;;; em-term.el --- running visual commands  -*- lexical-binding:t -*-

;; Copyright (C) 1999-2022 Free Software Foundation, Inc.

;; Author: John Wiegley <johnw@gnu.org>

;; 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 <https://www.gnu.org/licenses/>.

;;; Commentary:

;; At the moment, eshell is stream-based in its interactive input and
;; output.  This means that full-screen commands, such as "vi" or
;; "lynx", will not display correctly.  These are therefore thought of
;; as "visual" programs.  In order to run these programs under Emacs,
;; Eshell uses the term.el package, and invokes them in a separate
;; buffer, giving the illusion that Eshell itself is allowing these
;; visual processes to execute.

;;; Code:

(require 'cl-lib)
(require 'esh-util)
(require 'esh-ext)
(eval-when-compile (require 'eshell))
(require 'term)

;;;###autoload
(progn
(defgroup eshell-term nil
  "This module causes visual commands (e.g., `vi') to be executed by
the `term' package, which comes with Emacs.  This package handles most
of the ANSI control codes, allowing curses-based applications to run
within an Emacs window.  The variable `eshell-visual-commands' defines
which commands are considered visual in nature."
  :tag "Running visual commands"
  :group 'eshell-module))

;;; User Variables:

(defcustom eshell-term-load-hook nil
  "A list of functions to call when loading `eshell-term'."
  :version "24.1"			; removed eshell-term-initialize
  :type 'hook)

(defcustom eshell-visual-commands
  '("vi"                                ; what is going on??
    "screen" "tmux" "top" "htop"        ; ok, a valid program...
    "less" "more"                       ; M-x view-file
    "lynx" "links" "ncftp"              ; eww, ange-ftp
    "mutt" "pine" "tin" "trn" "elm")    ; GNUS!!
  "A list of commands that present their output in a visual fashion.

Commands listed here are run in a term buffer.

See also `eshell-visual-subcommands' and `eshell-visual-options'."
  :type '(repeat string)
  :version "27.1")

(defcustom eshell-visual-subcommands
  nil
  "An alist of subcommands that present their output in a visual fashion.

An alist of the form

  ((COMMAND1 SUBCOMMAND1 SUBCOMMAND2...)
   (COMMAND2 SUBCOMMAND1 ...))

of commands with subcommands that present their output in a
visual fashion.  A likely entry is

  (\"git\" \"log\" \"diff\" \"show\")

because git shows logs and diffs using a pager by default.

See also `eshell-visual-commands' and `eshell-visual-options'."
  :type '(repeat (cons (string :tag "Command")
		       (repeat (string :tag "Subcommand"))))
  :version "24.4")

(defcustom eshell-visual-options
  nil
  "An alist of commands that present their output in a visual fashion.
It has this form:

  ((COMMAND1 OPTION1 OPTION2...)
   (COMMAND2 OPTION1 ...))

For example, a sensible entry would be

  (\"git\" \"--help\" \"--paginate\")

because \"git <command> --help\" shows the command's
documentation with a pager and \"git --paginate <command>\"
always uses a pager for output.

See also `eshell-visual-commands' and `eshell-visual-subcommands'."
  :type '(repeat (cons (string :tag "Command")
		       (repeat (string :tag "Option"))))
  :version "24.4")

;; If you change this from term-term-name, you need to ensure that the
;; value you choose exists in the system's terminfo database.  (Bug#12485)
(defcustom eshell-term-name term-term-name
  "Name to use for the TERM variable when running visual commands.
See `term-term-name' in term.el for more information on how this is
used."
  :version "24.3"	       ; eterm -> term-term-name = eterm-color
  :type 'string)

(defcustom eshell-escape-control-x t
  "If non-nil, allow <C-x> to be handled by Emacs key in visual buffers.
See the variables `eshell-visual-commands',
`eshell-visual-subcommands', and `eshell-visual-options'.  If
this variable is set to nil, <C-x> will send that control
character to the invoked process."
  :type 'boolean)

(defcustom eshell-destroy-buffer-when-process-dies nil
  "If non-nil, term buffers are destroyed after their processes die.
WARNING: Setting this to non-nil may result in unexpected
behavior for short-lived processes, see bug#18108."
  :version "25.1"
  :type 'boolean)

;;; Internal Variables:

(defvar eshell-parent-buffer)

;;; Functions:

(defun eshell-term-initialize ()    ;Called from `eshell-mode' via intern-soft!
  "Initialize the `term' interface code."
  (setq-local eshell-interpreter-alist
	(cons (cons #'eshell-visual-command-p
		    'eshell-exec-visual)
	      eshell-interpreter-alist)))

(defun eshell-visual-command-p (command args)
  "Return non-nil when given a visual command.
If either COMMAND or a subcommand in ARGS (e.g. git log) is a
visual command, returns non-nil."
  (let ((command (file-name-nondirectory command)))
    (and (eshell-interactive-output-p)
         (or (member command eshell-visual-commands)
             (member (car args)
                     (cdr (assoc command eshell-visual-subcommands)))
             (cl-intersection args
                              (cdr (assoc command eshell-visual-options))
                              :test 'string=)))))

(defun eshell-exec-visual (&rest args)
  "Run the specified PROGRAM in a terminal emulation buffer.
ARGS are passed to the program.  At the moment, no piping of input is
allowed."
  (let* (eshell-interpreter-alist
	 (interp (eshell-find-interpreter (car args) (cdr args)))
	 (program (car interp))
	 (args (flatten-tree
		(eshell-stringify-list (append (cdr interp)
					       (cdr args)))))
	 (term-buf
	  (generate-new-buffer
	   (concat "*" (file-name-nondirectory program) "*")))
	 (eshell-buf (current-buffer)))
    (save-current-buffer
      (switch-to-buffer term-buf)
      (term-mode)
      (setq-local term-term-name eshell-term-name)
      (setq-local eshell-parent-buffer eshell-buf)
      (term-exec term-buf program program nil args)
      (let ((proc (get-buffer-process term-buf)))
	(if (and proc (eq 'run (process-status proc)))
	    (set-process-sentinel proc #'eshell-term-sentinel)
	  (error "Failed to invoke visual command")))
      (term-char-mode)
      (if eshell-escape-control-x
          ;; Don't drop existing escape char.
          (let (term-escape-char) (term-set-escape-char ?\C-x)))))
  nil)

;; Process sentinels receive two arguments.
(defun eshell-term-sentinel (proc msg)
  "Clean up the buffer visiting PROC.
If `eshell-destroy-buffer-when-process-dies' is non-nil, destroy
the buffer."
  (term-sentinel proc msg) ;; First call the normal term sentinel.
  (when eshell-destroy-buffer-when-process-dies
    (let ((proc-buf (process-buffer proc)))
      (when (and proc-buf (buffer-live-p proc-buf)
                 (not (eq 'run (process-status proc)))
                 (= (process-exit-status proc) 0))
        (if (eq (current-buffer) proc-buf)
            (let ((buf (and (boundp 'eshell-parent-buffer)
                            eshell-parent-buffer
                            (buffer-live-p eshell-parent-buffer)
                            eshell-parent-buffer)))
              (if buf
                  (switch-to-buffer buf))))
        (kill-buffer proc-buf)))))

;; jww (1999-09-17): The code below will allow Eshell to send input
;; characters directly to the currently running interactive process.
;; However, since this would introduce other problems that would need
;; solutions, I'm going to let it wait until after 2.1.

; (defvar eshell-term-raw-map nil
;   "Keyboard map for sending characters directly to the inferior process.")
; (defvar eshell-term-escape-char nil
;   "Escape character for char-sub-mode of term mode.
; Do not change it directly;  use term-set-escape-char instead.")
; (defvar eshell-term-raw-escape-map nil)

; (defun eshell-term-send-raw-string (chars)
;   (goto-char eshell-last-output-end)
;   (process-send-string (eshell-head-process) chars))

; (defun eshell-term-send-raw ()
;   "Send the last character typed through the terminal-emulator
; without any interpretation."
;   (interactive)
;   ;; Convert `return' to C-m, etc.
;   (if (and (symbolp last-input-event)
;	   (get last-input-event 'ascii-character))
;       (setq last-input-event (get last-input-event 'ascii-character)))
;   (eshell-term-send-raw-string (make-string 1 last-input-event)))

; (defun eshell-term-send-raw-meta ()
;   (interactive)
;   (if (symbolp last-input-event)
;       ;; Convert `return' to C-m, etc.
;       (let ((tmp (get last-input-event 'event-symbol-elements)))
;	(if tmp
;	    (setq last-input-event (car tmp)))
;	(if (symbolp last-input-event)
;	    (progn
;	      (setq tmp (get last-input-event 'ascii-character))
;	      (if tmp (setq last-input-event tmp))))))
;   (eshell-term-send-raw-string (if (and (numberp last-input-event)
;					(> last-input-event 127)
;					(< last-input-event 256))
;				   (make-string 1 last-input-event)
;				 (format "\e%c" last-input-event))))

; (defun eshell-term-mouse-paste (click arg)
;   "Insert the last stretch of killed text at the position clicked on."
;   (interactive "e\nP")
;   ;; Give temporary modes such as isearch a chance to turn off.
;   (run-hooks 'mouse-leave-buffer-hook)
;   (setq this-command 'yank)
;   (eshell-term-send-raw-string
;    (current-kill (cond ((listp arg) 0)
; 		       ((eq arg '-) -1)
; 		       (t (1- arg))))))

; ;; Which would be better:  "\e[A" or "\eOA"? readline accepts either.
; ;; For my configuration it's definitely better \eOA but YMMV. -mm
; ;; For example: vi works with \eOA while elm wants \e[A ...
; (defun eshell-term-send-up    () (interactive) (eshell-term-send-raw-string "\eOA"))
; (defun eshell-term-send-down  () (interactive) (eshell-term-send-raw-string "\eOB"))
; (defun eshell-term-send-right () (interactive) (eshell-term-send-raw-string "\eOC"))
; (defun eshell-term-send-left  () (interactive) (eshell-term-send-raw-string "\eOD"))
; (defun eshell-term-send-home  () (interactive) (eshell-term-send-raw-string "\e[1~"))
; (defun eshell-term-send-end   () (interactive) (eshell-term-send-raw-string "\e[4~"))
; (defun eshell-term-send-prior () (interactive) (eshell-term-send-raw-string "\e[5~"))
; (defun eshell-term-send-next  () (interactive) (eshell-term-send-raw-string "\e[6~"))
; (defun eshell-term-send-del   () (interactive) (eshell-term-send-raw-string "\C-?"))
; (defun eshell-term-send-backspace  () (interactive) (eshell-term-send-raw-string "\C-H"))

; (defun eshell-term-set-escape-char (c)
;   "Change term-escape-char and keymaps that depend on it."
;   (if eshell-term-escape-char
;       (define-key eshell-term-raw-map eshell-term-escape-char 'eshell-term-send-raw))
;   (setq c (make-string 1 c))
;   (define-key eshell-term-raw-map c eshell-term-raw-escape-map)
;   ;; Define standard bindings in eshell-term-raw-escape-map
;   (define-key eshell-term-raw-escape-map "\C-x"
;     (lookup-key (current-global-map) "\C-x"))
;   (define-key eshell-term-raw-escape-map "\C-v"
;     (lookup-key (current-global-map) "\C-v"))
;   (define-key eshell-term-raw-escape-map "\C-u"
;     (lookup-key (current-global-map) "\C-u"))
;   (define-key eshell-term-raw-escape-map c 'eshell-term-send-raw))

; (defun eshell-term-char-mode ()
;   "Switch to char (\"raw\") sub-mode of term mode.
; Each character you type is sent directly to the inferior without
; intervention from Emacs, except for the escape character (usually C-c)."
;   (interactive)
;   (if (not eshell-term-raw-map)
;       (let* ((map (make-keymap))
;	     (esc-map (make-keymap))
;	     (i 0))
;	(while (< i 128)
;	  (define-key map (make-string 1 i) 'eshell-term-send-raw)
;	  (define-key esc-map (make-string 1 i) 'eshell-term-send-raw-meta)
;	  (setq i (1+ i)))
;	(define-key map "\e" esc-map)
;	(setq eshell-term-raw-map map)
;	(setq eshell-term-raw-escape-map
;	      (copy-keymap (lookup-key (current-global-map) "\C-x")))
;	(define-key eshell-term-raw-map [mouse-2] 'eshell-term-mouse-paste)
;	(define-key eshell-term-raw-map [up] 'eshell-term-send-up)
;	(define-key eshell-term-raw-map [down] 'eshell-term-send-down)
;	(define-key eshell-term-raw-map [right] 'eshell-term-send-right)
;	(define-key eshell-term-raw-map [left] 'eshell-term-send-left)
;	(define-key eshell-term-raw-map [delete] 'eshell-term-send-del)
;	(define-key eshell-term-raw-map [backspace] 'eshell-term-send-backspace)
;	(define-key eshell-term-raw-map [home] 'eshell-term-send-home)
;	(define-key eshell-term-raw-map [end] 'eshell-term-send-end)
;	(define-key eshell-term-raw-map [prior] 'eshell-term-send-prior)
;	(define-key eshell-term-raw-map [next] 'eshell-term-send-next)
;	(eshell-term-set-escape-char ?\C-c))))

; (defun eshell-term-line-mode  ()
;   "Switch to line (\"cooked\") sub-mode of eshell-term mode."
;  (use-local-map term-old-mode-map))

(provide 'em-term)

;; Local Variables:
;; generated-autoload-file: "esh-groups.el"
;; End:

;;; em-term.el ends here