;;; nndoc.el --- single file access for Gnus  -*- lexical-binding: t; -*-

;; Copyright (C) 1995-2024 Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;;	Masanobu UMEDA <umerin@flab.flab.fujitsu.junet>
;; Keywords: news

;; 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:

;; For Outlook mail boxes format, see https://mbx2mbox.sourceforge.net/

;;; Code:

(require 'nnheader)
(require 'message)
(require 'nnmail)
(require 'nnoo)
(require 'gnus-util)
(require 'mm-util)
(eval-when-compile (require 'cl-lib))

(nnoo-declare nndoc)

(defvoo nndoc-article-type 'guess
  "Type of the file.
One of `mbox', `babyl', `digest', `news', `rnews', `mmdf', `forward',
`rfc934', `rfc822-forward', `mime-parts', `standard-digest',
`slack-digest', `clari-briefs', `nsmail', `outlook', `oe-dbx',
`mailman', `exim-bounce', or `guess'.")

(defvoo nndoc-post-type 'mail
  "Whether the nndoc group is `mail' or `post'.")

(defvoo nndoc-open-document-hook 'nnheader-ms-strip-cr
  "Hook run after opening a document.
The default function removes all trailing carriage returns
from the document.")

(defvar nndoc-type-alist
  `((mmdf
     (article-begin .  "^\^A\^A\^A\^A\n")
     (body-end .  "^\^A\^A\^A\^A\n"))
    (debbugs-db
     (file-begin    . "^\005")
     (article-begin . "^[\005\007]\n")
     (body-end      . "^\003"))
    (mime-digest
     (article-begin . "")
     (head-begin . "^ ?\n")
     (head-end . "^ ?$")
     (body-end . "")
     (file-end . "")
     (subtype digest guess))
    (nsmail
     (article-begin .  "^From - "))
    (news
     (article-begin . "^Path:"))
    (rnews
     (article-begin . "^#! *rnews +\\([0-9]+\\) *\n")
     (body-end-function . nndoc-rnews-body-end))
    (mbox
     (article-begin-function . nndoc-mbox-article-begin)
     (body-end-function . nndoc-mbox-body-end))
    (babyl
     (article-begin . "\^_\^L *\n")
     (body-end . "\^_")
     (body-begin-function . nndoc-babyl-body-begin)
     (head-begin-function . nndoc-babyl-head-begin))
    (mime-parts
     (generate-head-function . nndoc-generate-mime-parts-head)
     (article-transform-function . nndoc-transform-mime-parts))
    (exim-bounce
     (article-begin . "^------ This is a copy of the message, including all the headers. ------\n\n")
     (body-end-function . nndoc-exim-bounce-body-end-function))
    (rfc934
     (article-begin . "^--.*\n+")
     (body-end . "^--.*$")
     (prepare-body-function . nndoc-unquote-dashes))
    (mailman
     (article-begin . "^--__--__--\n\nMessage:")
     (body-end . "^--__--__--$")
     (prepare-body-function . nndoc-unquote-dashes))
    (clari-briefs
     (article-begin . "^ \\*")
     (body-end . "^\t------*[ \t]^*\n^ \\*")
     (body-begin . "^\t")
     (head-end . "^\t")
     (generate-head-function . nndoc-generate-clari-briefs-head)
     (article-transform-function . nndoc-transform-clari-briefs))

    (standard-digest
     (first-article . ,(concat "^" (make-string 70 ?-) "\n *\n+"))
     (article-begin . ,(concat "^\n" (make-string 30 ?-) "\n *\n+"))
     (prepare-body-function . nndoc-unquote-dashes)
     (body-end-function . nndoc-digest-body-end)
     (head-end . "^ *$")
     (body-begin . "^ *\n")
     (file-end . "^End of .*digest.*[0-9].*\n\\*\\*\\|^End of.*Digest *$")
     (subtype digest guess))
    (slack-digest
     (article-begin . "^------------------------------*[\n \t]+")
     (head-end . "^ ?$")
     (body-end-function . nndoc-digest-body-end)
     (body-begin . "^ ?$")
     (file-end . "^End of")
     (prepare-body-function . nndoc-unquote-dashes)
     (subtype digest guess))
    (google
     (pre-dissection-function . nndoc-decode-content-transfer-encoding)
     (article-begin . "^== [0-9]+ of [0-9]+ ==$")
     (head-begin . "^Date:")
     (head-end . "^$")
     (body-end-function . nndoc-digest-body-end)
     (body-begin . "^$")
     (file-end . "^==============================================================================$")
     (prepare-body-function . nndoc-unquote-dashes)
     (subtype digest guess))
    (lanl-gov-announce
     (article-begin . "^\\\\\\\\\n")
     (head-begin . "^\\(Paper.*:\\|arXiv:\\)")
     (head-end   . "\\(^\\\\\\\\.*\n\\|-----------------\\)")
     (body-begin . "")
     (body-end   . "\\(-------------------------------------------------\\|%-%-%-%-%-%-%-%-%-%-%-%-%-%-\\|%%--%%--%%--%%--%%--%%--%%--%%--\\|%%%---%%%---%%%---%%%---\\)")
     (file-end   . "\\(^Title: Recent Seminal\\|%%%---%%%---%%%---%%%---\\)")
     (generate-head-function . nndoc-generate-lanl-gov-head)
     (article-transform-function . nndoc-transform-lanl-gov-announce)
     (subtype preprints guess))
    (git
     (file-begin . "\n- Log ---.*")
     (article-begin . "^commit ")
     (head-begin . "^Author: ")
     (body-begin . "^$")
     (file-end . "\n-----------------------------------------------------------------------")
     (article-transform-function . nndoc-transform-git-article)
     (header-transform-function . nndoc-transform-git-headers))
    (rfc822-forward
     (article-begin . "^\n+")
     (body-end-function . nndoc-rfc822-forward-body-end-function)
     (generate-head-function . nndoc-rfc822-forward-generate-head)
     (generate-article-function . nndoc-rfc822-forward-generate-article))
    (outlook
     (article-begin-function . nndoc-outlook-article-begin)
     (body-end .  "\0"))
    (oe-dbx  ;; Outlook Express DBX format
     (dissection-function . nndoc-oe-dbx-dissection)
     (generate-head-function . nndoc-oe-dbx-generate-head)
     (generate-article-function . nndoc-oe-dbx-generate-article))
    (forward
     (article-begin . "^-+ \\(Start of \\)?forwarded message.*\n+")
     (body-end . "^-+ End \\(of \\)?forwarded message.*$")
     (prepare-body-function . nndoc-unquote-dashes))
    (mail-in-mail ;; Wild guess on mailer daemon's messages or others
     (article-begin-function . nndoc-mail-in-mail-article-begin))
    (guess
     (guess . t)
     (subtype nil))
    (digest
     (guess . t)
     (subtype nil))
    (preprints
     (guess . t)
     (subtype nil))))

(defvar nndoc-binary-file-names ".[Dd][Bb][Xx]$"
  "Regexp for binary nndoc file names.")


(defvoo nndoc-file-begin nil)
(defvoo nndoc-first-article nil)
(defvoo nndoc-article-begin nil)
(defvoo nndoc-head-begin nil)
(defvoo nndoc-head-end nil)
(defvoo nndoc-file-end nil)
(defvoo nndoc-body-begin nil)
(defvoo nndoc-body-end-function nil)
(defvoo nndoc-body-begin-function nil)
(defvoo nndoc-head-begin-function nil)
(defvoo nndoc-body-end nil)
;; nndoc-dissection-alist is a list of sublists.  Each sublist holds the
;; following items.  ARTICLE acts as the association key and is an ordinal
;; starting at 1.  HEAD-BEGIN [0], HEAD-END [1], BODY-BEGIN [2] and BODY-END
;; [3] are positions in the `nndoc' buffer.  LINE-COUNT [4] is a count of
;; lines in the body.  For MIME dissections only, ARTICLE-INSERT [5] and
;; SUMMARY-INSERT [6] give headers to insert for full article or summary line
;; generation, respectively.  Other headers usually follow directly from the
;; buffer.  Value nil means no insert.
(defvoo nndoc-dissection-alist nil)
(defvoo nndoc-prepare-body-function nil)
(defvoo nndoc-generate-head-function nil)
(defvoo nndoc-article-transform-function nil)
(defvoo nndoc-header-transform-function nil)
(defvoo nndoc-article-begin-function nil)
(defvoo nndoc-generate-article-function nil)
(defvoo nndoc-dissection-function nil)
(defvoo nndoc-pre-dissection-function nil)

(defvoo nndoc-status-string "")
(defvoo nndoc-group-alist nil)
(defvoo nndoc-current-buffer nil
  "Current nndoc news buffer.")
(defvoo nndoc-address nil)

(defconst nndoc-version "nndoc 1.0"
  "nndoc version.")
(make-obsolete-variable 'nndoc-version 'emacs-version "29.1")



;;; Interface functions

(nnoo-define-basics nndoc)

(deffoo nndoc-retrieve-headers (articles &optional newsgroup server _fetch-old)
  (when (nndoc-possibly-change-buffer newsgroup server)
    (with-current-buffer nntp-server-buffer
      (erase-buffer)
      (let (article entry)
	(if (stringp (car articles))
	    'headers
	  (while articles
	    (when (setq entry (cdr (assq (setq article (pop articles))
					 nndoc-dissection-alist)))
	      (let ((start (point)))
		(insert (format "221 %d Article retrieved.\n" article))
		(if nndoc-generate-head-function
		    (funcall nndoc-generate-head-function article)
		  (insert-buffer-substring
		   nndoc-current-buffer (car entry) (nth 1 entry)))
		(goto-char (point-max))
		(unless (eq (char-after (1- (point))) ?\n)
		  (insert "\n"))
		(insert (format "Lines: %d\n" (nth 4 entry)))
		(insert ".\n")
		(when nndoc-header-transform-function
		  (save-excursion
		    (save-restriction
		      (narrow-to-region start (point))
		      (funcall nndoc-header-transform-function entry)))))))
	  (nnheader-fold-continuation-lines)
	  'headers)))))

(deffoo nndoc-request-article (article &optional newsgroup server buffer)
  (nndoc-possibly-change-buffer newsgroup server)
  (let ((buffer (or buffer nntp-server-buffer))
        (entry (cdr (assq article nndoc-dissection-alist)))
        beg)
    (with-current-buffer buffer
      (erase-buffer)
      (when entry
	(cond
	 ((stringp article) nil)
	 (nndoc-generate-article-function
	  (funcall nndoc-generate-article-function article))
	 (t
	  (insert-buffer-substring
	   nndoc-current-buffer (car entry) (nth 1 entry))
	  (insert "\n")
	  (setq beg (point))
	  (insert-buffer-substring
	   nndoc-current-buffer (nth 2 entry) (nth 3 entry))
	  (goto-char beg)
	  (when nndoc-prepare-body-function
	    (funcall nndoc-prepare-body-function))
	  (when nndoc-article-transform-function
	    (funcall nndoc-article-transform-function article))
	  t))))))

(deffoo nndoc-request-group (group &optional server dont-check _info)
  "Select news GROUP."
  (let (number)
    (cond
     ((not (nndoc-possibly-change-buffer group server))
      (nnheader-report 'nndoc "No such file or buffer: %s"
		       nndoc-address))
     (dont-check
      (nnheader-report 'nndoc "Selected group %s" group)
      t)
     ((zerop (setq number (length nndoc-dissection-alist)))
      (nndoc-close-group group)
      (nnheader-report 'nndoc "No articles in group %s" group))
     (t
      (nnheader-insert "211 %d %d %d %s\n" number 1 number group)))))

(deffoo nndoc-retrieve-groups (groups &optional server)
  (dolist (group groups)
    (nndoc-request-group group server))
  t)

(deffoo nndoc-request-type (_group &optional article)
  (cond ((not article) 'unknown)
	(nndoc-post-type nndoc-post-type)
	(t 'unknown)))

(deffoo nndoc-close-group (group &optional server)
  (nndoc-possibly-change-buffer group server)
  (and (buffer-live-p nndoc-current-buffer)
       (kill-buffer nndoc-current-buffer))
  (setq nndoc-group-alist (delq (assoc group nndoc-group-alist)
				nndoc-group-alist))
  (setq nndoc-current-buffer nil)
  (nnoo-close-server 'nndoc server)
  (setq nndoc-dissection-alist nil)
  t)

(deffoo nndoc-request-list (&optional _server)
  t)

(deffoo nndoc-request-newgroups (_date &optional _server)
  nil)

(deffoo nndoc-request-list-newsgroups (&optional _server)
  nil)


;;; Internal functions.

(defun nndoc-possibly-change-buffer (group _source)
  (let (buf)
    (cond
     ;; The current buffer is this group's buffer.
     ((and (buffer-live-p nndoc-current-buffer)
	   (eq nndoc-current-buffer
	       (setq buf (cdr (assoc group nndoc-group-alist))))))
     ;; We change buffers by taking an old from the group alist.
     ;; `source' is either a string (a file name) or a buffer object.
     (buf
      (setq nndoc-current-buffer buf))
     ;; It's a totally new group.
     ((or (buffer-live-p nndoc-address)
	  (and (stringp nndoc-address)
	       (file-exists-p nndoc-address)
	       (not (file-directory-p nndoc-address))))
      (push (cons group (setq nndoc-current-buffer
			      (gnus-get-buffer-create
			       (concat " *nndoc " group "*"))))
	    nndoc-group-alist)
      (setq nndoc-dissection-alist nil)
      (with-current-buffer nndoc-current-buffer
	(erase-buffer)
	(set-buffer-multibyte nil)
	(condition-case error
	    (if (and (stringp nndoc-address)
		     (string-match nndoc-binary-file-names nndoc-address))
		(let ((coding-system-for-read 'binary))
		  (mm-insert-file-contents nndoc-address))
	      (if (stringp nndoc-address)
		  (nnheader-insert-file-contents nndoc-address)
		(insert-buffer-substring nndoc-address))
	      (run-hooks 'nndoc-open-document-hook))
	  (file-error
	   (nnheader-report 'nndoc "Couldn't open %s: %s"
			    group error))))))
    ;; Initialize the nndoc structures according to this new document.
    (when (and nndoc-current-buffer
	       (not nndoc-dissection-alist))
      (with-current-buffer nndoc-current-buffer
	(nndoc-set-delims)
	(if (eq nndoc-article-type 'mime-parts)
	    (nndoc-dissect-mime-parts)
	  (nndoc-dissect-buffer))))
    (unless nndoc-current-buffer
      (nndoc-close-server))
    ;; Return whether we managed to select a file.
    nndoc-current-buffer))

;;;
;;; Deciding what document type we have
;;;

(defun nndoc-set-delims ()
  "Set the nndoc delimiter variables according to the type of the document."
  (let ((vars '(nndoc-file-begin
		nndoc-first-article
		nndoc-article-begin-function
		nndoc-head-begin nndoc-head-end
		nndoc-file-end nndoc-article-begin
		nndoc-body-begin nndoc-body-end-function nndoc-body-end
		nndoc-prepare-body-function nndoc-article-transform-function
		nndoc-header-transform-function
		nndoc-generate-head-function nndoc-body-begin-function
		nndoc-head-begin-function
		nndoc-generate-article-function
		nndoc-dissection-function
		nndoc-pre-dissection-function)))
    (while vars
      (set (pop vars) nil)))
  (let (defs)
    ;; Guess away until we find the real file type.
    (while (assq 'guess (setq defs (cdr (assq nndoc-article-type
					      nndoc-type-alist))))
      (setq nndoc-article-type (nndoc-guess-type nndoc-article-type)))
    ;; Set the nndoc variables.
    (while defs
      (set (intern (format "nndoc-%s" (caar defs)))
	   (cdr (pop defs))))))

(defun nndoc-guess-type (subtype)
  (let ((alist nndoc-type-alist)
	results result entry)
    (while (and (not result)
		(setq entry (pop alist)))
      (when (memq subtype (or (cdr (assq 'subtype entry)) '(guess)))
	(goto-char (point-min))
	;; Remove blank lines.
	(while (eq (following-char) ?\n)
	  (delete-char 1))
	(when (numberp (setq result (funcall (intern
					      (format "nndoc-%s-type-p"
						      (car entry))))))
	  (push (cons result entry) results)
	  (setq result nil))))
    (unless (or result results)
      (error "Document is not of any recognized type"))
    (car (if result
	     entry
	   (cdar (last (sort results #'car-less-than-car)))))))

;;;
;;; Built-in type predicates and functions
;;;

(defun nndoc-mbox-type-p ()
  (when (looking-at message-unix-mail-delimiter)
    t))

(defun nndoc-mbox-article-begin ()
  (when (re-search-forward (concat "^" message-unix-mail-delimiter) nil t)
    (goto-char (match-beginning 0))))

(defun nndoc-mbox-body-end ()
  (let ((beg (point))
	len end)
    (when
	(save-excursion
	  (and (re-search-backward
		(concat "^" message-unix-mail-delimiter) nil t)
	       (setq end (point))
	       (search-forward "\n\n" beg t)
	       (re-search-backward
		"^Content-Length:[ \t]*\\([0-9]+\\) *$" end t)
	       (setq len (string-to-number (match-string 1)))
	       (search-forward "\n\n" beg t)
	       (unless (= (setq len (+ (point) len)) (point-max))
		 (and (< len (point-max))
		      (goto-char len)
		      (looking-at message-unix-mail-delimiter)))))
      (goto-char len))))

(defun nndoc-mmdf-type-p ()
  (when (looking-at "\^A\^A\^A\^A$")
    t))

(defun nndoc-debbugs-db-type-p ()
  (when (looking-at "\006$")
    t))

(defun nndoc-news-type-p ()
  (when (looking-at "^Path:.*\n")
    t))

(defun nndoc-rnews-type-p ()
  (when (looking-at "#! *rnews")
    t))

(defun nndoc-rnews-body-end ()
  (and (re-search-backward nndoc-article-begin nil t)
       (forward-line 1)
       (goto-char (+ (point) (string-to-number (match-string 1))))))

(defun nndoc-google-type-p ()
  (when (re-search-forward "^=3D=3D 1 of [0-9]+ =3D=3D$" nil t)
    t))

(defun nndoc-decode-content-transfer-encoding ()
  (let ((encoding
	 (save-restriction
	   (message-narrow-to-head)
	   (message-fetch-field "content-transfer-encoding"))))
    (when (and encoding
	       (search-forward "\n\n" nil t))
      (save-restriction
	(narrow-to-region (point) (point-max))
	(mm-decode-content-transfer-encoding
	 (intern (downcase (mail-header-strip-cte encoding))))))))

(defun nndoc-babyl-type-p ()
  (when (re-search-forward "\^_\^L *\n" nil t)
    t))

(defun nndoc-babyl-body-begin ()
  (re-search-forward "^\n" nil t)
  (when (looking-at "\\*\\*\\* EOOH \\*\\*\\*")
    (let ((next (or (save-excursion
		      (re-search-forward nndoc-article-begin nil t))
		    (point-max))))
      (unless (re-search-forward "^\n" next t)
	(goto-char next)
	(forward-line -1)
	(insert "\n")
	(forward-line -1)))))

(defun nndoc-babyl-head-begin ()
  (when (re-search-forward "^[0-9].*\n" nil t)
    (when (looking-at "\\*\\*\\* EOOH \\*\\*\\*")
      (forward-line 1))
    t))

(defun nndoc-forward-type-p ()
  (when (and (re-search-forward "^-+ \\(Start of \\)?forwarded message.*\n+"
				nil t)
	     (looking-at "[\r\n]*[a-zA-Z][a-zA-Z0-9-]*:\\|^>?From "))
    t))

(defun nndoc-rfc934-type-p ()
  (when (and (re-search-forward "^-+ Start of forwarded.*\n+" nil t)
	     (not (re-search-forward "^Subject:.*digest" nil t))
	     (not (re-search-backward "^From:" nil t 2))
	     (not (re-search-forward "^From:" nil t 2)))
    t))

(defun nndoc-mailman-type-p ()
  (when (re-search-forward "^--__--__--\n+" nil t)
    t))

(defun nndoc-rfc822-forward-type-p ()
  (save-restriction
    (message-narrow-to-head)
    (when (re-search-forward "^Content-Type: *message/rfc822" nil t)
      t)))

(defun nndoc-rfc822-forward-body-end-function ()
  (goto-char (point-max)))

(defun nndoc-rfc822-forward-generate-article (article &optional head)
  (let ((entry (cdr (assq article nndoc-dissection-alist)))
	(begin (point))
	encoding)
    (with-current-buffer nndoc-current-buffer
      (save-restriction
	(message-narrow-to-head)
	(setq encoding (message-fetch-field "content-transfer-encoding"))))
    (insert-buffer-substring nndoc-current-buffer (car entry) (nth 3 entry))
    (when encoding
      (save-restriction
	(narrow-to-region begin (point-max))
	(mm-decode-content-transfer-encoding
	 (intern (downcase (mail-header-strip-cte encoding))))))
    (when head
      (goto-char begin)
      (when (search-forward "\n\n" nil t)
	(delete-region (1- (point)) (point-max)))))
  t)

(defun nndoc-rfc822-forward-generate-head (article)
  (nndoc-rfc822-forward-generate-article article 'head))

(defun nndoc-mime-parts-type-p ()
  (let ((case-fold-search t)
	(limit (search-forward "\n\n" nil t)))
    (goto-char (point-min))
    (when (and limit
	       (re-search-forward
		(concat "\
^Content-Type:[ \t]*multipart/[a-z]+ *; *\\(\\(\n[ \t]\\)?.*;\\)*"
			"\\(\n[ \t]\\)?[ \t]*boundary=\"?[^\"\n]*[^\" \t\n]")
		limit t))
      t)))

(defun nndoc-transform-mime-parts (article)
  (let* ((entry (cdr (assq article nndoc-dissection-alist)))
	 (headers (nth 5 entry)))
    (when headers
      (goto-char (point-min))
      (insert headers))))

(defun nndoc-generate-mime-parts-head (article)
  (let* ((entry (cdr (assq article nndoc-dissection-alist)))
	 (headers (nth 6 entry)))
    (save-restriction
      (narrow-to-region (point) (point))
      (insert-buffer-substring
       nndoc-current-buffer (car entry) (nth 1 entry))
      (goto-char (point-max)))
    (when headers
      (insert headers))))

(defun nndoc-clari-briefs-type-p ()
  (when (let ((case-fold-search nil))
	  (re-search-forward "^\t[^a-z]+ ([^a-z]+) --" nil t))
    t))

(defun nndoc-transform-clari-briefs (article)
  (goto-char (point-min))
  (when (looking-at " *\\*\\(.*\\)\n")
    (replace-match "" t t))
  (nndoc-generate-clari-briefs-head article))

(defun nndoc-generate-clari-briefs-head (article)
  (let ((entry (cdr (assq article nndoc-dissection-alist)))
	subject from)
    (with-current-buffer nndoc-current-buffer
      (save-restriction
	(narrow-to-region (car entry) (nth 3 entry))
	(goto-char (point-min))
	(when (looking-at " *\\*\\(.*\\)$")
	  (setq subject (match-string 1))
	  (when (string-match "[ \t]+$" subject)
	    (setq subject (substring subject 0 (match-beginning 0)))))
	(when
	    (let ((case-fold-search nil))
	      (re-search-forward
	       "^\t\\([^a-z]+\\(,[^(]+\\)? ([^a-z]+)\\) --" nil t))
	  (setq from (match-string 1)))))
    (insert "From: " "clari@clari.net (" (or from "unknown") ")"
	    "\nSubject: " (or subject "(no subject)") "\n")))

(defun nndoc-exim-bounce-type-p ()
  (and (re-search-forward "^------ This is a copy of the message, including all the headers. ------" nil t)
       t))

(defun nndoc-exim-bounce-body-end-function ()
  (goto-char (point-max)))


(defun nndoc-mime-digest-type-p ()
  (let ((case-fold-search t)
	boundary-id b-delimiter entry)
    (when (and
	   (re-search-forward
	    (concat "^Content-Type: *multipart/digest;[ \t\n]*[ \t]"
		    "boundary=\"?\\([^\"\n]*[^\" \t\n]\\)")
	    nil t)
	   (match-beginning 1))
      (setq boundary-id (match-string 1)
	    b-delimiter (concat "\n--" boundary-id "[ \t]*$"))
      (setq entry (assq 'mime-digest nndoc-type-alist))
      (setcdr entry
	      (list
	       (cons 'head-begin "^ ?\n")
	       (cons 'head-end "^ ?$")
	       (cons 'body-begin "^ ?\n")
	       (cons 'article-begin b-delimiter)
	       (cons 'body-end-function 'nndoc-digest-body-end)
	       (cons 'file-end (concat "^--" boundary-id "--[ \t]*$"))))
      t)))

(defun nndoc-standard-digest-type-p ()
  (when (and (re-search-forward (concat "^" (make-string 70 ?-) "\n\n") nil t)
	     (re-search-forward
	      (concat "\n\n" (make-string 30 ?-) "\n\n") nil t))
    t))

(defun nndoc-digest-body-end ()
  (and (re-search-forward nndoc-article-begin nil t)
       (goto-char (match-beginning 0))))

(defun nndoc-slack-digest-type-p ()
  0)

(defun nndoc-git-type-p ()
  (and (search-forward "\n- Log ---" nil t)
       (search-forward "\ncommit " nil t)
       (search-forward "\nAuthor: " nil t)))

(defun nndoc-transform-git-article (_article)
  (goto-char (point-min))
  (when (re-search-forward "^Author: " nil t)
    (replace-match "From: " t t)))

(defun nndoc-transform-git-headers (entry)
  (goto-char (point-min))
  (when (re-search-forward "^Author: " nil t)
    (replace-match "From: " t t))
  (let (subject)
    (with-current-buffer nndoc-current-buffer
      (goto-char (car entry))
      (when (search-forward "\n\n" nil t)
	(setq subject (buffer-substring (point) (line-end-position)))))
    (when subject
      (goto-char (point-min))
      (forward-line 1)
      (insert (format "Subject: %s\n" subject)))))

(defun nndoc-lanl-gov-announce-type-p ()
  (when (let ((case-fold-search nil))
	  (re-search-forward "^\\\\\\\\\n\\(Paper\\( (\\*cross-listing\\*)\\)?: [a-zA-Z\\.-]+/[0-9]+\\|arXiv:\\)" nil t))
    t))

(defun nndoc-transform-lanl-gov-announce (_article)
  (let ((case-fold-search nil))
    (goto-char (point-max))
    (when (re-search-backward "^\\\\\\\\ +( *\\([^ ]*\\) , *\\([^ ]*\\))" nil t)
      (replace-match "\n\nGet it at \\1 (\\2)" t nil))
    (goto-char (point-min))
    (while (re-search-forward "^\\\\\\\\$" nil t)
      (replace-match "" t nil))
    (goto-char (point-min))
    (when (re-search-forward "^replaced with revised version +\\(.*[^ ]\\) +" nil t)
      (replace-match "Date: \\1 (revised) " t nil))
    (goto-char (point-min))
    (unless (re-search-forward "^From" nil t)
      (goto-char (point-min))
      (when (re-search-forward "^Authors?: \\(.*\\)" nil t)
	(goto-char (point-min))
	(insert "From: " (match-string 1) "\n")))
    (when (re-search-forward "^arXiv:" nil t)
      (replace-match "Paper: arXiv:" t nil))))

(defun nndoc-generate-lanl-gov-head (article)
  (let ((entry (cdr (assq article nndoc-dissection-alist)))
	(from "<no address given>")
	subject date)
    (with-current-buffer nndoc-current-buffer
      (save-restriction
	(narrow-to-region (car entry) (nth 1 entry))
	(goto-char (point-min))
	(when (looking-at "^\\(Paper.*: \\|arXiv:\\)\\([0-9a-zA-Z\\./-]+\\)")
	  (setq subject (concat " (" (match-string 2) ")"))
	  (when (re-search-forward "^From: \\(.*\\)" nil t)
	    (setq from (concat "<"
			       (cadr (funcall gnus-extract-address-components
					      (match-string 1))) ">")))
	  (if (re-search-forward "^Date: +\\([^(]*\\)" nil t)
	      (setq date (match-string 1))
	    (when (re-search-forward "^replaced with revised version +\\([^(]*\\)" nil t)
	      (setq date (match-string 1))))
	  (when (re-search-forward "^Title: \\([^\f]*\\)\nAuthors?: \\(.*\\)"
				   nil t)
	    (setq subject (concat (match-string 1) subject))
	    (setq from (concat (match-string 2) " " from))))))
    (while (and from (string-match "([^)]*)" from))
      (setq from (replace-match "" t t from)))
    (insert "From: "  (or from "unknown")
	    "\nSubject: " (or subject "(no subject)") "\n")
    (if date (insert "Date: " date))))

(defun nndoc-nsmail-type-p ()
  (when (looking-at "From - ")
    t))

(defun nndoc-outlook-article-begin ()
  (prog1 (re-search-forward "From:\\|Received:" nil t)
    (goto-char (match-beginning 0))))

(defun nndoc-outlook-type-p ()
  ;; FIXME: Is JMF the magic of outlook mailbox? -- ShengHuo.
  (looking-at "JMF"))

(defun nndoc-oe-dbx-type-p ()
  (looking-at "\317\255\022\376"))

(defun nndoc-read-little-endian ()
  (+ (prog1 (char-after) (forward-char 1))
     (ash (prog1 (char-after) (forward-char 1)) 8)
     (ash (prog1 (char-after) (forward-char 1)) 16)
     (ash (prog1 (char-after) (forward-char 1)) 24)))

(defun nndoc-oe-dbx-decode-block ()
  (list
   (nndoc-read-little-endian)   ;; this address
   (nndoc-read-little-endian)   ;; next address offset
   (nndoc-read-little-endian)   ;; blocksize
   (nndoc-read-little-endian))) ;; next address

(defun nndoc-oe-dbx-dissection ()
  (let ((i 0) blk p tp)
    (goto-char 60117) ;; 0x0000EAD4+1
    (setq p (point))
    (unless (eobp)
      (setq blk (nndoc-oe-dbx-decode-block)))
    (while (and blk (> (car blk) 0) (or (zerop (nth 3 blk))
					(> (nth 3 blk) p)))
      (push (list (cl-incf i) p nil nil nil 0) nndoc-dissection-alist)
      (while (and (> (car blk) 0) (> (nth 3 blk) p))
	(goto-char (1+ (nth 3 blk)))
	(setq blk (nndoc-oe-dbx-decode-block)))
      (if (or (<= (car blk) p)
	      (<= (nth 1 blk) 0)
	      (not (zerop (nth 3 blk))))
	  (setq blk nil)
	(setq tp (+ (car blk) (nth 1 blk) 17))
	(if (or (<= tp p) (>= tp (point-max)))
	    (setq blk nil)
	  (goto-char tp)
	  (setq p tp
		blk (nndoc-oe-dbx-decode-block)))))))

(defun nndoc-oe-dbx-generate-article (article &optional head)
  (let ((entry (cdr (assq article nndoc-dissection-alist)))
	(cur (current-buffer))
	(begin (point))
	blk p)
    (with-current-buffer nndoc-current-buffer
      (setq p (car entry))
      (while (> p (point-min))
	(goto-char p)
	(setq blk (nndoc-oe-dbx-decode-block))
	(setq p (point))
	(with-current-buffer cur
	  (insert-buffer-substring nndoc-current-buffer p (+ p (nth 2 blk))))
	(setq p (1+ (nth 3 blk)))))
    (goto-char begin)
    (while (re-search-forward "\r$" nil t)
      (delete-char -1))
    (when head
      (goto-char begin)
      (when (search-forward "\n\n" nil t)
	(setcar (cddddr entry) (count-lines (point) (point-max)))
	(delete-region (1- (point)) (point-max))))
    t))

(defun nndoc-oe-dbx-generate-head (article)
  (nndoc-oe-dbx-generate-article article 'head))

(defun nndoc-mail-in-mail-type-p ()
  (let (found)
    (save-excursion
      (catch 'done
	(while (re-search-forward "\n\n[-A-Za-z0-9]+:" nil t)
	  (setq found 0)
	  (forward-line)
	  (while (looking-at "[ \t]\\|[-A-Za-z0-9]+:")
	    (if (looking-at "[-A-Za-z0-9]+:")
		(setq found (1+ found)))
	    (forward-line))
	  (if (and (> found 0) (looking-at "\n"))
	      (throw 'done 9999)))
	nil))))

(defun nndoc-mail-in-mail-article-begin ()
  (let (point found)
    (if (catch 'done
	  (while (re-search-forward "\n\n\\([-A-Za-z0-9]+:\\)" nil t)
	    (setq found 0)
	    (setq point (match-beginning 1))
	    (forward-line)
	    (while (looking-at "[ \t]\\|[-A-Za-z0-9]+:")
	      (if (looking-at "[-A-Za-z0-9]+:")
		  (setq found (1+ found)))
	      (forward-line))
	    (if (and (> found 0) (looking-at "\n"))
		(throw 'done t)))
	  nil)
	(goto-char point))))

(deffoo nndoc-request-accept-article (_group &optional _server _last)
  nil)

;;;
;;; Functions for dissecting the documents
;;;

(defun nndoc-search (regexp)
  (prog1
      (re-search-forward regexp nil t)
    (beginning-of-line)))

(defun nndoc-dissect-buffer ()
  "Go through the document and partition it into heads/bodies/articles."
  (let ((i 0)
	(first t)
	art-begin head-begin head-end body-begin body-end)
    (setq nndoc-dissection-alist nil)
    (with-current-buffer nndoc-current-buffer
      (goto-char (point-min))
      ;; Remove blank lines.
      (while (eq (following-char) ?\n)
	(delete-char 1))
      (when nndoc-pre-dissection-function
	(save-excursion
	  (funcall nndoc-pre-dissection-function)))
      (if nndoc-dissection-function
	  (funcall nndoc-dissection-function)
	;; Find the beginning of the file.
	(when nndoc-file-begin
	  (nndoc-search nndoc-file-begin))
	;; Go through the file.
	(while (if (and first nndoc-first-article)
		   (nndoc-search nndoc-first-article)
		 (if art-begin
		     (goto-char art-begin)
		   (nndoc-article-begin)))
	  (setq first nil
		art-begin nil)
	  (cond (nndoc-head-begin-function
		 (funcall nndoc-head-begin-function))
		(nndoc-head-begin
		 (nndoc-search nndoc-head-begin)))
	  (if (or (eobp)
		  (and nndoc-file-end
		       (looking-at nndoc-file-end)))
	      (goto-char (point-max))
	    (setq head-begin (point))
	    (nndoc-search (or nndoc-head-end "^$"))
	    (setq head-end (point))
	    (if nndoc-body-begin-function
		(funcall nndoc-body-begin-function)
	      (nndoc-search (or nndoc-body-begin "^\n")))
	    (setq body-begin (point))
	    (or (and nndoc-body-end-function
		     (funcall nndoc-body-end-function))
		(and nndoc-body-end
		     (nndoc-search nndoc-body-end))
		(and (nndoc-article-begin)
		     (setq art-begin (point)))
		(progn
		  (goto-char (point-max))
		  (when nndoc-file-end
		    (and (re-search-backward nndoc-file-end nil t)
			 (beginning-of-line)))))
	    (setq body-end (point))
	    (push (list (cl-incf i) head-begin head-end body-begin body-end
			(count-lines body-begin body-end))
		  nndoc-dissection-alist)))))
    (setq nndoc-dissection-alist (nreverse nndoc-dissection-alist))))

(defun nndoc-article-begin ()
  (if nndoc-article-begin-function
      (funcall nndoc-article-begin-function)
    (ignore-errors
      (nndoc-search nndoc-article-begin))))

(defun nndoc-unquote-dashes ()
  "Unquote quoted non-separators in digests."
  (while (re-search-forward "^- -"nil t)
    (replace-match "-" t t)))

;; Against compiler warnings.
(defvar nndoc-mime-split-ordinal)

(defun nndoc-dissect-mime-parts ()
  "Go through a MIME composite article and partition it into sub-articles.
When a MIME entity contains sub-entities, dissection produces one article for
the header of this entity, and one article per sub-entity."
  (setq nndoc-dissection-alist nil
	nndoc-mime-split-ordinal 0)
  (with-current-buffer nndoc-current-buffer
    (nndoc-dissect-mime-parts-sub (point-min) (point-max) nil nil nil)))

(defun nndoc-dissect-mime-parts-sub (head-begin body-end article-insert
						position parent)
  "Dissect an entity, within a composite MIME message.
The complete message or MIME entity extends from HEAD-BEGIN to BODY-END.
ARTICLE-INSERT should be added at beginning for generating a full article.
The string POSITION holds a dotted decimal representation of the article
position in the hierarchical structure, it is nil for the outer entity.
PARENT is the message-ID of the parent summary line, or nil for none."
  (let ((case-fold-search t)
	(message-id (nnmail-message-id))
	head-end body-begin summary-insert message-rfc822 multipart-any
	subject content-type type subtype boundary-regexp)
    ;; Gracefully handle a missing body.
    (goto-char head-begin)
    (if (or (and (eq (char-after) ?\n) (or (forward-char 1) t))
	    (search-forward "\n\n" body-end t))
	(setq head-end (1- (point))
	      body-begin (point))
      (setq head-end body-end
	    body-begin body-end))
    (narrow-to-region head-begin head-end)
    ;; Save MIME attributes.
    (goto-char head-begin)
    (setq content-type (message-fetch-field "Content-Type"))
    (when content-type
      (when (string-match
	     "^ *\\([^ \t\n/;]+\\)/\\([^ \t\n/;]+\\)" content-type)
	(setq type (downcase (match-string 1 content-type))
	      subtype (downcase (match-string 2 content-type))
	      message-rfc822 (and (string= type "message")
				  (string= subtype "rfc822"))
	      multipart-any (string= type "multipart")))
      (when (string-match ";[ \t\n]*name=\\([^ \t\n;]+\\)" content-type)
	(setq subject (match-string 1 content-type)))
      (when (string-match "boundary=\"?\\([^\"\n]*[^\" \t\n]\\)" content-type)
	(setq boundary-regexp (concat "^--"
				      (regexp-quote
				       (match-string 1 content-type))
				      "\\(--\\)?[ \t]*\n"))))
    (unless subject
      (when (or multipart-any (not article-insert))
	(setq subject (message-fetch-field "Subject"))))
    (unless type
      (setq type "text"
	    subtype "plain"))
    ;; Prepare the article and summary inserts.
    (unless article-insert
      (setq article-insert (buffer-string)
	    head-end head-begin))
    ;; Fix MIME-Version
    (unless (string-match "MIME-Version:" article-insert)
      (setq article-insert
	    (concat article-insert "MIME-Version: 1.0\n")))
    (setq summary-insert article-insert)
    ;; - summary Subject.
    (setq summary-insert
	  (let ((line (concat "Subject: <" position
			      (and position multipart-any ".")
			      (and multipart-any "*")
			      (and (or position multipart-any) " ")
			      (cond ((string= subtype "plain") type)
				    ((string= subtype "basic") type)
				    (t subtype))
			      ">"
			      (and subject " ")
			      subject
			      "\n")))
	    (if (string-match "Subject:.*\n\\([ \t].*\n\\)*" summary-insert)
		(replace-match line t t summary-insert)
	      (concat summary-insert line))))
    ;; - summary Message-ID.
    (setq summary-insert
	  (let ((line (concat "Message-ID: " message-id "\n")))
	    (if (string-match "Message-ID:.*\n\\([ \t].*\n\\)*" summary-insert)
		(replace-match line t t summary-insert)
	      (concat summary-insert line))))
    ;; - summary References.
    (when parent
      (setq summary-insert
	    (let ((line (concat "References: " parent "\n")))
	      (if (string-match "References:.*\n\\([ \t].*\n\\)*"
				summary-insert)
		  (replace-match line t t summary-insert)
		(concat summary-insert line)))))
    ;; Generate dissection information for this entity.
    (push (list (cl-incf nndoc-mime-split-ordinal)
		head-begin head-end body-begin body-end
		(count-lines body-begin body-end)
		article-insert summary-insert)
	  nndoc-dissection-alist)
    ;; Recurse for all sub-entities, if any.
    (widen)
    (cond
     (message-rfc822
      (save-excursion
	(nndoc-dissect-mime-parts-sub body-begin body-end nil
				      position message-id)))
     ((and multipart-any boundary-regexp)
      (let ((part-counter 0)
	    part-begin part-end eof-flag)
	(while (string-match "\
^\\(Lines\\|Content-\\(Type\\|Transfer-Encoding\\|Disposition\\)\\):.*\n\\([ \t].*\n\\)*"
			     article-insert)
	  (setq article-insert (replace-match "" t t article-insert)))
	(let ((case-fold-search nil))
	  (goto-char body-begin)
	  (setq eof-flag (not (re-search-forward boundary-regexp body-end t)))
	  (while (not eof-flag)
	    (setq part-begin (point))
	    (cond ((re-search-forward boundary-regexp body-end t)
		   (or (not (match-string 1))
		       (string= (match-string 1) "")
		       (setq eof-flag t))
		   (forward-line -1)
		   (setq part-end (point))
		   (forward-line 1))
		  (t (setq part-end body-end
			   eof-flag t)))
	    (save-excursion
	      (nndoc-dissect-mime-parts-sub
	       part-begin part-end article-insert
	       (concat position
		       (and position ".")
		       (format "%d" (cl-incf part-counter)))
	       message-id)))))))))

;;;###autoload
(defun nndoc-add-type (definition &optional position)
  "Add document DEFINITION to the list of nndoc document definitions.
If POSITION is nil or `last', the definition will be added
as the last checked definition, if t or `first', add as the
first definition, and if any other symbol, add after that
symbol in the alist."
  ;; First remove any old instances.
  (gnus-alist-pull (car definition) nndoc-type-alist)
  ;; Then enter the new definition in the proper place.
  (cond
   ((or (null position) (eq position 'last))
    (setq nndoc-type-alist (nconc nndoc-type-alist (list definition))))
   ((or (eq position t) (eq position 'first))
    (push definition nndoc-type-alist))
   (t
    (let ((list (memq (assq position nndoc-type-alist)
		      nndoc-type-alist)))
      (unless list
	(error "No such position: %s" position))
      (setcdr list (cons definition (cdr list)))))))

(provide 'nndoc)

;;; nndoc.el ends here
