#!/bin/bash
  # Manipulate options in a .config file from the command line
  
  myname=${0##*/}
  
  # If no prefix forced, use the default CONFIG_
  CONFIG_="${CONFIG_-CONFIG_}"
  
  usage() {
  	cat >&2 <<EOL
  Manipulate options in a .config file from the command line.
  Usage:
  $myname options command ...
  commands:
  	--enable|-e option   Enable option
  	--disable|-d option  Disable option
  	--module|-m option   Turn option into a module
  	--set-str option string
  	                     Set option to "string"
  	--set-val option value
  	                     Set option to value
  	--undefine|-u option Undefine option
  	--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   .config file to change (default .config)
  	--keep-case|-k       Keep next symbols' case (dont' upper-case it)
  
  $myname doesn't check the validity of the .config file. This is done at next
  make time.
  
  By default, $myname will upper-case the given symbol. Use --keep-case to keep
  the case of all following symbols unchanged.
  
  $myname uses 'CONFIG_' as the default symbol prefix. Set the environment
  variable CONFIG_ to the prefix to use. Eg.: CONFIG_="FOO_" $myname ...
  EOL
  	exit 1
  }
  
  checkarg() {
  	ARG="$1"
  	if [ "$ARG" = "" ] ; then
  		usage
  	fi
  	case "$ARG" in
  	${CONFIG_}*)
  		ARG="${ARG/${CONFIG_}/}"
  		;;
  	esac
  	if [ "$MUNGE_CASE" = "yes" ] ; then
  		ARG="`echo $ARG | tr a-z A-Z`"
  	fi
  }
  
  txt_append() {
  	local anchor="$1"
  	local insert="$2"
  	local infile="$3"
  	local tmpfile="$infile.swp"
  
  	# sed append cmd: 'a\' + newline + text + newline
  	cmd="$(printf "a\\%b$insert" "
  ")"
  
  	sed -e "/$anchor/$cmd" "$infile" >"$tmpfile"
  	# replace original file with the edited one
  	mv "$tmpfile" "$infile"
  }
  
  txt_subst() {
  	local before="$1"
  	local after="$2"
  	local infile="$3"
  	local tmpfile="$infile.swp"
  
  	sed -e "s:$before:$after:" "$infile" >"$tmpfile"
  	# replace original file with the edited one
  	mv "$tmpfile" "$infile"
  }
  
  txt_delete() {
  	local text="$1"
  	local infile="$2"
  	local tmpfile="$infile.swp"
  
  	sed -e "/$text/d" "$infile" >"$tmpfile"
  	# replace original file with the edited one
  	mv "$tmpfile" "$infile"
  }
  
  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
  		txt_append "^$before=" "$new" "$FN"
  		txt_append "^# $before is not set" "$new" "$FN"
  	elif grep -Eq "$name_re" "$FN"; then
  		txt_subst "^$name=.*" "$new" "$FN"
  		txt_subst "^# $name is not set" "$new" "$FN"
  	else
  		echo "$new" >>"$FN"
  	fi
  }
  
  undef_var() {
  	local name=$1
  
  	txt_delete "^$name=" "$FN"
  	txt_delete "^# $name is not set" "$FN"
  }
  
  if [ "$1" = "--file" ]; then
  	FN="$2"
  	if [ "$FN" = "" ] ; then
  		usage
  	fi
  	shift 2
  else
  	FN=.config
  fi
  
  if [ "$1" = "" ] ; then
  	usage
  fi
  
  MUNGE_CASE=yes
  while [ "$1" != "" ] ; do
  	CMD="$1"
  	shift
  	case "$CMD" in
  	--keep-case|-k)
  		MUNGE_CASE=no
  		continue
  		;;
  	--refresh)
  		;;
  	--*-after|-E|-D|-M)
  		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)
  		# sed swallows one level of escaping, so we need double-escaping
  		set_var "${CONFIG_}$ARG" "${CONFIG_}$ARG=\"${1//\"/\\\\\"}\""
  		shift
  		;;
  
  	--set-val)
  		set_var "${CONFIG_}$ARG" "${CONFIG_}$ARG=$1"
  		shift
  		;;
  	--undefine|-u)
  		undef_var "${CONFIG_}$ARG"
  		;;
  
  	--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="${V/#\"/}"
  				V="${V/%\"/}"
  				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