#!/bin/bash

dm="grubtest"
size="6000000000" # units of 512 bytes
p1_size="+2T"
p2_size="+100M"

case $1 in
create|destroy|auto) ;;
*) echo "Usage: $0 <auto [sizes]|create|destroy <dir>>"; exit 1;;
esac

set -e

create() {
loop=`losetup -f`
tmpdir=`mktemp -d -u`

cat <<-EOF
Settings:
loop: $loop
tmpdir: $tmpdir
dmsetup: $dm
disk size: $(( size * 512 )) bytes
first partition size: $p1_size
second partition size: $p2_size

hit enter to goooooo
EOF
read

mkdir $tmpdir
pushd $tmpdir >/dev/null
echo ${loop} > loop
dd if=/dev/zero count=1 seek=$(( size - 1 )) obs=512 of=img
ls -lh img
losetup -v ${loop} img
devinfo=$(stat -c %t:%T ${loop})
echo "0 ${size} linear ${devinfo} 0" | dmsetup create $dm

p1="n\n\n\n${p1_size}\n\n"
p2="n\n\n\n${p2_size}\n\n"
fin="p\nw\ny\n"
gdisk /dev/mapper/$dm <<<"$(printf %b "$p1$p2$fin")"

kpartx -a /dev/mapper/$dm

mke2fs /dev/mapper/${dm}2
mkdir mnt
mount /dev/mapper/${dm}2 mnt
mkdir -p mnt/boot
rsync -a /boot/grub/ mnt/boot/grub/
echo "(hd0) /dev/mapper/${dm}" > mnt/boot/grub/device.map

printf 'root (hd0,1)\nsetup (hd0)\n' | grub --batch --device-map=$tmpdir/mnt/boot/grub/device.map

cat <<-EOF

############
Now run:
  printf 'root (hd0,1)\nsetup (hd0)\n' | grub --batch --device-map=$tmpdir/mnt/boot/grub/device.map
To cleanup:
  $0 destroy $tmpdir
EOF
}

destroy() {
tmpdir=$1
if [[ ! -d $tmpdir ]] ; then
	echo "Need the tmpdir; $tmpdir does not exist"
	exit 1
fi
pushd $tmpdir >/dev/null
loop=$(<loop)

if [[ -e mnt ]] ; then
	if ! rmdir mnt 2>/dev/null ; then
		umount mnt
		rmdir mnt
	fi
fi

if [[ -e /dev/mapper/${dm}1 ]] ; then
	kpartx -d /dev/mapper/${dm}
fi

if [[ -e /dev/mapper/$dm ]] ; then
	dmsetup remove $dm
fi

losetup -d ${loop}
rm img loop
cd /
rmdir $tmpdir
}

auto() {
case $# in
1) p1_size=$1 ;;
2) p1_size=$1 p2_size=$2 ;;
*) ;;
esac
create
d=$PWD
cd /
destroy $d
cat <<EOF

AUTOMATICALLY CLEANED UP HAVE A NICE DAY
EOF
}

"$@"