;;; time.el --- display time and load in mode line of Emacs.

;; Copyright (C) 1985, 86, 87, 93, 94, 1996 Free Software Foundation, Inc.

;; Maintainer: FSF

;; This file is part of XEmacs.

;; XEmacs is free software; you can redistribute it and/or modify it
;; under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; XEmacs is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;; General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with XEmacs; see the file COPYING.  If not, write to the Free
;; Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
;; 02111-1307, USA.

;;; Synched up with: Not synched with FSF.

;;; Commentary:

;; Facilities to display current time/date and a new-mail indicator
;; in the Emacs mode line.  The single entry point is `display-time'.

;; See also reportmail.el.
;; This uses the XEmacs timeout-event mechanism, via a version
;; of Kyle Jones' itimer package.

;;; Code:

(require 'itimer)

(defvar display-time-mail-file nil
  "*File name of mail inbox file, for indicating existence of new mail.
Non-nil and not a string means don't check for mail.  nil means use
default, which is system-dependent, and is the same as used by Rmail.")

;;;###autoload
(defvar display-time-day-and-date nil "\
*Non-nil means \\[display-time] should display day and date as well as time.")

(defvar display-time-interval 60
  "*Seconds between updates of time in the mode line.")

(defvar display-time-24hr-format nil
  "*Non-nil indicates time should be displayed as hh:mm, 0 <= hh <= 23.
Nil means 1 <= hh <= 12, and an AM/PM suffix is used.")

(defvar display-time-echo-area nil
  "*If non-nil, display-time will use the echo area instead of the mode line.")

(defvar display-time-string nil)

(defvar display-time-hook nil
  "*List of functions to be called when the time is updated on the mode line.")

(defvar display-time-server-down-time nil
   "Time when mail file's file system was recorded to be down.
If that file system seems to be up, the value is nil.")

;;;###autoload
(defun display-time ()
  "Display current time, load level, and mail flag in mode line of each buffer.
Updates automatically every minute.
If `display-time-day-and-date' is non-nil, the current day and date
are displayed as well.
After each update, `display-time-hook' is run with `run-hooks'.
If `display-time-echo-area' is non-nil, the time is displayed in the
echo area instead of in the mode-line."
  (interactive)
  ;; if the "display-time" itimer already exists, nuke it first.
  (let ((old (get-itimer "display-time")))
    (if old (delete-itimer old)))
  ;; If we're not displaying the time in the echo area
  ;; and the global mode string does not have a non-nil value
  ;; then initialize the global mode string's value.
  (or display-time-echo-area
      global-mode-string
      (setq global-mode-string '("")))
  ;; If we're not displaying the time in the echo area
  ;; and our display variable is not part of the global-mode-string list
  ;; the we add our variable to the list.  This will make the time
  ;; appear on the modeline.
  (or display-time-echo-area
      (memq 'display-time-string global-mode-string)
      (setq global-mode-string
	    (append global-mode-string '(display-time-string))))
  ;; Display the time initially...
  (display-time-function)
  ;; ... and start an itimer to do it automatically thereafter.
  ;;
  ;; If we wanted to be really clever about this, we could have the itimer
  ;; not be automatically restarted, but have it re-add itself each time.
  ;; Then we could look at (current-time) and arrange for the itimer to
  ;; wake up exactly at the minute boundary.  But that's just a little
  ;; more work than it's worth...
  (start-itimer "display-time" 'display-time-function
		display-time-interval display-time-interval))

(defvar display-time-string-forms
  '((if display-time-day-and-date
        (format "%s %s %s " dayname monthname day)
      "")
    (format "%s:%s%s"
            (if display-time-24hr-format 24-hours 12-hours)
            minutes
            (if display-time-24hr-format "" am-pm))
    load
    (if mail " Mail" ""))
  "*A list of expressions governing display of the time in the mode line.
This expression is a list of expressions that can involve the keywords
`load', `day', `month', and `year', `12-hours', `24-hours', `minutes',
`seconds', all numbers in string form, and `monthname', `dayname', `am-pm',
and `time-zone' all alphabetic strings, and `mail' a true/nil value.

For example, the form

  '((substring year -2) \"/\" month \"/\" day
    \" \" 24-hours \":\" minutes \":\" seconds
    (if time-zone \" (\") time-zone (if time-zone \")\")
    (if mail \" Mail\" \"\"))

would give mode line times like `94/12/30 21:07:48 (UTC)'.")

(defun display-time-function ()
  (let* ((now (current-time))
	 (time (current-time-string now))
         (load (condition-case ()
                   (if (zerop (car (load-average))) ""
                     (let ((str (format " %03d" (car (load-average)))))
                       (concat (substring str 0 -2) "." (substring str -2))))
                 (error "")))
         (mail-spool-file (or display-time-mail-file
                              (getenv "MAIL")
                              (concat rmail-spool-directory
                                      (user-login-name))))
	 (mail (and (stringp mail-spool-file)
		    (or (null display-time-server-down-time)
			;; If have been down for 20 min, try again.
			(> (- (nth 1 (current-time))
			      display-time-server-down-time)
			   1200))
		    (let ((start-time (current-time)))
		      (prog1
			  (display-time-file-nonempty-p mail-spool-file)
			(if (> (- (nth 1 (current-time)) (nth 1 start-time))
			       20)
			    ;; Record that mail file is not accessible.
			    (setq display-time-server-down-time 
				  (nth 1 (current-time)))
			  ;; Record that mail file is accessible.
			  (setq display-time-server-down-time nil))))))
         (24-hours (substring time 11 13))
         (hour (string-to-int 24-hours))
         (12-hours (int-to-string (1+ (% (+ hour 11) 12))))
         (am-pm (if (>= hour 12) "pm" "am"))
         (minutes (substring time 14 16))
         (seconds (substring time 17 19))
         (time-zone (car (cdr (current-time-zone now))))
         (day (substring time 8 10))
         (year (substring time 20 24))
         (monthname (substring time 4 7))
         (month
          (cdr
           (assoc
            monthname
            '(("Jan" . "1") ("Feb" . "2") ("Mar" . "3") ("Apr" . "4")
              ("May" . "5") ("Jun" . "6") ("Jul" . "7") ("Aug" . "8")
              ("Sep" . "9") ("Oct" . "10") ("Nov" . "11") ("Dec" . "12")))))
         (dayname (substring time 0 3)))
    (setq display-time-string
          (mapconcat 'eval display-time-string-forms ""))
    ;; This is inside the let binding, but we are not going to document
    ;; what variables are available.
    (run-hooks 'display-time-hook))
  (if display-time-echo-area
      (or (> (minibuffer-depth) 0)
	  ;; don't stomp echo-area-buffer if reading from minibuffer now.
	  (save-excursion
	    (save-window-excursion
	      (select-window (minibuffer-window))
	      (erase-buffer)
	      (indent-to (- (screen-width) (length display-time-string) 1))
	      (insert display-time-string)
	      (message (buffer-string)))))
    (force-mode-line-update)
    ;; Do redisplay right now, if no input pending.
    (sit-for 0)))

(defun display-time-file-nonempty-p (file)
  (and (file-exists-p file)
       (< 0 (nth 7 (file-attributes (file-chase-links file))))))

(provide 'time)

;;; time.el ends here