;;; ob-svgbob.el --- Babel Functions for SVGBob -*- lexical-binding: t; -*-

;; Copyright (C) 2021 Free Software Foundation, Inc.

;; Author: Steven vanZyl <rushsteve1@rushsteve1.us>
;;         TEC <tec@tecosaur.com>
;; Maintainer: Timothy <tec@tecosaur.com>
;; Keywords: literate programming, reproducible research
;; Homepage: https://orgmode.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:

;; Org-Babel support for evaluating and SVGBob diagrams.
;; https://github.com/ivanceras/svgbob

;; This is very similar to ob-dot.el with a similar list of caveats:

;; * There are no sessions
;; * We are generally only going to return results of type "file graphics"
;; * The "file" header argument is required
;; * SVGBob has no definite syntax

;; This file also includes some additional utility functions and a simple
;; derived major-mode for SVGBob

;;; Code:
(require 'ob)

(defcustom svgbob-executable "svgbob"
  "The path to the SVGBob binary.
This can be installed from source using `cargo install svgbob_cli'"
  :group 'svgbob
  :type 'file)

(defcustom svgbob-buffer-name "*svgbob-output*"
  "The name of the buffer that SVGBob will output to"
  :group 'svgbob
  :type 'string)

(defcustom org-babel-svgbob-options
  '((background . "transparent"))
  "Options passed to the SVGBob executable"
  :group 'svgbob
  :type '(alist :value-type (symbol string)))

;; So `org-edit-special' works.
;; Since SVGBob is based on simple ASCII diagrams without a definite, this mode
;; is derived from `artist-mode'.
(unless (fboundp 'svgbob-mode)
  (define-derived-mode svgbob-mode artist-mode "svgbob"))

(defun ob-svgbob-string-to-svg (str)
  "Converts a string to SVG text and returns a string of that"
  (org-babel-eval
   (concat svgbob-executable " "
           (mapconcat (lambda (opt) (format "--%s %s " (symbol-name (car opt)) (cdr opt)))
                      org-babel-svgbob-options
                      " "))
   str))

(defun ob-svgbob-region-to-svg (start end)
  "Converts a region to SVG text in a new buffer"
  (interactive "r")
  (let ((str (ob-svgbob-string-to-svg (buffer-substring-no-properties start end))))
    (with-current-buffer (get-buffer-create svgbob-buffer-name)
      (read-only-mode 0) ; Disable read-only
      (fundamental-mode) ; Required to erase the buffer
      (erase-buffer)
      (insert str)
      (image-mode)
      (read-only-mode)
      (display-buffer-in-side-window (current-buffer) '((side . right))))))

(defun ob-svgbob-buffer-to-svg ()
  "Converts a buffer to SVG text in a new buffer.
See `svgbob-region-to-svg' for more"
  (interactive)
  (ob-svgbob-region-to-svg (point-min) (point-max)))

(defvar org-babel-default-header-args:svgbob
  '((:results . "file graphics") (:exports . "results"))
  "Default arguments to use when evaluating a dot source block.")

(defun org-babel-execute:svgbob (body params)
  (if (alist-get :file params)
      (ob-svgbob-string-to-svg body)
    (user-error "You need to specify a :file parameter")))

(defun org-babel-prep-session:svgbob (_session _params)
  "Return an error because SVGBob does not support sessions."
  (user-error "SVGBob does not support sessions"))

(provide 'ob-svgbob)

;;; ob-svgbob.el ends here