#!/bin/sh

SRC_DIR=nachos-4.0
MY_SRC=$SRC_DIR
PACKAGE=${SRC_DIR}.tar.Z
GROUPNAME=my_group
LAB=4

check_first() {
	if [ -e tmp ]
		then echo 'tmp' exits, refusing to overwrite
		exit 1
	fi
	if [ -f $PACKAGE ]
		then echo Found $PACKAGE
		else echo Could not find $PACKAGE
		exit 1
	fi
}

make_patch() {
	if [ "$1" != "" ]
		then PATCHFILE=$1
		else PATCHFILE=${GROUPNAME}.${LAB}.patch
	fi
	mkdir tmp
	echo UNPACKING SROUCE: $PACKAGE; sleep 1
	tar xzf $PACKAGE -C tmp
	mv tmp/$SRC_DIR tmp/${SRC_DIR}.orig
	cd tmp
	ln -s ../$MY_SRC $SRC_DIR
	echo MAKING PATCH: $PATCHFILE
	diff -Nur ${SRC_DIR}.orig $SRC_DIR > ../$PATCHFILE
	rm $SRC_DIR
	rm -rf ${SRC_DIR}.orig
	cd ..
	rmdir tmp
}

apply_patch() {
	if [ "$2" != "" ]
		then NEWDIR=$2
		else NEWDIR=${GROUPNAME}.${LAB}
	fi
	if [ -e $NEWDIR ]
		then echo refusing to overwrite \'$NEWDIR\'
		exit 1
	fi
	if [ "$1" != "" ]
		then PATCHFILE=$1
		else PATCHFILE=${GROUPNAME}.${LAB}.patch
	fi
	if [ -f $PATCHFILE ]
		then echo Found patch \'$PATCHFILE\'
		else echo Could not find \'$PATCHFILE\'
	fi
	mkdir tmp
	echo UNPACKING SROUCE: $PACKAGE; sleep 1
	tar xzf $PACKAGE -C tmp
	cd tmp
	echo applying \'$PATCHFILE\'
	patch -p0 <../$PATCHFILE
	mv $SRC_DIR ../$NEWDIR
	cd ..
	rmdir tmp
}

case "$1" in
'make')
	check_first
	make_patch $2;;
'apply')
	check_first
	apply_patch $2 $3;;
*)
	echo USAGE:"	"$0 make '[<patch_file>]'
	echo "	"$0 apply '[<patch_file>]'
	echo "	"$0 apply '[<patch_file> <new_directory>]'
esac