IBM i MCP Server

/** * @fileoverview Centralized error handler for the Hono HTTP transport. * This middleware intercepts errors that occur during request processing, * standardizes them using the application's ErrorHandler utility, and * formats them into a consistent JSON-RPC error response. * @module src/mcp-server/transports/httpErrorHandler */ import { Context } from "hono"; import { StatusCode } from "hono/utils/http-status"; import { JsonRpcErrorCode, McpError } from "../../../types-global/errors.js"; import { ErrorHandler, requestContextService } from "../../../utils/index.js"; import { logOperationStart } from "../../../utils/internal/logging-helpers.js"; import { HonoNodeBindings } from "./httpTypes.js"; function toHttpCode(errorCode: JsonRpcErrorCode): StatusCode { switch (errorCode) { case JsonRpcErrorCode.ParseError: case JsonRpcErrorCode.InvalidRequest: case JsonRpcErrorCode.InvalidParams: case JsonRpcErrorCode.ValidationError: return 400; case JsonRpcErrorCode.MethodNotFound: case JsonRpcErrorCode.NotFound: return 404; case JsonRpcErrorCode.Unauthorized: return 401; case JsonRpcErrorCode.Forbidden: return 403; case JsonRpcErrorCode.Conflict: return 409; case JsonRpcErrorCode.RateLimited: return 429; case JsonRpcErrorCode.Timeout: return 504; case JsonRpcErrorCode.ServiceUnavailable: return 503; default: return 500; } } /** * A centralized error handling middleware for Hono. * This function is registered with `app.onError()` and will catch any errors * thrown from preceding middleware or route handlers. * * @param err - The error that was thrown. * @param c - The Hono context object for the request. * @returns A Response object containing the formatted JSON-RPC error. */ export const httpErrorHandler = async ( err: Error, c: Context<{ Bindings: HonoNodeBindings; Variables: { requestId?: string | number | null }; }>, ): Promise<Response> => { const context = requestContextService.createRequestContext({ operation: "httpErrorHandler", path: c.req.path, method: c.req.method, }); logOperationStart(context, "HTTP error handler invoked."); const handledError = ErrorHandler.handleError(err, { operation: "httpTransport", context, }); const errorCode = handledError instanceof McpError ? handledError.code : JsonRpcErrorCode.InternalError; const status = toHttpCode(errorCode); logOperationStart(context, `Mapping error to HTTP status ${status}.`, { status, errorCode, }); // Retrieve the request ID from the Hono context let requestId: string | number | null = null; try { // Use c.get() which handles the retrieval safely requestId = c.get("requestId") ?? null; } catch (_e) { // Log if retrieval fails, though unlikely logOperationStart( context, "Could not retrieve requestId from Hono context in error handler.", ); } c.status(status); const errorResponse = { jsonrpc: "2.0", error: { code: errorCode, message: handledError.message, }, id: requestId, }; return c.json(errorResponse); };