;;; Commentary:

;; Kills buffers that I never use, and that annoy me when completion
;; offers their names.

;; Note that this may be overkill (ha); given that I use "ido", it
;; might suffice to simply add something to ido-make-buffer-list-hook,
;; that puts these buffers at the end of the list.

;; This code all depends on a buffer-local variable named
;; buffer-creation-time.  That variable doesn't (yet) exist in
;; anyone's Emacs but mine, since I hacked it in myself.
(if (fboundp 'buffer-creation-time)
  (progn
    (defun kill-them-buffers ()
      (mapc
       (lambda (p)
         (flet ((time->string
                 (time)
                 (format-seconds "%Y, %D, %H, %M, %z%S" (float-time time))))
           (let ((victim (get-buffer (car p))))
             (when victim
               ;; if the buffer is not old enough, spare its life.
               (let ((allotted-lifespan (cdr p))
                     (age (time-subtract
                           (current-time)
                           (with-current-buffer  victim

                             ;; Ideally we'd consider the
                             ;; last-modification time of the buffer
                             ;; too, and kill it only if _both_ those
                             ;; times are old.  But we don't keep
                             ;; track of that time (yet :-).
                             (buffer-creation-time)))))

                 (if (time-less-p allotted-lifespan age)
                     (progn
                       ;; if it's displayed in some window, nix the window.
                       (let ((window-victim (get-buffer-window victim t)))
                         (while window-victim
                           (delete-window window-victim)
                           (setq window-victim (get-buffer-window victim t))))
                       (message "Killing buffer %s -- it's %s old (which is more than %s)!!"
                                victim
                                (time->string age)
                                (time->string allotted-lifespan))
                       (kill-buffer victim))

                   (message "Spared buffer %s -- it's only %s old"
                            victim
                            (time->string age))))))))

       ;; These are buffers whose names make them likely to get in my
       ;; way when I'm looking for some other, similarly-named,
       ;; buffer.  Ido probably makes this problem worse.
       `(
         ;; Times are pairs of (HIGH LOW) seconds; see 'current-time'
         ("*Completions*" . (0 3))
         ("*Shell Command Output*" . (0 120))
         ("*vc-diff*" . (0 60))
         )))

    (setq *reaper-timer*
          (run-with-idle-timer 5 t 'kill-them-buffers))

    (when nil
      (cancel-timer *reaper-timer*)))
  (message "There's no function named buffer-creation-time, so I cannot start the reaper."))