#!/bin/bash
#
# usage: snaprsync <setting>... <positionals>
#  <setting> is ---<name>=<value>
#  <positionals> are assigned to unused mandatory values in order
# mandatory:
#   rhost device mountpoint localarea 
# optional:
	localprevious=
	snapkind=lvm
	rsharedir=/usr/share/chiark-backup 
	retcdir=/etc/chiark-backup
	rvardir=/var/lib/chiark-backup
	bwlimit=

set -e

badusage () { echo >&2 "snaprsync: bad usage: $1"; exit 12; }
x () { echo "+ $@"; "$@"; }

while true; do
	case "$1" in
	--?*=?*)
		name=${1#--}; name=${name%%=*}
		value=${1#--*=}
		case "$name" in
		rhost|device|mountpoint|localarea);;
		localprevious|rsharedir|retcdir|rvardir|bwlimit);;
		*) badusage "unknown setting $name";;
		esac
		eval "$name=\$value"
		;;
	--)	shift; break ;;
	-*)	badusage "unknown option $1" ;;
	*)	break ;;
	esac
	shift
done

for name in rhost device mountpoint localarea; do
	eval "value=\$$name"
	if [ "x$value" != x ]; then continue; fi
	if [ $# = 0 ]; then badusage "no value for setting $name"; fi
	eval "$name=$1"
	shift
done

datefmt='%Y-%m-%d %H:%M:%S Z'
rsync="rsync ${bwlimit:+--bwlimit} $bwlimit"
export RSYNC_RSH='ssh -o compression=no'

ssh $rhost "date -u '+$rhost $datefmt start'"
ssh $rhost id
ssh $rhost ls -d $rsharedir
ssh $rhost ls -d $rvardir

test -d $localarea || x mkdir $localarea
ournode=`uname -n`
rsumsfile=for-$ournode.sums

td=/dev/enoent
rc=12
trap 'rm -rf $td; exit $rc' 0
td=`mktemp -td`

mkfifo -m 600 $td/sentinel
exec 4<>$td/sentinel

x ssh $rhost "$rsharedir/snap-drop"
x ssh $rhost "$retcdir/snap/$snapkind snap $rvardir $device $mountpoint"
ssh $rhost <$td/sentinel 4<&- "
  set -e
  date -u '+$rhost $datefmt main'
  exec 3<&0 0</dev/null
  (set +e; read x <&3; kill 0) &
  cd $rvardir
  umask 077
  exec 3>$rsumsfile
  cd snap-mount
  summer -Ctqf . | sort -t'	' -k2 >&3
  test x"${PIPESTATUS[*]}" = 'x0 0'
  date -u '+$rhost $datefmt sumsdone'
  cd ..
" &
rsumpid=$!
x $rsync -aHSxz --numeric-ids --delete \
	${localprevious:+--link-dest} $localprevious \
	$rhost:$rvardir/snap-mount/. $localarea/.
wait $rsumpid
x ssh $rhost "$rsharedir/snap-drop"

if [ "x${localprevious}" != x ]; then
	cp "$localprevious,rsums" "$localarea,rsums"
fi
x $rsync -p \
	$rhost:$rvardir/$rsumsfile \
	"$localarea,rsums"