feat: add entity handles and a bevy channel abstraction

Signed-off-by: Schmarni <marnistromer@gmail.com>

src/core/bevy_channel.rs

@@ -0,0 +1,32 @@
+use std::sync::OnceLock;
+
+use bevy::prelude::*;
+use tokio::sync::mpsc::{self, error::TryRecvError};
+
+#[derive(Resource)]
+pub struct BevyChannelReader<T: Send + Sync + 'static>(mpsc::UnboundedReceiver<T>);
+pub struct BevyChannel<T: Send + Sync + 'static>(OnceLock<mpsc::UnboundedSender<T>>);
+impl<T: Send + Sync + 'static> BevyChannel<T> {
+	pub const fn new() -> Self {
+		Self(OnceLock::new())
+	}
+	pub fn init(&self, app: &mut App) {
+		let (tx, rx) = mpsc::unbounded_channel();
+		self.0.set(tx).unwrap();
+		app.insert_resource(BevyChannelReader(rx));
+	}
+	pub fn send(&self, msg: T) -> Option<()> {
+		self.0.get()?.send(msg).ok()
+	}
+}
+
+impl<T: Send + Sync + 'static> BevyChannelReader<T> {
+	pub fn read(&mut self) -> Option<T> {
+		match self.0.try_recv() {
+			Ok(v) => Some(v),
+			Err(TryRecvError::Disconnected) => panic!("bevy channel should never disconnect"),
+			Err(TryRecvError::Empty) => None,
+		}
+	}
+}
+