#!/bin/sh
set -e

usage_exit()
{
	echo
	echo "usage: $0 src [--layer=tarball]... dest [dest]..."
	echo
	echo "example: copying image to devices: sde, sdf, sdg"
	echo "$0 lx-trainer.img /dev/sde /dev/sdf /dev/sdg"
	echo
	exit 1
}

if [ `id -u` -ne 0 ]; then
	echo "error: sorry, this script must be run as root"
	exit 1
fi

# minimum 2 arguments
if [ $# -lt 2 ]; then
	echo "error: invalid arguments"
	usage_exit
fi

# gather arguments
SRC=""
LAYERS=""
DESTS=""

for arg in $@; do
	case $arg in
	--layer=*)
		LAYERS="$LAYERS `echo $arg | sed -e 's/^--layer=//'`"
		;;
	--*)
		echo "error: unknown option: $arg"
		usage_exit
		;;
	*)
		if [ -z "$SRC" ]; then
			SRC="$arg"
		else
			DESTS="$DESTS $arg"
		fi
		;;
	esac
done

# source must be file or block device
if [ ! -f "$SRC" -a ! -b "$SRC" ]; then
	echo "error: invalid src"
	usage_exit
fi

# destination must be block device
for dest in $DESTS; do
	if [ ! -b $dest ]; then
		echo "error: invalid dest: $dest"
		usage_exit
	fi
done

# delete mbr's and rescan devices
dd if=/dev/zero bs=1M count=10 | tee $DESTS > /dev/null
partprobe $DESTS

# efficiently copy source to all destinations and rescan devices
cat $SRC | tee $DESTS > /dev/null
partprobe $DESTS

# add 2nd partition
for dest in $DESTS; do
	/bin/echo -e "n\np\n\n\n\nw" | fdisk $dest
done

# rescan devices
partprobe $DESTS

# wait for partitions to appear
for dest in $DESTS; do
	while [ ! -b ${dest}2 ]; do
		echo "waiting for ${dest}2..."
		sleep 1
	done
done

# create ext4 on 2nd partition
for dest in $DESTS; do
	mkfs.ext4 -L lxhome ${dest}2 &
done
wait

# setup temp directory for mountpoints
TMP_ROOT="/tmp/dd-multi-`date +%s`.$$"
rm -rf $TMP_ROOT
mkdir -p $TMP_ROOT
echo "using temp directory $TMP_ROOT"

for dest in $DESTS; do
	# create mountpoints
	mkdir -p ${TMP_ROOT}${dest}1
	mkdir -p ${TMP_ROOT}${dest}2

	# mount partitions
	mount ${dest}1 ${TMP_ROOT}${dest}1
	mount ${dest}2 ${TMP_ROOT}${dest}2

	# move home directories to 2nd partition
	mv ${TMP_ROOT}${dest}1/home/* ${TMP_ROOT}${dest}2/

	# setup 2nd partition to be mounted as /home
	echo 'LABEL=lxhome /home ext4 defaults 0 0' | \
		tee -a ${TMP_ROOT}${dest}1/etc/fstab

	# copy layer tarballs to /home
	for tarball in $LAYERS; do
		destfile="${TMP_ROOT}${dest}2/`basename $tarball`"
		if [ -f $destfile ]; then
			echo
			echo "WARNING: OVERWRITING $destfile" 1>&2
			echo
			sleep 1
		fi
		cp $tarball $destfile
	done

	# remount home to /home
	umount ${TMP_ROOT}${dest}2
	mount ${dest}2 ${TMP_ROOT}${dest}1/home

	# unpack layers
	for tarball in $LAYERS; do
		destfile=`basename $tarball`
		chroot ${TMP_ROOT}${dest}1 tar -x -f /home/$destfile --numeric-owner -C /
		rm ${TMP_ROOT}${dest}1/home/$destfile
	done

	# unmount partitions
	umount ${TMP_ROOT}${dest}1/home
	umount ${TMP_ROOT}${dest}1
done

# cleanup temp directory
rm -rf $TMP_ROOT