const errorHandler = (err, req, res, next) => {
  console.error('Error occurred:', {
    message: err.message,
    stack: process.env.NODE_ENV === 'development' ? err.stack : undefined,
    path: req.path,
    method: req.method,
    timestamp: new Date().toISOString(),
  });

  if (err.name === 'ValidationError') {
    return res.status(400).json({
      error: 'Validation Error',
      message: err.message,
      details: err.details || {},
    });
  }

  if (err.name === 'SequelizeValidationError') {
    return res.status(400).json({
      error: 'Database Validation Error',
      message: 'Invalid data provided',
      details: err.errors?.map(e => ({ field: e.path, message: e.message })) || [],
    });
  }

  if (err.name === 'SequelizeUniqueConstraintError') {
    return res.status(409).json({
      error: 'Conflict',
      message: 'Resource already exists',
      details: err.errors?.map(e => ({ field: e.path, message: e.message })) || [],
    });
  }

  if (err.status || err.statusCode) {
    return res.status(err.status || err.statusCode).json({
      error: err.name || 'Error',
      message: err.message,
    });
  }

  if (err.code === 'OPENAI_API_ERROR') {
    return res.status(502).json({
      error: 'OpenAI Service Error',
      message: 'There was an issue communicating with OpenAI. Please try again.',
    });
  }

  res.status(500).json({
    error: 'Internal Server Error',
    message: process.env.NODE_ENV === 'development' ? err.message : 'Something went wrong!',
    ...(process.env.NODE_ENV === 'development' && { stack: err.stack }),
  });
};

module.exports = errorHandler;