#!/bin/bash
#Copyright 2004 William Stearns <wstearns@pobox.com>
#Released under the GPL
#V0.2

#Despite this app's best efforts, it's still a poster child for race
#conditions.  It really should only be run on a system in single user
#mode, or at least on files you _know_ won't be touched.

requireutil () {
	while [ -n "$1" ]; do
		if ! type -path "$1" >/dev/null 2>/dev/null ; then
			echo Missing utility "$1". Please install it. >&2
			return 1	#False, app is not available.
		fi
		shift
	done
	return 0	#True, app is there.
} #End of requireutil

TFile () {
	mktemp -q "$BaseFile.XXXXXX"
	if [ $? -ne 0 ]; then
		echo Unable to make temporary file, exiting. >&2
		exit 1
	fi
}

MaxTries=6

if [ $EUID -ne 0 ]; then
	requireutil sudo || exit 1
	SUDO=`which sudo`
fi

requireutil awk chmod chown dd df diff filefrag grep lsof ls mktemp mv rm sed seq touch || exit 1

BaseFile="$1"

if [ -z "$BaseFile" -o -n "$2" ]; then
	echo Usage:
	echo $0 File_to_defragment
	echo You can only specify a single file, and it must not be in use.
	exit 1
fi

if LsofOut="`lsof \"$BaseFile\" 2>&1`" ; then
	echo "$BaseFile is being held open:"
	echo "$LsofOut"
	echo 'Unable to continue on this file, exiting.'
	exit 1
fi
#echo 'File is currently closed, good, continuing.'

FileMegs=`ls -s --block-size=1048576 "$BaseFile" | awk '{print $1}'`
FreeSpace=`df -m "$BaseFile" | grep -v '^Filesystem' | awk '{print $4}'`

if [ $[ $FileMegs * $MaxTries + 20 ] -gt $FreeSpace ]; then
	echo "$BaseFile is ${FileMegs}M large, $FreeSpace free on that filesystem"
	echo "Making $MaxTries copies of $BaseFile would not leave 20M free.  Exiting."
	exit 1
fi

ExtentInfo=`$SUDO filefrag "$BaseFile" | sed -e 's/^.*: \([0-9]*\) extents* found, perfection would be \([0-9]*\) extents*$/\1 \2/' -e 's/^.*: \([0-9]*\) extents* found$/\1 \1/'`
CurrentExtents=${ExtentInfo%% *}
PerfectExtents=${ExtentInfo##* }

echo "Current $CurrentExtents Perfect $PerfectExtents"
if [ $CurrentExtents -eq $PerfectExtents ]; then
	echo "$BaseFile is at a perfect level, good.  Exiting."
	exit 0
elif [ $CurrentExtents -lt $PerfectExtents ]; then
	echo "Hmmm, $Basefile claimed to have fewer extents than perfection, something is wrong.  Exiting."
	exit 1
else
	echo "$BaseFile is fragmented, trying to defrag."

	BestPass=0
	BestExtents=$CurrentExtents
	declare -a Try TryExtents
	for Pass in `seq 1 $MaxTries` ; do
		Try[$Pass]=`TFile`
		dd if="$BaseFile" of="${Try[$Pass]}" 2>/dev/null

		TryExtents[$Pass]=`$SUDO filefrag ${Try[$Pass]} | sed -e 's/^.*: //' -e 's/ extent.*//'`
		echo -n "${TryExtents[$Pass]} "
		if [ ${TryExtents[$Pass]} -lt $BestExtents ]; then
			BestPass=$Pass
			BestExtents=${TryExtents[$Pass]}
		fi
	done
	echo

	#Remove all but the best
	for Pass in `seq 1 $MaxTries` ; do
		if [ $Pass -ne $BestPass ]; then
			rm -f "${Try[$Pass]}"
		fi
	done

	if [ $BestPass = 0 ]; then
		echo "Couldn't do better than the original file, exiting."
		rm -f "${Try[$BestPass]}"
		exit 0
	fi

	echo "Best pass was pass number $BestPass with ${TryExtents[$BestPass]} extents."

	touch --reference="$BaseFile" "${Try[$BestPass]}" || echo touch failed
	chmod --reference="$BaseFile" "${Try[$BestPass]}" || echo chmod failed
	chown --reference="$BaseFile" "${Try[$BestPass]}" || echo chown failed

	if ! diff -q "$BaseFile" "${Try[$BestPass]}" >/dev/null ; then
		echo "Warning - $BaseFile and ${Try[$BestPass]} differ, exiting"
		rm -f "${Try[$BestPass]}"
		exit 1
	fi

	if LsofOut="`lsof \"${Try[$BestPass]}\" 2>&1`" ; then
		echo "Someone opened ${Try[$BestPass]}:"
		echo "$LsofOut"
		echo 'Unable to continue on $BaseFile, exiting.'
		rm -f "${Try[$BestPass]}"
		exit 1
	fi
	if LsofOut="`lsof \"$BaseFile\" 2>&1`" ; then
		echo "Someone opened $BaseFile:"
		echo "$LsofOut"
		echo 'Unable to continue on this file, exiting.'
		rm -f "${Try[$BestPass]}"
		exit 1
	fi

#To completely replace the original
	echo "Succeeded, renaming ${Try[$BestPass]} to $BaseFile with no backup."
	rm "$BaseFile"
	mv "${Try[$BestPass]}" "$BaseFile"

#For manual replacement
	#echo "Succeeded, please rename ${Try[$BestPass]} to $BaseFile."

#To keep the original as a backup (untested)
	#echo "Succeeded, renaming ${Try[$BestPass]} to $BaseFile and keeping a backup of the original."
	#mv "$BaseFile" "`TFile`"
	#mv "${Try[$BestPass]}" "$BaseFile"
fi