Import source: backend/src/middleware/errorHandler

Import the existing local project snapshot. This commit organizes existing files; it does not represent newly developed functionality.

backend/src/middleware/errorHandler.ts

@@ -0,0 +1,33 @@
+import type { ErrorRequestHandler } from 'express';
+import { ZodError } from 'zod';
+
+export class HttpError extends Error {
+  status: number;
+  code: string;
+
+  constructor(status: number, code: string, message: string) {
+    super(message);
+    this.status = status;
+    this.code = code;
+  }
+}
+
+export const notFoundHandler = () => {
+  throw new HttpError(404, 'NOT_FOUND', 'Not found');
+};
+
+export const errorHandler: ErrorRequestHandler = (err, _req, res, _next) => {
+  if (err instanceof ZodError) {
+    res.status(400).json({
+      error: 'Validation failed',
+      code: 'VALIDATION_ERROR',
+      details: err.flatten(),
+    });
+    return;
+  }
+
+  const status = err instanceof HttpError ? err.status : 500;
+  const code = err instanceof HttpError ? err.code : 'INTERNAL_ERROR';
+  const message = status === 500 ? 'Internal server error' : err.message;
+  res.status(status).json({ error: message, code });
+};