{
  config,
  lib,
  pkgs,
  ...
}: let
  cfg = config.dns;
in {
  options.dns = {
    bind = {
      enable = lib.mkEnableOption "BIND DNS server";
      settings = {
        interfaces = lib.mkOption {
          type = lib.types.listOf lib.types.str;
          default = ["127.0.0.1"];
          description = "Network interfaces BIND should listen on (IPv4)";
        };

        interfaces6 = lib.mkOption {
          type = lib.types.listOf lib.types.str;
          default = ["::1"];
          description = "Network interfaces BIND should listen on (IPv6)";
        };

        zones = lib.mkOption {
          type = lib.types.listOf (lib.types.submodule {
            options = {
              name = lib.mkOption {
                type = lib.types.str;
                description = "Name of the DNS zone";
              };
              type = lib.mkOption {
                type = lib.types.enum ["master" "slave"];
                default = "master";
                description = "Type of DNS zone";
              };
              file = lib.mkOption {
                type = lib.types.str;
                default = "";
                description = "Path to zone file";
              };
            };
          });
          default = [];
          description = "DNS zones to configure";
        };

        extraConfig = lib.mkOption {
          type = lib.types.lines;
          default = "";
          description = "Additional BIND configuration options";
        };
      };
    };

    technitium = {
      enable = lib.mkEnableOption "Technitium DNS server";
      settings = {
        address = lib.mkOption {
          type = lib.types.str;
          default = "0.0.0.0";
          description = "IP address Technitium should listen on";
        };
        port = lib.mkOption {
          type = lib.types.port;
          default = 5380;
          description = "Port for Technitium DNS server";
        };
        extraOptions = lib.mkOption {
          type = lib.types.attrs;
          default = {};
          description = "Additional Technitium configuration options";
        };
      };
    };
  };

  config = lib.mkMerge [
    (lib.mkIf cfg.bind.enable {
      services.bind = {
        enable = true;
        listenOn = cfg.bind.settings.interfaces;
        listenOnIpv6 = cfg.bind.settings.interfaces6;
        zones =
          map (zone: {
            name = zone.name;
            type = zone.type;
            file = zone.file;
          })
          cfg.bind.settings.zones;
        extraConfig = cfg.bind.settings.extraConfig;
      };
      networking.firewall = {
        allowedTCPPorts = [53];
        allowedUDPPorts = [53];
      };
      environment.systemPackages = [pkgs.bind];
    })

    (lib.mkIf cfg.technitium.enable {
      services.technitium-dns-server = {
        enable = true;
        openFirewall = true;
        firewallTCPPorts = [53 5380 53443];
        firewallUDPPorts = [53];
      };
    })
  ];
}