(define-module (buer shepherd-services)
  #:use-module (guix gexp)
  #:use-module (gnu services shepherd)
  #:use-module (shepherd service timer)

  #:export (guix-gc snapshot-@home timer))

(define timer-trigger-action
  (shepherd-action
    (name 'trigger)
    (procedure #~trigger-timer)
    (documentation
      "Trigger the action associated with @var{timer} as if it had reached its
next calendar event.")))

(define guix-gc
  (shepherd-service
    (provision '(guix-gc))
    (modules '((shepherd service timer)))
    (start #~(make-timer-constructor
               (calendar-event #:days-of-month '(1 15))
               (command '("guix" "gc" "--optimize" "--free-space=10G"))))
    (stop #~(make-timer-destructor))
    (actions (list timer-trigger-action))))

(define snapshot-@home
  (shepherd-service
    (provision '(snapshot-@home))
    (modules '((shepherd service timer)))
    (start #~(make-timer-constructor
               (calendar-event #:days-of-month '(1 15))
               (lambda ()
                 (let ((btrfs "/run/current-system/profile/bin/btrfs")
                       (date (strftime "%Y-%m-%d" (localtime (current-time)))))
                   (spawn-shell-command
                     (string-append btrfs " subvolume snapshot"
                                    " /home /snapshots/home/" date))))))
    (stop #~(make-timer-destructor))
    (actions (list timer-trigger-action))))

(define timer
  (shepherd-service
    (provision '(timer))
    (modules '((shepherd service timer)))
    (free-form #~(timer-service))))