(define-module (resize-fs)
  #:use-module (gnu packages disk)
  #:use-module (gnu packages linux)

  #:use-module (guix build utils)
  #:use-module (guix packages)

  #:use-module (gnu services)
  #:use-module (guix gexp)
  #:use-module (guix records)
  #:use-module (gnu services shepherd))

(define (resize-fs-service config)
  (use-modules (guix gexp))
  (define parted #$(string-append (or (resize-fs-configuration-parted config)
                                      parted)
                                  "/sbin/parted"))
  (define resize2fs #$(string-append (or (resize-fs-configuration-e2fsprogs config)
                                         e2fsprogs)
                                     "/sbin/resize2fs"))
  (define size #$(resize-fs-configuration-size config))
  (define device #$(resize-fs-configuration-device config))
  (define partition #$(resize-fs-configuration-partition config))
  (define device+partition (string-append device "p" partition))

  (shepherd-service
   (documentation "Resize a file-system.  Intended for Guix Systems that are booted from an image")
   (provision '(resize-fs))
   (one-shot? #t)
   (requirement '())
   (start #~(invoke (plain-file "resize_partition.bash"
                                (string-append
                                 "#!/bin/sh
parted " #$device " ---pretend-input-tty <<EOF
resizepart
" #$partition "
Yes
" #$size"
EOF
" $#resize2fs " " device+partition))))))

(define-record-type* <resize-fs-configuration>
  resize-fs-configuration make-resize-fs-configuration
  resize-fs-configuration?
  ;; the utilities doing the job
  (parted resize-fs-configuraiton-parted
          (default parted))
  (e2fsprogs resize-fs-configuration-e2fsprogs
             (default e2fsprogs))
  ;; path of a device
  (device resize-fs-configuration-device
          (default "/dev/mmcblk0")) ; #f may be preferrable here
  ;; integer
  (partition resize-fs-configuration-partition
             (default 2))
  ;; size - as understood by parted
  (size resize-fs-configuration-size
        (default "100%")))

(define-public resize-fs-service-type
  (service-type
   (name 'resize-fs)
   (extensions
    (list (service-extension shepherd-root-service-type resize-fs-service)))
   (description "Resize a partition.")
   (default-value (resize-fs-configuration))))