Support compression

Hello I really love marblejs!! I want to use it on my project and also contribute it if I can. BTW is there a talk channel for marblejs? like spectrum, gitter, discord

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I wanna compress response(gzip) like express-compression. Middleware looks like only update req but not res

// effects.combiner.ts
export const combineMiddlewares = <T, U>
  (...effects: Effect<T, T, U>[]) =>
  (input$: Observable<T>, client: U, meta: EffectMetadata): Observable<T> =>
    effects.reduce((i$, effect) => effect(i$, client, meta!), input$);

So user can not add compress feature by add a compression middleware.

[JozefFlakus]

Thanks for kind words! There is already a Gitter channel for Marble.js but looks like nobody wants to talk ¯_(ツ)_/¯

For response compression, you can make use of output$ interceptor where you can attach a compression logic, which for example can be piped to the response.

This is only a dummy idea of how it can be implemented. More details you can find here.

const output$: HttpOutputEffect = res$ =>
  res$.pipe(
    // lets assume that res.body is a ReadableStream
    // and 'accept-encoding' is set to 'gzip'
    map(res =>  ({
      ...res,
      headers: { ...res.headers, 'Content-Encoding': 'gzip' },
      body: res.body.pipe(zlib.createGzip()),
    }),
  );

[JozefFlakus]

The idea for this improvement will look like this:

const output$: HttpOutputEffect = (res$, _, { initiator }) =>
  res$.pipe(
    // lets assume that res.body is a ReadableStream
    // and 'initiator.headers.accept-encoding' is set to 'gzip'
    map(res =>  ({
      ...res,
      headers: { ...res.headers, 'Content-Encoding': 'gzip' },
      body: res.body.pipe(zlib.createGzip()),
    }),
  );

So in general, output$ effect will have an ability to get an initiator which will contain a contextual object (eg. HttpRequest), so the developer will be able to grab all relevant information when needed from Effect metadata. The same pattern is used inside ErrorEffect where you can grab from meta the error object.