#! /bin/sh -e
# initramfs local-premount script for resizing writable

PREREQ=""

# Output pre-requisites
prereqs()
{
        echo "$PREREQ"
}

case "$1" in
    prereqs)
        prereqs
        exit 0
        ;;
esac

TMPFILE="/run/initramfs/old-table.txt"
LOGFILE="/run/initramfs/resize-writable.log"

wait-for-root "LABEL=writable" "${ROOTDELAY:-180}" >/dev/null || true

for opt in $(cat /proc/cmdline); do
    case $opt in
        debug)
            LOGFILE="/dev/kmsg"
        ;;
    esac
done

writable_part="$(findfs LABEL=writable)"

syspath="$(dirname $(realpath /sys/class/block/$(basename $writable_part)))"
device="$(realpath /dev/block/$(cat $syspath/dev))"
partition=$(cat $syspath/$(basename $writable_part)/partition)

device_size="$(($(cat $syspath/size)/2))"
sum_size="$(($(grep $(basename $device)[a-z0-9] /proc/partitions|\
    tr -s ' '|cut -d' ' -f4|tr '\n' '+'|sed 's/+$//')))"

get_end()
{
    NUM=$1
    lastpart="$(grep -cE ^'[0-9]{1,}': $TMPFILE)"
    if [ "$lastpart" = "$NUM" ]; then
        endsize="$(parted -ms $DEV print| grep ^/ | cut -d: -f2)"
    else
        # we are not at the end ! get the start of the next partition
        # (minus 1 byte) instead of using the absolute end of the disk
        endsize=$(($(parted -ms $DEV unit B print|grep ^$(($num+1)):|\
            cut -d: -f2|sed 's/B$//')-1))
    fi
    echo "$endsize"
}

do_gpt()
{
    DISK=$1

    PARTNUM="$(sgdisk -p $DISK|grep writable|sed -r 's/^([^ ]*[ ]*){1}([^ ]*).*/\2/')"
    GUID="$(sgdisk -i $PARTNUM $DISK|grep unique| sed 's/^.*: //g')"
    FIRST="$(sgdisk -i $PARTNUM $DISK|grep ^First| sed 's/^.*: //g;s/ .*$//')"

    echo "fixing backup GPT" >>$LOGFILE 2>&1
    sgdisk --move-second-header $DISK >>$LOGFILE 2>&1

    echo "Deleting partition $PARTNUM" >>$LOGFILE 2>&1
    sgdisk -d $PARTNUM $DISK >>$LOGFILE 2>&1

    echo "Creating partition $PARTNUM at $FIRST" >>$LOGFILE 2>&1
    sgdisk -n $PARTNUM:$FIRST:0 $DISK >>$LOGFILE 2>&1

    echo "Setting GUID of partition $PARTNUM to $GUID" >>$LOGFILE 2>&1
    sgdisk -u $PARTNUM:$GUID $DISK >>$LOGFILE 2>&1

    echo "Setting name of $PARTNUM to writable" >>$LOGFILE 2>&1
    sgdisk -c $PARTNUM:writable $DISK >>$LOGFILE 2>&1

    sgdisk -p $DISK >/run/initramfs/new-gpt-table.txt 2>/dev/null
}

do_mbr()
{
    DEV=$1
    PART=$2
    endsize=$(get_end $PART)
    parted -s $DEV resizepart $PART $endsize
}


free_space=$(($device_size-$sum_size))
min_free_space=$(($device_size/10))

if [ "$min_free_space" -lt "$free_space" ]; then
    echo "initrd: found more than 10% free space on disk, resizing ${writable_part}" >/dev/kmsg || true
    echo "initrd: partition to full disk size, see ${LOGFILE} for details" >/dev/kmsg || true
    # back up the original partition table for later use or debugging
    parted -ms $device unit B print >$TMPFILE 2>/dev/null
    # grow our selected partition to max space available
    table="$(parted -ms $device print| grep ^/| cut -d: -f6)"
    case $table in
        gpt)
            # do_gpt needs the device name
            do_gpt $device >>$LOGFILE 2>&1
            ;;
        mbr|msdos)
            # do_mbr needs the device node and partition number
            do_mbr $device $partition >>$LOGFILE 2>&1
            resizeopts="-f"
            ;;
        *)
            echo "unknown partition table type, not resizing" >>$LOGFILE
            exit 0
            ;;
    esac
    # make sure the partitions are ready for further use
    udevadm settle >>$LOGFILE 2>&1
    # check the filesystem before attempting re-size
    e2fsck -fy $writable_part >>$LOGFILE 2>&1
    # resize the filesystem to full size of the partition
    resize2fs $resizeopts $writable_part >>$LOGFILE 2>&1
fi
