;;; rfc2231.el --- Functions for decoding rfc2231 headers

;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
;;   2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; 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 <http://www.gnu.org/licenses/>.

;;; Commentary:

;;; Code:

(eval-when-compile (require 'cl))
(require 'ietf-drums)
(require 'rfc2047)
(autoload 'mm-encode-body "mm-bodies")
(autoload 'mail-header-remove-whitespace "mail-parse")
(autoload 'mail-header-remove-comments "mail-parse")

(defun rfc2231-get-value (ct attribute)
  "Return the value of ATTRIBUTE from CT."
  (cdr (assq attribute (cdr ct))))

(defun rfc2231-parse-qp-string (string)
  "Parse QP-encoded string using `rfc2231-parse-string'.
N.B.  This is in violation with RFC2047, but it seem to be in common use."
  (rfc2231-parse-string (rfc2047-decode-string string)))

(defun rfc2231-parse-string (string &optional signal-error)
  "Parse STRING and return a list.
The list will be on the form
 `(name (attribute . value) (attribute . value)...)'.

If the optional SIGNAL-ERROR is non-nil, signal an error when this
function fails in parsing of parameters.  Otherwise, this function
must never cause a Lisp error."
  (with-temp-buffer
    (let ((ttoken (ietf-drums-token-to-list ietf-drums-text-token))
	  (stoken (ietf-drums-token-to-list ietf-drums-tspecials))
	  (ntoken (ietf-drums-token-to-list "0-9"))
	  c type attribute encoded number parameters value)
      (ietf-drums-init
       (condition-case nil
	   (mail-header-remove-whitespace
	    (mail-header-remove-comments string))
	 ;; The most likely cause of an error is unbalanced parentheses
	 ;; or double-quotes.  If all parentheses and double-quotes are
	 ;; quoted meaninglessly with backslashes, removing them might
	 ;; make it parseable.  Let's try...
	 (error
	  (let (mod)
	    (when (and (string-match "\\\\\"" string)
		       (not (string-match "\\`\"\\|[^\\]\"" string)))
	      (setq string (mm-replace-in-string string "\\\\\"" "\"")
		    mod t))
	    (when (and (string-match "\\\\(" string)
		       (string-match "\\\\)" string)
		       (not (string-match "\\`(\\|[^\\][()]" string)))
	      (setq string (mm-replace-in-string string "\\\\\\([()]\\)" "\\1")
		    mod t))
	    (or (and mod
		     (ignore-errors
		       (mail-header-remove-whitespace
			(mail-header-remove-comments string))))
		;; Finally, attempt to extract only type.
		(if (string-match
		     (concat "\\`[\t\n ]*\\([^" ietf-drums-tspecials "\t\n ]+"
			     "\\(?:/[^" ietf-drums-tspecials
			     "\t\n ]+\\)?\\)\\(?:[\t\n ;]\\|\\'\\)")
		     string)
		    (match-string 1 string)
		  ""))))))
      (let ((table (copy-syntax-table ietf-drums-syntax-table)))
	(modify-syntax-entry ?\' "w" table)
	(modify-syntax-entry ?* " " table)
	(modify-syntax-entry ?\; " " table)
	(modify-syntax-entry ?= " " table)
	;; The following isn't valid, but one should be liberal
	;; in what one receives.
	(modify-syntax-entry ?\: "w" table)
	(set-syntax-table table))
      (setq c (char-after))
      (when (and (memq c ttoken)
		 (not (memq c stoken))
		 (setq type (ignore-errors
			      (downcase
			       (buffer-substring (point) (progn
							   (forward-sexp 1)
							   (point)))))))
	;; Do the params
	(condition-case err
	    (progn
	      (while (not (eobp))
		(setq c (char-after))
		(unless (eq c ?\;)
		  (error "Invalid header: %s" string))
		(forward-char 1)
		;; If c in nil, then this is an invalid header, but
		;; since elm generates invalid headers on this form,
		;; we allow it.
		(when (setq c (char-after))
		  (if (and (memq c ttoken)
			   (not (memq c stoken)))
		      (setq attribute
			    (intern
			     (downcase
			      (buffer-substring
			       (point) (progn (forward-sexp 1) (point))))))
		    (error "Invalid header: %s" string))
		  (setq c (char-after))
		  (if (eq c ?*)
		      (progn
			(forward-char 1)
			(setq c (char-after))
			(if (not (memq c ntoken))
			    (setq encoded t
				  number nil)
			  (setq number
				(string-to-number
				 (buffer-substring
				  (point) (progn (forward-sexp 1) (point)))))
			  (setq c (char-after))
			  (when (eq c ?*)
			    (setq encoded t)
			    (forward-char 1)
			    (setq c (char-after)))))
		    (setq number nil
			  encoded nil))
		  (unless (eq c ?=)
		    (error "Invalid header: %s" string))
		  (forward-char 1)
		  (setq c (char-after))
		  (cond
		   ((eq c ?\")
		    (setq value (buffer-substring (1+ (point))
						  (progn
						    (forward-sexp 1)
						    (1- (point)))))
		    (when encoded
		      (setq value (mapconcat (lambda (c) (format "%%%02x" c))
					     value ""))))
		   ((and (or (memq c ttoken)
			     ;; EXTENSION: Support non-ascii chars.
			     (> c ?\177))
			 (not (memq c stoken)))
		    (setq value
			  (buffer-substring
			   (point)
			   (progn
			     ;; Jump over asterisk, non-ASCII
			     ;; and non-boundary characters.
			     (while (and c
					 (or (eq c ?*)
					     (> c ?\177)
					     (not (eq (char-syntax c) ? ))))
			       (forward-char 1)
			       (setq c (char-after)))
			     (point)))))
		   (t
		    (error "Invalid header: %s" string)))
		  (push (list attribute value number encoded)
			parameters))))
	  (error
	   (setq parameters nil)
	   (when signal-error
	     (signal (car err) (cdr err)))))

	;; Now collect and concatenate continuation parameters.
	(let ((cparams nil)
	      elem)
	  (loop for (attribute value part encoded)
		in (sort parameters (lambda (e1 e2)
				      (< (or (caddr e1) 0)
					 (or (caddr e2) 0))))
		do (if (or (not (setq elem (assq attribute cparams)))
			   (and (numberp part)
				(zerop part)))
		       (push (list attribute value encoded) cparams)
		     (setcar (cdr elem) (concat (cadr elem) value))))
	  ;; Finally decode encoded values.
	  (cons type (mapcar
		      (lambda (elem)
			(cons (car elem)
			      (if (nth 2 elem)
				  (rfc2231-decode-encoded-string (nth 1 elem))
				(nth 1 elem))))
		      (nreverse cparams))))))))

(defun rfc2231-decode-encoded-string (string)
  "Decode an RFC2231-encoded string.
These look like:
 \"us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A\",
 \"us-ascii''This%20is%20%2A%2A%2Afun%2A%2A%2A\",
 \"'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A\",
 \"''This%20is%20%2A%2A%2Afun%2A%2A%2A\", or
 \"This is ***fun***\"."
  (string-match "\\`\\(?:\\([^']+\\)?'\\([^']+\\)?'\\)?\\(.+\\)" string)
  (let ((coding-system (mm-charset-to-coding-system (match-string 1 string)))
	;;(language (match-string 2 string))
	(value (match-string 3 string)))
    (mm-with-unibyte-buffer
      (insert value)
      (goto-char (point-min))
      (while (re-search-forward "%\\([0-9A-Fa-f][0-9A-Fa-f]\\)" nil t)
	(insert
	 (prog1
	     (string-to-number (match-string 1) 16)
	   (delete-region (match-beginning 0) (match-end 0)))))
      ;; Decode using the charset, if any.
      (if (memq coding-system '(nil ascii))
	  (buffer-string)
	(mm-decode-coding-string (buffer-string) coding-system)))))

(defun rfc2231-encode-string (param value)
  "Return and PARAM=VALUE string encoded according to RFC2231.
Use `mml-insert-parameter' or `mml-insert-parameter-string' to insert
the result of this function."
  (let ((control (ietf-drums-token-to-list ietf-drums-no-ws-ctl-token))
	(tspecial (ietf-drums-token-to-list ietf-drums-tspecials))
	(special (ietf-drums-token-to-list "*'%\n\t"))
	(ascii (ietf-drums-token-to-list ietf-drums-text-token))
	(num -1)
	;; Don't make lines exceeding 76 column.
	(limit (- 74 (length param)))
	spacep encodep charsetp charset broken)
    (mm-with-multibyte-buffer
      (insert value)
      (goto-char (point-min))
      (while (not (eobp))
	(cond
	 ((or (memq (following-char) control)
	      (memq (following-char) tspecial)
	      (memq (following-char) special))
	  (setq encodep t))
	 ((eq (following-char) ? )
	  (setq spacep t))
	 ((not (memq (following-char) ascii))
	  (setq charsetp t)))
	(forward-char 1))
      (when charsetp
	(setq charset (mm-encode-body)))
      (mm-disable-multibyte)
      (cond
       ((or encodep charsetp
	    (progn
	      (end-of-line)
	      (> (current-column) (if spacep (- limit 2) limit))))
	(setq limit (- limit 6))
	(goto-char (point-min))
	(insert (symbol-name (or charset 'us-ascii)) "''")
	(while (not (eobp))
	  (if (or (not (memq (following-char) ascii))
		  (memq (following-char) control)
		  (memq (following-char) tspecial)
		  (memq (following-char) special)
		  (eq (following-char) ? ))
	      (progn
		(when (>= (current-column) (1- limit))
		  (insert ";\n")
		  (setq broken t))
		(insert "%" (format "%02x" (following-char)))
		(delete-char 1))
	    (when (> (current-column) limit)
	      (insert ";\n")
	      (setq broken t))
	    (forward-char 1)))
	(goto-char (point-min))
	(if (not broken)
	    (insert param "*=")
	  (while (not (eobp))
	    (insert (if (>= num 0) " " "")
		    param "*" (format "%d" (incf num)) "*=")
	    (forward-line 1))))
       (spacep
	(goto-char (point-min))
	(insert param "=\"")
	(goto-char (point-max))
	(insert "\""))
       (t
	(goto-char (point-min))
	(insert param "=")))
      (buffer-string))))

(provide 'rfc2231)

;;; rfc2231.el ends here