#!/bin/bash

if [[ -z $1 ]]; then
  dns=$(gum choose --height 5 --header "Select DNS provider" Cloudflare DHCP Custom)
else
  dns=$1
fi

case "$dns" in
Cloudflare)
  sudo tee /etc/systemd/resolved.conf >/dev/null <<'EOF'
[Resolve]
DNS=1.1.1.1#cloudflare-dns.com 1.0.0.1#cloudflare-dns.com
FallbackDNS=9.9.9.9 149.112.112.112
DNSOverTLS=opportunistic
EOF
  
  # Ensure network interfaces don't override our DNS settings
  for file in /etc/systemd/network/*.network; do
    [[ -f "$file" ]] || continue
    if ! grep -q "^\[DHCPv4\]" "$file"; then continue; fi
    
    # Add UseDNS=no to DHCPv4 section if not present
    if ! sed -n '/^\[DHCPv4\]/,/^\[/p' "$file" | grep -q "^UseDNS="; then
      sudo sed -i '/^\[DHCPv4\]/a UseDNS=no' "$file"
    fi
    
    # Add UseDNS=no to IPv6AcceptRA section if present
    if grep -q "^\[IPv6AcceptRA\]" "$file" && ! sed -n '/^\[IPv6AcceptRA\]/,/^\[/p' "$file" | grep -q "^UseDNS="; then
      sudo sed -i '/^\[IPv6AcceptRA\]/a UseDNS=no' "$file"
    fi
  done
  
  sudo systemctl restart systemd-networkd systemd-resolved
  ;;

DHCP)
  sudo tee /etc/systemd/resolved.conf >/dev/null <<'EOF'
[Resolve]
DNS=
FallbackDNS=
DNSOverTLS=no
EOF
  
  # Allow network interfaces to use DHCP DNS
  for file in /etc/systemd/network/*.network; do
    [[ -f "$file" ]] || continue
    sudo sed -i '/^UseDNS=no/d' "$file"
  done
  
  sudo systemctl restart systemd-networkd systemd-resolved
  ;;

Custom)
  echo "Enter your DNS servers (space-separated, e.g. '192.168.1.1 1.1.1.1'):"
  read -r dns_servers

  if [[ -z "$dns_servers" ]]; then
    echo "Error: No DNS servers provided."
    exit 1
  fi

  sudo tee /etc/systemd/resolved.conf >/dev/null <<EOF
[Resolve]
DNS=$dns_servers
FallbackDNS=9.9.9.9 149.112.112.112
EOF
  
  # Ensure network interfaces don't override our DNS settings
  for file in /etc/systemd/network/*.network; do
    [[ -f "$file" ]] || continue
    if ! grep -q "^\[DHCPv4\]" "$file"; then continue; fi
    
    # Add UseDNS=no to DHCPv4 section if not present
    if ! sed -n '/^\[DHCPv4\]/,/^\[/p' "$file" | grep -q "^UseDNS="; then
      sudo sed -i '/^\[DHCPv4\]/a UseDNS=no' "$file"
    fi
    
    # Add UseDNS=no to IPv6AcceptRA section if present
    if grep -q "^\[IPv6AcceptRA\]" "$file" && ! sed -n '/^\[IPv6AcceptRA\]/,/^\[/p' "$file" | grep -q "^UseDNS="; then
      sudo sed -i '/^\[IPv6AcceptRA\]/a UseDNS=no' "$file"
    fi
  done
  
  sudo systemctl restart systemd-networkd systemd-resolved

  ;;
esac