Add crawler handling for correct urls, response codes 301, 302, 403, 404, 500

private/util.rkt

@@ -2,7 +2,7 @@
 
 (require xml)
 
-(provide debug-mode? printf-debug print-progress print-complete
+(provide debug-mode? printf-debug print-progress print-complete print-flag
          current-cookie-jar update-cookie-jar! cookie-jar->header cookie-jar-ref
          string->xexpr find-flags find-hrefs)
 
@@ -33,6 +33,12 @@
   (when (debug-mode?)
     (printf "\r\x1b[KCrawl complete\n")))
 
+;; Str ->
+;; Prints a flag
+(define (print-flag flag)
+  (if (debug-mode?)
+    (printf "\r\x1b[K~a\n" flag) ; make sure not to garble the debug progess
+    (displayln flag)))
 
 ;; Cookie jar
 (struct cj [jar cache sema] #:transparent)

smol-http/http-msg.rkt

@@ -3,6 +3,7 @@
          http-msg-headers
          http-msg-header
          http-msg-body
+         http-rsp-code
          write-http-msg
          read-http-msg
          http-add-headers
@@ -62,6 +63,11 @@
     [(assoc k (http-msg-headers msg)) => cdr]
     [else #f]))
 
+;; (http-rsp-code msg) -> http-response-code?
+;; msg : http-rsp?
+(define (http-rsp-code msg)
+  (http-start-line:res-code (http-msg-start-line msg)))
+
 ;; (http-add-headers msg hdrs) -> http-msg?
 ;; msg : http-msg?
 ;; hdrs : (listof (cons/c symbol? any?))

webcrawler

@@ -9,7 +9,8 @@
 ;  /_//_/ /_/\__,_/_/ /_/\__, /   \__,_/ |__/|__/\__,_/
 ;                       /____/
 
-(require smol-http
+(require net/url-string
+         smol-http
          "private/util.rkt")
 
 (define HOST "fring.ccs.neu.edu")
@@ -19,46 +20,89 @@
                        ;; christo pls do not track thanks
                        (dnt . "1")))
 
-(define (crawler-fetch/noclose req)
-  (define sock (http-connect HOST
-                             #:headers (cons (cookie-jar->header (current-cookie-jar))
+;; Returns response for request without closing the socket
+(define (crawler-fetch/noclose method path [body #f])
+  (define req
+    (let ([basic-req (make-http-req method path '())])
+      (if body (http-set-body basic-req body) basic-req)))
+  (define sock
+    (http-connect
+      HOST #:headers (cons (cookie-jar->header (current-cookie-jar))
                            DEFAULT-HDRS)))
   (define rsp (http-request sock req))
   (update-cookie-jar! (current-cookie-jar) (http-msg-headers rsp))
-  (values rsp sock))
+  (match (http-rsp-code rsp)
+    [(or 301 302)
+     ;; handle redirects transparently
+     (define new-location (http-msg-header rsp 'location))
+     (http-close sock)
+     (crawler-fetch/noclose method new-location body)]
+    [500
+     ;; handle server failure retries transparently
+     (crawler-fetch/noclose method path body)]
+    [_
+     ;; other stuff like 403/404 up to caller
+     (values rsp sock)]))
 
-(define (crawler-fetch req)
-  (define-values [rsp sock] (crawler-fetch/noclose req))
+;; Returns response for request, closing socket
+(define (crawler-fetch . params)
+  (define-values [rsp sock] (apply crawler-fetch/noclose params))
   (http-close sock)
   rsp)
 
-(define (crawler-fetch/xexpr req)
-  (define-values [rsp sock] (crawler-fetch/noclose req))
-  (define xe (string->xexpr
+;; Fetches request and tries to parse the result as xexpr
+(define (crawler-fetch/xexpr . params)
+  (define-values [rsp sock] (apply crawler-fetch/noclose params))
+  (match (http-rsp-code rsp)
+    [(or 403 404)
+     (http-close sock)
+     '()]
+    [200
+     (define xe
+       (string->xexpr
          (bytes->string/utf-8
            (for/fold ([res #""])
              ([chunk (in-http-body-chunks (http-msg-body rsp))])
              (bytes-append res chunk)))))
      (http-close sock)
-  xe)
+     xe]
+    [code (http-close sock) (error "unexpected response code" code)]))
 
+;; Logs in with the given username and password
 (define (crawler-login username password)
-  (crawler-fetch (make-http-req 'GET LOGIN-PATH))
+  (crawler-fetch 'GET LOGIN-PATH)
   (define form-body
     (format "username=~a&password=~a&csrfmiddlewaretoken=~a&next="
             username password (cookie-jar-ref (current-cookie-jar) "csrftoken")))
-  (crawler-fetch (http-set-body (make-http-req 'POST LOGIN-PATH)
-                                (string->bytes/utf-8 form-body)))
+  (crawler-fetch 'POST LOGIN-PATH (string->bytes/utf-8 form-body))
   (void))
 
+;; Checks if this is a URL we should crawl
+(define (crawler-valid-url? page-url)
+  (match page-url
+    [(url "http" _ (? (curry equal? HOST)) _ _ _ _ _) #t]
+    [_ #f]))
+
+;; Fetches one page, prints any flags, and returns a list of urls to continue with
+;; (may contain duplicates)
+(define (crawler-iterate-one page-url)
+  (let* ([path (string-join (map path/param-path (url-path page-url)) "/")]
+         [xe (crawler-fetch/xexpr 'GET path)]
+         [flags (find-flags xe)]
+         [page-links (map (lambda (x) (combine-url/relative page-url x))
+                          (find-hrefs xe))])
+    (for ([flag (in-list flags)])
+      (print-flag flag))
+    (filter crawler-valid-url? page-links)))
+
 (define (run-webcrawler username password)
   (printf-debug "the credentials are: ~s ~s\n" username password)
   (printf-debug "logging in...\n")
   (crawler-login username password)
   (printf-debug "logged in\n")
-  (define xe (crawler-fetch/xexpr (make-http-req 'GET ROOT-PATH)))
-  (displayln (find-flags xe))
-  (displayln (find-hrefs xe)))
+  (define base-url (url "http" #f HOST #f #t (list (path/param ROOT-PATH '())) '() #f))
+  (define next-pages (crawler-iterate-one base-url))
+  (displayln (map url->string next-pages)))
 
 (module+ main
   (command-line