/**
 * Error Handler Middleware
 * Xử lý tất cả errors trong ứng dụng
 */

class AppError extends Error {
  constructor(message, statusCode = 500, isOperational = true) {
    super(message);
    this.statusCode = statusCode;
    this.isOperational = isOperational;
    this.status = `${statusCode}`.startsWith('4') ? 'fail' : 'error';
    
    Error.captureStackTrace(this, this.constructor);
  }
}

/**
 * Handle Sequelize Validation Errors
 */
const handleSequelizeValidationError = (err) => {
  const errors = err.errors.map(e => ({
    field: e.path,
    message: e.message,
  }));
  
  return new AppError(
    'Validation Error',
    400,
    true,
    errors
  );
};

/**
 * Handle Sequelize Unique Constraint Error
 */
const handleSequelizeUniqueError = (err) => {
  const field = err.errors[0]?.path || 'field';
  const message = `${field} already exists`;
  
  return new AppError(message, 409);
};

/**
 * Handle Sequelize Foreign Key Error
 */
const handleSequelizeForeignKeyError = (err) => {
  return new AppError('Referenced record not found', 404);
};

/**
 * Development Error Response
 */
const sendErrorDev = (err, res) => {
  res.status(err.statusCode).json({
    success: false,
    status: err.status,
    error: err,
    message: err.message,
    stack: err.stack,
  });
};

/**
 * Production Error Response
 */
const sendErrorProd = (err, res) => {
  // Operational, trusted error: send message to client
  if (err.isOperational) {
    res.status(err.statusCode).json({
      success: false,
      status: err.status,
      message: err.message,
      errors: err.errors,
    });
  } 
  // Programming or unknown error: don't leak error details
  else {
    console.error('❌ ERROR:', err);
    
    res.status(500).json({
      success: false,
      status: 'error',
      message: 'Something went wrong!',
    });
  }
};

/**
 * Global Error Handler Middleware
 */
const errorHandler = (err, req, res, next) => {
  err.statusCode = err.statusCode || 500;
  err.status = err.status || 'error';
  
  if (process.env.NODE_ENV === 'development') {
    sendErrorDev(err, res);
  } else {
    let error = { ...err };
    error.message = err.message;
    
    // Handle specific Sequelize errors
    if (err.name === 'SequelizeValidationError') {
      error = handleSequelizeValidationError(err);
    }
    
    if (err.name === 'SequelizeUniqueConstraintError') {
      error = handleSequelizeUniqueError(err);
    }
    
    if (err.name === 'SequelizeForeignKeyConstraintError') {
      error = handleSequelizeForeignKeyError(err);
    }
    
    sendErrorProd(error, res);
  }
};

/**
 * 404 Handler
 */
const notFoundHandler = (req, res, next) => {
  const err = new AppError(
    `Cannot find ${req.originalUrl} on this server`,
    404
  );
  next(err);
};

/**
 * Async Error Wrapper
 */
const catchAsync = (fn) => {
  return (req, res, next) => {
    fn(req, res, next).catch(next);
  };
};

module.exports = {
  AppError,
  errorHandler,
  notFoundHandler,
  catchAsync,
};