Add error-reporting to UNIX cli client

src/unix.lisp

@@ -41,21 +41,21 @@
 ;; NIL → NIL
 (defun main ()
   "Actual invocation of the program. This is what you should set as :toplevel."
-  (multiple-value-bind (opts free) (opts:get-opts)
-    (when-opt opts :help (help))
-    (let* ((input-file   (pathname (car free)))
-           (url-base     (or (getf opts :url-base) (getf opts :download-dir) "mirror/"))
-           (download-dir (or (getf opts :download-dir) url-base)))
-      (when (not input-file)
-        (format *error-output* "No file provided.~%")
-        (help 2))
-
-      (format
-       't
-       (mirror-img:mirror-img
-        input-file
-        download-dir
-        :url-dir url-base)))))
+  (error-print
+   99 ""
+   (multiple-value-bind (opts free) (opts:get-opts)
+     (when-opt opts :help (help))
+     (let* ((input-file   (car free))
+            (url-base     (or (getf opts :url-base) (getf opts :download-dir) "mirror/"))
+            (download-dir (or (getf opts :download-dir) url-base)))
+       (when (not input-file)
+         (error-print 1 "No HTML file provided. Use --help for more information."))
+       (format
+        't
+        (mirror-img:mirror-img
+         (pathname input-file)
+         download-dir
+         :url-dir url-base))))))
 
 (opts:define-opts
   (:name :help
@@ -67,8 +67,12 @@
   (:name :download-dir
    :description "directory for all mirrored files"
    :short #\d :long "downloads"
-   :arg-parser (lambda (dir)
-                 (car (directory dir)))))
+   :arg-parser
+         (lambda (dir)
+           (handler-case
+               (ensure-directories-exist dir)
+             (error (c)
+               (error-print 11 "Could not access or create directory." c))))))
 
 ;; number stream → nil
 (defun help (&optional (exit-code 0) (stream *standard-output*))
@@ -76,3 +80,9 @@
   (unix-opts:describe :prefix "usage: mirror-img [-h] [-d DIR] [-b BASE] HTML_FILE"
                       :stream stream)
   (unix-opts:exit exit-code))
+
+;; number string condition → nil
+(defun error-print (exit-code &optional message condition)
+  "Print an error-message and exit."
+  (format *error-output* "~@[~A~%~]~@[~A~%~]" message condition)
+  (unix-opts:exit exit-code))