#!/bin/sh
# -------
# File:        llxcfg-xorg-conf
# Description: LliureX simple xorg.conf setup tool
# Author:      Luis Garcia Gisbert <garcia_luigis@gva.es>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin St, Fifth Floor, Boston MA 02110-1301 USA
# --------

# vars
SECTION_REGEXP="/^Section[[:blank:]]\+\"Device\"/,/^EndSection/"
DRIVER_REGEXP="/[[:blank:]]\+Driver/"
GETDRIVER_REGEXP="$SECTION_REGEXP{$DRIVER_REGEXP{s%[^\"]*\"%%;s%\".*$%%;p}}"
XORG_CONF="/etc/X11/xorg.conf"
XORG_MOD="${XORG_CONF}.llxcfg"
XORG_BACK="${XORG_MOD}.BACKUP"
XORG_MD5="${XORG_BACK}.md5sum"

# funcs
get_driver(){
   CONF_FILE="$1"
   [ "$CONF_FILE" ] || CONF_FILE="$XORG_CONF"
   sed -ne "${GETDRIVER_REGEXP}" ${CONF_FILE}
}

show_current(){
   echo "Current driver: $(get_driver)"
}

show_backup(){
   if [ -r "$XORG_BACK" ] ; then
      echo "Backup configuration: $(get_driver "$XORG_BACK")"
   else
      echo "No backup configuration"
   fi
}

set_driver(){
   NEW_DRIVER="$1"
   NEW_CONF="${XORG_MOD}.${NEW_DRIVER}"
   if [ ! -r "$NEW_CONF" ] ; then
      SETDRIVER_REGEXP="$SECTION_REGEXP{$DRIVER_REGEXP{s%\".*\"%\"$NEW_DRIVER\"%}}"
      sed -e "${SETDRIVER_REGEXP}" ${XORG_CONF} > "$NEW_CONF"
   fi
   llxcfg-install "$NEW_CONF" "$XORG_CONF"
}

current_was_generated(){
   if [ -r "$XORG_BACK" -a -r "$XORG_MD5" ] && md5sum -c --status $XORG_MD5 ; then
      # the current xorg.conf was generated by this program
      return 0
   fi
   return 1
}

do_backup(){
   if ! test_backup > /dev/null ; then
      cp -a $XORG_CONF $XORG_BACK
   fi
   return 0
}
do_restore(){
   if [ -r "$XORG_BACK" ] ; then
      llxcfg-install $XORG_BACK $XORG_CONF
   else
      warn_msg "There is no backup file to restore"
   fi
   rm -f $XORG_BACK $XORG_MD5
}
do_md5sum(){
   md5sum $XORG_CONF > $XORG_MD5
   return 0
}

error_msg(){
   echo "$1" >&2
   exit 1
}

warn_msg(){
   echo "Warning: $1"
}

test_write(){
   [ -w "$XORG_CONF" ] || error_msg "Error: can't write to $XORG_CONF"
}

test_backup(){
   [ -r "$XORG_BACK" ] && return 0
   warn_msg "There is no backup file to restore"
   return 1
}

usage(){
   error_msg "Usage: $0 {set driver DRIVER|unset driver |restore driver |show driver |getcurrent driver }"
}

# main
[ -r "$XORG_CONF" ] || error_msg "Error: unreadable $XORG_CONF"

ACTION="$1"
[ "$ACTION" ] || usage

shift
SECTION="$1"
# only driver at this moment
[ "$SECTION" = "driver" ] || usage

case $ACTION in
   show)
      show_current
      show_backup
      ;;
   set)
      [ "$2" ] || usage
      test_write
      DRIVER="$2"
      OLD_DRIVER="$(get_driver)"
      [ "$DRIVER" = "$OLD_DRIVER" ] && return 0
      do_backup
      set_driver "$DRIVER"
      do_md5sum
      ;;
   unset)
      test_write
      if current_was_generated ; then
         do_restore
      elif test_backup ; then
         warn_msg "There are custom modifications in current config. Skipping restore"
      fi
      ;;
   restore)
      # unconditional restore
      test_write
      do_restore
      ;;
   getcurrent)
      get_driver
      ;;
esac
return 0