#!/bin/sh

if [ $# -lt 1 ]; then
    exit 0;
fi

function get_current_root_device
{
    PARTUUID=$(swupdate -g | sed 's/PARTUUID=\([^ ]*\).*/\1/');
    CURRENT_ROOT=$(readlink -f /dev/disk/by-partuuid/$PARTUUID);
}

function get_update_part
{
    CURRENT_PART="${CURRENT_ROOT: -1}"
    if [ $CURRENT_PART = "2" ]; then
        UPDATE_PART="3";
	GRUB_DEFAULT="1";
	GRUB_FALLBACK="0";
    else
        UPDATE_PART="2";
	GRUB_DEFAULT="0";
        GRUB_FALLBACK="1";
    fi
}

function get_update_device
{
    UPDATE_ROOT=${CURRENT_ROOT%?}${UPDATE_PART}
}

if [ $1 == "preinst" ]; then
    # get the current root device
    get_current_root_device

    # get the device to be updated
    get_update_part
    get_update_device

    # create a symlink for the update process
    ln -sf $UPDATE_ROOT /dev/update
fi

if [ $1 == "postinst" ]; then
    get_current_root_device
    get_update_part
    sync; /usr/bin/grub-editenv /boot/efi/EFI/BOOT/grubenv set default=$GRUB_DEFAULT; sync;
    sync; /usr/bin/grub-editenv /boot/efi/EFI/BOOT/grubenv set fallback=$GRUB_FALLBACK; sync;
fi