;; -----------------------------------------------------------------------------

;; https://www.gnu.org/software/emacs/manual/html_node/org/Math-formatting-in-HTML-export.html
;; https://orgmode.org/manual/Math-formatting-in-HTML-export.html
;; https://emacs.stackexchange.com/questions/31271/siunitx-mathjax-org-mode-and-html-export
;; https://stackoverflow.com/questions/49300667/which-mathjax-cdn-script-should-be-used

;; modify path and mathml
(setq org-html-mathjax-options
  '((path "https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML")
    (scale "100")
    (align "center")
    (indent "2em")
    (mathml t)))

(setq org-html-mathjax-template
              "
<script type=\"text/javascript\" src=\"%PATH\"></script>
<script type=\"text/javascript\">
<!--/*--><![CDATA[/*><!--*/
    MathJax.Hub.Config({
        jax: [\"input/TeX\", \"output/HTML-CSS\"],
        extensions: [\"tex2jax.js\",\"TeX/AMSmath.js\",\"TeX/AMSsymbols.js\",
                     \"TeX/noUndefined.js\", \"[Contrib]/siunitx/siunitx.js\", \"[Contrib]/mhchem/mhchem.js\"],
        tex2jax: {
            inlineMath: [ [\"\\\\(\",\"\\\\)\"] ],
            displayMath: [ ['$$','$$'], [\"\\\\[\",\"\\\\]\"], [\"\\\\begin{displaymath}\",\"\\\\end{displaymath}\"] ],
            skipTags: [\"script\",\"noscript\",\"style\",\"textarea\",\"pre\",\"code\"],
            ignoreClass: \"tex2jax_ignore\",
            processEscapes: false,
            processEnvironments: true,
            preview: \"TeX\"
        },
        TeX: {extensions: [\"AMSmath.js\",\"AMSsymbols.js\",  \"[Contrib]/siunitx/siunitx.js\", \"[Contrib]/mhchem/mhchem.js\"]},
        showProcessingMessages: true,
        displayAlign: \"%ALIGN\",
        displayIndent: \"%INDENT\",

        \"HTML-CSS\": {
             scale: %SCALE,
             availableFonts: [\"STIX\",\"TeX\"],
             preferredFont: \"TeX\",
             webFont: \"TeX\",
             imageFont: \"TeX\",
             showMathMenu: true,
        },
        MMLorHTML: {
             prefer: {
                 MSIE:    \"MML\",
                 Firefox: \"MML\",
                 Opera:   \"HTML\",
                 other:   \"HTML\"
             }
        }
    });
/*]]>*///-->
</script>")

;; -----------------------------------------------------------------------------

;; https://www.reddit.com/r/orgmode/comments/7u2n0h/tip_for_defining_latex_macros_for_use_in_both/

(add-to-list 'org-src-lang-modes '("latex-macros" . latex))

(defvar org-babel-default-header-args:latex-macros
  '((:results . "raw")
    (:exports . "results")))

(defun prefix-all-lines (pre body)
  (with-temp-buffer
    (insert body)
    (string-insert-rectangle (point-min) (point-max) pre)
    (buffer-string)))

(defun org-babel-execute:latex-macros (body _params)
  (concat
   (prefix-all-lines "#+LATEX_HEADER: " body)
   "\n#+HTML_HEAD_EXTRA: <div style=\"display: none\"> \\(\n"
   (prefix-all-lines "#+HTML_HEAD_EXTRA: " body)
   "\n#+HTML_HEAD_EXTRA: \\)</div>\n"))

;; Example:

;; #+BEGIN_SRC latex-macros
;; \newcommand{\Z}{\mathbb{Z}}
;; \newcommand{\Hom}{\mathrm{Hom}}
;; #+END_SRC

(org-toggle-inline-images)