#!/bin/bash
# Info: Script to install Resolv packages
# Author: JesusPerezLorenzo
# Release: 1.0
# Date: 30-10-2023
USAGE="install-resolv.sh "

[ "$1" == "-h"  ] && echo "$USAGE"  && exit 1

_config_resolver() {
  [ -z "$NAMESERVERS" ]  && return
  local resolv_cfg_path
  local resolv_cfg_file
  if [ -d "/etc/resolvconf/resolv.conf.d" ] ; then
    resolv_cfg_path=/etc/resolvconf/resolv.conf.d
    resolv_cfg_file="head"
  else
    resolv_cfg_path=/etc
    resolv_cfg_file="resolv.conf"
     chattr -i "$resolv_cfg_path/$resolv_cfg_file"
  fi
  [ ! -r "$resolv_cfg_path/_$resolv_cfg_file" ] && sudo mv "$resolv_cfg_path/$resolv_cfg_file" "$resolv_cfg_path/_$resolv_cfg_file"
  grep -v "^nameserver" "$resolv_cfg_path/_$resolv_cfg_file" | sudo tee "$resolv_cfg_path/$resolv_cfg_file" &>/dev/null
  echo "
#options rotate
options timeout:1
" | sudo tee -a "$resolv_cfg_path/$resolv_cfg_file" &>/dev/null
  for ns in $NAMESERVERS
  do
    echo "nameserver $ns" | sudo tee -a "$resolv_cfg_path/$resolv_cfg_file" &>/dev/null
  done
  [ -n "$DOMAINS_SEARCH" ] && echo "search $DOMAINS_SEARCH" | sudo tee -a "$resolv_cfg_path/$resolv_cfg_file" &>/dev/null
  if [ -d "/etc/resolvconf/resolv.conf.d" ] ; then
     sudo timeout -k 10 20 systemctl restart resolvconf
  else
     chattr +i "$resolv_cfg_path/$resolv_cfg_file"
  fi
}

_config_split_dns() {
  [ -z "$SPLIT_DNS_SERVER" ] && return

  # Prefer systemd-resolved: true per-domain routing via routing domains.
  if systemctl cat systemd-resolved &>/dev/null; then
    local domains=""
    for d in $SPLIT_DNS_DOMAINS; do
      domains="$domains ~$d"
    done
    mkdir -p /etc/systemd/resolved.conf.d
    printf '[Resolve]\nDNS=%s\nDomains=%s\n' \
      "$SPLIT_DNS_SERVER" "${domains# }" \
      > /etc/systemd/resolved.conf.d/10-split-dns.conf

    local stub=/run/systemd/resolve/stub-resolv.conf
    local cur
    cur=$(readlink /etc/resolv.conf 2>/dev/null || echo "")
    if [ "$cur" != "$stub" ]; then
      chattr -i /etc/resolv.conf 2>/dev/null || true
      rm -f /etc/resolv.conf
      ln -sf "$stub" /etc/resolv.conf
    fi

    systemctl enable --now systemd-resolved
    systemctl daemon-reload
    systemctl restart systemd-resolved
    return
  fi

  # Fallback: prepend SPLIT_DNS_SERVER as primary nameserver.
  # coredns-vpn at SPLIT_DNS_SERVER forwards unknown zones to upstream.
  # Mirror the same path-selection logic as _config_resolver so resolvconf wins.
  if [ -d "/etc/resolvconf/resolv.conf.d" ]; then
    # resolvconf is managing /etc/resolv.conf.
    # Use 'head': its content is cat-ed verbatim into the output, bypassing the
    # 3-nameserver cap enforced on the 'base' file's entries.
    local head=/etc/resolvconf/resolv.conf.d/head
    if ! grep -q "^nameserver ${SPLIT_DNS_SERVER}$" "$head" 2>/dev/null; then
      local tmp
      tmp=$(mktemp)
      printf 'nameserver %s\n' "$SPLIT_DNS_SERVER" > "$tmp"
      grep "^nameserver" "$head" 2>/dev/null | grep -vF "$SPLIT_DNS_SERVER" >> "$tmp" || true
      grep -v "^nameserver" "$head" 2>/dev/null >> "$tmp" || true
      sudo mv "$tmp" "$head"
    fi
    resolvconf -u 2>/dev/null || sudo timeout -k 10 20 systemctl restart resolvconf
  else
    local resolv=/etc/resolv.conf
    chattr -i "$resolv" 2>/dev/null || true
    if ! grep -q "^nameserver ${SPLIT_DNS_SERVER}$" "$resolv" 2>/dev/null; then
      local tmp
      tmp=$(mktemp)
      printf 'nameserver %s\n' "$SPLIT_DNS_SERVER" > "$tmp"
      grep "^nameserver" "$resolv" 2>/dev/null | grep -vF "$SPLIT_DNS_SERVER" >> "$tmp" || true
      grep -v "^nameserver" "$resolv" 2>/dev/null >> "$tmp" || true
      sudo mv "$tmp" "$resolv"
    fi
    chattr +i "$resolv" 2>/dev/null || true
  fi
}

[ -r "./env-resolv"  ] && . ./env-resolv

case "${1:-install}" in
  install|update|reinstall|restart)
    _config_resolver
    _config_split_dns
    ;;
  resolver)
    _config_resolver
    ;;
  split-dns)
    _config_split_dns
    ;;
esac
exit 0