#!/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=
	subdir=.
	rsyncopts=
	rsynccompress=z
	sshopts=
	summer=summer


# snaprsync
#
# This file is part of chiark backup, a system for backing up GNU/Linux and
# other UN*X-compatible machines, as used on chiark.greenend.org.uk.
#
# chiark backup is:
#  Copyright (C) 1997-1998,2000-2001,2007
#                     Ian Jackson <ian@chiark.greenend.org.uk>
#  Copyright (C) 1999 Peter Maydell <pmaydell@chiark.greenend.org.uk>
#
# This is free software; you can redistribute it and/or modify it under the
# terms of the GNU General Public License as published by the Free Software
# Foundation; either version 3, or (at your option) any later version.
#
# This is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
# details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, consult the Free Software Foundation's
# website at www.fsf.org, or the GNU Project website at www.gnu.org.


set -e

badusage () { echo >&2 "snaprsync: bad usage: $1"; exit 12; }
nb_echo () { (echo "$@"); } # See Debian #382798
x () { nb_echo "+ $@"; "$@"; }
xspawned () { eval "${1}pid=$!; nb_echo \"+[$!] ($1) &\";"; }
xwait () { eval "nb_echo \"+[\$${1}pid] ($1)...\"; wait \$${1}pid;"; }

while true; do
	case "$1" in
	--?*=*)
		name=${1#--}; name=${name%%=*}
		value=${1#--*=}
		case "$name" in
		rhost|device|mountpoint|localarea);;
		localprevious|snapkind|rsharedir|retcdir|rvardir|bwlimit);;
		subdir|rsyncopts|rsynccompress|sshopts|summer);;
		*) 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 $sshopts"
sshpfx='PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin; export PATH; '

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

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

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 $sshopts $rhost "$sshpfx $rsharedir/snap-drop $rvardir"
x ssh $sshopts $rhost "
	$sshpfx
	set -e
	cd $rvardir
	echo '$retcdir/snap/$snapkind drop $rvardir' >snap-drop.new
	mv snap-drop.new snap-drop
"
x ssh $sshopts $rhost "$sshpfx $retcdir/snap/$snapkind snap $rvardir $device $mountpoint"
ssh $sshopts $rhost <$td/sentinel 4<&- "
  $sshpfx
  set -e
  date -u '+$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
  $summer . >&3
  date -u '+$rhost $datefmt sumsdone'
  cd ..
" &
xspawned rsum
x $rsync -aHSx$rsynccompress --numeric-ids --delete $rsyncopts \
	${localprevious:+--link-dest} $localprevious \
	$rhost:$rvardir/snap-mount/$subdir $localarea/.
date -u "+ $datefmt rsyncdone"

exec 3>$localarea,lsums
(cd $localarea && \
 $summer . >&3) &
xspawned lsum
exec 3>&-

xwait rsum
exec 4<&-
date -u "+ $datefmt sumsdone"
x ssh $sshopts $rhost "$sshpfx $rsharedir/snap-drop $rvardir"

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

xwait $lsum
date -u "+ $datefmt checking"

set +e
diff -u <(sed -e 's/^mountpoint/dir       /' "$localarea,rsums") \
  "$localarea,lsums" >"$localarea,sumsdiff"
diffrc=$?
set -e
test $diffrc = 0 || test $diffrc = 1

date -u "+ $datefmt checked $diffrc"
rc=$diffrc