Add sauron event for @-mention in twittering mode

If `twittering-username` is set, events will be added when new tweets
come with with `@<username>`. `sauron-prio-twittering-mention` can be
customized to change the priority of @-mention messages.

Resolves #43

README.org

@@ -13,7 +13,7 @@
    case of IRC (ERC), it will switch you to the buffer (channel) it originated
    from. It's a bit of a generalization of what /tracking mode/ does in ERC (the
    emacs IRC client), and that is in fact how it started.
- 
+
    There's an increasing number of hooks and tunables in sauron, which allows
    you to fine-tune the behavior. However, I strive for it to be useful with
    minimal configuration.
@@ -228,7 +228,7 @@
    - *identica* - for =identica-mode=, the social-network site
    - *twittering* - for =twittering-mode=, the emacs twitter client
    - *jabber* - for =jabber=, the IM protocol (XMPP)
-   - *elfeed* - for =elfeed=, an emacs Atom/RSS feed reader 
+   - *elfeed* - for =elfeed=, an emacs Atom/RSS feed reader
 
      By default, =sauron= tries to load all of them; this should work, even if
      you don't have some of these packages (they simply won't be activated).
@@ -356,6 +356,14 @@ DBUS_SESSION_BUS_ADDRESS="`cat ~/.sauron-dbus`" dbus-send ....
     =sauron-identica= shows the number of new dents found by =identica-mode= whenever
     there is at least one new dent.
 
+*** twittering
+
+    =sauron-twittering= shows the number of new tweets found by
+    =twittering-mode= whenever there is at least one new tweet.
+
+    If =twittering-username= is set, it will also show @-mentions when new
+    tweets arrive.
+
 *** jabber
 
     =sauron-jabber= shows events from =jabber.el=, this includes new messages, info

sauron-twittering.el

@@ -28,6 +28,9 @@
 (defvar sauron-prio-twittering-new-tweets 3
   "Twittering new tweets event priority.")
 
+(defvar sauron-prio-twittering-mention 4
+  "Twittering @-mention event priority.")
+
 (defvar sauron-twittering-running nil
   "when non-nil, sauron-twittering is running")
 
@@ -40,7 +43,9 @@
 	(error "sauron-twittering is already running. Call
           sauron-twittering-stop first."))
 
-      (add-hook 'twittering-new-tweets-hook 'sauron-twittering-new-tweets-func)
+      (add-hook 'twittering-new-tweets-hook #'sauron-twittering-new-tweets-func)
+      (add-hook 'twittering-new-tweets-hook
+                #'sauron-twittering-check-tweet-mention-func)
       (setq sauron-twittering-running t))
     (message "No twittering, so sauron-twittering could not
     start")))
@@ -50,21 +55,47 @@
   "Stops and cleans up sauron-twittering."
   (when sauron-twittering-running
     (remove-hook 'twittering-new-tweets-hook 'sauron-twittering-new-tweets-func)
+    (remove-hook 'twittering-new-tweets-hook
+                 #'sauron-twittering-check-tweet-mention-func)
     (setq sauron-twittering-running nil)))
 
 
+(defun sauron-twittering-check-tweet-mention-func ()
+  "Hook which takes newly incoming tweets and adds sauron events
+for any mentioning `twittering-username'. Events will be added
+using `sauron-prio-twittering-mention' priority."
+  (when (and twittering-username
+             (boundp 'twittering-new-tweets-statuses))
+    (dolist (tweet twittering-new-tweets-statuses)
+      (when (string-match-p
+             (format "@%s" twittering-username)
+             (alist-get 'text tweet))
+        (sr-twit-add-event
+         sauron-prio-twittering-mention
+         (format "%s: %s"
+                 (alist-get 'user-screen-name tweet)
+                 (alist-get 'text tweet))
+         (lexical-let
+             ((tweets-spec twittering-new-tweets-spec)
+              (tweets-data twittering-new-tweets-statuses)
+              (tweets-count twittering-new-tweets-count))
+           (lambda ()
+             (sr-twit-activate-event
+              tweets-data tweets-count tweets-spec))))))))
+
+
 (defun sauron-twittering-new-tweets-func ()
   "Hook which handles the arrival of new tweets. Main entry point and interface
 to twittering."
-  (sr-twit-add-event sauron-prio-twittering-new-tweets
-                     (format "%d new tweets"  twittering-new-tweets-count)
-    (lexical-let
-      ((tweets-spec twittering-new-tweets-spec)
-	(tweets-data twittering-new-tweets-statuses)
-	(tweets-count twittering-new-tweets-count))
-      (lambda ()
-	(sr-twit-activate-event tweets-data tweets-count tweets-spec)
-	))))
+  (sr-twit-add-event
+   sauron-prio-twittering-new-tweets
+   (format "%d new tweets"  twittering-new-tweets-count)
+   (lexical-let
+       ((tweets-spec twittering-new-tweets-spec)
+        (tweets-data twittering-new-tweets-statuses)
+        (tweets-count twittering-new-tweets-count))
+     (lambda ()
+       (sr-twit-activate-event tweets-data tweets-count tweets-spec)))))
 
 (defun sr-twit-add-event (priority message callback)
   (sauron-add-event 'twittering priority message callback))