;;; Commentary:
-;; This is a library for creating an Atom file from a Lisp program.
+;; This is a library for creating an Atom feed from a Lisp program.
+;; The normal usage is to create a feed with `atom-create', giving it
+;; a title and a Web address. Once the feed has been created, entries
+;; may be added to the feed, by specifying (at the minimum) a title, a
+;; permanent link and the content of the entry. Text-only, HTML and
+;; XHTML entries are supported.
+
+;; A feed is really a Lisp structure as used by the `xml.el' package,
+;; without the parent `feed' element.
;; A typical usage would look like this:
;; (let ((my-atom-feed (atom-create "My feed" "http://example.org")))
-;; (atom-add-text-entry my-atom-feed
-;; "Hello world"
-;; "http://example.org/hello"
-;; "Hello the world!")
-;; (atom-add-xhtml-entry my-atom-feed
-;; "An XHTML example"
-;; "http://example.org/html-example"
-;; "<p>One can also use <acronym>XHTML</acronym> in the
-;; entries.</p>")
+;; ; A simple, text-only entry
+;; (atom-add-text-entry
+;; my-atom-feed
+;; "Hello world"
+;; "http://example.org/hello"
+;; "Hello the world!")
+;;
+;; ; A text-only entry, with all the optional pieces of data
+;; (atom-add-text-entry
+;; my-atom-feed
+;; "Bonjour"
+;; "http://example.org/bonjour"
+;; "Bonjour à tout le monde !"
+;; ;; optional: the last modification time
+;; (date-to-time "2011-01-30 23:40:12")
+;; ;; optional: an identifier for this entry; a common way to generate it is
+;; ;; to use the domain name and the creation date of the entry.
+;; (atom-generate-id "http://example.org"
+;; (date-to-time "2011-01-30 10:01:05"))
+;; ;; optional: a summary for this entry
+;; "Bonjour, monde.")
+;;
+;; (atom-add-xhtml-entry
+;; my-atom-feed
+;; "An XHTML example"
+;; "http://example.org/html-example"
+;; "<p>One can also use <acronym>XHTML</acronym> in the entries.</p>")
;; (atom-print my-atom-feed))
+
;;; Code:
+(require 'xml)
+
(defun atom-create (title link &optional author updated id)
"Create a new atom structure.
ID is a unique identifier for this feed. If not given, it
defaults to LINK."
-
`((title nil ,title)
(link ((href . ,link)))
,(atom-massage-author author)
(nconc entry (list elem)))))
(defun atom-add-entry (atom title link content
- &optional summary updated id)
+ &optional updated id summary)
"Add an entry to the atom flux ATOM. Return the newly added
entry.
UPDATED defaults to `(current-time)' if omitted, which is
probably not a very good default.
-ID defaults to LINK, which is not optimal; TODO give a way to
-easily generate IDs. For a given entry, it must not change
-between successive generations of the atom feed."
+ID defaults to LINK, which is not optimal; see `atom-generate-id'
+for a way to create good identifiers. For a given entry, it must
+not change between successive generations of the atom feed, even
+when the content of the entry ."
(let ((entry (list (list 'title nil title))))
(atom-modify-entry entry 'link (list (list (cons 'href link))))
(atom-modify-entry entry 'id (or id link))
`atom-add-entry' for details.")
(defun atom-add-html-entry (atom title link content
- &optional summary updated id)
+ &optional updated id summary)
"Add an entry to ATOM, with some HTML content. CONTENT should
be a string enconding a valid HTML fragment. See `atom-add-entry'
for additional details."
updated id))
(defun atom-add-xhtml-entry (atom title link content
- &optional summary updated id)
+ &optional updated id summary)
"Add an entry to ATOM, with some XHTML content. CONTENT may be
given either as a string, or as an XML tree, of a valid XHTML
fragment. See `atom-add-entry' for additional details."
(email nil ,(cadr author))))
(t `(author nil ,author))))
+(require 'url-parse)
+
+(defun atom-generate-id (link creation-date)
+ "Generate a string suitable for use as an atom:id element. This
+implements Mark Pilgrom's tag: URI method, using the
+CREATION-DATE of the entry, and the domain part of LINK"
+ (format "tag:%s,%s:/%s"
+ (url-host (url-generic-parse-url link))
+ (format-time-string "%Y-%m-%d" creation-date)
+ (format-time-string "%Y%m%d%H%M%S" creation-date)))
+
(provide 'atom)
;;; atom.el ends here