;; How I Convert Org Files To HTML.
;; ================================
;;
;; Or: Why We Can't Have Nice Things: Exhibit #42.
;;     -------------------------------------------
;;
;; Or: I Got Way Too Much Time On My Hands, Apparently.
;;     ------------------------------------------------
;;
;; I see two straightforward ways to export Org files to HTML:
;;
;; 1. ox-html.el, Org's HTML backend: even with all the settings and
;;    filters available, there are still a few things that annoy me:
;;    lots of extra <div>s, unstable section IDs…
;;
;;    Also, I want to squeeze pandoc somewhere in the pipeline, to run
;;    my Lua filters.
;;
;; 2. pandoc: does not cover all of Org's features.  Org is so crammed
;;    with constructs that don't exist in other markup formats
;;    (agendas, logbooks, spreadsheets, properties…) and so many knobs
;;    can be tweaked on a per-file basis (link abbreviations, tags,
;;    TODO cycles) that Elisp remains the least painful way to process
;;    these files, IMO.
;;
;; A less-straightforward, but still reasonably simple way to go would
;; be to use Org's markdown backend, then run pandoc on the result.
;; Unfortunately, AFAICT ox-md.el does not implement definition lists,
;; nor syntax-highlighting in fenced code blocks.
;;
;; So here's where I'm at: using Elisp, I'll preprocess Org files to
;; add a bunch of #+OPTIONS pandoc recognizes, "dumb down" the stuff
;; pandoc does not recognize, format some other stuff arbitrarily,
;; *then* I'll run pandoc on the result.

(defun preprocess-org (input)
  (with-temp-buffer
    (insert "#+OPTIONS: ^:{} tags:nil\n")
    (insert-file-contents input)
    (org-mode)
    (while (re-search-forward org-heading-regexp nil t)
      (save-excursion
        (save-match-data
          (when-let ((tags (org-get-tags (point))))
            (insert "\n#+begin_tags\n")
            (dolist (tag tags)
              (insert "- " tag "\n"))
            (insert "#+end_tags\n")))))
    ;; TODO: dump properties
    ;; TODO: fontify TODO keywords
    ;; TODO: expand #+LINK abbreviations
    (princ (buffer-string))))