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

;; Copyright (C) 1996,1997 Free Software Foundation, Inc.

;; Author: Richard L. Pieri <ratinox@peorth.gweep.net>
;; Keywords: mail, pop3
;; Version: 1.3g - epop3mail revisions

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

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

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; 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.

;; -----------------------------------------------------------------
;; 4/8/2000 note: this is a SLIGHTLY modified version of pop3.el
;; made to run with epop3mail.  this is to insure that epop3mail
;; users will have at least SOME working version of pop3.el
;; available to them.
;;
;; flames & suggestions about this particular version should go to
;; franklin lee and NOT to rich pieri.
;;
;; - franklin lee <lee.franklin@worldnet.att.net>
;;

;;; Code:

(require 'mail-utils)
(provide 'pop3)

(defconst pop3-version "1.3g -- epop3mail revisions")

(defvar pop3-maildrop (or user-login-name
                          (getenv "LOGNAME")
                          (getenv "USER")
                          nil)
  "*POP3 maildrop.")
(defvar pop3-mailhost (or (getenv "MAILHOST") nil)
  "*POP3 mailhost.")
(defvar pop3-port 110
  "*POP3 port.")

(defvar pop3-password-required t
  "*Non-nil if a password is required when connecting to POP server.")
(defvar pop3-password nil
  "*Password to use when connecting to POP server.")

(defvar pop3-authentication-scheme 'pass
  "*POP3 authentication scheme.
Defaults to 'pass, for the standard USER/PASS authentication.  Other valid
values are 'apop.")

(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)

(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)
    ;; for debugging only
    (if pop3-debug (switch-to-buffer (process-buffer process)))
    (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)))
    (while (<= n message-count)
      (message (format "Retrieving message %d of %d from %s..."
                       n message-count pop3-mailhost))
      (pop3-retr process n crashbuf)
      (save-excursion
        (set-buffer crashbuf)
        (append-to-file (point-min) (point-max) crashbox)
        (set-buffer (process-buffer process))
        (while (> (buffer-size) 5000)
          (goto-char (point-min))
          (forward-line 50)
          (delete-region (point-min) (point))))
      (pop3-dele process n)
      (setq n (+ 1 n))
      (if pop3-debug (sit-for 1) (sit-for 0.1)))
    (pop3-quit process)
    (kill-buffer crashbuf)))

(defun pop3-open-server (mailhost port)
  "Open TCP connection to MAILHOST.
Returns the process associated with the connection."
  (let ((process-buffer
         (get-buffer-create (format "trace of POP session to %s" mailhost)))
        (process))
    (save-excursion
      (set-buffer process-buffer)
      (erase-buffer)
      (setq pop3-read-point (point-min)))
    (setq process
          (open-network-stream "POP" process-buffer mailhost port))

    ;; next lisp form added 10/1998
    (if (fboundp 'set-process-coding-system)
        (set-process-coding-system process 'raw-text-unix 'no-conversion))

    (let ((response (pop3-read-response process t)))
      (setq pop3-timestamp
            (substring response (or (string-match "<" response) 0)
                       (+ 1 (or (string-match ">" response) -1)))))
    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 command)
  (process-send-string process "\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 (not (search-forward "\r\n" nil t))
        (accept-process-output process 3)
        (goto-char pop3-read-point))
      (setq match-end (point))
      (goto-char pop3-read-point)
      (if (looking-at "-ERR")
          (error (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-string-to-list (string &optional regexp)
  "Chop up a string into a list."
  (let ((list)
        (regexp (or regexp " "))
        (string (if (string-match "\r" string)
                    (substring string 0 (match-beginning 0))
                  string)))
    (store-match-data nil)
    (while string
      (if (string-match regexp string)
          (setq list (cons (substring string 0 (- (match-end 0) 1)) list)
                string (substring string (match-end 0)))
        (setq list (cons string list)
              string nil)))
    (nreverse list)))

(defvar pop3-read-passwd nil)
(defun pop3-read-passwd (prompt)
  (if (not pop3-read-passwd)
      (if (load "passwd" t)
          (setq pop3-read-passwd 'read-passwd)
        (cond ((= 19 emacs-major-version)
               (autoload 'ange-ftp-read-passwd "ange-ftp")
               (setq pop3-read-passwd 'ange-ftp-read-passwd))
              ((= 20 emacs-major-version)
               (autoload 'read-passwd "ange-ftp")
               (setq pop3-read-passwd 'read-passwd)))))
  (funcall pop3-read-passwd prompt))

(defun pop3-clean-region (start end)
  (setq end (set-marker (make-marker) end))
  (save-excursion
    (goto-char start)
    (while (and (< (point) end)
                ;; Modified to regexp search for multiple ^M's
                ;; courtesy of jbowen@mas.co.nz on account of possible
                ;; os/2 processing bug.
                (re-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))

(defun pop3-munge-message-separator (start end)
  "Check to see if a message separator exists.  If not, generate one."
  (if (not (fboundp 'message-make-date))
      (autoload 'message-make-date "message"))
  (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")))
                (date (pop3-string-to-list (or (mail-fetch-field "Date")
                                               (message-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
            (setq date
                  (cond ((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_))))))

;; 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 (format "USER %s not valid." user)))))

(defun pop3-pass (process)
  "Send authentication information to the server."
  (let ((pass pop3-password))
    (if (and pop3-password-required (not pass))
        (setq pass
              (pop3-read-passwd (format "Password for %s: " pop3-maildrop))))
    (if pass
        (progn
          (pop3-send-command process (format "PASS %s" pass))
          (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."
  (if (not (fboundp 'md5)) (autoload 'md5 "md5"))
  (let ((pass pop3-password))
    (if (and pop3-password-required (not pass))
        (setq pass
              (pop3-read-passwd (format "Password for %s: " pop3-maildrop))))
    (if pass
        (let ((hash (md5 (concat pop3-timestamp pass))))
          (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-int (nth 1 (pop3-string-to-list response)))
          (string-to-int (nth 2 (pop3-string-to-list 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))
        (accept-process-output process 3)
        ;; bill@att.com ... to save wear and tear on the heap
        (if (> (buffer-size)  20000) (sleep-for 1))
        (if (> (buffer-size)  50000) (sleep-for 1))
        (if (> (buffer-size) 100000) (sleep-for 1))
        (if (> (buffer-size) 200000) (sleep-for 1))
        (if (> (buffer-size) 500000) (sleep-for 1))
        ;; bill@att.com
        (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-int (nth 1 (pop3-string-to-list 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]

;;; 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]
