;;; thai-util.el --- utilities for Thai -*- coding: utf-8; -*-

;; Copyright (C) 2000-2019 Free Software Foundation, Inc.
;; Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
;;   2005, 2006, 2007, 2008, 2009, 2010, 2011
;;   National Institute of Advanced Industrial Science and Technology (AIST)
;;   Registration Number H14PRO021

;; Keywords: mule, multilingual, Thai, i18n

;; 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 <https://www.gnu.org/licenses/>.

;;; Commentary:

;;; Code:

(defvar thai-auto-composition-mode)

;; Setting information of Thai characters.

(defconst thai-category-table (make-category-table))
(define-category ?c "Thai consonant" thai-category-table)
(define-category ?v "Thai upper/lower vowel" thai-category-table)
(define-category ?t "Thai tone mark" thai-category-table)
(define-category ?u "Thai tone mark and upper sign" thai-category-table)
(define-category ?I "THAI CHARACTER SARA I" thai-category-table)
(define-category ?U "THAI CHARACTER THANTHAKHAT" thai-category-table)

;; The general composing rules are as follows:
;;
;;                          T
;;       V        U         V                  U
;; CV -> C, CU -> C, CVT -> C, Cv -> C, CvU -> C
;;                                   v         v
;;
;; where C: consonant, V: vowel upper, v: vowel lower,
;;       T: tone mark, U: tone mark and upper sign.
;; Special rule: The sign `์' can be put on the vowel `ิ'.


(defvar thai-composition-pattern
  "\\cc\\(\\cu\\|\\cI\\cU\\|\\cv\\ct?\\)\\|\\cv\\ct\\|\\cI\\cU"
  "Regular expression matching a Thai composite sequence.")

(let ((l '((?ก consonant)	; 0xA1
	   (?ข consonant)	; 0xA2
	   (?ฃ consonant)	; 0xA3
	   (?ค consonant)	; 0xA4
	   (?ฅ consonant)	; 0xA5
	   (?ฆ consonant)	; 0xA6
	   (?ง consonant)	; 0xA7
	   (?จ consonant)	; 0xA8
	   (?ฉ consonant)	; 0xA9
	   (?ช consonant)	; 0xAA
	   (?ซ consonant)	; 0xAB
	   (?ฌ consonant)	; 0xAC
	   (?ญ consonant)	; 0xAD
	   (?ฎ consonant)	; 0xAE
	   (?ฏ consonant)	; 0xAF
	   (?ฐ consonant)	; 0xB0
	   (?ฑ consonant)	; 0xB1
	   (?ฒ consonant)	; 0xB2
	   (?ณ consonant)	; 0xB3
	   (?ด consonant)	; 0xB4
	   (?ต consonant)	; 0xB5
	   (?ถ consonant)	; 0xB6
	   (?ท consonant)	; 0xB7
	   (?ธ consonant)	; 0xB8
	   (?น consonant)	; 0xB9
	   (?บ consonant)	; 0xBA
	   (?ป consonant)	; 0xBB
	   (?ผ consonant)	; 0xBC
	   (?ฝ consonant)	; 0xBD
	   (?พ consonant)	; 0xBE
	   (?ฟ consonant)	; 0xBF
	   (?ภ consonant)	; 0xC0
	   (?ม consonant)	; 0xC1
	   (?ย consonant)	; 0xC2
	   (?ร consonant)	; 0xC3
	   (?ฤ vowel-base)	; 0xC4
	   (?ล consonant)	; 0xC5
	   (?ฦ vowel-base)	; 0xC6
	   (?ว consonant)	; 0xC7
	   (?ศ consonant)	; 0xC8
	   (?ษ consonant)	; 0xC9
	   (?ส consonant)	; 0xCA
	   (?ห consonant)	; 0xCB
	   (?ฬ consonant)	; 0xCC
	   (?อ consonant)	; 0xCD
	   (?ฮ consonant)	; 0xCE
	   (?ฯ special)	; 0xCF
	   (?ะ vowel-base)	; 0xD0
	   (?ั vowel-upper)	; 0xD1
	   (?า vowel-base)	; 0xD2
	   (?ำ vowel-base)	; 0xD3
	   (?ิ vowel-upper)	; 0xD4
	   (?ี vowel-upper)	; 0xD5
	   (?ึ vowel-upper)	; 0xD6
	   (?ื vowel-upper)	; 0xD7
	   (?ุ vowel-lower)	; 0xD8
	   (?ู vowel-lower)	; 0xD9
	   (?ฺ vowel-lower)	; 0xDA
	   (?฻ invalid)	; 0xDA
	   (?฼ invalid)	; 0xDC
	   (?฽ invalid)	; 0xDC
	   (?฾ invalid)	; 0xDC
	   (?฿ special)	; 0xDF
	   (?เ vowel-base)	; 0xE0
	   (?แ vowel-base)	; 0xE1
	   (?โ vowel-base)	; 0xE2
	   (?ใ vowel-base)	; 0xE3
	   (?ไ vowel-base)	; 0xE4
	   (?ๅ vowel-base)	; 0xE5
	   (?ๆ special)	; 0xE6
	   (?็ sign-upper)	; 0xE7
	   (?่ tone)		; 0xE8
	   (?้ tone)		; 0xE9
	   (?๊ tone)		; 0xEA
	   (?๋ tone)		; 0xEB
	   (?์ sign-upper)	; 0xEC
	   (?ํ sign-upper)	; 0xED
	   (?๎ sign-upper)	; 0xEE
	   (?๏ special)	; 0xEF
	   (?๐ special)	; 0xF0
	   (?๑ special)	; 0xF1
	   (?๒ special)	; 0xF2
	   (?๓ special)	; 0xF3
	   (?๔ special)	; 0xF4
	   (?๕ special)	; 0xF5
	   (?๖ special)	; 0xF6
	   (?๗ special)	; 0xF7
	   (?๘ special)	; 0xF8
	   (?๙ special)	; 0xF9
	   (?๚ special)	; 0xFA
	   (?๛ special)	; 0xFB
	   (?๜ invalid)	; 0xFC
	   (?๝ invalid)	; 0xFD
	   (?๞ invalid)	; 0xFE
	   ))
      elm)
  (while l
    (setq elm (car l) l (cdr l))
    (let ((char (car elm))
	  (ptype (nth 1 elm)))
      (put-char-code-property char 'phonetic-type ptype)
      (cond ((eq ptype 'consonant)
	     (modify-category-entry char ?c thai-category-table))
	    ((memq ptype '(vowel-upper vowel-lower))
	     (modify-category-entry char ?v thai-category-table)
	     (if (= char ?ิ)
		 ;; Give category `I' to "SARA I".
		 (modify-category-entry char ?I thai-category-table)))
	    ((eq ptype 'tone)
	     (modify-category-entry char ?t thai-category-table)
	     (modify-category-entry char ?u thai-category-table))
	    ((eq ptype 'sign-upper)
	     (modify-category-entry char ?u thai-category-table)
	     (if (= char ?์)
		 ;; Give category `U' to "THANTHAKHAT".
		 (modify-category-entry char ?U thai-category-table)))))))

(defun thai-compose-syllable (beg end &optional category-set string)
  (or category-set
      (setq category-set
	    (char-category-set (if string (aref string beg) (char-after beg)))))
  (if (aref category-set ?c)
      ;; Starting with a consonant.  We do relative composition.
      (if string
	  (compose-string string beg end)
	(compose-region beg end))
    ;; Vowel tone sequence.
    (if string
	(compose-string string beg end (list (aref string beg) '(Bc . Bc)
					     (aref string (1+ beg))))
      (compose-region beg end (list (char-after beg) '(Bc . Bc)
				    (char-after (1+ beg))))))
  (- end beg))

;;;###autoload
(defun thai-compose-region (beg end)
  "Compose Thai characters in the region.
When called from a program, expects two arguments,
positions (integers or markers) specifying the region."
  (interactive "r")
  (let ((pos (point)))
    (save-restriction
      (narrow-to-region beg end)
      (goto-char (point-min))
      (with-category-table thai-category-table
	(while (re-search-forward thai-composition-pattern nil t)
	  (setq beg (match-beginning 0) end (match-end 0))
	  (if (and (> pos beg) (< pos end))
	      (setq pos end))
	  (thai-compose-syllable beg end
				 (char-category-set (char-after beg))))))
    (goto-char pos)))

;;;###autoload
(defun thai-compose-string (string)
  "Compose Thai characters in STRING and return the resulting string."
  (with-category-table thai-category-table
    (let ((idx 0))
      (while (setq idx (string-match thai-composition-pattern string idx))
	(thai-compose-syllable idx (match-end 0) nil string)
	(setq idx (match-end 0)))))
  string)

;;;###autoload
(defun thai-compose-buffer ()
  "Compose Thai characters in the current buffer."
  (interactive)
  (thai-compose-region (point-min) (point-max)))

;;;###autoload
(defun thai-composition-function (gstring)
  (if (= (lgstring-char-len gstring) 1)
      (compose-gstring-for-graphic gstring)
    (or (font-shape-gstring gstring)
	(let ((glyph-len (lgstring-glyph-len gstring))
	      (last-char (lgstring-char gstring
					(1- (lgstring-char-len gstring))))
	      (i 0)
	      glyph)
	  (while (and (< i glyph-len)
		      (setq glyph (lgstring-glyph gstring i)))
	    (setq i (1+ i)))
	  (if (= last-char ?ำ)
	      (setq i (1- i)))
	  (compose-glyph-string-relative gstring 0 i 0.1)))))

;; Thai-word-mode requires functions in the feature `thai-word'.
(require 'thai-word)

(defvar thai-word-mode-map
  (let ((map (make-sparse-keymap)))
    (define-key map [remap forward-word] 'thai-forward-word)
    (define-key map [remap backward-word] 'thai-backward-word)
    (define-key map [remap kill-word] 'thai-kill-word)
    (define-key map [remap backward-kill-word] 'thai-backward-kill-word)
    (define-key map [remap transpose-words] 'thai-transpose-words)
    map)
  "Keymap for `thai-word-mode'.")

(define-minor-mode thai-word-mode
  "Minor mode to make word-oriented commands aware of Thai words.
With a prefix argument ARG, enable the mode if ARG is positive,
and disable it otherwise.  If called from Lisp, enable the mode
if ARG is omitted or nil.  The commands affected are
\\[forward-word], \\[backward-word], \\[kill-word], \\[backward-kill-word],
\\[transpose-words], and \\[fill-paragraph]."
  :global t :group 'mule
  (cond (thai-word-mode
	 ;; This enables linebreak between Thai characters.
	 (modify-category-entry (make-char 'thai-tis620) ?|)
	 ;; This enables linebreak at a Thai word boundary.
	 (put-charset-property 'thai-tis620 'fill-find-break-point-function
			       'thai-fill-find-break-point))
	(t
	 (modify-category-entry (make-char 'thai-tis620) ?| nil t)
	 (put-charset-property 'thai-tis620 'fill-find-break-point-function
			       nil))))

;; Function to call on entering the Thai language environment.
(defun setup-thai-language-environment-internal ()
  (thai-word-mode 1))

;; Function to call on exiting the Thai language environment.
(defun exit-thai-language-environment-internal ()
  (thai-word-mode -1))

;;
(provide 'thai-util)

;;; thai-util.el ends here
