main.rs

#[macro_use]
extern crate serde_derive;

extern crate serde;
extern crate warp;

use warp::Filter;

fn main() {
    // Match any request and return hello world!
    let routes = warp::any().and(warp::body::json()).map(handle_callback);

    warp::serve(routes).run(([127, 0, 0, 1], 3030));
}

#[derive(Debug, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
enum Callback {
    UrlVerification { token: String, challenge: String },
    EventCallback { token: String, event: Event },
}

#[derive(Debug, Deserialize)]
struct Event {
    channel: String,
    ts: String,
    #[serde(default)]
    thread_ts: Option<String>,
}

#[derive(Serialize)]
struct Challenge {
    challenge: String,
}

fn handle_callback(callback: Callback) -> impl warp::Reply {
    match callback {
        Callback::UrlVerification { challenge, .. } => return warp::reply::json(&Challenge { challenge }),
        // Callback::EventCallback { event, .. } if event.thread_ts.is_none() => {
        //     return warp::reply
        // },
        Callback::EventCallback {..} => return warp::reply(),
    }
}