#!/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" "\n")"

        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