Add ionos-dyndns module for the NixOS config

nix/modules/ionos-dyndns.nix

@@ -0,0 +1,118 @@
+{ config, lib, pkgs, ... }:
+with lib;
+let
+  cfg = config.services.ionos-dyndns;
+  ionos-dyndns = pkgs.callPackage ../packages/ionos-dyndns.nix {};
+
+  command = lib.concatStringsSep " " (
+    [
+      "${ionos-dyndns}/bin/ionos-dyndns"
+      "--api-prefix"
+      "$(cat ${cfg.apiPrefixPath})"
+      "--api-secret"
+      "$(cat ${cfg.apiSecretPath})"
+      "--fqdn"
+      cfg.fqdn
+      "--interface"
+      cfg.interface
+    ]
+    ++ lib.optionals cfg.a [ "--A" ]
+    ++ lib.optionals cfg.aaaa [ "--AAAA" ]
+  );
+in {
+  options = {
+    services.ionos-dyndns = {
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to turn on the IONOS DynDNS timer.
+        '';
+      };
+      user = mkOption {
+        type = types.str;
+        default = "ionos-dyndns";
+      };
+      apiPrefixPath = mkOption {
+        type = types.path;
+        description = ''
+          Path of a file holding the API prefix.
+        '';
+      };
+      apiSecretPath = mkOption {
+        type = types.path;
+        description = ''
+          Path of a file holding the API secret.
+        '';
+      };
+      a = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to set the A record (IPv4).
+        '';
+      };
+      aaaa = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to set the AAAA record (IPv6).
+        '';
+      };
+      fqdn = mkOption {
+        type = types.str;
+        description = ''
+          Fully qualified domain name for this host.
+        '';
+      };
+      interface = mkOption {
+        type = types.str;
+        description = ''
+          Interface to get the IP address from.
+        '';
+      };
+      interval = mkOption {
+        type = types.str;
+        default = "14m";
+        description = "How often to run the update script in systemd.timers notation.";
+      };
+      serviceName = mkOption {
+        type = types.str;
+        default = "ionos-dyndns";
+      };
+    };
+  };
+  config = mkIf cfg.enable {
+    users = {
+      users = {
+        ${cfg.user} = {
+          isSystemUser = true;
+          group = cfg.user;
+          description = "IONOS DynDNS user.";
+        };
+      };
+      groups = {
+        ${cfg.user} = {
+        };
+      };
+    };
+    systemd = {
+      services.${cfg.serviceName} = {
+        serviceConfig = {
+          Type = "oneshot";
+          User = cfg.user;
+          # We assume that command doesn't contain any single quotes
+          ExecStart = "${pkgs.bash}/bin/bash -c '${command}'";
+        };
+      };
+      timers.${cfg.serviceName} = {
+        wantedBy = [ "timers.target" ];
+        timerConfig = {
+          Unit = "${cfg.serviceName}.service";
+          OnBootSec = "30s";
+          OnActiveSec = cfg.interval;
+        };
+      };
+    };
+  };
+}