#!/usr/bin/env bash
set -eu

DIR=$(cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd)
MAC_ADDRESS_FILE=${DIR}/tinc-macaddr
TINC_SUBNET_FILE=${DIR}/tinc-subnet

has() {
  command -v "$1" >/dev/null 2>&1
}

die() {
  echo $1 &>2
  exit 1
}

set_mac() {
  local interface=$1
  local mac_address=$2
  if has ifconfig; then
    ifconfig "$interface" down
    if [[ "$OSTYPE" == "linux-gnu" ]]; then
      ifconfig "$interface" hw ether "$mac_address"
    else
      ifconfig "$interface" ether "$mac_address"
    fi
    ifconfig "$interface" up
  elif has ip; then
    ip link set dev "$interface" down
    ip link set dev "$interface" address "$mac_address"
    ip link set dev "$interface" up
  else
    die "no suitable program found to configure the network interface, need iproute2 or ifconfig"
  fi
}

mask2cidr() {
  local netmask=$1
  local nbits=0
  IFS=.
  for dec in "$netmask"; do
    case $dec in
      255) let nbits+=8;;
      254) let nbits+=7;;
      252) let nbits+=6;;
      248) let nbits+=5;;
      240) let nbits+=4;;
      224) let nbits+=3;;
      192) let nbits+=2;;
      128) let nbits+=1;;
      0);;
      *) die "Error: $dec is not recognised"
    esac
  done
  echo "$nbits"
}

set_ip() {
  local interface=$1
  local ip=$2
  local netmask=$3
  if has ifconfig; then
    ifconfig "$interface" "$ip" netmask "$netmask"
  elif has ip; then
    ip addr add "$ip" dev "$interface"
  else
    die "no suitable program found to set ip address, need iproute2 or ifconfig"
  fi
}

start_dhclient() {
  local interface=$1
  if [[ "$OSTYPE" == "linux-gnu"  ]]; then
    dhclient -nw "$interface"
  elif [[ "$OSTYPE" == "freebsd"* ]]; then
    dhclient -b "$interface"
  else
    nohup setsid dhclient "$interface" >/dev/null 2>&1
  fi
}

start_dhcp() {
  local interface=$1
  if has dhcpcd; then
    dhcpcd -b -n "$interface"
  elif has dhclient; then
    start_dhclient "$interface"
  elif [[ "$OSTYPE" == "darwin"* ]]; then # TODO untested
    ipconfig set "$interface" DHCP
  else
    die "no suitable dhcp program found, need dhcpcd or dhclient"
  fi
}

[ -z "${INTERFACE:-}" ] && die "no INTERFACE environment variable set"

if [ ! -f "$MAC_ADDRESS_FILE" ]; then
  die "${MAC_ADDRESS_FILE} does not exists. Generate it with ./tinc-generate-mac"
fi

read -r MAC_ADDRESS <"$MAC_ADDRESS_FILE"
set_mac "$INTERFACE" "$MAC_ADDRESS"

if [ -e $TINC_SUBNET_FILE ]; then
  read -a SUBNET <"$TINC_SUBNET_FILE"
  IP=${SUBNET[0]}
  NETMASK=${SUBNET[1]}
  [ -z "$IP" ] && die "no ip set in '$TINC_SUBNET_FILE'"
  [ -z "$NETMASK" ] && die "no netmask set in '$TINC_SUBNET_FILE'"
  set_ip "$INTERFACE" "$IP" "$NETMASK"
else
  start_dhcp "$INTERFACE"
fi