#!/bin/bash

HOST=`hostname -s | titlecase`

TEMP=`getopt -o e:h:n: -n 'undodelta' -- "$@"`

if [ $? != 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi

eval set -- "$TEMP"

while true ; do
        case "$1" in
               -e)
                        EXT=.$2
                        shift 2
                        ;;
               -h)
                        HOST=$2
                        shift 2
                        ;;
               -n)
                        NAME=/$2
                        shift 2
                        ;;
                --)
                        shift
                        break
                        ;;
                *) echo "Internal error!" ; exit 1 ;;
        esac
done

if [ $# -ne 1 ]
then
	echo $0 '[-h hostname] [-e fileextension] [-n name] backuproot'
	exit 1
fi

if [ ! -f $1/.backup ]
then
	echo Not a backup directory root.
	exit 1
fi

DESTDIR=$1/$HOST$NAME

UNDO=$DESTDIR/undo-`date --iso-8601`${EXT}.patch
NEW=$DESTDIR/new$EXT
CURRENT=$DESTDIR/current$EXT

cat > $NEW

if [ ! -s $NEW ]
then
	echo Database $HOST$NAME is missing.
	rm $NEW
elif [ -r $CURRENT ]
then
	diff -u $NEW $CURRENT > $UNDO
	if [ -r $NEW -a -r $UNDO ]
	then
		if [ ! -s $UNDO ]
		then
			rm $UNDO
		fi
	
		mv $NEW $CURRENT
	else
		echo Failed to do undo delta to $CURRENT! 2>&1
	fi
else
	mv $NEW $CURRENT
fi