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+;;; gnus-int.el --- backend interface functions for Gnus
+;; Copyright (C) 1996,97 Free Software Foundation, Inc.
+
+;; Author: Lars Magne Ingebrigtsen <[email protected]>
+;; 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 2, 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; 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 'gnus)
+
+(defcustom gnus-open-server-hook nil
+  "Hook called just before opening connection to the news server."
+  :group 'gnus-start
+  :type 'hook)
+
+;;;
+;;; Server Communication
+;;;
+
+(defun gnus-start-news-server (&optional confirm)
+  "Open a method for getting news.
+If CONFIRM is non-nil, the user will be asked for an NNTP server."
+  (let (how)
+    (if gnus-current-select-method
+	;; Stream is already opened.
+	nil
+      ;; Open NNTP server.
+      (unless gnus-nntp-service
+	(setq gnus-nntp-server nil))
+      (when confirm
+	;; Read server name with completion.
+	(setq gnus-nntp-server
+	      (completing-read "NNTP server: "
+			       (mapcar (lambda (server) (list server))
+				       (cons (list gnus-nntp-server)
+					     gnus-secondary-servers))
+			       nil nil gnus-nntp-server)))
+
+      (when (and gnus-nntp-server
+		 (stringp gnus-nntp-server)
+		 (not (string= gnus-nntp-server "")))
+	(setq gnus-select-method
+	      (cond ((or (string= gnus-nntp-server "")
+			 (string= gnus-nntp-server "::"))
+		     (list 'nnspool (system-name)))
+		    ((string-match "^:" gnus-nntp-server)
+		     (list 'nnmh gnus-nntp-server
+			   (list 'nnmh-directory
+				 (file-name-as-directory
+				  (expand-file-name
+				   (concat "~/" (substring
+						 gnus-nntp-server 1)))))
+			   (list 'nnmh-get-new-mail nil)))
+		    (t
+		     (list 'nntp gnus-nntp-server)))))
+
+      (setq how (car gnus-select-method))
+      (cond
+       ((eq how 'nnspool)
+	(require 'nnspool)
+	(gnus-message 5 "Looking up local news spool..."))
+       ((eq how 'nnmh)
+	(require 'nnmh)
+	(gnus-message 5 "Looking up mh spool..."))
+       (t
+	(require 'nntp)))
+      (setq gnus-current-select-method gnus-select-method)
+      (run-hooks 'gnus-open-server-hook)
+      (or
+       ;; gnus-open-server-hook might have opened it
+       (gnus-server-opened gnus-select-method)
+       (gnus-open-server gnus-select-method)
+       (gnus-y-or-n-p
+	(format
+	 "%s (%s) open error: '%s'.  Continue? "
+	 (car gnus-select-method) (cadr gnus-select-method)
+	 (gnus-status-message gnus-select-method)))
+       (gnus-error 1 "Couldn't open server on %s"
+		   (nth 1 gnus-select-method))))))
+
+(defun gnus-check-group (group)
+  "Try to make sure that the server where GROUP exists is alive."
+  (let ((method (gnus-find-method-for-group group)))
+    (or (gnus-server-opened method)
+	(gnus-open-server method))))
+
+(defun gnus-check-server (&optional method silent)
+  "Check whether the connection to METHOD is down.
+If METHOD is nil, use `gnus-select-method'.
+If it is down, start it up (again)."
+  (let ((method (or method gnus-select-method)))
+    ;; Transform virtual server names into select methods.
+    (when (stringp method)
+      (setq method (gnus-server-to-method method)))
+    (if (gnus-server-opened method)
+	;; The stream is already opened.
+	t
+      ;; Open the server.
+      (unless silent
+	(gnus-message 5 "Opening %s server%s..." (car method)
+		      (if (equal (nth 1 method) "") ""
+			(format " on %s" (nth 1 method)))))
+      (run-hooks 'gnus-open-server-hook)
+      (prog1
+	  (gnus-open-server method)
+	(unless silent
+	  (message ""))))))
+
+(defun gnus-get-function (method function &optional noerror)
+  "Return a function symbol based on METHOD and FUNCTION."
+  ;; Translate server names into methods.
+  (unless method
+    (error "Attempted use of a nil select method"))
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (let ((func (intern (format "%s-%s" (car method) function))))
+    ;; If the functions isn't bound, we require the backend in
+    ;; question.
+    (unless (fboundp func)
+      (require (car method))
+      (when (and (not (fboundp func))
+		 (not noerror))
+	;; This backend doesn't implement this function.
+	(error "No such function: %s" func)))
+    func))
+
+
+;;;
+;;; Interface functions to the backends.
+;;;
+
+(defun gnus-open-server (method)
+  "Open a connection to METHOD."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (let ((elem (assoc method gnus-opened-servers)))
+    ;; If this method was previously denied, we just return nil.
+    (if (eq (nth 1 elem) 'denied)
+	(progn
+	  (gnus-message 1 "Denied server")
+	  nil)
+      ;; Open the server.
+      (let ((result
+	     (funcall (gnus-get-function method 'open-server)
+		      (nth 1 method) (nthcdr 2 method))))
+	;; If this hasn't been opened before, we add it to the list.
+	(unless elem
+	  (setq elem (list method nil)
+		gnus-opened-servers (cons elem gnus-opened-servers)))
+	;; Set the status of this server.
+	(setcar (cdr elem) (if result 'ok 'denied))
+	;; Return the result from the "open" call.
+	result))))
+
+(defun gnus-close-server (method)
+  "Close the connection to METHOD."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (funcall (gnus-get-function method 'close-server) (nth 1 method)))
+
+(defun gnus-request-list (method)
+  "Request the active file from METHOD."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (funcall (gnus-get-function method 'request-list) (nth 1 method)))
+
+(defun gnus-request-list-newsgroups (method)
+  "Request the newsgroups file from METHOD."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (funcall (gnus-get-function method 'request-list-newsgroups) (nth 1 method)))
+
+(defun gnus-request-newgroups (date method)
+  "Request all new groups since DATE from METHOD."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (let ((func (gnus-get-function method 'request-newgroups t)))
+    (when func
+      (funcall func date (nth 1 method)))))
+
+(defun gnus-server-opened (method)
+  "Check whether a connection to METHOD has been opened."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (funcall (inline (gnus-get-function method 'server-opened)) (nth 1 method)))
+
+(defun gnus-status-message (method)
+  "Return the status message from METHOD.
+If METHOD is a string, it is interpreted as a group name.   The method
+this group uses will be queried."
+  (let ((method (if (stringp method) (gnus-find-method-for-group method)
+		  method)))
+    (funcall (gnus-get-function method 'status-message) (nth 1 method))))
+
+(defun gnus-request-regenerate (method)
+  "Request a data generation from METHOD."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (funcall (gnus-get-function method 'request-regenerate) (nth 1 method)))
+
+(defun gnus-request-group (group &optional dont-check method)
+  "Request GROUP.  If DONT-CHECK, no information is required."
+  (let ((method (or method (inline (gnus-find-method-for-group group)))))
+    (when (stringp method)
+      (setq method (inline (gnus-server-to-method method))))
+    (funcall (inline (gnus-get-function method 'request-group))
+	     (gnus-group-real-name group) (nth 1 method) dont-check)))
+
+(defun gnus-list-active-group (group)
+  "Request active information on GROUP."
+  (let ((method (gnus-find-method-for-group group))
+	(func 'list-active-group))
+    (when (gnus-check-backend-function func group)
+      (funcall (gnus-get-function method func)
+	       (gnus-group-real-name group) (nth 1 method)))))
+
+(defun gnus-request-group-description (group)
+  "Request a description of GROUP."
+  (let ((method (gnus-find-method-for-group group))
+	(func 'request-group-description))
+    (when (gnus-check-backend-function func group)
+      (funcall (gnus-get-function method func)
+	       (gnus-group-real-name group) (nth 1 method)))))
+
+(defun gnus-close-group (group)
+  "Request the GROUP be closed."
+  (let ((method (inline (gnus-find-method-for-group group))))
+    (funcall (gnus-get-function method 'close-group)
+	     (gnus-group-real-name group) (nth 1 method))))
+
+(defun gnus-retrieve-headers (articles group &optional fetch-old)
+  "Request headers for ARTICLES in GROUP.
+If FETCH-OLD, retrieve all headers (or some subset thereof) in the group."
+  (let ((method (gnus-find-method-for-group group)))
+    (if (and gnus-use-cache (numberp (car articles)))
+	(gnus-cache-retrieve-headers articles group fetch-old)
+      (funcall (gnus-get-function method 'retrieve-headers)
+	       articles (gnus-group-real-name group) (nth 1 method)
+	       fetch-old))))
+
+(defun gnus-retrieve-groups (groups method)
+  "Request active information on GROUPS from METHOD."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (funcall (gnus-get-function method 'retrieve-groups) groups (nth 1 method)))
+
+(defun gnus-request-type (group &optional article)
+  "Return the type (`post' or `mail') of GROUP (and ARTICLE)."
+  (let ((method (gnus-find-method-for-group group)))
+    (if (not (gnus-check-backend-function 'request-type (car method)))
+	'unknown
+      (funcall (gnus-get-function method 'request-type)
+	       (gnus-group-real-name group) article))))
+
+(defun gnus-request-update-mark (group article mark)
+  "Return the type (`post' or `mail') of GROUP (and ARTICLE)."
+  (let ((method (gnus-find-method-for-group group)))
+    (if (not (gnus-check-backend-function 'request-update-mark (car method)))
+	mark
+      (funcall (gnus-get-function method 'request-update-mark)
+	       (gnus-group-real-name group) article mark))))
+
+(defun gnus-request-article (article group &optional buffer)
+  "Request the ARTICLE in GROUP.
+ARTICLE can either be an article number or an article Message-ID.
+If BUFFER, insert the article in that group."
+  (let ((method (gnus-find-method-for-group group)))
+    (funcall (gnus-get-function method 'request-article)
+	     article (gnus-group-real-name group) (nth 1 method) buffer)))
+
+(defun gnus-request-head (article group)
+  "Request the head of ARTICLE in GROUP."
+  (let* ((method (gnus-find-method-for-group group))
+	 (head (gnus-get-function method 'request-head t))
+	 res clean-up)
+    (cond
+     ;; Check the cache.
+     ((and gnus-use-cache
+	   (numberp article)
+	   (gnus-cache-request-article article group))
+      (setq res (cons group article)
+	    clean-up t))
+     ;; Use `head' function.
+     ((fboundp head)
+      (setq res (funcall head article (gnus-group-real-name group)
+			 (nth 1 method))))
+     ;; Use `article' function.
+     (t
+      (setq res (gnus-request-article article group)
+	    clean-up t)))
+    (when clean-up
+      (save-excursion
+	(set-buffer nntp-server-buffer)
+	(goto-char (point-min))
+	(when (search-forward "\n\n" nil t)
+	  (delete-region (1- (point)) (point-max)))
+	(nnheader-fold-continuation-lines)))
+    res))
+
+(defun gnus-request-body (article group)
+  "Request the body of ARTICLE in GROUP."
+  (let ((method (gnus-find-method-for-group group)))
+    (funcall (gnus-get-function method 'request-body)
+	     article (gnus-group-real-name group) (nth 1 method))))
+
+(defun gnus-request-post (method)
+  "Post the current buffer using METHOD."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (funcall (gnus-get-function method 'request-post) (nth 1 method)))
+
+(defun gnus-request-scan (group method)
+  "Request a SCAN being performed in GROUP from METHOD.
+If GROUP is nil, all groups on METHOD are scanned."
+  (let ((method (if group (gnus-find-method-for-group group) method))
+	(gnus-inhibit-demon t))
+    (funcall (gnus-get-function method 'request-scan)
+	     (and group (gnus-group-real-name group)) (nth 1 method))))
+
+(defsubst gnus-request-update-info (info method)
+  "Request that METHOD update INFO."
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (when (gnus-check-backend-function 'request-update-info (car method))
+    (funcall (gnus-get-function method 'request-update-info)
+	     (gnus-group-real-name (gnus-info-group info))
+	     info (nth 1 method))))
+
+(defun gnus-request-expire-articles (articles group &optional force)
+  (let ((method (gnus-find-method-for-group group)))
+    (funcall (gnus-get-function method 'request-expire-articles)
+	     articles (gnus-group-real-name group) (nth 1 method)
+	     force)))
+
+(defun gnus-request-move-article
+  (article group server accept-function &optional last)
+  (let ((method (gnus-find-method-for-group group)))
+    (funcall (gnus-get-function method 'request-move-article)
+	     article (gnus-group-real-name group)
+	     (nth 1 method) accept-function last)))
+
+(defun gnus-request-accept-article (group method &optional last)
+  ;; Make sure there's a newline at the end of the article.
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (when (and (not method)
+	     (stringp group))
+    (setq method (gnus-group-name-to-method group)))
+  (goto-char (point-max))
+  (unless (bolp)
+    (insert "\n"))
+  (let ((func (car (or method (gnus-find-method-for-group group)))))
+    (funcall (intern (format "%s-request-accept-article" func))
+	     (if (stringp group) (gnus-group-real-name group) group)
+	     (cadr method)
+	     last)))
+
+(defun gnus-request-replace-article (article group buffer)
+  (let ((func (car (gnus-find-method-for-group group))))
+    (funcall (intern (format "%s-request-replace-article" func))
+	     article (gnus-group-real-name group) buffer)))
+
+(defun gnus-request-associate-buffer (group)
+  (let ((method (gnus-find-method-for-group group)))
+    (funcall (gnus-get-function method 'request-associate-buffer)
+	     (gnus-group-real-name group))))
+
+(defun gnus-request-restore-buffer (article group)
+  "Request a new buffer restored to the state of ARTICLE."
+  (let ((method (gnus-find-method-for-group group)))
+    (funcall (gnus-get-function method 'request-restore-buffer)
+	     article (gnus-group-real-name group) (nth 1 method))))
+
+(defun gnus-request-create-group (group &optional method args)
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (let ((method (or method (gnus-find-method-for-group group))))
+    (funcall (gnus-get-function method 'request-create-group)
+	     (gnus-group-real-name group) (nth 1 method) args)))
+
+(defun gnus-request-delete-group (group &optional force)
+  (let ((method (gnus-find-method-for-group group)))
+    (funcall (gnus-get-function method 'request-delete-group)
+	     (gnus-group-real-name group) force (nth 1 method))))
+
+(defun gnus-request-rename-group (group new-name)
+  (let ((method (gnus-find-method-for-group group)))
+    (funcall (gnus-get-function method 'request-rename-group)
+	     (gnus-group-real-name group)
+	     (gnus-group-real-name new-name) (nth 1 method))))
+
+(defun gnus-close-backends ()
+  ;; Send a close request to all backends that support such a request.
+  (let ((methods gnus-valid-select-methods)
+	(gnus-inhibit-demon t)
+	func method)
+    (while (setq method (pop methods))
+      (when (fboundp (setq func (intern
+				 (concat (car method) "-request-close"))))
+	(funcall func)))))
+
+(defun gnus-asynchronous-p (method)
+  (let ((func (gnus-get-function method 'asynchronous-p t)))
+    (when (fboundp func)
+      (funcall func))))
+
+(defun gnus-remove-denial (method)
+  (when (stringp method)
+    (setq method (gnus-server-to-method method)))
+  (let* ((elem (assoc method gnus-opened-servers))
+	 (status (cadr elem)))
+    ;; If this hasn't been opened before, we add it to the list.
+    (when (eq status 'denied)
+      ;; Set the status of this server.
+      (setcar (cdr elem) 'closed))))
+
+(provide 'gnus-int)
+
+;;; gnus-int.el ends here