first commit

backend/middleware/errorHandler.js

@@ -0,0 +1,30 @@
+/**
+ * Error Handler Middleware
+ * Sanitizes errors before sending to client (security best practice)
+ */
+
+function errorHandler(err, req, res, _next) {
+  // Log full error internally (with stack trace)
+  console.error('[ERROR]', {
+    timestamp: new Date().toISOString(),
+    path: req.path,
+    method: req.method,
+    error: err.message,
+    code: err.code,
+    stack: process.env.NODE_ENV !== 'production' ? err.stack : undefined,
+  });
+
+  // Determine error type
+  const statusCode = err.statusCode || 500;
+  const isClientError = statusCode >= 400 && statusCode < 500;
+
+  // Send sanitized response to client
+  // IMPORTANT: Never expose internal error messages in production
+  res.status(statusCode).json({
+    success: false,
+    error: isClientError ? err.message : 'Internal server error',
+    code: err.code || 'INTERNAL_ERROR',
+  });
+}
+
+module.exports = { errorHandler };