implementing modules for system applications

system/modules/network/default.nix

@@ -0,0 +1,48 @@
+{
+  config,
+  lib,
+  ...
+}: let
+  inherit (lib) mkIf mkEnableOption mkOption types;
+  cfg = config.modules.network;
+in {
+  options = {
+    modules = {
+      network = {
+        enable = mkEnableOption "Enable the custom networking module";
+
+        hostName = mkOption {
+          type = types.str;
+          default = "default-hostname";
+          description = "Hostname for the system.";
+        };
+
+        interfaces = mkOption {
+          type = types.attrsOf (types.submodule {
+            options = {
+              allowedTCPPorts = mkOption {
+                type = types.listOf types.int;
+                default = [];
+                description = "List of allowed TCP ports for this interface.";
+              };
+            };
+          });
+          default = {};
+          description = "Network interface configurations.";
+        };
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    networking = {
+      networkmanager.enable = true;
+      inherit (cfg) hostName;
+      nftables.enable = true;
+      firewall = {
+        enable = true;
+        inherit (cfg) interfaces;
+      };
+    };
+  };
+}