;;; ob-eshell.el --- Babel Functions for Eshell      -*- lexical-binding: t; -*-

;; Copyright (C) 2018-2024 Free Software Foundation, Inc.

;; Author: stardiviner <numbchild@gmail.com>
;; Maintainer: stardiviner <numbchild@gmail.com>
;; URL: https://github.com/stardiviner/ob-eshell
;; Keywords: literate programming, reproducible research

;; 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:

;; Org Babel support for evaluating Eshell source code.

;;; Code:

(require 'org-macs)
(org-assert-version)

(require 'ob)
(require 'eshell)

(declare-function eshell-send-input "esh-mode"
                  (&optional use-region queue-p no-newline))

(defvar eshell-last-output-start)
(defvar eshell-last-output-end)
(defvar eshell-last-input-end)

(defvar org-babel-default-header-args:eshell '())

(defun org-babel-execute:eshell (body params)
  "Execute a block of Eshell code BODY with PARAMS.
This function is called by `org-babel-execute-src-block'.

The BODY argument is code which can be executed in Eshell.
Eshell allows executing normal shell command and Elisp code.
For more details, see Info node `(eshell) Top'.

The PARAMS argument is passed to
`org-babel-expand-body:generic' (which see)."
  (let* ((session (org-babel-eshell-initiate-session
		   (cdr (assq :session params))))
	 (full-body (org-babel-expand-body:generic
		     body params (org-babel-variable-assignments:eshell params))))
    (if session
	(progn
	  (with-current-buffer session
	    (dolist (line (split-string full-body "\n"))
	      (goto-char eshell-last-output-end)
	      (insert line)
	      (eshell-send-input))
	    ;; get output of last input
	    ;; TODO: collect all output instead of last command's output.
	    (goto-char eshell-last-input-end)
	    (buffer-substring-no-properties (point) eshell-last-output-start)))
      (with-temp-buffer
	(eshell-command full-body t)
	(buffer-string)))))

(defun org-babel-prep-session:eshell (session params)
  "Prepare SESSION according to the header arguments specified in PARAMS."
  (let* ((session (org-babel-eshell-initiate-session session))
	 ;; Eshell session buffer is read from variable `eshell-buffer-name'.
	 (eshell-buffer-name session)
	 (var-lines (org-babel-variable-assignments:eshell params)))
    (call-interactively #'eshell)
    (mapc #'eshell-command var-lines)
    session))

(defun ob-eshell-session-live-p (session)
  "Non-nil if Eshell SESSION exists."
  (get-buffer session))

(defun org-babel-eshell-initiate-session (&optional session _params)
  "Initiate a session named SESSION."
  (when (and session (not (string= session "none")))
    (save-window-excursion
      (unless (ob-eshell-session-live-p session)
	(let ((eshell-buffer-name session)) (eshell))))
    session))

(defun org-babel-variable-assignments:eshell (params)
  "Convert ob-eshell variables from PARAMS into Eshell variables assignments."
  (mapcar
   (lambda (pair)
     ;; Use `ignore' to suppress value in the command output.
     (format "(ignore (setq %s %S))" (car pair) (cdr pair)))
   (org-babel--get-vars params)))

(defun org-babel-load-session:eshell (session body params)
  "Load BODY into SESSION with PARAMS."
  (save-window-excursion
    (let ((buffer (org-babel-prep-session:eshell session params)))
      (with-current-buffer buffer
	(goto-char (point-max))
	(insert (org-babel-chomp body)))
      buffer)))

(provide 'ob-eshell)

;;; ob-eshell.el ends here