#!/bin/sh -euf

SNAPSHOT_DIRECTORY="/var/backups/dataset-snapshots"

usage() (
	echo "backup-dataset.sh <dataset> <duplicity destination> [duplicity options]"
	echo
	echo "Performs a duplicity incremental backup of the specified dataset."
	echo "An atomic snapshot of the dataset is taken prior to backing up."
	echo
)

backup_dataset() (
	DATASET="$1"
	DESTINATION="$2"
	DUPLICITY_OPTIONS="$3"

	sudo snap.sh snap "$DATASET"
	PASSPHRASE="null" duplicity $DUPLICITY_OPTIONS "$SNAPSHOT_DIRECTORY/$DATASET" "$DESTINATION"
	sudo snap.sh free "$DATASET"
)

case "${1:-help}" in
	"help")	usage;;
	*)	backup_dataset "$1" "$2" "${3:-}";;
esac