;;; elmo-nntp.el --- NNTP Interface for ELMO.  -*- lexical-binding: t -*-

;; Copyright (C) 1998,1999,2000 Yuuichi Teranishi <teranisi@gohome.org>
;; Copyright (C) 1998,1999,2000 Masahiro MURATA <muse@ba2.so-net.ne.jp>
;; Copyright (C) 1999,2000      Kenichi OKADA <okada@opaopa.org>

;; Author: Yuuichi Teranishi <teranisi@gohome.org>
;;	Masahiro MURATA <muse@ba2.so-net.ne.jp>
;;	Kenichi OKADA <okada@opaopa.org>
;; Keywords: mail, net news

;; This file is part of ELMO (Elisp Library for Message Orchestration).

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

;;; Commentary:
;;

;;; Code:
;;
(require 'cl-lib)

(require 'elmo-vars)
(require 'elmo-util)
(require 'elmo-date)
(require 'elmo-msgdb)
(require 'elmo-cache)
(require 'elmo)
(require 'elmo-net)

(defvar elmo-nntp-overview-fetch-chop-length 200
 "*Number of overviews to fetch in one request in nntp.")

(defvar elmo-nntp-use-cache t
  "Use cache in nntp folder.")

(defvar elmo-nntp-max-number-precedes-list-active nil
  "Non-nil means max number of msgdb is set as the max number of `list active'.
(Needed for inn 2.3 or later?).")

(defvar elmo-nntp-group-coding-system nil
  "A coding system for newsgroup string.")

(defconst elmo-nntp-folder-name-syntax `(group
					 (?: [user "^\\([A-Za-z]\\|$\\)"])
					 ,@elmo-net-folder-name-syntax))

(defsubst elmo-nntp-encode-group-string (string)
  (if elmo-nntp-group-coding-system
      (encode-coding-string string elmo-nntp-group-coding-system)
    string))

(defsubst elmo-nntp-decode-group-string (string)
  (if elmo-nntp-group-coding-system
      (decode-coding-string string elmo-nntp-group-coding-system)
    string))

;; For debugging.
(defvar elmo-nntp-debug nil
  "Non-nil forces NNTP folder as debug mode.
Debug information is inserted in the buffer \"*NNTP DEBUG*\"")

;;; Debug
(defsubst elmo-nntp-debug (message &rest args)
  (if elmo-nntp-debug
      (let ((biff (string-match "BIFF-" (buffer-name))))
	(with-current-buffer (get-buffer-create (concat "*NNTP DEBUG*"
							(if biff "BIFF")))
	  (goto-char (point-max))
	  (insert (apply 'format message args) "\n")))))

;;; ELMO NNTP folder
(eval-and-compile
  (luna-define-class elmo-nntp-folder (elmo-net-folder)
		     (group temp-crosses reads))
  (luna-define-internal-accessors 'elmo-nntp-folder))

(luna-define-method elmo-folder-initialize ((folder elmo-nntp-folder) name)
  (let ((elmo-network-stream-type-alist
	 (if elmo-nntp-stream-type-alist
	     (append elmo-nntp-stream-type-alist
		     elmo-network-stream-type-alist)
	   elmo-network-stream-type-alist))
	tokens)
    (setq tokens (car (elmo-parse-separated-tokens
		       name
		       elmo-nntp-folder-name-syntax)))
    ;; group
    (elmo-nntp-folder-set-group-internal folder
					 (elmo-nntp-encode-group-string
					  (cdr (assq 'group tokens))))
    ;; user
    (elmo-net-folder-set-user-internal folder
				       (let ((user (cdr (assq 'user tokens))))
					 (if user
					     (and (> (length user) 0) user)
					   elmo-nntp-default-user)))
    ;; network
    (elmo-net-folder-set-parameters
     folder
     tokens
     (list :server	elmo-nntp-default-server
	   :port	elmo-nntp-default-port
	   :stream-type
	   (elmo-get-network-stream-type elmo-nntp-default-stream-type)))
    folder))

(luna-define-method elmo-folder-expand-msgdb-path ((folder elmo-nntp-folder))
  (convert-standard-filename
   (expand-file-name
    (elmo-nntp-folder-group-internal folder)
    (expand-file-name (or (elmo-net-folder-server-internal folder) "nowhere")
		      (expand-file-name "nntp"
					elmo-msgdb-directory)))))

(luna-define-method elmo-folder-newsgroups ((folder elmo-nntp-folder))
  (list (elmo-nntp-folder-group-internal folder)))

;;; NNTP Session
(eval-and-compile
  (luna-define-class elmo-nntp-session (elmo-network-session)
		     (current-group))
  (luna-define-internal-accessors 'elmo-nntp-session))

;;
;; internal variables
;;

(defvar elmo-nntp-connection-cache nil
  "Cache of NNTP connection.")
;; buffer local variable

(defvar elmo-nntp-list-folders-use-cache 600
  "*Time to cache of list folders, as the number of seconds.
Don't cache if nil.")

(defvar elmo-nntp-list-folders-cache nil)

(defvar elmo-nntp-groups-async nil)
(defvar elmo-nntp-header-fetch-chop-length 200)

(defvar elmo-nntp-read-point 0)

(defvar elmo-nntp-send-mode-reader t)

(defvar elmo-nntp-opened-hook nil)

(defvar elmo-nntp-get-folders-securely nil)

(defvar elmo-nntp-default-use-xover t)

(defvar elmo-nntp-default-use-listgroup t)

(defvar elmo-nntp-default-use-list-active t)

(defvar elmo-nntp-default-use-xhdr t)

(defvar elmo-nntp-server-command-alist nil)


(defconst elmo-nntp-server-command-index '((xover . 0)
					   (listgroup . 1)
					   (list-active . 2)
					   (xhdr . 3)))

(defmacro elmo-nntp-get-server-command (session)
  `(assoc (cons (elmo-network-session-server-internal ,session)
		(elmo-network-session-port-internal ,session))
	  elmo-nntp-server-command-alist))

(defmacro elmo-nntp-set-server-command (session com value)
  `(let (entry)
     (unless (setq entry (cdr (elmo-nntp-get-server-command
			       ,session)))
       (setq elmo-nntp-server-command-alist
	     (nconc elmo-nntp-server-command-alist
		    (list (cons
			   (cons
			    (elmo-network-session-server-internal ,session)
			    (elmo-network-session-port-internal ,session))
			   (setq entry
				 (vector
				  elmo-nntp-default-use-xover
				  elmo-nntp-default-use-listgroup
				  elmo-nntp-default-use-list-active
				  elmo-nntp-default-use-xhdr)))))))
     (aset entry
	   (cdr (assq ,com elmo-nntp-server-command-index))
	   ,value)))

(defmacro elmo-nntp-xover-p (session)
  `(let ((entry (elmo-nntp-get-server-command ,session)))
     (if entry
	 (aref (cdr entry)
	       (cdr (assq 'xover elmo-nntp-server-command-index)))
       elmo-nntp-default-use-xover)))

(defmacro elmo-nntp-set-xover (session value)
  `(elmo-nntp-set-server-command ,session 'xover ,value))

(defmacro elmo-nntp-listgroup-p (session)
  `(let ((entry (elmo-nntp-get-server-command ,session)))
     (if entry
	 (aref (cdr entry)
	       (cdr (assq 'listgroup elmo-nntp-server-command-index)))
       elmo-nntp-default-use-listgroup)))

(defmacro elmo-nntp-set-listgroup (session value)
  `(elmo-nntp-set-server-command ,session 'listgroup ,value))

(defmacro elmo-nntp-list-active-p (session)
  `(let ((entry (elmo-nntp-get-server-command ,session)))
     (if entry
	 (aref (cdr entry)
	       (cdr (assq 'list-active elmo-nntp-server-command-index)))
       elmo-nntp-default-use-list-active)))

(defmacro elmo-nntp-set-list-active (session value)
  `(elmo-nntp-set-server-command ,session 'list-active ,value))

(defmacro elmo-nntp-xhdr-p (session)
  `(let ((entry (elmo-nntp-get-server-command ,session)))
     (if entry
	 (aref (cdr entry)
	       (cdr (assq 'xhdr elmo-nntp-server-command-index)))
       elmo-nntp-default-use-xhdr)))

(defmacro elmo-nntp-set-xhdr (session value)
  `(elmo-nntp-set-server-command ,session 'xhdr ,value))

(defsubst elmo-nntp-max-number-precedes-list-active-p ()
  elmo-nntp-max-number-precedes-list-active)

(defsubst elmo-nntp-folder-postfix (user server port type)
  (concat
   (and user (concat ":" user))
   (if (and server
	    (null (string= server elmo-nntp-default-server)))
       (concat "@" server))
   (if (and port
	    (null (eq port elmo-nntp-default-port)))
       (concat ":" (if (numberp port)
		       (number-to-string port) port)))
   (unless (eq (elmo-network-stream-type-symbol type)
	       elmo-nntp-default-stream-type)
     (elmo-network-stream-type-spec-string type))))

(defun elmo-nntp-get-session (folder &optional if-exists)
  (elmo-network-get-session
   'elmo-nntp-session
   (concat
    (if (elmo-folder-biff-internal folder)
	"BIFF-")
    "NNTP")
   folder
   if-exists))

(luna-define-method elmo-network-initialize-session ((session
						      elmo-nntp-session))
  (let ((process (elmo-network-session-process-internal session))
	response)
    (set-process-filter (elmo-network-session-process-internal session)
			'elmo-nntp-process-filter)
    (with-current-buffer (elmo-network-session-buffer session)
      (setq elmo-nntp-read-point (point-min))
      ;; Skip garbage output from process before greeting.
      (while (and (memq (process-status process) '(open run))
		  (goto-char (point-max))
		  (forward-line -1)
		  (not (looking-at "^[2-5][0-9][0-9]")))
	(accept-process-output process 1))
      (setq elmo-nntp-read-point (point))
      (setq response (elmo-nntp-read-response session t t))
      (unless (car response)
	  (signal 'elmo-open-error (list (cdr response))))
      (if elmo-nntp-send-mode-reader
	  (elmo-nntp-send-mode-reader session))
      (when (memq (elmo-network-stream-type-symbol
		   (elmo-network-session-stream-type-internal session))
		  elmo-network-starttls-stream-type-list)
	(elmo-nntp-send-command session "starttls")
	(or (elmo-nntp-read-response session)
	    (error "Cannot open starttls session"))
	(elmo-network-session-starttls-negotiate session)))))

(luna-define-method elmo-network-authenticate-session ((session
							elmo-nntp-session))
  (with-current-buffer (elmo-network-session-buffer session)
    (when (elmo-network-session-user-internal session)
      (elmo-nntp-send-command session
			      (format "authinfo user %s"
				      (elmo-network-session-user-internal
				       session))
			      nil
			      'no-log)
      (or (elmo-nntp-read-response session)
	  (signal 'elmo-authenticate-error '(authinfo)))
      (elmo-nntp-send-command
       session
       (format "authinfo pass %s"
	       (elmo-get-passwd (elmo-network-session-password-key session)))
       nil
       'no-log)
      (or (elmo-nntp-read-response session)
	  (signal 'elmo-authenticate-error '(authinfo))))))

(luna-define-method elmo-network-setup-session ((_session
						 elmo-nntp-session))
  (run-hooks 'elmo-nntp-opened-hook))

(defun elmo-nntp-process-filter (process output)
  (when (buffer-live-p (process-buffer process))
    (with-current-buffer (process-buffer process)
      (goto-char (point-max))
      (insert output)
      (elmo-nntp-debug "RECEIVED: %s\n" output))))

(defun elmo-nntp-send-mode-reader (session)
  (elmo-nntp-send-command session "mode reader")
  (if (null (elmo-nntp-read-response session t))
      (message "Mode reader failed")))

(defun elmo-nntp-send-command (session command &optional noerase no-log)
  (with-current-buffer (elmo-network-session-buffer session)
    (unless noerase
      (erase-buffer)
      (goto-char (point-min)))
    (setq elmo-nntp-read-point (point))
    (elmo-nntp-debug "SEND: %s\n" (if no-log "<NO LOGGING>" command))
    (process-send-string (elmo-network-session-process-internal session)
			 (concat command "\r\n"))))

(defun elmo-nntp-read-response (session &optional not-command error-msg)
  (with-current-buffer (elmo-network-session-buffer session)
    (let ((process (elmo-network-session-process-internal session))
	  (response-continue t)
	  response match-end last
	  (start elmo-nntp-read-point))
      (while response-continue
	(setq match-end elmo-nntp-read-point)
	(while (null (progn (goto-char match-end)
			    (search-forward "\r\n" nil t)))
	  (setq match-end (max (1- (point-max)) elmo-nntp-read-point))
	  (accept-process-output process))
	(setq match-end (point)
	      last elmo-nntp-read-point
	      elmo-nntp-read-point match-end)
	(goto-char last)
	(cond
	 ((looking-at "[23][0-9]+ ")
	  (setq response-continue nil))
	 ((looking-at "[^23][0-9]+ ")
	  (setq response-continue nil
		start nil))
	 (not-command
	  (setq response-continue nil))))
      (setq response
	    (and start
		 (elmo-delete-cr (buffer-substring start (- match-end 2)))))
      (if error-msg
	  (cons response (buffer-substring last (- match-end 2)))
	response))))

(defun elmo-nntp-read-raw-response (session)
  (with-current-buffer (elmo-network-session-buffer session)
    (goto-char elmo-nntp-read-point)
    (while (not (search-forward "\r\n" nil t))
      (accept-process-output (elmo-network-session-process-internal
			      session))
      (goto-char elmo-nntp-read-point))
    (buffer-substring elmo-nntp-read-point (- (point) 2))))

(defun elmo-nntp-read-contents (session)
  (with-current-buffer (elmo-network-session-buffer session)
    (let ((point elmo-nntp-read-point))
      (while (null (progn (goto-char (1- point))
			  (search-forward "\n.\r\n" nil t)))
  	(setq point (max (- (point-max) 2) elmo-nntp-read-point))
	(accept-process-output (elmo-network-session-process-internal
				session)))
      (elmo-delete-cr (buffer-substring
		       elmo-nntp-read-point (- (point) 3))))))

(defun elmo-nntp-read-body (session outbuf)
  (with-current-buffer (elmo-network-session-buffer session)
    (let ((point elmo-nntp-read-point))
      (while (null (progn (goto-char (1- point))
			  (search-forward "\n.\r\n" nil t)))
	(setq point (max (- (point-max) 2) elmo-nntp-read-point))
	(accept-process-output
	 (elmo-network-session-process-internal session)))
      (setq point (point))
      (set-buffer outbuf)
      (erase-buffer)
      (insert-buffer-substring
       (elmo-network-session-buffer session) elmo-nntp-read-point (- point 3))
      (elmo-delete-cr-buffer)))
  t)

(defun elmo-nntp-select-group (session group &optional force)
  (let (response)
    (when (or force
	      (not (string= (elmo-nntp-session-current-group-internal session)
			    group)))
      (unwind-protect
	  (progn
	    (elmo-nntp-send-command session (format "group %s" group))
	    (setq response (elmo-nntp-read-response session)))
	(elmo-nntp-session-set-current-group-internal session
						      (and response group))
	response))))

(defun elmo-nntp-list-folders-get-cache (group server buf)
  (when (and elmo-nntp-list-folders-use-cache
	     elmo-nntp-list-folders-cache
	     (string-match (concat "^"
				   (regexp-quote
				    (or (nth 1 elmo-nntp-list-folders-cache)
					"")))
			   (or group ""))
	     (string= (or (nth 2 elmo-nntp-list-folders-cache) "")
		      (or server ""))
	     (null (elmo-time-expire (car elmo-nntp-list-folders-cache)
				     elmo-nntp-list-folders-use-cache)))
    (with-current-buffer buf
      (if group
	  (let ((regexp (concat "^" (regexp-quote group) "\\..*$"))
		(string (nth 3 elmo-nntp-list-folders-cache))
		start)
	    (while (string-match regexp string start)
	      (insert (match-string 0 string) "\n")
	      (setq start (match-end 0))))
	(insert (nth 3 elmo-nntp-list-folders-cache))))
    t))

(defsubst elmo-nntp-catchup-msgdb (msgdb max-number)
  (elmo-make-number-list (elmo-max-of-list (elmo-msgdb-list-messages msgdb))
			 max-number))

(luna-define-method elmo-folder-list-subfolders ((folder elmo-nntp-folder)
						 &optional one-level)
  (elmo-nntp-folder-list-subfolders folder one-level))

(defun elmo-nntp-folder-list-subfolders (folder one-level)
  (let ((session (elmo-nntp-get-session folder))
	(group (elmo-nntp-folder-group-internal folder))
	(server (elmo-net-folder-server-internal folder))
	(username (or (elmo-net-folder-user-internal folder) ""))
	(port (elmo-net-folder-port-internal folder))
	(stream-type (elmo-net-folder-stream-type-internal folder))
	case-fold-search
	response ret-val top-ng append-serv prefix start regexp)
    (setq append-serv
	  (concat
	   (unless (string= username (or elmo-nntp-default-user ""))
	     (concat ":" (elmo-quote-syntactical-element
			  username 'user elmo-nntp-folder-name-syntax)))
	   (unless (string= server elmo-nntp-default-server)
	     (concat "@" server))
	   (unless (eq port elmo-nntp-default-port)
	     (concat ":" (number-to-string port)))
	   (unless (eq (elmo-network-stream-type-symbol stream-type)
		       elmo-nntp-default-stream-type)
	     (elmo-network-stream-type-spec-string stream-type)))
	  prefix (list (car (rassq 'nntp elmo-folder-type-alist))))
    (when (string= group "") (setq group nil))
    (with-temp-buffer
      (set-buffer-multibyte nil)
      (if (and group (elmo-nntp-select-group session group))
	  ;; add top newsgroups
	  (setq ret-val (list (concat prefix group append-serv))))
      (unless (elmo-nntp-list-folders-get-cache group server (current-buffer))
	(when (and group (elmo-nntp-list-active-p session))
	  (elmo-nntp-send-command
	   session (concat "list active" (and group (concat " " group ".*"))))
	  (if (elmo-nntp-read-response session t)
	      (if (null (setq response (elmo-nntp-read-contents session)))
		  (error "NNTP List folders failed")
		(when elmo-nntp-list-folders-use-cache
		  (setq elmo-nntp-list-folders-cache
			(list (current-time) group server response)))
		(insert response))
	    (elmo-nntp-set-list-active session nil)))
	(unless response
	  (elmo-nntp-send-command session "list")
	  (unless (and (elmo-nntp-read-response session t)
		       (setq response (elmo-nntp-read-contents session)))
	    (error "NNTP List folders failed"))
	  (when elmo-nntp-list-folders-use-cache
	    (setq elmo-nntp-list-folders-cache
		  (list (current-time) nil server response)))
	  (if group
	      (progn
		(setq regexp (concat "^" (regexp-quote group) ".*$"))
		(while (string-match regexp response start)
		  (insert (match-string 0 response) "\n")
		  (setq start (match-end 0))))
	    (insert response))))
      (goto-char (point-min))
      (elmo-with-progress-display
	  (elmo-nntp-parse-active (count-lines (point-min) (point-max)))
	  "Parsing active"
	(if one-level
	    (progn
	      (setq regexp (concat "^\\("
				   (when group
				     (regexp-quote (concat group ".")))
				   "[^. ]+\\)\\([. ]\\).*\n"))
	      (while (looking-at regexp)
		(setq top-ng (concat prefix
				     (match-string-no-properties 1)
				     append-serv))
		(if (string= (match-string-no-properties 2) " ")
		    (unless (or (member top-ng ret-val)
				(assoc top-ng ret-val))
		      (setq ret-val (cons top-ng ret-val)))
		  (unless (assoc top-ng ret-val)
		    (setq ret-val (cons (list top-ng)
					(delete top-ng ret-val)))))
		(elmo-progress-notify 'elmo-nntp-parse-active)
		(forward-line)))
	  (while (re-search-forward "\\([^ ]+\\) .*\n" nil t)
	    (setq ret-val (cons (concat prefix (match-string-no-properties 1)
					append-serv)
				ret-val))
	    (elmo-progress-notify 'elmo-nntp-parse-active)))))
    (nreverse ret-val)))

(defun elmo-nntp-make-msglist (beg-str end-str)
  (elmo-make-number-list (string-to-number beg-str)
			 (string-to-number end-str)))

(luna-define-method elmo-folder-list-messages-plugged ((folder
							elmo-nntp-folder)
						       &optional _nohide)
  (let ((session (elmo-nntp-get-session folder))
	(group   (elmo-nntp-folder-group-internal folder))
	response numbers use-listgroup)
    (save-excursion
      (when (setq use-listgroup (elmo-nntp-listgroup-p session))
	(elmo-nntp-send-command session
				(format "listgroup %s" group))
	(if (not (elmo-nntp-read-response session t))
	    (progn
	      (elmo-nntp-set-listgroup session nil)
	      (setq use-listgroup nil))
	  (if (null (setq response (elmo-nntp-read-contents session)))
	      (error "Fetching listgroup failed"))
	  (setq numbers (elmo-string-to-list response))
	  (elmo-nntp-session-set-current-group-internal session
							group)))
      (unless use-listgroup
	(elmo-nntp-send-command session (format "group %s" group))
	(if (null (setq response (elmo-nntp-read-response session)))
	    (error "Select group failed"))
	(when (and
	       (string-match
		"211 \\([0-9]+\\) \\([0-9]+\\) \\([0-9]+\\) [^.].+$"
		response)
	       (> (string-to-number (match-string 1 response)) 0))
	  (setq numbers (elmo-nntp-make-msglist
			 (match-string 2 response)
			 (match-string 3 response)))))
      numbers)))

(luna-define-method elmo-folder-status ((folder elmo-nntp-folder))
  (elmo-nntp-folder-status folder))

(defun elmo-nntp-folder-status (folder)
  (let ((killed-list (elmo-msgdb-killed-list-load
		      (elmo-folder-msgdb-path folder)))
	end-num entry)
    (if elmo-nntp-groups-async
	(if (setq entry
		  (gethash
		   (concat (elmo-nntp-folder-group-internal folder)
			   (elmo-nntp-folder-postfix
			    (elmo-net-folder-user-internal folder)
			    (elmo-net-folder-server-internal folder)
			    (elmo-net-folder-port-internal folder)
			    (elmo-net-folder-stream-type-internal folder)))
		   elmo-newsgroups-hashtb))
	    (progn
	      (setq end-num (nth 2 entry))
	      (when (and killed-list
			 (elmo-number-set-member end-num killed-list))
		;; Max is killed.
		(setq end-num nil))
	      (cons end-num (car entry)))
	  (error "No such newsgroup \"%s\""
		 (elmo-nntp-folder-group-internal folder)))
      (let ((session (elmo-nntp-get-session folder))
	    response e-num)
	(if (null session)
	    (error "Connection failed"))
	(save-excursion
	  (elmo-nntp-send-command session
				  (format
				   "group %s"
				   (elmo-nntp-folder-group-internal folder)))
	  (setq response (elmo-nntp-read-response session))
	  (if (and response
		   (string-match
		    "211 \\([0-9]+\\) \\([0-9]+\\) \\([0-9]+\\) [^.].+$"
		    response))
	      (progn
		(setq end-num (string-to-number (match-string 3 response)))
		(setq e-num (string-to-number (match-string 1 response)))
		(when (and killed-list
			   (elmo-number-set-member end-num killed-list))
		  ;; Max is killed.
		  (setq end-num nil))
		(cons end-num e-num))
	    (if (null response)
		(error "Selecting newsgroup \"%s\" failed"
		       (elmo-nntp-folder-group-internal folder))
	      nil)))))))

(defconst elmo-nntp-overview-index
  '(("number" . 0)
    ("subject" . 1)
    ("from" . 2)
    ("date" . 3)
    ("message-id" . 4)
    ("references" . 5)
    ("size" . 6)
    ("lines" . 7)
    ("xref" . 8)))

(defun elmo-nntp-create-msgdb-from-overview-string (folder
						    str
						    flag-table
						    &optional numlist)
  (let ((new-msgdb (elmo-make-msgdb))
	ov-list message-id entity
	ov-entity num
	field field-index flags)
    (setq ov-list (elmo-nntp-parse-overview-string str))
    (while ov-list
      (setq ov-entity (car ov-list))
;;; INN bug??
;;;      (if (or (> (setq num (string-to-number (aref ov-entity 0)))
;;;		 99999)
;;;	      (<= num 0))
;;;	  (setq num 0))
;;;      (setq num (number-to-string num))
      (setq num (string-to-number (aref ov-entity 0)))
      (when (or (null numlist)
		(memq num numlist))
	(setq entity (elmo-msgdb-make-message-entity
		      (elmo-msgdb-message-entity-handler new-msgdb)
		      :message-id (aref ov-entity 4)
		      :number     num
		      :references (nreverse
				   (mapcar 'std11-msg-id-string
					   (std11-parse-msg-ids-string
					    (aref ov-entity 5))))
		      :from       (eword-decode-string
				   (elmo-delete-char  ?\"
						      (or (aref ov-entity 2)
							  elmo-no-from)))
		      :subject    (or (eword-decode-string
				       (aref ov-entity 1))
				      elmo-no-subject)
		      :date       (aref ov-entity 3)
		      :size       (string-to-number (aref ov-entity 6))))
	(dolist (extra elmo-msgdb-extra-fields)
	  (setq extra (downcase extra))
	  (when (and (setq field-index
			   (cdr (assoc extra elmo-nntp-overview-index)))
		     (> (length ov-entity) field-index))
	    (setq field (aref ov-entity field-index))
	    (when (eq field-index 8) ;; xref
	      (setq field (elmo-msgdb-remove-field-string field)))
	    (elmo-message-entity-set-field entity (intern extra) field)))
	(setq message-id (elmo-message-entity-field entity 'message-id)
	      flags (elmo-flag-table-get flag-table message-id))
	(elmo-global-flags-set flags folder num message-id)
	(elmo-msgdb-append-entity new-msgdb entity flags))
      (setq ov-list (cdr ov-list)))
    new-msgdb))

(luna-define-method elmo-folder-msgdb-create ((folder elmo-nntp-folder)
					      numbers flag-table)
  (elmo-nntp-folder-msgdb-create folder numbers flag-table))

(defun elmo-nntp-folder-msgdb-create (folder numbers flag-table)
  (let ((filter numbers)
	(session (elmo-nntp-get-session folder))
	(new-msgdb (elmo-make-msgdb))
	beg-num end-num cur length
	ov-str use-xover)
    (elmo-nntp-select-group session (elmo-nntp-folder-group-internal
				     folder))
    (when (setq use-xover (elmo-nntp-xover-p session))
      (setq beg-num (car numbers)
	    cur beg-num
	    end-num (nth (1- (length numbers)) numbers)
	    length  (+ (- end-num beg-num) 1))
      (elmo-with-progress-display (elmo-retrieve-overview length)
	  "Getting overview"
	(while (<= cur end-num)
	  (elmo-nntp-send-command
	   session
	   (format
	    "xover %s-%s"
	    (number-to-string cur)
	    (number-to-string
	     (+ cur
		elmo-nntp-overview-fetch-chop-length))))
	  (with-current-buffer (elmo-network-session-buffer session)
	    (if ov-str
		(elmo-msgdb-append
		 new-msgdb
		 (elmo-nntp-create-msgdb-from-overview-string
		  folder
		  ov-str
		  flag-table
		  filter))))
	  (if (null (elmo-nntp-read-response session t))
	      (progn
		(setq cur end-num);; exit while loop
		(elmo-nntp-set-xover session nil)
		(setq use-xover nil))
	    (if (null (setq ov-str (elmo-nntp-read-contents session)))
		(error "Fetching overview failed")))
	  (setq cur (+ elmo-nntp-overview-fetch-chop-length cur 1))
	  (elmo-progress-notify 'elmo-retrieve-overview
				:set (+ (- (min cur end-num) beg-num) 1)))))
    (if (not use-xover)
	(setq new-msgdb (elmo-nntp-msgdb-create-by-header
			 session numbers flag-table))
      (with-current-buffer (elmo-network-session-buffer session)
	(if ov-str
	    (elmo-msgdb-append
	     new-msgdb
	     (elmo-nntp-create-msgdb-from-overview-string
	      folder
	      ov-str
	      flag-table
	      filter)))))
    (elmo-folder-set-killed-list-internal
     folder
     (nconc
      (elmo-folder-killed-list-internal folder)
      (car (elmo-list-diff
	    numbers
	    (elmo-msgdb-list-messages new-msgdb)))))
    ;; If there are canceled messages, overviews are not obtained
    ;; to max-number(inn 2.3?).
    (when (and (elmo-nntp-max-number-precedes-list-active-p)
	       (elmo-nntp-list-active-p session))
      (elmo-nntp-send-command
       session (format "list active %s"
		       (elmo-nntp-folder-group-internal folder)))
      (unless (elmo-nntp-read-response session)
	(elmo-nntp-set-list-active session nil)
	(error "NNTP list command failed"))
      (let ((killed (elmo-nntp-catchup-msgdb
		     new-msgdb
		     (nth 1 (read (concat "(" (elmo-nntp-read-contents
					       session) ")"))))))
	(when killed
	  (elmo-folder-kill-messages folder killed))))
    new-msgdb))

(luna-define-method elmo-folder-update-number ((folder elmo-nntp-folder))
  (when (elmo-nntp-max-number-precedes-list-active-p)
    (let ((session (elmo-nntp-get-session folder)))
      (when (elmo-nntp-list-active-p session)
	(let ((numbers (elmo-folder-list-messages folder nil 'in-msgdb))
	      msgdb-max max-number)
	  ;; If there are canceled messages, overviews are not obtained
	  ;; to max-number(inn 2.3?).
	  (elmo-nntp-select-group session
				  (elmo-nntp-folder-group-internal folder))
	  (elmo-nntp-send-command session
				  (format "list active %s"
					  (elmo-nntp-folder-group-internal
					   folder)))
	  (if (null (elmo-nntp-read-response session))
	      (error "NNTP list command failed"))
	  (setq max-number
		(nth 1 (read (concat "(" (elmo-nntp-read-contents
					  session) ")"))))
	  (setq msgdb-max (if numbers (apply #'max numbers) 0))
	  (when (and msgdb-max
		     max-number
		     (< msgdb-max max-number))
	    (let ((i (1+ msgdb-max))
		  killed)
	      (while (<= i max-number)
		(setq killed (cons i killed))
		(cl-incf i))
	      (elmo-folder-kill-messages folder (nreverse killed)))))))))

(defun elmo-nntp-msgdb-create-by-header (session numbers flag-table)
  (with-temp-buffer
    (elmo-nntp-retrieve-headers session (current-buffer) numbers)
    (elmo-nntp-msgdb-create-message
     (length numbers) flag-table)))

(defun elmo-nntp-parse-xhdr-response (string)
  (let (response)
    (with-temp-buffer
      (insert string)
      (goto-char (point-min))
      (while (not (eobp))
	(if (looking-at "^\\([0-9]+\\) \\(.*\\)$")
	    (setq response (cons (cons (string-to-number
					(match-string-no-properties 1))
				       (match-string-no-properties 2))
				 response)))
	(forward-line)))
    (nreverse response)))

(defun elmo-nntp-parse-overview-string (string)
  (let ((index 0)
	(length (length string))
	next result)
    (while (or (setq next (string-match "\n" string index))
	       (/= index length))
      (setq result (cons (apply 'vector (split-string
					 (substring string index next) "\t"))
			 result)
	    index (if next (1+ next) length)))
    (nreverse result)))

(defun elmo-nntp-get-newsgroup-by-msgid (msgid server user port type)
  "Get nntp header string."
  (save-excursion
    (let ((session (elmo-nntp-get-session
		    (luna-make-entity
		     'elmo-nntp-folder
		     :user user
		     :server server
		     :port port
		     :stream-type type))))
      (elmo-nntp-send-command session
			      (format "head %s" msgid))
      (if (elmo-nntp-read-response session)
	  (elmo-nntp-read-contents session))
      (with-current-buffer (elmo-network-session-buffer session)
	(std11-field-body "Newsgroups")))))

(luna-define-method elmo-message-fetch :around
  ((folder elmo-nntp-folder) number _strategy &optional unread _section)
  (when (luna-call-next-method)
    (elmo-nntp-setup-crosspost-buffer folder number)
    (unless unread
      (elmo-nntp-folder-update-crosspost-message-alist
       folder (list number)))
    t))

(luna-define-method elmo-message-fetch-plugged ((folder elmo-nntp-folder)
						number strategy
						&optional section outbuf
						unread)
  (elmo-nntp-message-fetch folder number strategy section outbuf unread))

(defun elmo-nntp-message-fetch (folder number _strategy _section outbuf unread)
  (let ((session (elmo-nntp-get-session folder)))

    (with-current-buffer (elmo-network-session-buffer session)
      (elmo-nntp-select-group session (elmo-nntp-folder-group-internal folder))
      (elmo-nntp-send-command session (format "article %s" number))
      (if (null (elmo-nntp-read-response session t))
	  (progn
	    (with-current-buffer outbuf (erase-buffer))
	    (message "Fetching message failed")
	    nil)
	(prog1 (elmo-nntp-read-body session outbuf)
	  (with-current-buffer outbuf
	    (goto-char (point-min))
	    (while (re-search-forward "^\\." nil t)
	      (replace-match "")
	      (forward-line))
	    (elmo-nntp-setup-crosspost-buffer folder number)
	    (unless unread
	      (elmo-nntp-folder-update-crosspost-message-alist
	       folder (list number)))))))))

(defun elmo-nntp-post (hostname content-buf)
  (let ((session (elmo-nntp-get-session
		  (luna-make-entity
		   'elmo-nntp-folder
		   :user elmo-nntp-default-user
		   :server hostname
		   :port elmo-nntp-default-port
		   :stream-type
		   (elmo-get-network-stream-type
		    elmo-nntp-default-stream-type))))
	response has-message-id)
    (with-current-buffer content-buf
      (goto-char (point-min))
      (if (search-forward mail-header-separator nil t)
	  (delete-region (match-beginning 0)(match-end 0)))
      (setq has-message-id (elmo-get-message-id-from-buffer 'none))
      (elmo-nntp-send-command session "post")
      (if (string-match "^340" (setq response
				     (elmo-nntp-read-raw-response session)))
	  (if (string-match "recommended ID \\(<[^@]+@[^>]+>\\)" response)
	      (unless has-message-id
		;; We should remove invalid Message-ID header.
		(save-restriction
		  (save-match-data
		    (std11-narrow-to-header)
		    (goto-char (point-min))
		    (let ((case-fold-search t))
		      (if (re-search-forward "^message-id:[ \t]*" nil t)
			  (delete-region
			   (match-beginning 0)
			   (min (point-max) (1+ (std11-field-end))))))))
		(goto-char (point-min))
		(insert (concat "Message-ID: "
				(match-string 1 response) "\n"))))
	(error "POST failed"))
      (run-hooks 'elmo-nntp-post-pre-hook)
      (elmo-nntp-send-buffer session content-buf)
      (elmo-nntp-send-command session ".")
;;;      (elmo-nntp-read-response buffer process t)
      (if (not (string-match
		"^2" (setq response (elmo-nntp-read-raw-response
				     session))))
	  (error "NNTP error: %s" response)))))

(defsubst elmo-nntp-send-data-line (session line)
  "Send LINE to SESSION."
  (process-send-string
   (elmo-network-session-process-internal session)
   ;; Escape "." at start of a line
   (concat (if (eq (string-to-char line) ?.) ".") line "\r\n")))

(defun elmo-nntp-send-buffer (session databuf)
  "Send data content of DATABUF to SESSION."
  (with-current-buffer databuf
    (goto-char (point-min))
    (while (null (eobp))
      (elmo-nntp-send-data-line
       session (buffer-substring (point) (goto-char (line-end-position))))
      (forward-line))))

(luna-define-method elmo-folder-delete-messages ((folder elmo-nntp-folder)
						 numbers)
  (elmo-folder-kill-messages folder numbers)
  t)

(luna-define-method elmo-folder-exists-p-plugged ((folder elmo-nntp-folder))
  (let ((session (elmo-nntp-get-session folder)))
    (elmo-nntp-send-command
     session
     (format "group %s"
	     (elmo-nntp-folder-group-internal folder)))
    (elmo-nntp-read-response session)))

(defun elmo-nntp-retrieve-field (spec field from-msgs)
  "Retrieve FIELD values from FROM-MSGS.
Returns a list of cons cells like (NUMBER . VALUE)"
  (let ((session (elmo-nntp-get-session spec))
	result)
    (setq result
	  (if (elmo-nntp-xhdr-p session)
	      (progn
		(elmo-nntp-select-group
		 session (elmo-nntp-folder-group-internal spec))
		(elmo-nntp-send-command
		 session
		 (format "xhdr %s %s"
			 field
			 (if from-msgs
			     (format "%d-%d"
				     (apply 'min from-msgs)
				     (apply 'max from-msgs))
			   "0-")))
		(if (elmo-nntp-read-response session t)
		    (elmo-nntp-parse-xhdr-response
		     (elmo-nntp-read-contents session))
		  (elmo-nntp-set-xhdr session nil)
		  (error "NNTP XHDR command failed")))))
    (if from-msgs
	(delq nil (mapcar (lambda (pair) (when (memq (car pair) from-msgs)
					   pair))
			  result))
      result)))

(defun elmo-nntp-search-primitive (spec condition &optional from-msgs)
  (let ((search-key (elmo-filter-key condition))
	(numbers (cond
		  ((null from-msgs) (elmo-folder-list-messages spec))
		  ((listp from-msgs) from-msgs)
		  (t (elmo-folder-list-messages spec 'visible 'in-msgdb)))))
    (cond
     ((string= "last" search-key)
      (nthcdr (max (- (length numbers)
		      (string-to-number (elmo-filter-value condition)))
		   0)
	      numbers))
     ((string= "first" search-key)
      (car (elmo-list-diff
	    numbers
	    (nthcdr (string-to-number (elmo-filter-value condition))
		    numbers))))
     ((member search-key '("since" "before"))
      (let ((specified-date (elmo-date-make-sortable-string
			     (elmo-date-get-datevec (elmo-filter-value
						     condition))))
	    (since (string= "since" search-key))
	    field-date)
	(if (eq (elmo-filter-type condition) 'unmatch)
	    (setq since (not since)))
	(delq nil
	      (mapcar
	       (lambda (pair)
		 (setq field-date
		       (ignore-errors
			 (elmo-date-make-sortable-string
			  (timezone-fix-time
			   (cdr pair)
			   (current-time-zone) nil))))
		 (if (and field-date
			  (if since
			      (null (string< field-date specified-date))
			    (string< field-date specified-date)))
		     (car pair)))
	       (elmo-nntp-retrieve-field spec "date" numbers)))))
     (t
      (let ((val (elmo-filter-value condition))
	    (negative (eq (elmo-filter-type condition) 'unmatch))
	    (case-fold-search t))
	(delq nil
	      (mapcar
	       (lambda (pair)
		 (if (string-match val (eword-decode-string
					(decode-mime-charset-string
					 (cdr pair) elmo-mime-charset)))
		     (unless negative (car pair))
		   (if negative (car pair))))
	       (elmo-nntp-retrieve-field spec search-key numbers))))))))

(defun elmo-nntp-search-internal (folder condition from-msgs)
  (let (result)
    (cond
     ((vectorp condition)
      (setq result (elmo-nntp-search-primitive
		    folder condition from-msgs)))
     ((eq (car condition) 'and)
      (setq result (elmo-nntp-search-internal folder
					      (nth 1 condition)
					      from-msgs)
	    result (elmo-list-filter result
				     (elmo-nntp-search-internal
				      folder (nth 2 condition)
				      from-msgs))))
     ((eq (car condition) 'or)
      (setq result (elmo-nntp-search-internal folder
					      (nth 1 condition)
					      from-msgs)
	    result (elmo-sort-uniq-number-list
		    (nconc result
			   (elmo-nntp-search-internal
			    folder (nth 2 condition) from-msgs))))))))

(defun elmo-nntp-use-server-search-p (condition)
  (if (vectorp condition)
      (not (member (elmo-filter-key condition) '("raw-body" "body" "flag")))
    (and (elmo-nntp-use-server-search-p (nth 1 condition))
	 (elmo-nntp-use-server-search-p (nth 2 condition)))))

(luna-define-method elmo-folder-search :around ((folder elmo-nntp-folder)
						condition &optional from-msgs)
  (if (and (elmo-folder-plugged-p folder)
	   (elmo-nntp-use-server-search-p condition))
      (elmo-nntp-search-internal folder condition from-msgs)
    (luna-call-next-method)))

(defun elmo-nntp-get-folders-info-prepare (folder session-keys)
  (condition-case ()
      (let ((session (elmo-nntp-get-session folder))
	    key count)
	(with-current-buffer (elmo-network-session-buffer session)
	  (unless (setq key (assoc session session-keys))
	    (erase-buffer)
	    (setq key (cons session
			    (vector 0
				    (elmo-net-folder-server-internal folder)
				    (elmo-net-folder-user-internal folder)
				    (elmo-net-folder-port-internal folder)
				    (elmo-net-folder-stream-type-internal
				     folder))))
	    (setq session-keys (nconc session-keys (list key))))
	  (elmo-nntp-send-command session
				  (format "group %s"
					  (elmo-nntp-folder-group-internal
					   folder))
				  'noerase)
	  (if elmo-nntp-get-folders-securely
	      (accept-process-output
	       (elmo-network-session-process-internal session)
	       1))
	  (setq count (aref (cdr key) 0))
	  (aset (cdr key) 0 (1+ count))))
    (error
     (when elmo-auto-change-plugged
       (sit-for 1))
     nil))
  session-keys)

(defun elmo-nntp-get-folders-info (session-keys)
  (let ((sessions session-keys)
	(cur (get-buffer-create " *ELMO NNTP Temp*")))
    (while sessions
      (let* ((session (caar sessions))
	     (key     (cdar sessions))
	     (count   (aref key 0))
	     (server  (aref key 1))
	     (user    (aref key 2))
	     (port    (aref key 3))
	     (type    (aref key 4))
	     (hashtb (or elmo-newsgroups-hashtb
			 (setq elmo-newsgroups-hashtb
			       (elmo-make-hash count)))))
	(save-excursion
	  (elmo-nntp-groups-read-response session cur count)
	  (set-buffer cur)
	  (goto-char (point-min))
	  (let ((case-replace nil)
		(postfix (elmo-nntp-folder-postfix user server port type)))
	    (if (not (string= postfix ""))
		(save-excursion
		  (while (re-search-forward "^\\(211 [0-9]+ [0-9]+ [0-9]+ [^ \n]+\\)\\(.*\\)$" nil t)
		    (replace-match (concat (match-string 1)
					   (replace-regexp-in-string
					    "\\\\" "\\\\\\\\"
					    postfix t t)))))))
	  (let (len min max)
	    (while (not (eobp))
	      (condition-case ()
		  (when (= (following-char) ?2)
		    (read cur)
		    (setq len (read cur)
			  min (read cur)
			  max (read cur))
		    (puthash
		     (symbol-name (read cur)) (list len min max) hashtb))
		(error nil))
	      (forward-line))))
	(setq sessions (cdr sessions))))
    (kill-buffer cur)))

;; original is 'nntp-retrieve-groups [Gnus]
(defun elmo-nntp-groups-read-response (session outbuf count)
  (let* ((received 0)
	 (last-point (point-min)))
    (with-current-buffer (elmo-network-session-buffer session)
      (accept-process-output
       (elmo-network-session-process-internal session) 1)
      (discard-input)
      ;; Wait for all replies.
      (elmo-with-progress-display (elmo-nntp-groups-read-response count)
	  "Getting folders info"
	(while (progn
		 (goto-char last-point)
		 ;; Count replies.
		 (while (re-search-forward "^[0-9]" nil t)
		   (forward-line)
		   (setq received (1+ received)))
		 (setq last-point (point))
		 (< received count))
	  (accept-process-output
	   (elmo-network-session-process-internal session)
	   1)
	  (discard-input)
	  (elmo-progress-notify 'elmo-nntp-groups-read-response :set received)))
      ;; Wait for the reply from the final command.
      (goto-char (point-max))
      (re-search-backward "^[0-9]" nil t)
      (when (memq (following-char) '(?2 ?3))
	(while (progn
		 (goto-char (point-max))
		 (not (re-search-backward "\r?\n" (- (point) 3) t)))
	  (accept-process-output
	   (elmo-network-session-process-internal session) 1)
	  (discard-input)))
      ;; Now all replies are received.  We remove CRs.
      (elmo-delete-cr-buffer)
      (copy-to-buffer outbuf (point-min) (point-max)))))

;; from nntp.el [Gnus]

(defsubst elmo-nntp-next-result-arrived-p ()
  (if (eq (following-char) ?2)
      (re-search-forward "\n\\.\r?\n" nil t)
    (if (memq (following-char) '(?3 ?4))
	(search-forward "\n" nil t))))

(defun elmo-nntp-retrieve-headers (session outbuf articles)
  "Retrieve the headers of ARTICLES."
  (with-current-buffer (elmo-network-session-buffer session)
    (erase-buffer)
    (let ((number (length articles))
	  (count 0)
	  (received 0)
	  (last-point (point-min))
	  article)
      (elmo-with-progress-display (elmo-retrieve-header number)
	  "Getting headers"
	;; Send HEAD commands.
	(while (setq article (pop articles))
	  (elmo-nntp-send-command session
				  (format "head %s" article)
				  'noerase)
	  (setq count (1+ count))
	  ;; Every 200 requests we have to read the stream in
	  ;; order to avoid deadlocks.
	  (when (or (null articles)	;All requests have been sent.
		    (zerop (% count elmo-nntp-header-fetch-chop-length)))
	    (accept-process-output
	     (elmo-network-session-process-internal session) 1)
	    (discard-input)
	    (while (progn
		     (goto-char last-point)
		     ;; Count replies.
		     (while (elmo-nntp-next-result-arrived-p)
		       (setq last-point (point))
		       (setq received (1+ received)))
		     (< received count))
	      (elmo-progress-notify 'elmo-retrieve-header :set received)
	      (accept-process-output
	       (elmo-network-session-process-internal session) 1)
	      (discard-input)))))
      ;; Replace all CRLF with LF.
      (elmo-delete-cr-buffer)
      (copy-to-buffer outbuf (point-min) (point-max)))))

;; end of from Gnus

(defun elmo-nntp-msgdb-create-message (len flag-table)
  (save-excursion
    (let ((new-msgdb (elmo-make-msgdb))
	  beg entity num message-id)
      (set-buffer-multibyte nil)
      (goto-char (point-min))
      (elmo-with-progress-display (elmo-folder-msgdb-create len)
	  "Creating msgdb"
	(while (not (eobp))
	  (setq beg (save-excursion (forward-line) (point)))
	  (setq num
		(and (looking-at "^2[0-9]*[ ]+\\([0-9]+\\)")
		     (string-to-number
		      (match-string-no-properties 1))))
	  (elmo-nntp-next-result-arrived-p)
	  (when num
	    (save-excursion
	      (forward-line -1)
	      (save-restriction
		(narrow-to-region beg (point))
		(setq entity
		      (elmo-msgdb-create-message-entity-from-header
		       (elmo-msgdb-message-entity-handler new-msgdb) num))
		(when entity
		  (setq message-id
			(elmo-message-entity-field entity 'message-id))
		  (elmo-msgdb-append-entity
		   new-msgdb
		   entity
		   (elmo-flag-table-get flag-table message-id))))))
	  (elmo-progress-notify 'elmo-folder-msgdb-create)))
      new-msgdb)))

(luna-define-method elmo-message-use-cache-p ((_folder elmo-nntp-folder) _number)
  elmo-nntp-use-cache)

(defun elmo-nntp-parse-newsgroups (string &optional subscribe-only)
  (let ((nglist (elmo-parse string "[ \t\f\r\n,]*\\([^ \t\f\r\n,]+\\)"))
	ngs)
    (if (not subscribe-only)
	nglist
      (dolist (ng nglist)
	(if (elmo-has-hash-val ng elmo-newsgroups-hashtb)
	    (setq ngs (cons ng ngs))))
      ngs)))

;;; Crosspost processing.

;; 1. setup crosspost alist.
;;    1.1. When message is fetched and is crossposted message,
;;         it is remembered in `temp-crosses' slot.
;;         temp-crosses slot is a list of cons cell:
;;         (NUMBER . (MESSAGE-ID (LIST-OF-NEWSGROUPS) 'ng))
;;    1.2. In elmo-folder-close, `temp-crosses' slot is cleared,
;;    1.3. In elmo-folder-flag-as-read, move crosspost entry
;;         from `temp-crosses' slot to `elmo-crosspost-message-alist'.

;; 2. process crosspost alist.
;;    2.1. At elmo-folder-process-crosspost, setup `reads' slot from
;;         `elmo-crosspost-message-alist'.
;;    2.2. remove crosspost entry for current newsgroup from
;;         `elmo-crosspost-message-alist'.
;;    2.3. elmo-folder-list-unreads return unread message list according to
;;         `reads' slot.
;;         (There's a problem that if `elmo-folder-list-unreads'
;;           never executed, crosspost information is thrown away.)
;;    2.4. In elmo-folder-close, `read' slot is cleared,

(defun elmo-nntp-setup-crosspost-buffer (folder number)
;;    1.1. When message is fetched and is crossposted message,
;;         it is remembered in `temp-crosses' slot.
;;         temp-crosses slot is a list of cons cell:
;;         (NUMBER . (MESSAGE-ID (LIST-OF-NEWSGROUPS) 'ng))
  (let (newsgroups crosspost-newsgroups message-id)
    (save-restriction
      (std11-narrow-to-header)
      (setq newsgroups (std11-fetch-field "newsgroups")
	    message-id (elmo-get-message-id-from-header 'none)))
    (when newsgroups
      (when (setq crosspost-newsgroups
		  (delete
		   (elmo-nntp-folder-group-internal folder)
		   (elmo-nntp-parse-newsgroups newsgroups t)))
	(unless (assq number
		      (elmo-nntp-folder-temp-crosses-internal folder))
	  (elmo-nntp-folder-set-temp-crosses-internal
	   folder
	   (cons (cons number (list message-id crosspost-newsgroups 'ng))
		 (elmo-nntp-folder-temp-crosses-internal folder))))))))

(luna-define-method elmo-folder-close-internal ((folder elmo-nntp-folder))
;;    1.2. In elmo-folder-close, `temp-crosses' slot is cleared,
  (elmo-nntp-folder-set-temp-crosses-internal folder nil)
  (elmo-nntp-folder-set-reads-internal folder nil))

(defun elmo-nntp-folder-update-crosspost-message-alist (folder numbers)
;;    1.3. In elmo-folder-flag-as-read, move crosspost entry
;;         from `temp-crosses' slot to `elmo-crosspost-message-alist'.
  (let (elem)
    (dolist (number numbers)
      (when (setq elem (assq number
			     (elmo-nntp-folder-temp-crosses-internal folder)))
	(unless (assoc (cdr (cdr elem)) elmo-crosspost-message-alist)
	  (setq elmo-crosspost-message-alist
		(cons (cdr elem) elmo-crosspost-message-alist)))
	(elmo-nntp-folder-set-temp-crosses-internal
	 folder
	 (delq elem (elmo-nntp-folder-temp-crosses-internal folder)))))))

(luna-define-method elmo-folder-set-flag :before ((folder elmo-nntp-folder)
						  numbers
						  flag
						  &optional _is-local)
  (when (eq flag 'read)
    (elmo-nntp-folder-update-crosspost-message-alist folder numbers)))

(luna-define-method elmo-folder-unset-flag :before ((folder elmo-nntp-folder)
						    numbers
						    flag
						    &optional _is-local)
  (when (eq flag 'unread)
    (elmo-nntp-folder-update-crosspost-message-alist folder numbers)))

(defsubst elmo-nntp-folder-process-crosspost (folder)
;;    2.1. At elmo-folder-process-crosspost, setup `reads' slot from
;;         `elmo-crosspost-message-alist'.
;;    2.2. remove crosspost entry for current newsgroup from
;;         `elmo-crosspost-message-alist'.
  (let (cross-deletes reads entity ngs)
    (dolist (cross elmo-crosspost-message-alist)
      (when (setq entity (elmo-message-entity folder (nth 0 cross)))
	(setq reads (cons (elmo-message-entity-number entity) reads)))
      (when entity
	(if (setq ngs (delete (elmo-nntp-folder-group-internal folder)
			      (nth 1 cross)))
	    (setcar (cdr cross) ngs)
	  (setq cross-deletes (cons cross cross-deletes)))
	(setq elmo-crosspost-message-alist-modified t)))
    (dolist (dele cross-deletes)
      (setq elmo-crosspost-message-alist (delq
					  dele
					  elmo-crosspost-message-alist)))
    (elmo-nntp-folder-set-reads-internal folder reads)))

(luna-define-method elmo-folder-process-crosspost ((folder elmo-nntp-folder))
  (elmo-nntp-folder-process-crosspost folder))

(luna-define-method elmo-folder-list-flagged :around ((folder elmo-nntp-folder)
						      flag &optional in-msgdb)
  ;;    2.3. elmo-folder-list-unreads return unread message list according to
  ;;         `reads' slot.
  (let ((msgs (luna-call-next-method)))
    (if in-msgdb
	msgs
      (cl-case flag
	(unread
	 (elmo-living-messages msgs (elmo-nntp-folder-reads-internal folder)))
	;; Should consider read, digest and any flag?
	(otherwise
	 msgs)))))

(require 'product)
(product-provide (provide 'elmo-nntp) (require 'elmo-version))

;;; elmo-nntp.el ends here
