#!/bin/bash
# batocera-ventoy-resize.sh 20240921 n2qz/maximumentropy
# Expand a Batocera installation image file to make storage space
# available in SHARE when booting the image from Ventoy.
#
# Tested on Ubuntu 24.04.1 LTS with e2fsprogs 1.47.0. May not work on
# older versions of linux, as current Batocera images (v41+) use newer
# ext4 features not available with older ext4 utilities
err () {
    exitcode=$?
    echo "... Exit code $exitcode on line ${BASH_LINENO[0]} while executing command: $BASH_COMMAND"
    exit $exitcode
}
trap err ERR
growsize="$1"
inputimage="$2"
outputimage="$3"
if [ -z "${growsize}" -o -z "${inputimage}" -o "${inputimage}" = "${outputimage}" -o "${outputimage}" != "$(basename "${outputimage}" .gz)" ]
then
    echo "Usage: $0 growsize inputimage[.gz] [outputimage]"
    echo "Example: $0 32G batocera.img ventoy.img"
    exit 2
fi
image=$(basename "${inputimage}" .gz)
if [ -z "${outputimage}" ]
then
    outputimage="ventoy-${image}"
fi
if [ "${inputimage}" = "${image}" ]
then
    echo "... Copy ${inputimage} to ${outputimage}"
    cp "${inputimage}" "{$outputimage}"
else
    echo "... Decompress ${inputimage} to ${outputimage}"
    gzip -vkcd "${inputimage}" > "${outputimage}"
fi
echo "... Grow image ${outputimage}"
truncate -s "+${growsize}" "$outputimage"
echo "... Set up loopback device"
lodev=$(sudo losetup --find --show --partscan "${outputimage}")
echo "... Loopback device is: ${lodev}"
sharepart=2
sharepartdev="${lodev}p${sharepart}"
echo "... Adjust GPT on ${lodev}"
sudo sgdisk -e "${lodev}"
echo "... Show free space on ${sharepartdev}"
sudo dumpe2fs "${sharepartdev}" | grep '^Free blocks'
echo "... Resize SHARE partition ${sharepartdev}"
sudo parted -s "${lodev}" "resizepart ${sharepart} 100%"
echo "... Check ${sharepartdev}"
sudo fsck -f "${sharepartdev}"
echo "... Grow ${sharepartdev}"
sudo resize2fs "${sharepartdev}"
echo "... Show free space on ${sharepartdev}"
sudo dumpe2fs "${sharepartdev}" | grep '^Free blocks'
echo "... Detach loopback device ${lodev}"
sudo losetup -d "${lodev}"
echo "... Successfully completed"