nixos/hickory-dns: combine Hint and Forward zone types into one

        '';

      };

      zone_type = mkOption {

        type = types.enum [ "Primary" "Secondary" "Hint" "Forward" ];

        type = types.enum [ "Primary" "Secondary" "External" ];

        default = "Primary";

        description = ''

          One of:

          - "Primary" (the master, authority for the zone).

          - "Secondary" (the slave, replicated from the primary).

          - "Hint" (a cached zone with recursive resolver abilities).

          - "Forward" (a cached zone where all requests are forwarded to another resolver).

          - "External" (a cached zone that queries other nameservers).

          For more details about these zone types, consult the documentation for BIND,

          though note that hickory-dns supports only a subset of BIND's zone types:

        '';

      };

      file = mkOption {

        type = types.either types.path types.str;

        default = "${config.zone}.zone";

        defaultText = literalExpression ''"''${config.zone}.zone"'';

        type = types.nullOr (types.either types.path types.str);

        default = if config.zone_type != "External" then "${config.zone}.zone" else null;

        defaultText = literalExpression ''if config.zone_type != "External" then "''${config.zone}.zone" else null'';

        description = ''

          Path to the .zone file.

          If not fully-qualified, this path will be interpreted relative to the `directory` option.

          If omitted, defaults to the value of the `zone` option suffixed with ".zone".

          If omitted, defaults to the value of the `zone` option suffixed with ".zone" when `zone_type` isn't External; otherwise, defaults to `null`.

        '';

      };

    };

      configFile = mkOption {

        type = types.path;

        default = toml.generate "hickory-dns.toml" (

          lib.filterAttrsRecursive (_: v: v != null) cfg.settings

          lib.mapAttrs (_: v: if builtins.isList v then map (v: if builtins.isAttrs v then lib.filterAttrs (_: v: v != null) v else v) v else v) (lib.filterAttrsRecursive (_: v: v != null) cfg.settings)

        );

        defaultText = lib.literalExpression ''

          let toml = pkgs.formats.toml { }; in toml.generate "hickory-dns.toml" cfg.settings