#!/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