Accept HTML from stdin, instead of requiring a file

This is much more handy (not to mention UNIX-y)!

src/mirror-img.lisp

@@ -28,16 +28,17 @@
 
 ;;; Mirror-img
 ;;; ————————————————————————————————————————
-;; pathname pathname list → string
+;; pathname/input-stream pathname list → string
-(defun mirror-img (html-file download-dir &key (url-dir download-dir) (tags *default-tags*))
+(defun mirror-img (html-source download-dir &key (url-dir download-dir) (tags *default-tags*))
-  "Attempt to mirror all remote HREF/SRC URLs of an HTML file’s tags,
+  "Attempt to mirror all remote HREF/SRC URLs of an HTML document’s tags,
 downloading them to DOWNLOAD-DIR. For each remote URL that could be
 successfuly mirrored, the remote URLs will be replaced with the local
 version. The URL used will will be BASE-DIR plus the filename, where
 BASE-DIR defaults to DOWNLOAD-DIR.
+HTML-SOURCE, the document, can be either a pathname or an input stream.
 Returns a string of the modified page’s HTML."
   (let* ((dom
-           (lquery:$ (lquery:initialize html-file)))
+           (lquery:$ (lquery:initialize html-source)))
          (url→pathname-alist
            (mirror-linked-urls dom :tags tags :download-dir download-dir))
          (url→relative-url-alist

src/unix.lisp

@@ -38,22 +38,22 @@
 
 ;;; Mirror-img (UNIX)
 ;;; ————————————————————————————————————————
-;; NIL → NIL
+;; nil → nil
 (defun main ()
   "Actual invocation of the program. This is what you should set as :toplevel."
   (error-print
    99 ""
    (multiple-value-bind (opts free) (opts:get-opts)
      (when-opt opts :help (help))
-     (let* ((input-file   (car free))
+     (let* ((input-stream (choose-input-stream (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)
+       (when (not input-stream)
-         (error-print 1 "No HTML file provided. Use --help for more information."))
+         (error-print 1 "No HTML file provided. See --help for more information."))
        (format
         't
         (mirror-img:mirror-img
-         (pathname input-file)
+         input-stream
          download-dir
          :url-dir url-base))))))
 
@@ -77,7 +77,10 @@
 ;; number stream → nil
 (defun help (&optional (exit-code 0) (stream *standard-output*))
   "Prints help message and dies."
-  (unix-opts:describe :prefix "usage: mirror-img [-h] [-d DIR] [-b BASE] HTML_FILE"
+  (unix-opts:describe
+   :prefix (format nil "~A~%~A"
+                   "usage: mirror-img [-h] [-d DIR] [-b BASE] HTML_FILE"
+                   "       mirror-img [-h] [-d DIR] [-b BASE]")
    :stream stream)
   (unix-opts:exit exit-code))
 
@@ -86,3 +89,25 @@
   "Print an error-message and exit."
   (format *error-output* "~@[~A~%~]~@[~A~%~]" message condition)
   (unix-opts:exit exit-code))
+
+
+
+;;; Input
+;;; ————————————————————————————————————————
+;; list → stream
+(defun choose-input-stream (file-arg)
+  "Select an input stream, between a file passed in free-args or stdin."
+  (let* ((input-file   file-arg)
+         (input-file-p (ignore-errors (probe-file input-file)))
+         (stdinp      (listen *standard-input*)))
+    (cond ((or stdinp (equal input-file "-")) ; “-” is commonly used to mean stdin.
+           *standard-input*)
+          (input-file-p (open input-file))
+          ((and input-file (not input-file-p))
+           (error-print 2 "File “~A” does not exist." input-file))
+          ('T
+           ;; Warn the user, if we’re reading from stdin (without immediate input).
+           ;; This means they might’ve made a massive typo. ^ ^
+           (format *error-output* "Reading from standard input. Hit ^D (CTRL+D) when done.~%")
+           (format *error-output* "Run with --help argument for details.~%")
+           *standard-input*))))