;;; ox-template.el --- A HTML exporter via templates for org-mode
;; Copyright (C) 2021 Sameer Rahmani
;; Author: Sameer Rahmani <lxsameer@gnu.org>
;; URL: https://devheroes.codes/lxsameer/lxhome
;;
;; This program 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.
;;
;; This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; Inspired by Juan Jose Garcia Ripoll work.
;;; Code:
;; We ensure the org infrastructure

(require 'org)
(require 'seq)
(require 'ox-publish)
(require 'mustache)
(require 'pp)
(require 'ht)
(require 'lisp/utils)


(defun use-html (path-to-template)
  "Use the given template at PATH-TO-TEMPLATE as a template."
  (with-temp-buffer
    (insert-file-contents path-to-template)
    (buffer-string)))


(defun render-tags (tags)
  "Return a string representing TAGS html."
  (if tags
      (mapconcat (lambda (x) (format "<a href=\"/tags/%s.html\" class=\"tag-link\">#%s</a>" x x))
                 tags
                 " | ")
    ""))


(defun preamble-fn (info)
  "Return a string for the header section of pages using INFO plist."
  (let* ((file (plist-get info :input-file))
         (page-template (or (plist-get info :html-page-preamble-template) "page-preamble.html"))
         (post-template (or (plist-get info :html-post-preabmle-template) "post-preamble.html"))
         (is-page? (string= (get-file-global-props file "PAGE") "true"))
         (tags (get-file-tags file)))

    (let ((title (get-file-global-props file "TITLE"))
          (date (get-file-global-props file "DATE")))

      (when (not title)
        (message "'#+TITLE' is missing from '%s'" file)
        (error "'#+TITLE' is missing from '%s'" file))

      (if is-page?
          (mustache-render (use-html page-template)
                           (ht ("title" title)))
        (progn

          (mustache-render (use-html post-template)
                           (ht
                            ("title" title)
                            ("date" (or date ""))
                            ("tags" (render-tags tags)))))))))


(defun org-html-render-tag-template (tags info)
  "Render the given TAGS and INFO using the :html-headline-template."
  (let ((template (plist-get info :html-tags-template))
        (ctx (ht ("tags" (format "%s" tags))
                 ("base-url" (plist-get info :base-url)))))
    (if (null tags)
        ""
      (mustache-render (use-html template) ctx))))


;; Replace org-html--tags with our impelementation if the
;; `:html-headline-template' configuration exists
(advice-add 'org-html--tags :around 'org-html-tag-template)

(defun org-html-tag-template (orig-fn &rest args)
  "Decide whether to run ORIG-FN with ARGS or the org-html-render-tag-template.
It looks for `:html-tags-template' in the info and if i exists it will
call `org-html-render-tag-template' otherwise will call ORIG-FN."
  (let ((template (plist-get (cadr args) :html-tags-template)))
    (if template
        (apply #'org-html-render-tag-template args)
      (apply orig-fn args))))



(org-export-define-derived-backend 'templated-html 'html
  :translate-alist '((template . templated-html-template-fn)))


(defun headline-format (todo todo-type priority text tags info)
  "Format the headline using TODO TODO-TYPE PRIORITY TEXT TAGS and INFO."
  (let ((todo (org-html--todo todo info))
	(priority (org-html--priority priority info))
        ;; We don't care about the tags here since we put the in the preamble
	(tags nil))

    (concat todo (and todo " ")
	    priority (and priority " ")
	    text
	    (and tags "&#xa0;&#xa0;&#xa0;") tags)))


(defun render-template (template-name contents info)
  "Render the given template TEMPLATE-NAME using CONTENTS and INFO."
  (let ((ctx (ht ("content" contents)
                 ("head" (plist-get info :html-head-extra))
                 ("base-url" (plist-get info :base-url))
                 ("preamble" (org-html--build-pre/postamble 'preamble info))
                 ("postamble" (org-html--build-pre/postamble 'postamble info)))))
    (mustache-render (use-html template-name) ctx)))


(defun templated-html-template-fn (contents info)
  "Return the finalized html CONTENTS using the INFO and templates."
  (let ((template (plist-get info :html-template)))
    (if template
        (render-template template contents info)
      (org-html-template contents info))))


(defun custom-drawer-format (name content)
  (format "<section class='%s-drawer'><p>%s</p>%s</section>"
          (downcase name)
          (capitalize name)
          content))


(defun org-html-publish-to-templated-html (plist filename pub-dir)
  "Publish an org file to HTML.

FILENAME is the filename of the Org file to be published.  PLIST
is the property list for the given project.  PUB-DIR is the
publishing directory.

Return output file name."
  (org-publish-org-to 'templated-html filename
                      (concat "." (or (plist-get plist :html-extension)
                                      org-html-extension
                                      "html"))
                      plist pub-dir))


(provide 'lisp/ox-template)
;;; ox-template.el ends here