[gnus] / lisp / nnimap.el

;;; nnimap.el --- imap backend for Gnus

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

;; Author: Simon Josefsson <simon@josefsson.org>
;;         Jim Radford <radford@robby.caltech.edu>
;; Keywords: mail

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Todo, major things:
;;
;;   o Fix Gnus to view correct number of unread/total articles in group buffer
;;   o Fix Gnus to handle leading '.' in group names (fixed?)
;;   o Finish disconnected mode (moving articles between mailboxes unplugged)
;;   o Sieve
;;   o MIME (partial article fetches)
;;   o Split to other backends, different split rules for different
;;     servers/inboxes
;;
;; Todo, minor things:
;;
;;   o Don't require half of Gnus -- backends should be standalone
;;   o Verify that we don't use IMAP4rev1 specific things (RFC2060 App B)
;;   o Dont uid fetch 1,* in nnimap-retrive-groups (slow)
;;   o Split up big fetches (1,* header especially) in smaller chunks
;;   o What do I do with gnus-newsgroup-*?
;;   o Tell Gnus about new groups (how can we tell?)
;;   o Respooling (fix Gnus?) (unnecessary?)
;;   o Add support for the following: (if applicable)
;;       request-list-newsgroups, request-regenerate
;;       list-active-group,
;;       request-associate-buffer, request-restore-buffer,
;;   o Do The Right Thing when UIDVALIDITY changes (what's the right thing?)
;;   o Support RFC2221 (Login referrals)
;;   o IMAP2BIS compatibility? (RFC2061)
;;   o ACAP stuff (perhaps a different project, would be nice to ACAPify
;;     .newsrc.eld)
;;   o What about Gnus's article editing, can we support it?  NO!
;;   o Use \Draft to support the draft group??
;;   o Duplicate suppression
;;   o Rewrite UID SEARCH UID X as UID FETCH X (UID) for those with slow servers

;;; Code:

(require 'imap)
(require 'nnoo)
(require 'nnmail)
(require 'nnheader)
(require 'mm-util)
(require 'gnus)
(require 'gnus-range)
(require 'gnus-start)
(require 'gnus-int)

(eval-when-compile (require 'cl))

(autoload 'auth-source-user-or-password "auth-source")

(nnoo-declare nnimap)

(defconst nnimap-version "nnimap 1.0")

(defgroup nnimap nil
  "Reading IMAP mail with Gnus."
  :group 'gnus)

(defvoo nnimap-address nil
  "Address of physical IMAP server.  If nil, use the virtual server's name.")

(defvoo nnimap-server-port nil
  "Port number on physical IMAP server.
If nil, defaults to 993 for TLS/SSL connections and 143 otherwise.")

;; Splitting variables

(defcustom nnimap-split-crosspost t
  "If non-nil, do crossposting if several split methods match the mail.
If nil, the first match found will be used."
  :group 'nnimap
  :type 'boolean)

(defcustom nnimap-split-inbox nil
  "Name of mailbox to split mail from.

Mail is read from this mailbox and split according to rules in
`nnimap-split-rule'.

This can be a string or a list of strings."
  :group 'nnimap
  :type '(choice (string)
                 (repeat string)))

(define-widget 'nnimap-strict-function 'function
  "This widget only matches values that are functionp.

Warning: This means that a value that is the symbol of a not yet
loaded function will not match.  Use with care."
  :match 'nnimap-strict-function-match)

(defun nnimap-strict-function-match (widget value)
  "Ignoring WIDGET, match if VALUE is a function."
  (functionp value))

(defcustom nnimap-split-rule nil
  "Mail will be split according to these rules.

Mail is read from mailbox(es) specified in `nnimap-split-inbox'.

If you'd like, for instance, one mail group for mail from the
\"gnus-imap\" mailing list, one group for junk mail and leave
everything else in the incoming mailbox, you could do something like
this:

\(setq nnimap-split-rule '((\"INBOX.gnus-imap\"   \"From:.*gnus-imap\")
                          (\"INBOX.junk\"        \"Subject:.*buy\")))

As you can see, `nnimap-split-rule' is a list of lists, where the
first element in each \"rule\" is the name of the IMAP mailbox (or the
symbol `junk' if you want to remove the mail), and the second is a
regexp that nnimap will try to match on the header to find a fit.

The second element can also be a function.  In that case, it will be
called narrowed to the headers with the first element of the rule as
the argument.  It should return a non-nil value if it thinks that the
mail belongs in that group.

This variable can also have a function as its value, the function will
be called with the headers narrowed and should return a group where it
thinks the article should be splitted to.  See `nnimap-split-fancy'.

To allow for different split rules on different virtual servers, and
even different split rules in different inboxes on the same server,
the syntax of this variable have been extended along the lines of:

\(setq nnimap-split-rule
      '((\"my1server\"    (\".*\"    ((\"ding\"    \"ding@gnus.org\")
                                  (\"junk\"    \"From:.*Simon\")))
        (\"my2server\"    (\"INBOX\" nnimap-split-fancy))
        (\"my[34]server\" (\".*\"    ((\"private\" \"To:.*Simon\")
                                  (\"junk\"    my-junk-func)))))

The virtual server name is in fact a regexp, so that the same rules
may apply to several servers.  In the example, the servers
\"my3server\" and \"my4server\" both use the same rules.  Similarly,
the inbox string is also a regexp.  The actual splitting rules are as
before, either a function, or a list with group/regexp or
group/function elements."
  :group 'nnimap
  ;; FIXME: Doesn't allow `("my2server" ("INBOX" nnimap-split-fancy))'
  ;; per example above.  -- fx
  :type '(choice :tag "Rule type"
                 (repeat :menu-tag "Single-server"
                         :tag "Single-server list"
                         (list (string :tag "Mailbox")
                               (choice :tag "Predicate"
                                       (regexp :tag "A regexp")
                                       (nnimap-strict-function :tag "A function"))))
                 (choice :menu-tag "A function"
                         :tag "A function"
                         (function-item nnimap-split-fancy)
                         (function-item nnmail-split-fancy)
                         (nnimap-strict-function :tag "User-defined function"))
                 (repeat :menu-tag "Multi-server (extended)"
                         :tag "Multi-server list"
                         (list (regexp :tag "Server regexp")
                               (list (regexp :tag "Incoming Mailbox regexp")
                                     (repeat :tag "Rules for matching server(s) and mailbox(es)"
                                             (list (string :tag "Destination mailbox")
                                                   (choice :tag "Predicate"
                                                           (regexp :tag "A Regexp")
                                                           (nnimap-strict-function :tag "A Function")))))))))

(defcustom nnimap-split-predicate "UNSEEN UNDELETED"
  "The predicate used to find articles to split.
If you use another IMAP client to peek on articles but always would
like nnimap to split them once it's started, you could change this to
\"UNDELETED\". Other available predicates are available in
RFC2060 section 6.4.4."
  :group 'nnimap
  :type 'string)

(defcustom nnimap-split-fancy nil
  "Like the variable `nnmail-split-fancy'."
  :group 'nnimap
  :type 'sexp)

(defvar nnimap-split-download-body-default nil
  "Internal variable with default value for `nnimap-split-download-body'.")

(defcustom nnimap-split-download-body 'default
  "Whether to download entire articles during splitting.
This is generally not required, and will slow things down considerably.
You may need it if you want to use an advanced splitting function that
analyzes the body before splitting the article.
If this variable is nil, bodies will not be downloaded; if this
variable is the symbol `default' the default behavior is
used (which currently is nil, unless you use a statistical
spam.el test); if this variable is another non-nil value bodies
will be downloaded."
  :version "22.1"
  :group 'nnimap
  :type '(choice (const :tag "Let system decide" deault)
                 boolean))

;; Performance / bug workaround variables

(defcustom nnimap-close-asynchronous t
  "Close mailboxes asynchronously in `nnimap-close-group'.
This means that errors caught by nnimap when closing the mailbox will
not prevent Gnus from updating the group status, which may be harmful.
However, it increases speed."
  :version "22.1"
  :type 'boolean
  :group 'nnimap)

(defcustom nnimap-dont-close t
  "Never close mailboxes.
This increases the speed of closing mailboxes (quiting group) but may
decrease the speed of selecting another mailbox later.  Re-selecting
the same mailbox will be faster though."
  :version "22.1"
  :type 'boolean
  :group 'nnimap)

(defcustom nnimap-retrieve-groups-asynchronous t
  "Send asynchronous STATUS commands for each mailbox before checking mail.
If you have mailboxes that rarely receives mail, this speeds up new
mail checking.  It works by first sending STATUS commands for each
mailbox, and then only checking groups which has a modified UIDNEXT
more carefully for new mail.

In summary, the default is O((1-p)*k+p*n) and changing it to nil makes
it O(n).  If p is small, then the default is probably faster."
  :version "22.1"
  :type 'boolean
  :group 'nnimap)

(defvoo nnimap-need-unselect-to-notice-new-mail t
  "Unselect mailboxes before looking for new mail in them.
Some servers seem to need this under some circumstances.")

(defvoo nnimap-logout-timeout nil
  "Close server immediately if it can't logout in this number of seconds.
If it is nil, never close server until logout completes.  This variable
overrides `imap-logout-timeout' on a per-server basis.")

;; Authorization / Privacy variables

(defvoo nnimap-auth-method nil
  "Obsolete.")

(defvoo nnimap-stream nil
  "How nnimap will connect to the server.

The default, nil, will try to use the \"best\" method the server can
handle.

Change this if

1) you want to connect with TLS/SSL.  The TLS/SSL integration
   with IMAP is suboptimal so you'll have to tell it
   specifically.

2) your server is more capable than your environment -- i.e. your
   server accept Kerberos login's but you haven't installed the
   `imtest' program or your machine isn't configured for Kerberos.

Possible choices: gssapi, kerberos4, starttls, tls, ssl, network, shell.
See also `imap-streams' and `imap-stream-alist'.")

(defvoo nnimap-authenticator nil
  "How nnimap authenticate itself to the server.

The default, nil, will try to use the \"best\" method the server can
handle.

There is only one reason for fiddling with this variable, and that is
if your server is more capable than your environment -- i.e. you
connect to a server that accept Kerberos login's but you haven't
installed the `imtest' program or your machine isn't configured for
Kerberos.

Possible choices: gssapi, kerberos4, digest-md5, cram-md5, login, anonymous.
See also `imap-authenticators' and `imap-authenticator-alist'")

(defvoo nnimap-directory (nnheader-concat gnus-directory "overview/")
  "Directory to keep NOV cache files for nnimap groups.
See also `nnimap-nov-file-name'.")

(defvoo nnimap-nov-file-name "nnimap."
  "NOV cache base filename.
The group name and `nnimap-nov-file-name-suffix' will be appended.  A
typical complete file name would be
~/News/overview/nnimap.pdc.INBOX.ding.nov, or
~/News/overview/nnimap/pdc/INBOX/ding/nov if
`nnmail-use-long-file-names' is nil")

(defvoo nnimap-nov-file-name-suffix ".novcache"
  "Suffix for NOV cache base filename.")

(defvoo nnimap-nov-is-evil gnus-agent
  "If non-nil, never generate or use a local nov database for this backend.
Using nov databases should speed up header fetching considerably.
However, it will invoke a UID SEARCH UID command on the server, and
some servers implement this command inefficiently by opening each and
every message in the group, thus making it quite slow.
Unlike other backends, you do not need to take special care if you
flip this variable.")

(defvoo nnimap-search-uids-not-since-is-evil nil
  "If non-nil, avoid \"UID SEARCH UID ... NOT SINCE\" queries when expiring.
Instead, use \"UID SEARCH SINCE\" to prune the list of expirable
articles within Gnus.  This seems to be faster on Courier in some cases.")

(defvoo nnimap-expunge-on-close 'always ; 'ask, 'never
  "Whether to expunge a group when it is closed.
When a IMAP group with articles marked for deletion is closed, this
variable determine if nnimap should actually remove the articles or
not.

If always, nnimap always perform a expunge when closing the group.
If never, nnimap never expunges articles marked for deletion.
If ask, nnimap will ask you if you wish to expunge marked articles.

When setting this variable to `never', you can only expunge articles
by using `G x' (gnus-group-nnimap-expunge) from the Group buffer.")

(defvoo nnimap-list-pattern "*"
  "A string LIMIT or list of strings with mailbox wildcards used to limit available groups.
See below for available wildcards.

The LIMIT string can be a cons cell (REFERENCE . LIMIT), where
REFERENCE will be passed as the first parameter to LIST/LSUB.  The
semantics of this are server specific, on the University of Washington
server you can specify a directory.

Example:
 '(\"INBOX\" \"mail/*\" (\"~friend/mail/\" . \"list/*\"))

There are two wildcards * and %. * matches everything, % matches
everything in the current hierarchy.")

(defvoo nnimap-news-groups nil
  "IMAP support a news-like mode, also known as bulletin board mode,
where replies is sent via IMAP instead of SMTP.

This variable should contain a regexp matching groups where you wish
replies to be stored to the mailbox directly.

Example:
  '(\"^[^I][^N][^B][^O][^X].*$\")

This will match all groups not beginning with \"INBOX\".

Note that there is nothing technically different between mail-like and
news-like mailboxes.  If you wish to have a group with todo items or
similar which you wouldn't want to set up a mailing list for, you can
use this to make replies go directly to the group.")

(defvoo nnimap-expunge-search-string "UID %s NOT SINCE %s"
  "IMAP search command to use for articles that are to be expired.
The first %s is replaced by a UID set of articles to search on,
and the second %s is replaced by a date criterium.

One useful (and perhaps the only useful) value to change this to would
be `UID %s NOT SENTSINCE %s' to make nnimap use the Date: header
instead of the internal date of messages.  See section 6.4.4 of RFC
2060 for more information on valid strings.

However, if `nnimap-search-uids-not-since-is-evil' is true, this
variable has no effect since the search logic is reversed.")

(defvoo nnimap-importantize-dormant t
  "If non-nil, mark \"dormant\" articles as \"ticked\" for other IMAP clients.
Note that within Gnus, dormant articles will still (only) be
marked as ticked.  This is to make \"dormant\" articles stand out,
just like \"ticked\" articles, in other IMAP clients.")

(defvoo nnimap-server-address nil
  "Obsolete.  Use `nnimap-address'.")

(defcustom nnimap-authinfo-file "~/.authinfo"
  "Authorization information for IMAP servers.  In .netrc format."
  :type
  '(choice file
           (repeat :tag "Entries"
                   :menu-tag "Inline"
                   (list :format "%v"
                         :value ("" ("login" . "") ("password" . ""))
                         (string :tag "Host")
                         (checklist :inline t
                                    (cons :format "%v"
                                          (const :format "" "login")
                                          (string :format "Login: %v"))
                                    (cons :format "%v"
                                          (const :format "" "password")
                                          (string :format "Password: %v"))))))
  :group 'nnimap)

(defcustom nnimap-prune-cache t
  "If non-nil, nnimap check whether articles still exist on server before using data stored in NOV cache."
  :type 'boolean
  :group 'nnimap)

(defvar nnimap-request-list-method 'imap-mailbox-list
  "Method to use to request a list of all folders from the server.
If this is 'imap-mailbox-lsub, then use a server-side subscription list to
restrict visible folders.")

(defcustom nnimap-id nil
  "Plist with client identity to send to server upon login.
A nil value means no information is sent, symbol `no' to disable ID query
altogether, or plist with identifier-value pairs to send to
server.  RFC 2971 describes the list as follows:

   Any string may be sent as a field, but the following are defined to
   describe certain values that might be sent.  Implementations are free
   to send none, any, or all of these.  Strings are not case-sensitive.
   Field strings MUST NOT be longer than 30 octets.  Value strings MUST
   NOT be longer than 1024 octets.  Implementations MUST NOT send more
   than 30 field-value pairs.

     name            Name of the program
     version         Version number of the program
     os              Name of the operating system
     os-version      Version of the operating system
     vendor          Vendor of the client/server
     support-url     URL to contact for support
     address         Postal address of contact/vendor
     date            Date program was released, specified as a date-time
                       in IMAP4rev1
     command         Command used to start the program
     arguments       Arguments supplied on the command line, if any
                       if any
     environment     Description of environment, i.e., UNIX environment
                       variables or Windows registry settings

   Implementations MUST NOT send the same field name more than once.

An example plist would be '(\"name\" \"Gnus\" \"version\" gnus-version-number
\"os\" system-configuration \"vendor\" \"GNU\")."
  :group 'nnimap
  :type '(choice (const :tag "No information" nil)
                 (const :tag "Disable ID query" no)
                 (plist :key-type string :value-type string)))

(defcustom nnimap-debug nil
  "If non-nil, trace nnimap- functions into `nnimap-debug-buffer'.
Uses `trace-function-background', so you can turn it off with,
say, `untrace-all'.

Note that username, passwords and other privacy sensitive
information (such as e-mail) may be stored in the buffer.
It is not written to disk, however.  Do not enable this
variable unless you are comfortable with that.

This variable only takes effect when loading the `nnimap' library.
See also `nnimap-log'."
  :group 'nnimap
  :type 'boolean)

;; Internal variables:

(defvar nnimap-debug-buffer "*nnimap-debug*")
(defvar nnimap-mailbox-info (gnus-make-hashtable 997))
(defvar nnimap-current-move-server nil)
(defvar nnimap-current-move-group nil)
(defvar nnimap-current-move-article nil)
(defvar nnimap-length)
(defvar nnimap-progress-chars '(?| ?/ ?- ?\\))
(defvar nnimap-progress-how-often 20)
(defvar nnimap-counter)
(defvar nnimap-server-buffer-alist nil) ;; Map server name to buffers.
(defvar nnimap-current-server nil) ;; Current server
(defvar nnimap-server-buffer nil) ;; Current servers' buffer

\f

(nnoo-define-basics nnimap)

;; Utility functions:

(defsubst nnimap-get-server-buffer (server)
  "Return buffer for SERVER, if nil use current server."
  (cadr (assoc (or server nnimap-current-server) nnimap-server-buffer-alist)))

(defun nnimap-remove-server-from-buffer-alist (server list)
  "Remove SERVER from LIST."
  (let (l)
    (dolist (e list)
      (unless (equal server (car-safe e))
        (push e l)))
    l))

(defun nnimap-possibly-change-server (server)
  "Return buffer for SERVER, changing the current server as a side-effect.
If SERVER is nil, uses the current server."
  (setq nnimap-current-server (or server nnimap-current-server)
        nnimap-server-buffer (nnimap-get-server-buffer nnimap-current-server)))

(defun nnimap-verify-uidvalidity (group server)
  "Verify stored uidvalidity match current one in GROUP on SERVER."
  (let* ((gnusgroup (gnus-group-prefixed-name
                     group (gnus-server-to-method
                            (format "nnimap:%s" server))))
         (new-uidvalidity (imap-mailbox-get 'uidvalidity))
         (old-uidvalidity (gnus-group-get-parameter gnusgroup 'uidvalidity))
         (dir (file-name-as-directory (expand-file-name nnimap-directory)))
         (nameuid (nnheader-translate-file-chars
                   (concat nnimap-nov-file-name
                           (if (equal server "")
                               "unnamed"
                             server) "." group "." old-uidvalidity
                           nnimap-nov-file-name-suffix) t))
         (file (if (or nnmail-use-long-file-names
                       (file-exists-p (expand-file-name nameuid dir)))
                   (expand-file-name nameuid dir)
                 (expand-file-name
                  (mm-encode-coding-string
                   (nnheader-replace-chars-in-string nameuid ?. ?/)
                   nnmail-pathname-coding-system)
                  dir))))
    (if old-uidvalidity
        (if (not (equal old-uidvalidity new-uidvalidity))
            ;; uidvalidity clash
            (gnus-delete-file file)
          (gnus-group-set-parameter gnusgroup 'uidvalidity new-uidvalidity)
          t)
      (gnus-group-add-parameter gnusgroup (cons 'uidvalidity new-uidvalidity))
      t)))

(defun nnimap-before-find-minmax-bugworkaround ()
  "Function called before iterating through mailboxes with
`nnimap-find-minmax-uid'."
  (when nnimap-need-unselect-to-notice-new-mail
    ;; XXX this is for UoW imapd problem, it doesn't notice new mail in
    ;; currently selected mailbox without a re-select/examine.
    (or (null (imap-current-mailbox nnimap-server-buffer))
        (imap-mailbox-unselect nnimap-server-buffer))))

(defun nnimap-find-minmax-uid (group &optional examine)
  "Find lowest and highest active article number in GROUP.
If EXAMINE is non-nil the group is selected read-only."
  (with-current-buffer nnimap-server-buffer
    (when (or (string= group (imap-current-mailbox))
              (imap-mailbox-select group examine))
      (let (minuid maxuid)
        (when (> (imap-mailbox-get 'exists) 0)
          (imap-fetch-safe '("1,*" . "1,*:*") "UID" nil 'nouidfetch)
          (imap-message-map (lambda (uid Uid)
                              (setq minuid (if minuid (min minuid uid) uid)
                                    maxuid (if maxuid (max maxuid uid) uid)))
                            'UID))
        (list (imap-mailbox-get 'exists) minuid maxuid)))))

(defun nnimap-possibly-change-group (group &optional server)
  "Make GROUP the current group, and SERVER the current server."
  (when (nnimap-possibly-change-server server)
    (with-current-buffer nnimap-server-buffer
      (if (or (null group) (imap-current-mailbox-p group))
          imap-current-mailbox
        (if (imap-mailbox-select group)
            (if (or (nnimap-verify-uidvalidity
                     group (or server nnimap-current-server))
                    (zerop (imap-mailbox-get 'exists group))
                    t ;; for OGnus to see if ignoring uidvalidity
                    ;; changes has any bad effects.
                    (yes-or-no-p
                     (format
                      "nnimap: Group %s is not uidvalid.  Continue? " group)))
                imap-current-mailbox
              (imap-mailbox-unselect)
              (error "nnimap: Group %s is not uid-valid" group))
          (nnheader-report 'nnimap (imap-error-text)))))))

(defun nnimap-replace-whitespace (string)
  "Return STRING with all whitespace replaced with space."
  (when string
    (while (string-match "[\r\n\t]+" string)
      (setq string (replace-match " " t t string)))
    string))

;; Required backend functions

(defun nnimap-retrieve-headers-progress ()
  "Hook to insert NOV line for current article into `nntp-server-buffer'."
  (and (numberp nnmail-large-newsgroup)
       (zerop (% (incf nnimap-counter) nnimap-progress-how-often))
       (> nnimap-length nnmail-large-newsgroup)
       (nnheader-message 6 "nnimap: Retrieving headers... %c"
                         (nth (/ (% nnimap-counter
                                    (* (length nnimap-progress-chars)
                                       nnimap-progress-how-often))
                                 nnimap-progress-how-often)
                              nnimap-progress-chars)))
  (with-current-buffer nntp-server-buffer
    (let (headers lines chars uid mbx)
      (with-current-buffer nnimap-server-buffer
        (setq uid imap-current-message
              mbx imap-current-mailbox
              headers (if (imap-capability 'IMAP4rev1)
                           ;; xxx don't just use car? alist doesn't contain
                           ;; anything else now, but it might...
                           (nth 2 (car (imap-message-get uid 'BODYDETAIL)))
                        (imap-message-get uid 'RFC822.HEADER))
              lines (imap-body-lines (imap-message-body imap-current-message))
              chars (imap-message-get imap-current-message 'RFC822.SIZE)))
      (nnheader-insert-nov
       ;; At this stage, we only have bytes, so let's use unibyte buffers
       ;; to make it more clear.
       (mm-with-unibyte-buffer
         (buffer-disable-undo)
         ;; headers can be nil if article is write-only
         (when headers (insert headers))
         (let ((head (nnheader-parse-naked-head uid)))
           (mail-header-set-number head uid)
           (mail-header-set-chars head chars)
           (mail-header-set-lines head lines)
           (mail-header-set-xref
            head (format "%s %s:%d" (system-name) mbx uid))
           head))))))

(defun nnimap-retrieve-which-headers (articles fetch-old)
  "Get a range of articles to fetch based on ARTICLES and FETCH-OLD."
  (with-current-buffer nnimap-server-buffer
    (if (numberp (car-safe articles))
        (imap-search
         (concat "UID "
                 (imap-range-to-message-set
                  (gnus-compress-sequence
                   (append (gnus-uncompress-sequence
                            (and fetch-old
                                 (cons (if (numberp fetch-old)
                                           (max 1 (- (car articles) fetch-old))
                                         1)
                                       (1- (car articles)))))
                           articles)))))
      (mapcar (lambda (msgid)
                (imap-search
                 (format "HEADER Message-Id \"%s\"" msgid)))
              articles))))

(defun nnimap-group-overview-filename (group server)
  "Make file name for GROUP on SERVER."
  (let* ((dir (file-name-as-directory (expand-file-name nnimap-directory)))
         (uidvalidity (gnus-group-get-parameter
                       (gnus-group-prefixed-name
                        group (gnus-server-to-method
                               (format "nnimap:%s" server)))
                       'uidvalidity))
         (name (nnheader-translate-file-chars
                (concat nnimap-nov-file-name
                        (if (equal server "")
                            "unnamed"
                          server) "." group nnimap-nov-file-name-suffix) t))
         (nameuid (nnheader-translate-file-chars
                   (concat nnimap-nov-file-name
                           (if (equal server "")
                               "unnamed"
                             server) "." group "." uidvalidity
                           nnimap-nov-file-name-suffix) t))
         (oldfile (if (or nnmail-use-long-file-names
                          (file-exists-p (expand-file-name name dir)))
                      (expand-file-name name dir)
                    (expand-file-name
                     (mm-encode-coding-string
                      (nnheader-replace-chars-in-string name ?. ?/)
                      nnmail-pathname-coding-system)
                     dir)))
         (newfile (if (or nnmail-use-long-file-names
                          (file-exists-p (expand-file-name nameuid dir)))
                      (expand-file-name nameuid dir)
                    (expand-file-name
                     (mm-encode-coding-string
                      (nnheader-replace-chars-in-string nameuid ?. ?/)
                      nnmail-pathname-coding-system)
                     dir))))
    (when (and (file-exists-p oldfile) (not (file-exists-p newfile)))
      (message "nnimap: Upgrading novcache filename...")
      (sit-for 1)
      (gnus-make-directory (file-name-directory newfile))
      (unless (ignore-errors (rename-file oldfile newfile) t)
        (if (ignore-errors (copy-file oldfile newfile) t)
            (delete-file oldfile)
          (error "Can't rename `%s' to `%s'" oldfile newfile))))
    newfile))

(defun nnimap-retrieve-headers-from-file (group server)
  (with-current-buffer nntp-server-buffer
    (let ((nov (nnimap-group-overview-filename group server)))
      (when (file-exists-p nov)
        (mm-insert-file-contents nov)
        (set-buffer-modified-p nil)
        (let ((min (ignore-errors (goto-char (point-min))
                                  (read (current-buffer))))
              (max (ignore-errors (goto-char (point-max))
                                  (forward-line -1)
                                  (read (current-buffer)))))
          (if (and (numberp min) (numberp max))
              (cons min max)
            ;; junk, remove it, it's saved later
            (erase-buffer)
            nil))))))

(defun nnimap-retrieve-headers-from-server (articles group server)
  (with-current-buffer nnimap-server-buffer
    (let ((imap-fetch-data-hook '(nnimap-retrieve-headers-progress))
          (nnimap-length (gnus-range-length articles))
          (nnimap-counter 0))
      (imap-fetch (imap-range-to-message-set articles)
                  (concat "(UID RFC822.SIZE BODY "
                          (let ((headers
                                 (append '(Subject From Date Message-Id
                                                   References In-Reply-To Xref)
                                         (copy-sequence
                                          nnmail-extra-headers))))
                            (if (imap-capability 'IMAP4rev1)
                                (format "BODY.PEEK[HEADER.FIELDS %s])" headers)
                              (format "RFC822.HEADER.LINES %s)" headers)))))
      (with-current-buffer nntp-server-buffer
        (sort-numeric-fields 1 (point-min) (point-max)))
      (and (numberp nnmail-large-newsgroup)
           (> nnimap-length nnmail-large-newsgroup)
           (nnheader-message 6 "nnimap: Retrieving headers...done")))))

(defun nnimap-dont-use-nov-p (group server)
  (or gnus-nov-is-evil nnimap-nov-is-evil
      (unless (and (gnus-make-directory
                    (file-name-directory
                     (nnimap-group-overview-filename group server)))
                   (file-writable-p
                    (nnimap-group-overview-filename group server)))
        (message "nnimap: Nov cache not writable, %s"
                 (nnimap-group-overview-filename group server)))))

(deffoo nnimap-retrieve-headers (articles &optional group server fetch-old)
  (when (nnimap-possibly-change-group group server)
    (with-current-buffer nntp-server-buffer
      (erase-buffer)
      (if (nnimap-dont-use-nov-p group server)
          (nnimap-retrieve-headers-from-server
           (gnus-compress-sequence articles) group server)
        (let (uids cached low high)
          (when (setq uids (nnimap-retrieve-which-headers articles fetch-old)
                      low (car uids)
                      high (car (last uids)))
            (if (setq cached (nnimap-retrieve-headers-from-file group server))
                (progn
                  ;; fetch articles with uids before cache block
                  (when (< low (car cached))
                    (goto-char (point-min))
                    (nnimap-retrieve-headers-from-server
                     (cons low (1- (car cached))) group server))
                  ;; fetch articles with uids after cache block
                  (when (> high (cdr cached))
                    (goto-char (point-max))
                    (nnimap-retrieve-headers-from-server
                     (cons (1+ (cdr cached)) high) group server))
                  (when nnimap-prune-cache
                    ;; remove nov's for articles which has expired on server
                    (goto-char (point-min))
                    (dolist (uid (gnus-set-difference articles uids))
                      (when (re-search-forward (format "^%d\t" uid) nil t)
                        (gnus-delete-line)))))
              ;; nothing cached, fetch whole range from server
              (nnimap-retrieve-headers-from-server
               (cons low high) group server))
            (when (buffer-modified-p)
              (nnmail-write-region
               (point-min) (point-max)
               (nnimap-group-overview-filename group server) nil 'nomesg))
            (nnheader-nov-delete-outside-range low high))))
      'nov)))

(defun nnimap-open-connection (server)
  ;; Note: `nnimap-open-server' that calls this function binds
  ;; `imap-logout-timeout' to `nnimap-logout-timeout'.
  (if (not (imap-open nnimap-address nnimap-server-port nnimap-stream
                      nnimap-authenticator nnimap-server-buffer))
      (nnheader-report 'nnimap "Can't open connection to server %s" server)
    (unless (or (imap-capability 'IMAP4 nnimap-server-buffer)
                (imap-capability 'IMAP4rev1 nnimap-server-buffer))
      (imap-close nnimap-server-buffer)
      (nnheader-report 'nnimap "Server %s is not IMAP4 compliant" server))
    (let* ((list (progn (gnus-message 7 "Parsing authinfo file `%s'."
                                      nnimap-authinfo-file)
                        (netrc-parse nnimap-authinfo-file)))
           (port (if nnimap-server-port
                     (int-to-string nnimap-server-port)
                   "imap"))
           (user (or
                  (auth-source-user-or-password "login" server port) ; this is preferred to netrc-*
                  (netrc-machine-user-or-password
                   "login"
                   list
                   (list server
                         (or nnimap-server-address
                             nnimap-address))
                   (list port)
                   (list "imap" "imaps" "143" "993"))))
           (passwd (or
                    (auth-source-user-or-password "password" server port) ; this is preferred to netrc-*
                    (netrc-machine-user-or-password
                     "password"
                     list
                     (list server
                           (or nnimap-server-address
                               nnimap-address))
                     (list port)
                     (list "imap" "imaps" "143" "993")))))
      (if (imap-authenticate user passwd nnimap-server-buffer)
          (prog2
              (setq nnimap-server-buffer-alist
                    (nnimap-remove-server-from-buffer-alist
                     server
                     nnimap-server-buffer-alist))
              (push (list server nnimap-server-buffer)
                    nnimap-server-buffer-alist)
            (imap-id nnimap-id nnimap-server-buffer)
            (nnimap-possibly-change-server server))
        (imap-close nnimap-server-buffer)
        (kill-buffer nnimap-server-buffer)
        (nnheader-report 'nnimap "Could not authenticate to %s" server)))))

(deffoo nnimap-open-server (server &optional defs)
  (nnheader-init-server-buffer)
  (if (nnimap-server-opened server)
      t
    (unless (assq 'nnimap-server-buffer defs)
      (push (list 'nnimap-server-buffer (concat " *nnimap* " server)) defs))
    ;; translate `nnimap-server-address' to `nnimap-address' in defs
    ;; for people that configured nnimap with a very old version
    (unless (assq 'nnimap-address defs)
      (if (assq 'nnimap-server-address defs)
          (push (list 'nnimap-address
                      (cadr (assq 'nnimap-server-address defs))) defs)
        (push (list 'nnimap-address server) defs)))
    (nnoo-change-server 'nnimap server defs)
    (or nnimap-server-buffer
        (setq nnimap-server-buffer (cadr (assq 'nnimap-server-buffer defs))))
    (with-current-buffer (get-buffer-create nnimap-server-buffer)
      (nnoo-change-server 'nnimap server defs))
    (let ((imap-logout-timeout nnimap-logout-timeout))
      (or (and nnimap-server-buffer
               (imap-opened nnimap-server-buffer)
               (if (with-current-buffer nnimap-server-buffer
                     (memq imap-state '(auth selected examine)))
                   t
                 (imap-close nnimap-server-buffer)
                 (nnimap-open-connection server)))
          (nnimap-open-connection server)))))

(deffoo nnimap-server-opened (&optional server)
  "Whether SERVER is opened.
If SERVER is the current virtual server, and the connection to the
physical server is alive, this function return a non-nil value.  If
SERVER is nil, it is treated as the current server."
  ;; clean up autologouts??
  (and (or server nnimap-current-server)
       (nnoo-server-opened 'nnimap (or server nnimap-current-server))
       (imap-opened (nnimap-get-server-buffer server))))

(deffoo nnimap-close-server (&optional server)
  "Close connection to server and free all resources connected to it.
Return nil if the server couldn't be closed for some reason."
  (let ((server (or server nnimap-current-server))
        (imap-logout-timeout nnimap-logout-timeout))
    (when (or (nnimap-server-opened server)
              (imap-opened (nnimap-get-server-buffer server)))
      (imap-close (nnimap-get-server-buffer server))
      (kill-buffer (nnimap-get-server-buffer server))
      (setq nnimap-server-buffer nil
            nnimap-current-server nil
            nnimap-server-buffer-alist
            (nnimap-remove-server-from-buffer-alist
             server
             nnimap-server-buffer-alist)))
    (nnoo-close-server 'nnimap server)))

(deffoo nnimap-request-close ()
  "Close connection to all servers and free all resources that the backend have reserved.
All buffers that have been created by that
backend should be killed.  (Not the nntp-server-buffer, though.) This
function is generally only called when Gnus is shutting down."
  (mapc (lambda (server) (nnimap-close-server (car server)))
        nnimap-server-buffer-alist)
  (setq nnimap-server-buffer-alist nil))

(deffoo nnimap-status-message (&optional server)
  "This function returns the last error message from server."
  (when (nnimap-possibly-change-server server)
    (nnoo-status-message 'nnimap server)))

;; We used to use a string-as-multibyte here, but it is really incorrect.
;; This function is used when we're about to insert a unibyte string
;; into a potentially multibyte buffer.  The string is either an article
;; header or body (or both?), undecoded.  When Emacs is asked to convert
;; a unibyte string to multibyte, it may either use the equivalent of
;; nothing (e.g. non-Mule XEmacs), string-make-unibyte (i.e. decode using
;; locale), string-as-multibyte (decode using emacs-internal coding system)
;; or string-to-multibyte (keep the data undecoded as a sequence of bytes).
;; Only the last one preserves the data such that we can reliably later on
;; decode the text using the mime info.
(defalias 'nnimap-demule 'mm-string-to-multibyte)

(defun nnimap-make-callback (article gnus-callback buffer)
  "Return a callback function."
  `(lambda ()
     (nnimap-callback ,article ,gnus-callback ,buffer)))

(defun nnimap-callback (article gnus-callback buffer)
  (when (eq article (imap-current-message))
    (remove-hook 'imap-fetch-data-hook
                 (nnimap-make-callback article gnus-callback buffer))
    (with-current-buffer buffer
      (insert
       (with-current-buffer nnimap-server-buffer
         (nnimap-demule
          (if (imap-capability 'IMAP4rev1)
              ;; xxx don't just use car? alist doesn't contain
              ;; anything else now, but it might...
              (nth 2 (car (imap-message-get article 'BODYDETAIL)))
            (imap-message-get article 'RFC822)))))
      (nnheader-ms-strip-cr)
      (funcall gnus-callback t))))

(defun nnimap-request-article-part (article part prop &optional
                                            group server to-buffer detail)
  (when (nnimap-possibly-change-group group server)
    (let ((article (if (stringp article)
                       (car-safe (imap-search
                                  (format "HEADER Message-Id \"%s\"" article)
                                  nnimap-server-buffer))
                     article)))
      (when article
        (gnus-message 10 "nnimap: Fetching (part of) article %d from %s..."
                      article (or group imap-current-mailbox
                                  gnus-newsgroup-name))
        (if (not nnheader-callback-function)
            (with-current-buffer (or to-buffer nntp-server-buffer)
              (erase-buffer)
              (let ((data (imap-fetch article part prop nil
                                      nnimap-server-buffer)))
                ;; data can be nil if article is write-only
                (when data
                  (insert (nnimap-demule (if detail
                                             (nth 2 (car data))
                                           data)))))
              (nnheader-ms-strip-cr)
              (gnus-message
               10 "nnimap: Fetching (part of) article %d from %s...done"
               article (or group imap-current-mailbox gnus-newsgroup-name))
              (if (bobp)
                  (nnheader-report 'nnimap "No such article %d in %s: %s"
                                   article (or group imap-current-mailbox
                                               gnus-newsgroup-name)
                                   (imap-error-text nnimap-server-buffer))
                (cons group article)))
          (add-hook 'imap-fetch-data-hook
                    (nnimap-make-callback article
                                          nnheader-callback-function
                                          nntp-server-buffer))
          (imap-fetch-asynch article part nil nnimap-server-buffer)
          (cons group article))))))

(deffoo nnimap-asynchronous-p ()
  t)

(deffoo nnimap-request-article (article &optional group server to-buffer)
  (if (imap-capability 'IMAP4rev1 nnimap-server-buffer)
      (nnimap-request-article-part
       article "BODY.PEEK[]" 'BODYDETAIL group server to-buffer 'detail)
    (nnimap-request-article-part
     article "RFC822.PEEK" 'RFC822 group server to-buffer)))

(deffoo nnimap-request-head (article &optional group server to-buffer)
  (if (imap-capability 'IMAP4rev1 nnimap-server-buffer)
      (nnimap-request-article-part
       article "BODY.PEEK[HEADER]" 'BODYDETAIL group server to-buffer 'detail)
    (nnimap-request-article-part
     article "RFC822.HEADER" 'RFC822.HEADER group server to-buffer)))

(deffoo nnimap-request-body (article &optional group server to-buffer)
  (if (imap-capability 'IMAP4rev1 nnimap-server-buffer)
      (nnimap-request-article-part
       article "BODY.PEEK[TEXT]" 'BODYDETAIL group server to-buffer 'detail)
    (nnimap-request-article-part
     article "RFC822.TEXT.PEEK" 'RFC822.TEXT group server to-buffer)))

(deffoo nnimap-request-group (group &optional server fast)
  (nnimap-request-update-info-internal
   group
   (gnus-get-info (gnus-group-prefixed-name
                   group (gnus-server-to-method (format "nnimap:%s" server))))
   server)
  (when (nnimap-possibly-change-group group server)
    (nnimap-before-find-minmax-bugworkaround)
    (let (info)
      (cond (fast group)
            ((null (setq info (nnimap-find-minmax-uid group t)))
             (nnheader-report 'nnimap "Could not get active info for %s"
                              group))
            (t
             (nnheader-insert "211 %d %d %d %s\n" (or (nth 0 info) 0)
                              (max 1 (or (nth 1 info) 1))
                              (or (nth 2 info) 0) group)
             (nnheader-report 'nnimap "Group %s selected" group)
             t)))))

(defun nnimap-update-unseen (group &optional server)
  "Update the unseen count in `nnimap-mailbox-info'."
  (gnus-sethash
   (gnus-group-prefixed-name group server)
   (let ((old (gnus-gethash-safe (gnus-group-prefixed-name group server)
                                 nnimap-mailbox-info)))
     (list (nth 0 old) (nth 1 old)
           (imap-mailbox-status group 'unseen nnimap-server-buffer)
           (nth 3 old)))
   nnimap-mailbox-info))

(defun nnimap-close-group (group &optional server)
  (with-current-buffer nnimap-server-buffer
    (when (and (imap-opened)
               (nnimap-possibly-change-group group server))
      (nnimap-update-unseen group server)
      (case nnimap-expunge-on-close
        (always (progn
                  (imap-mailbox-expunge nnimap-close-asynchronous)
                  (unless nnimap-dont-close
                    (imap-mailbox-close nnimap-close-asynchronous))))
        (ask (if (and (imap-search "DELETED")
                      (gnus-y-or-n-p (format "Expunge articles in group `%s'? "
                                             imap-current-mailbox)))
                 (progn
                   (imap-mailbox-expunge nnimap-close-asynchronous)
                   (unless nnimap-dont-close
                     (imap-mailbox-close nnimap-close-asynchronous)))
               (imap-mailbox-unselect)))
        (t (imap-mailbox-unselect)))
      (not imap-current-mailbox))))

(defun nnimap-pattern-to-list-arguments (pattern)
  (mapcar (lambda (p)
            (cons (car-safe p) (or (cdr-safe p) p)))
          (if (and (listp pattern)
                   (listp (cdr pattern)))
              pattern
            (list pattern))))

(deffoo nnimap-request-list (&optional server)
  (when (nnimap-possibly-change-server server)
    (with-current-buffer nntp-server-buffer
      (erase-buffer))
    (gnus-message 5 "nnimap: Generating active list%s..."
                  (if (> (length server) 0) (concat " for " server) ""))
    (nnimap-before-find-minmax-bugworkaround)
    (with-current-buffer nnimap-server-buffer
      (dolist (pattern (nnimap-pattern-to-list-arguments nnimap-list-pattern))
        (dolist (mbx (funcall nnimap-request-list-method
                              (cdr pattern) (car pattern)))
          (or (member "\\NoSelect" (imap-mailbox-get 'list-flags mbx))
              (let ((info (nnimap-find-minmax-uid mbx 'examine)))
                (when info
                  (with-current-buffer nntp-server-buffer
                    (insert (format "\"%s\" %d %d y\n"
                                    mbx (or (nth 2 info) 0)
                                    (max 1 (or (nth 1 info) 1)))))))))))
    (gnus-message 5 "nnimap: Generating active list%s...done"
                  (if (> (length server) 0) (concat " for " server) ""))
    t))

(deffoo nnimap-request-post (&optional server)
  (let ((success t))
    (dolist (mbx (message-unquote-tokens
                  (message-tokenize-header
                   (message-fetch-field "Newsgroups") ", ")) success)
      (let ((to-newsgroup (gnus-group-prefixed-name mbx gnus-command-method)))
        (or (gnus-active to-newsgroup)
            (gnus-activate-group to-newsgroup)
            (if (gnus-y-or-n-p (format "No such group: %s.  Create it? "
                                       to-newsgroup))
                (or (and (gnus-request-create-group
                          to-newsgroup gnus-command-method)
                         (gnus-activate-group to-newsgroup nil nil
                                              gnus-command-method))
                    (error "Couldn't create group %s" to-newsgroup)))
            (error "No such group: %s" to-newsgroup))
        (unless (nnimap-request-accept-article mbx (nth 1 gnus-command-method))
          (setq success nil))))))

;; Optional backend functions

(defun nnimap-string-lessp-numerical (s1 s2)
  "Return t if first arg string is less than second in numerical order."
  (cond ((string= s1 s2)
         nil)
        ((> (length s1) (length s2))
         nil)
        ((< (length s1) (length s2))
         t)
        ((< (string-to-number (substring s1 0 1))
            (string-to-number (substring s2 0 1)))
         t)
        ((> (string-to-number (substring s1 0 1))
            (string-to-number (substring s2 0 1)))
         nil)
        (t
         (nnimap-string-lessp-numerical (substring s1 1) (substring s2 1)))))

(deffoo nnimap-retrieve-groups (groups &optional server)
  (when (nnimap-possibly-change-server server)
    (gnus-message 5 "nnimap: Checking mailboxes...")
    (with-current-buffer nntp-server-buffer
      (erase-buffer)
      (nnimap-before-find-minmax-bugworkaround)
      (let (asyncgroups slowgroups)
        (if (null nnimap-retrieve-groups-asynchronous)
            (setq slowgroups groups)
          (dolist (group groups)
            (gnus-message 9 "nnimap: Quickly checking mailbox %s" group)
            (add-to-list (if (gnus-gethash-safe
                              (gnus-group-prefixed-name group server)
                              nnimap-mailbox-info)
                             'asyncgroups
                           'slowgroups)
                         (list group (imap-mailbox-status-asynch
                                      group '(uidvalidity uidnext unseen)
                                      nnimap-server-buffer))))
          (dolist (asyncgroup asyncgroups)
            (let ((group (nth 0 asyncgroup))
                  (tag   (nth 1 asyncgroup))
                  new old)
              (when (imap-ok-p (imap-wait-for-tag tag nnimap-server-buffer))
                (if (or (not (string=
                              (nth 0 (gnus-gethash (gnus-group-prefixed-name
                                                    group server)
                                                   nnimap-mailbox-info))
                              (imap-mailbox-get 'uidvalidity group
                                                nnimap-server-buffer)))
                        (not (string=
                              (nth 1 (gnus-gethash (gnus-group-prefixed-name
                                                    group server)
                                                   nnimap-mailbox-info))
                              (imap-mailbox-get 'uidnext group
                                                nnimap-server-buffer))))
                    (push (list group) slowgroups)
                  (insert (nth 3 (gnus-gethash (gnus-group-prefixed-name
                                                group server)
                                               nnimap-mailbox-info))))))))
        (dolist (group slowgroups)
          (if nnimap-retrieve-groups-asynchronous
              (setq group (car group)))
          (gnus-message 7 "nnimap: Mailbox %s modified" group)
          (imap-mailbox-put 'uidnext nil group nnimap-server-buffer)
          (or (member "\\NoSelect" (imap-mailbox-get 'list-flags group
                                                     nnimap-server-buffer))
              (let* ((info (nnimap-find-minmax-uid group 'examine))
                     (str (format "\"%s\" %d %d y\n" group
                                  (or (nth 2 info) 0)
                                  (max 1 (or (nth 1 info) 1)))))
                (when (> (or (imap-mailbox-get 'recent group
                                               nnimap-server-buffer) 0)
                         0)
                  (push (list (cons group 0)) nnmail-split-history))
                (insert str)
                (when nnimap-retrieve-groups-asynchronous
                  (gnus-sethash
                   (gnus-group-prefixed-name group server)
                   (list (or (imap-mailbox-get
                              'uidvalidity group nnimap-server-buffer)
                             (imap-mailbox-status
                              group 'uidvalidity nnimap-server-buffer))
                         (or (imap-mailbox-get
                              'uidnext group nnimap-server-buffer)
                             (imap-mailbox-status
                              group 'uidnext nnimap-server-buffer))
                         (or (imap-mailbox-get
                              'unseen group nnimap-server-buffer)
                             (imap-mailbox-status
                              group 'unseen nnimap-server-buffer))
                         str)
                   nnimap-mailbox-info)))))))
    (gnus-message 5 "nnimap: Checking mailboxes...done")
    'active))

(deffoo nnimap-request-update-info-internal (group info &optional server)
  (when (nnimap-possibly-change-group group server)
    (when info ;; xxx what does this mean? should we create a info?
      (with-current-buffer nnimap-server-buffer
        (gnus-message 5 "nnimap: Updating info for %s..."
                      (gnus-info-group info))

        (when (nnimap-mark-permanent-p 'read)
          (let (seen unseen)
            ;; read info could contain articles marked unread by other
            ;; imap clients!  we correct this
            (setq unseen (gnus-compress-sequence
                          (imap-search "UNSEEN UNDELETED"))
                  seen (gnus-range-difference (gnus-info-read info) unseen)
                  seen (gnus-range-add seen
                                       (gnus-compress-sequence
                                        (imap-search "SEEN")))
                  seen (if (and (integerp (car seen))
                                (null (cdr seen)))
                           (list (cons (car seen) (car seen)))
                         seen))
            (gnus-info-set-read info seen)))

        (dolist (pred gnus-article-mark-lists)
          (when (or (eq (cdr pred) 'recent)
                    (and (nnimap-mark-permanent-p (cdr pred))
                         (member (nnimap-mark-to-flag (cdr pred))
                                 (imap-mailbox-get 'flags))))
            (gnus-info-set-marks
             info
             (gnus-update-alist-soft
              (cdr pred)
              (gnus-compress-sequence
               (imap-search (nnimap-mark-to-predicate (cdr pred))))
              (gnus-info-marks info))
             t)))

        (when nnimap-importantize-dormant
          ;; nnimap mark dormant article as ticked too (for other clients)
          ;; so we remove that mark for gnus since we support dormant
          (gnus-info-set-marks
           info
           (gnus-update-alist-soft
            'tick
            (gnus-remove-from-range
             (cdr-safe (assoc 'tick (gnus-info-marks info)))
             (cdr-safe (assoc 'dormant (gnus-info-marks info))))
            (gnus-info-marks info))
           t))

        (gnus-message 5 "nnimap: Updating info for %s...done"
                      (gnus-info-group info))

        info))))

(deffoo nnimap-request-type (group &optional article)
  (if (and nnimap-news-groups (string-match nnimap-news-groups group))
      'news
    'mail))

(deffoo nnimap-request-set-mark (group actions &optional server)
  (when (nnimap-possibly-change-group group server)
    (with-current-buffer nnimap-server-buffer
      (let (action)
        (gnus-message 7 "nnimap: Setting marks in %s..." group)
        (while (setq action (pop actions))
          (let ((range (nth 0 action))
                (what  (nth 1 action))
                (cmdmarks (nth 2 action))
                marks)
            ;; bookmark can't be stored (not list/range
            (setq cmdmarks (delq 'bookmark cmdmarks))
            ;; killed can't be stored (not list/range
            (setq cmdmarks (delq 'killed cmdmarks))
            ;; unsent are for nndraft groups only
            (setq cmdmarks (delq 'unsent cmdmarks))
            ;; cache flags are pointless on the server
            (setq cmdmarks (delq 'cache cmdmarks))
            ;; seen flags are local to each gnus
            (setq cmdmarks (delq 'seen cmdmarks))
            ;; recent marks can't be set
            (setq cmdmarks (delq 'recent cmdmarks))
            (when nnimap-importantize-dormant
              ;; flag dormant articles as ticked
              (if (memq 'dormant cmdmarks)
                  (setq cmdmarks (cons 'tick cmdmarks))))
            ;; remove stuff we are forbidden to store
            (mapc (lambda (mark)
                    (if (imap-message-flag-permanent-p
                         (nnimap-mark-to-flag mark))
                        (setq marks (cons mark marks))))
                  cmdmarks)
            (when (and range marks)
              (cond ((eq what 'del)
                     (imap-message-flags-del
                      (imap-range-to-message-set range)
                      (nnimap-mark-to-flag marks nil t)))
                    ((eq what 'add)
                     (imap-message-flags-add
                      (imap-range-to-message-set range)
                      (nnimap-mark-to-flag marks nil t)))
                    ((eq what 'set)
                     (imap-message-flags-set
                      (imap-range-to-message-set range)
                      (nnimap-mark-to-flag marks nil t)))))))
        (gnus-message 7 "nnimap: Setting marks in %s...done" group))))
  nil)

(defun nnimap-split-fancy ()
  "Like the function `nnmail-split-fancy', but uses `nnimap-split-fancy'."
  (let ((nnmail-split-fancy nnimap-split-fancy))
    (nnmail-split-fancy)))

(defun nnimap-split-to-groups (rules)
  ;; tries to match all rules in nnimap-split-rule against content of
  ;; nntp-server-buffer, returns a list of groups that matched.
  (with-current-buffer nntp-server-buffer
    ;; Fold continuation lines.
    (goto-char (point-min))
    (while (re-search-forward "\\(\r?\n[ \t]+\\)+" nil t)
      (replace-match " " t t))
    (if (functionp rules)
        (funcall rules)
      (let (to-groups regrepp)
        (catch 'split-done
          (dolist (rule rules to-groups)
            (let ((group (car rule))
                  (regexp (cadr rule)))
              (goto-char (point-min))
              (when (and (if (stringp regexp)
                             (progn
                               (if (not (stringp group))
                                   (setq group (eval group))
                                 (setq regrepp
                                       (string-match "\\\\[0-9&]" group)))
                               (re-search-forward regexp nil t))
                           (funcall regexp group))
                         ;; Don't enter the article into the same group twice.
                         (not (assoc group to-groups)))
                (push (if regrepp
                          (nnmail-expand-newtext group)
                        group)
                      to-groups)
                (or nnimap-split-crosspost
                    (throw 'split-done to-groups))))))))))

(defun nnimap-assoc-match (key alist)
  (let (element)
    (while (and alist (not element))
      (if (string-match (car (car alist)) key)
          (setq element (car alist)))
      (setq alist (cdr alist)))
    element))

(defun nnimap-split-find-rule (server inbox)
  (if (and (listp nnimap-split-rule) (listp (car nnimap-split-rule))
           (list (cdar nnimap-split-rule)) (listp (cadar nnimap-split-rule)))
      ;; extended format
      (cadr (nnimap-assoc-match inbox (cdr (nnimap-assoc-match
                                            server nnimap-split-rule))))
    nnimap-split-rule))

(defun nnimap-split-find-inbox (server)
  (if (listp nnimap-split-inbox)
      nnimap-split-inbox
    (list nnimap-split-inbox)))

(defun nnimap-split-articles (&optional group server)
  (when (nnimap-possibly-change-server server)
    (with-current-buffer nnimap-server-buffer
      (let (rule inbox removeorig (inboxes (nnimap-split-find-inbox server)))
        ;; iterate over inboxes
        (while (and (setq inbox (pop inboxes))
                    (nnimap-possibly-change-group inbox)) ;; SELECT
          ;; find split rule for this server / inbox
          (when (setq rule (nnimap-split-find-rule server inbox))
            ;; iterate over articles
            (dolist (article (imap-search nnimap-split-predicate))
              (when (if (if (eq nnimap-split-download-body 'default)
                            nnimap-split-download-body-default
                          nnimap-split-download-body)
                        (and (nnimap-request-article article)
                             (with-current-buffer nntp-server-buffer (mail-narrow-to-head)))
                      (nnimap-request-head article))
                ;; copy article to right group(s)
                (setq removeorig nil)
                (dolist (to-group (nnimap-split-to-groups rule))
                  (cond ((eq to-group 'junk)
                         (message "IMAP split removed %s:%s:%d" server inbox
                                  article)
                         (setq removeorig t))
                        ((imap-message-copy (number-to-string article)
                                            to-group nil 'nocopyuid)
                         (message "IMAP split moved %s:%s:%d to %s" server
                                  inbox article to-group)
                         (setq removeorig t)
                         (when nnmail-cache-accepted-message-ids
                           (with-current-buffer nntp-server-buffer
                             (let (msgid)
                               (and (setq msgid
                                          (nnmail-fetch-field "message-id"))
                                    (nnmail-cache-insert msgid
                                                         to-group
                                                         (nnmail-fetch-field "subject"))))))
                         ;; Add the group-art list to the history list.
                         (push (list (cons to-group 0)) nnmail-split-history))
                        (t
                         (message "IMAP split failed to move %s:%s:%d to %s"
                                  server inbox article to-group))))
                (if (if (eq nnimap-split-download-body 'default)
                        nnimap-split-download-body-default
                      nnimap-split-download-body)
                    (widen))
                ;; remove article if it was successfully copied somewhere
                (and removeorig
                     (imap-message-flags-add (format "%d" article)
                                             "\\Seen \\Deleted")))))
          (when (imap-mailbox-select inbox) ;; just in case
            ;; todo: UID EXPUNGE (if available) to remove splitted articles
            (imap-mailbox-expunge)
            (imap-mailbox-close)))
        (when nnmail-cache-accepted-message-ids
          (nnmail-cache-close))
        t))))

(deffoo nnimap-request-scan (&optional group server)
  (nnimap-split-articles group server))

(deffoo nnimap-request-newgroups (date &optional server)
  (when (nnimap-possibly-change-server server)
    (with-current-buffer nntp-server-buffer
      (gnus-message 5 "nnimap: Listing subscribed mailboxes%s%s..."
                    (if (> (length server) 0) " on " "") server)
      (erase-buffer)
      (nnimap-before-find-minmax-bugworkaround)
      (dolist (pattern (nnimap-pattern-to-list-arguments
                        nnimap-list-pattern))
        (dolist (mbx (imap-mailbox-lsub (cdr pattern) (car pattern) nil
                                        nnimap-server-buffer))
          (or (catch 'found
                (dolist (mailbox (imap-mailbox-get 'list-flags mbx
                                                   nnimap-server-buffer))
                  (if (string= (downcase mailbox) "\\noselect")
                      (throw 'found t)))
                nil)
              (let ((info (nnimap-find-minmax-uid mbx 'examine)))
                (when info
                  (insert (format "\"%s\" %d %d y\n"
                                  mbx (or (nth 2 info) 0)
                                  (max 1 (or (nth 1 info) 1)))))))))
      (gnus-message 5 "nnimap: Listing subscribed mailboxes%s%s...done"
                    (if (> (length server) 0) " on " "") server))
    t))

(deffoo nnimap-request-create-group (group &optional server args)
  (when (nnimap-possibly-change-server server)
    (or (imap-mailbox-status group 'uidvalidity nnimap-server-buffer)
        (imap-mailbox-create group nnimap-server-buffer)
        (nnheader-report 'nnimap "%S"
                         (imap-error-text nnimap-server-buffer)))))

(defun nnimap-time-substract (time1 time2)
  "Return TIME for TIME1 - TIME2."
  (let* ((ms (- (car time1) (car time2)))
         (ls (- (nth 1 time1) (nth 1 time2))))
    (if (< ls 0)
        (list (- ms 1) (+ (expt 2 16) ls))
      (list ms ls))))

(eval-when-compile (require 'parse-time))
(defun nnimap-date-days-ago (daysago)
  "Return date, in format \"3-Aug-1998\", for DAYSAGO days ago."
  (require 'parse-time)
  (let* ((time (nnimap-time-substract (current-time) (days-to-time daysago)))
         (date (format-time-string
                (format "%%d-%s-%%Y"
                        (capitalize (car (rassoc (nth 4 (decode-time time))
                                                 parse-time-months))))
                time)))
    (if (eq ?0 (string-to-char date))
        (substring date 1)
      date)))

(defun nnimap-request-expire-articles-progress ()
  (gnus-message 5 "nnimap: Marking article %d for deletion..."
                imap-current-message))

(defun nnimap-expiry-target (arts group server)
  (unless (eq nnmail-expiry-target 'delete)
    (with-temp-buffer
      (dolist (art arts)
        (nnimap-request-article art group server (current-buffer))
        ;; hints for optimization in `nnimap-request-accept-article'
        (let ((nnimap-current-move-article art)
              (nnimap-current-move-group group)
              (nnimap-current-move-server server))
          (nnmail-expiry-target-group nnmail-expiry-target group))))
    ;; It is not clear if `nnmail-expiry-target' somehow cause the
    ;; current group to be changed or not, so we make sure here.
    (nnimap-possibly-change-group group server)))

;; Notice that we don't actually delete anything, we just mark them deleted.
(deffoo nnimap-request-expire-articles (articles group &optional server force)
  (let ((artseq (gnus-compress-sequence articles)))
    (when (and artseq (nnimap-possibly-change-group group server))
      (with-current-buffer nnimap-server-buffer
        (let ((days (or (and nnmail-expiry-wait-function
                             (funcall nnmail-expiry-wait-function group))
                        nnmail-expiry-wait)))
          (cond ((or force (eq days 'immediate))
                 (let ((oldarts (imap-search
                                 (concat "UID "
                                         (imap-range-to-message-set artseq)))))
                   (when oldarts
                     (nnimap-expiry-target oldarts group server)
                     (when (imap-message-flags-add
                            (imap-range-to-message-set
                             (gnus-compress-sequence oldarts)) "\\Deleted")
                       (setq articles (gnus-set-difference
                                       articles oldarts))))))
                ((and nnimap-search-uids-not-since-is-evil (numberp days))
                 (let* ((all-new-articles
                         (gnus-compress-sequence
                          (imap-search (format "SINCE %s"
                                               (nnimap-date-days-ago days)))))
                        (oldartseq
                         (gnus-range-difference artseq all-new-articles))
                        (oldarts (gnus-uncompress-range oldartseq)))
                   (when oldarts
                     (nnimap-expiry-target oldarts group server)
                     (when (imap-message-flags-add
                            (imap-range-to-message-set oldartseq)
                            "\\Deleted")
                       (setq articles (gnus-set-difference
                                       articles oldarts))))))
                ((numberp days)
                 (let ((oldarts (imap-search
                                 (format nnimap-expunge-search-string
                                         (imap-range-to-message-set artseq)
                                         (nnimap-date-days-ago days))))
                       (imap-fetch-data-hook
                        '(nnimap-request-expire-articles-progress)))
                   (when oldarts
                     (nnimap-expiry-target oldarts group server)
                     (when (imap-message-flags-add
                            (imap-range-to-message-set
                             (gnus-compress-sequence oldarts)) "\\Deleted")
                       (setq articles (gnus-set-difference
                                       articles oldarts)))))))))))
  ;; return articles not deleted
  articles)

(deffoo nnimap-request-move-article (article group server accept-form
                                             &optional last move-is-internal)
  (when (nnimap-possibly-change-server server)
    (save-excursion
      (let ((buf (get-buffer-create " *nnimap move*"))
            (nnimap-current-move-article article)
            (nnimap-current-move-group group)
            (nnimap-current-move-server nnimap-current-server)
            result)
        (gnus-message 10 "nnimap-request-move-article: this is an %s move"
                      (if move-is-internal
                          "internal"
                        "external"))
        ;; request the article only when the move is NOT internal
        (and (or move-is-internal
                 (nnimap-request-article article group server))
             (with-current-buffer buf
               (buffer-disable-undo (current-buffer))
               (insert-buffer-substring nntp-server-buffer)
               (setq result (eval accept-form))
               (kill-buffer buf)
               result)
             (nnimap-possibly-change-group group server)
             (imap-message-flags-add
              (imap-range-to-message-set (list article))
              "\\Deleted" 'silent nnimap-server-buffer))
        result))))

(deffoo nnimap-request-accept-article (group &optional server last)
  (when (nnimap-possibly-change-server server)
    (let (uid)
      (if (setq uid
                (if (string= nnimap-current-server nnimap-current-move-server)
                    ;; moving article within same server, speed it up...
                    (and (nnimap-possibly-change-group
                          nnimap-current-move-group)
                         (imap-message-copy (number-to-string
                                             nnimap-current-move-article)
                                            group 'dontcreate nil
                                            nnimap-server-buffer))
                  (with-current-buffer (current-buffer)
                    (goto-char (point-min))
                    ;; remove any 'From blabla' lines, some IMAP servers
                    ;; reject the entire message otherwise.
                    (when (looking-at "^From[^:]")
                      (delete-region (point) (progn (forward-line) (point))))
                    ;; turn into rfc822 format (\r\n eol's)
                    (while (search-forward "\n" nil t)
                      (replace-match "\r\n"))
                    (when nnmail-cache-accepted-message-ids
                      (nnmail-cache-insert (nnmail-fetch-field "message-id")
                                           group
                                           (nnmail-fetch-field "subject"))))
                  (when (and last nnmail-cache-accepted-message-ids)
                    (nnmail-cache-close))
                  ;; this 'or' is for Cyrus server bug
                  (or (null (imap-current-mailbox nnimap-server-buffer))
                      (imap-mailbox-unselect nnimap-server-buffer))
                  (imap-message-append group (current-buffer) nil nil
                                       nnimap-server-buffer)))
          (cons group (nth 1 uid))
        (nnheader-report 'nnimap (imap-error-text nnimap-server-buffer))))))

(deffoo nnimap-request-delete-group (group force &optional server)
  (when (nnimap-possibly-change-server server)
    (when (string= group (imap-current-mailbox nnimap-server-buffer))
      (imap-mailbox-unselect nnimap-server-buffer))
    (with-current-buffer nnimap-server-buffer
      (if force
          (or (null (imap-mailbox-status group 'uidvalidity))
              (imap-mailbox-delete group))
        ;; UNSUBSCRIBE?
        t))))

(deffoo nnimap-request-rename-group (group new-name &optional server)
  (when (nnimap-possibly-change-server server)
    (imap-mailbox-rename group new-name nnimap-server-buffer)))

(defun nnimap-expunge (mailbox server)
  (when (nnimap-possibly-change-group mailbox server)
    (imap-mailbox-expunge nil nnimap-server-buffer)))

(defun nnimap-acl-get (mailbox server)
  (when (nnimap-possibly-change-server server)
    (and (imap-capability 'ACL nnimap-server-buffer)
         (imap-mailbox-acl-get mailbox nnimap-server-buffer))))

(defun nnimap-acl-edit (mailbox method old-acls new-acls)
  (when (nnimap-possibly-change-server (cadr method))
    (unless (imap-capability 'ACL nnimap-server-buffer)
      (error "Your server does not support ACL editing"))
    (with-current-buffer nnimap-server-buffer
      ;; delete all removed identifiers
      (mapc (lambda (old-acl)
              (unless (assoc (car old-acl) new-acls)
                (or (imap-mailbox-acl-delete (car old-acl) mailbox)
                    (error "Can't delete ACL for %s" (car old-acl)))))
            old-acls)
      ;; set all changed acl's
      (mapc (lambda (new-acl)
              (let ((new-rights (cdr new-acl))
                    (old-rights (cdr (assoc (car new-acl) old-acls))))
                (unless (and old-rights new-rights
                             (string= old-rights new-rights))
                  (or (imap-mailbox-acl-set (car new-acl) new-rights mailbox)
                      (error "Can't set ACL for %s to %s" (car new-acl)
                             new-rights)))))
            new-acls)
      t)))

\f
;;; Internal functions

;;
;; This is confusing.
;;
;; mark      => read, tick, draft, reply etc
;; flag      => "\\Seen", "\\Flagged", "\\Draft", "gnus-expire" etc
;; predicate => "SEEN", "FLAGGED", "DRAFT", "KEYWORD gnus-expire" etc
;;
;; Mark should not really contain 'read since it's not a "mark" in the Gnus
;; world, but we cheat.  Mark == gnus-article-mark-lists + '(read . read).
;;

(defconst nnimap-mark-to-predicate-alist
  (mapcar
   (lambda (pair)                       ; cdr is the mark
     (or (assoc (cdr pair)
                '((read . "SEEN")
                  (tick . "FLAGGED")
                  (draft . "DRAFT")
                  (recent . "RECENT")
                  (reply . "ANSWERED")))
         (cons (cdr pair)
               (format "KEYWORD gnus-%s" (symbol-name (cdr pair))))))
   (cons '(read . read) gnus-article-mark-lists)))

(defun nnimap-mark-to-predicate (pred)
  "Convert a Gnus mark (a symbol such as read, tick, expire) to a IMAP predicate.
This is a string such as \"SEEN\", \"FLAGGED\", \"KEYWORD gnus-expire\",
to be used within a IMAP SEARCH query."
  (cdr (assq pred nnimap-mark-to-predicate-alist)))

(defconst nnimap-mark-to-flag-alist
  (mapcar
   (lambda (pair)
     (or (assoc (cdr pair)
                '((read . "\\Seen")
                  (tick . "\\Flagged")
                  (draft . "\\Draft")
                  (recent . "\\Recent")
                  (reply . "\\Answered")))
         (cons (cdr pair)
               (format "gnus-%s" (symbol-name (cdr pair))))))
   (cons '(read . read) gnus-article-mark-lists)))

(defun nnimap-mark-to-flag-1 (preds)
  (if (and (not (null preds)) (listp preds))
      (cons (nnimap-mark-to-flag (car preds))
            (nnimap-mark-to-flag (cdr preds)))
    (cdr (assoc preds nnimap-mark-to-flag-alist))))

(defun nnimap-mark-to-flag (preds &optional always-list make-string)
  "Convert a Gnus mark (a symbol such as read, tick, expire) to a IMAP flag.
This is a string such as \"\\Seen\", \"\\Flagged\", \"gnus-expire\", to
be used in a STORE FLAGS command."
  (let ((result (nnimap-mark-to-flag-1 preds)))
    (setq result (if (and (or make-string always-list)
                          (not (listp result)))
                     (list result)
                   result))
    (if make-string
        (mapconcat (lambda (flag)
                     (if (listp flag)
                         (mapconcat 'identity flag " ")
                       flag))
                   result " ")
      result)))

(defun nnimap-mark-permanent-p (mark &optional group)
  "Return t if MARK can be permanently (between IMAP sessions) saved on articles, in GROUP."
  (imap-message-flag-permanent-p (nnimap-mark-to-flag mark)))

(when nnimap-debug
  (require 'trace)
  (buffer-disable-undo (get-buffer-create nnimap-debug-buffer))
  (mapc (lambda (f) (trace-function-background f nnimap-debug-buffer))
        '(
          nnimap-possibly-change-server
          nnimap-verify-uidvalidity
          nnimap-find-minmax-uid
          nnimap-before-find-minmax-bugworkaround
          nnimap-possibly-change-group
          ;;nnimap-replace-whitespace
          nnimap-retrieve-headers-progress
          nnimap-retrieve-which-headers
          nnimap-group-overview-filename
          nnimap-retrieve-headers-from-file
          nnimap-retrieve-headers-from-server
          nnimap-retrieve-headers
          nnimap-open-connection
          nnimap-open-server
          nnimap-server-opened
          nnimap-close-server
          nnimap-request-close
          nnimap-status-message
          ;;nnimap-demule
          nnimap-request-article-part
          nnimap-request-article
          nnimap-request-head
          nnimap-request-body
          nnimap-request-group
          nnimap-close-group
          nnimap-pattern-to-list-arguments
          nnimap-request-list
          nnimap-request-post
          nnimap-retrieve-groups
          nnimap-request-update-info-internal
          nnimap-request-type
          nnimap-request-set-mark
          nnimap-split-to-groups
          nnimap-split-find-rule
          nnimap-split-find-inbox
          nnimap-split-articles
          nnimap-request-scan
          nnimap-request-newgroups
          nnimap-request-create-group
          nnimap-time-substract
          nnimap-date-days-ago
          nnimap-request-expire-articles-progress
          nnimap-request-expire-articles
          nnimap-request-move-article
          nnimap-request-accept-article
          nnimap-request-delete-group
          nnimap-request-rename-group
          gnus-group-nnimap-expunge
          gnus-group-nnimap-edit-acl
          gnus-group-nnimap-edit-acl-done
          nnimap-group-mode-hook
          nnimap-mark-to-predicate
          nnimap-mark-to-flag-1
          nnimap-mark-to-flag
          nnimap-mark-permanent-p
          )))

(provide 'nnimap)

;; arch-tag: 2b001f20-3ff9-4094-a0ad-46807c1ba70b
;;; nnimap.el ends here