;;; pop3.el --- Post Office Protocol (RFC 1460) interface

;; Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
;;   2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.

;; Author: Richard L. Pieri <ratinox@peorth.gweep.net>
;; Maintainer: FSF
;; 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:

;; Most of the standard Post Office Protocol version 3 (RFC 1460) commands
;; are implemented.  The LIST command has not been implemented due to lack
;; of actual usefulness.
;; The optional POP3 command TOP has not been implemented.

;; This program was inspired by Kyle E. Jones's vm-pop program.

;;; Code:

(require 'mail-utils)
(defvar parse-time-months)

(defgroup pop3 nil
  "Post Office Protocol."
  :group 'mail
  :group 'mail-source)

(defcustom pop3-maildrop (or (user-login-name)
			     (getenv "LOGNAME")
			     (getenv "USER"))
  "*POP3 maildrop."
  :version "22.1" ;; Oort Gnus
  :type 'string
  :group 'pop3)

(defcustom pop3-mailhost (or (getenv "MAILHOST") ;; nil -> mismatch
			     "pop3")
  "*POP3 mailhost."
  :version "22.1" ;; Oort Gnus
  :type 'string
  :group 'pop3)

(defcustom pop3-port 110
  "*POP3 port."
  :version "22.1" ;; Oort Gnus
  :type 'number
  :group 'pop3)

(defcustom pop3-password-required t
  "*Non-nil if a password is required when connecting to POP server."
  :version "22.1" ;; Oort Gnus
  :type 'boolean
  :group 'pop3)

;; Should this be customizable?
(defvar pop3-password nil
  "*Password to use when connecting to POP server.")

(defcustom pop3-authentication-scheme 'pass
  "*POP3 authentication scheme.
Defaults to `pass', for the standard USER/PASS authentication.  The other
valid value is 'apop'."
  :type '(choice (const :tag "Normal user/password" pass)
		 (const :tag "APOP" apop))
  :version "22.1" ;; Oort Gnus
  :group 'pop3)

(defcustom pop3-leave-mail-on-server nil
  "*Non-nil if the mail is to be left on the POP server after fetching.

If `pop3-leave-mail-on-server' is non-nil the mail is to be left
on the POP server after fetching.  Note that POP servers maintain
no state information between sessions, so what the client
believes is there and what is actually there may not match up.
If they do not, then you may get duplicate mails or the whole
thing can fall apart and leave you with a corrupt mailbox."
  ;; We can't use the UILD support from XEmacs mail-lib or cvs.m17n.org:
  ;; http://thread.gmane.org/v9lld8fml4.fsf@marauder.physik.uni-ulm.de
  ;; http://thread.gmane.org/b9yy8hzy9ej.fsf@jpl.org
  ;; Any volunteer to re-implement this?
  :version "22.1" ;; Oort Gnus
  :type 'boolean
  :group 'pop3)

(defvar pop3-timestamp nil
  "Timestamp returned when initially connected to the POP server.
Used for APOP authentication.")

(defvar pop3-read-point nil)
(defvar pop3-debug nil)

;; Borrowed from nnheader-accept-process-output in nnheader.el.  See the
;; comments there for explanations about the values.

(eval-and-compile
  (if (and (fboundp 'nnheader-accept-process-output)
	   (boundp 'nnheader-read-timeout))
      (defalias 'pop3-accept-process-output 'nnheader-accept-process-output)
    ;; Borrowed from `nnheader.el':
    (defvar pop3-read-timeout
      (if (string-match "windows-nt\\|os/2\\|emx\\|cygwin"
			(symbol-name system-type))
	  1.0
	0.01)
      "How long pop3 should wait between checking for the end of output.
Shorter values mean quicker response, but are more CPU intensive.")
    (defun pop3-accept-process-output (process)
      (accept-process-output
       process
       (truncate pop3-read-timeout)
       (truncate (* (- pop3-read-timeout
		       (truncate pop3-read-timeout))
		    1000))))))

(defun pop3-movemail (&optional crashbox)
  "Transfer contents of a maildrop to the specified CRASHBOX."
  (or crashbox (setq crashbox (expand-file-name "~/.crashbox")))
  (let* ((process (pop3-open-server pop3-mailhost pop3-port))
	 (crashbuf (get-buffer-create " *pop3-retr*"))
	 (n 1)
	 message-count
	 (pop3-password pop3-password))
    ;; for debugging only
    (if pop3-debug (switch-to-buffer (process-buffer process)))
    ;; query for password
    (if (and pop3-password-required (not pop3-password))
	(setq pop3-password
	      (read-passwd (format "Password for %s: " pop3-maildrop))))
    (cond ((equal 'apop pop3-authentication-scheme)
	   (pop3-apop process pop3-maildrop))
	  ((equal 'pass pop3-authentication-scheme)
	   (pop3-user process pop3-maildrop)
	   (pop3-pass process))
	  (t (error "Invalid POP3 authentication scheme")))
    (setq message-count (car (pop3-stat process)))
    (unwind-protect
	(while (<= n message-count)
	  (message "Retrieving message %d of %d from %s..."
		   n message-count pop3-mailhost)
	  (pop3-retr process n crashbuf)
	  (save-excursion
	    (set-buffer crashbuf)
	    (let ((coding-system-for-write 'binary))
	      (write-region (point-min) (point-max) crashbox t 'nomesg))
	    (set-buffer (process-buffer process))
	    (while (> (buffer-size) 5000)
	      (goto-char (point-min))
	      (forward-line 50)
	      (delete-region (point-min) (point))))
          (unless pop3-leave-mail-on-server
            (pop3-dele process n))
	  (setq n (+ 1 n))
	  (pop3-accept-process-output process))
      (when (and pop3-leave-mail-on-server
		 (> n 1))
	(message "pop3.el doesn't support UIDL.  Setting `pop3-leave-mail-on-server'
to %s might not give the result you'd expect." pop3-leave-mail-on-server)
	(sit-for 1))
      (pop3-quit process))
    (kill-buffer crashbuf))
  t)

(defun pop3-get-message-count ()
  "Return the number of messages in the maildrop."
  (let* ((process (pop3-open-server pop3-mailhost pop3-port))
	 message-count
	 (pop3-password pop3-password))
    ;; for debugging only
    (if pop3-debug (switch-to-buffer (process-buffer process)))
    ;; query for password
    (if (and pop3-password-required (not pop3-password))
	(setq pop3-password
	      (read-passwd (format "Password for %s: " pop3-maildrop))))
    (cond ((equal 'apop pop3-authentication-scheme)
	   (pop3-apop process pop3-maildrop))
	  ((equal 'pass pop3-authentication-scheme)
	   (pop3-user process pop3-maildrop)
	   (pop3-pass process))
	  (t (error "Invalid POP3 authentication scheme")))
    (setq message-count (car (pop3-stat process)))
    (pop3-quit process)
    message-count))

(autoload 'open-tls-stream "tls")
(autoload 'starttls-open-stream "starttls")
(autoload 'starttls-negotiate "starttls") ; avoid warning

(defcustom pop3-stream-type nil
  "*Transport security type for POP3 connexions.
This may be either nil (plain connexion), `ssl' (use an
SSL/TSL-secured stream) or `starttls' (use the starttls mechanism
to turn on TLS security after opening the stream).  However, if
this is nil, `ssl' is assumed for connexions to port
995 (pop3s)."
  :version "23.1" ;; No Gnus
  :group 'pop3
  :type '(choice (const :tag "Plain" nil)
		 (const :tag "SSL/TLS" ssl)
		 (const starttls)))

(defun pop3-open-server (mailhost port)
  "Open TCP connection to MAILHOST on PORT.
Returns the process associated with the connection."
  (let ((coding-system-for-read 'binary)
	(coding-system-for-write 'binary)
	process)
    (save-excursion
      (set-buffer (get-buffer-create (concat " trace of POP session to "
					     mailhost)))
      (erase-buffer)
      (setq pop3-read-point (point-min))
      (setq process
	    (cond
	     ((or (eq pop3-stream-type 'ssl)
		  (and (not pop3-stream-type) (member port '(995 "pop3s"))))
	      ;; gnutls-cli, openssl don't accept service names
	      (if (or (equal port "pop3s")
		      (null port))
		  (setq port 995))
	      (let ((process (open-tls-stream "POP" (current-buffer)
					      mailhost port)))
		(when process
		  ;; There's a load of info printed that needs deleting.
		  (let ((again 't))
		    ;; repeat until
		    ;; - either we received the +OK line
		    ;; - or accept-process-output timed out without getting
		    ;;   anything
		    (while (and again
				(setq again (memq (process-status process)
						  '(open run))))
		      (setq again (pop3-accept-process-output process))
		      (goto-char (point-max))
		      (forward-line -1)
		      (cond ((looking-at "\\+OK")
			     (setq again nil)
			     (delete-region (point-min) (point)))
			    ((not again)
			     (pop3-quit process)
			     (error "POP SSL connexion failed")))))
		  process)))
	     ((eq pop3-stream-type 'starttls)
	      ;; gnutls-cli, openssl don't accept service names
	      (if (equal port "pop3")
		  (setq port 110))
	      ;; Delay STLS until server greeting is read (Bug#7438).
	      (starttls-open-stream "POP" (current-buffer)
				    mailhost (or port 110)))
	     (t
	      (open-network-stream "POP" (current-buffer) mailhost port))))
      (let ((response (pop3-read-response process t)))
	(setq pop3-timestamp
	      (substring response (or (string-match "<" response) 0)
			 (+ 1 (or (string-match ">" response) -1)))))
      (when (eq pop3-stream-type 'starttls)
	(pop3-send-command process "STLS")
	(let ((response (pop3-read-response process t)))
	  (if (and response (string-match "+OK" response))
	      (starttls-negotiate process)
	    (pop3-quit process)
	    (error "POP server doesn't support starttls"))))
      process)))

;; Support functions

(defun pop3-process-filter (process output)
  (save-excursion
    (set-buffer (process-buffer process))
    (goto-char (point-max))
    (insert output)))

(defun pop3-send-command (process command)
  (set-buffer (process-buffer process))
  (goto-char (point-max))
  ;; (if (= (aref command 0) ?P)
  ;;     (insert "PASS <omitted>\r\n")
  ;;   (insert command "\r\n"))
  (setq pop3-read-point (point))
  (goto-char (point-max))
  (process-send-string process (concat command "\r\n")))

(defun pop3-read-response (process &optional return)
  "Read the response from the server.
Return the response string if optional second argument is non-nil."
  (let ((case-fold-search nil)
	match-end)
    (save-excursion
      (set-buffer (process-buffer process))
      (goto-char pop3-read-point)
      (while (and (memq (process-status process) '(open run))
		  (not (search-forward "\r\n" nil t)))
	(pop3-accept-process-output process)
	(goto-char pop3-read-point))
      (setq match-end (point))
      (goto-char pop3-read-point)
      (if (looking-at "-ERR")
	  (error "%s" (buffer-substring (point) (- match-end 2)))
	(if (not (looking-at "+OK"))
	    (progn (setq pop3-read-point match-end) nil)
	  (setq pop3-read-point match-end)
	  (if return
	      (buffer-substring (point) match-end)
	    t)
	  )))))

(defun pop3-clean-region (start end)
  (setq end (set-marker (make-marker) end))
  (save-excursion
    (goto-char start)
    (while (and (< (point) end) (search-forward "\r\n" end t))
      (replace-match "\n" t t))
    (goto-char start)
    (while (and (< (point) end) (re-search-forward "^\\." end t))
      (replace-match "" t t)
      (forward-char)))
  (set-marker end nil))

;; Copied from message-make-date.
(defun pop3-make-date (&optional now)
  "Make a valid date header.
If NOW, use that time instead."
  (require 'parse-time)
  (let* ((now (or now (current-time)))
	 (zone (nth 8 (decode-time now)))
	 (sign "+"))
    (when (< zone 0)
      (setq sign "-")
      (setq zone (- zone)))
    (concat
     (format-time-string "%d" now)
     ;; The month name of the %b spec is locale-specific.  Pfff.
     (format " %s "
	     (capitalize (car (rassoc (nth 4 (decode-time now))
				      parse-time-months))))
     (format-time-string "%Y %H:%M:%S " now)
     ;; We do all of this because XEmacs doesn't have the %z spec.
     (format "%s%02d%02d" sign (/ zone 3600) (/ (% zone 3600) 60)))))

(defun pop3-munge-message-separator (start end)
  "Check to see if a message separator exists.  If not, generate one."
  (save-excursion
    (save-restriction
      (narrow-to-region start end)
      (goto-char (point-min))
      (if (not (or (looking-at "From .?") ; Unix mail
		   (looking-at "\001\001\001\001\n") ; MMDF
		   (looking-at "BABYL OPTIONS:") ; Babyl
		   ))
	  (let* ((from (mail-strip-quoted-names (mail-fetch-field "From")))
		 (tdate (mail-fetch-field "Date"))
		 (date (split-string (or (and tdate
					      (not (string= "" tdate))
					      tdate)
					 (pop3-make-date))
				     " "))
		 (From_))
	    ;; sample date formats I have seen
	    ;; Date: Tue, 9 Jul 1996 09:04:21 -0400 (EDT)
	    ;; Date: 08 Jul 1996 23:22:24 -0400
	    ;; should be
	    ;; Tue Jul 9 09:04:21 1996

	    ;; Fixme: This should use timezone on the date field contents.
	    (setq date
		  (cond ((not date)
			 "Tue Jan 1 00:00:0 1900")
			((string-match "[A-Z]" (nth 0 date))
			 (format "%s %s %s %s %s"
				 (nth 0 date) (nth 2 date) (nth 1 date)
				 (nth 4 date) (nth 3 date)))
			(t
			 ;; this really needs to be better but I don't feel
			 ;; like writing a date to day converter.
			 (format "Sun %s %s %s %s"
				 (nth 1 date) (nth 0 date)
				 (nth 3 date) (nth 2 date)))
			))
	    (setq From_ (format "\nFrom %s  %s\n" from date))
	    (while (string-match "," From_)
	      (setq From_ (concat (substring From_ 0 (match-beginning 0))
				  (substring From_ (match-end 0)))))
	    (goto-char (point-min))
	    (insert From_)
	    (if (search-forward "\n\n" nil t)
		nil
	      (goto-char (point-max))
	      (insert "\n"))
	    (narrow-to-region (point) (point-max))
	    (let ((size (- (point-max) (point-min))))
	      (goto-char (point-min))
	      (widen)
	      (forward-line -1)
	      (insert (format "Content-Length: %s\n" size)))
	    )))))

;; The Command Set

;; AUTHORIZATION STATE

(defun pop3-user (process user)
  "Send USER information to POP3 server."
  (pop3-send-command process (format "USER %s" user))
  (let ((response (pop3-read-response process t)))
    (if (not (and response (string-match "+OK" response)))
	(error "USER %s not valid" user))))

(defun pop3-pass (process)
  "Send authentication information to the server."
  (pop3-send-command process (format "PASS %s" pop3-password))
  (let ((response (pop3-read-response process t)))
    (if (not (and response (string-match "+OK" response)))
	(pop3-quit process))))

(defun pop3-apop (process user)
  "Send alternate authentication information to the server."
  (let ((pass pop3-password))
    (if (and pop3-password-required (not pass))
	(setq pass
	      (read-passwd (format "Password for %s: " pop3-maildrop))))
    (if pass
	(let ((hash (md5 (concat pop3-timestamp pass) nil nil 'binary)))
	  (pop3-send-command process (format "APOP %s %s" user hash))
	  (let ((response (pop3-read-response process t)))
	    (if (not (and response (string-match "+OK" response)))
		(pop3-quit process)))))
    ))

;; TRANSACTION STATE

(defun pop3-stat (process)
  "Return the number of messages in the maildrop and the maildrop's size."
  (pop3-send-command process "STAT")
  (let ((response (pop3-read-response process t)))
    (list (string-to-number (nth 1 (split-string response " ")))
	  (string-to-number (nth 2 (split-string response " "))))
    ))

(defun pop3-list (process &optional msg)
  "Scan listing of available messages.
This function currently does nothing.")

(defun pop3-retr (process msg crashbuf)
  "Retrieve message-id MSG to buffer CRASHBUF."
  (pop3-send-command process (format "RETR %s" msg))
  (pop3-read-response process)
  (let ((start pop3-read-point) end)
    (save-excursion
      (set-buffer (process-buffer process))
      (while (not (re-search-forward "^\\.\r\n" nil t))
	(pop3-accept-process-output process)
	(goto-char start))
      (setq pop3-read-point (point-marker))
      ;; this code does not seem to work for some POP servers...
      ;; and I cannot figure out why not.
      ;;      (goto-char (match-beginning 0))
      ;;      (backward-char 2)
      ;;      (if (not (looking-at "\r\n"))
      ;;	  (insert "\r\n"))
      ;;      (re-search-forward "\\.\r\n")
      (goto-char (match-beginning 0))
      (setq end (point-marker))
      (pop3-clean-region start end)
      (pop3-munge-message-separator start end)
      (save-excursion
	(set-buffer crashbuf)
	(erase-buffer))
      (copy-to-buffer crashbuf start end)
      (delete-region start end)
      )))

(defun pop3-dele (process msg)
  "Mark message-id MSG as deleted."
  (pop3-send-command process (format "DELE %s" msg))
  (pop3-read-response process))

(defun pop3-noop (process msg)
  "No-operation."
  (pop3-send-command process "NOOP")
  (pop3-read-response process))

(defun pop3-last (process)
  "Return highest accessed message-id number for the session."
  (pop3-send-command process "LAST")
  (let ((response (pop3-read-response process t)))
    (string-to-number (nth 1 (split-string response " ")))
    ))

(defun pop3-rset (process)
  "Remove all delete marks from current maildrop."
  (pop3-send-command process "RSET")
  (pop3-read-response process))

;; UPDATE

(defun pop3-quit (process)
  "Close connection to POP3 server.
Tell server to remove all messages marked as deleted, unlock the maildrop,
and close the connection."
  (pop3-send-command process "QUIT")
  (pop3-read-response process t)
  (if process
      (save-excursion
	(set-buffer (process-buffer process))
	(goto-char (point-max))
	(delete-process process))))

;; Summary of POP3 (Post Office Protocol version 3) commands and responses

;;; AUTHORIZATION STATE

;; Initial TCP connection
;; Arguments: none
;; Restrictions: none
;; Possible responses:
;;  +OK [POP3 server ready]

;; USER name
;; Arguments: a server specific user-id (required)
;; Restrictions: authorization state [after unsuccessful USER or PASS
;; Possible responses:
;;  +OK [valid user-id]
;;  -ERR [invalid user-id]

;; PASS string
;; Arguments: a server/user-id specific password (required)
;; Restrictions: authorization state, after successful USER
;; Possible responses:
;;  +OK [maildrop locked and ready]
;;  -ERR [invalid password]
;;  -ERR [unable to lock maildrop]

;; STLS      (RFC 2595)
;; Arguments: none
;; Restrictions: Only permitted in AUTHORIZATION state.
;; Possible responses:
;;  +OK
;;  -ERR

;;; TRANSACTION STATE

;; STAT
;; Arguments: none
;; Restrictions: transaction state
;; Possible responses:
;;  +OK nn mm [# of messages, size of maildrop]

;; LIST [msg]
;; Arguments: a message-id (optional)
;; Restrictions: transaction state; msg must not be deleted
;; Possible responses:
;;  +OK [scan listing follows]
;;  -ERR [no such message]

;; RETR msg
;; Arguments: a message-id (required)
;; Restrictions: transaction state; msg must not be deleted
;; Possible responses:
;;  +OK [message contents follow]
;;  -ERR [no such message]

;; DELE msg
;; Arguments: a message-id (required)
;; Restrictions: transaction state; msg must not be deleted
;; Possible responses:
;;  +OK [message deleted]
;;  -ERR [no such message]

;; NOOP
;; Arguments: none
;; Restrictions: transaction state
;; Possible responses:
;;  +OK

;; LAST
;; Arguments: none
;; Restrictions: transaction state
;; Possible responses:
;;  +OK nn [highest numbered message accessed]

;; RSET
;; Arguments: none
;; Restrictions: transaction state
;; Possible responses:
;;  +OK [all delete marks removed]

;;; UPDATE STATE

;; QUIT
;; Arguments: none
;; Restrictions: none
;; Possible responses:
;;  +OK [TCP connection closed]

(provide 'pop3)

;; arch-tag: 2facc142-1d74-498e-82af-4659b64cac12
;;; pop3.el ends here