#!/bin/bash
# 
#   pacman-optimize
#  
#   Copyright (c) 2002-2006 by Judd Vinet <jvinet@zeroflux.org>
#  
#   This program 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 2 of the License, or
#   (at your option) any later version.
# 
#   This program 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, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 
#   USA.
#

myver='2.9.8'

usage() {
	echo "pacman-optimize $myver"
	echo "usage: $0 [pacman_db_root]"
	echo
	echo "pacman-optimize is a little hack that should improve the performance"
	echo "of pacman when reading/writing to its filesystem-based database."
	echo
	echo "Because pacman uses many small files to keep track of packages,"
	echo "there is a tendency for these files to become fragmented over time."
	echo "This script attempts to relocate these small files into one"
	echo "contiguous location on your hard drive.  The result is that the hard"
	echo "drive should be able to read them faster, since the hard drive head"
	echo "does not have to move around the disk as much."
	echo
}

die() {
	echo "pacman-optimize: $*" >&2
	exit 1
}

die_r() {
	rm -f /tmp/pacman.lck
	die $*
}


dbroot="/var/lib/pacman"

if [ "$1" != "" ]; then
	if [ "$1" = "-h" -o "$1" = "--help" ]; then
		usage
		exit 0
	fi
	dbroot=$1
fi

if [ "`id -u`" != 0 ]; then
	die "You must be root to optimize the database"
fi

# make sure pacman isn't running
if [ -f /tmp/pacman.lck ]; then
	die "Pacman lockfile was found.  Cannot run while pacman is running."
fi

if [ ! -d $dbroot ]; then
	die "$dbroot does not exist or is not a directory"
fi

# don't let pacman run while we do this
touch /tmp/pacman.lck

# step 1: sum the old db
echo "==> md5sum'ing the old database..."
find $dbroot -type f | sort | xargs md5sum >/tmp/pacsums.old 

# step 1: copy the entire db directory to a new one
echo "==> copying $dbroot..."
cp -a $dbroot $dbroot.new || die_r "error copying $dbroot"

# step 2: switch the directory names and sum the new one
echo "==> md5sum'ing the new database..."
mv $dbroot $dbroot.bak || die_r "error renaming $dbroot"
mv $dbroot.new $dbroot || die_r "error renaming $dbroot.new"
find $dbroot -type f | sort | xargs md5sum >/tmp/pacsums.new

# step 3: compare sums
echo "==> checking integrity..."
diff /tmp/pacsums.old /tmp/pacsums.new >/dev/null 2>&1
if [ $? -ne 0 ]; then
	# failed, move the old one back into place
	rm -rf $dbroot
	mv $dbroot.bak $dbroot
	die_r "integrity check FAILED, reverting to old database"
fi

# step 4: remove the backup
echo "==> removing old database..."
rm -rf $dbroot.bak || die_r "error removing backup $dbroot.bak"

# remove the lock and sum files
rm -f /tmp/pacman.lck /tmp/pacsums.old /tmp/pacsums.new

echo
echo "Finished.  Your pacman database has been optimized."
echo

exit 0