V2: Middleware

[tucnak]

How about we add some sort of middleware support. The perfect use case is spam handling and abuse mitigation, which is in its basic form is pretty much route-independent.

I doubt we should go with a fully-fledged approach that of Gin, for example, which utilizes route groups with attached middlewares. It seems to me a simple, bot-global middleware chain must be sufficient.

API:

// object :: (Message | Query | Callback)
bot.Use(func(b *Bot, object interface{}) bool {
    return true // return false - breaks the chain
})

[tucnak]

/cc @zoni

[tucnak]

I can't think of any other use case other than spam handling, which can now be managed via Poller interface, so I suggest middleware no more.

[tucnak]

So I thought about it for a while... and it actually seems worthwhile to implement some middleware system based on Pollers:

(like)

poller := &tb.LongPoller{25 * time.Second}
spamProtected := tb.Middleware(poller, func (upd *Update) bool {
    // return false to deny update
    return true
})

b, err := tb.NewBot(tb.Settings{
    Token: "TOKEN_HERE",
    Poller: spamProtected,
})