;;; time-date.el --- Date and time handling functions

;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
;;   2007, 2008, 2009, 2010  Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;;	Masanobu Umeda <umerin@mse.kyutech.ac.jp>
;; Keywords: mail news util

;; This file is part of GNU Emacs.

;; GNU Emacs 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 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs 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 GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Time values come in three formats.  The oldest format is a cons
;; cell of the form (HIGH . LOW).  This format is obsolete, but still
;; supported.  The two other formats are the lists (HIGH LOW) and
;; (HIGH LOW MICRO).  The first two formats specify HIGH * 2^16 + LOW
;; seconds; the third format specifies HIGH * 2^16 + LOW + MICRO /
;; 1000000 seconds.  We should have 0 <= MICRO < 1000000 and 0 <= LOW
;; < 2^16.  If the time value represents a point in time, then HIGH is
;; nonnegative.  If the time value is a time difference, then HIGH can
;; be negative as well.  The macro `with-decoded-time-value' and the
;; function `encode-time-value' make it easier to deal with these
;; three formats.  See `time-subtract' for an example of how to use
;; them.

;;; Code:

(defmacro with-decoded-time-value (varlist &rest body)
  "Decode a time value and bind it according to VARLIST, then eval BODY.

The value of the last form in BODY is returned.

Each element of the list VARLIST is a list of the form
\(HIGH-SYMBOL LOW-SYMBOL MICRO-SYMBOL [TYPE-SYMBOL] TIME-VALUE).
The time value TIME-VALUE is decoded and the result it bound to
the symbols HIGH-SYMBOL, LOW-SYMBOL and MICRO-SYMBOL.

The optional TYPE-SYMBOL is bound to the type of the time value.
Type 0 is the cons cell (HIGH . LOW), type 1 is the list (HIGH
LOW), and type 2 is the list (HIGH LOW MICRO)."
  (declare (indent 1)
	   (debug ((&rest (symbolp symbolp symbolp &or [symbolp form] form))
		   body)))
  (if varlist
      (let* ((elt (pop varlist))
	     (high (pop elt))
	     (low (pop elt))
	     (micro (pop elt))
	     (type (unless (eq (length elt) 1)
		     (pop elt)))
	     (time-value (car elt))
	     (gensym (make-symbol "time")))
	`(let* ,(append `((,gensym ,time-value)
			  (,high (pop ,gensym))
			  ,low ,micro)
			(when type `(,type)))
	   (if (consp ,gensym)
	       (progn
		 (setq ,low (pop ,gensym))
		 (if ,gensym
		     ,(append `(setq ,micro (car ,gensym))
			      (when type `(,type 2)))
		   ,(append `(setq ,micro 0)
			    (when type `(,type 1)))))
	     ,(append `(setq ,low ,gensym ,micro 0)
		      (when type `(,type 0))))
	   (with-decoded-time-value ,varlist ,@body)))
    `(progn ,@body)))

(defun encode-time-value (high low micro type)
  "Encode HIGH, LOW, and MICRO into a time value of type TYPE.
Type 0 is the cons cell (HIGH . LOW), type 1 is the list (HIGH LOW),
and type 2 is the list (HIGH LOW MICRO)."
  (cond
   ((eq type 0) (cons high low))
   ((eq type 1) (list high low))
   ((eq type 2) (list high low micro))))

(autoload 'parse-time-string "parse-time")
(autoload 'timezone-make-date-arpa-standard "timezone")

;;;###autoload
;; `parse-time-string' isn't sufficiently general or robust.  It fails
;; to grok some of the formats that timezone does (e.g. dodgy
;; post-2000 stuff from some Elms) and either fails or returns bogus
;; values.  timezone-make-date-arpa-standard should help.
(defun date-to-time (date)
  "Parse a string DATE that represents a date-time and return a time value.
If DATE lacks timezone information, GMT is assumed."
  (condition-case ()
      (apply 'encode-time (parse-time-string date))
    (error (condition-case ()
	       (apply 'encode-time
		      (parse-time-string
		       (timezone-make-date-arpa-standard date)))
	     (error (error "Invalid date: %s" date))))))

;; Bit of a mess.  Emacs has float-time since at least 21.1.
;; This file is synced to Gnus, and XEmacs packages may have been written
;; using time-to-seconds from the Gnus library.
;;;###autoload(if (or (featurep 'emacs)
;;;###autoload        (and (fboundp 'float-time)
;;;###autoload             (subrp (symbol-function 'float-time))))
;;;###autoload    (progn
;;;###autoload      (defalias 'time-to-seconds 'float-time)
;;;###autoload      (make-obsolete 'time-to-seconds 'float-time "21.1"))
;;;###autoload  (autoload 'time-to-seconds "time-date"))

(eval-when-compile
  (or (featurep 'emacs)
      (and (fboundp 'float-time)
           (subrp (symbol-function 'float-time)))
      (defun time-to-seconds (time)
        "Convert time value TIME to a floating point number."
        (with-decoded-time-value ((high low micro time))
          (+ (* 1.0 high 65536)
             low
             (/ micro 1000000.0))))))

;;;###autoload
(defun seconds-to-time (seconds)
  "Convert SECONDS (a floating point number) to a time value."
  (list (floor seconds 65536)
	(floor (mod seconds 65536))
	(floor (* (- seconds (ffloor seconds)) 1000000))))

;;;###autoload
(defun time-less-p (t1 t2)
  "Return non-nil if time value T1 is earlier than time value T2."
  (with-decoded-time-value ((high1 low1 micro1 t1)
			    (high2 low2 micro2 t2))
    (or (< high1 high2)
	(and (= high1 high2)
	     (or (< low1 low2)
		 (and (= low1 low2)
		      (< micro1 micro2)))))))

;;;###autoload
(defun days-to-time (days)
  "Convert DAYS into a time value."
  (let* ((seconds (* 1.0 days 60 60 24))
	 (high (condition-case nil (floor (/ seconds 65536))
		 (range-error most-positive-fixnum))))
    (list high (condition-case nil (floor (- seconds (* 1.0 high 65536)))
		 (range-error 65535)))))

;;;###autoload
(defun time-since (time)
  "Return the time elapsed since TIME.
TIME should be either a time value or a date-time string."
  (when (stringp time)
    ;; Convert date strings to internal time.
    (setq time (date-to-time time)))
  (time-subtract (current-time) time))

;;;###autoload
(defalias 'subtract-time 'time-subtract)

;;;###autoload
(defun time-subtract (t1 t2)
  "Subtract two time values, T1 minus T2.
Return the difference in the format of a time value."
  (with-decoded-time-value ((high low micro type t1)
			    (high2 low2 micro2 type2 t2))
    (setq high (- high high2)
	  low (- low low2)
	  micro (- micro micro2)
	  type (max type type2))
    (when (< micro 0)
      (setq low (1- low)
	    micro (+ micro 1000000)))
    (when (< low 0)
      (setq high (1- high)
	    low (+ low 65536)))
    (encode-time-value high low micro type)))

;;;###autoload
(defun time-add (t1 t2)
  "Add two time values T1 and T2.  One should represent a time difference."
  (with-decoded-time-value ((high low micro type t1)
			    (high2 low2 micro2 type2 t2))
    (setq high (+ high high2)
	  low (+ low low2)
	  micro (+ micro micro2)
	  type (max type type2))
    (when (>= micro 1000000)
      (setq low (1+ low)
	    micro (- micro 1000000)))
    (when (>= low 65536)
      (setq high (1+ high)
	    low (- low 65536)))
    (encode-time-value high low micro type)))

;;;###autoload
(defun date-to-day (date)
  "Return the number of days between year 1 and DATE.
DATE should be a date-time string."
  (time-to-days (date-to-time date)))

;;;###autoload
(defun days-between (date1 date2)
  "Return the number of days between DATE1 and DATE2.
DATE1 and DATE2 should be date-time strings."
  (- (date-to-day date1) (date-to-day date2)))

;;;###autoload
(defun date-leap-year-p (year)
  "Return t if YEAR is a leap year."
  (or (and (zerop (% year 4))
	   (not (zerop (% year 100))))
      (zerop (% year 400))))

;;;###autoload
(defun time-to-day-in-year (time)
  "Return the day number within the year corresponding to TIME."
  (let* ((tim (decode-time time))
	 (month (nth 4 tim))
	 (day (nth 3 tim))
	 (year (nth 5 tim))
	 (day-of-year (+ day (* 31 (1- month)))))
    (when (> month 2)
      (setq day-of-year (- day-of-year (/ (+ 23 (* 4 month)) 10)))
      (when (date-leap-year-p year)
	(setq day-of-year (1+ day-of-year))))
    day-of-year))

;;;###autoload
(defun time-to-days (time)
  "The number of days between the Gregorian date 0001-12-31bce and TIME.
TIME should be a time value.
The Gregorian date Sunday, December 31, 1bce is imaginary."
  (let* ((tim (decode-time time))
	 (month (nth 4 tim))
	 (day (nth 3 tim))
	 (year (nth 5 tim)))
    (+ (time-to-day-in-year time)	; 	Days this year
       (* 365 (1- year))		;	+ Days in prior years
       (/ (1- year) 4)			;	+ Julian leap years
       (- (/ (1- year) 100))		;	- century years
       (/ (1- year) 400))))		;	+ Gregorian leap years

(defun time-to-number-of-days (time)
  "Return the number of days represented by TIME.
Returns a floating point number."
  (/ (funcall (eval-when-compile
                (if (or (featurep 'emacs)
                        (and (fboundp 'float-time)
                             (subrp (symbol-function 'float-time))))
                    'float-time
                  'time-to-seconds)) time) (* 60 60 24)))

;;;###autoload
(defun safe-date-to-time (date)
  "Parse a string DATE that represents a date-time and return a time value.
If DATE is malformed, return a time value of zeros."
  (condition-case ()
      (date-to-time date)
    (error '(0 0))))


;;;###autoload
(defun format-seconds (string seconds)
  "Use format control STRING to format the number SECONDS.
The valid format specifiers are:
%y is the number of (365-day) years.
%d is the number of days.
%h is the number of hours.
%m is the number of minutes.
%s is the number of seconds.
%z is a non-printing control flag (see below).
%% is a literal \"%\".

Upper-case specifiers are followed by the unit-name (e.g. \"years\").
Lower-case specifiers return only the unit.

\"%\" may be followed by a number specifying a width, with an
optional leading \".\" for zero-padding.  For example, \"%.3Y\" will
return something of the form \"001 year\".

The \"%z\" specifier does not print anything.  When it is used, specifiers
must be given in order of decreasing size.  To the left of \"%z\", nothing
is output until the first non-zero unit is encountered.

This function does not work for SECONDS greater than `most-positive-fixnum'."
  (let ((start 0)
        (units '(("y" "year"   31536000)
                 ("d" "day"       86400)
                 ("h" "hour"       3600)
                 ("m" "minute"       60)
                 ("s" "second"        1)
                 ("z")))
        (case-fold-search t)
        spec match usedunits zeroflag larger prev name unit num zeropos)
    (while (string-match "%\\.?[0-9]*\\(.\\)" string start)
      (setq start (match-end 0)
            spec (match-string 1 string))
      (unless (string-equal spec "%")
	;; `assoc-string' is not available in XEmacs.  So when compiling
	;; Gnus (`time-date.el' is part of Gnus) with XEmacs, we get
	;; a warning here.  But `format-seconds' is not used anywhere in
	;; Gnus so it's not a real problem. --rsteib
        (or (setq match (assoc-string spec units t))
            (error "Bad format specifier: `%s'" spec))
        (if (assoc-string spec usedunits t)
            (error "Multiple instances of specifier: `%s'" spec))
        (if (string-equal (car match) "z")
            (setq zeroflag t)
          (unless larger
            (setq unit (nth 2 match)
                  larger (and prev (> unit prev))
                  prev unit)))
        (push match usedunits)))
    (and zeroflag larger
         (error "Units are not in decreasing order of size"))
    (dolist (u units)
      (setq spec (car u)
            name (cadr u)
            unit (nth 2 u))
      (when (string-match (format "%%\\(\\.?[0-9]+\\)?\\(%s\\)" spec) string)
        (if (string-equal spec "z")     ; must be last in units
            (setq string
                  (replace-regexp-in-string
                   "%z" ""
                   (substring string (min (or zeropos (match-end 0))
                                          (match-beginning 0)))))
          ;; Cf article-make-date-line in gnus-art.
          (setq num (floor seconds unit)
                seconds (- seconds (* num unit)))
          ;; Start position of the first non-zero unit.
          (or zeropos
              (setq zeropos (unless (zerop num) (match-beginning 0))))
          (setq string
                (replace-match
                 (format (concat "%" (match-string 1 string) "d%s") num
                         (if (string-equal (match-string 2 string) spec)
                             ""       ; lower-case, no unit-name
                           (format " %s%s" name
                                   (if (= num 1) "" "s"))))
                 t t string))))))
  (replace-regexp-in-string "%%" "%" string))


(provide 'time-date)

;;; time-date.el ends here