allow changing minecraft data dir + allow opening firewall

nixos/modules/services/games/minecraft-server.nix

@@ -8,6 +8,7 @@ in
 {
   options = {
     services.minecraft-server = {
+
       enable = mkOption {
         type = types.bool;
         default = false;
@@ -15,7 +16,23 @@ in
           If enabled, start a Minecraft Server. The listening port for
           the server is always <literal>25565</literal>. The server
           data will be loaded from and saved to
-          <literal>/var/lib/minecraft</literal>.
+          <literal>${cfg.dataDir}</literal>.
+        '';
+      };
+
+      dataDir = mkOption {
+        type = types.path;
+        default = "/var/lib/minecraft";
+        description = ''
+          Directory to store minecraft database and other state/data files.
+        '';
+      };
+
+      openFirewall = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to open ports in the firewall (if enabled) for the server.
         '';
       };
 
@@ -30,7 +47,7 @@ in
   config = mkIf cfg.enable {
     users.extraUsers.minecraft = {
       description     = "Minecraft Server Service user";
-      home            = "/var/lib/minecraft";
+      home            = cfg.dataDir;
       createHome      = true;
       uid             = config.ids.uids.minecraft;
     };
@@ -43,9 +60,14 @@ in
       serviceConfig.Restart = "always";
       serviceConfig.User    = "minecraft";
       script = ''
-        cd /var/lib/minecraft
+        cd ${cfg.dataDir}
         exec ${pkgs.minecraft-server}/bin/minecraft-server ${cfg.jvmOpts}
       '';
     };
+
+    networking.firewall = mkIf cfg.openFirewall {
+      allowedUDPPorts = [ 25565 ];
+      allowedTCPPorts = [ 25565 ];
+    };
   };
 }