#!/bin/env bash

interface="";
server="dhcpd"
ip="10.5.5.11"
range="24"
interface_internet=""

# Todo : List interface ✓
#        Select first ✓
#        Select dhcpd or dnsmasq ✓
#        Select ip range ✓
#        Select ip ✓
#        Help ✓
#        Install from Makefile ✓
#        Add support for tethapp
#        dnsmasq config overwrite

# Default interface is the first non-wireless interfaces (sorted alpha-num)

function guess_nowifi {
    for i in `ls /sys/class/net/`; do
        if [ ! -d "/sys/class/net/$i/wireless" ] ; then 
            if [ "$interface" ] ; then 
                if [[ "$i" < "$înterface" ]] ; then
                    interface="$i"
                fi
            else
                interface="$i"
            fi
        fi
    done
}
function guess_internet {
    echo $(ip route show | grep 'default' |  \
                    sed 's/.*dev/dev/' | sed 's/scope//' | \
                    sed 's/src \([[:digit:]]\{1,3\}\.\)\{3\}[[:digit:]]\{1,3\}//g' | \
                    sed 's/link//' |
                    tr -s ' ' |
                    cut -d' ' -f 2)
}






if [ "$1" == "dns" ] ; then
    server="dnsmasq"
    shift
elif [ "$1" == "teth" ] ; then
  interface_internet=$(guess_internet)
  shift
elif [ "$1" == "teth_dns" ] ; then
  interface_internet=$(guess_internet)
  server="dnsmasq"
  shift
fi

if [ "$1" == "help" -o "$1" == "-h" -o "$1" == "--help" ] ; then
    echo 'Usage : autoDHCP [interface] [ip/range] [dns]'
    echo ''
    echo 'You also put the server type at the start of the command'
    echo 'Ex :'
    echo '> autoDHCP wlp3s0 10.5.5.11/24'
    echo '> autoDHCP eth0 192.168.0.1 dns'
    echo '> autoDHCP dns eth0 192.168.0.1/30'
fi



if [ "$1" ] ; then
    interface="$1"
    echo "Interface set to ${interface}"
fi

if [ "$2" ] ; then
    if [[ "$2" =~ .*/.* ]] ; then
        ip=$(echo $2 | cut -d'/' -f1)
        range="`echo $2 | cut -d'/' -f2 `"
        echo "Range set to ${range}"
    else
        ip="$2"
    fi
    echo "Ip set to ${ip}"
fi

if [ "$3" == "dns" ] ; then
    server="dnsmasq"
fi

IFS='.' read -r -a ipList <<< "$ip"
mask=$(( 4294967295 >> 32-${range} << 32-${range} ))
ipRaw=$(( ipList[0]*2**24 + ipList[1]*2**16 + ipList[2]*2**8 + ipList[3] ))
ipNetRaw=$(( ipRaw & mask ))

ipNet="$(( ipNetRaw >> 24 )).$(( ipNetRaw >> 16 & 255 )).$(( ipNetRaw >> 8 & 255)).$(( ipNetRaw & 255))"

if [ -z "$interface" ] ; then
  guess_nowifi
fi

sudo ip l set "$interface" up
sudo ip a r "${ip}/${range}" dev "$interface"
#sudo ip r a "${ip}/${range}" dev "$interface" src "${ip}"

if [ "$server" == "dhcpd" ] ; then
    sudo /usr/bin/dhcpd -4 -q -pf /run/dhcpd4.pid "$interface"
elif [ "$server" == "dnsmasq" ] ; then

    echo 'Configure dnsmasq'

    ip_start=$(echo "${ip}" | sed 's/\(\([0-9]\{1,3\}\.\)\{3\}\)[0-9]\{1,3\}/\1/')
    ip_start_tmp=$(echo "${ip}" | sed 's/\(\([0-9]\{1,3\}\.\)\{3\}\)//')
    ip_start_tmp=$((ip_start_tmp+1))

    dhcp_range=$(echo ${ip_start}{$ip_start_tmp\,,254}),12h
    echo "$dhcp_range"

    cat <<< $(
    echo "
        interface=${interface}
        listen-address=${ip}
        bind-interfaces
        dhcp-range=${dhcp_range}"
    ) > /tmp/dnsmasq.conf
    sudo dnsmasq --conf-file=/tmp/dnsmasq.conf

else
    echo "Server name ${server} unknow"
fi


if [ -n "$interface_internet" ] ; then
  echo "Routage des connections internet (${interface_internet} => ${interface})"
  sudo sysctl net.ipv4.ip_forward=1
  sudo iptables -t nat -A POSTROUTING -o "${interface_internet}" -j MASQUERADE
  sudo iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
  sudo iptables -A FORWARD -i "${interface}" -o "${interface_internet}" -j ACCEPT
fi


echo 'Should be ready ;)'