import { Injectable, NestMiddleware } from '@nestjs/common';
import { plainToInstance } from 'class-transformer';
import { validateOrReject, ValidationError } from 'class-validator';
import { Request, Response, NextFunction } from 'express';

/**
 * @name ValidationMiddleware
 * @description Allows use of decorator and non-decorator based validation
 * @param type dto
 * @param skipMissingProperties When skipping missing properties
 * @param whitelist Even if your object is an instance of a validation class it can contain additional properties that are not defined
 * @param forbidNonWhitelisted If you would rather to have an error thrown when any non-whitelisted properties are present
 */
@Injectable()
export class ValidationMiddleware implements NestMiddleware {
  use(req: Request, res: Response, next: NextFunction) {
    const { body } = req;
    const dto = plainToInstance(body.constructor, body); // type is inferred based on class

    validateOrReject(dto, { skipMissingProperties: true, whitelist: true, forbidNonWhitelisted: true })
      .then(() => {
        req.body = dto;
        next();
      })
      .catch((errors: ValidationError[]) => {
        const message = errors.map((error: ValidationError) => Object.values(error.constraints)).join(', ');
        next(new Error(message)); // You can create a custom exception filter if needed
      });
  }
}