IBM i MCP Server

/** * @fileoverview Hono middleware for handling MCP transport logic. * This middleware is responsible for adapting an incoming Hono request into a * standardized McpTransportRequest object and delegating all further processing * to the provided TransportManager. It no longer contains any session logic itself. * @module src/mcp-server/transports/http/mcpTransportMiddleware */ import { ErrorCode, McpError } from "@modelcontextprotocol/sdk/types.js"; import { MiddlewareHandler } from "hono"; import { createMiddleware } from "hono/factory"; import { requestContextService, withRequestContext, } from "../../../utils/index.js"; import { convertWebHeadersToNodeHeaders } from "../core/headerUtils.js"; // Import the utility import { McpTransportRequest } from "../core/transportRequest.js"; import { TransportManager, TransportResponse } from "../core/transportTypes.js"; import { HonoNodeBindings } from "./httpTypes.js"; type McpMiddlewareEnv = { Variables: { mcpResponse: TransportResponse; // Add requestId for use in the error handler requestId: string | number | null; }; }; export const mcpTransportMiddleware = ( transportManager: TransportManager, ): MiddlewareHandler<McpMiddlewareEnv & { Bindings: HonoNodeBindings }> => { return createMiddleware<McpMiddlewareEnv & { Bindings: HonoNodeBindings }>( async (c, next) => { const sessionId = c.req.header("mcp-session-id"); const context = requestContextService.createRequestContext({ operation: "mcpTransportMiddleware", sessionId, transport: "http", }); await withRequestContext(context, async () => { let body: unknown; let requestId: string | number | null = null; try { body = await c.req.json(); // Safely extract ID if (body && typeof body === "object" && "id" in body) { const id = (body as { id: unknown }).id; if ( typeof id === "string" || typeof id === "number" || id === null ) { requestId = id; } } } catch (_error) { // Ensure requestId is set even if parsing fails c.set("requestId", null); throw new McpError( ErrorCode.ParseError, "Failed to parse request body as JSON.", ); } c.set("requestId", requestId); // Store in context const transportRequest: McpTransportRequest = { // Use the centralized utility headers: convertWebHeadersToNodeHeaders(c.req.raw.headers), body, context, sessionId: sessionId || undefined, }; const response = await transportManager.handleRequest(transportRequest); c.set("mcpResponse", response); await next(); }); }, ); };