Add a way to intercept outgoing http requests

[smaznet]

I have a suggestion
Please add a way to middlewar outgoing requests

Something like this

bot.telegram.use(async (method,data,next)=>{
    let result = await next(method,data);
});

This is useful in some cases:

1. if you want save outgoing messages to database
2. modify some requests
3. if you want run some requests with delay
4. When you want send some requests which their flooding fast like sendContact
   You can limit requests

[wojpawlik]

Currently, this can be safely achieved by replacing ctx.telegram.callApi in every request (see https://github.com/KnightNiwrem/telegraf-throttler/blob/master/src/index.ts), but I agree that it'd be nice to have a proper API for it.

[smaznet]

Yes i know and I'm using this method

[wojpawlik]

This will be a significant internal change (I'd expect it to ship in 4.2 5.0).

We will need a proposal, so here's mine. To keep the discussion manageable, please post any concerns about my proposal as a reply to this, and any alternatives as a standalone comment, so it can be discussed separately.

---

ApiClient already contains a lot of complexity. Let's wrap it instead of adding more.

interface ApiClientInterface {
  callApi: <M extends keyof Telegram>(
    method: M,
    payload: Opts<M>,
    { signal, response }: ApiClient.CallApiOptions = {}
  ) => Promise<ReturnType<Telegram[M]>>
}

type Interceptor = (client: ApiClientInterface) => ApiClientInterface

ApiClient would ignore response, but an interceptor could use it to perform webhookReply.

It'd be great if some way to access response headers (Date to be specific ) was introduced.

Breaking: Telegram would need to accept and contain ApiClientInterface rather than accept token and inherit from ApiClient.

Breaking: that breaks Telegram::getFileLink, so it needs to be replaced with something. cc @AndrewLaneX

This decoupling would allow to write MockApiClient (#224).

bot.intercept(interceptor) would apply the interceptor to bot.telegram and all future ctx.telegrams.

[wojpawlik]

This only allows one interceptor, and adds complexity to ApiClient.

[smaznet]

Oh That's bad idea
Telegraf creates ApiClient on each incoming update and this code won't work

[wojpawlik]

why someone wants more interceptors?

I could imagine wanting to use telegraf-throttler and auto webhookReply alongside my bot-specific, custom interceptor.

[KnorpelSenf]

In case anyone is still interested in this, an alternative package that I created (called grammY) features exactly what this discussion is asking for.

https://grammy.dev

[wojpawlik]

#1704