{ lib, ... }:
let
  inherit (lib) mkOption types;
  inherit (types) submodule;
in
{
  resources.network = {
    description = "Networking info.";
    policy =
      { config, ... }:
      {
        _class = "fediversity-resource-policy";
        options = {
          name = mkOption {
            description = ''
              The name of the machine. Most of the time, this will look like `vm02XXX`
              or `fediYYY`.
            '';
          };
          ipv4 = mkOption {
            type = submodule {
              options = {
                # enable = mkOption {
                #   default = true;
                # };

                interface = mkOption {
                  description = ''
                    The interface that carries the machine's IPv4 network.
                  '';
                  default = "eth0";
                };

                address = mkOption {
                  description = ''
                    The IP address of the machine, version 4. It will be injected as a
                    value in `networking.interfaces.eth0`, but it will also be used to
                    communicate with the machine via NixOps4.
                  '';
                };

                # prefixLength = mkOption {
                #   description = ''
                #     The subnet mask of the interface, specified as the number of bits in
                #     the prefix.
                #   '';
                #   default = 24;
                # };

                gateway = mkOption {
                  description = ''
                    The IP address of the default gateway.
                  '';
                  default = "185.206.232.1"; # FIXME: compute default from `address` and `prefixLength`.
                };
              };
            };
          };

          ipv6 = mkOption {
            type = submodule {
              options = {
                # enable = mkOption {
                #   default = true;
                # };

                interface = mkOption {
                  description = ''
                    The interface that carries the machine's IPv6 network.
                  '';
                  default = "eth0";
                };

                address = mkOption {
                  description = ''
                    The IP address of the machine, version 6. It will be injected as a
                    value in `networking.interfaces.eth0`, but it will also be used to
                    communicate with the machine via NixOps4.
                  '';
                };

                # prefixLength = mkOption {
                #   description = ''
                #     The subnet mask of the interface, specified as the number of bits in
                #     the prefix.
                #   '';
                #   default = 64;
                # };

                gateway = mkOption {
                  description = ''
                    The IP address of the default gateway.
                  '';
                  default = "2a00:51c0:12:1201::1"; # FIXME: compute default from `address` and `prefixLength`.
                };
              };
            };
          };
        };
        config = {
          resource-type = types.unspecified; # NixOS module
          apply =
            let
              cfg = config;
            in
            _requests:
            { config, ... }:
            {
              # imports = [
              #   ../../../../infra/common/nixos/networking.nix
              # ];
              networking = lib.mkMerge [
                {
                  hostName = cfg.name;
                }
                {
                  interfaces.${config.networking.defaultGateway.interface}.ipv4.addresses = [
                    {
                      prefixLength = 24;
                      address = cfg.ipv4.address;
                    }
                  ];
                  defaultGateway = {
                    address = cfg.ipv4.gateway;
                  };
                }
                {
                  interfaces.${config.networking.defaultGateway6.interface}.ipv6.addresses = [
                    {
                      prefixLength = 64;
                      address = cfg.ipv6.address;
                    }
                  ];
                  defaultGateway6 = {
                    address = cfg.ipv6.gateway;
                  };
                }
              ];
            };
        };
      };
  };
}