#!/bin/sh

set -e

mkdir -p /mnt/urbackup_snaps

CDIR=`dirname $0`

SNAP_ID=$1
SNAP_MOUNTPOINT="$2"
SNAP_DEST=/mnt/urbackup_snaps/$SNAP_ID
SNAP_MOUNTPOINT_SAN=$(echo "$SNAP_MOUNTPOINT" | sed 's@/@_@g')
SNAP_NUM_PATH="/mnt/urbackup_snaps/cbt_info/$SNAP_MOUNTPOINT_SAN-snapdev"
SNAP_COWFILE_PATH="/mnt/urbackup_snaps/cbt_info/$SNAP_MOUNTPOINT_SAN-cowfile"

exists()
{
	[ -e "$1" ]
}

has_num ()
{
	exists /mnt/urbackup_snaps/cbt_info/*-snapdev && grep "$1" /mnt/urbackup_snaps/cbt_info/*-snapdev > /dev/null
}

get_path()
{
	echo $1/$2 | sed 's@//@/@g'
}


CDIR=`dirname $0`
. $CDIR/filesystem_snapshot_common
exit_exclude_snapshot_mountpoints "$SNAP_MOUNTPOINT"

DEVICE=$(df -T -P | egrep " ${SNAP_MOUNTPOINT}\$" | head -n 1 | tr -s " " | cut -d" " -f1)
set_filesystem_type "${SNAP_MOUNTPOINT}"

if [ "x$TYPE" = "x" ]
then
        if btrfs subvolume list -o "$SNAP_MOUNTPOINT" > /dev/null 2>&1
        then
                TYPE="btrfs"
        fi
fi

if [ "x$TYPE" = "xbtrfs" ]
then
    $CDIR/btrfs_create_filesystem_snapshot "$@"
    exit $?
fi

if [ "x$DEVICE" = "x" ]
then
    echo "Cannot get device for filesystem $SNAP_MOUNTPOINT"
    exit 1
fi

echo "Snapshotting device $DEVICE via dattobd..."

NUM=0

while [ -e "/dev/datto$NUM" ] || has_num $NUM
do
        NUM=`expr $NUM + 1`
done

if ! modprobe dattobd
then
	echo "Dattobd kernel module not available"
	exit 1
fi

sync

TRY_TRANS=0
if [ -e "$SNAP_COWFILE_PATH" ] && [ -e "$SNAP_NUM_PATH" ]
then
	TRY_TRANS=1
	TRANS_NUM=$(cat "$SNAP_NUM_PATH")
	echo "Trying to transition /dev/datto$TRANS_NUM to snapshot..."
	echo "dbdctl transition-to-snapshot $(get_path $SNAP_MOUNTPOINT "datto_3d41c58e-6724-4d47-8981-11c766a08a24_$SNAP_ID") $TRANS_NUM"
fi

if [ $TRY_TRANS = 1 ] && dbdctl transition-to-snapshot $(get_path $SNAP_MOUNTPOINT ".datto_3d41c58e-6724-4d47-8981-11c766a08a24_$SNAP_ID") $TRANS_NUM
then
	echo "Transitioned /dev/datto$TRANS_NUM to snapshot."
	CBT_FILE=$(cat $SNAP_COWFILE_PATH)
	echo "CBT_FILE=$CBT_FILE"
	echo "CBT=type=datto"
	NUM=$TRANS_NUM
else
	if [ $TRY_TRANS = 1 ]
	then
		rm "$SNAP_NUM_PATH"
		rm "$SNAP_COWFILE_PATH"
	fi

	echo "Using /dev/datto$NUM..."
	
	echo "CBT=type=datto&reset=1"
	dbdctl setup-snapshot "$DEVICE" $(get_path $SNAP_MOUNTPOINT ".datto_3d41c58e-6724-4d47-8981-11c766a08a24_$SNAP_ID") $NUM
fi

echo $NUM > ${SNAP_DEST}-num

DEV_SIZE=`blockdev --getsize /dev/datto$NUM`

truncate -s100M $(get_path $SNAP_MOUNTPOINT ".overlay_2fefd007-3e48-4162-b2c6-45ccdda22f37_$SNAP_ID")

LODEV=`losetup -f`

if [ "x$LODEV" = x ]
then
	rm "${SNAP_DEST}-num"
	rm $(get_path $SNAP_MOUNTPOINT ".overlay_2fefd007-3e48-4162-b2c6-45ccdda22f37_$SNAP_ID")
	dbdctl destroy $NUM
    exit 1
fi

losetup $LODEV $(get_path $SNAP_MOUNTPOINT ".overlay_2fefd007-3e48-4162-b2c6-45ccdda22f37_$SNAP_ID")

echo "0 $DEV_SIZE snapshot /dev/datto$NUM $LODEV N 8" | dmsetup create "wsnap-$SNAP_ID"

echo "Mounting /dev/mapper/wsnap-$SNAP_ID..."

mkdir -p $SNAP_DEST
mkdir -p /mnt/urbackup_snaps/cbt_info

MOUNTOPTS="ro"

if [ $TYPE = "xfs" ]
then
    MOUNTOPTS="ro,nouuid"
fi

if ! mount -o $MOUNTOPTS /dev/mapper/wsnap-$SNAP_ID $SNAP_DEST
then
    echo "Mounting filesystem failed"
    rmdir "$SNAP_DEST"
    rm "${SNAP_DEST}-num"
    dmsetup remove "wsnap-$SNAP_ID"
	losetup -d $LODEV
    rm $(get_path $SNAP_MOUNTPOINT ".overlay_2fefd007-3e48-4162-b2c6-45ccdda22f37_$SNAP_ID")
    dbdctl destroy $NUM
    exit 1
fi

echo "/dev/datto$NUM" > ${SNAP_DEST}-dev
echo "$NUM" > $SNAP_NUM_PATH
echo $(get_path $SNAP_MOUNTPOINT ".datto_3d41c58e-6724-4d47-8981-11c766a08a24_$SNAP_ID") > $SNAP_COWFILE_PATH
echo "SNAPSHOT=$SNAP_DEST"

exit 0