refactor: Phase 2 - add error handling modules and response helpers

dashcaddy-api/error-handler.js

@@ -0,0 +1,85 @@
+// Error Handler Middleware
+// Centralizes error handling logic to eliminate duplicate catch blocks
+
+const { HTTP_STATUS } = require('./constants');
+
+/**
+ * Async route handler wrapper - catches errors and passes to error middleware
+ * Usage: app.get('/route', asyncHandler(async (req, res) => { ... }))
+ */
+function asyncHandler(fn) {
+  return (req, res, next) => {
+    Promise.resolve(fn(req, res, next)).catch(next);
+  };
+}
+
+/**
+ * Express error middleware - handles all errors consistently
+ */
+function errorMiddleware(err, req, res, next) {
+  const logger = req.app.get('logger');
+  
+  // Log the error with context
+  logger.error('Request error', {
+    error: err.message,
+    stack: err.stack,
+    path: req.path,
+    method: req.method,
+    ip: req.ip,
+    userId: req.user?.id
+  });
+  
+  // Determine status code
+  const statusCode = err.statusCode || err.status || HTTP_STATUS.INTERNAL_ERROR;
+  
+  // Send consistent error response
+  res.status(statusCode).json({
+    success: false,
+    error: err.message || 'Internal server error',
+    ...(process.env.NODE_ENV === 'development' && { stack: err.stack })
+  });
+}
+
+/**
+ * Custom error classes for specific scenarios
+ */
+class ValidationError extends Error {
+  constructor(message) {
+    super(message);
+    this.name = 'ValidationError';
+    this.statusCode = HTTP_STATUS.BAD_REQUEST;
+  }
+}
+
+class UnauthorizedError extends Error {
+  constructor(message = 'Unauthorized') {
+    super(message);
+    this.name = 'UnauthorizedError';
+    this.statusCode = HTTP_STATUS.UNAUTHORIZED;
+  }
+}
+
+class NotFoundError extends Error {
+  constructor(message = 'Not found') {
+    super(message);
+    this.name = 'NotFoundError';
+    this.statusCode = HTTP_STATUS.NOT_FOUND;
+  }
+}
+
+class ConflictError extends Error {
+  constructor(message) {
+    super(message);
+    this.name = 'ConflictError';
+    this.statusCode = HTTP_STATUS.CONFLICT;
+  }
+}
+
+module.exports = {
+  asyncHandler,
+  errorMiddleware,
+  ValidationError,
+  UnauthorizedError,
+  NotFoundError,
+  ConflictError
+};