{ config, lib, ... }: with lib; {
  options.constants = {
    domain = mkOption {
      type = types.str;
      default = "invariantspace.com";
      description = ''
        Store the default domain for all devices.
      '';
    };
    homeDir = mkOption {
      type = types.str;
      default = "/home/${config.constants.userName}";
      description = ''
        The default home directory for the default user.
      '';
    };
    localhost = mkOption {
      type = types.str;
      default = "127.0.0.1";
      description = ''
        Store the default localhost address.
      '';
    };
    postMaster = mkOption {
      type = types.str;
      default = "trivial@${config.constants.domain}";
      description = ''
        Store the default post master email address.
      '';
    };
    publicKeys = mkOption {
      type = types.listOf types.str;
      default = [
        "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHPT/zRq5fffcUmjxcwG2cTr09fOa9O4rBUb6ob2CyNy macronova@blitzar"
      ];
      description = ''
        The public keys for SSH authentication.
      '';
    };
    privateKeyFiles = mkOption {
      type = types.listOf types.str;
      default = if config.services.openssh.enable then builtins.map (key: key.path) config.services.openssh.hostKeys else [ "/root/.ssh/${config.networking.hostName}" ];
      description = ''
        The private key files for sops.
      '';
    };
    sopsFile = mkOption {
      type = types.path;
      default = ./secrets.yaml;
      description = ''
        The secrets file for device.
      '';
    };
    userName = mkOption {
      type = types.str;
      default = "macronova";
      description = ''
        The default username across all devices.
      '';
    };
  };
}