#!/bin/sh
function usage()
{
      echo "sdns -u[change to local domain]"
      echo "sdns [change to dnscrypt-proxy domain]"
      echo "sdns ip[manual dns server ip]"
      exit -1
}

function unblockresolv()
{
      sudo chattr -i /etc/resolv.conf
      sudo chmod 777 /etc/resolv.conf
}


function blockresolv()
{
      sudo chmod 444 /etc/resolv.conf
      sudo chattr +i /etc/resolv.conf
}


if [ $# == 0 ]; then
    unblockresolv
    sudo echo "nameserver 127.0.0.1" > /etc/resolv.conf
    blockresolv
    exit -1
elif [ $# == 1 ]; then
    dnsip=`echo $1|grep -x -E "([0-9]{1,3}\.){3}[0-9]{1,3}"`
    if [ $? == 0 ]; then
      unblockresolv
      sudo echo "nameserver $dnsip" > /etc/resolv.conf
      blockresolv
      exit -1
    elif [ "$1" == "-u" ]; then
      ip=`ifconfig|grep  -Eo  "([0-9]{1,3}\.){3}"|grep -v ^127|grep -v ^255|uniq`'1'
      unblockresolv
      sudo echo "nameserver $ip" > /etc/resolv.conf
      blockresolv
      exit -1
    else
      usage
    fi

else
    usage
fi