#!/usr/bin/env bash

set -e

ROOT_DIRECTORY=$1
SUBVOLUME=$2

TARGET_SUBVOLUME="${ROOT_DIRECTORY}/${SUBVOLUME}"
SNAPSHOT_DIRECTORY="${ROOT_DIRECTORY}/@snapshots"

if [ "${ROOT_DIRECTORY}" == "" ]
then
	echo "No root directory provided"
	exit 1
fi

if [ ! -d "${SNAPSHOT_DIRECTORY}" ]
then
	echo "No snapshot directory in root ${ROOT_DIRECTORY}"
	exit 1
fi

if [ "${SUBVOLUME}" == "" ]
then
	echo "No subvolume provided"
	exit 1
fi

LATEST_SNAPSHOT=$(ls ${ROOT_DIRECTORY}/@snapshots/ | grep "${SUBVOLUME}\." | awk '{ print length, $0 }' | sort | tail -n 1 | awk '{ print $2 }')

SNAPSHOT_PATH="${SNAPSHOT_DIRECTORY}/${LATEST_SNAPSHOT}"

if [ ! -d "${SNAPSHOT_PATH}" ] || [ "${LATEST_SNAPSHOT}" == "" ]
then
	echo "Couldn't find latest snapshot for subvolume ${SUBVOLUME}"
	exit 1
fi

if [ -d "${TARGET_SUBVOLUME}" ]
then
	echo "Removing existing subvolume"
	btrfs subvolume delete "${TARGET_SUBVOLUME}"
fi

echo "Snapshotting ${SNAPSHOT_PATH} into ${TARGET_SUBVOLUME}"
btrfs subvolume snapshot "${SNAPSHOT_PATH}" "${TARGET_SUBVOLUME}"