Feat/add controller validation

[gabriellopes00]

I've working on controllers validation implementation, as proposed on issue #52. I created a validation module inside infra/http, that contains the validators which can be used by many controllers, once them purpose is general. For now, i'v only implemented the validators in RegisterUserController, so i created two validators. One is the most important for all controllers, is the RequiredFields validator, that receives an object with expected properties (request body expected data), and if any expected property comes with undefined or null value, it returns an error. The second is the CompareFields validator, which receives two fields, and compare if they're equal (in case of RegisterUserController it was used to compre password and password_confirmation).

So was created an interface

interface Validator<T = any> {
  validate(data: T): Either<Error, null>
}

All the validators must implement this interface, once the controllers now will depends of any class that implements it. But once the controller maybe needs more than one validator, i created a validator compositor, which receive others validators, and call the validate method of each of them. For example, in RegistrationUserController is needed to validate required fields in request body, and compare password with password_confirmation, so the validation compositor of RegisterUserController receives an RequiredFieldsValidator and a CompareFieldsValidator, and use this two validators to validate request body.

The validation compositor looks like this

class ValidatorCompositor<T = any> implements Validator<T> {
  constructor(private readonly validators: Validator<T>[]) {}

  validate(input: T): Either<Error, null> {
    for (const validator of this.validators) {
      const error = validator.validate(input)
      if (error !== null) return error
    }

    return null
  }
}

This way, if any of the validators received by the validation compositor returns an error, this error will be passed on to the controller, and finally an error 400 will be returned to the client.

I also created tests for each of the validators, and one more test in RegisterUserController, to verify if the controller actually returns 400 on validation fail.

What do you think ? @diego3g If you approve this implementation, then we can work on implementing the other controllers.

[diego3g]

@gabriellopes00 Thanks a lot for the contribution, I'm taking a deeper look into de implementation but I really think it's great!

[diego3g]

Don't you think we could use this validation logic in another places as the Kafka handlers? I think we can move it to outside of the http folder. I think we could put it inside the src/core

[gabriellopes00]

Don't you think we could use this validation logic in another places as the Kafka handlers? I think we can move it to outside of the http folder. I think we could put it inside the src/core

Sure, why not ? The main idea is creating a generic validation, and apply to components which requires one... maybe gRPC handlers, GraphQL resolvers... Kafka handlers would be a great use-case ! Once you have the expected handler data format, only inject the validator as a dependency in the handler, and use it to validate the messages (or any other data).

[gabriellopes00]

@diego3g Dude, i provided suggested changes on the validator method, changing the verification to:

if ( data[field] === null || data[field] === undefined || (typeof data[field] === 'string' && data[field].trim() === '')) {
        return left(new MissingParamError(field))
}

And i refactored the validation implementation inside RegisterUserController to pass the entire request to validator, and the final result is here:

  async handle(request: RegisterUserControllerRequest): Promise<HttpResponse> {
    try {
      const validationResult = this.validator.validate(request)

      if (validationResult.isLeft()) {
        return clientError(validationResult.value)
      }

      const { name, email, password } = request

      ...

What dou you think ?

[diego3g]

Hey @gabriellopes00, nice job!

So, let's move the generic validator files outside the http folder?

I think they should be at:

• src/core/validation/* (eg. src/core/validation/Validator.ts)

Besides that, you can go on and create the validators for all the controllers and Kafka handlers :)

[gabriellopes00]

Sure, i think we should move the validator interface only to src/core/validation/Validator.ts, and the implementations, we should put in src/infra/validation/*, this way we can share the implementation (if needed) between http controllers and Kafka handlers. Right ?

[diego3g]

I Agree.

[gabriellopes00]

Sure.

[gabriellopes00]

I refactored the code... now the validator interface is at src/core/infra/Validator.ts and the validators implementation are at src/infra/validation/*. So we won't have many problems to implement them in the Kafka handlers or in others components if needed.

[diego3g]

That's great! Will you create the rest of the validators for the other controllers as well? If not, i'm gonna merge this PR and we create them later.

[gabriellopes00]

Allright, in my opinion you can merge this PR for now. And as soon as i implement the rest of the validators in the others controllers, i'll open new PRs (as well as when applying validations to Kafka handlers). Thanks very much 👊