commit cbfe4536d6239c9ae5c95c52cab11402623c3b81
Author: Yann Esposito (Yogsototh) <yann.esposito@gmail.com>
Date:   Tue Jul 30 23:23:01 2019 +0200

    Initial commit, emacs package is not straightforward.

diff --git a/org-auto-id.el b/org-auto-id.el
new file mode 100644
index 0000000..18baa8e
--- /dev/null
+++ b/org-auto-id.el
@@ -0,0 +1,88 @@
+;;; org-auto-id.el --- Add custom id to all org entries, useful for html exporting. -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2019 Yann Esposito
+
+;; Author: Yann Esposito <yann@esposito.host>
+;; Maintainer: Yann Esposito <yann@esposito.host>
+;; Created: 28 Jul 2019
+;; Version: 0.1
+;; Keywords: org
+;; Homepage: https://gitlab.esy.fun/yogsototh/org-auto-id
+;; Package-Requires: ((emacs "24.4") org (org-auto-id "0.1"))
+
+;; This file is not part of GNU Emacs
+
+;;; Commentary:
+;; Will warn you if you have duplicate CUSTOM_ID.
+
+;;; License:
+
+;; Licensed under the same terms as Emacs.
+
+;;; Code:
+
+(require 'org)
+
+(with-eval-after-load 'org
+  (defvar org-auto-id--all-ids '()
+    "List as set of all ids of the current org-file")
+
+  (defun org-auto-id-format (title)
+    "Generate a new org-id using TITLE."
+    (concat (downcase (replace-regexp-in-string "\\W" "-" title))))
+
+  (defun org-auto-id-add-id (id &optional new?)
+    "Add the id to the set of existing ids, warn if not a generation of new id."
+    (if (member id org-auto-id--all-ids)
+        (progn (unless new?
+                 (message "Duplicate CUSTOM_ID found: %s" id))
+               (org-auto-id-add-id (format "%s-%04x" id (random (expt 16 4))) new?))
+      (progn
+        (add-to-list 'org-auto-id--all-ids id)
+        id)))
+
+  (defun org-auto-id-custom-id-get (&optional pom create)
+    "Get the CUSTOM_ID property of the entry at point-or-marker POM.
+If POM is nil, refer to the entry at point.
+If the entry does not have an CUSTOM_ID, the function returns nil.
+However, when CREATE is non nil, create a CUSTOM_ID if none is present already.
+In any case, the CUSTOM_ID of the entry is returned."
+    (interactive)
+    (org-with-point-at pom
+      (let ((id (org-entry-get nil "CUSTOM_ID")))
+        (cond
+         ((and id (stringp id) (string-match "\\S-" id))
+          (progn
+            (org-auto-id-add-id id)
+            id))
+         (create
+          (let ((id (org-auto-id-format (org-entry-get nil "ITEM"))))
+            (let ((new-id (org-auto-id-add-id id t)))
+              (org-entry-put pom "CUSTOM_ID" new-id)
+              new-id)))))))
+
+  (defun org-auto-id-add-ids-to-headlines-in-file ()
+    "Add CUSTOM_ID properties to all headlines.
+In the current file, all headlines which do not already have a CUSTOM_ID.
+Only adds ids if the `auto-id' option is set to `t' in the file somewhere.
+ie, #+OPTIONS: auto-id:t"
+    (interactive)
+    (save-excursion
+      (widen)
+      (goto-char (point-min))
+      (let ((add-suffix (re-search-forward "^#\\+OPTIONS:.* auto-id-add-suffix:t" (point-max) t)))
+        (when (re-search-forward "^#\\+OPTIONS:.* auto-id:t" (point-max) t)
+          (setq org-auto-id--all-ids '())
+          (org-map-entries (lambda () (org-auto-id-custom-id-get (point) 'create)))))))
+
+  (add-hook 'org-mode-hook
+            (lambda ()
+              (add-hook 'before-save-hook
+                        (lambda ()
+                          (when (and (eq major-mode 'org-mode)
+                                     (eq buffer-read-only nil))
+                            (org-auto-id-add-ids-to-headlines-in-file)))))))
+
+(provide 'org-auto-id)
+
+;;; org-auto-id.el ends here