Playing around with syntax sugar around handling websocket messages

0.log

 INFO  otto_eventbus > Listening for WebSocket connections on 127.0.0.1:9311
 DEBUG tungstenite::handshake::server > Server handshake done.
 DEBUG otto_eventbus                  > Received: Ok(Text("{\"type\":\"ping\", \"value\" : {\"msg\":\"hi\"}}"))
 INFO  otto_eventbus                  > deser: Meow { ttype: "ping", value: Object({"msg": String("hi")}) }
 DEBUG otto_eventbus                  > Handling: Ping { msg: "hi" }
 DEBUG otto_eventbus                  > Received: Ok(Text("{\"type\":\"hello\",\"value\": null}"))
 INFO  otto_eventbus                  > deser: Meow { ttype: "hello", value: Null }
 DEBUG otto_eventbus                  > Handling hello: Hello

main.rs

/**
 * Meow is the primary message envolope
 */
#[derive(Debug, Deserialize, Serialize)]
struct Meow {
    #[serde(rename = "type")]
    ttype: String,
    value: serde_json::Value,
}

trait Handler: Send + Sync {
    /**
     * convert will take the given Value and attempt to convert it to the trait implementer's type
     *
     * If the conversion cannot be done properly, None will be returned
     */
    fn convert(v: serde_json::Value) -> Option<Self> where Self: std::marker::Sized + serde::de::DeserializeOwned {
        serde_json::from_value::<Self>(v).map_or(None, |res| Some(res))
    }
    /**
     * handle must be implemented by the trait implementer and should
     * do something novel with the value
     */
    fn handle(v: serde_json::Value) -> Result<(), std::io::Error>;
}


#[derive(Debug, Deserialize, Serialize)]
struct Ping {
    msg: String,
}
impl Handler for Ping {
    fn handle(v: serde_json::Value) -> Result<(), std::io::Error> {
        if let Some(ping) = Self::convert(v) {
            debug!("Handling: {:?}", ping);
        }
        Ok(())
    }
}

#[derive(Debug, Deserialize, Serialize)]
struct Hello;
impl Handler for Hello {
    fn handle(v: serde_json::Value) -> Result<(), std::io::Error> {
        if let Some(hello) = Self::convert(v) {
            debug!("Handling hello: {:?}", hello);
        }
        Ok(())
    }
}
lazy_static! {
    static ref REGISTRY: Mutex<HashMap<String, Dispatch>> = {
        let mut reg = HashMap::new();
        Mutex::new(reg)
    };
}
macro_rules! register_handler {
    ($($t:ty), * => $($e:expr), *) => {
        $(
            REGISTRY.lock().expect("Failed to unlock registry")
                .insert($e.to_string(), Dispatch::new(|v| { <$t>::handle(v); }));
        )*
    }
}

struct Dispatch {
    f: Box<dyn Fn(serde_json::Value) + Send + Sync>,
}
impl Dispatch {
    fn new<F>(f: F) -> Self
    where
        F: Fn(serde_json::Value) + 'static + Send + Sync,
    {
        Self { f: Box::new(f) }
    }
}

async fn handle_ws(mut c: Connection) -> Result<(), std::io::Error> {
    register_handler!(Ping => "ping");
    register_handler!(Hello => "hello");

    while let Some(item) = c.stream.next().await {
        debug!("Received: {:?}", item);
        match item {
            Ok(msg) => {
                if let Ok(meow) = serde_json::from_str::<Meow>(msg.to_text().unwrap()) {
                    info!("deser: {:?}", meow);

                    if let Ok(registry) = REGISTRY.lock() {
                        if let Some(container) = registry.get(&meow.ttype) {
                            (container.f)(meow.value);
                        }
                    }
                }
            },
            _ => {
            },
        }
    }
    Ok(())
}