;;; telnet.el --- run a telnet session from within an Emacs buffer

;;; Copyright (C) 1985, 1988, 1992 Free Software Foundation, Inc.

;; Author: William F. Schelter
;; Maintainer: FSF

;; 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, 675 Mass Ave, Cambridge, MA 02139, USA.

;;; Commentary:

;; This mode is intended to be used for telnet or rsh to a remode host;
;; `telnet' and `rsh' are the two entry points.  Multiple telnet or rsh
;; sessions are supported.
;;
;; Normally, input is sent to the remote telnet/rsh line-by-line, as you
;; type RET or LFD.  C-c C-c sends a C-c to the remote immediately; 
;; C-c C-z sends C-z immediately.  C-c C-q followed by any character
;; sends that character immediately.
;;
;; All RET characters are filtered out of the output coming back from the
;; remote system.  The mode tries to do other useful translations based
;; on what it sees coming back from the other system before the password
;; query.  It knows about UNIX, ITS, TOPS-20 and Explorer systems.

;;; Code:

;; to do fix software types for lispm:
;; to eval current expression.  Also to try to send escape keys correctly.
;; essentially we'll want the rubout-handler off.

;; filter is simplistic but should be okay for typical shell usage.
;; needs hacking if it is going to deal with asynchronous output in a sane
;; manner

(require 'comint)

(defvar telnet-new-line "\r")
(defvar telnet-mode-map nil)
(defvar telnet-prompt-pattern "^[^#$%>]*[#$%>] *")
(defvar telnet-replace-c-g nil)
(make-variable-buffer-local
 (defvar telnet-remote-echoes t
   "True if the telnet process will echo input."))
(make-variable-buffer-local
 (defvar telnet-interrupt-string "\C-c" "String sent by C-c."))

(defvar telnet-count 0
  "Number of output strings read from the telnet process
while looking for the initial password.")

(defvar telnet-initial-count -50
  "Initial value of `telnet-count'.  Should be set to the negative of the
number of terminal writes telnet will make setting up the host connection.")

(defvar telnet-maximum-count 4
  "Maximum value `telnet-count' can have.
After this many passes, we stop looking for initial setup data.
Should be set to the number of terminal writes telnet will make
rejecting one login and prompting for the again for a username and password.")

(defun telnet-interrupt-subjob ()
  (interactive)
  "Interrupt the program running through telnet on the remote host."
  (send-string nil telnet-interrupt-string))

(defun telnet-c-z ()
  (interactive)
  (send-string nil "\C-z"))

(defun send-process-next-char ()
  (interactive)
  (send-string nil
	       (char-to-string
		(let ((inhibit-quit t))
		  (prog1 (read-char)
		    (setq quit-flag nil))))))

; initialization on first load.
(if telnet-mode-map
    nil
  (setq telnet-mode-map (copy-keymap comint-mode-map))
  (define-key telnet-mode-map "\C-m" 'telnet-send-input)
;  (define-key telnet-mode-map "\C-j" 'telnet-send-input)
  (define-key telnet-mode-map "\C-c\C-q" 'send-process-next-char)
  (define-key telnet-mode-map "\C-c\C-c" 'telnet-interrupt-subjob) 
  (define-key telnet-mode-map "\C-c\C-z" 'telnet-c-z))

;;maybe should have a flag for when have found type
(defun telnet-check-software-type-initialize (string)
  "Tries to put correct initializations in.  Needs work."
  (let ((case-fold-search t))
    (cond ((string-match "unix" string)
	 (setq telnet-prompt-pattern comint-prompt-regexp)
	 (setq telnet-new-line "\n"))
	((string-match "tops-20" string) ;;maybe add telnet-replace-c-g
	 (setq telnet-prompt-pattern  "[@>]*"))
	((string-match "its" string)
	 (setq telnet-prompt-pattern  "^[^*>]*[*>] *"))
	((string-match "explorer" string)  ;;explorer telnet needs work
	 (setq telnet-replace-c-g ?\n))))
  (setq comint-prompt-regexp telnet-prompt-pattern))

(defun telnet-initial-filter (proc string)
  ;For reading up to and including password; also will get machine type.
  (cond ((string-match "No such host" string)
	 (kill-buffer (process-buffer proc))
	 (error "No such host."))
	((string-match "passw" string)
	 (telnet-filter proc string)
	 (let* ((echo-keystrokes 0)
		(password (read-password)))
	   (setq telnet-count 0)
	   (send-string proc (concat password telnet-new-line))))
	(t (telnet-check-software-type-initialize string)
	   (telnet-filter proc string)
	   (cond ((> telnet-count telnet-maximum-count)
		  (set-process-filter proc 'telnet-filter))
		 (t (setq telnet-count (1+ telnet-count)))))))

;; Identical to comint-simple-send, except that it sends telnet-new-line
;; instead of "\n".
(defun telnet-simple-send (proc string)
  (comint-send-string proc string)
  (comint-send-string proc telnet-new-line))

(defun telnet-filter (proc string)
  (let ((at-end
	 (and (eq (process-buffer proc) (current-buffer))
	      (= (point) (point-max)))))
    (save-excursion
      (set-buffer (process-buffer proc))
      (goto-char (process-mark proc))
      (let ((now (point)))
	;; Insert STRING, omitting all C-m characters.
	(let ((index 0) c-m)
	  (while (setq c-m (string-match "\C-m" string index))
	    (insert-before-markers (substring string index c-m))
	    (setq index (1+ c-m)))
	  (insert-before-markers (substring string index)))
	(and telnet-replace-c-g
	     (subst-char-in-region now (point) ?\C-g telnet-replace-c-g)))
;      (if (and (integer-or-marker-p last-input-start)
;	       (marker-position last-input-start)
;	       telnet-remote-echoes)
;	  (delete-region last-input-start last-input-end))
      )
    (if at-end
	(goto-char (point-max)))))

(defun telnet-send-input ()
  (interactive)
;  (comint-send-input telnet-new-line telnet-remote-echoes)
  (comint-send-input)
  (if telnet-remote-echoes
      (delete-region comint-last-input-start
		     comint-last-input-end)))

;;;###autoload
(defun telnet (arg)
  "Open a network login connection to host named HOST (a string).
Communication with HOST is recorded in a buffer *HOST-telnet*.
Normally input is edited in Emacs and sent a line at a time."
  (interactive "sOpen telnet connection to host: ")
  (let ((name (concat arg "-telnet" )))
    (switch-to-buffer (make-comint name "telnet"))
    (set-process-filter (get-process name) 'telnet-initial-filter)
    ;; Don't send the `open' cmd till telnet is ready for it.
    (accept-process-output (get-process name))
    (erase-buffer)
    (send-string  name (concat "open " arg "\n"))
    (telnet-mode)
    (setq comint-input-sender 'telnet-simple-send)
    (setq telnet-count telnet-initial-count)))

(defun telnet-mode ()
  "This mode is for using telnet (or rsh) from a buffer to another host.
It has most of the same commands as comint-mode.
There is a variable ``telnet-interrupt-string'' which is the character
sent to try to stop execution of a job on the remote host.
Data is sent to the remote host when RET is typed.

\\{telnet-mode-map}
"
  (interactive)
  (comint-mode)
  (setq major-mode 'telnet-mode
	mode-name "Telnet"
	comint-prompt-regexp telnet-prompt-pattern)
  (use-local-map telnet-mode-map)
  (run-hooks 'telnet-mode-hook))

;;;###autoload
(defun rsh (arg)
  "Open a network login connection to host named HOST (a string).
Communication with HOST is recorded in a buffer *HOST-rsh*.
Normally input is edited in Emacs and sent a line at a time."
  (interactive "sOpen rsh connection to host: ")
  (require 'shell)
  (let ((name (concat arg "-rsh" )))
    (switch-to-buffer (make-comint name "rsh"))
    (set-process-filter (get-process name) 'telnet-initial-filter)
    (telnet-mode)
    (setq telnet-count -16)))

(defun read-password ()
  (let ((answ "") tem)
    (message "Reading password...")
    (while (prog1 (not (memq (setq tem (read-char)) '(?\C-m ?\n ?\C-g)))
	     (setq quit-flag nil))
      (setq answ (concat answ (char-to-string tem))))
    answ))

(provide 'telnet)

;;; telnet.el ends here
