Initial, untested version

org-clock-waybar.el

@@ -0,0 +1,59 @@
+;;; org-clock-waybar --- Summary
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'xdg)
+(require 'org-clock)
+
+(defgroup org-clock-waybar nil
+  "Send current clocked task to a JSON file for Waybar visualization"
+  :group 'emacs)
+
+(defcustom org-clock-waybar-filename
+  (expand-file-name ".waybar-current-task.json" (xdg-cache-home))
+  "Name of the file to save task data to."
+  :type 'string
+  :group 'org-clock-waybar)
+
+(defconst org-clock-waybar-filename-coding-system
+  (if (coding-system-p 'utf-8-emacs)
+      'utf-8-emacs
+    'emacs-mule)
+  "Coding system of the file `org-clock-waybar-filename'.")
+
+(defun org-clock-waybar--get-clocked-task-json (buffer)
+  "Save the current clocked-in task’s title and category to BUFFER.
+
+The output is in JSON format.  If there is no clocked in task, both title and
+category will be a JSON null value."
+  (let ((category (when org-clock-current-task
+                    (get-text-property 0 'org-category org-clock-current-task)))
+        (title (when org-clock-current-task
+                 (substring-no-properties org-clock-current-task))))
+    (with-current-buffer buffer
+      (insert "{\"title\":")
+      (insert (if title (json-encode-string title) "null"))
+      (insert ",\"category\":")
+      (insert (if category (json-encode-string category) "null"))
+      (insert "}"))))
+
+(defun org-clock-waybar-save-task ()
+  "Save the current clocked in task to `org-clock-waybar-filename'."
+  (with-temp-buffer
+    (erase-buffer)
+    (set-buffer-file-coding-system org-clock-waybar-filename-coding-system)
+    (org-clock-waybar--get-clocked-task-json (current-buffer))
+    (write-file org-clock-waybar-filename)))
+
+(defun org-clock-waybar-setup ()
+  "Setup org-clock-waybar.
+
+It adds `org-clock-waybar-save-task' to both `org-clock-in-hook' and
+`org-clock-out-hook'."
+  (add-hook 'org-clock-in-hook #'org-clock-waybar-save-task)
+  (add-hook 'org-clock-out-hook #'org-clock-waybar-save-task))
+
+(provide 'org-clock-waybar)
+;;; org-clock-waybar.el ends here