#!/bin/bash
#
# Credits to hassos-expand original script
# https://github.com/home-assistant/operating-system/

DEVICE_OVERLAYFS="$(findfs PARTUUID=f1326040-5236-40eb-b683-aaa100a9afcf)"
DEVICE_OVERLAYFS_NAME="$(basename "${DEVICE_OVERLAYFS}")"
DEVICE="/dev/$(lsblk -no pkname "${DEVICE_OVERLAYFS}")"
PART_NUM="$(cat "/sys/class/block/${DEVICE_OVERLAYFS_NAME}/partition")"
PART_TABLE="$(sfdisk -lqJ "${DEVICE}")"

if sfdisk --verify "${DEVICE}" 2>&1 | grep "The backup GPT table is not on the end of the device."; then
        echo "[INFO] Moving GPT backup header to the end"
        sfdisk --relocate gpt-bak-std "${DEVICE}"

        # Reload partition label to get correct .partitiontable.lastlba
        PART_TABLE="$(sfdisk -lqJ "${DEVICE}")"
fi
LAST_USABLE_LBA="$(echo "${PART_TABLE}" | jq -r '.partitiontable.lastlba')"

echo "[INFO] Last usable logical block ${LAST_USABLE_LBA}"

JQ_FILTER=".partitiontable.partitions[] | select ( .node == \"${DEVICE_OVERLAYFS}\" ) | .start + .size"
OVERLAYFS_PARTITION_END="$(echo "${PART_TABLE}" | jq "${JQ_FILTER}")"
echo "[INFO] Overlayfs partition end block ${OVERLAYFS_PARTITION_END}"

UNUSED_BLOCKS=$(( LAST_USABLE_LBA - DATA_PARTITION_END ))
if [ "${UNUSED_BLOCKS}" -le "16384" ]; then
    echo "[INFO] No resize of overlayfs partition needed"
    exit 0
fi

echo "[INFO] Update Overlayfs partition ${PART_NUM}"
echo ", +" | sfdisk --no-reread --no-tell-kernel -N "${PART_NUM}" "${DEVICE}"
sfdisk -V "${DEVICE}"
partx -u "${DEVICE}"
udevadm settle
partprobe "${DEVICE}"

echo "[INFO] Resizing the overlayfs partition"
resize2fs "${DEVICE_OVERLAYFS}"
echo "[OK]"