feat(core): hooks to the stdio transport layer

Author: MathurAditya724

examples/mcp-sdk/package.json

@@ -0,0 +1,20 @@
+{
+    "name": "example-mcp-sdk",
+    "version": "0.0.1",
+    "bin": "./dist/index.js",
+    "scripts": {
+        "dev": "tsx ./src/index.ts",
+        "build": "pkgroll --watch"
+    },
+    "dependencies": {
+        "@hono/node-server": "^1.13.8",
+        "@modelcontextprotocol/sdk": "^1.7.0",
+        "hono": "^4.7.4",
+        "muppet": "workspace:*"
+    },
+    "devDependencies": {
+        "pkgroll": "^2.11.2",
+        "tsx": "^4.19.3",
+        "typescript": "^5.8.2"
+    }
+}

examples/mcp-sdk/src/index.ts

@@ -0,0 +1,13 @@
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
+import { createMuppet } from "muppet";
+
+const transport = new StdioServerTransport();
+
+createMuppet({
+  name: "mcp-sdk",
+  version: "0.0.1",
+  transport,
+  logger: {
+    path: "/Users/adityamathur/dev/muppet-dev/muppet/examples/mcp-sdk/dist/main.log",
+  },
+}).then((muppet) => muppet.start());

examples/mcp-sdk/tsconfig.json

@@ -0,0 +1,30 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "lib": ["ESNext", "DOM"],
+    "moduleDetection": "force",
+    "useDefineForClassFields": false,
+    "experimentalDecorators": true,
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "resolveJsonModule": true,
+    "allowJs": true,
+    "strict": true,
+    "noFallthroughCasesInSwitch": true,
+    "noImplicitOverride": true,
+    "noImplicitReturns": true,
+    "noUnusedLocals": true,
+    "noImplicitAny": true,
+    "noUnusedParameters": true,
+    "declaration": false,
+    "noEmit": true,
+    "outDir": "dist/",
+    "sourceMap": true,
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "isolatedModules": true,
+    "verbatimModuleSyntax": true,
+    "skipLibCheck": true
+  },
+  "include": ["./src/**/*"]
+}

packages/core/package.json

@@ -1,5 +1,5 @@
 {
-  "name": "@muppet/validations",
+  "name": "muppet",
   "version": "0.1.0",
   "private": true,
   "type": "module",
@@ -10,7 +10,7 @@
     "dist"
   ],
   "scripts": {
-    "build": "pkgroll --minify"
+    "build": "pkgroll --watch"
   },
   "exports": {
     ".": {
@@ -24,8 +24,12 @@
       }
     }
   },
-  "peerDependencies": {},
+  "peerDependencies": {
+    "@modelcontextprotocol/sdk": "^1.7.0",
+    "pino": "^9.6.0"
+  },
   "devDependencies": {
+    "@standard-schema/spec": "^1.0.0",
     "pkgroll": "^2.5.1"
   }
 }

packages/core/src/createMuppet.ts

@@ -0,0 +1,52 @@
+import { ErrorCode } from "@modelcontextprotocol/sdk/types.js";
+import { messageHandler } from "./handlers";
+import type { MuppetConfig } from "./types";
+import pino from "pino";
+
+export function createMuppet(config: MuppetConfig) {
+  const { transport, logger: loggerConfig } = config;
+
+  const logger = pino(
+    loggerConfig ? pino.destination(loggerConfig.path) : { enabled: false },
+  );
+
+  transport.onclose = () => {
+    logger.info("Connection closed");
+  };
+
+  transport.onerror = (err) => {
+    logger.error({ err }, "Connection error");
+  };
+
+  transport.onmessage = async (message) => {
+    // biome-ignore lint/suspicious/noExplicitAny: <explanation>
+    let payload: any;
+
+    try {
+      const ctx = { logger };
+      payload = await messageHandler(ctx, message, config);
+    } catch (err) {
+      logger.error({ err }, "Error processing message");
+      payload = {
+        error: {
+          // @ts-expect-error
+          code: Number.isSafeInteger(err.code)
+            ? // @ts-expect-error
+              err.code
+            : ErrorCode.InternalError,
+          // @ts-expect-error
+          message: err.message ?? "Internal error",
+        },
+      };
+    }
+
+    transport.send({
+      jsonrpc: "2.0",
+      // @ts-expect-error
+      id: _request.id,
+      ...payload,
+    });
+  };
+
+  return transport;
+}

packages/core/src/handlers/index.ts

@@ -0,0 +1 @@
+export * from "./messageHandler";

packages/core/src/handlers/initializeHandler.ts

@@ -0,0 +1,31 @@
+import {
+  InitializeRequestSchema,
+  LATEST_PROTOCOL_VERSION,
+  SUPPORTED_PROTOCOL_VERSIONS,
+} from "@modelcontextprotocol/sdk/types.js";
+import type { HandlerFn } from "../types";
+
+export const initializeHandler: HandlerFn = (ctx, request, config) => {
+  ctx.logger.info({
+    msg: "Initializing mcp server",
+    request,
+  });
+
+  const validatedData = InitializeRequestSchema.parse(request);
+  const requestedVersion = validatedData.params.protocolVersion;
+
+  return {
+    result: {
+      protocolVersion: SUPPORTED_PROTOCOL_VERSIONS.includes(requestedVersion)
+        ? requestedVersion
+        : LATEST_PROTOCOL_VERSION,
+      serverInfo: {
+        name: config.name,
+        version: config.version,
+      },
+      capabilities: {
+        tools: {},
+      },
+    },
+  };
+};

packages/core/src/handlers/messageHandler.ts

@@ -0,0 +1,26 @@
+import {
+  RequestSchema,
+  type JSONRPCMessage,
+} from "@modelcontextprotocol/sdk/types.js";
+import type { HandlerFn } from "../types";
+import { initializeHandler } from "./initializeHandler";
+import { methodNotFoundHandler } from "./notFound";
+
+const handlersMap: Record<string, HandlerFn | undefined> = {
+  initialize: initializeHandler,
+};
+
+export const messageHandler: HandlerFn = async (ctx, request, config) => {
+  const _request = RequestSchema.parse(request);
+
+  const handler = handlersMap[_request.method] ?? methodNotFoundHandler;
+
+  const response = await handler(ctx, request, config);
+
+  ctx.logger.info({
+    msg: `Response for ${_request.method}`,
+    response,
+  });
+
+  return response;
+};

packages/core/src/handlers/notFound.ts

@@ -0,0 +1,16 @@
+import { ErrorCode } from "@modelcontextprotocol/sdk/types.js";
+import type { HandlerFn } from "../types";
+
+export const methodNotFoundHandler: HandlerFn = (ctx, request) => {
+  ctx.logger.error({
+    msg: "Method not found",
+    request,
+  });
+
+  return {
+    error: {
+      code: ErrorCode.MethodNotFound,
+      message: "Method not found",
+    },
+  };
+};

packages/core/src/index.ts

@@ -1,3 +1,2 @@
-export function defineConfig() {
-  return {};
-}
+export * from "./createMuppet";
+export * from "./types";