yog-event 0.9.4

Yog event system — pub/sub for game/server events.
Documentation 
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//! Calling the bus from this binary: the one way it's reached is set once
//! (by `yog-api` in a mod, by the runtime in itself), and every action's
//! function and [`call`] go through it.

use yog_sync::OnceLock;

use crate::{Message, Service};

/// Sends `payload` to `address`'s provider: its reply's bytes, `None` when
/// no one answers.
pub type Caller = fn(address: crate::Address, payload: &[u8]) -> Option<Vec<u8>>;

static CALLER: OnceLock<Caller> = OnceLock::new();

/// How this binary reaches the bus; the first one set stays.
pub fn set_caller(caller: Caller) {
    let _ = CALLER.set(caller);
}

/// Asks `request`'s provider: its reply, `None` when no one answers (or the
/// bus isn't reached yet).
pub fn call<S: Service>(request: &S) -> Option<S::Reply> {
    let caller = CALLER.get()?;
    let reply = request.with_bytes(|payload| caller(request.address(), payload))?;
    S::Reply::from_bytes(&reply)
}