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;;; cal-bahai.el --- calendar functions for the Bahá'í calendar. -*- coding: utf-8 -*-
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;; Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007
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;;   Free Software Foundation, Inc.
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;; Author: John Wiegley <johnw@gnu.org>
;; Keywords: calendar
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;; Human-Keywords: Bahá'í calendar, Bahá'í, Baha'i, Bahai, calendar, diary
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;; 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
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;; the Free Software Foundation; either version 3, or (at your option)
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;; 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; see the file COPYING.  If not, write to the
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;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.
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;;; Commentary:

;; This collection of functions implements the features of calendar.el
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;; and diary.el that deal with the Bahá'í calendar.
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;; The Bahá'í (http://www.bahai.org) calendar system is based on a
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;; solar cycle of 19 months with 19 days each.  The four remaining
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;; "intercalary" days are called the Ayyám-i-Há (days of Há), and are
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;; placed between the 18th and 19th months.  They are meant as a time
;; of festivals preceding the 19th month, which is the month of
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;; fasting.  In Gregorian leap years, there are 5 of these days (Há
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;; has the numerical value of 5 in the arabic abjad, or
;; letter-to-number, reckoning).

;; Each month is named after an attribute of God, as are the 19 days
;; -- which have the same names as the months.  There is also a name
;; for each year in every 19 year cycle.  These cycles are called
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;; Váhids.  A cycle of 19 Váhids (361 years) is called a Kullu-Shay,
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;; which means "all things".

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;; The calendar was named the "Badí` calendar" by its author, the Báb.
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;; It uses a week of seven days, corresponding to the Gregorian week,
;; each of which has its own name, again patterned after the
;; attributes of God.

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;; Note: The days of Ayyám-i-Há are encoded as zero and negative
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;; offsets from the first day of the final month.  So, (19 -3 157) is
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;; the first day of Ayyám-i-Há, in the year 157 BE.
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;;; Code:

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(defvar date)
(defvar displayed-month)
(defvar displayed-year)
(defvar number)
(defvar original-date)

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(require 'cal-julian)

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(defconst calendar-bahai-month-name-array
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  ["Bahá" "Jalál" "Jamál" "`Azamat" "Núr" "Rahmat" "Kalimát" "Kamál"
   "Asmá" "`Izzat" "Mashiyyat" "`Ilm" "Qudrat" "Qawl" "Masá'il"
   "Sharaf" "Sultán" "Mulk" "`Alá"])
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(defconst calendar-bahai-epoch (calendar-absolute-from-gregorian '(3 21 1844))
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  "Absolute date of start of Bahá'í calendar = March 19, 622 A.D. (Julian).")
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(defun calendar-bahai-leap-year-p (year)
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  "True if YEAR is a leap year on the Bahá'í calendar."
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  (calendar-leap-year-p (+ year 1844)))

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(defconst calendar-bahai-leap-base
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  (+ (/ 1844 4) (- (/ 1844 100)) (/ 1844 400)))

(defun calendar-absolute-from-bahai (date)
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  "Compute absolute date from Bahá'í date DATE.
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The absolute date is the number of days elapsed since the (imaginary)
Gregorian date Sunday, December 31, 1 BC."
  (let* ((month (extract-calendar-month date))
	 (day (extract-calendar-day date))
	 (year (extract-calendar-year date))
	 (prior-years (+ (1- year) 1844))
	 (leap-days (- (+ (/ prior-years 4) ; Leap days in prior years.
			  (- (/ prior-years 100))
			  (/ prior-years 400))
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		       calendar-bahai-leap-base)))
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    (+ (1- calendar-bahai-epoch)	; Days before epoch
       (* 365 (1- year))		; Days in prior years.
       leap-days
       (calendar-sum m 1 (< m month) 19)
       (if (= month 19) 4 0)
       day)))				; Days so far this month.

(defun calendar-bahai-from-absolute (date)
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  "Bahá'í year corresponding to the absolute DATE."
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  (if (< date calendar-bahai-epoch)
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      (list 0 0 0) ;; pre-Bahá'í date
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    (let* ((greg (calendar-gregorian-from-absolute date))
	   (year (+ (- (extract-calendar-year greg) 1844)
		    (if (or (> (extract-calendar-month greg) 3)
			    (and (= (extract-calendar-month greg) 3)
				 (>= (extract-calendar-day greg) 21)))
			1 0)))
           (month ;; Search forward from Baha.
            (1+ (calendar-sum m 1
			      (> date
				 (calendar-absolute-from-bahai
				  (list m 19 year)))
			      1)))
           (day	;; Calculate the day by subtraction.
            (- date
               (1- (calendar-absolute-from-bahai (list month 1 year))))))
      (list month day year))))

(defun calendar-bahai-date-string (&optional date)
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  "String of Bahá'í date of Gregorian DATE.
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Defaults to today's date if DATE is not given."
  (let* ((bahai-date (calendar-bahai-from-absolute
                       (calendar-absolute-from-gregorian
                        (or date (calendar-current-date)))))
         (y (extract-calendar-year bahai-date))
         (m (extract-calendar-month bahai-date))
         (d (extract-calendar-day bahai-date)))
    (let ((monthname
	   (if (and (= m 19)
		    (<= d 0))
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	       "Ayyám-i-Há"
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	     (aref calendar-bahai-month-name-array (1- m))))
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	  (day (int-to-string
		(if (<= d 0)
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		    (if (calendar-bahai-leap-year-p y)
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			(+ d 5)
		      (+ d 4))
		  d)))
	  (dayname nil)
	  (month (int-to-string m))
	  (year (int-to-string y)))
      (mapconcat 'eval calendar-date-display-form ""))))

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(defun calendar-bahai-print-date ()
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  "Show the Bahá'í calendar equivalent of the selected date."
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  (interactive)
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  (message "Bahá'í date: %s"
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           (calendar-bahai-date-string (calendar-cursor-to-date t))))

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(defun calendar-bahai-goto-date (date &optional noecho)
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  "Move cursor to Bahá'í date DATE.
Echo Bahá'í date unless NOECHO is t."
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  (interactive (calendar-bahai-prompt-for-date))
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  (calendar-goto-date (calendar-gregorian-from-absolute
                       (calendar-absolute-from-bahai date)))
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  (or noecho (calendar-bahai-print-date)))
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(defun calendar-bahai-prompt-for-date ()
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  "Ask for a Bahá'í date."
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  (let* ((today (calendar-current-date))
         (year (calendar-read
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                "Bahá'í calendar year (not 0): "
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                '(lambda (x) (/= x 0))
                (int-to-string
                 (extract-calendar-year
                  (calendar-bahai-from-absolute
                   (calendar-absolute-from-gregorian today))))))
         (completion-ignore-case t)
         (month (cdr (assoc
                       (completing-read
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                        "Bahá'í calendar month name: "
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                        (mapcar 'list
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                                (append calendar-bahai-month-name-array nil))
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                        nil t)
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                      (calendar-make-alist calendar-bahai-month-name-array
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                                           1))))
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         (day (calendar-read "Bahá'í calendar day (1-19): "
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			     '(lambda (x) (and (< 0 x) (<= x 19))))))
    (list (list month day year))))

(defun diary-bahai-date ()
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  "Bahá'í calendar equivalent of date diary entry."
  (format "Bahá'í date: %s" (calendar-bahai-date-string date)))
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(defun holiday-bahai (month day string)
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  "Holiday on MONTH, DAY (Bahá'í) called STRING.
If MONTH, DAY (Bahá'í) is visible, the value returned is corresponding
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Gregorian date in the form of the list (((month day year) STRING)).  Returns
nil if it is not visible in the current calendar window."
  (let* ((bahai-date (calendar-bahai-from-absolute
		      (calendar-absolute-from-gregorian
		       (list displayed-month 15 displayed-year))))
         (m (extract-calendar-month bahai-date))
         (y (extract-calendar-year bahai-date))
	 (date))
    (if (< m 1)
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        nil ;;   Bahá'í calendar doesn't apply.
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      (increment-calendar-month m y (- 10 month))
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      (if (> m 7) ;;  Bahá'í date might be visible
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          (let ((date (calendar-gregorian-from-absolute
                       (calendar-absolute-from-bahai (list month day y)))))
            (if (calendar-date-is-visible-p date)
                (list (list date string))))))))

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;; d-b-l-e should be called from diary code.
(declare-function add-to-diary-list "diary-lib"
                  (date string specifier &optional marker globcolor literal))

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(defun diary-bahai-list-entries ()
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  "Add any Bahá'í date entries from the diary file to `diary-entries-list'.
Bahá'í date diary entries must be prefaced by an
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`bahai-diary-entry-symbol' (normally a `B').  The same diary date
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forms govern the style of the Bahá'í calendar entries, except that the
Bahá'í month names must be given numerically.  The Bahá'í months are
numbered from 1 to 19 with Bahá being 1 and 19 being `Alá.  If a
Bahá'í date diary entry begins with a `diary-nonmarking-symbol', the
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entry will appear in the diary listing, but will not be marked in the
calendar.  This function is provided for use with the
`nongregorian-diary-listing-hook'."
  (if (< 0 number)
      (let ((buffer-read-only nil)
            (diary-modified (buffer-modified-p))
            (gdate original-date)
            (mark (regexp-quote diary-nonmarking-symbol)))
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        (dotimes (idummy number)
          (let* ((d diary-date-forms)
                 (bdate (calendar-bahai-from-absolute
                         (calendar-absolute-from-gregorian gdate)))
                 (month (extract-calendar-month bdate))
                 (day (extract-calendar-day bdate))
                 (year (extract-calendar-year bdate)))
            (while d
              (let*
                  ((date-form (if (equal (car (car d)) 'backup)
                                  (cdr (car d))
                                (car d)))
                   (backup (equal (car (car d)) 'backup))
                   (dayname
                    (concat
                     (calendar-day-name gdate) "\\|"
                     (substring (calendar-day-name gdate) 0 3) ".?"))
                   (calendar-month-name-array
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                    calendar-bahai-month-name-array)
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                   (monthname
                    (concat
                     "\\*\\|"
                     (calendar-month-name month)))
                   (month (concat "\\*\\|0*" (int-to-string month)))
                   (day (concat "\\*\\|0*" (int-to-string day)))
                   (year
                    (concat
                     "\\*\\|0*" (int-to-string year)
                     (if abbreviated-calendar-year
                         (concat "\\|" (int-to-string (% year 100)))
                       "")))
                   (regexp
                    (concat
                     "\\(\\`\\|\^M\\|\n\\)" mark "?"
                     (regexp-quote bahai-diary-entry-symbol)
                     "\\("
                     (mapconcat 'eval date-form "\\)\\(")
                     "\\)"))
                   (case-fold-search t))
                (goto-char (point-min))
                (while (re-search-forward regexp nil t)
                  (if backup (re-search-backward "\\<" nil t))
                  (if (and (or (char-equal (preceding-char) ?\^M)
                               (char-equal (preceding-char) ?\n))
                           (not (looking-at " \\|\^I")))
                      ;;  Diary entry that consists only of date.
                      (backward-char 1)
                    ;;  Found a nonempty diary entry--make it visible and
                    ;;  add it to the list.
                    (let ((entry-start (point))
                          (date-start))
                      (re-search-backward "\^M\\|\n\\|\\`")
                      (setq date-start (point))
                      (re-search-forward "\^M\\|\n" nil t 2)
                      (while (looking-at " \\|\^I")
                        (re-search-forward "\^M\\|\n" nil t))
                      (backward-char 1)
                      (subst-char-in-region date-start (point) ?\^M ?\n t)
                      (add-to-diary-list
                       gdate
                       (buffer-substring-no-properties entry-start (point))
                       (buffer-substring-no-properties
                        (1+ date-start) (1- entry-start)))))))
              (setq d (cdr d))))
          (setq gdate
                (calendar-gregorian-from-absolute
                 (1+ (calendar-absolute-from-gregorian gdate)))))
        (set-buffer-modified-p diary-modified))
    (goto-char (point-min))))
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(declare-function diary-name-pattern "diary-lib"
                  (string-array &optional abbrev-array paren))

(declare-function mark-calendar-days-named "diary-lib"
                  (dayname &optional color))

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(defun diary-bahai-mark-entries ()
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  "Mark days in the calendar window that have Bahá'í date diary entries.
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Each entry in diary-file (or included files) visible in the calendar
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window is marked.  Bahá'í date entries are prefaced by a
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bahai-diary-entry-symbol \(normally a B`I').  The same
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diary-date-forms govern the style of the Bahá'í calendar entries,
except that the Bahá'í month names must be spelled in full.  The
Bahá'í months are numbered from 1 to 12 with Bahá being 1 and 12 being
`Alá.  Bahá'í date diary entries that begin with a
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diary-nonmarking-symbol will not be marked in the calendar.  This
function is provided for use as part of the
nongregorian-diary-marking-hook."
  (let ((d diary-date-forms))
    (while d
      (let*
          ((date-form (if (equal (car (car d)) 'backup)
                          (cdr (car d))
                        (car d)));; ignore 'backup directive
           (dayname (diary-name-pattern calendar-day-name-array))
           (monthname
            (concat
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             (diary-name-pattern calendar-bahai-month-name-array t)
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             "\\|\\*"))
           (month "[0-9]+\\|\\*")
           (day "[0-9]+\\|\\*")
           (year "[0-9]+\\|\\*")
           (l (length date-form))
           (d-name-pos (- l (length (memq 'dayname date-form))))
           (d-name-pos (if (/= l d-name-pos) (+ 2 d-name-pos)))
           (m-name-pos (- l (length (memq 'monthname date-form))))
           (m-name-pos (if (/= l m-name-pos) (+ 2 m-name-pos)))
           (d-pos (- l (length (memq 'day date-form))))
           (d-pos (if (/= l d-pos) (+ 2 d-pos)))
           (m-pos (- l (length (memq 'month date-form))))
           (m-pos (if (/= l m-pos) (+ 2 m-pos)))
           (y-pos (- l (length (memq 'year date-form))))
           (y-pos (if (/= l y-pos) (+ 2 y-pos)))
           (regexp
            (concat
             "\\(\\`\\|\^M\\|\n\\)"
             (regexp-quote bahai-diary-entry-symbol)
             "\\("
             (mapconcat 'eval date-form "\\)\\(")
             "\\)"))
           (case-fold-search t))
        (goto-char (point-min))
        (while (re-search-forward regexp nil t)
          (let* ((dd-name
                  (if d-name-pos
                      (buffer-substring
                       (match-beginning d-name-pos)
                       (match-end d-name-pos))))
                 (mm-name
                  (if m-name-pos
                      (buffer-substring
                       (match-beginning m-name-pos)
                       (match-end m-name-pos))))
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                 (mm (string-to-number
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                      (if m-pos
                          (buffer-substring
                           (match-beginning m-pos)
                           (match-end m-pos))
                        "")))
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                 (dd (string-to-number
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                      (if d-pos
                          (buffer-substring
                           (match-beginning d-pos)
                           (match-end d-pos))
                        "")))
                 (y-str (if y-pos
                            (buffer-substring
                             (match-beginning y-pos)
                             (match-end y-pos))))
                 (yy (if (not y-str)
                         0
                       (if (and (= (length y-str) 2)
                                abbreviated-calendar-year)
                           (let* ((current-y
                                   (extract-calendar-year
                                    (calendar-bahai-from-absolute
                                     (calendar-absolute-from-gregorian
                                      (calendar-current-date)))))
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                                  (y (+ (string-to-number y-str)
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                                        (* 100 (/ current-y 100)))))
                             (if (> (- y current-y) 50)
                                 (- y 100)
                               (if (> (- current-y y) 50)
                                   (+ y 100)
                                 y)))
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                         (string-to-number y-str)))))
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            (if dd-name
                (mark-calendar-days-named
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                 (cdr (assoc-string (substring dd-name 0 3)
                                    (calendar-make-alist
                                     calendar-day-name-array
                                     0
                                     '(lambda (x) (substring x 0 3)))
                                    t)))
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              (if mm-name
                  (if (string-equal mm-name "*")
                      (setq mm 0)
                    (setq mm
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                          (cdr (assoc-string
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                                mm-name
                                (calendar-make-alist
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                                  calendar-bahai-month-name-array)
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                                t)))))
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              (calendar-bahai-mark-date-pattern mm dd yy)))))
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      (setq d (cdr d)))))

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(defun calendar-bahai-mark-date-pattern (month day year)
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  "Mark dates in calendar window that conform to Bahá'í date MONTH/DAY/YEAR.
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A value of 0 in any position is a wildcard."
  (save-excursion
    (set-buffer calendar-buffer)
    (if (and (/= 0 month) (/= 0 day))
        (if (/= 0 year)
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            ;; Fully specified Bahá'í date.
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            (let ((date (calendar-gregorian-from-absolute
                         (calendar-absolute-from-bahai
                          (list month day year)))))
              (if (calendar-date-is-visible-p date)
                  (mark-visible-calendar-date date)))
          ;; Month and day in any year--this taken from the holiday stuff.
          (let* ((bahai-date (calendar-bahai-from-absolute
                                (calendar-absolute-from-gregorian
                                 (list displayed-month 15 displayed-year))))
                 (m (extract-calendar-month bahai-date))
                 (y (extract-calendar-year bahai-date))
                 (date))
            (if (< m 1)
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                nil;;   Bahá'í calendar doesn't apply.
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              (increment-calendar-month m y (- 10 month))
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              (if (> m 7);;  Bahá'í date might be visible
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                  (let ((date (calendar-gregorian-from-absolute
                               (calendar-absolute-from-bahai
                                (list month day y)))))
                    (if (calendar-date-is-visible-p date)
                        (mark-visible-calendar-date date)))))))
      ;; Not one of the simple cases--check all visible dates for match.
      ;; Actually, the following code takes care of ALL of the cases, but
      ;; it's much too slow to be used for the simple (common) cases.
      (let ((m displayed-month)
            (y displayed-year)
            (first-date)
            (last-date))
        (increment-calendar-month m y -1)
        (setq first-date
              (calendar-absolute-from-gregorian
               (list m 1 y)))
        (increment-calendar-month m y 2)
        (setq last-date
              (calendar-absolute-from-gregorian
               (list m (calendar-last-day-of-month m y) y)))
        (calendar-for-loop date from first-date to last-date do
          (let* ((b-date (calendar-bahai-from-absolute date))
                 (i-month (extract-calendar-month b-date))
                 (i-day (extract-calendar-day b-date))
                 (i-year (extract-calendar-year b-date)))
            (and (or (zerop month)
                     (= month i-month))
                 (or (zerop day)
                     (= day i-day))
                 (or (zerop year)
                     (= year i-year))
                 (mark-visible-calendar-date
                  (calendar-gregorian-from-absolute date)))))))))

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(defun diary-bahai-insert-entry (arg)
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  "Insert a diary entry.
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For the Bahá'í date corresponding to the date indicated by point.
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Prefix arg will make the entry nonmarking."
  (interactive "P")
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  (let* ((calendar-month-name-array calendar-bahai-month-name-array))
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    (make-diary-entry
     (concat
      bahai-diary-entry-symbol
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      (calendar-date-string
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       (calendar-bahai-from-absolute
        (calendar-absolute-from-gregorian
         (calendar-cursor-to-date t)))
       nil t))
     arg)))

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(defun diary-bahai-insert-monthly-entry (arg)
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  "Insert a monthly diary entry.
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For the day of the Bahá'í month corresponding to the date indicated by point.
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Prefix arg will make the entry nonmarking."
  (interactive "P")
  (let* ((calendar-date-display-form
          (if european-calendar-style '(day " * ") '("* " day )))
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         (calendar-month-name-array calendar-bahai-month-name-array))
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    (make-diary-entry
     (concat
      bahai-diary-entry-symbol
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      (calendar-date-string
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       (calendar-bahai-from-absolute
        (calendar-absolute-from-gregorian
         (calendar-cursor-to-date t)))))
     arg)))

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(defun diary-bahai-insert-yearly-entry (arg)
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  "Insert an annual diary entry.
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For the day of the Bahá'í year corresponding to the date indicated by point.
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Prefix arg will make the entry nonmarking."
  (interactive "P")
  (let* ((calendar-date-display-form
          (if european-calendar-style
              '(day " " monthname)
            '(monthname " " day)))
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         (calendar-month-name-array calendar-bahai-month-name-array))
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    (make-diary-entry
     (concat
      bahai-diary-entry-symbol
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      (calendar-date-string
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       (calendar-bahai-from-absolute
        (calendar-absolute-from-gregorian
         (calendar-cursor-to-date t)))))
     arg)))

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;; Backward compatibility.
(define-obsolete-function-alias
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  'list-bahai-diary-entries 'diary-bahai-list-entries "23.1")
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(define-obsolete-function-alias
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  'mark-bahai-diary-entries 'diary-bahai-mark-entries "23.1")
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(define-obsolete-function-alias
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  'insert-bahai-diary-entry 'diary-bahai-insert-entry "23.1")
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(define-obsolete-function-alias
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  'insert-monthly-bahai-diary-entry 'diary-bahai-insert-monthly-entry "23.1")
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(define-obsolete-function-alias
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  'insert-yearly-bahai-diary-entry 'diary-bahai-insert-yearly-entry "23.1")
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(define-obsolete-function-alias
  'mark-bahai-calendar-date-pattern 'calendar-bahai-mark-date-pattern "23.1")
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(define-obsolete-function-alias
  'calendar-goto-bahai-date 'calendar-bahai-goto-date "23.1")
(define-obsolete-function-alias
  'calendar-print-bahai-date 'calendar-bahai-print-date "23.1")
540

541 542
(provide 'cal-bahai)

543
;; arch-tag: c1cb1d67-862a-4264-a01c-41cb4df01f14
544
;;; cal-bahai.el ends here