guixsd-configuration/modules/i3-battery-warning.scm

#!/run/current-system/profile/bin/guile -s
!#

(define-module (i3-battery-warning)
  #:use-module (ice-9 rdelim)
  #:use-module (ice-9 regex)
  #:use-module (ice-9 popen)
  #:use-module (srfi srfi-1))

;; TODO!
;; Make config file to read values.
;; Package with guix
;; Add to mcron jobs as a simple program...


(define BAT-WARN-LVL 30)
(define BAT-ERR-LVL 20)

(define (bat-percentage)
  (let* ((return #f)
         (pipe-bat
          (open-input-pipe
           (string-append "upower -i "
                          "/org/freedesktop/UPower/devices/battery_BAT0")))
         (str-bat (read-line pipe-bat))
         (re-perc-line (make-regexp "percentage:"))
         (re-perc-num (make-regexp "[0-9][0-9]")))

    (while (not (eof-object? str-bat))
      (when (regexp-exec re-perc-line str-bat)
        (set! return (string->number
                      (match:substring
                       (regexp-exec re-perc-num str-bat)))))
      (set! str-bat (read-line pipe-bat)))

    (close-pipe pipe-bat)
    return))

(define (pwr-connected?)
  (let* ((return #f)
         (pipe-pwr
          (open-input-pipe
           (string-append "upower -i"
                          " /org/freedesktop/UPower/devices/line_power_ADP1")))
         (str-pwr (read-line pipe-pwr))
         (re-pat (make-regexp "online:              yes" regexp/icase)))

    (while (not (eof-object? str-pwr))
       (when (regexp-exec re-pat str-pwr)
         (set! return #t))
       (set! str-pwr (read-line pipe-pwr)))
    
    (close-pipe pipe-pwr)
    return))

(define (notify-usr percentage)
  (system (string-append "i3-nagbar"
                         " -m \"Battery low! at " (number->string percentage) "%\""
                         " -t "
                         (if (< percentage BAT-ERR-LVL)
                             "error"
                             "warning"))))

(define (check&react)
  (let ((pc (pwr-connected?))
        (bp (bat-percentage)))
    (unless pc
      (when (< bp BAT-WARN-LVL)
        (notify-usr bp)))))

(check&react)