feat(brain): @mosaic/brain structured data service (#11)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

packages/brain/src/index.ts

@@ -0,0 +1,83 @@
+#!/usr/bin/env node
+
+import Fastify from 'fastify';
+import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
+import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
+import { JsonStore } from './storage/json-store.js';
+import { Collections } from './storage/collections.js';
+import { requireAuth } from './middleware/auth.js';
+import { registerRoutes } from './routes/api.js';
+import { registerMcpTools } from './mcp/tools.js';
+
+const HOST = process.env['HOST'] ?? '0.0.0.0';
+const PORT = Number(process.env['PORT'] ?? 8100);
+const DATA_DIR = process.env['MOSAIC_BRAIN_DATA_DIR'] ?? './data';
+
+/**
+ * Create a fresh MCP server instance with all tools registered.
+ * Each HTTP request gets its own instance to avoid state leaks.
+ */
+function createMcpServer(collections: Collections): McpServer {
+  const mcp = new McpServer({
+    name: 'mosaic-brain',
+    version: '0.1.0',
+  });
+  registerMcpTools(mcp, collections);
+  return mcp;
+}
+
+async function main(): Promise<void> {
+  // --- Storage ---
+  const store = new JsonStore({ dataDir: DATA_DIR });
+  await store.init();
+  const collections = new Collections(store);
+
+  // --- Fastify ---
+  const app = Fastify({ logger: true });
+
+  // Auth on all /v1 and /mcp routes
+  app.addHook('onRequest', async (req, reply) => {
+    if (req.url.startsWith('/v1/') || req.url === '/mcp') {
+      await requireAuth(req, reply);
+    }
+  });
+
+  // REST API
+  registerRoutes(app, collections);
+
+  // MCP over HTTP (Streamable HTTP transport)
+  // Each request gets a fresh McpServer + transport to avoid state leaks
+  app.all('/mcp', async (req, reply) => {
+    const mcp = createMcpServer(collections);
+    const transport = new StreamableHTTPServerTransport({
+      sessionIdGenerator: undefined, // stateless
+    });
+    await mcp.connect(transport);
+
+    if (req.method === 'POST') {
+      await transport.handleRequest(
+        req.raw,
+        reply.raw,
+        req.body as Record<string, unknown>,
+      );
+    } else if (req.method === 'GET') {
+      await transport.handleRequest(req.raw, reply.raw);
+    } else if (req.method === 'DELETE') {
+      await transport.handleRequest(req.raw, reply.raw);
+    } else {
+      reply.code(405).send({ error: 'Method not allowed' });
+    }
+  });
+
+  // --- Start ---
+  await app.listen({ host: HOST, port: PORT });
+  console.log(`mosaic-brain listening on ${HOST}:${PORT}`);
+  console.log(`  REST API: http://${HOST}:${PORT}/v1/`);
+  console.log(`  MCP:      http://${HOST}:${PORT}/mcp`);
+  console.log(`  Data dir: ${DATA_DIR}`);
+}
+
+main().catch((err) => {
+  console.error('Failed to start mosaic-brain:', err);
+  process.exit(1);
+});