nEngine/packages/mcp/test/server-namespace.test.ts

import { mkdtemp, mkdir, rm, writeFile } from "node:fs/promises";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { describe, expect, it } from "vitest";
import { createEngine } from "@nengine/core";
import { createEngineNamespaces, McpGateway } from "../src/index.js";

const TIME_YAML = [
  "id: default",
  "dayLengthTicks: 480",
  "seasons:",
  "  - { name: spring, dayCount: 28 }",
  "start: { day: 1, season: spring }",
  "",
].join("\n");

const FARM_YAML = [
  "id: farm",
  "width: 2",
  "height: 2",
  'tilesetRef: "tiles"',
  "spawn: { x: 0, y: 0 }",
  "layers:",
  "  - name: ground",
  "    data:",
  "      - [a, b]",
  "      - [b, a]",
  "",
].join("\n");

interface Setup {
  engine: ReturnType<typeof createEngine>;
  gateway: McpGateway;
  tmp: string;
  close: () => Promise<void>;
}

async function setup(): Promise<Setup> {
  const tmp = await mkdtemp(join(tmpdir(), "farm-server-ns-"));
  await mkdir(join(tmp, "maps"), { recursive: true });
  await writeFile(join(tmp, "time.yaml"), TIME_YAML);
  await writeFile(join(tmp, "maps", "farm.yaml"), FARM_YAML);

  const engine = createEngine({ contentDir: tmp });
  const gateway = new McpGateway();
  for (const namespace of createEngineNamespaces(engine, { gateway })) {
    gateway.register(namespace);
  }
  await engine.start();
  return {
    engine,
    gateway,
    tmp,
    close: async () => {
      await engine.stop();
      await rm(tmp, { recursive: true, force: true });
    },
  };
}

async function callText(gateway: McpGateway, name: string, args: Record<string, unknown> = {}): Promise<{
  ok: boolean;
  text: string;
}> {
  const result = await gateway.callTool(name, args);
  return { ok: result.isError !== true, text: result.content[0]?.text ?? "" };
}

describe("server namespace subsystem toggles", () => {
  it("enable_subsystem/disable_subsystem reject non-string and empty names", async () => {
    const { gateway, close } = await setup();
    try {
      const missing = await callText(gateway, "server.enable_subsystem", {});
      expect(missing.ok).toBe(false);
      expect(missing.text).toMatch(/missing required arguments: name/);

      const empty = await callText(gateway, "server.disable_subsystem", { name: "" });
      expect(empty.ok).toBe(false);
      expect(empty.text).toBe("server.disable_subsystem: name must be a non-empty string");

      const nonString = await callText(gateway, "server.enable_subsystem", { name: 42 });
      expect(nonString.ok).toBe(false);
      expect(nonString.text).toBe("server.enable_subsystem: name must be a non-empty string");
    } finally {
      await close();
    }
  });

  it("enable_subsystem/disable_subsystem reject unknown subsystems", async () => {
    const { gateway, close } = await setup();
    try {
      const enableUnknown = await callText(gateway, "server.enable_subsystem", { name: "nope" });
      expect(enableUnknown.ok).toBe(false);
      expect(enableUnknown.text).toBe("server.enable_subsystem: unknown subsystem: nope");

      const disableUnknown = await callText(gateway, "server.disable_subsystem", { name: "nope" });
      expect(disableUnknown.ok).toBe(false);
      expect(disableUnknown.text).toBe("server.disable_subsystem: unknown subsystem: nope");
    } finally {
      await close();
    }
  });

  it("disable removes a subsystem's tools/resources/prompts; enable restores them", async () => {
    const { gateway, close } = await setup();
    try {
      const allTools = gateway.listTools().map((tool) => tool.name);
      expect(allTools).toContain("time.get");
      expect(allTools).toContain("crop.create");
      expect(allTools).toContain("server.info");
      expect(gateway.listPrompts().map((prompt) => prompt.name)).toContain("crop.create-prompt");
      const allResources = gateway.listResources().map((resource) => resource.uri);
      expect(allResources).toContain("time://state");

      const disabled = await callText(gateway, "server.disable_subsystem", { name: "time" });
      expect(disabled.ok).toBe(true);
      expect(JSON.parse(disabled.text)).toEqual({ name: "time", enabled: false });

      const afterTools = gateway.listTools().map((tool) => tool.name);
      expect(afterTools).not.toContain("time.get");
      expect(afterTools).not.toContain("time.advance");
      expect(afterTools).toContain("server.info");
      expect(gateway.listResources().map((resource) => resource.uri)).not.toContain("time://state");

      const rejected = await callText(gateway, "time.get");
      expect(rejected.ok).toBe(false);
      expect(rejected.text).toMatch(/namespace "time" is disabled/);

      const info = await callText(gateway, "server.info");
      expect(info.ok).toBe(true);
      const subsystems = (JSON.parse(info.text) as { subsystems: { name: string; enabled: boolean }[] }).subsystems;
      expect(subsystems.find((s) => s.name === "time")).toEqual({ name: "time", enabled: false });
      expect(subsystems.find((s) => s.name === "server")).toEqual({ name: "server", enabled: true });

      const disabledCrop = await callText(gateway, "server.disable_subsystem", { name: "crop" });
      expect(disabledCrop.ok).toBe(true);
      expect(gateway.listPrompts().map((prompt) => prompt.name)).not.toContain("crop.create-prompt");

      const enabledCrop = await callText(gateway, "server.enable_subsystem", { name: "crop" });
      expect(enabledCrop.ok).toBe(true);
      expect(gateway.listPrompts().map((prompt) => prompt.name)).toContain("crop.create-prompt");

      const enabled = await callText(gateway, "server.enable_subsystem", { name: "time" });
      expect(enabled.ok).toBe(true);
      expect(JSON.parse(enabled.text)).toEqual({ name: "time", enabled: true });

      const restored = gateway.listTools().map((tool) => tool.name);
      expect(restored).toContain("time.get");
      const get = await callText(gateway, "time.get");
      expect(get.ok).toBe(true);
      expect(JSON.parse(get.text)).toEqual({ day: 1, season: "spring", tickInDay: 0 });
    } finally {
      await close();
    }
  });

  it("disable_subsystem rejects disabling the server namespace itself (guard rail)", async () => {
    const { gateway, close } = await setup();
    try {
      const guarded = await callText(gateway, "server.disable_subsystem", { name: "server" });
      expect(guarded.ok).toBe(false);
      expect(guarded.text).toBe("server.disable_subsystem: cannot disable the server subsystem");

      expect(gateway.listTools().map((tool) => tool.name)).toContain("server.info");
      const status = gateway.status().find((s) => s.name === "server");
      expect(status).toEqual({ name: "server", enabled: true });
    } finally {
      await close();
    }
  });

  it("enable/disable state is per-gateway in-memory and does not touch engine systems", async () => {
    const { engine, gateway, close } = await setup();
    try {
      await callText(gateway, "server.disable_subsystem", { name: "time" });
      const timeSystem = engine.systems.get("time");
      expect(timeSystem?.get()).toEqual({ day: 1, season: "spring", tickInDay: 0 });
      expect(gateway.status().find((s) => s.name === "time")).toEqual({ name: "time", enabled: false });
    } finally {
      await close();
    }
  });
});