Update README.md, mention new --source argument

Now, relative URLs in the input file can be
mirrored in relation to a given URL.

README.md

@@ -6,11 +6,12 @@ file, mirroring its remote images, stylesheets, and other resources.
 
 ## Usage
 ```
-usage: mirror-img [-h] [-d DIR] [-b BASE] HTML_FILE
-       mirror-img [-h] [-d DIR] [-b BASE]
+usage: mirror-img [-h] [-d DIR] [-b BASE] [-s URL] HTML_FILE
+       mirror-img [-h] [-d DIR] [-b BASE] [-s URL]
 Available options:
   -h, --help          print this help text.
-  -b, --base          path to mirror directory used in URLs
+  -b, --base ARG      path to mirror directory used in URLs
+  -s, --source ARG    URL used to resolve & mirror relative URLs
   -d, --downloads ARG directory for all mirrored files
 ```
 
@@ -21,12 +22,28 @@ In order to mirror a webpage, you can simply download it and pipe it into mirror
 $ curl https://www.gnu.org/philosophy/philosophy.html | mirror-img > philosophy.html
 ```
 
-And now `philosophy.html` will be a fully-local HTML file, with no external resources!
-All mirrored content will be found in the `mirror/` directory, and all links
-have been adjusted accordingly.
+And now `philosophy.html` is a fully-local HTML file with no external resources!
+
+… at least, it *would* be. Notice how some resources, like the CSS, don’t load.
+This is because they are defined as *relative* links (e.g., “../style.css”
+rather than “https://invalid.tld/style.css”). In order for these to be
+mirrored as well, mirror-img needs to somehow know the source URL.
+
+You can use the `--source` argument to provide the source URL, so
+relatively-linked resources can be mirrored, too:
+
+```
+$ SOURCE_URL="https://www.gnu.org/philosophy/philosophy.html"
+$ curl "$SOURCE_URL" | mirror-img --source "$SOURCE_URL" > philosophy.html
+```
+
+*Now* we’re done! All mirrored content will be found in the `mirror/`
+directory, and all links have been adjusted accordingly.
+
+---
 
 If you’d like to change the download directory, you can use the `--downloads`
-argument. To change the directory used in the output HTML’s URLs, you can
+argument. To change the directory used in the output-HTML’s URLs, you can
 use `--base`.
 
 For example, if you’d like to mirror files into `/tmp/mirrors/` but have URLs

src/mirror-img.lisp

@@ -28,19 +28,25 @@
 
 ;;; Mirror-img
 ;;; ————————————————————————————————————————
-;; pathname/input-stream pathname list → string
-(defun mirror-img (html-source download-dir &key (url-dir download-dir) (tags *default-tags*))
+;; pathname/input-stream pathname string string list → string
+(defun mirror-img (html-source download-dir
+                   &key html-url
+                     (url-dir download-dir)
+                     (tags *default-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.
+If HTML-URL is provided, then relative URLs in the file will be interpreted
+in relation to HTML-URL.
 Returns a string of the modified page’s HTML."
   (let* ((dom
            (lquery:$ (lquery:initialize html-source)))
          (url→pathname-alist
-           (mirror-linked-urls dom :tags tags :download-dir download-dir))
+           (mirror-linked-urls dom :tags tags :download-dir download-dir
+                                   :html-url html-url))
          (url→relative-url-alist
            (mapcar
             (lambda (pair)
@@ -53,7 +59,7 @@ Returns a string of the modified page’s HTML."
     (aref (lquery:$ dom (serialize)) 0)))
 
 ;; lquery-dom list pathname → alist
-(defun mirror-linked-urls (dom &key (tags *default-tags*) download-dir)
+(defun mirror-linked-urls (dom &key (tags *default-tags*) download-dir (html-url ""))
   "Mirror all URLs in the HREF/SRC attributes of the given tags in an LQuery
 DOM, downloading them to either the current-working directory or the DOWNLOAD-DIR.
 Returns an associative list containing pairs of remote-URLs to local pathnames.
@@ -62,12 +68,16 @@ For example:
     ((“https://downloaded.com/a/b.jpg” . #p“a/b.jpg”))"
   (remove-if
    #'not
-   (mapcar (lambda (url)
-             (let ((download-path
-                     (ensure-directories-exist
-                      (mirrored-pathname url :base-dir download-dir))))
+   (mapcar (lambda (original-url)
+             (let* ((url (if (not (quri:uri-scheme (quri:uri original-url)))
+                             (quri:merge-uris original-url html-url) ; For relative URLs
+                             original-url))
+
+                    (download-path
+                      (ensure-directories-exist
+                       (mirrored-pathname url :base-dir download-dir))))
                (if (http-fetch url download-path)
-                   (cons url download-path))))
+                   (cons original-url download-path))))
     (linked-urls dom :tags tags))))
 
 ;; lquery-dom alist list → nil

src/unix.lisp

@@ -41,7 +41,8 @@
         (when-opt opts :help (help))
         (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)))
+               (download-dir (or (getf opts :download-dir) url-base))
+               (source-url   (getf opts :source-url)))
           (when (not input-stream)
             (error-print 1 "No HTML file provided. See --help for more information."))
           (format
@@ -49,7 +50,8 @@
            (mirror-img:mirror-img
             input-stream
             download-dir
-            :url-dir url-base))))
+            :url-dir url-base
+            :html-url source-url))))
     (error (c)
       (error-print 99 nil c))))
 
@@ -59,7 +61,20 @@
    :short #\h  :long "help")
   (:name :url-base
    :description "path to mirror directory used in URLs"
-   :short #\b :long "base")
+   :short #\b :long "base"
+   :arg-parser (lambda (base) base))
+  (:name :source-url
+   :description "URL used to resolve & mirror relative URLs"
+   :short #\s :long "source"
+   :arg-parser
+         (lambda (source)
+           (handler-case
+               (let ((uri (quri:uri source)))
+                 (if (not (quri:uri-scheme uri))
+                   (error-print 6 "Source URL is not proper (e.g., “https://invalid.tld/”).")
+                   uri))
+             (error (c)
+               (error-print 6 "Source URL is not proper (e.g., “https://invalid.tld/”)." c)))))
   (:name :download-dir
    :description "directory for all mirrored files"
    :short #\d :long "downloads"
@@ -79,8 +94,8 @@
   "Prints help message and dies."
   (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]")
+                   "usage: mirror-img [-h] [-d DIR] [-b BASE] [-s URL] HTML_FILE"
+                   "       mirror-img [-h] [-d DIR] [-b BASE] [-s URL]")
    :stream stream)
   (unix-opts:exit exit-code))
 

t/mirror-img.lisp

@@ -51,10 +51,13 @@ system’s path."
     (setq *mirror-img-result*
           (let* ((html-path    (relative-pathname "t/testing-website/index.html"))
                  (download-dir (relative-pathname "t/tmp/"))
+                 (html-url     "http://localhost:4242")
                  (url-dir      (pathname-utils:relative-pathname
                                 (relative-pathname "t/")
                                 download-dir)))
-            (mirror-img:mirror-img html-path download-dir :url-dir url-dir))))))
+            (mirror-img:mirror-img html-path download-dir
+                                   :url-dir url-dir
+                                   :html-url html-url))))))
 
 (define-test mirror-img.files-mirrored (:tags '(mirror-img))
   (assert-equal
@@ -90,13 +93,13 @@ system’s path."
 
 (define-test linked-urls (:tags '(dom))
   (assert-equal
-   '("http://localhost:4242/res/img/b/fireplace.jpg"
+   '("/res/welcoming you.jpg"
+     "http://localhost:4242/res/img/b/fireplace.jpg"
      "http://localhost:4242/res/img/b/I’m trying hard to randomly name these directories/more_calming.jpg"
      "http://localhost:4242/res/img/b/I’m trying hard to randomly name these directories/ĉu ĉi tio sufiĉe hazardas?!/classy_fireplace.jpg"
      "http://localhost:4242/res/img/level-2/café.jpg"
      "http://localhost:4242/res/img/merry christmas!!! ^_^.jpg"
-     "http://localhost:4242/res/style.css"
-     "http://localhost:4242/res/welcoming you.jpg")
+     "http://localhost:4242/res/style.css")
    (sort (mirror-img::linked-urls
           (lquery:$ (lquery:initialize
                      (relative-pathname "t/testing-website/index.html"))))

t/testing-website/index.html

@@ -11,7 +11,7 @@
 			<h1>A sultry welcome to you</h1>
 
 			<figure>
-				<img src="http://localhost:4242/res/welcoming you.jpg">
+				<img src="/res/welcoming you.jpg">
 				<figcaption>Welcome~
 					<a href="https://twitter.com/Distrbeachboy/status/1758538124785852426">
 						🔗