;;; org-clock-waybar.el --- 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)

(defcustom org-clock-waybar-text-function
  nil
  "Function to generate the title text.

The function must return a single string.
When nil, `org-clock-waybar-get-task-title' is used."
  :type 'function
  :group 'org-clock-waybar)

(defcustom org-clock-waybar-alt-function
  nil
  "Function to generate the alternative text.

The function must return a single string.
When nil, `org-clock-waybar-get-task-category' is used."
  :type 'function
  :group 'org-clock-waybar)

(defcustom org-clock-waybar-class-function
  nil
  "Function to generate the class.

The function must either return a string, or a list of strings.
When nil, `org-clock-waybar-get-tags' is used."
  :type 'function
  :group 'org-clock-waybar)

(defcustom org-clock-waybar-tooltip-function
  nil
  "Function to generate the tooltip.

The function must return a string.
When nil, `org-clock-waybar-get-tooltip' is used."
  :type 'function
  :group 'org-clock-waybar)

(defcustom org-clock-waybar-percentage-function
  nil
  "Function to generate the percentage text.

When nil, the percentage text will be an empty string."
  :type 'function
  :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 ()
  "Get the title of TASK."
  (if (org-clocking-p)
      (substring-no-properties org-clock-current-task)
    org-clock-waybar-not-clocked-in-text))

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

(defun org-clock-waybar--list-of-strings-p (object)
  "Return t if OBJECT is a list of strings."
  (not (null (delq nil
                   (mapcar (lambda (x) (and (stringp x) x)) object)))))

(defun org-clock-waybar-get-tooltip ()
  "The default tooltip to send to waybar."
  (when (org-clocking-p)
    (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-tags ()
  "Get the tags of the currently clocked-in task."
  (when (org-clocking-p)
    (save-window-excursion
      (org-clock-goto)
      (org-get-tags))))

(defun org-clock-waybar--get-clocked-task-json ()
  "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'."
  (let* ((text-func (or 'org-clock-waybar-text-function
                         'org-clock-waybar-get-task-title))
         (text (funcall text-func))
         (alt-func (or 'org-clock-waybar-alt-function
                       'org-clock-waybar-get-task-category))
         (alt (funcall alt-func))
         (tooltip-func (or 'org-clock-waybar-tooltip-function
                           'org-clock-waybar-get-tooltip))
         (tooltip (funcall tooltip-func))
         (class-func (or 'org-clock-waybar-class-function
                         'org-clock-waybar-get-tags))
         (class (funcall class-func))
         (percentage (when (fboundp 'org-clock-waybar-percentage-function)
                       (funcall 'org-clock-waybar-percentage-function)))
         (output (json-new-object)))
    (or (null title)
        (stringp title)
        (error "Title must be a string (org-clock-waybar)!"))
    (or (null alt)
        (stringp alt)
        (error "Alt text must be a string (org-clock-waybar)!"))
    (or (null tooltip)
        (stringp tooltip)
        (error "Tooltip must be a string (org-clock-waybar)!"))
    (or (null class)
        (stringp class)
        (org-clock-waybar--list-of-strings-p class)
        (error "Class must be a string or a list of strings (org-clock-waybar)!"))
    (or (null percentage)
        (stringp percentage)
        (error "Percentage must be a string (org-clock-waybar)!"))
    (setq output (json-add-to-object output "text" (or text "")))
    (setq output (json-add-to-object output "alt" (or alt "")))
    (setq output (json-add-to-object output "tooltip" (or tooltip "")))
    (setq output (json-add-to-object output "class" (or class "")))
    (setq output (json-add-to-object output "percentage" (or percentage "")))
    (json-encode output)))

(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)
    (insert (org-clock-waybar--get-clocked-task-json))
    (write-file org-clock-waybar-filename)))

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

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