(require 'xml)
-(defun atom-create (title link &optional self id author updated)
+(defun atom-create (title link &optional subtitle self id author updated)
"Create a new atom structure.
TITLE is the title for the feed, a short, text-only, human
LINK is the URL of a page responible for the content of this
feed.
+SUBTITLE is a subtitle for the feed; it can be a bit longer than
+TITLE, maybe a paragraph long.
+
SELF is the canonical URL to this feed.
ID is a unique identifier for this feed. If not given, it
(let ((atom-feed (list (list 'title nil title))))
(atom-modify-entry atom-feed 'link `(((href . ,link))))
(atom-modify-entry atom-feed 'author (atom-massage-author author))
+ (if subtitle (atom-modify-entry atom-feed 'subtitle subtitle))
(if self (atom-modify-entry atom-feed 'link
`(((href . ,self) (rel . "self")
(type . "application/atom+xml")))))
(nconc atom (list `(entry nil ,@entry))))
(defun atom-modify-entry (entry name val)
- "Set the NAME element of ENTRY to VAL. A true MULTIPLE means
-to add a new element instead of updating it when it already exists."
+ "Set the NAME element of ENTRY to VAL."
(let ((elem (if (stringp val)
(list name nil val)
(cons name val))))
(write-region (point-min) (point-max) filename)))
\f
+(defun atom-to-rss (atom)
+ "Translate an Atom feed into an RSS one, returning the translation.
+
+Some information may be lost or approximated."
+ (let ((rss (list (assoc 'title atom))))
+ (atom-to-rss-translator atom rss '((subtitle . description)
+ (updated . pubDate)
+ (link . link)))
+ (atom-to-rss-modify-time rss)
+ (atom-to-rss-modify-link rss)
+ (dolist (entry (xml-get-children atom 'entry))
+ (push (atom-to-rss-item entry) rss))
+ (reverse rss)))
+
+(defun atom-to-rss-item (entry)
+ "Translates an Atom entry into an RSS item."
+ (let ((item (list (assoc 'title entry))))
+ (atom-to-rss-translator
+ (xml-node-children entry) item
+ '((id . guid) (content . description) (updated . pubDate) (link . link)))
+ (atom-to-rss-modify-time item)
+ (atom-to-rss-modify-link item)
+ (let ((guid (assoc 'guid item))
+ (descr (assoc 'description item)))
+ (if guid
+ (setcar (cdr guid) (list (cons 'isPermaLink "false"))))
+ (if (and descr
+ (equal (xml-get-attribute descr 'type) "xhtml"))
+ (setcar (cddr descr) (xml-node-text descr))))
+ `(item nil ,@item)))
+
+(defun atom-to-rss-translator (source target translations)
+ (dolist (translation translations)
+ (let* ((from (car translation))
+ (to (cdr translation))
+ (data (copy-tree (cdr (assoc from source)))))
+ (when data
+ (atom-modify-entry target to data)))))
+
+(defun xml-node-text (node)
+ (with-temp-buffer
+ (xml-print (xml-node-children node))
+ (buffer-string)))
+
+(defun atom-to-rss-modify-link (entry)
+ (let* ((link (assoc 'link entry))
+ (link-addr (xml-get-attribute-or-nil link 'href)))
+ (message "%S" link)
+ (when link
+ (setcar (cdr link) nil)
+ (setcdr (cdr link) (cons link-addr nil)))))
+
+(defun atom-print-as-rss (atom)
+ (let ((rss (atom-to-rss atom)))
+ (insert "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n")
+ (insert "<rss version=\"2.0\">\n")
+ (insert " <channel>\n")
+ (xml-print rss " ")
+ (insert "\n </channel>\n")
+ (insert "</rss>")))
+
+(defun atom-to-rss-time (time)
+ "Translates a string from the format used by Atom into the
+format used by RSS."
+ ;; Same remark as in `atom-format-time'
+ (let ((system-time-locale "C"))
+ (format-time-string "%a, %d %b %Y %T %z" (atom-parse-time time))))
+
+(defun atom-to-rss-modify-time (entry)
+ "Modify ENTRY, changing the format of the `pubDate' in it."
+ (let ((pubDate (assoc 'pubDate entry)))
+ (setcar (cddr pubDate)
+ (atom-to-rss-time (car (xml-node-children pubDate))))))
+
+(defun atom-to-rss-write-file (atom filename)
+ "Saves ATOM as a RSS feed into FILENAME."
+ (with-temp-buffer
+ (atom-print-as-rss atom)
+ (write-region nil nil filename)))
+
+\f
+(defvar atom-time-format-string "%Y-%m-%dT%T%z"
+ "The format for string representation of dates.")
+
(defun atom-format-time (&optional time)
"Format a time according to RFC3339."
;; The time zone must be specified in numeric form, but with a colon between
;; the hour and minute parts.
(replace-regexp-in-string
- "\\(..\\)$"
- ":\\1"
- (format-time-string "%Y-%m-%dT%T%z" time)))
+ "\\(..\\)$" ":\\1"
+ (format-time-string atom-time-format-string time)))
+
+(defun atom-parse-time (&optional time)
+ "Parse a time as specified in RFC3339 into Emacs's native format."
+ (date-to-time (replace-regexp-in-string ":\\(..\\)$" "\\1" time)))
(defun atom-massage-html (content)
"Massage CONTENT so it can be used as an HTML fragment in an