{ lib, ... }:
with lib;
(evalModules {
  modules = [
    {
      options.configurations = mkOption {
        description = "My configurations.";
        type =
          with types;
          attrsOf (
            submodule (
              { name, ... }:
              {
                freeformType = attrs;
                options =
                  let
                    mkConfigurationTypeOption =
                      type:
                      mkOption {
                        description = "Whether the machine's functional type is a ${type} one.";
                        type = bool;
                        default = false;
                      };
                  in
                  {
                    hostname = mkOption {
                      description = "The machine's hostname.";
                      type = str;
                      default = name;
                      readOnly = true;
                    };

                    stateVersion = mkOption {
                      description = "Machine's Nixpkgs state version.";
                      type = str;
                      default = trivial.release;
                    };

                    deviceIcon = mkOption {
                      description = "Device icon to be used with nix-topology.";
                      type = nullOr (either path str);
                      default = null;
                    };

                    system = mkOption {
                      description = "The machine's system.";
                      type = nullOr (enum platforms.all);
                      default = null;
                    };

                    isHeadless = mkConfigurationTypeOption "headless";
                    isHeadful = mkConfigurationTypeOption "headful";
                    isOther = mkConfigurationTypeOption "other";

                    ipv4 = {
                      address = mkOption {
                        description = "The machine's public IPv4 address.";
                        type = nullOr str;
                        default = null;
                      };
                      prefixLength = mkOption {
                        description = "The machine's public IPv4 prefix length.";
                        type = nullOr int;
                        default = null;
                      };
                      gatewayAddress = mkOption {
                        description = "The machine's public IPv4 gateway address.";
                        type = nullOr str;
                        default = null;
                      };
                    };
                    ipv6 = {
                      address = mkOption {
                        description = "The machine's public IPv6 address.";
                        type = nullOr str;
                        default = null;
                      };
                      prefixLength = mkOption {
                        description = "The machine's public IPv6 prefix length.";
                        type = nullOr int;
                        default = null;
                      };
                      gatewayAddress = mkOption {
                        description = "The machine's public IPv6 gateway address.";
                        type = nullOr str;
                        default = null;
                      };
                    };

                    wireguard = {
                      ipv4.address = mkOption {
                        description = "The machine's internal IPv4 addresses.";
                        type = nullOr str;
                        default = null;
                      };
                      ipv6.address = mkOption {
                        description = "The machine's internal IPv6 addresses.";
                        type = nullOr str;
                        default = null;
                      };
                      publicKey = mkOption {
                        description = "The machine's public key.";
                        type = nullOr str;
                        default = null;
                      };
                    };

                    # TODO Automate filling of this from the NSD service module.
                    # Right now I need to copy domain definitions from there to here
                    # manually.
                    #
                    # Something like taking `config.services.nsd.zones[$domain]` and
                    # filtering for actual subdomains. We can remove this option
                    # altogether then.
                    domains = mkOption {
                      description = "External domains that resolve to this address.";
                      type = listOf str;
                      default = [ ];
                    };

                    syncthing.id = mkOption {
                      description = "Syncthing ID.";
                      type = nullOr str;
                      default = null;
                    };
                  };
              }
            )
          );

        default = { };
      };

      config = {
        _module.freeformType = types.attrs;

        fullname = "Firstname Lastname";
        username = "azahi";
        domain = {
          azahi = "azahi.cc";
          rohan = "rohan.net";
          gondor = "gondor.net";
          shire = "shire.net";
        };
        email = "frodo@${my.domain.gondor}";
        pgp = {
          key = "@PGP_KEY@";
          fingerprint = "@PGP_FINGERPRINT@";
          grip = "@PGP_GRIP@";
        };
        ssh = rec {
          type = "ed25519";
          id = my.email;
          key = "ssh-${type} @PUBLIC_KEY@ ${id}";
        };
        hashedPassword = "@HASHED_PASSWORD@";

        configurations = {
          # VPS in Germany.
          manwe = {
            stateVersion = "24.05";
            deviceIcon = "devices.cloud-server";
            system = "x86_64-linux";
            isHeadless = true;
            ipv4 = {
              gatewayAddress = "@IPV4_ADDRESS@";
              address = "@IPV4_ADDRESS@";
              prefixLength = 22;
            };
            ipv6 = {
              gatewayAddress = "@IPV6_ADDRESS@";
              address = "@IPV6_ADDRESS@]";
              prefixLength = 64;
            };
            wireguard = {
              ipv4.address = "10.69.0.1";
              ipv6.address = "fd69::0:1";
              publicKey = "@PUBLIC_KEY@";
            };
            domains = with my.domain; [
              "alertmanager.${shire}"
              "frodo.${rohan}"
              "frodo.${gondor}"
              "bitwarden.${shire}"
              "git.${azahi}"
              "git.${shire}"
              "grafana.${shire}"
              "irc.${shire}"
              "loki.${shire}"
              "ntfy.${shire}"
              "plausible.${shire}"
              "prometheus.${shire}"
              "radicale.${shire}"
              "rss-bridge.${shire}"
              "start.local"
              "uptime.${shire}"
              "vaultwarden.${shire}"
              azahi
              rohan
              gondor
              shire
            ];
          };

          # VPS in Germany.
          varda = {
            stateVersion = "24.05";
            deviceIcon = "devices.cloud-server";
            system = "x86_64-linux";
            isHeadless = true;
            ipv4 = {
              gatewayAddress = "@IPV4_ADDRESS@";
              address = "@IPV4_ADDRESS@";
              prefixLength = 22;
            };
            ipv6 = {
              gatewayAddress = "@IPV6_ADDRESS@";
              address = "@IPV6_ADDRESS@";
              prefixLength = 64;
            };
            wireguard = {
              ipv4.address = "10.69.1.1";
              ipv6.address = "fd69::1:1";
              publicKey = "@PUBLIC_KEY@";
            };
          };

          # VPS in France.
          yavanna = {
            stateVersion = "24.05";
            deviceIcon = "devices.cloud-server";
            system = "x86_64-linux";
            isHeadless = true;
            ipv4 = {
              gatewayAddress = "@IPV4_ADDRESS@";
              address = "@IPV4_ADDRESS@";
              prefixLength = 24;
            };
            ipv6 = {
              gatewayAddress = "@IPV6_ADDRESS@";
              address = "@IPV6_ADDRESS@";
              prefixLength = 128;
            };
            wireguard = {
              ipv4.address = "10.69.1.2";
              ipv6.address = "fd69::1:2";
              publicKey = "@PUBLIC_KEY@";
            };
            domains = with my.domain; [
              "flood.${shire}"
              "jackett.${shire}"
              "lidarr.${shire}"
            ];
            syncthing.id = "@SYNCTHING_ID@";
          };

          # VPS in Russia.
          tulkas = {
            stateVersion = "24.05";
            deviceIcon = "devices.cloud-server";
            system = "x86_64-linux";
            isHeadless = true;
            ipv4 = {
              gatewayAddress = "@IPV4_ADDRESS@";
              address = "@IPV4_ADDRESS@";
              prefixLength = 32;
            };
            ipv6 = {
              gatewayAddress = "@IPV6_ADDRESS@";
              address = "@IPV6_ADDRESS@";
              prefixLength = 64;
            };
            wireguard = {
              ipv4.address = "10.69.0.4";
              ipv6.address = "fd69::0:4";
              publicKey = "@PUBLIC_KEY@";
            };
          };

          # A beefy desktop: 7950x/rx6750xt/128GB.
          eonwe = {
            stateVersion = "24.05";
            deviceIcon = "devices.desktop";
            system = "x86_64-linux";
            isHeadful = true;
            wireguard = {
              ipv4.address = "10.69.3.1";
              ipv6.address = "fd69::3:1";
              publicKey = "@PUBLIC_KEY@";
            };
            syncthing.id = "@SYNCTHING_ID@";
          };

          # ThinkPad X1 Nano Gen 3.
          ilmare = {
            stateVersion = "24.05";
            deviceIcon = "devices.laptop";
            system = "x86_64-linux";
            isHeadful = true;
            wireguard = {
              ipv4.address = "10.69.4.1";
              ipv6.address = "fd69::4:1";
              publicKey = "@PUBLIC_KEY@";
            };
            syncthing.id = "@SYNCTHING_ID@";
          };

          # Google Pixel 7a w/ GrapheneOS.
          lungorthin = {
            isOther = true;
            wireguard = {
              ipv4.address = "10.69.5.2";
              ipv6.address = "fd69::5:2";
              publicKey = "@PUBLIC_KEY@";
            };
            syncthing.id = "@SYNCTHING_ID@";
          };
        };
      };
    }
  ];
}).config