(unless (= 2 (length argv))
  (error "Usage: emacs --script scripts/export-to-html <source-file> <output-file>"))

(let* ((source-filename (file-truename (elt argv 0)))
       (output-filename (file-truename (elt argv 1)))
       (source-buffer (find-file source-filename))
       (output-buffer (find-file output-filename))
       (html-buffer (get-buffer-create "*Org HTML Export*"))
       (pt nil)
       (file-buffer (current-buffer))
       (org-html-toplevel-hlevel 1)
       (org-html-head "")
       (org-html-head-extra "")
       (org-html-head-include-default-style nil)
       (org-html-head-include-scripts nil)
       (org-html-preamble nil)
       (org-html-postamble nil)
       (org-html-use-infojs nil)
       (org-export-with-toc nil))
  (with-current-buffer output-buffer
    (erase-buffer))

  (set-buffer source-buffer)
  (org-next-visible-heading 1)
  (while (not (equal pt (point)))
    (setq pt (point))
    (let ((title (org-get-heading t))
          (id (org-element-property :CUSTOM_ID (org-element-at-point)))
          (timestamp (org-read-date nil
                                    t
                                    (org-element-property :TIMESTAMP (org-element-at-point))
                                    nil))
          (tags (org-get-tags))
          (subtree nil)
          (html nil)
          (hash nil))
      (org-copy-subtree)
      (setq subtree (with-temp-buffer (yank) (buffer-string)))

      (org-html-export-as-html nil t t t)
      (set-buffer html-buffer)
      (setq html (buffer-string))

      (set-buffer output-buffer)
      (json-insert `((id . ,id)
                     (title . ,title)
                     (timestamp . ,(format-time-string "%FT%T%z" timestamp))
                     (tags . ,(vconcat tags))
                     (hash . ,(secure-hash 'sha256 subtree))
                     (source . ,subtree)
                     (html . ,html)))

      (set-buffer source-buffer))
    (org-forward-heading-same-level 1))

  (set-buffer output-buffer)
  (save-buffer))