examples: add MCP Apps arcade server (#346)

examples/arcade-server/index.ts

@@ -0,0 +1,105 @@
+#!/usr/bin/env node
+
+/**
+ * Arcade MCP Server - Entry Point
+ *
+ * Sets up HTTP transport with Express and serves the modified emulation script.
+ */
+
+import cors from "cors";
+import express from "express";
+import type { Request, Response } from "express";
+import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
+import { createServer, validateGameId } from "./server.js";
+import {
+  getCachedEmulationScript,
+  processGameEmbed,
+} from "./game-processor.js";
+
+const DEFAULT_PORT = 3001;
+
+async function main() {
+  const port = parseInt(process.env.PORT ?? String(DEFAULT_PORT), 10);
+  const app = express();
+
+  app.use(cors());
+  app.use(express.json());
+
+  // Serve the modified emulation script (import() rewritten to loadScript()).
+  // <script src> is not subject to CORS, so this works from srcdoc iframes.
+  app.get("/scripts/emulation.js", (_req: Request, res: Response) => {
+    const script = getCachedEmulationScript();
+    if (!script) {
+      res.status(404).send("// No script cached. Load a game first.");
+      return;
+    }
+    res.setHeader("Content-Type", "application/javascript");
+    res.setHeader("Cache-Control", "no-cache");
+    res.send(script);
+  });
+
+  // Serve game HTML by ID. Fetches and processes the game from archive.org.
+  app.get("/game-html/:gameId", async (req: Request, res: Response) => {
+    const gameId = req.params.gameId as string;
+    if (!validateGameId(gameId)) {
+      res.status(400).send("Invalid game ID.");
+      return;
+    }
+    try {
+      const html = await processGameEmbed(gameId, port);
+      res.setHeader("Content-Type", "text/html");
+      res.setHeader("Cache-Control", "no-cache");
+      res.send(html);
+    } catch (error) {
+      console.error("Failed to load game:", gameId, error);
+      res.status(500).send("Failed to load game.");
+    }
+  });
+
+  // MCP endpoint - stateless transport (new server per request)
+  app.all("/mcp", async (req: Request, res: Response) => {
+    const server = createServer(port);
+    const transport = new StreamableHTTPServerTransport({
+      sessionIdGenerator: undefined,
+    });
+
+    res.on("close", () => {
+      transport.close().catch(() => {});
+      server.close().catch(() => {});
+    });
+
+    try {
+      await server.connect(transport);
+      await transport.handleRequest(req, res, req.body);
+    } catch (error) {
+      console.error("MCP error:", error);
+      if (!res.headersSent) {
+        res.status(500).json({
+          jsonrpc: "2.0",
+          error: { code: -32603, message: "Internal server error" },
+          id: null,
+        });
+      }
+    }
+  });
+
+  const httpServer = app.listen(port, () => {
+    console.log(`Arcade MCP Server listening on http://localhost:${port}/mcp`);
+  });
+  httpServer.setMaxListeners(20);
+
+  const shutdown = () => {
+    console.log("\nShutting down...");
+    httpServer.close(() => process.exit(0));
+    // Force exit after 2 seconds if connections don't close gracefully
+    setTimeout(() => process.exit(0), 2000).unref();
+  };
+
+  process.on("SIGINT", shutdown);
+  process.on("SIGTERM", shutdown);
+}
+
+main().catch((e) => {
+  console.error(e);
+  process.exit(1);
+});