#!/bin/bash

is_nat_set() {
  local gateway_interface=${1}
  iptables -w -nvt nat -L POSTROUTING | grep MASQUERADE | grep -q "${gateway_interface}"
}

unset_nat() {
  local gateway_interface=${1}
  echo "[INFO] hotspot ${wifi_device}: Unset NAT on ${gateway_interface}"
  iptables -w -t nat -D POSTROUTING -o "${gateway_interface}" -j MASQUERADE
}

set_nat() {
  local gateway_interface=${1}
  echo "[INFO] hotspot ${wifi_device}: Set NAT on ${gateway_interface}"
  iptables -w -t nat -A POSTROUTING -o "${gateway_interface}" -j MASQUERADE
}

has_ip6delegatedprefix() {
  [[ -n "${ip6_net}" ]] && [[ "${ip6_net}" != "none" ]]
}

is_ip6addr_set() {
  ip address show dev "${wifi_device}" 2>/dev/null | grep -q "${ip6_addr}/64"
}

unset_ip6addr() {
  echo "[INFO] hotspot ${wifi_device}: Unset IPv6 address ${ip6_addr}"
  ip address delete "${ip6_addr}/64" dev "${wifi_device}"
}

ynh_hotspot_state=$(systemctl is-active __SERVICE_NAME__)
if [[ "${ynh_hotspot_state}" == "active" || "${ynh_hotspot_state}" == "activating" ]]; then
  old_gateway_interface=${dev}
  new_gateway_interface=$(ip route | awk '/default via/ { print $5; }')
  
  ip6_net=$(yunohost app setting __APP__ ip6_net)
  ip6_addr="${ip6_net}1"

  wifi_device=$(yunohost app setting __APP__ wifi_device)

  if is_nat_set "${old_gateway_interface}"; then
    unset_nat "${old_gateway_interface}"
  fi

  if [[ -n "$new_gateway_interface" ]] && ! is_nat_set $new_gateway_interface; then
    set_nat "${new_gateway_interface}"
  fi

  if has_ip6delegatedprefix && is_ip6addr_set; then
    unset_ip6addr
  fi

  yunohost app setting __APP__ gateway_interface --value "${new_gateway_interface}"
fi