function errorHandler(error, req, res, next) {
  console.error('Error occurred:', error);

  // Default error response
  let statusCode = 500;
  let message = 'Internal server error';
  let details = null;

  // Handle specific error types
  if (error.name === 'ValidationError') {
    statusCode = 400;
    message = 'Validation error';
    details = error.details || error.message;
  } else if (error.name === 'UnauthorizedError') {
    statusCode = 401;
    message = 'Unauthorized';
  } else if (error.name === 'SequelizeValidationError') {
    statusCode = 400;
    message = 'Database validation error';
    details = error.errors.map(err => ({
      field: err.path,
      message: err.message
    }));
  } else if (error.name === 'SequelizeUniqueConstraintError') {
    statusCode = 409;
    message = 'Resource already exists';
    details = error.errors.map(err => ({
      field: err.path,
      message: err.message
    }));
  } else if (error.name === 'SequelizeForeignKeyConstraintError') {
    statusCode = 400;
    message = 'Invalid reference';
  } else if (error.status) {
    statusCode = error.status;
    message = error.message;
  }

  // Send error response
  const response = {
    success: false,
    message,
    timestamp: new Date().toISOString()
  };

  // Include error details in development
  if (process.env.NODE_ENV === 'development') {
    response.error = details || error.message;
    response.stack = error.stack;
  } else if (details) {
    response.details = details;
  }

  res.status(statusCode).json(response);
}

module.exports = errorHandler;