#!/bin/bash
# Author: Bandie <bandie@chaospott.de>
# Copyright: Bandie, 2019, GNU-GPLv3

CONFIG="/etc/default/grub"
TMPCFG="grub_tmp"
CFGKEYS=(

  ## 'COMMENT'
  ## 'KEY'
  ## 'EXAMPLE_VALUE'

  'Name and mail address of owner'
  'OWNER'
  '"John Doe <john@doe.tld>"'
  
  'Amounts of seconds for how long the owner information is displayed. It is skippable via ESC. Default: 5'
  'OWNER_TIMEOUT'
  '5'
)


function testPerms(){
  if ! [ -e "$CONFIG" ]; then
    echo "$0: ERROR: $CONFIG does not exist!"
    exit 1
  fi
  if ! [ -w "$CONFIG" ]; then
    echo "$0: ERROR: Permission denied for file $CONFIG"
    exit 1
  fi
}


function append(){
  testPerms

  for ((i=0; i<${#CFGKEYS[@]}; i+=3)); do
    cat "$CONFIG" | grep "${CFGKEYS[(($i+1))]}" >> /dev/null
    if [ $? -ne 0 ]; then
      echo "Adding ${CFGKEYS[(($i+1))]} to $CONFIG..."
      echo "" >> $CONFIG
      echo "# ${CFGKEYS[$i]}" >> $CONFIG
      echo "#${CFGKEYS[(($i+1))]}=${CFGKEYS[(($i+2))]}" >> $CONFIG
    fi

  done
}

function remove(){
  testPerms
  
  for ((i=0; i<${#CFGKEYS[@]}; i+=3)); do
    echo "Removing ${CFGKEYS[(($i+1))]} from $CONFIG..."
    sed "$!N;/${CFGKEYS[$i]}/!P;D" "$CONFIG" | sed "/.*${CFGKEYS[(($i+1))]}=.*/d" > "$TMPCFG"
    cp "$TMPCFG" "$CONFIG"
  done
  rm $TMPCFG
}

function h(){
  echo "$0: Usage:"
  echo "$0 -i [ CONFIGFILE ] - Install config keys to config file. Configfile optional."
  echo "$0 -r [ CONFIGFILE ] - Remove config keys from config file. Configfile optional."
}

if [ -n "$2" ]; then
  CONFIG="$2"
fi

case $1 in
"-i")
  append
  ;;

"-r")
  remove
  ;;

*)
  h
esac