Nesting resources

[abstract escarp]

Hey guys, I have several different variants of the same "resource", is it possible to nest these variants under the top-level resource directory?

e.g. say i have an "items" resource, with 2 variants "foo", "bar", could I have my project layout look something like: ```text
root/
src/
items/
foo/
foo.controller.ts
foo.service.ts
...
bar/
bar.controller.ts
bar.service.ts

and then in the top level "items" controller/module, just import those child variants?

[pallid crypt]

I'm a little confused by what you mean by "variants of the same 'resource'". At first glance this seems like a candidate for a module but I think this is an example where foo and bar just aren't going to cut it.

[abstract escarp]

So the use case is I have several 3rd party apis that I want to wrap, and it didn't seem to make sense to put them all into a single controller/service

ideally there would be a single controller/service/module at the top level (i.e. a resource), but from what I understand I need to add those all as dependencies in my root app.module?

didn't phrase that as well as I'd like

basically in the above example, "items" would be the "api" resource, and then inside that i would have subdirectories for each api

I don't really understand enough about how nest is structured to explain this clearly unfortunately

at the url level, you'd have something like /endpoints/{:api_id}/...

[pallid crypt]

If there's enough unique logic for the transactions back and forth between those APIs I'll often create modules which each have their own dedicated HttpModule configuration and related services that are exported and imported into the "main" app module. Something for example like:

modules/
┣ flight-data-enrichment/
┃ ┣ providers/
┃ ┃ ┗ services/
┃ ┃   ┣ flight-data-enrichment/
┃ ┃ ┃ ┃ ┣ flight-data-enrichment.service.spec.ts
┃ ┃ ┃ ┃ ┗ flight-data-enrichment.service.ts
┃ ┃   ┗ index.ts
┃ ┣ flight-data-enrichment.module.ts
┃ ┗ index.ts
┗ sam-communication/
  ┣ providers/
┃ ┃ ┗ services/
┃ ┃   ┣ sam-communication/
┃ ┃ ┃ ┃ ┣ sam-communication.service.spec.ts
┃ ┃ ┃ ┃ ┗ sam-communication.service.ts
┃ ┃   ┗ index.ts
  ┣ index.ts
  ┗ sam-communication.module.ts

[abstract escarp]

interesting... are the direct children of modules/ resources?

I haven't really internalized what modules, services, etc do yet

only generally that controllers reference services, which themselves return the data of interest

just to be clear, when i say "api" I mean 3rd party apis that I'm fetching data from

[pallid crypt]

In this particular case they're only services.

Controllers should simply direct traffic that's hitting a route, most logic should be handled by another provider, most often a service. (Traffic Controllers is a fun way to remember)

Modules are groupings of resources. These can be pipes, services, controllers, etc. One of the big benefits I find with modules is the ability to have contextual instances. So for example in the sam-communication module HttpModule is imported and has a configuration unique to hitting that API. Same for the flight-data-enrichment module. So when those services (that are defined as providers in their respective modules and exported) have their HttpService injected that service is configured for the endpoints that's relevant to them.

[pallid crypt]

yeah that's exactly what the flight-data-enrichment service is for: it hits an internal API to grab additional data which might not have come through from an AMQP message and merges the two data objects. The the sam-communication service sends transformed data to an external API. Both of them have different configuration requirements: Obviously different base URLs, different content-types, different authentication, and different accept values. Packaging them in modules gives me the flexibility to do that and not think about it much after it's all set.

[abstract escarp]

ah ok, yeah that sounds exactly like what I'm trying to do. I'm guessing your code isn't open source, but is there a repo that utilises a similar structure that I can look at, so I can better internalise what you're saying?

[pallid crypt]

This particular repo is not I'm sorry to say but let me see what I can find for you.

[abstract escarp]

That would be greatly appreciated, thanks for that

[pallid crypt]

While I'm looking, the basic Modules docs will make your life easier https://docs.nestjs.com/modules

[abstract escarp]

Thanks, taking a look

[pallid crypt]

example-nested-module.ts

import { HttpModule } from '@nestjs/axios';
import { Module } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import { ExampleCommunicationService } from '@example-integration/modules/xample-communication/providers/services';
import { ExampleHttpConfiguration } from '@example-integration/utils/config';

@Module({
    imports: [HttpModule.registerAsync({
        imports: [ConfigModule],
        useClass: ExampleHttpConfiguration
      }),
      ConfigModule
    ],
    providers: [ExampleCommunicationService],
    exports: [ExampleCommunicationService]
})
export class ExampleCommunicationModule {}

example-http-service-configuration.ts

import { HttpModuleOptions, HttpModuleOptionsFactory } from "@nestjs/axios";
import { Injectable } from "@nestjs/common";
import { ConfigService } from "@nestjs/config";
import { ExampleConfiguration } from "@example-integration/data";

@Injectable()
export class ExampleHttpConfiguration implements HttpModuleOptionsFactory {
    private readonly apiKey: string;
    private readonly baseUrl: string;
    private readonly contentType: string = 'application/xml';
    
    constructor(private readonly configService: ConfigService) {
        this.apiKey = this.configService.getOrThrow<string>(ExampleConfiguration.ApiKey);
        this.baseUrl = this.configService.getOrThrow<string>(ExampleConfiguration.Url);
    }

    createHttpOptions(): HttpModuleOptions|Promise<HttpModuleOptions> {
        return {
            baseURL: `https://${this.baseUrl}`,
            headers: {
                "Content-Type": this.contentType,
                "X-API-Key": this.apiKey,
                "Accept": this.contentType,
                "Host": this.baseUrl
            }
        }
    }
};

example-communication.service.ts

import { HttpService } from '@nestjs/axios';
import { Injectable } from '@nestjs/common';
import { firstValueFrom } from 'rxjs';
import { ExampleXMLDocument, ExampleResponse } from '@example-integration/data';

@Injectable()
export class ExampleCommunicationService {

    private readonly resourcePath: string = '/example';

    constructor(private readonly exampleHttpService: HttpService) {}

    public async sendXml(xmlRequestData: ExampleXMLDocument): Promise<ExampleResponse> {
        return await firstValueFrom(this.exampleHttpService.post(this.resourcePath, xmlRequestData));
    }
}

And then to use the ExampleCommunicationService in another part of the application we simply import the ExampleCommunicationModule into the appropriate module (since it's exported) in my case I'm importing it right into the root app.module.ts

[abstract escarp]

Awesome man, thanks for sharing that. It's so weird, for some reason my nest.js looks so foreign and difficult to understand. I've come mostly from mvc frameworks (e.g. phoenix), but the terminology that nest uses and how it separates logic is very different from what I'm used to

[pallid crypt]

lol don't ask why we have to explicitly set Host 🤣

[pallid crypt]

It's a lot like Spring Boot and even more like Angular lol. The module system is a very "Angular" thing (even though they're allowing you to move away from it) but it's also really nice once you get used to it.

[abstract escarp]

We'll now I have to, why do you explicitly set it? 😂

Ah ok, yeah never used spring boot before and my only angular experience is with version 1.x

(and I imagine it's changed a huge amount architecturally speaking since then)

[pallid crypt]

that's AngularJS, totally different from Angular lol

[abstract escarp]

oh well there you go lol

[pallid crypt]

it's a shared responsibility resource with a third party and for some reason they insist we directly set it 🤣

[pallid crypt]

FrontEndMasters has great Angular courses. Taking one (as silly as it sounds) would probably help a lot with understanding Nest a little better.

[abstract escarp]

lol I'd be curious as to what about their codebase makes that necessary

didn't Angular evolve from angular.js though?

[pallid crypt]

I don't think it actually is but I do know enough about their stack to say that their language of choice isn't very forgiving and a lot of work to adjust anything.

[abstract escarp]

php?

and I know of it Angular, never used it before though. I'd just assumed it was an attempt to rebrand angular js after people started hating on it

[pallid crypt]

lol nah it's very different; I learned AngularJS back in the day when it was the new hotness then jumped to React after a while until somewhere around Angular 4 then I was doing both; but there was a huge learning curve for sure - it's not really at all like AngularJS, they really scrapped everything down and restarted and came out with an entirely different framework (and honestly I'd say it's the only frontend framework that's truly a full-fledged framework as opposed to just a library with a large ecosystem)

ironic enough, I started working really heavily with Angular and got a job that wanted me to do some work on their legacy AngularJS and I just couldn't for the life of me get back into the groove with it 🤣 (well that and the fact that it was really poorly written, but to be fair it sounds like they whipped it up in like 4 days and founded their company on it)

[pallid crypt]

nah, I can't stand PHP but it's not that difficult to work with. I don't want to say because I'm not really even supposed to know, it's one of those ~things~. I'll just say that it's a low-level language that a fair amount of people sort of know but very very few are actually good at.