes which returns the decoded entity as `bytes?`.
(define/contract/provide (read-entity/bytes in h)
  (input-port? (or/c string? bytes?) . -> . bytes?)
  (define out (open-output-bytes))
  (read-entity/port in h out)
  (get-output-bytes out))

;; Rather than return raw bytes?, this uses Content-Type header if any
;; to pick a more suitable representation as an xexpr?.
(define/contract/provide (read-entity/xexpr in h)
  (input-port? (or/c string? bytes?) . -> . xexpr?)

  (define (html-bytes->xexpr by)
    (define (get-element-from-port in)
      (define x (h:read-html-as-xml in))
      (make-element #f #f '***entity*** '() x))
    (third (xml->xexpr (call-with-input-bytes by get-element-from-port))))

  (define by (read-entity/bytes in h))
  (define ct (or (extract-field "Content-Type" h) ""))
  ;; TO-DO: Handle charset= part of Content-Type correctly, here, or
  ;; up to caller to handle?
   [(or (regexp-match? #rx"^text/xml" ct)
        (regexp-match? #rx"^application/xml" ct)
        (and (string=? "" ct)           ;no Content-Type specified
             (regexp-match? #px"^\\s*<\\?xml" by))) ;starts like XML
    (xml->xexpr (document-element (read-xml (open-input-bytes by))))]
   [(regexp-match? #rx"^text/html" ct)
    (html-bytes->xexpr by)]
   [(regexp-match? #rx"^text/plain" ct)
    (format "~a" by)]
   [(regexp-match? #rx"^application/x-www-form-urlencoded" ct)
    `(data ,(form-urlencoded->alist (bytes->string/utf-8 by)))]
    `(entity () ,(format "~a" by))]))


(define (string-trim s)
  (match s
    [(pregexp "^\\s*?(\\S*)\\s*?$" (list _ s)) s]
    [else s]))


(define MONTHS
  #("Jan" "Feb" "Mar" "Apr" "May" "Jun"
    "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"))
(define DAYS
  #("Sun" "Mon" "Tue" "Wed" "Thu" "Fri" "Sat"))

;; two-digits : num -> str
(define (two-digits n)
  (let ([str (number->string n)])
    (if (< n 10) (string-append "0" str) str)))

(define/provide (seconds->gmt-string [s (current-seconds)])
  (define date (seconds->date s #f))
  (format "~a, ~a ~a ~a ~a:~a:~a GMT"
          (vector-ref DAYS (date-week-day date))
          (two-digits (date-day date))
          (vector-ref MONTHS (sub1 (date-month date)))
          (date-year date)
          (two-digits (date-hour date))
          (two-digits (date-minute date))
          (two-digits (date-second date))))

(define/contract/provide (gmt-string->seconds s)
  (string? . -> . exact-integer?)
  (match s
       "([A-Z]{1,1}[a-z]{2,2}), "          ;weekday, e.g. "Mon"
       "(\\d{1,2}) "                       ;day, e.g. "01"
       "([A-Z]{1,1}[a-z]{2,2}) "           ;month, e.g. "Jan"
       "(\\d{4,4}) "                       ;year, e.g. "2012"
       "(\\d{2,2}):(\\d{2,2}):(\\d{2,2}) " ;hr:mn:sec
       "(.{3,4}?)"                         ;timezone, e.g. GMT or 0:00
      (list _ week-day day month year hr mn sc tz))
     (find-seconds (string->number sc)
                   (string->number mn)
                   (string->number hr)
                   (string->number day)
                   (for/or ([i (in-range (vector-length MONTHS))])
                       (if (string=? (vector-ref MONTHS i) month)
                           (add1 i)
                   (string->number year)
     (error 'gmt-string->seconds "expcted date string, got ~a" s)]))

;; seconds->gmt-8601-string
;; YYYY-MM-DDThh:mm:ss.000Z, as specified in the ISO 8601 standard.
(define/contract/provide (seconds->gmt-8601-string [style 'T/Z]
                                                   [s (current-seconds)])
  (() ((or/c 'plain 'T/Z 'T/.000Z) exact-integer?) . ->* . string?)
  (define date (seconds->date s #f))
  (format "~a-~a-~a~a~a:~a:~a~a"
          (date-year date)
          (two-digits (date-month date))
          (two-digits (date-day date))
          (match style
            [(or 'T/Z 'T/.000Z) "T"]
            ['plain " "])
          (two-digits (date-hour date))
          (two-digits (date-minute date))
          (two-digits (date-second date))
          (match style
            ['T/Z "Z"]
            ['T/.000Z ".000Z"]
            ['plain ""])))

(define/contract/provide (gmt-8601-string->seconds s)
  (string? . -> . exact-integer?)
  (match s
       "(\\d{4})-(\\d{2})-(\\d{2})"     ;YYYY-MM-DD
       "(T| ){1}"                       ;separator
       "(\\d{2}):(\\d{2}):(\\d{2})"     ;hr:mn:sc
       "(\\.\\d{3})*"                   ;subseconds
       "(Z)*"                           ;timezone
       (list _ year month day T hr mn sc _ _))
     (find-seconds (string->number sc)
                   (string->number mn)
                   (string->number hr)
                   (string->number day)
                   (string->number month)
                   (string->number year)
     (error 'gmt-8601-string->seconds
            "expected RFC 8601 date string, got ~a" s)]))


(define/contract/provide (purify-port/log-debug in)
  (input-port? . -> . string?)
  (define h (purify-port in))
  (when (log-level? (current-logger) 'debug)
    (for ([(k v) (in-dict (heads-string->dict h))])
        (log-debug (format "<- ~a: ~a" k v))))


(define/contract/provide (redirect-uri h)
  (string? . -> . (or/c #f string?))
  (case (extract-http-code h)
    [(301 302 303 305 307) (extract-field "Location" h)]
    [else #f]))

;; Do the two URLs respresent the same connection, i.e. the exact same
;; scheme, host, and port?
(define/contract/provide (same-connection? old new)
  (url? url? . -> . boolean?)
  (equal? (url-scheme old) (url-scheme new))
  (equal? (url-host old) (url-host new))
  (equal? (url-port old) (url-port new)))

;; Based on response headers, should the connection be closed?
(define/contract/provide (close-connection? h)
  (string? . -> . boolean?)
  (or (equal? "1.0" (extract-http-ver h))
      (let ([s (extract-field "Connection" h)])
        (and s (string-ci=? s "close")))))


;; call/requests provides a way to make one or more requests to the
;; same host connection, and ensure the ports are closed even if there
;; is an exception. `proc' is responsible for doing everything else,
;; such as calling `start-request', `purify-port/log-debug',
;; `read-entity/bytes', and so on.
(define/contract/provide (call/requests scheme host port proc)
  ((or/c "http" "https")
   (input-port? output-port? . -> . any/c)
   . -> . any/c)
  (define-values (in out) (connect scheme host port))
  (dynamic-wind (lambda () (void))
                (lambda () (proc in out))
                (lambda () (disconnect in out))))

(define/contract (call/request ver method uri data heads proc redirects)
  ((or/c "1.0" "1.1")
   (or/c #f bytes? (output-port? . -> . void?))
   (input-port? string? . -> . any/c)
   . -> . any/c)
  (define-values (scheme host port) (uri->scheme&host&port uri))
  (call/requests scheme host port
                 (lambda (in out)
                   (request/redirect ver method in out uri data heads
                                     proc redirects))))

;; Knows how to handle redirects.
;; Expects heads to already contain a Content-Length header.
(define/contract (request/redirect ver method in out uri data heads
                                   proc redirects)
  ((or/c "1.0" "1.1")
   (or/c #f bytes? (output-port? . -> . void?))
   (input-port? string? . -> . any/c)
   . -> . any/c)
  (define-values (path rh) (uri&headers->path&header uri heads))
  (define tx-data? (start-request in out ver method path rh))
  (when (and tx-data? data)
     [(bytes? data) (display data out)]
     [(procedure? data) (data out)])
    (flush-output out))
  (define h (purify-port/log-debug in))
  (define location (redirect-uri h))
   [(and location (> redirects 0))
    (read-entity/bytes in h) ;consume/ignore
    (define old-url (string->url uri))
    (define new-url (combine-url/relative old-url location))
    ;; Can we use the existing connection for the new location?
     [(and (same-connection? old-url new-url)
           (not (close-connection? h)))
      (log-info (format "<> Redirect ~a using SAME connection. ~a ~a"
                        redirects location (url->string new-url)))
      (request/redirect ver method in out (url->string new-url)
                        data heads proc (sub1 redirects))]
      ;; No
      (log-info (format "<> Redirect ~a using NEW connection. ~a ~a"
                        redirects location (url->string new-url)))
      (disconnect in out) ;go ahead and close now to free up connections
      (call/request ver method (url->string new-url) data heads proc
                    (sub1 redirects))])]
   [else (proc in h)]))

;; call/input-request is a simpler version of `call/request` for the
;; case where you want to make just one request and it is not a put or
;; post request (there is no data to send). As a result, the callback
;; proc is passed just the response header and the input port. Like
;; `call/request` it gurantees the ports will be closed.
(define/provide (call/input-request ver method uri heads proc
                                    #:redirects [redirects 10])
  (call/request ver method uri #f heads proc redirects))

;; call/output-request is a simpler version of `call/request` for the
;; case where you want to make just one request and it is a put or
;; post request. The data may be passed as bytes? or as a procedure
;; that will write to an output-port?; if the latter, you must pass
;; `len' unless you have already supplied a Content-Length header
;; yourself.
(define/contract/provide (call/output-request ver method uri data len heads proc
                                              #:redirects [redirects 10])
  (((or/c "1.0" "1.1")
    (or/c bytes? (output-port? . -> . void?))
    (or/c #f exact-nonnegative-integer?)
    (input-port? string? . -> . any/c))
   (#:redirects exact-nonnegative-integer?)
   . ->* . any/c)
  (call/request ver method uri data (maybe-add-cl heads data len) proc

(define (maybe-add-cl dict data len)
  (define cl (cond
              [len len]
              [data (bytes-length data)]
              [else #f]))
     (maybe-insert-field "Content-Length" cl (heads-dict->string dict)))]
   [else dict]))


;; Equivalents for net/url
;; Why use these instead? They support:
;; 1. SSL (only added in Racket 5.?.?
;; 2. "Expect: Continue 100" header, for big put/post requests.

(define http-ver (make-parameter "1.0"))
(provide http-ver)

(define/contract/provide (xxx-impure-port method url heads data)
  (string? url? dict? (or/c #f bytes?) . -> . input-port?)
  (define uri (url->string url))
  (define-values (in out) (connect-uri uri))
  (define new-heads
    (if data
         (maybe-insert-field "Content-Length"
                             (bytes-length data)
                             (heads-dict->string heads)))
  (define-values (path rh) (uri&headers->path&header uri new-heads))
  (define tx-data? (start-request in out (http-ver) method path rh))
  (when (and data tx-data?)
    (display data out))
   [(tcp-port? out) (tcp-abandon-port out)]
   [(ssl-port? out) (ssl-abandon-port out)]
   [(output-port? out) (close-output-port out)])

(define/contract/provide (head-impure-port* url [heads #hash()])
  ((url?) (dict?) . ->* . input-port?)
  (xxx-impure-port "head" url heads #f))

(define/contract/provide (get-impure-port* url [heads #hash()])
  ((url?) (dict?) . ->* . input-port?)
  (xxx-impure-port "get" url heads #f))

(define/contract/provide (delete-impure-port* url [heads #hash()])
  ((url?) (dict?) . ->* . input-port?)
  (xxx-impure-port "delete" url heads #f))

(define/contract/provide (put-impure-port* url data [heads #hash()])
  ((url? bytes?) (dict?) . ->* . input-port?)
  (xxx-impure-port "put" url heads data))

(define/contract/provide (post-impure-port* url data [heads #hash()])
  ((url? bytes?) (dict?) . ->* . input-port?)
  (xxx-impure-port "post" url heads data))

;; test

(module+ test
  (require rackunit)
  ;; Confirm HTTP 1.1. processing working correctly by doing two
  ;; requests over the same persistent connection.
  (define (get-twice uri)
    (define heads (hash 'Accept "text/html,text/plain"
                        'Accept-Encoding "gzip,deflate"))
    (define-values (in out) (connect-uri uri))
    (define-values (path rh) (uri&headers->path&header uri heads))
    (define/contract (get)
      (-> (or/c #f 'ok/open 'ok/close))
      (start-request in out "1.1" "get" path rh)
      (define h (purify-port/log-debug in))
      (define code (extract-http-code h))
       [(= code 999)
        (define e (read-entity/bytes in h))
        (log-debug (format "<- ~a bytes entity transfer and content decoded"
                           (bytes-length e)))
        (match (extract-field "Connection" h)
          [(regexp "(?i:close)") 'ok/close]
          [else 'ok/open])]))
    (define result (match (get)
                      (not (not (get)))]  ;try again on same connection
                      (log-debug "can't try again, due to Connection: close")
                     [else #f]))
    (disconnect in out)

  ;; Non I/O tests
   (check-true (close-connection? (string-append "HTTP/1.1 200 OK\r\n"
                                                 "Connection: close\r\n"
   (check-true (close-connection? "HTTP/1.0 200 OK\r\n\r\n"))
   (check-false (close-connection? "HTTP/1.1 200 OK\r\n\r\n")))

   (define-values (s h pt pth q f)
     (split-uri ""))
   (check-equal? s "http")
   (check-equal? h "")
   (check-equal? pt 80)
   (check-equal? pth "/path/to/res")
   (check-equal? q "a=1&b=2")
   (check-equal? f "fragment"))

   (check-equal? (combine-uri "http"

   (check-equal? (redirect-uri "HTTP/1.0 200 OK\r\n\r\n")
   (check-equal? (redirect-uri (string-append "HTTP/1.0 301\r\n"
                                              "Location: foobar\r\n"
   (check-equal? 0
                 (gmt-string->seconds (seconds->gmt-string 0)))
   (define s (current-seconds))
   (check-equal? s
                 (gmt-string->seconds (seconds->gmt-string s))))

   (check-equal? (seconds->gmt-8601-string 'plain 0)
                 "1970-01-01 00:00:00")
   (check-equal? (seconds->gmt-8601-string 'T/Z 0)
   (check-equal? (seconds->gmt-8601-string 'T/.000Z 0)

   (define s (current-seconds))
   (check-equal? (gmt-8601-string->seconds (seconds->gmt-8601-string 'plain s))
   (check-equal? (gmt-8601-string->seconds (seconds->gmt-8601-string 'T/Z s))
   (check-equal? (gmt-8601-string->seconds (seconds->gmt-8601-string 'T/.000Z s))

   (check-equal? (call-with-values
                     (lambda ()
                       (uri->scheme&host&port ""))
                 (list "http" "" 8080))
   (check-equal? (call-with-values
                     (lambda ()
                       (uri->scheme&host&port ""))
                 (list "https" "" 443)))

   (define heads (hash 'Date (format "Date: ~a" (seconds->gmt-string))
                       'Content-Length "123"))
   (define uri "" )
   (define-values (p h) (uri&headers->path&header uri heads))
   (check-equal? p "/path?query#frag")
   ;; did it append the Host header automatically?
   ;; (check-equal? (sort (heads-string->list h) string<?)
   ;;               (sort (append xs `("Host:")) string<?))

  ;; ----------------------------------------------------------------------
  ;; Tests that do I/O
  (define (extra-uris-to-test)
    (define (strip-comment s)
      (match s
        [(pregexp "^(.*?)\\s+#" (list _ x)) x]
        [(pregexp "^\\s*#") ""]
        [else s]))
    (define (strip-space s)
      (match s
        [(pregexp "^\\s*(\\S+)\\s*$" (list _ uri)) uri]
        [else #f]))
    (define (strip-comment-and-space s)
      (strip-space (strip-comment s)))
    (filter-map strip-comment-and-space
                (with-handlers ([exn:fail? (lambda (exn) '())])
                  (file->lines (build-path 'same "tests" "extra-uris")
                               #:mode 'text #:line-mode 'any))))

  (define xs-uri-to-test
       "" ;will do multiple redirects, diff ctx

  (for ([x (in-list xs-uri-to-test)])
      (test-case (string-append "Actual I/O test, get-twice " x)
                 (check-true (get-twice x))))
  (for ([x (in-list xs-uri-to-test)])
      (test-case (string-append "call/input-request, no encoding " x)
                  (call/input-request "1.1" "GET" x
                                      #:redirects 10
                                      (hash 'Accept "text/html,text/plain")
                                      (lambda (in h)
                                        (read-entity/bytes in h)
  (for ([x (in-list xs-uri-to-test)])
      (test-case (string-append "call/input-request, gzip,deflate " x)
                  (call/input-request "1.1" "GET" x
                                      #:redirects 10
                                       'Accept "text/html,text/plain"
                                       'Accept-Encoding "gzip,deflate")
                                      (lambda (in h)
                                        (read-entity/bytes in h)