#!/bin/bash
########################################################################
# Author: Fred (support@qo-op.com) + @benoit
# Version: 0.4
# License: AGPL-3.0 (https://choosealicense.com/licenses/agpl-3.0/)
########################################################################
{ # Full reading before execution !
# echo '
# 
#     __  ___                                       _     ___ 
#    /  |/  /_  __   ____  ____ _____ ___  ___     (_)___/__ \
#   / /|_/ / / / /  / __ \/ __ `/ __ `__ \/ _ \   / / ___// _/
#  / /  / / /_/ /  / / / / /_/ / / / / / /  __/  / (__  )/_/  
# /_/  /_/\__, /  /_/ /_/\__,_/_/ /_/ /_/\___/  /_/____/(_)   
#        /____/                                               
# 
# ' | lolcat
MY_PATH="`dirname \"$0\"`"              # relative
MY_PATH="`( cd \"$MY_PATH\" && pwd )`"  # absolutized and normalized
ME="${0##*/}"

# check if -w is specified:
# Will look for the public IP of my gateway
# if my node is a Demilitarized Zone (DMZ)
WAN=$1

# GNU DEBIAN Core install extension
[[ ! $(which nslookup) ]] && sudo apt-get update && sudo apt-get install dnsutils -y

# What is myIP?
export myIP=$(hostname -I | awk '{print $1}' | head -n 1)
# Check if IP is from reserved LAN addresses
export isLAN=$(echo $myIP | grep -E "/(^127\.)|(^192\.168\.)|(^10\.)|(^172\.1[6-9]\.)|(^172\.2[0-9]\.)|(^172\.3[0-1]\.)|(^::1$)|(^[fF][cCdD])/")
# Find default route gateway
export myRouter=$(sudo route -n | grep ' UG ' | tail -n 1 | awk '{print $2}')

# Ask to the router my name (BOX DNS or system defined)
[[ $isLAN ]] && export NODENAME=$(sudo nslookup $myIP $myRouter -timeout=2 | grep 'name =' | awk -F ' = ' '{print $2}' | sed 's/\.$//') \
|| export NODENAME=$(sudo nslookup $myIP -timeout=2 | grep 'name =' | awk -F ' = ' '{print $2}' | sed 's/\.$//')

if [[ -z "$NODENAME" && "$WAN" == "-w" ]]; then
	IP=`wget --quiet http://brouits.free.fr/ip.php -O- | sed 's/\r//'`
	NODENAME=`nslookup $IP -timeout=2 | head -1 | cut -d'=' -f 2 | sed -E 's/^ *(.*)\.$/\1/'`
fi

# We must have that nodename, perhaps BOX DNS doesn't exist...
[[ $NODENAME == "" ]] && [[ $isLAN ]] && export NODENAME=$(sudo nslookup $myIP -timeout=2 | grep 'name =' | awk -F ' = ' '{print $2}' | sed 's/\.$//')
# OK no DNS is answering, let's be /etc/hostname
[[ $NODENAME == "" ]] && NODENAME=$(cat /etc/hostname)

NODENAME=$(echo "$NODENAME" | awk '{print tolower($1)}' | tail -n1)

[[ ! $(ping $NODENAME -c 1 2>/dev/null) ]] && NODENAME=$(echo $NODENAME | awk -F '.' '{ print $1 }') && NODENAME=$(echo "$NODENAME.local")
[[ ! $(ping $NODENAME -c 1 2>/dev/null) ]] && NODENAME="localhost"

# I can tell my name is (in lowercase)
echo "$NODENAME"

} # Full reading before execution !