#!/bin/bash 

BACKUP_DIR=/mnt/opt/data/
SSH_HOST=cluster.univ@se.imbg.org.ua
SSH_PORT=3322
RSYNC_DEST_BASE=/srv/backups/cluster.univ/opt
RSYNC_SUDO=yes
#RSYNC_VERBOSE=1

# backup from DRBD-master a-node only
grep -q '/mnt/opt' /proc/mounts || exit 0

# lock in case of looooong backup
LOCK_FILE=/run/lock/rsync-opt
[ -f "$LOCK_FILE" ] && exit 0
trap "rm -f $LOCK_FILE" EXIT SIGINT SIGTERM
touch "$LOCK_FILE"

current_timestamp () {
    date +'%Y%m%d'
}

find_last_backup_script () {
cat <<END
#!/bin/bash
cd ${RSYNC_DEST_BASE}
find . -mindepth 1 -maxdepth 1 -type d | sed '/^\.\/$(current_timestamp)$/d' | sed -n '\$p'
END
}

do_rsync () {
	local localdir=$1
	local remotedir=$2

	local verbosity="--quiet --no-motd"
	[ -n "${RSYNC_EXCLUDE}" ] && excludefile="--exclude-from=${RSYNC_EXCLUDE}"
	[ -n "${RSYNC_VERBOSE}" ] && verbosity="--human-readable --progress"
	local rshcmd="ssh"
	[ -n "${SSH_PORT}" ] && rshcmd=ssh\ -p\ ${SSH_PORT}
	[ -n "${RSYNC_SUDO}" ] && rsyncpath=--rsync-path=sudo\ rsync
	[ -n "${RSYNC_DRY_RUN}" ] && dry_run=--dry-run\ --itemize-changes

	rsync --archive --links --recursive \
        	--hard-links --perms --owner --group \
		--devices --specials --times --sparse \
	        --compress --compress-level=9 ${excludefile} \
        	--rsh="$rshcmd" "$rsyncpath" --delete ${dry_run} \
		--numeric-ids ${verbosity} $RSYNC_LINK_DEST \
	        "${localdir}" "${remotedir}"
}

# put the simple script to find last backup on remote share
find_last_backup_script | ssh -p ${SSH_PORT} ${SSH_HOST} "cat > $RSYNC_DEST_BASE/find_last_backup.sh"

# execute the script to get last backup dir
last_backup=$( ssh -p ${SSH_PORT} ${SSH_HOST} "/bin/bash $RSYNC_DEST_BASE/find_last_backup.sh" )
if [ -n "$last_backup" ]; then
    if [ "$last_backup" != "./$( current_timestamp )" ]; then
        RSYNC_LINK_DEST=" --link-dest=.${last_backup}"
    fi
fi

RSYNC_DEST_URL="${SSH_HOST}:${RSYNC_DEST_BASE}/$( current_timestamp )"

changes=$( RSYNC_DRY_RUN=1 do_rsync ${BACKUP_DIR} ${RSYNC_DEST_URL} | wc -l )

if [ $changes -ne 0 ]; then
    do_rsync ${BACKUP_DIR} ${RSYNC_DEST_URL}
fi