feat(nixos): add Valheim service module

configs/nixos/hosts/pikachu/default.nix

@@ -66,35 +66,13 @@
 
   registry.address.pikachu.self = "10.23.10.102";
 
-  modules.services.steamcmd = {
+  modules.services.games.valheim = {
     enable = true;
     steamDir = "/pikachu/data/steamcmd";
-    serviceName = "valheim";
-    appId = 896660;
     installDir = "/pikachu/data/servers/valheim/main";
     stateDir = "/pikachu/media/games/servers/valheim/main";
-    executable = "./valheim_server.x86_64";
-    arguments = [
-      "-nographics"
-      "-batchmode"
-      "-name"
-      "main"
-      "-port"
-      "2456"
-      "-world"
-      "main"
-      "-savedir"
-      config.modules.services.steamcmd.stateDir
-      "-password"
-      "foobarbaz"
-      "-public"
-      "0"
-    ];
-    udpPorts = [
-      2456
-      2457
-      2458
-    ];
+    serverName = "main";
+    password = "foobarbaz";
   };
 
   guests.actualbudget = {

configs/nixos/modules/services/games/valheim.nix

@@ -0,0 +1,81 @@
+{
+  config,
+  lib,
+  ...
+}:
+{
+  options.modules.services.games.valheim = {
+    enable = lib.mkEnableOption "Valheim dedicated server";
+
+    steamDir = lib.mkOption {
+      type = lib.types.str;
+      example = "/data/steamcmd";
+      description = "Directory where SteamCMD stores metadata and cache files.";
+    };
+
+    installDir = lib.mkOption {
+      type = lib.types.str;
+      example = "/data/servers/valheim/main";
+      description = "Directory where SteamCMD installs the Valheim server files.";
+    };
+
+    stateDir = lib.mkOption {
+      type = lib.types.str;
+      example = "/data/state/valheim/main";
+      description = "Directory where Valheim stores world data.";
+    };
+
+    serverName = lib.mkOption {
+      type = lib.types.str;
+      default = "valheim";
+      description = "Name shown for the Valheim server.";
+    };
+
+    port = lib.mkOption {
+      type = lib.types.port;
+      default = 2456;
+      description = "Base UDP port for the Valheim server.";
+    };
+
+    password = lib.mkOption {
+      type = lib.types.str;
+      description = "Valheim server password.";
+    };
+
+  };
+
+  config = lib.mkIf config.modules.services.games.valheim.enable (
+    let
+      service = config.modules.services.games.valheim;
+    in
+    {
+      modules.services.steamcmd = {
+        enable = true;
+        inherit (service) steamDir installDir stateDir;
+        serviceName = "valheim";
+        appId = 896660;
+        executable = "./valheim_server.x86_64";
+        arguments = [
+          "-nographics"
+          "-batchmode"
+          "-name"
+          service.serverName
+          "-port"
+          (toString service.port)
+          "-world"
+          service.serverName
+          "-savedir"
+          service.stateDir
+          "-password"
+          service.password
+          "-public"
+          "0"
+        ];
+        udpPorts = [
+          service.port
+          (service.port + 1)
+        ];
+      };
+    }
+  );
+}