;;; vmsproc.el --- run asynchronous VMS subprocesses under Emacs

;; Copyright (C) 1986 Free Software Foundation, Inc.

;; Author: Mukesh Prasad
;; Maintainer: FSF
;; Keywords: vms

;; This file is part of GNU Emacs.

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

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

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

;;; Commentary:

;;; Code:

(defvar display-subprocess-window nil
  "If non-nil, the subprocess window is displayed whenever input is received.")

(defvar command-prefix-string "$ "
  "String to insert to distinguish commands entered by user.")

(defvar subprocess-running nil)
(defvar command-mode-map nil)

(if command-mode-map
    nil
  (setq command-mode-map (make-sparse-keymap))
  (define-key command-mode-map "\C-m" 'command-send-input)
  (define-key command-mode-map "\C-u" 'command-kill-line))

(defun subprocess-input (name str)
  "Handles input from a subprocess.  Called by Emacs."
  (if display-subprocess-window
      (display-buffer subprocess-buf))
  (let ((old-buffer (current-buffer)))
    (set-buffer subprocess-buf)
    (goto-char (point-max))
    (insert str)
    (insert ?\n)
    (set-buffer old-buffer)))

(defun subprocess-exit (name)
  "Called by Emacs upon subprocess exit."
  (setq subprocess-running nil))

(defun start-subprocess ()
  "Spawns an asynchronous subprocess with output redirected to
the buffer *COMMAND*.  Within this buffer, use C-m to send
the last line to the subprocess or to bring another line to
the end."
  (if subprocess-running
      (return t))
  (setq subprocess-buf (get-buffer-create "*COMMAND*"))
  (save-excursion
    (set-buffer subprocess-buf)
    (use-local-map command-mode-map))
  (setq subprocess-running (spawn-subprocess 1 'subprocess-input
					     'subprocess-exit))
  ;; Initialize subprocess so it doesn't panic and die upon
  ;; encountering the first error.
  (and subprocess-running
       (send-command-to-subprocess 1 "ON SEVERE_ERROR THEN CONTINUE")))

(defun subprocess-command-to-buffer (command buffer)
  "Execute COMMAND and redirect output into BUFFER."
  (let (cmd args)
    (setq cmd (substring command 0 (string-match " " command)))
    (setq args (substring command (string-match " " command)))
    (call-process cmd nil buffer nil "*dcl*" args)))
;BUGS: only the output up to the end of the first image activation is trapped.
;  (if (not subprocess-running)
;      (start-subprocess))
;  (save-excursion
;    (set-buffer buffer)
;    (let ((output-filename (concat "SYS$SCRATCH:OUTPUT-FOR-"
;				   (getenv "USER") ".LISTING")))
;      (while (file-exists-p output-filename)
;	(delete-file output-filename))
;      (define-logical-name "SYS$OUTPUT" (concat output-filename "-NEW"))
;      (send-command-to-subprocess 1 command)
;      (send-command-to-subprocess 1 (concat
;				     "RENAME " output-filename
;				     "-NEW " output-filename))
;      (while (not (file-exists-p output-filename))
;	(sleep-for 1))
;      (define-logical-name "SYS$OUTPUT" nil)
;      (insert-file output-filename)
;      (delete-file output-filename))))

(defun subprocess-command ()
  "Starts asynchronous subprocess if not running and switches to its window."
  (interactive)
  (if (not subprocess-running)
      (start-subprocess))
  (and subprocess-running
       (progn (pop-to-buffer subprocess-buf) (goto-char (point-max)))))

(defun command-send-input ()
  "If at last line of buffer, sends the current line to
the spawned subprocess.  Otherwise brings back current
line to the last line for resubmission."
  (interactive)
  (beginning-of-line)
  (let ((current-line (buffer-substring (point)
                                        (progn (end-of-line) (point)))))
    (if (eobp)
	(progn
	  (if (not subprocess-running)
	      (start-subprocess))
	  (if subprocess-running
	      (progn
		(beginning-of-line)
		(send-command-to-subprocess 1 current-line)
		(if command-prefix-string
		    (progn (beginning-of-line) (insert command-prefix-string)))
		(next-line 1))))
      ;; else -- if not at last line in buffer
      (end-of-buffer)
      (backward-char)
      (next-line 1)
      (if (string-equal command-prefix-string
			(substring current-line 0 (length command-prefix-string)))
	  (insert (substring current-line (length command-prefix-string)))
	(insert current-line)))))

(defun command-kill-line()
  "Kills the current line.  Used in command mode."
  (interactive)
  (beginning-of-line)
  (kill-line))

(define-key esc-map "$" 'subprocess-command)

;;; vmsproc.el ends here
