#! /bin/sh
# vim:ts=4:sw=4:
set -e
HOSTS="backup.niet.verweg.com"
POOLS="system"
BACKUP_PATH="${1}"
for backup_host in $HOSTS; do
	if nc -w 5 $backup_host 22 2>&1 > /dev/null; then
		for pool in $POOLS; do
			last_snapshot=$(zfs list -H -o name -t snap -r -d 1 $pool | tail -1)
			last_send_snapshot_file="/var/db/backup/last-${backup_host}-${pool}"
			test -f ${last_send_snapshot_file} && last_send_snapshot=$(cat ${last_send_snapshot_file}) || last_send_snapshot=""
			if [ "${last_snapshot}" != "${pool}@${last_send_snapshot}" ]; then
				test -n "${last_send_snapshot}" && incremental_opt="-I ${pool}@${last_send_snapshot}"
				echo zfs send -n -vR ${incremental_opt} ${last_snapshot}
				zfs send -n -vR ${incremental_opt} ${last_snapshot} 2>&1 | \
						tail -1 | \
						tee /var/tmp/backup-${backup_host}-$$.log
				if [ -n "${BACKUP_PATH}" -a -d "${BACKUP_PATH}" ]; then
					zfs send -vR ${incremental_opt} ${last_snapshot} | \
							zstd -v -6 --long > ${BACKUP_PATH}/${pool}-${backup_host}-${last_snapshot}.zstd | \
							tee -a /var/tmp/backup-${backup_host}-$$.log
					echo "Stored backup in ${BACKUP_PATH}/${pool}-${backup_host}-${last_snapshot}.zstd" 
					echo "rsync this to the other server and use as input"
				else
					zfs send -vR ${incremental_opt} ${last_snapshot} | \
							zstd -v -6 --long | \
							ssh ${backup_host} $pool | \
							tee -a /var/tmp/backup-${backup_host}-$$.log
				fi
				status=$(tail -1 /var/tmp/backup-${backup_host}-$$.log)
				echo ${last_snapshot} | sed -e "s/${pool}@//"
				if [ "${status}" = "OK" ]; then
					echo ${last_snapshot} | sed -e "s/${pool}@//" >  ${last_send_snapshot_file}
					mv /var/tmp/backup-${backup_host}-$$.log /var/log/zfs-backup-${backup_host}-${pool}-$(date +%a).log
				fi
			else
				echo "Backup for $pool up to date for ${backup_host}"
			fi
		done
	else
		echo "WARNING: $backup_host not reachable over IPv6"
	fi
done