;;; org-clock-waybar --- Summary

;; Copyright (C) 2021 Gergely Polonkai

;; Author: Gergely Polonkai <gergely@polonkai.eu>
;; Keywords: org, clocking, waybar
;; Version: 1.0
;; Package-Requires: ((emacs "26.1"))
;; URL: https://gitea.polonkai.eu/gergely/org-clock-waybar

;; 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:

;; Export the currently clocked-in task in JSON format that Waybar can process
;;
;; To use it, customize the `org-clock-waybar-filename' variable (defaults to
;; $XDG_CONFIG_HOME/waybar-current-task.json) and add the following snippet to
;; your Waybar config:
;;
;; "custom/org": {
;;   "format": " {}",
;;   "return-type": "json",
;;   "restart-interval": 5,
;;   "exec": "cat /home/yourusername/.cache/waybar-current-task.json"
;; }

;;; Code:

(require 'xdg)
(require 'json)
(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)

(defcustom org-clock-waybar-not-clocked-in-text
  "Not clocked in"
  "Text to display when not clocked in on any task."
  :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'.")

(defsubst org-clock-waybar--get-task-title (task)
  "Get the title of TASK."
  (when task (substring-no-properties task)))

(defsubst org-clock-waybar--get-task-category (task)
  "Get the category of TASK."
  (when task (get-text-property 0 'org-category task)))

(defun org-clock-waybar--get-tooltip ()
  "The default tooltip to send to waybar."
  (when org-clock-current-task
    (let ((clocked-time (org-clock-get-clocked-time)))
      (format "%s: %s (%s)"
              (org-clock-waybar--get-task-category)
              (org-clock-waybar--get-task-title)
              (org-duration-from-minutes clocked-time)))))

(defun org-clock-waybar--get-clocked-task-json (&optional clocking-out)
  "Get the currently clocked-in task’s data as a stringified JSON object.

The output is in JSON format constructed in a way so Waybar can process it.
If there is no clocked in task, alt becomes empty and text will be set to the
value of `org-clock-waybar-not-clocked-in-text'.

If CLOCKING-OUT is non-nil, `org-clock-current-task' will be treated as if it
were nil; this is required because `org-clock-out' calls the hook functions
before setting `org-clock-current-task' to nil."
  (let* ((task (if clocking-out nil org-clock-current-task))
         (category (org-clock-waybar--get-task-title task))
         (title (org-clock-waybar--get-task-category task))
         (tooltip (org-clock-waybar--get-tooltip))
         (output (json-new-object)))
    (setq output (json-add-to-object
                  output
                  "text"
                  (or title org-clock-waybar-not-clocked-in-text)))
    (setq output (json-add-to-object output "alt" (or category "")))
    (setq output (json-add-to-object output "tooltip" (or tooltip "")))
    (setq output (json-add-to-object output "class" ""))
    (setq output (json-add-to-object output "percentage" ""))
    (json-encode output)))

(defun org-clock-waybar-save-task (&optional clocking-out)
  "Save the current clocked in task to `org-clock-waybar-filename'.

If CLOCKING-OUT is non-nil, treat the current task as if it were nil."
  (with-temp-buffer
    (erase-buffer)
    (set-buffer-file-coding-system org-clock-waybar-filename-coding-system)
    (insert (org-clock-waybar--get-clocked-task-json clocking-out))
    (write-file org-clock-waybar-filename)))

(defun org-clock-waybar-clear-task ()
  "Clear the current task from `org-clock-waybar-filename'."
  (org-clock-waybar-save-task t))

(defun org-clock-waybar-ouptut-task ()
  "Output the current task in JSON format Waybar can understand.

This function is ought to be used via Emacsclient:

emacsclient --eval '(org-clock-waybar-output-task)'"
  (org-clock-waybar--get-clocked-task-json))

(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-task)
  (add-hook 'kill-emacs-hook #'org-clock-waybar-clear-task))

(provide 'org-clock-waybar)
;;; org-clock-waybar.el ends here