# -*- mode: sh; sh-basic-offset: 3; indent-tabs-mode: nil; -*-
###############################################################
#
#  This handler slowly creates a backup of each user's maildir
#  to a remote server. It is designed to be run with low overhead
#  in terms of cpu and bandwidth so it runs pretty slow.
#
#  if destdir is /backup/maildir/, then it will contain the files
#    daily.1
#    daily.2
#    daily.3
#    weekly.1
#    weekly.2
#    monthly.1
#  if keepdaily is 3, keepweekly is 2, and keepmonthly is 1. 
#
#  The basic algorithm is to rsync each maildir individually,
#  and to use hard links for retaining historical data.
#
#  We rsync each maildir individually because it becomes very
#  unweldy to start a single rsync of many hundreds of thousands
#  of files. 
#
#  For the backup rotation to work, destuser must be able to run 
#  arbitrary bash commands on the desthost.
#
##############################################################

getconf rotate yes
getconf remove yes

getconf loadlimit 5
getconf speedlimit 0
getconf keepdaily 5
getconf keepweekly 3
getconf keepmonthly 1

getconf srcdir /var/maildir
getconf destdir
getconf desthost
getconf destport 22
getconf destuser

failedcount=0

# strip trailing /
destdir=${destdir%/}
srcdir=${srcdir%/}

# used for testing
#getconf letter
#getconf testuser elijah
getconf backup yes
#letters=e
letters="a b c d e f g h i j k l m n o p q r s t u v w x y z"

[ -d $srcdir ] || fatal "source directory $srcdir doesn't exist"

[ ! $test ] || testflags="--dry-run -v"
rsyncflags="$testflags -e 'ssh -p $destport' -r -v --ignore-existing --delete --size-only --bwlimit=$speedlimit"
excludes="--exclude '.Trash/\*' --exclude '.Mistakes/\*' --exclude '.Spam/\*'"

# see if we can login
debug "ssh -o PasswordAuthentication=no $desthost -l $destuser 'echo -n 1'"
if [ ! $test ]; then
	result=`ssh -o PasswordAuthentication=no $desthost -l $destuser 'echo -n 1' 2>&1`
	if [ "$result" != "1" ]; then
		fatal "Can't connect to $desthost as $destuser."
	fi
fi

##################################################################
### FUNCTIONS

function do_user() {
	local user=$1
	local destdir=$2
	local letter=${user:0:1}
	local dir="$srcdir/$letter/$user"
	[ -d $dir ] || fatal "maildir $dir not found".

#	while true; do
#		load=`uptime | sed 's/^.*load average: \\([^,]*\\).*$/\\1/'`
#		over=`expr $load \> $loadlimit`
#		if [ $over == 1 ]; then
#			info "load $load, sleeping..."
#			sleep 600
#		else
#			break
#		fi
#	done
	
  	cmd="$RSYNC $rsyncflags $excludes $dir $destuser@$desthost:$destdir/$letter"
	ret=`rsync -e "ssh -p $destport" -r \
--links --ignore-existing --delete --size-only --bwlimit=$speedlimit \
--exclude '.Trash/*' --exclude '.Mistakes/*' --exclude '.Spam/*' \
$dir $destuser@$desthost:$destdir/$letter \
2>&1`
	ret=$?
	# ignore 0 (success) and 24 (file vanished before it could be copied)
	if [ $ret != 0 -a $ret != 24 ]; then
		warning "rsync $user failed"
		warning "  returned: $ret"
		let "failedcount = failedcount + 1"
		if [ $failedcount -gt 100 ]; then
			fatal "100 rsync errors -- something is not working right. bailing out."
		fi
	fi
}

# remove any maildirs from backup which might have been deleted
# and add new ones which have just been created.

function do_remove() {
	local tmp1=`maketemp maildir-tmp-file`
	local tmp2=`maketemp maildir-tmp-file`
	
	for i in a b c d e f g h i j k l m n o p q r s t u v w x y z; do
		ls -1 "$srcdir/$i" | sort > $tmp1
		ssh -p $destport $desthost ls -1 '$destdir/maildir/$i' | sort > $tmp2
		for deluser in `join -v 2 $tmp1 $tmp2`; do
			cmd="ssh -p $destport $desthost rm -vr '$destdir/maildir/$i/$deluser/'"
			debug $cmd
		done
	done
	rm $tmp1
	rm $tmp2	
}

function do_rotate() {
	backuproot=$destdir

(
	debug Connecting to $desthost
	ssh -T -o PasswordAuthentication=no $desthost -l $destuser <<EOF
##### BEGIN REMOTE SCRIPT #####
	seconds_daily=86400
	seconds_weekly=604800
	seconds_monthly=2628000
	keepdaily=$keepdaily
	keepweekly=$keepweekly
	keepmonthly=$keepmonthly
	now=\`date +%s\`

	for rottype in daily weekly monthly; do
		seconds=\$((seconds_\${rottype}))

		dir="$backuproot/\$rottype"
		if [ ! -d \$dir.1 ]; then
			echo "Info: \$dir.1 does not exist. This backup is missing, so we are skipping the rotation."
			continue 1
		elif [ ! -f \$dir.1/created ]; then
			echo "Warning: \$dir.1/created does not exist. This backup may be only partially completed. Skipping rotation."
			continue 1
		fi
		
		# Rotate the current list of backups, if we can.
		oldest=\`find $backuproot -type d -maxdepth 1 -name \$rottype'.*' | sed 's/^.*\.//' | sort -n | tail -1\`
		echo "Debug: oldest \$oldest"
		[ "\$oldest" == "" ] && oldest=0
		for (( i=\$oldest; i > 0; i-- )); do
			if [ -d \$dir.\$i ]; then
				if [ -f \$dir.\$i/created ]; then
					created=\`tail -1 \$dir.\$i/created\`
				else
					created=0
				fi
				cutoff_time=\$(( now - (seconds*(i-1)) ))
				if [ ! \$created -gt \$cutoff_time ]; then
					next=\$(( i + 1 ))
					if [ ! -d \$dir.\$next ]; then
						echo "Debug: mv \$dir.\$i \$dir.\$next"
						mv \$dir.\$i \$dir.\$next
						date +%c%n%s > \$dir.\$next/rotated
					else
						echo "Info: skipping rotation of \$dir.\$i because \$dir.\$next already exists."
					fi
				else
					echo "Info: skipping rotation of \$dir.\$i because it was created" \$(( (now-created)/86400)) "days ago ("\$(( (now-cutoff_time)/86400))" needed)."
				fi
			fi
		done
	done

	max=\$((keepdaily+1))
	if [ \( \$keepweekly -gt 0 -a -d $backuproot/daily.\$max \) -a ! -d $backuproot/weekly.1 ]; then
		echo mv $backuproot/daily.\$max $backuproot/weekly.1
		mv $backuproot/daily.\$max $backuproot/weekly.1
		date +%c%n%s > $backuproot/weekly.1/rotated
	fi

	max=\$((keepweekly+1))
	if [ \( \$keepmonthly -gt 0 -a -d $backuproot/weekly.\$max \) -a ! -d $backuproot/monthly.1 ]; then
		echo mv $backuproot/weekly.\$max $backuproot/monthly.1
		mv $backuproot/weekly.\$max $backuproot/monthly.1
		date +%c%n%s > $backuproot/monthly.1/rotated
	fi

	for rottype in daily weekly monthly; do
		max=\$((keep\${rottype}+1))
		dir="$backuproot/\$rottype"
		oldest=\`find $backuproot -type d -maxdepth 1 -name \$rottype'.*' | sed 's/^.*\.//' | sort -n | tail -1\`
		[ "\$oldest" == "" ] && oldest=0 
		# if we've rotated the last backup off the stack, remove it.
		for (( i=\$oldest; i >= \$max; i-- )); do
			if [ -d \$dir.\$i ]; then
				if [ -d $backuproot/rotate.tmp ]; then
					echo "Info: removing $backuproot/rotate.tmp"
					rm -rf $backuproot/rotate.tmp
				fi
				echo "Info: moving \$dir.\$i to $backuproot/rotate.tmp"
				mv \$dir.\$i $backuproot/rotate.tmp
			fi
		done
	done
####### END REMOTE SCRIPT #######
EOF
) | (while read a; do passthru $a; done)

}


function setup_remote_dirs() {
	local backuptype=$1
	local dir="$destdir/$backuptype"

(
	ssh -T -o PasswordAuthentication=no $desthost -l $destuser <<EOF
		if [ ! -d $destdir ]; then
			echo "Fatal: Destination directory $destdir does not exist on host $desthost."
			exit 1
		elif [ -d $dir.1 ]; then
			if [ -f $dir.1/created ]; then
				echo "Warning: $dir.1 already exists. Overwriting contents."
			else
				echo "Warning: we seem to be resuming a partially written $dir.1"
			fi
		else
			if [ -d $destdir/rotate.tmp ]; then
				mv $destdir/rotate.tmp $dir.1
				if [ \$? == 1 ]; then
					echo "Fatal: could mv $destdir/rotate.tmp $dir.1 on host $desthost"
					exit 1
				fi
			else
				mkdir $dir.1
				if [ \$? == 1 ]; then
					echo "Fatal: could not create directory $dir.1 on host $desthost"
					exit 1
				fi
				for i in a b c d e f g h i j k l m n o p q r s t u v w y x z; do
					mkdir $dir.1/\$i
				done
			fi
			if [ -d $destdir/$backuptype.2 ]; then
				echo "Info: updating hard links to $dir.1. This may take a while."
				cp -alf $destdir/$backuptype.2/. $dir.1
				#if [ \$? == 1 ]; then
				#	echo "Fatal: could not create hard links to $dir.1 on host $desthost"
				#	exit 1
				#fi
			fi
		fi
		[ -f $dir.1/created ] && rm $dir.1/created
		[ -f $dir.1/rotated ] && rm $dir.1/rotated
		exit 0
EOF
) | (while read a; do passthru $a; done)

	if [ $? == 1 ]; then exit; fi
}

###
##################################################################

### ROTATE BACKUPS ###

if [ "$rotate" == "yes" ]; then
	do_rotate
fi

### REMOVE OLD MAILDIRS ###

if [ "$remove" == "yes" ]; then
	debug remove
fi

### MAKE BACKUPS ###

if [ "$backup" == "yes" ]; then
	if [ $keepdaily -gt 0 ]; then btype=daily
	elif [ $keepweekly -gt 0 ]; then btype=weekly
	elif [ $keepmonthly -gt 0 ]; then btype=monthly
	else fatal "keeping no backups"; fi

	setup_remote_dirs $btype
	
	for i in $letters; do
		[ -d "$srcdir/$i" ] || fatal "directory $srcdir/$i not found."
		cd "$srcdir/$i"
		debug $i
		for user in `ls -1`; do
			if [ "$testuser" != "" -a "$testuser" != "$user" ]; then continue; fi
			do_user $user $destdir/$btype.1
		done
	done

	ssh -o PasswordAuthentication=no $desthost -l $destuser "date +%c%n%s > $destdir/$btype.1/created"
fi