Support for broken url handling in clients.

Some clients (looking at you, Lynx) actually try to treat the
directory entry for http links as a gopher link instead of going
straight to the provided url.  This update adds a text response that
instructs users of these clients on what to do in this situation.

diff --git a/burrower.scm b/burrower.scm
index a042e58..4d00253 100644 (file)
--- a/burrower.scm
+++ b/burrower.scm
@@ -68,12 +68,22 @@
 
 ;;; Selector type inference
 
-(define (has-suffix? selector . suffixes)
-  (if (null? suffixes)
+(define (true-for-one? predicate values)
+  (if (null? values)
       #f
-      (if (string-suffix? (car suffixes) selector)
+      (if (predicate (car values))
           #t
-          (apply has-suffix? selector (cdr suffixes)))))
+          (true-for-one? predicate (cdr values)))))
+
+(define (has-suffix? selector . suffixes)
+  (true-for-one? (lambda (suffix)
+                   (string-suffix? suffix selector))
+                 suffixes))
+
+(define (has-prefix? selector . prefixes)
+  (true-for-one? (lambda (prefix)
+                   (string-prefix? prefix selector))
+                 prefixes))
 
 (define (infer-selector-type selector)
   (let ((l (string-downcase selector)))
@@ -82,6 +92,7 @@
      ((has-suffix? l ".txt" ".org" ".md") 0)
      ((has-suffix? l ".png" ".jpg" ".gif" ".bmp" ".tif" ".tga") 'I)
      ((has-suffix? l "?.scm") 7)
+     ((has-prefix? l "url:" "/url:") 'h)
      (else 9))))
 
 
@@ -95,6 +106,7 @@
       ((1) (serve-directory selector config))
       ((0) (serve-text-file selector config))
       ((7) (serve-query selector arguments config))
+      ((h) (serve-url selector config))
       (else (serve-binary-file selector config)))))
 
 (define (serve-directory selector config)
@@ -157,6 +169,17 @@
         (error "Invalid query." selector arguments))))
 
 
+(define (serve-url selector config)
+  (let ((url (substring selector 4)))
+    (print
+     "If you are seeing this page, your gopher browser does not\r\n"
+     "properly support URL directory entries or cannot follow such\r\n"
+     "links.  To view the link you requested, use a web browser to\r\n"
+     "open the follwing url:\r\n"
+     "\r\n"
+     url "\r\n")))
+
+
 ;;; Index rendering
 
 (define (serve-info-records string)