;;; mel.el --- A MIME encoding/decoding library.

;; Copyright (C) 1995,1996,1997,1998,1999 Free Software Foundation, Inc.

;; Author: MORIOKA Tomohiko <tomo@m17n.org>
;; Created: 1995/6/25
;; Keywords: MIME, Base64, Quoted-Printable, uuencode, gzip64

;; This file is part of FLIM (Faithful Library about Internet Message).

;; This program 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.

;; This program 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 this program; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Code:

(require 'mime-def)
(require 'poem)
(require 'alist)
(require 'path-util)

(defcustom mime-encoding-list
  '("7bit" "8bit" "binary" "base64" "quoted-printable")
  "List of Content-Transfer-Encoding.  Each encoding must be string."
  :group 'mime
  :type '(repeat string))

(defun mime-encoding-list (&optional service)
  "Return list of Content-Transfer-Encoding.
If SERVICE is specified, it returns available list of
Content-Transfer-Encoding for it."
  (if service
      (let (dest)
	(mapatoms (lambda (sym)
		    (or (eq sym nil)
			(setq dest (cons (symbol-name sym) dest)))
		    )
		  (symbol-value (intern (format "%s-obarray" service))))
	(let ((rest mel-encoding-module-alist)
	      pair)
	  (while (setq pair (car rest))
	    (let ((key (car pair)))
	      (or (member key dest)
		  (<= (length key) 1)
		  (setq dest (cons key dest))))
	    (setq rest (cdr rest)))
	  )
	dest)
    mime-encoding-list))

(defun mime-encoding-alist (&optional service)
  "Return table of Content-Transfer-Encoding for completion."
  (mapcar #'list (mime-encoding-list service)))

(defsubst mel-use-module (name encodings)
  (while encodings
    (set-alist 'mel-encoding-module-alist
	       (car encodings)
	       (cons name (cdr (assoc (car encodings)
				      mel-encoding-module-alist))))
    (setq encodings (cdr encodings))))

(defsubst mel-find-function (service encoding)
  (mel-find-function-from-obarray
   (symbol-value (intern (format "%s-obarray" service))) encoding))


;;; @ setting for modules
;;;

(mel-define-backend "7bit")
(mel-define-method-function (mime-encode-string string (nil "7bit"))
			    'identity)
(mel-define-method-function (mime-decode-string string (nil "7bit"))
			    'identity)
(mel-define-method mime-encode-region (start end (nil "7bit")))
(mel-define-method mime-decode-region (start end (nil "7bit")))
(mel-define-method-function (mime-insert-encoded-file filename (nil "7bit"))
			    'insert-file-contents-as-binary)
(mel-define-method-function (mime-write-decoded-region
			     start end filename (nil "7bit"))
			    'write-region-as-binary)

(mel-define-backend "8bit" ("7bit"))

(mel-define-backend "binary" ("8bit"))

(defvar mel-b-builtin
   (and (fboundp 'base64-encode-string)
        (subrp (symbol-function 'base64-encode-string))))

(when mel-b-builtin
  (mel-define-backend "base64")
  (mel-define-method-function (mime-encode-string string (nil "base64"))
			      'base64-encode-string)
  (mel-define-method-function (mime-decode-string string (nil "base64"))
			      'base64-decode-string)
  (mel-define-method-function (mime-encode-region start end (nil "base64"))
			      'base64-encode-region)
  (mel-define-method-function (mime-decode-region start end (nil "base64"))
			      'base64-decode-region)  
  (mel-define-method mime-insert-encoded-file (filename (nil "base64"))
    "Encode contents of file FILENAME to base64, and insert the result.
It calls external base64 encoder specified by
`base64-external-encoder'.  So you must install the program (maybe
mmencode included in metamail or XEmacs package)."
    (interactive "*fInsert encoded file: ")
    (insert (base64-encode-string
	     (with-temp-buffer
	       (set-buffer-multibyte nil)
	       (insert-file-contents-as-binary filename)
	       (buffer-string))))
    (or (bolp) (insert ?\n)))
    
  (mel-define-method-function (encoded-text-encode-string string (nil "B"))
			      'base64-encode-string)
  (mel-define-method encoded-text-decode-string (string (nil "B"))
    (if (string-match (eval-when-compile
			(concat "\\`" B-encoded-text-regexp "\\'"))
		      string)
	(base64-decode-string string)
      (error "Invalid encoded-text %s" string)))
  )

(mel-use-module 'mel-b-el '("base64" "B"))
(mel-use-module 'mel-q '("quoted-printable" "Q"))
(mel-use-module 'mel-g '("x-gzip64"))
(mel-use-module 'mel-u '("x-uue" "x-uuencode"))

(defvar mel-b-ccl-module
  (and (featurep 'mule)
       (progn
	 (require 'path-util)
	 (module-installed-p 'mel-b-ccl))))

(defvar mel-q-ccl-module
  (and (featurep 'mule)
       (progn
	 (require 'path-util)
	 (module-installed-p 'mel-q-ccl))))

(when mel-b-ccl-module
  (mel-use-module 'mel-b-ccl '("base64" "B")))

(when mel-q-ccl-module
  (mel-use-module 'mel-q-ccl '("quoted-printable" "Q")))

(when base64-dl-module
  (mel-use-module 'mel-b-dl '("base64" "B")))


;;; @ region
;;;

;;;###autoload
(defun mime-encode-region (start end encoding)
  "Encode region START to END of current buffer using ENCODING.
ENCODING must be string."
  (interactive
   (list (region-beginning)(region-end)
	 (completing-read "Encoding: "
			  (mime-encoding-alist)
			  nil t "base64")))
  (funcall (mel-find-function 'mime-encode-region encoding) start end))


;;;###autoload
(defun mime-decode-region (start end encoding)
  "Decode region START to END of current buffer using ENCODING.
ENCODING must be string."
  (interactive
   (list (region-beginning)(region-end)
	 (completing-read "Encoding: "
			  (mime-encoding-alist 'mime-decode-region)
			  nil t "base64")))
  (funcall (mel-find-function 'mime-decode-region encoding)
	   start end))


;;; @ string
;;;

;;;###autoload
(defun mime-decode-string (string encoding)
  "Decode STRING using ENCODING.
ENCODING must be string.  If ENCODING is found in
`mime-string-decoding-method-alist' as its key, this function decodes
the STRING by its value."
  (let ((f (mel-find-function 'mime-decode-string encoding)))
    (if f
	(funcall f string)
      string)))


(mel-define-service encoded-text-encode-string (string encoding)
  "Encode STRING as encoded-text using ENCODING.  ENCODING must be string.")

(mel-define-service encoded-text-decode-string (string encoding)
  "Decode STRING as encoded-text using ENCODING.  ENCODING must be string.")

(defun base64-encoded-length (string)
  (* (/ (+ (length string) 2) 3) 4))

(defsubst Q-encoding-printable-char-p (chr mode)
  (and (not (memq chr '(?= ?? ?_)))
       (<= ?\  chr)(<= chr ?~)
       (cond ((eq mode 'text) t)
	     ((eq mode 'comment)
	      (not (memq chr '(?\( ?\) ?\\))))
	     (t
	      (string-match "[A-Za-z0-9!*+/=_---]" (char-to-string chr))))))

(defun Q-encoded-text-length (string &optional mode)
  (let ((l 0)(i 0)(len (length string)) chr)
    (while (< i len)
      (setq chr (aref string i))
      (if (or (Q-encoding-printable-char-p chr mode)
	      (eq chr ? ))
	  (setq l (+ l 1))
	(setq l (+ l 3)))
      (setq i (+ i 1)))
    l))


;;; @ file
;;;

;;;###autoload
(defun mime-insert-encoded-file (filename encoding)
  "Insert file FILENAME encoded by ENCODING format."
  (interactive
   (list (read-file-name "Insert encoded file: ")
	 (completing-read "Encoding: "
			  (mime-encoding-alist)
			  nil t "base64")))
  (funcall (mel-find-function 'mime-insert-encoded-file encoding)
	   filename))


;;;###autoload
(defun mime-write-decoded-region (start end filename encoding)
  "Decode and write current region encoded by ENCODING into FILENAME.
START and END are buffer positions."
  (interactive
   (list (region-beginning)(region-end)
	 (read-file-name "Write decoded region to file: ")
	 (completing-read "Encoding: "
			  (mime-encoding-alist 'mime-write-decoded-region)
			  nil t "base64")))
  (funcall (mel-find-function 'mime-write-decoded-region encoding)
	   start end filename))


;;; @ end
;;;

(provide 'mel)

;;; mel.el ends here.