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+;;; multi-eshell.el --- multi-eshell                 -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2023  Thanos Apollo
+
+;; Author: Thanos Apollo <[email protected]>
+;; Keywords: 
+
+;; This program 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.
+
+;; This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;
+
+;;; Code:
+(defgroup multi-eshell nil
+  "Simple support for having multiple shells open."
+  :group 'languages)
+
+(defcustom multi-eshell-shell-function '(eshell)
+  "Command called to create shell"
+  :group 'multi-eshell)
+
+(defcustom multi-eshell-name "*eshell*" "The name of the buffer opened by the shell command."
+  :type 'string
+  :group 'multi-eshell)
+
+(defun multi-eshell-function ()
+  "This function opens the appropriate shell."
+  (eval multi-eshell-shell-function))
+
+(defvar multi-eshell-ring (make-ring 100)
+  "This stores a bunch of buffers, which are shells created by multi-eshell." )
+(setq multi-eshell-index 0 )
+(defvar multi-eshell-last-buffer nil)
+
+(defun multi-eshell-is-current-buffer-current-multi-eshell (&optional ignored)
+  "Checks if current buffer is the current multi-eshell."
+  (eq (current-buffer) (ring-ref multi-eshell-ring multi-eshell-index)))
+
+(defun multi-eshell-switch-to-current-shell (&optional ignored)
+  "Switch to shell buffer."
+  (if (buffer-live-p (ring-ref multi-eshell-ring multi-eshell-index))
+      (switch-to-buffer (ring-ref multi-eshell-ring multi-eshell-index))))
+
+(defun multi-eshell-current-shell (&optional ignored)
+  "Returns the current multi-eshell."
+  (ring-ref multi-eshell-ring multi-eshell-index))
+
+(defun multi-eshell-switch-to-next-live-shell (&optional ignored)
+  "Switches to the next live shell. Creates one if none exists."
+  (interactive "p")
+  (let ((still-looking t)
+	(empty nil))
+    (while (and still-looking (not empty))
+      (if (ring-empty-p multi-eshell-ring)
+	  (progn
+	    (setq empty t)
+	    (multi-eshell 1))
+	(progn
+	  (if (buffer-live-p (ring-ref multi-eshell-ring multi-eshell-index))
+	      (progn
+		(setq multi-eshell-index (+ multi-eshell-index 1))
+		(switch-to-buffer (ring-ref multi-eshell-ring multi-eshell-index))
+		(setq still-looking nil))
+	    (ring-remove multi-eshell-ring multi-eshell-index)))))))
+
+;;;###autoload
+(defun multi-eshell-go-back (&optional ignored)
+  "Switch to buffer multi-eshell-last-buffer."
+  (interactive "p")
+  (if (buffer-live-p multi-eshell-last-buffer)
+      (switch-to-buffer multi-eshell-last-buffer)
+    (message "Last buffer visited before multi-eshell is gone. Nothing to go back to..")))
+
+
+;;;###autoload
+(defun multi-eshell-switch (&optional ignored)
+  "If current buffer is not an multi-eshell, switch to current multi-eshell buffer. Otherwise, switch to next multi-eshell buffer."
+  (interactive "p")
+  (progn
+    (setq multi-eshell-last-buffer (current-buffer))
+    (let ((still-looking t)
+	  (empty nil))
+      (if (ring-empty-p multi-eshell-ring)
+	  (multi-eshell 1)
+	(if (and (buffer-live-p (multi-eshell-current-shell) )
+		 (not (eq (multi-eshell-current-shell) (current-buffer))))
+	    (switch-to-buffer (multi-eshell-current-shell))
+	  (multi-eshell-switch-to-next-live-shell))))))
+
+;;;###autoload
+(defun multi-eshell (&optional numshells)
+  "Creates a shell buffer. If one already exists, this creates a new buffer, with the name '*shell*<n>', where n is chosen by the function generate-new-buffer-name."
+  (interactive "p")
+  (progn
+    (setq multi-eshell-last-buffer (current-buffer))
+    (dotimes (i (if-void 'numshells 1) nil)
+      (let ( (tempname (generate-new-buffer-name "*tempshell*"))
+	     (new-buff-name (generate-new-buffer-name multi-eshell-name))
+	     (localdir default-directory))
+	(if (eq (get-buffer multi-eshell-name) nil)
+	    (progn
+	      (multi-eshell-function)
+	      (ring-insert multi-eshell-ring (current-buffer))
+	      (setq multi-eshell-index (+ multi-eshell-index 1)))
+	  (progn
+	    (interactive)
+	    (multi-eshell-function)
+	    (rename-buffer tempname)
+	    (multi-eshell-function)
+	    (rename-buffer new-buff-name )
+	    (switch-to-buffer tempname)
+	    (rename-buffer multi-eshell-name)
+	    (switch-to-buffer new-buff-name)
+	    (ring-insert multi-eshell-ring (current-buffer) )
+	    (setq multi-eshell-index (+ multi-eshell-index 1))))))))
+
+(defun shell-with-name (name)
+  "Creates a shell with name given by the first argument, and switches to it. If a buffer with name already exists, we simply switch to it."
+  (let ((buffer-of-name (get-buffer name))
+	(tempname (generate-new-buffer-name "*tempshell*") ) )
+    (cond ((bufferp buffer-of-name) ;If the buffer exists, switch to it (assume it is a shell)
+	   (switch-to-buffer name))
+	  ((bufferp (get-buffer multi-eshell-name))
+	   (progn
+	     (multi-eshell-function)
+	     (rename-buffer tempname)
+	     (multi-eshell-function)
+	     (rename-buffer name)
+	     (switch-to-buffer tempname)
+	     (rename-buffer multi-eshell-name)
+	     (switch-to-buffer name)))
+	  (t
+	   (progn
+	     (multi-eshell-function)
+	     (rename-buffer name))))))
+
+(provide 'multi-eshell)
+;;; multi-eshell.el ends here