{ writeShellApplication
, coreutils
, gnugrep
, rsync
, util-linux
, koboLabel ? "KOBOeReader"
, ... }: writeShellApplication {
  name = "KoboInstaller";
  runtimeInputs = [
    coreutils
    gnugrep
    rsync
    util-linux
  ];
  text = ''
    INPUT=${1-}

    if [[ -z "$INPUT" ]]; then
      echo "Must provide an input directory"
      exit 255
    fi

    if [[ ! -d "$INPUT/.kobo" ]] || [[ ! -d "$INPUT/.adds" ]]; then
      echo "Missing one of $INPUT/.kobo or $INPUT/.adds. Are you sure your input directory is correct?"
      exit 255
    fi

    KOBO_MOUNTPOINT="$(findmnt -nlo TARGET LABEL="${koboLabel}")"
    if [[ -z "$KOBO_MOUNTPOINT" ]]; then
      echo "Couldn't find a Kobo eReader volume! Is one actually mounted?"
      exit 255
    fi

    KOBO_DIR="$KOBO_MOUNTPOINT/.kobo"
    if [[ ! -d "$KOBO_DIR" ]]; then
      echo "It doesn't seem like $KOBO_MOUNTPOINT actually points to a Kobo eReader since it doesn't contain a .kobo directory..."
      exit 255
    fi

    # Tiny DRY helper for the failure message...
    recap_failure() {
      echo "* As a result, the device may have been left in an inconsistent state!"
      echo "* Please note that NO automatic cleanup will be done!"
      echo "* As such, before unplugging your device, consider removing:"
      echo "* The following folders:"
      for kfm_folder in .adds/kfmon .adds/koreader .adds/plato ; do
        local current_folder="$KOBO_MOUNTPOINT/$kfm_folder"
        if [[ -d "$current_folder" ]] ; then
          printf "\t%s\n" "$current_folder"
        else
          printf "\t%-96s%32s\n" "$current_folder" "[OK: Already gone]"
        fi
      done
      echo "* As well as the following files:"
      for kfm_file in .kobo/KoboRoot.tgz kfmon.png koreader.png icons/plato.png ; do
        local current_file="$KOBO_MOUNTPOINT/$kfm_file"
        if [[ -f "$current_file" ]] ; then
          printf "\t%s\n" "$current_file"
        else
          printf "\t%-96s%32s\n" "$current_file" "[OK: Already gone]"
        fi
      done
    }

    KOBO_CONFIG="$KOBO_DIR/Kobo/Kobo eReader.conf"
    echo "* Preventing Nickel from scanning hidden directories . . ."
    cat >> "${KOBO_CONFIG}" <<-\EoM

        [FeatureSettings]
        ExcludeSyncFolders=(\\.(?!kobo|adobe).+|([^.][^/]*/)+\\..+)
    EoM

    # Check for a cat failure, as unlikely as it might be (permissions?)...
    ret=$?
    if [[ $ret -ne 0 ]] ; then
        echo "* Installation FAILED: Failed to update Nickel config!"
        echo "* No permanent changes have been made."
        exit $ret
    fi

    # Double-check that it was updated, in case of gremlins attack...
    if ! grep -Fq 'ExcludeSyncFolders=(\\.(?!kobo|adobe).+|([^.][^/]*/)+\\..+)' "${KOBO_CONFIG}" ; then
        echo "* Installation FAILED: Nickel config update was ineffective o_O !"
        echo "* No permanent changes have been made."
        exit 255
    fi

    echo "* Installing Kobo package"
    rsync -vr "$INPUT/" "$KOBO_MOUNTPOINT"

    ret=$?
    if [[ $ret -ne 0 ]]; then
      echo "* Installation FAILED: Failed to copy archive!"
      recap_failure
      exit $ret
    fi

    echo "* Sanity check . . ."
    if [[ ! "$KOBO_DIR/KoboRoot.tgz" ]]; then
      echo "* Installation FAILED: Copying was ineffective (no KoboRoot tarball) o_O !"
      recap_failure
      exit 255
    fi

    echo "* Installation successful!"
    echo "* Please make sure to eject & unplug your device safely!"

    exit 0
  '';
}