;;; tamil99.el --- Tamil99 input method -*- lexical-binding: t -*-

;; Tamil99 input method for Emacs
;; Copyright (C) 2022 Arun Isaac
;;
;; Author: Arun Isaac <arunisaac@systemreboot.net>
;; Version: 0.1.0
;; Keywords: abbrev, convenience, i18n
;; Homepage: https://git.systemreboot.net/tamil99
;; Package-Requires: ((emacs "25.1"))

;; This file is part of tamil99.

;; tamil99 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.

;; tamil99 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 tamil99.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:
;;
;; tamil99 is an implementation of the tamil99 input method for Emacs.
;;
;; Usage:
;;
;; Switch to the tamil99 input method using
;;
;; M-x set-input-method tamil99 RET
;; 
;; Enjoy typing in Tamil!
;;
;; tamil99 Emacs தொகுப்பிக்கு tamil99 உள்ளீட்டு முறையை அளிப்பது.
;;
;; பயன்பாடு:
;;
;; tamil99 உள்ளீட்டு முறைக்கு மாற
;;
;; M-x set-input-method tamil99 RET
;;
;; தமிழில் தட்டச்சிட்டு மகிழ்க!

;;; Code:

(require 'pcase)
(require 'quail)
(require 'seq)

(quail-define-package
 "tamil99" "Tamil" "tamil99"
 t "Tamil99 input method")

(defconst tamil99-vowels
  '(("q" "ஆ")
    ("w" "ஈ")
    ("e" "ஊ")
    ("r" "ஐ")
    ("t" "ஏ")
    ("a" "அ")
    ("s" "இ")
    ("d" "உ")
    ("g" "எ")
    ("z" "ஔ")
    ("x" "ஓ")
    ("c" "ஒ"))
  "Mapping for vowels.")

(defconst tamil99-vowel-modifiers
  '(("q" "ா")
    ("w" "ீ")
    ("e" "ூ")
    ("r" "ை")
    ("t" "ே")
    ("a" "")
    ("s" "ி")
    ("d" "ு")
    ("g" "ெ")
    ("z" "ௌ")
    ("x" "ோ")
    ("c" "ொ")
    ("f" "்"))
  "Mapping for vowel modifiers.")

(defconst tamil99-vallinam-consonants
  '(("h" "க")
    ("[" "ச")
    ("o" "ட")
    ("l" "த")
    ("j" "ப")
    ("u" "ற"))
  "Mapping for vallinam consonants.")

(defconst tamil99-mellinam-consonants
  '(("b" "ங")
    ("]" "ஞ")
    ("p" "ண")
    (";" "ந")
    ("k" "ம")
    ("i" "ன"))
  "Mapping for mellinam consonants.")

(defconst tamil99-idaiinam-consonants
  '(("'" "ய")
    ("m" "ர")
    ("n" "ல")
    ("v" "வ")
    ("/" "ழ")
    ("y" "ள"))
  "Mapping for idaiinam consonants.")

(defconst tamil99-grantham-consonants
  '(("Q" "ஸ")
    ("W" "ஷ")
    ("E" "ஜ")
    ("R" "ஹ"))
  "Mapping for grantham consonants.")

(defconst tamil99-consonants
  (append tamil99-vallinam-consonants
          tamil99-mellinam-consonants
          tamil99-idaiinam-consonants
          tamil99-grantham-consonants)
  "Mapping for all consonants.")

(defconst tamil99-other
  `(("T" ,(vector "க்ஷ"))
    ("Y" ,(vector "ஶஂரீ"))
    ("O" "[")
    ("P" "]")
    ("A" "௹")
    ("S" "௺")
    ("D" "௸")
    ("F" "ஃ")
    ("K" "\"")
    ("L" ":")
    (":" ";")
    ("\"" "'")
    ("Z" "௳")
    ("X" "௴")
    ("C" "௵")
    ("V" "௶")
    ("B" "௷")
    ("M" "/"))
  "Mapping for miscellaneous characters.")

(defun tamil99-install ()
  "Install tamil99 input method."
  (quail-define-rules)
  ;; உயிர்
  ;; vowel
  (mapc (pcase-lambda (`(,vowel-key ,vowel))
          (quail-defrule vowel-key vowel))
        tamil99-vowels)
  (mapc (pcase-lambda (`(,consonant-key ,consonant))
          ;; அகர உயிர்மெய்
          ;; consonant with agaram (அ)
          (quail-defrule consonant-key consonant)
          ;; மெய்யொற்று பின் அகர உயிர்மெய்
          ;; pulli on double consonant
          (quail-defrule (concat consonant-key consonant-key)
                         (vector (concat consonant "்" consonant)))
          (mapc (pcase-lambda (`(,vowel-key ,vowel-modifier))
                  ;; உயிர்மெய்
                  ;; vowel+consonant
                  (quail-defrule (concat consonant-key vowel-key)
                                 (vector (concat consonant vowel-modifier)))
                  ;; மெய்யொற்று பின் உயிர்மெய்
                  ;; vowel+consonant after double consonant
                  (quail-defrule (concat consonant-key consonant-key vowel-key)
                                 (vector (concat consonant "்" consonant vowel-modifier))))
                tamil99-vowel-modifiers))
        tamil99-consonants)
  (seq-mapn (pcase-lambda (`(,mellinam-consonant-key ,mellinam-consonant)
                           `(,vallinam-consonant-key ,vallinam-consonant))
              ;; மெல்லினம் பின் வல்லினம்
              ;; vallinam after mellinam
              (quail-defrule (concat mellinam-consonant-key vallinam-consonant-key)
                             (vector (concat mellinam-consonant "்" vallinam-consonant)))
              (mapc (pcase-lambda (`(,vowel-key ,vowel-modifier))
                      ;; மெல்லின ஒற்றொட்டிய வல்லினம் பின் உயிர்மெய்
                      ;; vowel+consonant after mellinam-vallinam consonant
                      (quail-defrule (concat mellinam-consonant-key vallinam-consonant-key vowel-key)
                                     (vector (concat mellinam-consonant "்" vallinam-consonant vowel-modifier))))
                    tamil99-vowel-modifiers))
            tamil99-mellinam-consonants
            tamil99-vallinam-consonants)
  ;; பிற வரியுருக்கள்
  ;; other characters
  (mapc (pcase-lambda (`(,key ,translation))
          (quail-defrule key translation))
        tamil99-other))

(tamil99-install)

(provide 'tamil99)

;;; tamil99.el ends here