#!/bin/bash
# Manipulate options in a .config file from the command line

usage() {
	cat >&2 <<EOL
Manipulate options in a .config file from the command line.
Usage:
config options command ...
commands:
	--enable|-e option   Enable option
	--disable|-d option  Disable option
	--module|-m option   Turn option into a module
	--set-str option value
	                     Set option to "value"
	--state|-s option    Print state of option (n,y,m,undef)

	--enable-after|-E beforeopt option
                             Enable option directly after other option
	--disable-after|-D beforeopt option
                             Disable option directly after other option
	--module-after|-M beforeopt option
                             Turn option into module directly after other option

	commands can be repeated multiple times

options:
	--file .config file to change (default .config)

config doesn't check the validity of the .config file. This is done at next
 make time.
EOL
	exit 1
}

checkarg() {
	ARG="$1"
	if [ "$ARG" = "" ] ; then
		usage
	fi
	case "$ARG" in
	CONFIG_*)
		ARG="${ARG/CONFIG_/}"
		;;
	esac
	ARG="`echo $ARG | tr a-z A-Z`"
}

set_var() {
	local name=$1 new=$2 before=$3

	name_re="^($name=|# $name is not set)"
	before_re="^($before=|# $before is not set)"
	if test -n "$before" && grep -Eq "$before_re" "$FN"; then
		sed -ri "/$before_re/a $new" "$FN"
	elif grep -Eq "$name_re" "$FN"; then
		sed -ri "s:$name_re.*:$new:" "$FN"
	else
		echo "$new" >>"$FN"
	fi
}

if [ "$1" = "--file" ]; then
	FN="$2"
	if [ "$FN" = "" ] ; then
		usage
	fi
	shift 2
else
	FN=.config
fi

if [ "$1" = "" ] ; then
	usage
fi

while [ "$1" != "" ] ; do
	CMD="$1"
	shift
	case "$CMD" in
	--refresh)
		;;
	--*-after)
		checkarg "$1"
		A=$ARG
		checkarg "$2"
		B=$ARG
		shift 2
		;;
	--*)
		checkarg "$1"
		shift
		;;
	esac
	case "$CMD" in
	--enable|-e)
		set_var "CONFIG_$ARG" "CONFIG_$ARG=y"
		;;

	--disable|-d)
		set_var "CONFIG_$ARG" "# CONFIG_$ARG is not set"
		;;

	--module|-m)
		set_var "CONFIG_$ARG" "CONFIG_$ARG=m"
		;;

	--set-str)
		set_var "CONFIG_$ARG" "CONFIG_$ARG=\"$1\""
		shift
		;;

	--state|-s)
		if grep -q "# CONFIG_$ARG is not set" $FN ; then
			echo n
		else
			V="$(grep "^CONFIG_$ARG=" $FN)"
			if [ $? != 0 ] ; then
				echo undef
			else
				V="${V/CONFIG_$ARG=/}"
				V="${V/\"/}"
				echo "$V"
			fi
		fi
		;;

	--enable-after|-E)
		set_var "CONFIG_$B" "CONFIG_$B=y" "CONFIG_$A"
		;;

	--disable-after|-D)
		set_var "CONFIG_$B" "# CONFIG_$B is not set" "CONFIG_$A"
		;;

	--module-after|-M)
		set_var "CONFIG_$B" "CONFIG_$B=m" "CONFIG_$A"
		;;

	# undocumented because it ignores --file (fixme)
	--refresh)
		yes "" | make oldconfig
		;;

	*)
		usage
		;;
	esac
done