inventory-barcode-system/middleware/errorHandler.js

const logger = require('../utils/logger');

/**
 * Error types and their corresponding HTTP status codes
 */
const ErrorTypes = {
  VALIDATION_ERROR: 'ValidationError',
  NOT_FOUND_ERROR: 'NotFoundError',
  CONFLICT_ERROR: 'ConflictError',
  UNAUTHORIZED_ERROR: 'UnauthorizedError',
  FORBIDDEN_ERROR: 'ForbiddenError',
  RATE_LIMIT_ERROR: 'RateLimitError',
  FILE_UPLOAD_ERROR: 'FileUploadError',
  DATABASE_ERROR: 'DatabaseError',
  EXTERNAL_SERVICE_ERROR: 'ExternalServiceError',
  BUSINESS_LOGIC_ERROR: 'BusinessLogicError'
};

/**
 * Custom error class for application-specific errors
 */
class AppError extends Error {
  constructor(message, type = 'ApplicationError', statusCode = 500, isOperational = true, details = null) {
    super(message);
    this.name = this.constructor.name;
    this.type = type;
    this.statusCode = statusCode;
    this.isOperational = isOperational;
    this.details = details;
    this.timestamp = new Date().toISOString();
    
    Error.captureStackTrace(this, this.constructor);
  }
}

/**
 * Create specific error types
 */
class ValidationError extends AppError {
  constructor(message, details = null) {
    super(message, ErrorTypes.VALIDATION_ERROR, 400, true, details);
  }
}

class NotFoundError extends AppError {
  constructor(message, details = null) {
    super(message, ErrorTypes.NOT_FOUND_ERROR, 404, true, details);
  }
}

class ConflictError extends AppError {
  constructor(message, details = null) {
    super(message, ErrorTypes.CONFLICT_ERROR, 409, true, details);
  }
}

class DatabaseError extends AppError {
  constructor(message, details = null) {
    super(message, ErrorTypes.DATABASE_ERROR, 500, true, details);
  }
}

class BusinessLogicError extends AppError {
  constructor(message, details = null) {
    super(message, ErrorTypes.BUSINESS_LOGIC_ERROR, 422, true, details);
  }
}

/**
 * Error response formatter
 */
const formatErrorResponse = (error, req) => {
  const isDevelopment = process.env.NODE_ENV !== 'production';
  
  const baseResponse = {
    success: false,
    error: error.type || 'InternalServerError',
    message: error.message || 'An unexpected error occurred',
    timestamp: error.timestamp || new Date().toISOString(),
    path: req.originalUrl,
    method: req.method
  };
  
  // Add details for operational errors
  if (error.isOperational && error.details) {
    baseResponse.details = error.details;
  }
  
  // Add stack trace in development
  if (isDevelopment && error.stack) {
    baseResponse.stack = error.stack;
  }
  
  // Add request ID if available
  if (req.requestId) {
    baseResponse.requestId = req.requestId;
  }
  
  return baseResponse;
};

/**
 * Determine if error should be retried
 */
const isRetryableError = (error) => {
  const retryableTypes = [
    ErrorTypes.DATABASE_ERROR,
    ErrorTypes.EXTERNAL_SERVICE_ERROR
  ];
  
  const retryableCodes = ['ECONNRESET', 'ETIMEDOUT', 'ENOTFOUND'];
  
  return retryableTypes.includes(error.type) || 
         retryableCodes.includes(error.code) ||
         (error.statusCode >= 500 && error.statusCode < 600);
};

/**
 * Get user-friendly error message
 */
const getUserFriendlyMessage = (error) => {
  const friendlyMessages = {
    [ErrorTypes.VALIDATION_ERROR]: 'The provided data is invalid. Please check your input and try again.',
    [ErrorTypes.NOT_FOUND_ERROR]: 'The requested resource could not be found.',
    [ErrorTypes.CONFLICT_ERROR]: 'This operation conflicts with existing data. Please check for duplicates.',
    [ErrorTypes.UNAUTHORIZED_ERROR]: 'Authentication is required to access this resource.',
    [ErrorTypes.FORBIDDEN_ERROR]: 'You do not have permission to perform this action.',
    [ErrorTypes.RATE_LIMIT_ERROR]: 'Too many requests. Please wait a moment before trying again.',
    [ErrorTypes.FILE_UPLOAD_ERROR]: 'There was a problem with the uploaded file. Please check the file format and size.',
    [ErrorTypes.DATABASE_ERROR]: 'A database error occurred. Please try again later.',
    [ErrorTypes.EXTERNAL_SERVICE_ERROR]: 'An external service is temporarily unavailable. Please try again later.',
    [ErrorTypes.BUSINESS_LOGIC_ERROR]: 'This operation cannot be completed due to business rules.'
  };
  
  return friendlyMessages[error.type] || error.message || 'An unexpected error occurred. Please try again later.';
};

/**
 * Main error handling middleware
 */
const errorHandler = (error, req, res, next) => {
  // Log the error with context
  const errorContext = {
    url: req.originalUrl,
    method: req.method,
    ip: req.ip,
    userAgent: req.get('User-Agent'),
    body: req.method !== 'GET' ? req.body : undefined,
    params: req.params,
    query: req.query,
    requestId: req.requestId
  };
  
  logger.logError(error, errorContext);
  
  // Handle specific error types
  let appError = error;
  
  // Convert known errors to AppError instances
  if (error.name === 'ValidationError') {
    appError = new ValidationError(error.message, error.details);
  } else if (error.name === 'CastError') {
    appError = new ValidationError('Invalid data format provided');
  } else if (error.code === 'SQLITE_CONSTRAINT_UNIQUE') {
    appError = new ConflictError('A record with this information already exists');
  } else if (error.code === 'SQLITE_CONSTRAINT') {
    appError = new ValidationError('Data constraint violation');
  } else if (error.code === 'ENOENT') {
    appError = new NotFoundError('Requested file or resource not found');
  } else if (error.code === 'LIMIT_FILE_SIZE') {
    appError = new ValidationError('File size exceeds the maximum allowed limit');
  } else if (error.code === 'LIMIT_UNEXPECTED_FILE') {
    appError = new ValidationError('Unexpected file upload');
  } else if (!error.isOperational) {
    // Convert unknown errors to generic AppError
    appError = new AppError(
      process.env.NODE_ENV === 'production' 
        ? 'An unexpected error occurred' 
        : error.message,
      'InternalServerError',
      500,
      false
    );
  }
  
  // Format response
  const errorResponse = formatErrorResponse(appError, req);
  
  // Override message with user-friendly version for production
  if (process.env.NODE_ENV === 'production') {
    errorResponse.message = getUserFriendlyMessage(appError);
  }
  
  // Add retry information for retryable errors
  if (isRetryableError(appError)) {
    errorResponse.retryable = true;
    errorResponse.retryAfter = 5; // seconds
  }
  
  // Send error response
  res.status(appError.statusCode || 500).json(errorResponse);
};

/**
 * 404 handler for unmatched routes
 */
const notFoundHandler = (req, res, next) => {
  const error = new NotFoundError(`Route ${req.method} ${req.originalUrl} not found`);
  next(error);
};

/**
 * Async error wrapper to catch async errors in route handlers
 */
const asyncHandler = (fn) => {
  return (req, res, next) => {
    Promise.resolve(fn(req, res, next)).catch(next);
  };
};

/**
 * Request timeout handler
 */
const timeoutHandler = (timeout = 30000) => {
  return (req, res, next) => {
    req.setTimeout(timeout, () => {
      const error = new AppError('Request timeout', 'TimeoutError', 408);
      next(error);
    });
    next();
  };
};

module.exports = {
  ErrorTypes,
  AppError,
  ValidationError,
  NotFoundError,
  ConflictError,
  DatabaseError,
  BusinessLogicError,
  errorHandler,
  notFoundHandler,
  asyncHandler,
  timeoutHandler,
  isRetryableError,
  getUserFriendlyMessage
};