1;;; metamail.el --- Metamail interface for GNU Emacs
2
3;; Copyright (C) 1993, 1996, 2001-2021 Free Software Foundation, Inc.
4
5;; Author: Masanobu UMEDA <umerin@mse.kyutech.ac.jp>
6;; Keywords: mail, news, mime, multimedia
7
8;; This file is part of GNU Emacs.
9
10;; GNU Emacs is free software: you can redistribute it and/or modify
11;; it under the terms of the GNU General Public License as published by
12;; the Free Software Foundation, either version 3 of the License, or
13;; (at your option) any later version.
14
15;; GNU Emacs is distributed in the hope that it will be useful,
16;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18;; GNU General Public License for more details.
19
20;; You should have received a copy of the GNU General Public License
21;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
22
23;;; Commentary:
24
25;; Note: Metamail does not have all the options which are compatible with
26;; the environment variables.  For that reason, metamail.el has to
27;; hack the environment variables.  In addition, there is no way to
28;; display all header fields without extra informative body messages
29;; which are suppressed by the "-q" option.
30
31;; The idea of using metamail to process MIME messages is from
32;; gnus-mime.el by Spike <Spike@world.std.com>.
33
34;;; Code:
35
36(defvar rmail-current-message)
37(defvar rmail-message-vector)
38
39(defgroup metamail nil
40  "Metamail interface for Emacs."
41  :group 'mail
42  :group 'processes)
43
44(defcustom metamail-program-name "metamail"
45  "Metamail program name."
46  :type 'string
47  :group 'metamail)
48
49(defcustom metamail-mailer-name "emacs"
50  "Mailer name set to MM_MAILER environment variable."
51  :type 'string
52  :group 'metamail)
53
54(defvar metamail-environment '("KEYHEADS=*" "MM_QUIET=1")
55  "Environment variables passed to `metamail'.
56It must be a list of strings that have the format ENVVARNAME=VALUE.
57It is not expected to be altered globally by `set' or `setq'.
58Instead, change its value temporary using `let' or `let*' form.")
59
60(defcustom metamail-switches '("-x" "-d" "-z")
61  "Switches for `metamail' program.
62`-z' is required to remove zap file.
63It is not expected to be altered globally by `set' or `setq'.
64Instead, change its value temporary using `let' or `let*' form.
65`-m MAILER' argument is automatically generated from the
66`metamail-mailer-name' variable."
67  :type '(repeat (string :tag "Switch"))
68  :group 'metamail)
69
70;;;###autoload
71(defun metamail-interpret-header ()
72  "Interpret a header part of a MIME message in current buffer.
73Its body part is not interpreted at all."
74  (interactive)
75  (save-excursion
76    (let* ((buffer-read-only nil)
77	   (metamail-switches		;Inhibit processing an empty body.
78	    (append metamail-switches '("-c" "text/plain" "-E" "7bit")))
79	   (end (progn
80		  (goto-char (point-min))
81		  (search-forward "\n\n" nil 'move)
82		  ;; An extra newline is inserted by metamail if there
83		  ;; is no body part.  So, insert a dummy body by
84		  ;; itself.
85		  (insert "\n")
86		  (point))))
87      (metamail-region (point-min) end nil nil 'nodisplay)
88      ;; Remove an extra newline inserted by myself.
89      (goto-char (point-min))
90      (if (search-forward "\n\n\n" nil t)
91	  (delete-char -1))
92      )))
93
94;;;###autoload
95(defun metamail-interpret-body (&optional viewmode nodisplay)
96  "Interpret a body part of a MIME message in current buffer.
97Optional argument VIEWMODE specifies the value of the
98EMACS_VIEW_MODE environment variable (defaulted to 1).
99Optional argument NODISPLAY non-nil means buffer is not
100redisplayed as output is inserted.
101Its header part is not interpreted at all."
102  (interactive "p")
103  (save-excursion
104    (let ((contype nil)
105	  (encoding nil)
106	  (end (progn
107		 (goto-char (point-min))
108		 (search-forward "\n\n" nil t)
109		 (point))))
110      ;; Find Content-Type and Content-Transfer-Encoding from the header.
111      (save-restriction
112	(narrow-to-region (point-min) end)
113	(setq contype
114	      (or (mail-fetch-field "Content-Type") "text/plain"))
115	(setq encoding
116	      (or (mail-fetch-field "Content-Transfer-Encoding") "7bit")))
117      ;; Interpret the body part only.
118      (let ((metamail-switches		;Process body part only.
119	     (append metamail-switches
120		     (list "-b" "-c" contype "-E" encoding))))
121	(metamail-region end (point-max) viewmode nil nodisplay))
122      ;; This mode specific hack is no longer appropriate in mbox Rmail.
123      ;; Pre-mbox, we have just modified the actual folder, so we
124      ;; update the message-vector with the new end position of the
125      ;; current message.  In mbox Rmail, all we have done is modify a
126      ;; display copy of the message.  Note also that point-max is a
127      ;; marker in the wrong buffer: the message-vector contains
128      ;; markers in rmail-view-buffer (which is not in rmail-mode).
129      ;; So this hack actually breaks the message-vector.
130      ;; If you're calling this on the actual rmail-view-buffer (or a
131      ;; non-swapped rmail-buffer), you would still need this hack.
132      ;; But you're not going to do that.
133;;;      (cond ((eq major-mode 'rmail-mode)
134;;;	     ;; Adjust the marker of this message if in Rmail mode buffer.
135;;;	     (set-marker (aref rmail-message-vector (1+ rmail-current-message))
136;;;			 (point-max))))
137      )))
138
139;;;###autoload
140(defun metamail-buffer (&optional viewmode buffer nodisplay)
141  "Process current buffer through `metamail'.
142Optional argument VIEWMODE specifies the value of the
143EMACS_VIEW_MODE environment variable (defaulted to 1).
144Optional argument BUFFER specifies a buffer to be filled (nil
145means current).
146Optional argument NODISPLAY non-nil means buffer is not
147redisplayed as output is inserted."
148  (interactive "p")
149  (metamail-region (point-min) (point-max) viewmode buffer nodisplay))
150
151;;;###autoload
152(defun metamail-region (beg end &optional viewmode buffer nodisplay)
153  "Process current region through `metamail'.
154Optional argument VIEWMODE specifies the value of the
155EMACS_VIEW_MODE environment variable (defaulted to 1).
156Optional argument BUFFER specifies a buffer to be filled (nil
157means current).
158Optional argument NODISPLAY non-nil means buffer is not
159redisplayed as output is inserted."
160  (interactive "r\np")
161  (let ((curbuf (current-buffer))
162	(buffer-read-only nil)
163	(metafile (make-temp-file "metamail"))
164	(option-environment
165	 (list (format "EMACS_VIEW_MODE=%d"
166		       (if (numberp viewmode) viewmode 1)))))
167    (save-excursion
168      ;; Gee!  Metamail does not output to stdout if input comes from
169      ;; stdin.
170      (let ((selective-display nil))	;Disable ^M to nl translation.
171	(write-region beg end metafile nil 'nomessage))
172      (if buffer
173	  (set-buffer buffer))
174      (setq buffer-read-only nil)
175      ;; Clear destination buffer.
176      (if (eq curbuf (current-buffer))
177	  (delete-region beg end)
178	(delete-region (point-min) (point-max)))
179      ;; We have to pass the environment variable KEYHEADS to display
180      ;; all header fields.  Metamail should have an optional argument
181      ;; to pass such information directly.
182      (let ((process-environment
183	     (append process-environment
184		     metamail-environment option-environment))
185	    (coding-system-for-read 'undecided))
186	(apply (function call-process)
187	       metamail-program-name
188	       nil
189	       t			;Output to current buffer
190	       (not nodisplay)		;Force redisplay
191	       (append metamail-switches
192		       (list "-m" (or metamail-mailer-name "emacs"))
193		       (list metafile))))
194      ;; `metamail' may not delete the temporary file!
195      (condition-case error
196	  (delete-file metafile)
197	(error nil))
198      )))
199
200(provide 'metamail)
201
202;;; metamail.el ends here
203